BBSC New SS Box Thread

[sjs]

...MB - I have heard a rule of thumb that a forced induction NSX engine behaves well by retarding the timing 6° per 1000 RPM beginning at 5000 RPM...

That was the approach used by Bell/Mectech when they modified the stock ECU, but only because they had no better option available. The primary driver for retard should be load/boost, although RPM can also be a (lesser) factor.

The comment about 1 degree per PSI is not uncommon but I think perhaps a bit low for the NSX which starts with quite a lot of advance.

 

[PaynNSX]

The stock NSX has the max advance at around 40 degrees at redline.

Can I ask where you got the data to support that? Or, were you measuring advance under part throttle at redline?

 

[kpond]

The comment about 1 degree per PSI is not uncommon but I think perhaps a bit low for the NSX which starts with quite a lot of advance.

sjs, I believe everything is relative. If we acknowledge that the NSX runs more advance than a typical high performance car, then it would stand to reason for me that head design, flow characteristics, black magic, etc have all contributed to the factory becoming comfortable with the timing settings that they have chosen. Take that same car, same heads, same flow characteristics, etc.... then I'm still OK with the same rule of thumb when blown.

According to Mark at SS, the NSX exhibits a very loud and pronounced pinging that is not hidden at all. According to Mark's experience on a multitude of cars, some have subtle pinging that is hard to detect from other presumably normal engine sounds. Not so with the NSX which he claims is pronounced.

That said, I can say that I have only heard my car ping once and that was for about 2 seconds on a steep hill on a hot day under moderate throttle. This is when I first got my car back after the SC install (more than 1 year ago). With all of the subsequent tuning I have done (and careful attentions the entire time to af's), I have never had it ping again.

The data point that concerns me is the more recent BBSC failures that have occured and what little information we have available to the masses as to what the symptoms were. I, for one, would like to know much more. For example, the prevailing theory was that the SS box didn't hold timing retard correctly which ultimately led to the demise of one or more cylinders. OK then, it would stand to reason that the owners would have heard pinging??? Furthermore, if you don't have any pinging, can you assume you are OK??

 

[sjs]

sjs, I believe everything is relative. If we acknowledge that the NSX runs more advance than a typical high performance car, then it would stand to reason for me that head design, flow characteristics, black magic, etc have all contributed to the factory becoming comfortable with the timing settings that they have chosen. Take that same car, same heads, same flow characteristics, etc.... then I'm still OK with the same rule of thumb when blown.

Not enough data yet to say for sure, and at the risk of stating the obvious, when in doubt...

The standard ~6psi BBSC is not intercooled, so one might be tempted to pull a bit more advance for that reason as well.

Ping can be very clearly heard in the NSX, I've certainly had my share, but I'm not sure that means there aren't other conditions when it is not audible.

 

[Yellow Rose]

First off, Kendall, I hope you don't mind that you'll recognize your words below are imported from the "Bad Cats ??" thread that I started. I did so for two reasons - when I posted the "Bad Cats ??" thread yesterday, I really did think that the cats are the culprit (even today, my exhaust smells much different than just two days ago with no map changes) and your words below in bold are a bit more fitting for this thread as it relates to electronics instead of cats, per se. I hope you don't mind. Besides, this is in accordance with the first few words in the opening line of the debut post in this thread - SS discussion.

.....my theory is that the SS box which is programmed to pass lies, lies, and more lies to the ECU of MAP values, has caused the ECU to set the EGR valve position incorrectly.

Yes, but the EGR valve has a lift position sensor on it that would confirm back to the ECU, that the EGR valve is where the ECU wants it to be. The convolution is that the ECU is setting the EGR valve position based on more inputs than just the MAP sensor - SS or OEM. My understanding is that there are other variables the ECU will take into consideration when setting the EGR position. Therefore, the SS's MAP sensor may or may not be the culprit. Hmmm, very intriguing.

I too had this problem and was only able to resolve by re-installing my stock injectors and bypassing the SS box.

And re-activating the factory MAP sensor.

I passed on the first try after these mods.

Last year I passed on the first try without going through what you did Kendall. At the time, when I saw the word "passed" on the receipt, I simply filed away the paperwork without taking a look at the results. I did not realize how close to the limit I was on one of the parameters. When you "defeated" the SS for your inspection, were the resulting numbers "borderline, but legal" like mine or were they well within the acceptable range?

 

[the nsxnut]

This is a quality thread...

