Yellow Rose
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Then what would you do to occupy those extra few thousand brain cells? 
Teach you how to paint your hood.
Teach you how to paint your hood.
BBSC New SS Box Thread
- Thread starter kpond
- Start date
The hood now resides somewhere in southern Cali. The new one is BLACK!!!!
Hey Andy,
I'm in Paris currently, it's 1AM in the morning and I am preparing a customer engagement for tomorrow - but I do read at least the FI part of Prime!
What precisely were the changes between you 383HP run and your 340+HP run? As I understand you did change your fuel map but did you also not change your timing map? I guess I'm wondering if you switched SS boxes in between the results? If so, what timing valuse did you use from the old box to the new? Same, or some multiplication?
Your belt slipping should be detectable by overlaying the graphs. If a belt slip (lower boost) you HP curves should be nearly identical up to about 6psi - I'm guessing that is around 6500 rpm.
I have the same overall rich condition you do. I have decided how I'm going to fix it too! (seriously). My thinking is if I'm rich now but have overall good curves, then I just need to add a little boost to consume that extra fuel!
Where can I source a couple of smaller (Novi 1000) pulleys. Is that something I have to get from MB or can I buy on-line somewhere?
I'm in Paris currently, it's 1AM in the morning and I am preparing a customer engagement for tomorrow - but I do read at least the FI part of Prime!
What precisely were the changes between you 383HP run and your 340+HP run? As I understand you did change your fuel map but did you also not change your timing map? I guess I'm wondering if you switched SS boxes in between the results? If so, what timing valuse did you use from the old box to the new? Same, or some multiplication?
Your belt slipping should be detectable by overlaying the graphs. If a belt slip (lower boost) you HP curves should be nearly identical up to about 6psi - I'm guessing that is around 6500 rpm.
I have the same overall rich condition you do. I have decided how I'm going to fix it too! (seriously). My thinking is if I'm rich now but have overall good curves, then I just need to add a little boost to consume that extra fuel!
Where can I source a couple of smaller (Novi 1000) pulleys. Is that something I have to get from MB or can I buy on-line somewhere?
Yellow Rose
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I'm in Paris currently.
Boy, could somebody have fun with that one!
Sorry, could not resist. Actually, are you still with the same French company employer (and that is a serious question, company name begins with "D")?
What precisely were the changes between your 383 HP run and your 340+ HP run?
Only two things - I leaned out the fuel map and on the day that I re-dyno'ed, I changed the supercharger belt. No other changes.
As I understand you did change your fuel map but did you also not change your timing map?
Changed fuel map, did not change timing map, except...............
I guess I'm wondering if you switched SS boxes in between the results?
Yes, new SS box installed back in December.
If so, what timing values did you use from the old box to the new? Same, or some multiplication?
...............I took the "same" values; however, per MB's instruction multiplied them by exactly 2x, cell-for-cell, in the new box.
Your belt slipping should be detectable by overlaying the graphs. If a belt slip (lower boost) your HP curves should be nearly identical up to about 6 PSI - I'm guessing that is around 6500 RPM.
Respectfully, not necessarily. If a belt is slipping, the HP across the RPM band will be reduced by x-amount because boost is lessened by y-amount. Upon closer examination of the before-n-after HP curves, this is very evident. The shape of the two curves is virtually identical; however, one is "just below" the other.
Where can I source a couple of smaller (Novi 1000) pulleys? Is that something I have to get from MB or can I buy on-line somewhere?
You and I have e-talked about this last year, where I offered to have a local machine shop make you a pulley. The critical dimension is not so much the diameter, but it is the six-sided hole in the pulley that goes on the shaft. Initial kits had the dimension of Y inches. Mine is exactly 0.625". You need to measure the six-sided hole in your pulley. Having said all this, I would think that MB would have (or can get you) a pulley.
To my knowledge they are not available on-line. MB explained to me that he did not want somebody calling up Paxton and ordering their standard pulley with round holes, for fear of that person over-boosting their engine. The standard Paxton shaft is just a round hole with a keyway in it. Anybody can make these; however, making a pulley with a six-sided hole requires a machine broach, and a "bare bones" machine shop will not have this.
Boy, could somebody have fun with that one!
Sorry, could not resist. Actually, are you still with the same French company employer (and that is a serious question, company name begins with "D")?What precisely were the changes between your 383 HP run and your 340+ HP run?
Only two things - I leaned out the fuel map and on the day that I re-dyno'ed, I changed the supercharger belt. No other changes.
As I understand you did change your fuel map but did you also not change your timing map?
Changed fuel map, did not change timing map, except...............
I guess I'm wondering if you switched SS boxes in between the results?
Yes, new SS box installed back in December.
