Dyno trouble.

MetalSpikeRacing

MetalSpikeRacing

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20 March 2009
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Toronto/Cancun
:mad:
Well, seems like nothing can go right for me.
Last night I got the car to the dyno finally, we strap the car down , and Marco at Magnus got to work.
I was most worrie about start up and with AEM little did I know what I had coming.

Marco's work start coming trough, one crank start and idle perfect!!!
Then he start doing advance tuning, First pull boost goes trough the roof @15 PSi!!! With the AEM Tru-boost off, so the Marco ask me what size spring was in the wastegate and I respond 3psi, then he ask me to run the compressor straight to the gate and bypass the controller, so I did.

Does another run, and we have 10.3psi with a wastegate controlled boost that is only running a 3psi spring.

Finally Marco comes out of the car, goes underneath the car and this is how the conversation went:

Marco:what da fak is this and why is like this???

Me:what???

Marco: the wastegate desing is running the wrong way!!! And it not releasing boost efficiently .

Marco: let me explain this way, exhaust need something like a highway off-ramp not a hairpin where it actually has to even turn around!!!!

Me: but there....

Marco: ya ya ya, there is 20 kits out there and this has never happened... Well it's happening now. Plus the pipes for the wastegate are to small in diameter for this wastegate .

Me: Fack.

I understand that there is all of you guys running this kit with this desing and has had no trouble, I think upgrading my wastegate to a precision unit has brought up the problem stated above.

The Y-pipe will be coming out tonigh, I'll mock up where the wastegate should come out and hopefully be back on the dyno on Saturday .

This is our theory, I will let you know guys if that fixed the problem, btw wastegate is working just fine.

If you have an idea of why this may be happening I would like to hear it.

Here is what Marco is talking about.
 

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did you have the lines ran correctly to the wastegate? the pressure line should be ran to the middle air fitting on the wastegate. the top should be vented to the atmosphere .
 
I used same ypipe but with Tial 46mm External Wastegate and I have no problem with the boost spike
 
While the wastegate placement is not as optimal as "the book" says, it does work perfectly fine as the great majority of 30+ kit owners (me included) have shown, not only this, but most of them are running low boost (5-6 PSI) which further proves that the wastegate placement can easily provide enough flow (the lower the boost, the more exhaust needs to flow out of the wastegate port) The wastegate is placed like it is to allow it to fit cleanly in th space allowed, but believe me, if it had presented a problem in teh last 5 years, I would have changed it.

If you look at factory designs, they frequently differ from what is considered theoretically optimal in order to package the components as needed.

I SERIOUSLY doubt that changing the wastegate location will fix the problem, if it were a matter of the wastegate not flowing enough, you'd have boost creep, not just a boost level that was too high - i.e. the 3 psi spring you have would give you 3 psi until higher RPMS where your boost would start to climb or "creep".

Take a look at the spring and confirm is is the 3psi spring you think it is. Even better, take the spring out and see how much boost you have, maybe 1-2psi...
 
Yes the fittings on the wastegate are correct, I am actually running the middle wastegate fitting straight to the compressor .ei boost off the wastegate spring.

I will trouble shoot this tonight before taking anything apart .

Thank you guys for the trouble shooting coments.

-MSR
 
Here's a hint. If I fill up a balloon with air to build up pressure. Then I poke that balloon with a straw to relieve that pressure, does it matter on the orientation of that straw?
 
Vega$ NSX said:
Here's a hint. If I fill up a balloon with air to build up pressure. Then I poke that balloon with a straw to relieve that pressure, does it matter on the orientation of that straw?
Click to expand...


Ya... I don't think that example applies in this situation, since we are talking about exhaust flow. Flow being the key word, since it's being bounced around instead of being prioritize . It's very easy to see that being the problem .

But anyways , I am off work and on my way to my garage to trouble shoot this problem.

-MST
 
I'm going to guess you have a sticking wastegate, diaphragm is ruptured or top port is blocked, leaky or clogged hose leading to the wastegate, or 8+ psi spring.

