Lack of power from LoveFab turbo kit

CB72 · 17 August 2016

I took my LoveFab turbocharged NSX to a local tuning shop to measure it's power as I was suspecting the car was well below it's 400 rwhp target.
In fact the car pulls very well to about 5000 rpm and then the rush goes away until you reach redline.
The graph below shows exactly what's happening:
280 hp at 5000 rpm followed by a dip to then slowly rise to 330 hp at 8250 rpm.
The torque is very generous at 410 Nm at 4800 rpm.
The engine is a 3 L model with stock internals and I'm running no more than 8 PSI of boost.
Fuel is 98 Octane.
What could the issue be?
Looking at the curve, I get the feeling that the VTEC is not working?
I'll look into the manual to determine if this could be the case?

NSX%20Pito%20Engineering%20001_zpsrczduomc.jpg

I had a quick look at my AEM EMS calibration file and it looks OK to me?
The Vtec is programmed to come on at 4800 rpm and 60% TPS.

E-Nough Logic · 17 August 2016

CB72 said:
I took my LoveFab turbocharged NSX to a local tuning shop to measure it's power as I was suspecting the car was well below it's 400 rwhp target.
In fact the car pulls very well to about 5000 rpm and then the rush goes away until you reach redline.
The graph below shows exactly what's happening:
280 hp at 5000 rpm followed by a dip to then slowly rise to 330 hp at 8250 rpm.
The torque is very generous at 410 Nm at 4800 rpm.
The engine is a 3 L model with stock internals and I'm running no more than 8 PSI of boost.
Fuel is 98 Octane.
What could the issue be?
Looking at the curve, I get the feeling that the VTEC is not working?
I'll look into the manual to determine if this could be the case?

I had a quick look at my AEM EMS calibration file and it looks OK to me?
The Vtec is programmed to come on at 4800 rpm and 60% TPS.

Was the car tuned at some point prior to this and everything was much better, or is this the first tune?

CB72 · 17 August 2016

The car was tuned through a couple of emails back and forth with Cody but this was the first time I had the power measured.
It's really difficult to determine if the tune has deteriorated over time as on the street it's difficult to run more than 5000 rpm.
It's my latest track outing against a BMW M3 V8 that made me doubt I really had 400 rwhp.

blodi · 18 August 2016

My first thought as well was vtec not engaging. Just looking at your plot power is falling off when it really should start ramping up. I went through this back in my bbsc days. The AEM signal was not getting to one of the solenoids so I jumped the two vtec wires together and it made all the difference.

Jinks · 18 August 2016

Sounds like you need [MENTION=23766]@DDozier to chime in. Where has he been anyhow???

CB72 · 18 August 2016

blodi said:
My first thought as well was vtec not engaging. Just looking at your plot power is falling off when it really should start ramping up. I went through this back in my bbsc days. The AEM signal was not getting to one of the solenoids so I jumped the two vtec wires together and it made all the difference.

You are right, I'm almost sure the problem comes from the Vtec signal not getting to the spool valves.
I'll hook up my voltmeter to the spool valves to determine if they are getting any signal.
Strangely, I noted that the signal goes through the 8 prong F connector and I can't remember if I plugged it on the AEM EFI unit???
It's a pain to get at it due to the Comptech harness bar I have mounted in the car.
If I do get the signal, I'll check the oil pressure switch output on the spool valves to determine if the Vtec is engaging or not?
The good news is that when I get it fixed I'll get an extra 70 hp!

BBVNSX · 18 August 2016

CB72 said:
The good news is that when I get it fixed I'll get an extra 70 hp!

And eating BMW M3 V8 for breakfast!!! :biggrin:

CB72 · 18 August 2016

BBVNSX said:
And eating BMW M3 V8 for breakfast!!! :biggrin:

That's for sure!
I can't wait to meet the guy again on track.
I'm now almost sure this issue has been here since the beginning, the proof beeing the speed at the end of the long uphill straight at Spa Francorchamps were I could manage only 215 to 220 km/h.
A speed that the 325/340 hp Porsche Cayman's can reach.

jaffaz32 · 18 August 2016

How are intake temps cooled?

might not explain the dip but if it was down right across the higher range if you had a water to air cooler is the pump running?

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Surely if vtec wasn't kicking in the plot wouldn't drop but be consistent curve?