If so, what timing values did you use from the old box to the new? Same, or some multiplication?
...............I took the "same" values; however, per MB's instruction multiplied them by exactly 2x, cell-for-cell, in the new box.
Your belt slipping should be detectable by overlaying the graphs. If a belt slip (lower boost) your HP curves should be nearly identical up to about 6 PSI - I'm guessing that is around 6500 RPM.
Respectfully, not necessarily. If a belt is slipping, the HP across the RPM band will be reduced by x-amount because boost is lessened by y-amount. Upon closer examination of the before-n-after HP curves, this is very evident. The shape of the two curves is virtually identical; however, one is "just below" the other.
Where can I source a couple of smaller (Novi 1000) pulleys? Is that something I have to get from MB or can I buy on-line somewhere?
You and I have e-talked about this last year, where I offered to have a local machine shop make you a pulley. The critical dimension is not so much the diameter, but it is the six-sided hole in the pulley that goes on the shaft. Initial kits had the dimension of Y inches. Mine is exactly 0.625". You need to measure the six-sided hole in your pulley. Having said all this, I would think that MB would have (or can get you) a pulley.
To my knowledge they are not available on-line. MB explained to me that he did not want somebody calling up Paxton and ordering their standard pulley with round holes, for fear of that person over-boosting their engine. The standard Paxton shaft is just a round hole with a keyway in it. Anybody can make these; however, making a pulley with a six-sided hole requires a machine broach, and a "bare bones" machine shop will not have this.
I'm in Paris currently.
Boy, could somebody have fun with that one!
Actually, I was with Paris (Hilton) Saturday night at the 2 yr anniversary of LIGHT at the Bellagio. Unfortunately, I wasn't IN Paris though . .
Boy, could somebody have fun with that one!
Actually, I was with Paris (Hilton) Saturday night at the 2 yr anniversary of LIGHT at the Bellagio. Unfortunately, I wasn't IN Paris though . .
I ordered a few different sized pulleys from Mark B. Probably best as the shaft configuration fits perfect.
Armando
Armando
Andy, and whoever else cares;
I work for Dassault Systemes... for almost 24 years now. We have a 70%+ marketshare of the automobile makers worldwide and an 85+% of the Aerospace market. So, when you are driving in a car or flying in a plane, the chances are it was designed/manufactured with our software solutions.
Several years ago we won Honda (one reason I was often in Japan and being forced to go to the NSX factory so often!)
Last year we had two major wins in Auto - having won significant strategic contracts with Ford and Toyota.
End of advertisement:
Andy, from you answers it is very clear that your HP differences are because of timing changes. I know what MB has said about 2X the numbers in the new box, but I respectfully disagree. I say this after extensive discussions with the owner/author of the SS software at SS. Both boxes treat the timing numbers EXACTLY the same.
That said, perhaps it is both safer and wiser to run more (2X)retard. I would not recommend against MB (my engine replacement guarantee does not exist!) My advice is to stay with this timing. FWIW, I set mine somewhere in between... about 1.5X SS box values.
Also, I beg to disagree with you on belt slipping in SC applications. You will NOT typically see slipping until higher boost levels wen there is correspondingly more resistance in the pulley. So, when you say you have the same curve as before - basically just offset lower - I say this is characteristic of pulling timing out. Belt slip, in my experience (similar SC applications), will not occur until higher boost and you will have maps on top of each other until very near the maximum achieved boost pressure.
JMO. Take care.
I work for Dassault Systemes... for almost 24 years now. We have a 70%+ marketshare of the automobile makers worldwide and an 85+% of the Aerospace market. So, when you are driving in a car or flying in a plane, the chances are it was designed/manufactured with our software solutions.
Several years ago we won Honda (one reason I was often in Japan and being forced to go to the NSX factory so often!)
Last year we had two major wins in Auto - having won significant strategic contracts with Ford and Toyota.
End of advertisement:
Andy, from you answers it is very clear that your HP differences are because of timing changes. I know what MB has said about 2X the numbers in the new box, but I respectfully disagree. I say this after extensive discussions with the owner/author of the SS software at SS. Both boxes treat the timing numbers EXACTLY the same.
That said, perhaps it is both safer and wiser to run more (2X)retard. I would not recommend against MB (my engine replacement guarantee does not exist!) My advice is to stay with this timing. FWIW, I set mine somewhere in between... about 1.5X SS box values.
Also, I beg to disagree with you on belt slipping in SC applications. You will NOT typically see slipping until higher boost levels wen there is correspondingly more resistance in the pulley. So, when you say you have the same curve as before - basically just offset lower - I say this is characteristic of pulling timing out. Belt slip, in my experience (similar SC applications), will not occur until higher boost and you will have maps on top of each other until very near the maximum achieved boost pressure.