To Andy, re: e-testing:

some things I have learned, by trial and error:
- the SS black box WILL control AFR in the vacuum range of the table. IOW, you CAN program lean values for the specific purpose of emissions testing. Of course, that requires a whole tuning session to find the optimum lean settings (target: stoich 14:1), simulating test conditions (15/25 mph). I guess this is probably no more trouble than converting back to OEM settings.

- You can knock the emissions down by injecting air into the exhaust stream. I once routed a tube from my bypass valve output to my header bung! It reduced my effective emissions by about 20%.

Ultimately, I was able to get my e-measurements within range to pass, but just barely, using the SS blackbox and the 440 injectors. Needless to say, if one tunes for this purpose, you must stay out of boost range until resetting back to performance specs.
I, too, suspected my cats, and changed them out, without much effect. Ultimately, it is the rich nature of the system that makes it very difficult to meet emissions standards. Also, Andy, if memory serves me (it often fails me), you did your initial test last year with an OE fuel pump, and have since upgraded to a Walbro. A big jump in FP will def. affect emissions!

 

[the nsxnut]

Locating SS Box in the cockpit

Kendall's earlier description of his detailed and neat solution to the location of the SS BB is impressive.

I also have the need to 'plug in' my serial cable often, and came up with a less complex, and less elegant, solution for the box location. I routed my harness and hard vac line into the cockpit in the usual way, and simply mounted my box on the surface of the interior trim panel behind the passenger seat. This necessitated making some modification to the panel to allow the wiring loom and vac line to pass through the trim piece, and I also have compromised my passenger seat travel, giving up about 1.5 inches (the depth of the box) of rearward travel. Also, I removed the 'top' of the box, reconfigured the screws that fasten it to the bottom so that it is now hinged (fasten 2 on opposite sides, and leave two off), and I can simply lift the top to expose the serial port and plug in as needed in about 30 seconds. the distance from the box to the ECU is about 3-4 inches, through the trim panel. The box is not hidden, and I have modified my interior, which some may think undesirable, but I was done in about 3 hours, and find it to be very functional.

I have also seen Bruce M's setup, where he installed the box out of sight behind the trim, and routed a custom cable from the serial port to the inside of his center console. Lift the armrest lid, and there's the connection. very slick. Took him all day.

 

[KGP]

Can't score it. So...

This is one of those threads where I wish we had some forum tool available to score the content. Thanks for sharing to all, and special thanks to kpond for initiating.

 

[Yellow Rose]

Passed Emissions

As you may recall, two weeks ago my BBSCed NSX failed the emissions inspection. In another thread, I suspected that it was the cats, having been on a garage shelf collecting dust and other contaminants over the past twelve months. The car passed inspections today with similar HC, CO, NOX values as last year. I did make a few changes, from a couple of weeks ago, which I will describe below to assist fellow BBSCers.

I have a Walbro high-volume, high-pressure fuel pump. At idle, the fuel pressure is 54 PSI with the factory fuel pump resistor bypassed. I upgraded to the Walbro because of future engine plans and I defeated the resistor because it makes SS tuning easier, by having a constant voltage to the fuel pump from idle to redline. The down side of this, is that for a given value in Map A from vacuum to 0 PSI, there will be more gasoline squirted into the combustion chamber. As suggested by nsxnut (thanks, Mark) I re-installed the resistor, which results in fuel pressure at idle of 46 PSI.

I then asked myself, “How can I further reduce the fuel injected, so as to lessen HC and NOX?” Ahah, lower the Map A values from vacuum to 0 PSI. The first attempt was to reduce all values (except for the two very important cells that contain values of 13.8) by 10%. Too much - the engine went into a lean idle surge with RPM fluctuating from 800 RPM to 1300 RPM. Next try was to lower the values by 5%. Better, but the idle was very sensitive to the gas pedal and the engine would die as I lifted off of the gas when rolling to a stop with the clutch pedal pushed in. Third time is a charm - reducing the values by only 2.5%, the engine responds nicely with a borderline lean condition. Normally theoretical AFR is 14.7:1 but I have my FJO temporarily disconnected. (((Before I start tuning again, I’ll see just how lean the FJO says the current fuel map is creating. If I remember to do so, I’ll post the results here. If I forget and you are interested, PM me a reminder.))) You may be wondering why I didn’t just leave the factory fuel pump resistor off and lower the Map A values even more to achieve the equivalent threshold lean condition. That certainly would have been just as effective, and either approach will yield the same result.

