I had my car dyno'd with the spray today and my A/F spiked lean at 3000rpms right when the nitrous hit and then droped down right around 4000-4500rpms.

The car also had a pretty nice smoke cloud that came out as I let off the thottle. I know a little smoke comes out of my car as I hammer the throttle.........as most higher HP cars do, but I thought smoke from the deceleration was kind of odd. I attached a video so you can try to help me make heads or tails of it!

Dyno pull:
http://s33.photobucket.com/albums/d5...rrent=Jon1.flv

Dyno Graph:
http://i33.photobucket.com/albums/d5...e/DSC04321.jpg

Close up of A/F:
http://i33.photobucket.com/albums/d5...e/DSC04325.jpg

 

Just curious Jon, have you done anything with your fuel system? I am shooting for 500 RWHP have a racetronics on the way before I do do it, I know your a bit more modded than I am. Are you logging anything like Fuel Pressure? I know on the stock Pump NA I lose 6-10 psi (regular pressure is 60, drops to 52 or so), a Big hit (your doing 200 -250 right) will probably lose alot of pressure w/ a stock pump.

Beer

 

Take it for what it is worth but an incomplete combustion can cause the exhaust to appear lean but in reality it could be full of unburnt gas and oxygen. Since only the o2 is being read, you will get low volts from the sensor. The smokey cloud you mention sort of supports a moment of being very rich rather than lean. However, if you are monitoring a lot of knock that coincides with the lean reading then your first impression is correct.

 

I had the same problem with mine on the dyno mine spiked to 17.1 when i shut her down real quick and i about chit my pants! But i upped the fuel jet and my tunner fattened it up in the 2800-4000 rpm band and it fixed it after a couple of tweaks down to 12.5 on the spike . which is close and alot safer on a 150 shot. I have the dyno under my sig but that is the wrong dyno sheet. that is the one before when we were still working on the fuel! I knew it wasnt a fuel problem with me i just installed the racetronix and hot wire kit! Are you still on stock pump?

 

I don't remember seeing too bad of a lean spike on our Camaro, here I will post the graph the A/F is on the bottom. We are using the Dynotune wet kit with a window switch, racetronix fuel system, and 30lb SVO injectors (not really applicable with the wet kit though).

 

That is on a 100shot? dry or wett? we are talking about a wett shot .I had no troubles with a 100wet shot on the dyno but when i went to 150 is when i had troubles.

 

I'm hitting right around a 170rwhp shot...........and I have the racetronix fuel pump too. I don't lose any fuel pressure when the nitrous hits. My fuel pressure stays between 60-65psi

 

I think his kit is a wet shot too, but I don't see any trouble in his A/F.

Look at mine. It spikes pretty hard..........

BTW guys, I have an upgraded fuel pump. Should I shorten the fuel line and lengthen the N20 line? Or is the spike to big for that to make a difference?

 

You could try the line length trick, at the least it may minimize spike. Rails and return at the reg can help. Going into PCM and adding fuel in the PE Multiplier at that rpm area can fix it, but will richen n/a up also, but does that matter to you? Changing over to a dry can eliminate lean spike alltogether, hehe.

Did you ever note fuel pressure upon activation of the spray?
Robert

 

It didnt hurt my na tune or numbers when i had to richen it up.

 

It is a 150 shot..and it is a wet kit.

EDIT: BTW, wet kit is mentioned twice in my original post.
There is a small lean spike when the nitrous sprays then our tuner had it run rich for safety as you can see the A/F run down toward 11...

 

I need to monitor my fuel pressure when the spray hits.........but usually your so focussed on the road, I don't ever think to look at it.

 

My 382 cu,in. Camaro went lean with a 300 shot at about 4200 rpm.To continue a 300 shot I will need a stand alone fuel cell even after adding a second fuel pump and and 60lb.injectors. Now 792RWHP and 835 TORQUE.

 

Jon,
What does the airfuel graph do on N/A? Is it nice and flat?

If your NA air fuel is not nice and flat it is going to be hard to get yourt nitrous air fuel nice and flat.

Do not tune the nitrous by changing fuel tables. That is not the correct way to go about it. That will change your N/A airfuel.

Since your fuel pressure is not droping fuel delivery is not a problem. Shorten the hose from the fuel solenoid to the plate by about 3-5 inches and it will tune out the lean spike. Or you can add alittle lenght to the nitrous. Shortening the fuel is the way I like to go if possible.

Dave

 

Why would changing your fuel tables in a certain rpm band hurt your na tune if it is done in small incruments? Like i said we fatened it up a little and it fixed the problem and didnt change my a/f ratio one bit or even change my hp or tq numbers on Na! I guess if you made drastic changes that wouldnt def be a good idea but small table adjustments wont hurt anything . But shortening the line is a good idea i shortened mine 4 inches so it always doesnt work!

 

I'll do that, and I haven't checked my N/A A/F in a long time. But it was good when we tuned it then.

Did you take a look at the A/F graph I attached? Seeing that A/F graph, do you think that line length change will help that big of a lean spike?

 

I did not mean it will actually hurt the tuine. But yes if changed much it should change the NA tune.

If its a small adjustment Im sure its fine.
Dave

 

Yes I think shorting the line will take care of your needs.
Dave

 

I'll be calling you soon for a new fuel line.

Thanks Dave.

 

good luck with your **** jon...Im still having issues to get my damn n20 noid fire correctly.