I am running a small dry kit (currently jetted at 75hp) and having some issues. During a pass the car will start to slightly "break up" nearing 5000rpm. After doing some searching and seeing that nozzle placement is so critical, I decided to change this first. I am now running 2 nozzles in the lid like the NOS kit, as per their instructions. However, this did not solve my problem. So I proceeded to run a fuel pressure gauge and noticed that when the car breaks up, the gauge flickers.

Note: The car has 42# injectors and has been dyno-tuned with them.

Here are my questions;

How much hp can a stock in-tank fuel pump handle? In current form my car makes 384 rwhp (off the bottle) on a dynojet.

I am running unported 243's slightly milled (.020) could this be too much Static compression for pump gas even with 4 degrees of timing being pulled?

I am running TR6 plugs gapped @ .035, is it possible this gap is too wide?

 

No one has any advice?

 

I think your right and it does sound like your stock pump just can't keep up. there is no set level that the pump isnt going to keep up, but you are in the general area that it can't. I would drop in a racetronix kit and i think that will take care of your problem.

everything else looks fine to me, good on timing and plugs

 

It sounds like you need a pump. You can pick up a walbro for less than $100 that is a direct swap to the factory in-tank pump. I would start out there and see how that goes.

 

what does flicker mean? dies the pressure drop then the car breaks up or car breaks up then the pressure drops? what was a/f and timming on motor and nitrous on the dyno and at the track?

 

Thanks for the responses!


Flicker means that the gauge went down roughly 5lbs but then returned. It seemed to happen simultaneously (breaking up, and pressure drop).

A/F on the engine is a good question. I was not present for the dyno tune and the sheet doesn't show A/F. However, when I put the car on a friends dyno the wideband showed it was perfectly flat but, the wideband on my friends dyno proved to be malfunctioning at the time. (It was reading substantially leaned than a brand new calibrated wideband) Based on the new wideband on hp the car is running roughly around 13:1 on hp. When I attempted to spray it on the dyno, It went lean.

 

whats the voltage look like when you spray? if voltage drops fp will drop and the noids will turn off then the volts will pick back up and it will happen again.

 

It has gremlins, you should sell it.

 

LOL check your pm's on efa.

 

Not quite sure on that. You make a good point. I think my next move is a hotwire kit and larger pump. Thanks!

 

If you get the Racetronix kit, it is super easy to install.

 

I'm betting a new pump & hotwire kit will solve this problem!

 

That would be where i start.

 

If it only drops 5lbs and then returns i would suspect something other than fuel pump? What about your filter? are you running a fuel pressure shut sw?

The voltage issue is an issue that is far more common than many realize. Do you have a bottle heater that may running when noids are engaged?
Robert