JMO. Take care.
Yellow Rose
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Andy, from you answers it is very clear that your HP differences are because of timing changes.
Agree, but only a partial contributor, because..........
That said, perhaps it is both safer and wiser to run more (2X) retard. I would not recommend against MB (my engine replacement guarantee does not exist!) My advice is to stay with this timing. FWIW, I set mine somewhere in between... about 1.5X SS box values.
I really need to get that scanner. Just talked to my buddy.....he will loan it to me this Saturday. Except rain is in the forecast for this weekend.
You will NOT typically see slipping until higher boost levels when there is correspondingly more resistance in the pulley. So, when you say you have the same curve as before - basically just offset lower - I say this is characteristic of pulling timing out. Belt slip, in my experience (similar SC applications), will not occur until higher boost and you will have maps on top of each other until very near the maximum achieved boost pressure.
..........because the belt is (was) also slipping. The curves are offset (timing); however, as you stated the curves begin to significantly diverge at 6500 RPM (slippage).
Last Friday my boost was 8.0 PSI as recorded by the SS. After the dyno on Saturday it was 5.8 PSI. About an hour ago I snugged the belt a little more and I just got back from an SS recording.....the boost is 6.8 PSI. No BS here, I can feel the 1 PSI difference!!! Using the can-you-twist-the-belt-90° rule, there is room to snug the belt a bit more, ostensibly to get back to the previous 8 PSI from last week.
Rhetorically speaking, if I was down 40-ish HP because of less timing and too loose of a belt, then with restored boost my power reduction is perhaps 20-ish HP. I determined this value by extrapolating the new power curve from the time it begins to diverge, and continue on a straight “offset” line. That is only a 5% loss, which to me is "lost in the noise" and worth the comfort factor knowing the timing is not too aggressive.
Agree, but only a partial contributor, because..........
That said, perhaps it is both safer and wiser to run more (2X) retard. I would not recommend against MB (my engine replacement guarantee does not exist!) My advice is to stay with this timing. FWIW, I set mine somewhere in between... about 1.5X SS box values.
I really need to get that scanner. Just talked to my buddy.....he will loan it to me this Saturday. Except rain is in the forecast for this weekend.
You will NOT typically see slipping until higher boost levels when there is correspondingly more resistance in the pulley. So, when you say you have the same curve as before - basically just offset lower - I say this is characteristic of pulling timing out. Belt slip, in my experience (similar SC applications), will not occur until higher boost and you will have maps on top of each other until very near the maximum achieved boost pressure.
..........because the belt is (was) also slipping. The curves are offset (timing); however, as you stated the curves begin to significantly diverge at 6500 RPM (slippage).
Last Friday my boost was 8.0 PSI as recorded by the SS. After the dyno on Saturday it was 5.8 PSI. About an hour ago I snugged the belt a little more and I just got back from an SS recording.....the boost is 6.8 PSI. No BS here, I can feel the 1 PSI difference!!! Using the can-you-twist-the-belt-90° rule, there is room to snug the belt a bit more, ostensibly to get back to the previous 8 PSI from last week.
Rhetorically speaking, if I was down 40-ish HP because of less timing and too loose of a belt, then with restored boost my power reduction is perhaps 20-ish HP. I determined this value by extrapolating the new power curve from the time it begins to diverge, and continue on a straight “offset” line. That is only a 5% loss, which to me is "lost in the noise" and worth the comfort factor knowing the timing is not too aggressive.
Andy, I heard you are going to go up to 10 psi. Will the belt hold combined with the smaller pully. Somebody out there cranked up the pulley tension and ended up with some main bearing damage. Also, this will be on stock internals and the ss box, correct. I need to give you credit, you have more bravado than I. Dan
Yellow Rose
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Andy, I heard you are going to go up to 10 PSI.
The diameter of the supercharger pulley currently on the car is 4.1". I have another pulley in the garage that is 3.4" in diameter. Using the Affinity Laws, 8 PSI with the large pulley will result in a theoretical 11.6 PSI with the small pulley.
I emphasize the word “theoretical” because we temporarily had the small pulley on the car at NSXPO 2002 and I think it was making 9.5 PSI. We put the large pulley back on because we did not have enough time to create a fuel map for the small pulley.
Is the small pulley worth it? This is something only I can answer with regards to balance between go-fast and reliability. Looking at my recent dyno plot and using unscientific but logical thinking, for my car 1 PSI equates to approximately 10 HP at redline. Depending on what the resulting actual boost will be with the small pulley, there is 15 to 35 HP that may potentially be added. Split the difference and call it 25 HP. Bang for the buck, that is the most economical NSX horsepower increase - the shorter belt is only $45, so it’s at least worth a try. If things don’t work out, I swap pulleys / belts and I’m done.