I've seen all sorts of bad WG placements, and they still function just fine at these low boost settings.
 
7 psi spring and max boost around 5.5 to 6 psi cause I used the line from compessor straight to the wastegate. Should get 7psi if I connected wastegate to intake madifold
 
MetalSpikeRacing said:
Ya... I don't think that example applies in this situation, since we are talking about exhaust flow. Flow being the key word, since it's being bounced around instead of being prioritize . It's very easy to see that being the problem .

But anyways , I am off work and on my way to my garage to trouble shoot this problem.

-MST
Click to expand...

You are talking about the difference between static and dynamic pressure. I guess the key issue is when should the blow off valve open when static pressure is x amount or when dynamic pressure is x amount. I am not a tuning expert but maybe that's the thing to focus in on...maybe it doesn't matter, I am not a tuning expert by any means.
 
The reason that you are having the problem and no one else is is because you are running that bad dog gt4088. When you actually go to a quality turbo like the gt4088 they require correct waste gate placement or they will over boost. It is all about flow when it comes to waste gates not exhaust pressure. Trying to make the exhaust do a u turn will never properly divert enough exhaust gases away from the turbo. The exhaust will flow to the path with least resistance
 
Ok, so seems like I found the problem.
And like Aaron @ precision said "it's always something stupid".
Did you guys know that the precision wastegate comes with three ports? One at the top and two on the middle.
Well I just found out, while all of my lines were run properly to the boost controller, the secondary port on the midle was open, Aaron told me that that usually comes pluged, I never reliesed it was not.

So I plugged it and seems to be working fine.
I do have a 3psi spring it and with Tru-boost at 90% duty(Maxed) I get 6.75psi.

I will change the spring today to a 6psi and attemp for the tonight.

In end:
Is the wastegate placement on most optimal spot?, no.
Does it work?, seems like it.
Do I feel dumb?, a little bit.

I'll update as soon as I am done at the dyno.

-MSR
 
MetalSpikeRacing said:
Ya... I don't think that example applies in this situation, since we are talking about exhaust flow. Flow being the key word, since it's being bounced around instead of being prioritize . It's very easy to see that being the problem .

But anyways , I am off work and on my way to my garage to trouble shoot this problem.

-MST
Click to expand...

Here's a hint #2: I'm a mechanical engineer and I know what I'm talking about.

It's a very common mis-conception for people to visualize flow as a rat going down a maze or particles moving down tube. They think that when the rat or particles hit a dead end, it stops all of their momentum because they have to turn around and move back in a different direction. This is because non-technical people often have to compare a system into more everyday examples to help them visualize what is happening; often to incorrect assumptions or conclusions (search the airplane on a treadmill thread).

There are two pressures at play here: a static pressure and dynamic pressure (sometimes called a velocity pressure). Static pressure is like the pressure in a balloon or say an oxygen tank. It’s pressure built up because the air is highly compressed because the walls of the “vessel” are pushing back. Velocity pressure is the pressure generated by the movement of the air, like a fan or hair dryer pushing air in your face (or a pinwheel/windmill).

In this particular case, you have both pressures, static and dynamic. However, the static pressure is far greater than the dynamic pressure. How your system is actually building pressure is by building static pressure. You have exhaust gasses exiting from your engine. The actual velocity of the exhaust isn’t terribly fast, so the velocity pressure isn’t very high either. What’s happening is that your turbo and piping is acting like a balloon. If you break it down, you are adding more gasses/pressure than you are releasing, so it “inflates” that balloon and builds pressure. That is why you need to use pretty stout metal piping for your charge piping, because you need the walls of the piping to act as a pressure vessel. Otherwise, if all you cared about was velocity pressure, you could use some plastic tubes and put it into pinwheel or windmill shaped fan blade. And if you think about it some more, all a blow off valve or wastegate does is open up a valve so that you exhaust more gas than you are adding so it releases the pressure (like a straw poking a hole in the balloon). Notice, velocity has no part in this equation, that’s because it doesn’t. There is a minuscule amount of dynamic/velocity pressure there, and so a smoother transition will always help minimize the velocity pressure loss, but it doesn’t even come close to cover the pressure differential you are experiencing. And your wastegate or BOV isn’t going to care or see that velocity pressure because all it is designed to do is relieve static pressure. That also explains why you can get minimal gains by smoothing out your exhaust piping in an N/A engine, but in a turbo, all those bends and curves really don’t matter as much because it uses static pressure. Changing your piping and relocating the wastegate will have negligible effects and not resolve your issue.
 