My understanding that vtec increases the cam profile so you may see a increase (spike) in the graph but if it wasn't working then surely the cam lift isn't changing and you would thought there be a smooth line without any spike or drop?

Making it like any other turbo car that doesn't have any form of variable cam timing etc.

If you were to install a Toda killer cam set, which gets rid of the vtec system, you wouldn't see a drop from these.

I might be wrong, but i don't get why there would be a drop if the vtec wasn't engaging.

RYU · 18 August 2016

Under the assumption that this car was tuned before and you were actually hitting the numbers you were expecting (>400wHP) then it would be useful to see the AFR and Boost curves after 5,000 RPM. If it's running super rich then we can speculate better.

...of course, this is assuming you don't have some type of "Auto-tune" enabled.

blodi · 18 August 2016

Here is my latest plot for comparison. It does level off slightly like yours but it never actually drops in power.

Dyno41215 by blodi, on Flickr

CB72 · 18 August 2016

jaffaz32 said:
How are intake temps cooled?

might not explain the dip but if it was down right across the higher range if you had a water to air cooler is the pump running?

- - - Updated - - -

Surely if vtec wasn't kicking in the plot wouldn't drop but be consistent curve?

My understanding that vtec increases the cam profile so you may see a increase (spike) in the graph but if it wasn't working then surely the cam lift isn't changing and you would thought there be a smooth line without any spike or drop?

Making it like any other turbo car that doesn't have any form of variable cam timing etc.

If you were to install a Toda killer cam set, which gets rid of the vtec system, you wouldn't see a drop from these.

I might be wrong, but i don't get why there would be a drop if the vtec wasn't engaging.

The NSX shop manual on page 5-5 shows the drop in power that should occur if only the low speed cam is in operation.
It's exactly what can be seen on my power curve.
Think of it as an Austin A40 that won't rev beyond 4000 rpm...
As for the intake temperatures, as I have a Water to Air intercooler the values don't change in a single run.

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RYU said:
Under the assumption that this car was tuned before and you were actually hitting the numbers you were expecting (>400wHP) then it would be useful to see the AFR and Boost curves after 5,000 RPM. If it's running super rich then we can speculate better.

...of course, this is assuming you don't have some type of "Auto-tune" enabled.

The engine is definitely running rich at high rpm with an AFR of 10.5 and I was suspecting this as the original cause of lack of power.
Now given the way the power drops off after the Vtec crossover point I don't want to play with the AFR until I'm sure there is no issue on the Vtec side.
Auto-tune is disabled.

RYU · 18 August 2016

I don't think it's an AFR issue quite yet. Check those VTEC solenoids. You can engage them manually at really low RPM for testing. You will notice your car will bog. Do one side at a time so help with the diagnosis. There are two wires on the left side of the ECU. I think they were yellow and white wires IIRC. This is the quick and dirty backyard mechanic way to diagnose. Good luck.

CB72 · 18 August 2016

RYU said:
I don't think it's an AFR issue quite yet. Check those VTEC solenoids. You can engage them manually at really low RPM for testing. You will notice your car will bog. Do one side at a time so help with the diagnosis. There are two wires on the left side of the ECU. I think they were yellow and white wires IIRC. This is the quick and dirty backyard mechanic way to diagnose. Good luck.

Thanks!
So far I've added a wire to one of the solenoids to measure the voltage as I drive the car into boost.
Great pleasure to get at them....

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blodi said:
Here is my latest plot for comparison. It does level off slightly like yours but it never actually drops in power.
Dyno41215 by blodi, on Flickr

Impressive!
You are in GTR Nismo category.
I'd love to drive this monster over here!

CB72 · 20 August 2016

I just came back from a test ride to check the spool valve signal.
Everything seems normal: at 4800 rpm under full load the voltmeter across the solenoid jumps to 13.9 volts.
No fun to do this on an open road as the car accelerates so fast one is obliged to take the measurement in 3rd or 4th gear to get any kind of accuracy.
Next step would be to determine if the VTEC actually engages by monitoring the oil pressure switch on the spool valve.
More fun to get access to those wires.
Why doesn't someone come up with a 4 Led device that would monitor the spool valve operation from the dashboard?

white98sh · 20 August 2016

Just a wild guess, do you have cam gears? Possible that there is too much vtec overlap and you are boosting straight into exhaust. This would be terrible for the turbo.