Will the belt hold combined with the smaller pulley?
Although the small pulley was on the car for only a brief time, I do not recall the belt slipping. However, it is intuitive that over long term the belt will wear faster because of the tighter bend radius. Maybe instead of changing the belt every twelve months, it would need to be changed every six or eight months. I would even consider using aerosol belt dressing
for a few days until I can get it replaced, if the belt begins to slip badly at the end of its useful life,
Somebody out there cranked up the pulley tension and ended up with some main bearing damage.
They must have really had that belt tight. The rule-of-thumb that I use to determine if the belt is adequately tight is as follows. If with your thumb and first finger you can twist the belt at the mid-point of the longest span more than 90° it is too loose. If you cannot twist it 90° it is too tight. Obviously, this is rather subjective depending on the strength of your forearms compared to mine.
Also, this will be on stock internals and the SS box, correct?
Stock internals with regards to no deck, no sleeves? Yes, but I do have low compression pistons.
I need to give you credit, you have more bravado than I.
Makes up for my lack of manners.
The diameter of the supercharger pulley currently on the car is 4.1". I have another pulley in the garage that is 3.4" in diameter. Using the Affinity Laws, 8 PSI with the large pulley will result in a theoretical 11.6 PSI with the small pulley.
I emphasize the word “theoretical” because we temporarily had the small pulley on the car at NSXPO 2002 and I think it was making 9.5 PSI. We put the large pulley back on because we did not have enough time to create a fuel map for the small pulley.
Is the small pulley worth it? This is something only I can answer with regards to balance between go-fast and reliability. Looking at my recent dyno plot and using unscientific but logical thinking, for my car 1 PSI equates to approximately 10 HP at redline. Depending on what the resulting actual boost will be with the small pulley, there is 15 to 35 HP that may potentially be added. Split the difference and call it 25 HP. Bang for the buck, that is the most economical NSX horsepower increase - the shorter belt is only $45, so it’s at least worth a try. If things don’t work out, I swap pulleys / belts and I’m done.
Will the belt hold combined with the smaller pulley?
Although the small pulley was on the car for only a brief time, I do not recall the belt slipping. However, it is intuitive that over long term the belt will wear faster because of the tighter bend radius. Maybe instead of changing the belt every twelve months, it would need to be changed every six or eight months. I would even consider using aerosol belt dressing
for a few days until I can get it replaced, if the belt begins to slip badly at the end of its useful life, Somebody out there cranked up the pulley tension and ended up with some main bearing damage.
They must have really had that belt tight. The rule-of-thumb that I use to determine if the belt is adequately tight is as follows. If with your thumb and first finger you can twist the belt at the mid-point of the longest span more than 90° it is too loose. If you cannot twist it 90° it is too tight. Obviously, this is rather subjective depending on the strength of your forearms compared to mine.
Also, this will be on stock internals and the SS box, correct?
Stock internals with regards to no deck, no sleeves? Yes, but I do have low compression pistons.
I need to give you credit, you have more bravado than I.
Makes up for my lack of manners.
Yellow Rose
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Andy, my concern was if you had the smaller pulley you would have less contact area.
Agree with that. At some point, the diameter becomes too small for a multi-rib belt to adequately grip the pulley. What is this threshold? I don't know, but from the looks in a picture somewhere here on PRIME (I don't recall the thread) there is a BBSC pulley even smaller than my small 3.4" pulley. I have given some thought to converting to a cogged belt arrangement if I go to an extreme, but that is really just a folly. I have found some to wrap around an extremely small pulley diameter; however, the cogged belts do not have (a) power rating or (b) speed rating.
The low comp pistons are good but will the SS box pull enough timing out. What is its range?
The old SS boxes were not 100% effective in pulling out timing. The new SS boxes are, because there is improved crank / cam sensor wiring input to the electronics. I have not explored the upper range of the new SS box's timing map; however, I can tell you that at redline the cell value for 8 PSI is 9.2 in my box. Somewhere here within PRIME (again, I don't know which thread it is within) I think I read that it is recommended to conservatively retard timing by 1° per 1 PSI of boost. Others said with good gasoline you might could pull out a little less timing.
My understanding in the SS box, the cell values in the fuel map are relative. Relative to what I don't know, other than you must have 13.8 in four critical cells that are read by the ECU at key-on. The 13.8 (and subsequent cell numbers) in the fuel map do not equate to air-fuel ratio. The numbers are relative to injector pulse width / duration. Kendall? Nut? Kodiac? BZ? However, the values in the timing map are absolute. Therefore, the above 9.2 equates to 9.2° of retard. For an 8 PSI pulley this is nice. However, if I elect to increase boost, then obviously a global cell change will be required in the cells that correspond to boost.