MetalSpikeRacing said:
Ok, so seems like I found the problem.
And like Aaron @ precision said "it's always something stupid".
Did you guys know that the precision wastegate comes with three ports? One at the top and two on the middle.
Well I just found out, while all of my lines were run properly to the boost controller, the secondary port on the midle was open, Aaron told me that that usually comes pluged, I never reliesed it was not.

So I plugged it and seems to be working fine.
I do have a 3psi spring it and with Tru-boost at 90% duty(Maxed) I get 6.75psi.

I will change the spring today to a 6psi and attemp for the tonight.

In end:
Is the wastegate placement on most optimal spot?, no.
Does it work?, seems like it.
Do I feel dumb?, a little bit.

I'll update as soon as I am done at the dyno.

-MSR
Click to expand...

As I mention in both of my posts, the position/location of the wastegate would have nothing to do with the problem you were seeing.

Glad you were able to fix your problem, but I hope you just don't walk away from this and wipe your hands clean like most people do, but instead take the time to really understand the dynamics of how a turbo system works and builds pressure and the function of a wastegate and how it relieves pressure (as I explain in my post above). It will allow you to debunk silly theories as to wastegate placement, velocity/static pressures and actually back up why.
 
Last edited:
Vega$ NSX said:
Here's a hint #2: I'm a mechanical engineer and I know what I'm talking about.

It's a very common mis-conception for people to visualize flow as a rat going down a maze or particles moving down tube. They think that when the rat or particles hit a dead end, it stops all of their momentum because they have to turn around and move back in a different direction. This is because non-technical people often have to compare a system into more everyday examples to help them visualize what is happening; often to incorrect assumptions or conclusions (search the airplane on a treadmill thread).

There are two pressures at play here: a static pressure and dynamic pressure (sometimes called a velocity pressure). Static pressure is like the pressure in a balloon or say an oxygen tank. It’s pressure built up because the air is highly compressed because the walls of the “vessel” are pushing back. Velocity pressure is the pressure generated by the movement of the air, like a fan or hair dryer pushing air in your face (or a pinwheel/windmill).

In this particular case, you have both pressures, static and dynamic. However, the static pressure is far greater than the dynamic pressure. How your system is actually building pressure is by building static pressure. You have exhaust gasses exiting from your engine. The actual velocity of the exhaust isn’t terribly fast, so the velocity pressure isn’t very high either. What’s happening is that your turbo and piping is acting like a balloon. If you break it down, you are adding more gasses/pressure than you are releasing, so it “inflates” that balloon and builds pressure. That is why you need to use pretty stout metal piping for your charge piping, because you need the walls of the piping to act as a pressure vessel. Otherwise, if all you cared about was velocity pressure, you could use some plastic tubes and put it into pinwheel or windmill shaped fan blade. And if you think about it some more, all a blow off valve or wastegate does is open up a valve so that you exhaust more gas than you are adding so it releases the pressure (like a straw poking a hole in the balloon). Notice, velocity has no part in this equation, that’s because it doesn’t. There is a minuscule amount of dynamic/velocity pressure there, and so a smoother transition will always help minimize the velocity pressure loss, but it doesn’t even come close to cover the pressure differential you are experiencing. And your wastegate or BOV isn’t going to care or see that velocity pressure because all it is designed to do is relieve static pressure. That also explains why you can get minimal gains by smoothing out your exhaust piping in an N/A engine, but in a turbo, all those bends and curves really don’t matter as much because it uses static pressure. Changing your piping and relocating the wastegate will have negligible effects and not resolve your issue.
Click to expand...



