My CTSC is leaning out at 7,300 RPM

[charleysung]

I have a whipple standard boost CTSC on my 2004 NSX. I did not install an AEM or other engine management unit.

I just had the car dyno'd, and the a/f ratio was fine up until about 7,300 RPM, then leaned out.

My tuner called Comptech, and they recommended that I install their new management unit that they developed for their autorotor unit. Including the harness, it will cost me about $700.

My tuner doesn't think I need to install that unit because I don't track the car, and frankly, how often will I hit 7,300 RPM? And if I do hit it, it will likely be in first or second gear and it will only be for a second or two, not enough to overheat the engine.

Any opinions?

 

[nsxotic911]

UMMM.... how lean is it? My gut answer is, you should fix any lean condition you detect, yesterday, rather than today.

Do a search and see how many engines have blown up due to the likely cause of detonation and unless you're itching to shell out 10 - 30K.. any solution < 5K sounds like a good deal to me.

I'd do whatever it takes to mitigate the risk to it's lowest point... I like my AEM, though it has drawback. Comtech FMU I'm sure is very good as well.

 

[Elite]

You should definitely be taking care of any lean conditions in your tune. The rational you are taking is going to lead you to a blown motor for sure. You will end up with the same result as many others have had with FI and a bad tune or hot intake air temps.

A Walbro 255 hp fuel pump could be your answer. We had a similar issue with a CTSC a few years ago and the addition of this pump brought the air/fuels to where they should be. Should be able to get one for right around $100.

 

[J-RnsxT]

A Walbro 255 hp fuel pump could be your answer. We had a similar issue with a CTSC a few years ago and the addition of this pump brought the air/fuels to where they should be. Should be able to get one for right around $100.

i would also invest on engine management, fuel regulator and bigger injectors on top of what elite say...

 

[LJSB]

I have a whipple standard boost CTSC on my 2004 NSX. I did not install an AEM or other engine management unit.

I just had the car dyno'd, and the a/f ratio was fine up until about 7,300 RPM, then leaned out.

My tuner called Comptech, and they recommended that I install their new management unit that they developed for their autorotor unit. Including the harness, it will cost me about $700.

My tuner doesn't think I need to install that unit because I don't track the car, and frankly, how often will I hit 7,300 RPM? And if I do hit it, it will likely be in first or second gear and it will only be for a second or two, not enough to overheat the engine.

Any opinions?

Yes. I have a opinion.

You schedule and take you car to your tuner for a dyno session to see how your car is running.

Having done that you review the data and find it is sometimes running lean.

You had your tuner call Comptech and share the details of the data from your dyno session and you have a answer from the CTSC experts, Comptech.

Having done this, your tuner decides you don't need to heed their advice.

Now you're asking here, people you may or may not know or be able to verify their expertise and, who I assume, have not had the benefit of reviewing the technical specifics(ie., the dyno results) for advice.

I mean no offense Charley, but my opinion is that you are a smart, conscientious person who doesn't mind or may even enjoy wasting his time.

 

[Lonestranger]

What he said!!!:wink: Remember, $700 won't hardly pay to pull the dead engine out, the next time you are merging on the freeway and decide to "taste the wine" a little!!!:biggrin:

Yes. I have a opinion.

You schedule and take you car to your tuner for a dyno session to see how your car is running.

Having done that you review the data and find it is sometimes running lean.

You had your tuner call Comptech and share the details of the data from your dyno session and you have a answer from the CTSC experts, Comptech.

Having done this, your tuner decides you don't need to heed their advice.

Now you're asking here, people you may or may not know or be able to verify their expertise and, who I assume, have not had the benefit of reviewing the technical specifics(ie., the dyno results) for advice.

I mean no offense Charley, but my opinion is that you are a smart, conscientious person who doesn't mind or may even enjoy wasting his time.

 

[Onsoku]

+1

Yes. I have a opinion.

You schedule and take you car to your tuner for a dyno session to see how your car is running.

Having done that you review the data and find it is sometimes running lean.

You had your tuner call Comptech and share the details of the data from your dyno session and you have a answer from the CTSC experts, Comptech.

Having done this, your tuner decides you don't need to heed their advice.

Now you're asking here, people you may or may not know or be able to verify their expertise and, who I assume, have not had the benefit of reviewing the technical specifics(ie., the dyno results) for advice.

I mean no offense Charley, but my opinion is that you are a smart, conscientious person who doesn't mind or may even enjoy wasting his time.