Agree with that. At some point, the diameter becomes too small for a multi-rib belt to adequately grip the pulley. What is this threshold? I don't know, but from the looks in a picture somewhere here on PRIME (I don't recall the thread) there is a BBSC pulley even smaller than my small 3.4" pulley. I have given some thought to converting to a cogged belt arrangement if I go to an extreme, but that is really just a folly. I have found some to wrap around an extremely small pulley diameter; however, the cogged belts do not have (a) power rating or (b) speed rating.
The low comp pistons are good but will the SS box pull enough timing out. What is its range?
The old SS boxes were not 100% effective in pulling out timing. The new SS boxes are, because there is improved crank / cam sensor wiring input to the electronics. I have not explored the upper range of the new SS box's timing map; however, I can tell you that at redline the cell value for 8 PSI is 9.2 in my box. Somewhere here within PRIME (again, I don't know which thread it is within) I think I read that it is recommended to conservatively retard timing by 1° per 1 PSI of boost. Others said with good gasoline you might could pull out a little less timing.
My understanding in the SS box, the cell values in the fuel map are relative. Relative to what I don't know, other than you must have 13.8 in four critical cells that are read by the ECU at key-on. The 13.8 (and subsequent cell numbers) in the fuel map do not equate to air-fuel ratio. The numbers are relative to injector pulse width / duration. Kendall? Nut? Kodiac? BZ? However, the values in the timing map are absolute. Therefore, the above 9.2 equates to 9.2° of retard. For an 8 PSI pulley this is nice. However, if I elect to increase boost, then obviously a global cell change will be required in the cells that correspond to boost.
Yellow Rose
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Scanner Results
Sorry, another semi-long post.....but important.
This past weekend I plugged in the Honda PGM Tester into my OBD-2 port. Before I continue, let me preface the results. The Honda dealership that I borrowed the scanner from, has four of these devices. At any one time, on average, one scanner is unavailable because of repairs. Often, it is the program card that acts up. I went there to have my car tech inspected for an upcoming track event and picked up the scanner towards the end of business on Saturday. They are closed Sunday, but because the two remaining scanners both went out on Friday, they had to have it back first thing Monday morning. As nifty as these devices are to provide ECU readings, one may wonder if the readings are valid. More on this later.
Somewhere I read that short-term fuel trim and long-term fuel trim should be as close to zero as possible. When the tech was showing me how to scroll through the menu, I asked him about STFT / LTFT. His reply was along the lines of, "No, the values are not as close as possible to zero. They should be as close as possible to one-point-zero." While he was showing me how to operate the scanner, it lost communication with the ECU two or three times.
When I got home, it took me almost ten attempts before the scanner would recognize the ECU, despite me following the same steps as the tech did back at the dealership. Once configured, while we were making data runs, the scanner lost communication with the ECU about five times. On a couple of occasions it prompted me to plug the scanner into a 12 VDC power source because the battery is low, despite the fact that the car's battery powers the scanner when it is plugged into the OBD-2 port. Needless to say, this user questions the dependability of the scanner I used, even though it was loaned to me.....very frustrating. No wonder that dealership has four of these scanners.
On the day of the data logs, it was approximately 73 °F ambient temperature. Running the car hard ranged the coolant temperature from 182-196 °F with a corresponding air inlet temperature of 135-142 °F. STFT varied from 1.02 to 1.05 and LTFT was generally in the 0.91 to 0.93 range. I suspect that over time the LTFT will show to approach 1.00. Keep in mind that fuel trims will fluctuate, but these numbers are representative of the data logging. Fuel injector pulse was 2.01 ms.
I save the best for last - spark advance. Timing at idle was 13-14° BTDC, which is what the service manual calls for. Somewhere here on PRIME it was suggested that timing on a stock NSX is around 25° BTDC, but a subsequent post stated that timing at redline was in the 40's. According to the Honda scanner, regardless if I am in second gear going 20 MPH with constant throttle input (vacuum), fourth gear going 40 MPH with constant throttle input (vacuum) or nailing the throttle up to redline (boost) the timing advance is around 47° BTDC. I do not believe this number for reasons - if timing was that advanced with my 8 PSI of boost there is no way the engine will have survived the past eighteen months and the SS box is lying to the ECU because timing changes with load and RPM.
We already know that the SS uses its own MAP sensor to lie to the ECU to control fuel. Additionally, the SS intercepts and manipulates the timing inputs from the two cam angle sensors and the two crank angle sensors. It then conveys altered signals to the ECU via "the back door". With the BBSC + SS, the ECU thinks it is controlling a naturally aspirated engine. So when you plug a scanner into "the front door" the ECU will report values that it is programmed to do so from Tochigi. Despite the timing being retarded, because the ECU doesn't know timing is being retarded, it reports to the scanner the above 47° BTDC thinking everything is ok. By the way, I think I remember MAP voltage of 2.7 mV, but I don't recall if that was at idle, cruising or under throttle.