Finally, as “insurance” I put five gallons of 104 octane in an almost empty tank. Did this in and of itself help? Hard to say. However, my instinct says that it does help to burn cleaner as evidenced by lower HC and NOX numbers. However, my low-speed HC was almost the same as last year and perilously close to the max limit. My theory at this point is that the old SS box is not pulling out enough timing - not only under boost but also not under vacuum, as well. All of the above is predicated on the old SS box. I will be upgrading to the new SS box in a few days. BTW, I ordered a nine-pin serial ribbon cable and a 90° serial connector. My hope is that I will be able to position the new SS quite easily within the cavity behind the passenger seat cable. Ditto with the above FJO comment, I’ll make a point to remember to report back.

Kendall you never answered some of my previous questions, which I feel are very important to this group.

When you failed emissions inspection last year with the 440 injectors and the old SS box, were the numbers “just over the limit” or were they “way over the limit”?

When you re-installed the factory injectors and disabled the SS to pass emissions, were the numbers “just under the limit” or were they “comfortably within range”?

With the new SS box, did you double the Map B values?

The relevance of your answers may substantiate my position, that changes via laptop in five minutes are most definitely more appealing than swapping injectors over the course of X hours, in order to pass emissions. In fact, MW mentioned this very possibility in an article he once wrote for NSX Driver.

 

[KGP]

Re: Passed Emissions

Finally, as “insurance” I put five gallons of 104 octane in an almost empty tank. Did this in and of itself help? Hard to say. However, my instinct says that it does help to burn cleaner as evidenced by lower HC and NOX numbers.

I guess the only way to know for sure is if you would have tested back to back, once without the 104, and then once with. You are certainly way more qualified than myself and others here on this, but I thought that the only thing a higher octane rating was relevant to was eliminating detonation?

Anyway, thanks for sharing. Good information for many, I'm sure.

 

[the nsxnut]

More excellent content, Andy. Glad you got it to pass. I'm also glad that someone else, besides me ( at least, AFAIK), was able to get some quantifiable tuning results in the vacuum range of Table A. Seems pretty straightforward to put back the resistor (steps down FP voltage), and input some lean values in the vacuum range for the purpose of passing emissions. Seems like there will come a time, though, when the borderline readings will eventually be problematic!

As far as fuel, it is true about higher octane burning cleaner. The higher the octane, the slower the flame front propogates through the combustion chamber. Slower burn=cleaner burn (more efficient combustion). Of course, it is more detonation resistant, and more expensive. The faster 'flash' of low octane fuel often leaves unburned fuel in the combustion cycle, which is, of course, very high in emissions.

Why not run all cars on high octane to reduce pollution in general? If a mfg. can make engines that pass emission standards in a detuned-state, on low octane, which is less expensive, that's what the general public wants. Take note that folks like 'us' are a tiny minority of drivers/car owners. Also, take note that, aside from cleaner combustion, there is no performance advantage to running a 'typical' engine, designed for 87 octane, on a high octane fuel. A petroleum engineer I know uses this rule of thumb: always run a motor on the lowest octane that the mfg recommends for that motor. The motor wants that grade of fuel.

Same is true for an NSX motor, unless you are using FI or other means of raising compression, there is no hp to be gained from using higher octane fuel in a stock motor rated for 93. Compression/charge density is where the power comes from, not octane.

 

[KGP]

Interesting, and well said, nsxnut. Please don't let this information leak out to the tree huggers, else we will be runing all of our cars on race gas.

 

[sjs]

I would agree with most of the above with the very minor variance that since the possible power benefit of higher octane is the avoidance of ignition timing retard in response to knock, there are times when a normally aspirated engine could still benefit from more than the suggested fuel, especially when running an enhanced ECU chip such as that from Dali or a complete ECU such as the AEM. In both cases you are likely to run more advance than normal. Likewise with other major NA mods such as cams and high compression pistons.

 

[ncdogdoc]

Steve,

I think Mark was saying that in an engine remaining the way its maker intended, there is no benefit to using a higher octane than what the maker specifies. Except in making the car lighter because there will be less in the wallet

 

[kpond]

Hi Andy,

I'll try to dig out my smog tests and get the answers you're looking for.

Based on the experiences of yourself and KGP, you are essentially saying that the NSX engine management is capable to allow the engine to run at different AFRs(depending on MAP values) during closed loop. This certainly defies conventional wisdom. Closed loop is depending on O2 readings and stock O2 sensors are esentially binary devices around stoichiometric.

That said, we have the practical cases of you and KGP where it HAS made a difference.

Hmmmm.... I sure wish this was easier. Any theories?