This theory sound really good in the shower or on paper. I have dealt with this problem for years with real testing on the dyno. If this system had a much smaller turbo on it he would be fine but because the gt40 is so efficient when the compressor spins it generates so much air that you will have an over boost if those exhaust gassed can not escape efficiently. You are not releasing pressure "TIP-Turbine inlet Pressure" as so much you releasing actual volume of exhaust gases. If this was a much smaller turbo that was running the "TIP" very high then waste gate placement would not matter much because then you would releasing the actual exhaust pressure from the system.

With the size of waste gate that metal spike is running he should have no problem running that turbo at the 3lb spring level with a properly placed waste gate. Although I would not recommend running this turbo at that low of psi because this turbo will surge. Run this turbo at a minimum of 8psi and you should be ok

Not trying to step on your toes vegas just letting everyone know what I have seen through out my career of tuning
 
Im not trying to be an ass here... but I crack up laughing when I here gt40r and 3 lb WG spring in the same sentance.

Your problem is incorrectturbosizingitus

The location of the wg can be better.. it's not the problem though.

your using a turbo that is designed to make 30-40 lbs of boost... trying to restrict a turbo that size at 3 lbs is not something I would ever try to do.

my .02
 
Really? You really think a 40R in v6 engine is too much when the goal is to only run 8-10 psi in the end? Hence the reason of running a 3psi spring.

The 40R is very linear on the V6 engine for a track car, even at such a low psi it generate great power. but you already know that, and thats another topic.




StmpoRaceProducts said:
Im not trying to be an ass here... but I crack up laughing when I here gt40r and 3 lb WG spring in the same sentance.

Your problem is incorrectturbosizingitus

The location of the wg can be better.. it's not the problem though.

your using a turbo that is designed to make 30-40 lbs of boost... trying to restrict a turbo that size at 3 lbs is not something I would ever try to do.

my .02
Click to expand...
 
Last edited:
Hey Vegas, thanks for hint #2.
I think I grasp the idea better now.
And no , I never walked away from anything, and I'm always willing to learn.


Thanks,

-MSR

Vega$ NSX said:
As I mention in both of my posts, the position/location of the wastegate would have nothing to do with the problem you were seeing.

Glad you were able to fix your problem, but I hope you just don't walk away from this and wipe your hands clean like most people do, but instead take the time to really understand the dynamics of how a turbo system works and builds pressure and the function of a wastegate and how it relieves pressure (as I explain in my post above). It will allow you to debunk silly theories as to wastegate placement, velocity/static pressures and actually back up why.
Click to expand...
 
MetalSpikeRacing said:
Really? You really think a 40R in v6 engine is too much when the goal is to only run 8-10 psi in the end? Hence the reason of running a 3psi spring.

The 40R is very linear on the V6 engine for a track car, even at such a low psi it generate great power. but you already know that, and thats another topic.
Click to expand...

The 40r is used on the drag strip way more than it is used on a track

This V6 redlines at 8k…. you can’t just use the fact it’s a v6 when sizing a turbo

without doing the math... at 8k on a c30 with a 40r... your looking at 36-40 lbs of pressure being generated... if your aiming at 8-10 lbs... you have 28-32 lbs leaving through your WG...

this is why turbo sizing is your problem...