So we have a real conundrum of three sorts (a) is timing being retarded (b) just what is the timing at redline (c) how do we determine true timing?
With respect to the first question, I think the answer is "yes". Intuitively, there is no way a forced induction NSX engine will survive with 47° BTDC of timing. It has been suggested that at redline, a boosted NSX engine should be at approximately 18° BTDC of timing.
With respect to the next two questions, a fellow BBSCer came up with a pretty slick idea. Have a fully degreed harmonic balancer pulley made at a machine shop, install it on the engine and shoot an induction timing light at the marks while the car is on a dyno. I see two obstacles with this - potentially high machine shop cost because of low demand and the danger of standing next to a dyno drum spinning at 120 MPH. But there are alternatives.
Removing the RR tire provides direct viewing access to the harmonic balancer. With a machinist's protractor and scribe, you can mark the rim of the pulley in 1° increments. Since the factory balancer already has 14° BTDC marked on the pulley, along with the +1° and the -1° mark (or is it +/-2° ?), you may not even need a protractor to scribe five additional marks to get you to 20° BTDC.
As far as the safety issue, I don't see an immediate solution other than building some sort of stable work platform that is firmly secured to the garage floor, and standing on it. You will have to crouch down to get close to the fender because the timing marks may be difficult to see.
Sorry, another semi-long post.....but important.
This past weekend I plugged in the Honda PGM Tester into my OBD-2 port. Before I continue, let me preface the results. The Honda dealership that I borrowed the scanner from, has four of these devices. At any one time, on average, one scanner is unavailable because of repairs. Often, it is the program card that acts up. I went there to have my car tech inspected for an upcoming track event and picked up the scanner towards the end of business on Saturday. They are closed Sunday, but because the two remaining scanners both went out on Friday, they had to have it back first thing Monday morning. As nifty as these devices are to provide ECU readings, one may wonder if the readings are valid. More on this later.
Somewhere I read that short-term fuel trim and long-term fuel trim should be as close to zero as possible. When the tech was showing me how to scroll through the menu, I asked him about STFT / LTFT. His reply was along the lines of, "No, the values are not as close as possible to zero. They should be as close as possible to one-point-zero." While he was showing me how to operate the scanner, it lost communication with the ECU two or three times.
When I got home, it took me almost ten attempts before the scanner would recognize the ECU, despite me following the same steps as the tech did back at the dealership. Once configured, while we were making data runs, the scanner lost communication with the ECU about five times. On a couple of occasions it prompted me to plug the scanner into a 12 VDC power source because the battery is low, despite the fact that the car's battery powers the scanner when it is plugged into the OBD-2 port. Needless to say, this user questions the dependability of the scanner I used, even though it was loaned to me.....very frustrating. No wonder that dealership has four of these scanners.
On the day of the data logs, it was approximately 73 °F ambient temperature. Running the car hard ranged the coolant temperature from 182-196 °F with a corresponding air inlet temperature of 135-142 °F. STFT varied from 1.02 to 1.05 and LTFT was generally in the 0.91 to 0.93 range. I suspect that over time the LTFT will show to approach 1.00. Keep in mind that fuel trims will fluctuate, but these numbers are representative of the data logging. Fuel injector pulse was 2.01 ms.
I save the best for last - spark advance. Timing at idle was 13-14° BTDC, which is what the service manual calls for. Somewhere here on PRIME it was suggested that timing on a stock NSX is around 25° BTDC, but a subsequent post stated that timing at redline was in the 40's. According to the Honda scanner, regardless if I am in second gear going 20 MPH with constant throttle input (vacuum), fourth gear going 40 MPH with constant throttle input (vacuum) or nailing the throttle up to redline (boost) the timing advance is around 47° BTDC. I do not believe this number for reasons - if timing was that advanced with my 8 PSI of boost there is no way the engine will have survived the past eighteen months and the SS box is lying to the ECU because timing changes with load and RPM.
We already know that the SS uses its own MAP sensor to lie to the ECU to control fuel. Additionally, the SS intercepts and manipulates the timing inputs from the two cam angle sensors and the two crank angle sensors. It then conveys altered signals to the ECU via "the back door". With the BBSC + SS, the ECU thinks it is controlling a naturally aspirated engine. So when you plug a scanner into "the front door" the ECU will report values that it is programmed to do so from Tochigi. Despite the timing being retarded, because the ECU doesn't know timing is being retarded, it reports to the scanner the above 47° BTDC thinking everything is ok. By the way, I think I remember MAP voltage of 2.7 mV, but I don't recall if that was at idle, cruising or under throttle.