Sent from my iPhone using Tapatalk

CB72 · 20 August 2016

white98sh said:
Just a wild guess, do you have cam gears? Possible that there is too much vtec overlap and you are boosting straight into exhaust. This would be terrible for the turbo.

Sent from my iPhone using Tapatalk

No I don't, the engine internals are absolutely stock.
I had a quick exchange with Cody who confirmed it was a VTEC issue.
Apparently the old AEM EMS VTEC outputs do fail over time...
I'll check the other side now.

Stephen@NCAutoUSA · 20 August 2016

Have you talked to Cody about this? I'm sure he has an idea what's going on with his experience.

CB72 · 21 August 2016

Sduff@Composites said:
Have you talked to Cody about this? I'm sure he has an idea what's going on with his experience.

Yes I did as I mentionned above.
Cody confirmed it could only be a VTEC issue probably due to a faulty output from the AEM EMS.
I've tested the signal to the front cylinder bank and it's OK, now I need to check the rear bank.
Cody suggested to use a relay to feed the defective side.

CB72 · 22 August 2016

Today I tested the VTEC signal to the rear cylinder bank solenoid.
Good news or bad news? It comes on at 4800 rpm just like the other side.
The solenoids themselves have an impedance of 24 ohms so well in spec.
Now eitheir one or both of the solenoids are stuck or the electrical fault is intermittent.
Cody indicated to test the solenoids without the engine running by changing the VTEC settings on the AEM EMS to zero rpm and then depress the accelerator to trigger the TPS.
I'm getting a little worried...
Good news, I exercised the solenoids without the engine running by using the Cody method ( without forgetting to "zero" the engine load threshold) and bingo I could distincly hear the front solenoid and nothing from the rear.
It must be stuck or else the oil filter in front of the solenoid is clogged?

blodi · 22 August 2016

Totally possible that the screen is clogged or one of the seals has deteriorated. Probably worth removing and rebuilding the solenoid. Probably worth doing the front while your at it.

BBVNSX · 22 August 2016

CB72 said:
Good news, I exercised the solenoids without the engine running by using the Cody method ( without forgetting to "zero" the engine load threshold) and bingo I could distincly hear the front solenoid and nothing from the rear.
It must be stuck or else the oil filter in front of the solenoid is clogged?

I'm starting to see you mopping the floor with a certain M3 V8 ... :biggrin::biggrin::biggrin:

CB72 · 22 August 2016

blodi said:
Totally possible that the screen is clogged or one of the seals has deteriorated. Probably worth removing and rebuilding the solenoid. Probably worth doing the front while your at it.

The worst part about this issue is that the front engine bank has been "pulling" the rear bank at high rpm.
That can't be good for sure.
I believe all AEM EMS owners should plug a warning light on both solenoid pressure switches to warn them of a potential issue.
Does the OEM ECU throw a CEL warning light when this happens?
Yes it has: error codes 22 or 52

jaffaz32 · 22 August 2016

Glad to hear you are getting there...

I have a spare engine that may have the Vtec Solnoids still attached, if you want me to removed and post one to you for testing let me know.

I do know it's common for them to leak, could it be there is a bad leak? also the gasket has a gause type mesh on it, is it possible that being clogged causes a issue?

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Although they are cheap enough to buy.

http://www.ebay.com/itm/1991-1992-1...ash=item418bc62cc5:g:cKAAAOSwyjBW3nIn&vxp=mtr

CB72 · 22 August 2016

jaffaz32 said:
Glad to hear you are getting there...

I have a spare engine that may have the Vtec Solnoids still attached, if you want me to removed and post one to you for testing let me know.

I do know it's common for them to leak, could it be there is a bad leak? also the gasket has a gause type mesh on it, is it possible that being clogged causes a issue?

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Although they are cheap enough to buy.

http://www.ebay.com/itm/1991-1992-1...ash=item418bc62cc5:g:cKAAAOSwyjBW3nIn&vxp=mtr

That's very kind of you!
There also appears to be a small leak around there somewhere?
Could that be the cause?
I've ordered new gaskets to ensure everything is nice and tidy when reassembling.

Lack of power from LoveFab turbo kit

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