my01corvette

okay 2001 C5 only mods are Slp loudmouth catback, cold air intake and cooler plugs with MSD Wires. Running a NX Proton Kit


First dyno run air/fuel was 12.8 air/fuel and made 340 rear wheel N/A
next run right after the first run the air/fuel was 13.4 and sprayed a 50 shot > the air/fuel remained 13.4 through the whole run but saw a gain of 90 Rear wheel horse! 430 rear wheel Hp!

so my question is what is the stock air/fuel ratio on a C5? and does it normally change when the car warms up? Also has anyone seen this kind of Rear wheel HP gain on a 50 shot?? I called NX and they said as long as the air/fuel stayed the same the whole run then it sounds like my car is hitting perfectly and exceding the 50 shot pills expectations. he did think the 13.4 was a little lean for the nitrous. so if this is a common air/fuel for a c5 should be okay on the sauce??

we tried this 3 times and all three the first run air/fuel was around 12.8 and then the next run would goto 13.4-13.8
common or not???

Thanks Guys

gotjuice?

Need to richen it up on the juice. What jets?

my01corvette

It is 35 N2O and 20 Fuel which is what the card said for a 50 shot. We did goto a 23 fuel jet which fatten it up but it took a few seconds of spraying to watch the air/fuel fatten up or thats the delay for it to show on the dyno.

So was the crazy HP gain due to the air/fuel ratio? And is that air/fuel common for a stock C5? 12.8 first run 13.3-13.5 second?

reactor2

13.4 is a little lean for sure. Not sure if you risk any engine damage at that power level but if you bring it back to 12.8ish you should pick up a little more power.

I do have an NOS kit on my vehicle but I haven't used it for years and never on a dyno but it sounds like numbers I would expect from a 100hp shot, not a 50 shot.

my01corvette

Yes but the pills we used said a 50 shot so maybe the air/fuel ratio made more HP??

Why does my air/fuel ratio go up to 13.4-13.6 after the first run? Is this common on a corvette??

MVP'S ZO6

What do you mean go up after the run? As in go up when you let off the throttle?

my01corvette

How I should have stated it is:

The first dyno run my air/fuel is 12:8
Then when the car is warmer the second run the air/fuel leans to 13:3-13:6 the third run is 13:3-13:6 also

Is this a common thing in a C5? So they like to run at that ratio after warming up?And if so sould I just use a large fuel jet then the NX chart advises to compensate?
Thanks Guys

JoeyG

Air/fuel ratio should be consistent for all NA runs. How many miles on the car and fuel pump? New fuel filter? Fuel pressure staying constant on the dyno? Pulling fuel off the rail?

LSOHOLIC

Call me old school....but there is know way in hell I'm trusting an a/f ratio as a benchmark.
Read your plug, it's in the chamber. Matter of fact there is one in each chamber to show you the worst cylinder effected by distribution. Then dial your tune up based on the worst cylinder.
Then...and only then......once the tune up is dialed via the plug. Take note of the a/f ratio, now you have a reference to base the a/f ratio off of.

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BLOWNBLUEZ06

I don't do that on the dyno. It's not the same as the track. Not the same load as the street or track and not for as long. I would set it up fat and safe and get plug readings at the track or wherever the car's going to be run. If you're going to run it 1/2 mile, dial it in at the 1/2 mile or conservatively at a 1/4mi track.

LSOHOLIC

I can see your logic Bret.
But if the dyno "lies", it will lie on a plug or an a/f meter (I'd still rather read the plug). Now grated we are just talking about a small hit, but it's a poor practice to get "comfortable" with. Because we all up the hit sooner or later.

But I do not have much experience with spraying on the dyno (for the very reasons you mentioned). We typically dial the n/a tune then hit the track. Make some small n/a adjustments within a run or two. Then make all the n2o hits at the track.
(edit****and this is why this tends to be a late model/tuner phenomenon)

I still stand by my comment of letting the plug "set" the benchmark for the afr.

But I do respect your wisdom Bret......you've been around the block a time or two.
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my01corvette

I have always tested my cars on the dyno before the street. Just makes me feel safer seeing the numbers first. I get the plug reading and I may have to go that route. I don't intend to take it down the track it really was just a small shot to play on the street but want it to be safe. So I was just curious what others C5's stock air/fuel was so I would know if I'm starting off the same as most.

Sigforty

What are you using to pull timing? The jets often recommended in the kits are close, but fine tuning on a dyno is always best. Have you watched your fuel pressure? There is typically always a lean spike and it gets worse if you tap the stock fuel system.

As for the talk about plug reading, most people make the mistake of driving on the plugs after the run. That will distort the readings.

my01corvette

I am using the Diablo Intune to pull timing or add fuel.
We added 2% fuel at WOT and got the air/fuel to 12:4 on the first dyno run but again on the second run when the car was warmer it went back to 13:4 both runs NA so not sure if it was a C5 thing?

I did tap the fuel line to goto the fuel solenoid using the test point on the rail. This effects the air/fuel?? Even NA when not in use? That what the directions said to do on the kit.

Thanks guys

my01corvette

Also I put the car back to the stock tune because adding the fuel had me loss about 12hp and it seems the car just wants to run at 13:3-13-6 once warmed up anyway. That's why I was asking if that's a common number in a C5

Sigforty

You make fueling adjustments with the nitrous through changing the jet sizes in the plate or nozzle. You only use a tuner to correct the timing. You should tune your car for optimal power using NA setup first. Then you will need to save that tune. For nitrous, you need a second tune or a device to pull the timing when nitrous is activated.

I do not know much about the diablo tuning device, but most of us here use HP Tuners or EFI Live. There are so many tables and variables, I am not sure the Diablo can adjust everything. That is probably why it keeps changing on you.

where did you put the nitrous nozzle at?

LSOHOLIC

I agree with most of what you said. The N/A tune has to be dialed before you start adding an oxidizer to the mix. Or you will never truly dial in the hit.

But about making fuel adjust on the n2o setup. Traditionally all your small adjustments are made with fuel pressure. And when the adjustment is to large for the pressure to "fix", then you step your pill up or down depending on what the plug is telling you.

Most kits today don't come with tons of jets. They typically come with "matched" pairs of the desired hp hit your wanting. So adjustments will need to be made with fuel pressure (or you could call your vendor and request more jets).

Also, as you were saying about adjusting timing. Like you said, I lock my N/A tune and make all my timing adjustments with a MSD timing twister. Which is all external, no laptop or handheld required.


Good luck OP....

Sigforty

Unless he puts in a regulator there is no way to adjust fuel pressure when feeding off the stock fuel system. So jet changes will be his only real option other than installing a stand alone.

LSOHOLIC

Yep....and I run a low pressure system. And have very little rail experience. But if it were mine, I'd run a regular off the rail. It's just another way to be more accurate with the tune up.

Looking at the chart.....looks like one fuel jet size is roughly 9psi on the high pressure system....give or take.

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Sigforty

I am with you. I run a stand alone on my car and have it at around 6 PSI. Fuel pressure is what I did my change with.