So we have a real conundrum of three sorts (a) is timing being retarded (b) just what is the timing at redline (c) how do we determine true timing?
With respect to the first question, I think the answer is "yes". Intuitively, there is no way a forced induction NSX engine will survive with 47° BTDC of timing. It has been suggested that at redline, a boosted NSX engine should be at approximately 18° BTDC of timing.
With respect to the next two questions, a fellow BBSCer came up with a pretty slick idea. Have a fully degreed harmonic balancer pulley made at a machine shop, install it on the engine and shoot an induction timing light at the marks while the car is on a dyno. I see two obstacles with this - potentially high machine shop cost because of low demand and the danger of standing next to a dyno drum spinning at 120 MPH. But there are alternatives.
Removing the RR tire provides direct viewing access to the harmonic balancer. With a machinist's protractor and scribe, you can mark the rim of the pulley in 1° increments. Since the factory balancer already has 14° BTDC marked on the pulley, along with the +1° and the -1° mark (or is it +/-2° ?), you may not even need a protractor to scribe five additional marks to get you to 20° BTDC.
As far as the safety issue, I don't see an immediate solution other than building some sort of stable work platform that is firmly secured to the garage floor, and standing on it. You will have to crouch down to get close to the fender because the timing marks may be difficult to see.
Andy, let me get this straight, the ss takes the ecu outputs and changes them as per your ss map programs. Now you are looking at the ecu factory outputs before they are changed or are you downstream of the SS with your datalog. Reading your post makes my head spin with the amount of work you will need to do to sort this all out. Here I go again, just chuck the thing and go tec3, AEM or Motec and and you will know EXACTLY what you have. Dan
That' the first thing that came to my mind as well, but Andy is OBDII. AEM needs to come out with TBW support for their ECU.tunapie said:
Yellow Rose
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Andy, let me get this straight, the SS takes the ECU outputs.....
Instead of ECU outputs, the SS is looking for ECU inputs - the SS MAP sensor, the two OEM crank angle sensors and the two OEM cam angle sensors.
.....and changes them as per your SS map programs.
As I understand it, correct. Caveat.....I do not know the electronic algorithm by which this is accomplished.
Now you are looking at the ECU factory outputs before they are changed downstream of the SS with your datalog.
I don’t know exactly, thus the purpose of my post.
One thing I forgot to mention in my previous post - knock retard (0° BTDC) was never engaged. This suggests to me that indeed there was no pre-detonation.
Reading your post makes my head spin with the amount of work you will need to do to sort this all out.
Then you should read the tachometer plugged into my head.
Big horsepower is not easy unless we purchase GT-2’s.....but I like the body style of the NSX any day of the week.
Here I go again, just chuck the thing and go tec3, AEM or Motec and you will know EXACTLY what you have.
Except those options are only available for OBD-1.....I am OBD-2. Actually, I have heard that Motec offers a “piggyback” module to their main controller that allows throttle-by-wire input for OBD-2 NSXs.
That’s the first thing that came to my mind as well, but Andy is OBDII. AEM needs to come out with TBW support for their ECU.
In a phone conversation that I had with them last year, this will not happen any time soon.....if at all.
Instead of ECU outputs, the SS is looking for ECU inputs - the SS MAP sensor, the two OEM crank angle sensors and the two OEM cam angle sensors.
.....and changes them as per your SS map programs.
As I understand it, correct. Caveat.....I do not know the electronic algorithm by which this is accomplished.
Now you are looking at the ECU factory outputs before they are changed downstream of the SS with your datalog.
I don’t know exactly, thus the purpose of my post.
One thing I forgot to mention in my previous post - knock retard (0° BTDC) was never engaged. This suggests to me that indeed there was no pre-detonation.
Reading your post makes my head spin with the amount of work you will need to do to sort this all out.
Then you should read the tachometer plugged into my head.
Big horsepower is not easy unless we purchase GT-2’s.....but I like the body style of the NSX any day of the week.
Here I go again, just chuck the thing and go tec3, AEM or Motec and you will know EXACTLY what you have.
Except those options are only available for OBD-1.....I am OBD-2. Actually, I have heard that Motec offers a “piggyback” module to their main controller that allows throttle-by-wire input for OBD-2 NSXs.
That’s the first thing that came to my mind as well, but Andy is OBDII. AEM needs to come out with TBW support for their ECU.
In a phone conversation that I had with them last year, this will not happen any time soon.....if at all.
The M600 and M800 support throttle by wire, but at the price (with the required custom harness) they ask, I find it very unlikely that they will ever sell a single one to any NSX owner.AndyVecsey said:
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New SS box wiring
May I interrupt this great technical discussion with a request?
