Hey guys, I went back to the dyno today to check on my nitrous system to make sure everything was looking ok before getting out of control with the spray...

My "plan" was to make a pull on motor, then a pull on a 100, and if all looked well, a pull on the 150 pill....

On motor the car went 524/490. Beautiful a/f curve at 13.0:1 at the tailpipe.
On the 100 shot(NOS plate jettings)the car went 615 but had a lean spike and an overall a/f curve that approached 13.1:1 at the higher revs.

I decided to change the fuel pill to the 150 pill while staying on the 100 nitrous pill. This setup, had a smaller spike, went fat(10.3:1) from4k to 5k, and then began to lean to 12.5:1 from 5,500 on to 6,300.

We then fattened the a/f on the N/A tune and somewhat stabilized the upper rev a/f to 11.7:1 nearing redline.

My isssues: the lean spike on nitrous hit, which I may be able to avoid by shortening the fuel line from the nozzle, or adding fuel to the n/a curve at that rpm. My other concern is being limited to the 100 pill, as I wanted the "ability" to spray the 150 pill if I felt froggy......

My fuel setup consists of 42lbs inj., Racetronix pump/hotwire, and stock rails. Fuel pressure does have a momentary drop when the spray hits, but immediately recovers and stays rock solid for the rest of the pull...

Should I look into fuel rails, or will that not solve my problem? I will be ordering a shorter fuel line to the noid to help with simultaneous delivering of fuel/nitrous.

Thanks for the thoughts!

Alan

 

Rails would probably help - when I switched from a FAST 90 with stock rails to a Vic Jr with big rails, I had a lot less lean spike when the nitrous comes in...

 

Thank you...The rails seem to be a toss dependant upon who you speak with, while the lines seem to be the universal "helping" factor.....

 

The real cure for your pressure drop and resulting lean spike is to put the return and regulator at the rails. Our systems take a bit to realize that a new volume of flowing fuel is needed because the regulator and return are at the tank area. So, once the system pulls additional fuel off the rails, and subsequent lose of pressure/volume, system has to adjust and being so far away it takes a small amount of time. Whereas, when the reg and return are at the rails, this becomes instantaneous. Yes, sometimes a shorter fuel line will help, or running a delay. Possibly rails with larger volume may help? Something else that can help if you have a tuner program is the activation RPM for your WOT Power Enrichment fuel multiplier. I always make sure that it's activation point is a couple hundred rpm before the spray becomes active. This way your already going richer micro seconds before the spray hits. In my web is two separate fuel system upgrade write ups, much insight can be had by reading this info. Good luck and let us know how you ultimately cure this issue.
Robert

 

I Would Look To Fuel Rails Anyways With The Power Your Running, Wont Hurt. I Went To A Victor Jr And Bigger Rails Just For The Insurance That I Wont Have The Problem. Good Build Though, Let Us Know How It Works Out.

 

I am using the Vic Jr and rails also.
Robert

 

the initial "spike" is nothing to worry about, it is normal, i would be more conserned about it leaning at the higher rpm's, sounds liket the fuel system is not keeping up.tho you do say it stays rock steady pressure.

 

Robert, do you have the parts numbers for the neccessary components to switch over to the return style rail?

Thanks!

 

We recorded the fuel pressure and besides the initial hit, the gauge seemed very solid....

 

Normal, only for inadequate fuel systems, and especially wet hits pulling off the rails. Most in the industry will say that if the initial lean spike is under 1/2 second no worry. however, you have to consider there perspective on selling kits and not needing to upgrade fuel system. A proper fuel system will not have a lean spike what so ever, been there done that. So if we can have a fuel system with no lean spike, is that ideal, yes, and doable.
Robert