+1 for the ECM tune. Specially if you tried almost everything on the nitrous system side.

 

Reguardless of having a battery charger hooked up I would like to see a different alternator installed just for testing. Last nitrous gremlins I chased came back to the alternator acting up.

How long is the car really taking to get above 4500rpms? It can't be anytime at all. I would adjust jetting for the final afr and not the afr you are hitting under light or no load at the beginning of the pull. That wideband isn't telling you crap straight from the hit until all flows have gotten going through the engine.

 

One thing I'm not seeing mentioned here is fuel volume. Have you flowed the pump without running the engine? Pressure means nothing if you don't have volume. Put a standalone on the car and report back to us. You can make a redneck standalone with a 5 vallon bucket fuel line hose and a return style regulator. Instead of trying to plumb a whole standalone in.

 

if the line is that short the motor should bog on fuel first. I don't care anything about the tune, you just eliminated it.


Heres something else, turn the bottle off, arm kit and make a pull. If it takes a second and a half as you say for the fuel to make the motor cough rich. You have a physical flow issue.

 

Having a traditional needle sweep gauge only gets you so far. This is a transient event. You need a fuel pressure sender with an analog output voltage that you can log. Think of it the same as trying to see a transient voltage spike with an rms multimeter.

If the narrowbands are showing the momentary lean state then I tend the believe it. Also it would likely show on the plugs if you killed the car right when it went lean, but you said it goes rich at the end of the pull masking the lean condition.

Personally I would not let the car go back to the customer if they plan to spray at all, otherwise have them sign a waiver lol.

 

Being lean can't hurt a nitrous motor, timing does.

But thats a whole nother argument

 

See what this does. Are you running a 255 or 340 pump. It's been about 4 years ago but we had 3 bad 255hp pump with in 6 months an never a problem before or after. Is the car a auto or m6? If it a stalled auto see what it does on the street. Is it a brand new kit or used? Is there a nitrous filter anywhere, how about a filter on the inlet fitting on the nitrous noid. Good luck, I know how much this can suck especially if you did the install and sold the kit.

 

Depends how lean we're talking, but yes too much timing is bad, hence why I asked how he was pulling timing on the spray

 

On a 150 shot there should be no doctoring of anything in order to make it work. I have pulled 300 off the rail on numerous cars without having to cheat anything. There is something being over looked, plan and simple. Do you have anyone who can look at the car? Sometimes working on a problem over and over you may just need a fresh set of eyes on it. I know it can get really frustrating sometimes finding an odd problem.

 

I wonder if its CLOSED LOOP at the times giving you the lean problems?
Someone previously might have hacked at the % TPS to go OL.

 

I appreciate all the tips guys. I have the car tuned for open loop all the time. I don't like to do this on a street car, but it has a set of really long headers and it just drives like crap below 2000 rpms with the camshaft because the trims fluctuate so much... I've tuned ol with a wideband and it drives great, turn on closed loop and you can feel the trims make the car have a bit of surge at cruising rpm. I've played with the cl integrator delay and idle without much luck. So trims aren't affecting it.

The AFR naturally aspirated is right on the money and it comes in right away....All the other nitrous cars I've seen/tuned the afr doesn't do this. Yes, they usually have a very brief lean spike then the fuel goes right where it should. That isn't the case with this car.

I have used the fuel pressure gauge I used to test this on multiple cars with fuel volume/pressure issues. A weak pump usually shows up right away in the injector pulse width. More fuel would be demanded at 6500 rpms than at 3500, however we're more than rich enough at that point. I have threw a .033 jet in with a .052 nitrous (100 nitrous, 150 fuel) in it and it will go mid to high 10:1 range at the top. I don't see volume as the issue, it just seems like the fuel solenoid doesn't open as fast as the nitrous one. Even properly jetted on the 100 shot the problem is identical.

I wish that a fresh set of eyes could fix this! We have 4 techs at the shop and nobody has been able to fix this. I have changed everything including the wiring so I'm not sure what anyone else would be able to see.

I'll hit it tomorrow with the bottle off just to see how long it takes for the fuel to bog the engine....but even if it did have a bit of a delay I'm not sure what I would do to fix it. The solenoid has been changed. I can pull an alt off of another vette and try that as well but the voltage on the log is fine. A voltage issue should affect the nitrous side I would think since that noid has about 3 times the current draw in comparison to the fuel. either way it is something else to try.

I have already thought about having the customer sign a waiver stating that the nitrous tune is not safe and to use it at their own risk. However, I'm sure we can command the afr in the tune between 3500-4500 rpms to be a point richer or so with very little change to the numbers it makes on motor anyway. Not something I want to do, but if it comes to it that may be what we have to do.

 

Put the correct fuel jet in. What about a window switch to delay the nitrous to 3500ish rpms.

Also with the nitrous timing enabled why not make the power enrichment come on quicker?

 

Anyone ever sprayed nitrous dry and used the "adder vs IAT" table to provide the additional fuel? With enough fuel injector that would seem to be an alternative since I'm always at a locked IAT when the nitrous sprays anyway due to the timing IAT relay.

Of course I'd have to change the tune for the injectors and sell the customer injectors.... And I'm not sure how low I'd have to command the afr to actually achieve what I'm shooting for.

Just thinking outside the box since nothing normal seems to fix this.... Atleast there wouldn't be fuel flowing through an intake that was never designed for fuel to flow through it.

 

I have had the correct fuel jet in it. Regardless of the fuel jet, the car has the same lean condition on the hit. The car does have a window switch and it is set at 3500 rpms. The dyno graph I posted in the begging shows the on and off points of the nitrous and that graph had the correct jetting for a 150 shot.

One would thing that a richer fuel jet would richen it everywhere, but it doesn't richen the lean area one bit....just richens it up after 4500 rpms or so. I've even sprayed it by flipping the switch at 5000 rpms and it still had the same amount of time lean, it just wasn't quite as lean.

I'm not sure I follow you on making the PE come on quicker. I have the PE delay set to zero and the enrichment ramp in set to 1.5. PE commanded afr comes in immediately as soon as the car meets all of the requirements and its in as soon as the car is wot. And the fuel is where it should be on motor from 2000 rpms on up till 3500 when the nitrous hits... PE has been active and steady for over 1000 rpms before the nitous even sprays.

 

I've never given much thought to a lean spike at the hit outside of this thread. Not enough time ever spen under load to think of it as anything more than sensors not catching up.

I know it's totally different when you are a business tuning someone elses car so my suggestions are just thinking outloud.

 

Latest NA pull vs. 100 shot and super short fuel line from noid to plate:

 

Thats the best way to do Dry nitrous IMO

 

Same graph vs. time in seconds. From the hit the car is stupid lean for 1.5 seconds. For whatever reason, the fuel looks good on this wideband after it comes in, but on the NGK wideband it reads about 1 full point richer by the end of the run

 

Have you looked at using EFI Live's COS5? Real good stuff for spark/fuel control and OL fueling.

I wonder if any of these might be useful:

1. Delay box for nitrous solenoid, allowing fuel to come on first. I know the MSD goes down to 1/10 second for activation.

2. Use a two stage nitrous controller, like the NOS Mini. On one channel bring the fuel in at an earlier RPM?

 

You can use custom operating system with efi live and have the o2's off at idle and turn on after x rpm and still run CL. With the custom os you can also fine tune fuel on nitrous and have PCM pull timing without having to cheat iat or any other sensors .