 

[sjs]

Steve,

I think Mark was saying that in an engine remaining the way its maker intended, there is no benefit to using a higher octane than what the maker specifies...

Agreed, but if someone focused on his statement "Same is true for an NSX motor, unless you are using FI or other means of raising compression, there is no hp to be gained from using higher octane fuel in a stock motor rated for 93" they might not think of the exceptions I mentioned. A chip or replacement ECU along with common bolt-ons could produce a condition where an otherwise stock engine experienced knock, especially at the track on a hot day. But as I said initially, that's a minor variance on a generally true statement.

 

[the nsxnut]

Steve, I agree with your exception for advancing timing in an otherwise stock motor...

 

[Yellow Rose]

Based on the experiences of yourself and KGP.....

Polite correction, I think you meant nsxnut instead of KGP.

.....you are essentially saying that the NSX engine management is capable to allow the engine to run at different AFRs (depending on MAP values) during closed loop.

I have suspected this all along during my tuning episodes with the SS. For example, one time the ECU went into “limp mode” when I was running too rich for too long. Unfortunately, we don’t know the threshold of AFR nor the threshold of time, that the ECU will allow the engine to run rich / lean.

This certainly defies conventional wisdom.

It also brings to mind something that I suggested in this (or another) thread, that the SS may not be the culprit of high NOX at idle.

Hmmmm.... I sure wish this was easier. Any theories?

No, but maybe someone can phone Stuttgart and ask them how they manage their FI engines.

 

[kpond]

Andy, thanks to correct me on my references. Sorry to nsxnut and KGP for the confusion.

Back to closed-loop.

Let's assume that the Honda engineers have tried to achieve a different AFR for various MAP inputs. How could it be achieved?

In other words, the O2 sensors are only reliable at 14.7:1, so if 13:1 or 15:1 were desired for certain conditions, I don't know how the existing engine management can achieve this.

 

[sjs]

...In other words, the O2 sensors are only reliable at 14.7:1, so if 13:1 or 15:1 were desired for certain conditions, I don't know how the existing engine management can achieve this.

Seems unlikely, but I suppose it could use what it knows about hitting 14.7, apply a correction/trim factor, then intentionally ignore the sensor until MAP changes.

 

[the nsxnut]

It is alway interesting to understand more how the ECU might manage all these functions, but it will also always be a little mysterious.

How does the Split Second Black Box interact with all that? It calibrates a signal to the ECU that determines injector duration based on input from the MAP sensor, which measures vacuum or boost (or atmospheric) pressure. The OEM MAP sensor readings are subjected to a correction factor in the equation.

So, the SSBB can manage AFR at any pressure level (vacuum or boost), as long as the inputs are correct. You can adjust to be lean or rich in any range of the map, light load or WOT. This was suggested on the BBSC list last year some time.

Perhaps the actual results of careful tuning inputs may be more important than how the ECU creates the result.

Andy's efforts and subsequent meeting of emission standards is a testiment to the flexibility of the system, and also verifies that his whole package is working. It's amazing that even with big boost, injectors, FP, etc... that the Honda motor is still low-emissions when properly tuned.

 

[kpond]

Mark,

It is difficult to refute the actual test results of you and Andy... and I am still thinking that perhaps there is another explanation. (In fact, I have a theory I will share in a moment.) At most, there is a possibility that the MAP values can have a very small effect on AFR... but not nearly to the degree that you suggest.

Once again, the NSX like virtually every other fuel injected car out there will be running in "closed loop" the majority of the time. In closed loop, there is no need for the ECU to even poll the MAP sensor - although perhaps it is taking a look just for collaboration. In closed loop, the ECU has pre-programmed tables for injector pulse width and it is using these and then verifying the results by looking at the O2 sensors. If it has the pulse width too long (rich) or too short (lean), it gets this feedback via the O2 and it can dynamically make the adjustments needed. This is why the system is called closed-loop. It is completely self-reliant... applying values and able to get and learn from the feedback. Think of it as a two-way communication.

Furthermore, in the event that the ECU cannnot, for some reason, achieve stoichimetric, it will issue a fault code and CEL. There is absolutely no ability for the ECU run leaner or richer in this closed loop mode. The stock O2 sensors are essentially binary devices arouund 14.7:1. In theory, the ECU can be either faster or slower in the way that it applies correction to errant AFR values and that is why I said that very small differences could potentially be possible. (Personally, I have my doubts about this too.)