I would contact hybrdthry911 for more insight… I have a short fuse when it comes to this and I hate seeing people spend tons of cash on mistakes

Here is the thread with his explanations and flow charts

http://www.nsxprime.com/forums/showthread.php?t=144743&highlight=turbo+sizing

Here is the turbo sizing research he did from that tread… we use the gt3076r as well.. and if it were avaiable at the time.. we would have used the gtx3076r... but the difference would be fractional


hybrdthry911 said:
The 40r can barely make 700whp but spools up like your typical 67mm billet wheeled unit capable of 900+whp. I've never liked this turbocharger, and if you look at garrett's compressor maps the gt3582r can outflow the 40r. All the new 62mm billet wheeled units(gtx3582r, hta3586, & precision 6262) spool up as fast as the 40r or faster and can make 750-800+whp. Although a better choice than a gt4088r even those seem like overkill for meager 400-450whp goals.

Kookoo touched on a great subject a smaller turbo is often pushed harder to meet the same power goals because the turbos dont flow as much air as a larger turbo at the same boost level. When pushed harder the midrange torque increases while the top end wont see as much of an increase in torque.

I rarely use these but i have a couple comp maps here to illustrate what im trying to say, keep in mind these arent using exact numbers but just gives you an idea on why a turbocharger that can make 400whp might not work well on an NSX:

I am assuming a 15% driveline loss of power to get 400whp so 475hp at the crank for the calculations which requires ~47 lb/min of air. i also used 130 degree intake air temps which i think would be on the higher end of what you can expect, and a 98% VE. Shown below is a compressor map for a gt3076r with a few select points. the Red line shows the air requirements of the NSX engine at 10psi(i was conservative i think the NSX can easily reach 400whp at ~8psi with a quality setup), and the green line shows the engines air requirements at 12.5psi(the minimum boost required to make 400whp on this turbocharger per the comp map). As you can see on the red line at 10psi and 8000rpm the turbocharger cant supply enough air to meet the NSX's engine demand. This means you will see torque drop off and you wont be able to make 400whp at 10psi. In an attempt to make 400whp one would try to increase the boost to lets say 12.5psi and try to attain 400whp. Unfortunately when boost is increased airflow through the entire engine increases. So when looking at the green line you can see at 3000rpm and 5000rpm the engine is now getting more air(lb/min) which means more torque and more stress on the motor to achieve the power we want. With our new found boost we will achieve our goal of 400whp at ~7400rpm and torque will then start to drop and our HP will likely maintain 400whp because the turbocharger cant supply any more air. It would seem the gt3076r might be too small for this particular application.

400whpgt3076rcomp.jpg


Now looking at the new GTX 3076r this looks like it will meet our goals of 400whp without having to push a higher boost level, it should supply the necessary 47lb/min required for the NSX engine at 10psi. Unfortunately when you want to achieve greater power from this unit it might not be the ideal turbocharger though because it wont be able to feed the 3.0L engine in the upper rpms. This would likely be the fastest spooling turbocharger you can use without putting additional stress on the motor to acheive 400whp.
GTX3076R400whp-600whp.jpg


IMO what might be the most well rounded turbo for the NSX on applications form 400-600whp seems to be the gt3582r. It seems to be able to feed the engine all the way to 8000rpm and beyond
gt3582r400whp-600whp.jpg



just some food for thought.
Click to expand...

hybrdthry911 said:
The whole point of my post is that you wont have to push these turbochargers(with the exception of the gt3076r) in the midrange to make the power levels you want. This means you will have around the same torque at say 4000rpm as you will at 6000-8000rpm. It will of course fluctuate as the VE of the motor changes through RPMS, and as you pass through the most efficient points of the turbocharger, this will happen on a larger turbo as well. It wont be a huge spike in the midrange though because you won't need to push a higher boost level to reach your goals. If you were breaking traction at 6000rpm though, you will break it at 4000rpm now yes.

About the 35r vs 40r i never noticed this until just now so i was skeptical at first as well. As you can see they are very close in the lower boost levels, and then the 35r starts to shine once above 2.5bar. I think the compressor map for the 4088r isnt as complete as the 35r and might show some more left at higher boost levels, but it would be hard to argue they arent almost on top of each other. Obviously the 4094r outflows both by a considerable amount i wasnt talking about that one.

714568-allcomp_e.gif


751470-allcomp_e.jpg
Click to expand...
 

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