I received my new SS box from Mark some months back. Unfortuantely this was without any install instructions. I was an early install and my original box wiring was soldered in-line with the ECU harness. Is the color coding for the new box wires the same as the original, such that I simply match them to the new box? What are the extra wires...where do they go??
Is there any written guide to the exchange?
Finally, I was running the orginal, unaltered "killer"file. Can I load this into the new box as a start.
Thanks,
James
May I interrupt this great technical discussion with a request?
I received my new SS box from Mark some months back. Unfortuantely this was without any install instructions. I was an early install and my original box wiring was soldered in-line with the ECU harness. Is the color coding for the new box wires the same as the original, such that I simply match them to the new box? What are the extra wires...where do they go??
Is there any written guide to the exchange?
Finally, I was running the orginal, unaltered "killer"file. Can I load this into the new box as a start.
Thanks,
James
I don't have an answer for you, but thought that there might be something in the owners area of the baschboost.com website, so I took a peak to see. No more website I guess. 
Re: Scanner Results
Indeed.
The latter is much more likely for any performance engine and consistent with the base NSX configuration for the AEM.
That would seem reasonable or a bit high for an unaltered value, so I agree that the scanner is probably being lied to just as is the ECU. Too bad.
The first part is probably true unless running quite rich (which yours may have been for awhile) but remember that the basic CTSC has no timing retard and no after cooler. But, at 8psi and no sign of ping I think it supports your assumption, not to mention the now lowered HP.
18 degrees at max boost & RPM is a bit too general. The rule of thumb is 1 degree per PSI of boost but I have argued that the NSX, especially those of us with stock internals, may need more retard. Meanwhile, the bits and pieces we hear from the pros make me think that they too are pulling a bit more than that to allow for a leaner mixture and better overall power under the curve. Of course, they know what their timing map looks like but I'm not sure they know how much they are pulling relative to stock. Your test suggests that stock will go as high as 47 degrees. If so, then the rule of thumb would mean ~29 at redline and 18psi. I'm guessing they run less but by no means willing to bet on it.
I like the idea for a DIY degreed pulley. You can do it well enough for a reasonably close measurement during a dyno pull
AndyVecsey said:
Indeed.
The latter is much more likely for any performance engine and consistent with the base NSX configuration for the AEM.
That would seem reasonable or a bit high for an unaltered value, so I agree that the scanner is probably being lied to just as is the ECU. Too bad.
The first part is probably true unless running quite rich (which yours may have been for awhile) but remember that the basic CTSC has no timing retard and no after cooler. But, at 8psi and no sign of ping I think it supports your assumption, not to mention the now lowered HP.
18 degrees at max boost & RPM is a bit too general. The rule of thumb is 1 degree per PSI of boost but I have argued that the NSX, especially those of us with stock internals, may need more retard. Meanwhile, the bits and pieces we hear from the pros make me think that they too are pulling a bit more than that to allow for a leaner mixture and better overall power under the curve. Of course, they know what their timing map looks like but I'm not sure they know how much they are pulling relative to stock. Your test suggests that stock will go as high as 47 degrees. If so, then the rule of thumb would mean ~29 at redline and 18psi. I'm guessing they run less but by no means willing to bet on it.
I like the idea for a DIY degreed pulley. You can do it well enough for a reasonably close measurement during a dyno pull
AndyVecsey said:
The 47° number you saw under light cruising conditions corresponds exactly with factory Honda low cam ignition map numbers in the 17 to 20 inches of vacuum range all the way to 5000 RPM.
As for the same 47° number full throttle to redline, this doesn't make sense when looking at the factory honda ignition map in the 1 atmosphere (full throttle) portion.
Here is an OEM Honda ignition map plot - full throttle, 1 atmosphere (zero vacuum), low and high cam to redline:
Attachments
i just got my low comp obd II BBsc with SSBB home from MB. unfortunately we ran out of time at the dyno when i picked it up, so it still needs some tweeking. The ssbb is very intuitive and I was able to follow the process as mark worked. (btw it put out 415 rwhp while running very rich!) i hope to be mid 400's when devin applies the finishing touches next week!
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Devin / Gerry - thanks for your comments........
The curve above shows a dip in timing in the 6000's RPM range. Now that I think about it, my co-pilot mentioned a brief drop in timing to something like 30-ish °BTDC. This is consistent with the above plot.
More Q-n-A's later.
The curve above shows a dip in timing in the 6000's RPM range. Now that I think about it, my co-pilot mentioned a brief drop in timing to something like 30-ish °BTDC. This is consistent with the above plot.
More Q-n-A's later.
Yellow Rose
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.....btw it put out 415 rwhp.....
You bastard!
You bastard!