To further make my point, the whole reason that we have this second mode, open-loop, is to allow the motor to run under richer conditions while under load. If it were possible to achieve various AFR's in closed loop, there would be no need for open loop but the fact is that open-loop exists... for this specific reason. In open-loop, the ECU's desire is to run at a richer condition, say, 13:1. Since there is no way to achieve this by monitoring O2's (only valid around 14.7:1), the car instead must rely on a variety of other sensors. In open-loop, the ECU is polling these critical sensors, MAP, temperature, etc and then it is using a look-up table to determine the right pulse width for the injectors. If the ECU is wrong, there is no way for him to know. Think of this as one-way communication. OK, so the best that can be done in open-loop mode is to do the best possible job to insure that the sensors inputs are valid. If the sesnor inputs are valid, then the ECU assumes all is well.

Several of the SS experimentors here have probably at some time put a value of greater that 13.8 into one of their MAP cells. In fact, the early tables from MB himself had a few of these values populated about. The trouble is that that the ECU NEVER expects to see a MAP value greated than 3.5v. If it does, it assumes that the MAP sensor has freaked and is therefore not reliable. The ECU will immediately throw a fault code, trigger a CEL, and go immediately to limp mode. (SS map values are simply MAP voltages x 4. A cell value of 14 = 3.5v.)

In summary, there is nothing to support the theory that MAP values can/will change AFR's during closed loop. In fact, I believe that neither you or Andy have any direct evidence of AF's being effected... but you do have the data point that changing the MAP values has enabled you to pass smog.

OK, so here's my theory. I claim that you are not effecting AFRs (for all of the aformentioned reasons) but you may be effecting the EGR valve position which will definitely change your emissions. In the NSX (which I believe is somewhat unique in this regard), the ECU computes (from external sensors) and then positions the EGR valve position. Unfortunately, the ECU also checks to see if the EGR valve has moved to the position it instructed... so it is hard to fool it. So, my theory is that in changing the MAP values via the SS box, you have both caused the EGR valve to go into a different position that is much more smog compliant.

On a final note, I am installing my FJO AFR gauge this morning. This will allow me to have real-time AFR feedback at all times. I will definitely be experimenting with SS map values and I will report back my findings.

Andy, nsxnut, please don't view my input as argumentative. I'm just trying to debate with you for the benefit of all. Other views/experiences are welcomed and appreciated.

 

[the nsxnut]

Not at all, Kendall. I think discussion like this is where we are really moving forward in our understanding. This is the leading edge of BBSC tuning, right here! MB and Mark at SS could learn from this info.

To make progress, a number of committed individuals have to be working concurrently on different approaches, and then share their findings for the betterment of the community.

However, if you state:

In fact, I believe that neither you or Andy have any direct evidence of AF's being effected

You would be mistaken. I have the files from several Dynojet runs, steady state/part throttle cruise conditions, that I specifically manipulated the vacuum range of the table to learn what effect there would be on AFR. AFR is as responsive to those inputs as it is under full boost/WOT. That is an empirical fact. HOW does this happen? I can't say exactly, but the results are indisputable.

 

[Yellow Rose]

Troika

pond, nut - excellent thread.....unlike the other recent "turbo vs super" thread; however, I digress.

Kendall - you offer up some very valid theories regarding the mystique of the NSX's ECU.

Mark - you too have some substantiated data on AFR in the vacuum columns.

This afternoon if the rain goes away, I will be re-activating my FJO with the SS fuel map that I passed with a couple of days ago. Recall, that I reduced fuel squirt by 10% - which would've resulted in a theoretical AFR of 16.3:1.....no wonder the ECU freaked out. Then I reduced by 5% - theoretical 15.5:1 AFR, better but still not good enough. Finally, the 2.5% reduction yielded a modified theoretical AFR of 15.1, which qualitatively seems to be an acceptable value for to ECU. In fact, before my recent fuel map editions, I recall that the FJO would occasionally display an AFR of 15.3:1 at idle with a warmed up engine, so perhaps I am at the bleeding edge.

 

[kpond]

nsxnut, I stand corrected. Hmmmmm, I have no idea how the ss box can do this. (By the way, neither does Mark, the developer/principal at Split Second.)

Anyway, I just installed the FJO gauge and two minutes ago verified that it works. I have to button up all of the interior pieces and see if I have some time for some experiments.

Andy.... you are not changing the "fuel squirt" by changing the SS values. You are only changing MAP values which is one of the input components in the ECU's no doubt complex equation in determining the injector pulse width. I really doubt that we would be so lucky to have a 1:1 correspondence between map values and injector pulse!! (I wish, I wish, I wish!)