 

[C-speed]

You can always adjust the FMU to raise the fuel pressure a bit. It'll richen it up everywhere below 7300, but you can at least get rid of the lean condition from 7300+. Of course, you'd need to do this on the dyno. Screw the top adjustment allen bolt IN to raise the FP, out to lower.

 

[Elite]

You can always adjust the FMU to raise the fuel pressure a bit. It'll richen it up everywhere below 7300, but you can at least get rid of the lean condition from 7300+. Of course, you'd need to do this on the dyno. Screw the top adjustment allen bolt IN to raise the FP, out to lower.

Maybe my memory is failing me, but I don't think the CTSC runs an FMU?

 

[C-speed]

I would believe that it does... I tuned one personally on the dyno. Its hooked up to the fuel return line and usually mounted on the rear firewall between the trunk and engine bay. Its a large cylindrical aluminum unit with 2 fuel lines (in/out) running to it - probably 4-5" in diameter.

Here's a pic. Red one on the left:

<img src="http://www.synapseengineering.com/synchronicsize1.jpg">

 

[charleysung]

I would believe that it does... I tuned one personally on the dyno. Its hooked up to the fuel return line and usually mounted on the rear firewall between the trunk and engine bay. Its a large cylindrical aluminum unit with 2 fuel lines (in/out) running to it - probably 4-5" in diameter.

Here's a pic. Red one on the left:

<img src="http://www.synapseengineering.com/synchronicsize1.jpg">

That red unit is Comptech's rising rate fuel pressure regulator.

 

[C-speed]

That red unit is Comptech's rising rate fuel pressure regulator.

Which is exactly what I'm talking about. FMU = RR FPR... one in the same You can make minor fuel adjustments to adjusting the screw at the top. Its not a fixed rising rate like Vortech's, etc which are set to 8:1, 10:1, 12:1, etc etc.

 

[powerneedy]

your telling me that comptech is charging 10k for a SC unit that still uses a fmu? when you can get a jrsc for a honda for 2200 bucks new for a very close product. yes smaller sc but... please tell me this isnt true

 

[C-speed]

your telling me that comptech is charging 10k for a SC unit that still uses a fmu? when you can get a jrsc for a honda for 2200 bucks new for a very close product. yes smaller sc but... please tell me this isnt true

Comptech uses the FMU but they also have a little piggy back unit that you have to splice into the ECU wiring. I'm sure that unit reads boost and retards the timing. However, you cannot change the parameters on the unit. You CAN adjust the FMU though.

If you think about it, any boosted application that still uses the stock injectors will almost definately require some sort of FMU/RR FPR. Otherwise there is no way stock injectors (even with a raised duty cycle) will flow enough fuel for the added air supply.

$10k for an NSX SC = supply vs demand

 

[Onsoku]

your telling me that comptech is charging 10k for a SC unit that still uses a fmu? when you can get a jrsc for a honda for 2200 bucks new for a very close product. yes smaller sc but... please tell me this isnt true

Also, CT had to pay for the smog cert process on every ECU change that occurred during the NSX production. If memory serves me right, I think it was 8-10 changes...gaining exemption status is not cheap, and low volumes of NSX owners, and even less that will do power mods.

Comptech's setup is the only NSX FI solution that is 50 state smog legal...

 

[ScienceofSpeed]

A little more information is needed before drawing a conclusion. Namely, what are the ratios earlier in the RPM band and what is considered lean. The Comptech's FMU can be adjusted so that the entire baseline fuel curves can be decreased or increased. It's a little bit of a compromise, however, the setups usually are a little rich on the bottom and become optimal on the top. If your curve now is optimal on the bottom but lean on top, you can increase the baseline fuel pressure to satisfy the fuel demands.

That being said...

You should monitor the fuel pressure during the pull. If you are not having fuel delivery problems, the rate of fuel pressure gauge vs. boost should be linear (approximately 10 psi of fuel for every 1 psi of manifold pressure). If the rate of gain tapers off at the top, in my experience, you are probably having a fuel delivery problem. The factory fuel pump becomes less effective at higher line pressures (as does every pump) and a pump better suited to the job is required. Walbro makes a "255lph" that is designed for high pressure applications. We stock this pump and the fitting kit.

The Comptech fuel controller is also a good idea which will increase injector pulse width on the top reducing how much pressure is required to satisfy fuel demand.

Cheers,
-- Chris