shawnk

My car was running fine but I wanted to go ahead and put in my FPR before dyno tuning in case my 550/1300 injectors weren't up to my 350rwhp goal. I converted to stainless hoses and rerouted everything including back above axle to put filter in engine bay. Tapped both sides of both rails and ran my hoses like this:

From frontmost line in the tank trio at the bottom of drivers side engine bay near firewall to filter to rear of primary to front of secondary to side inlet of FPR, capped other side inlet and then out of bottom to middle line in the tank trio.

The problem that I am having is that when I hit boost (anything above 0in) my car stumbles/hesitates terribly and I dont try any further. It idles smoothly and cruises fine. I have upgraded the fuel pump and have been running that with stock regulator for a few weeks and saw nothing like this. Since no other changes were made I am assuming that either I am not getting enough fuel or I am getting too much fuel (and flooding out the car). I do get a strong gas fume in the car when I get this hesitation and there is no leaking in the engine bay so I am assuming this is coming from the exhaust and that would support the too much fuel theory. I am running a PFC with the map that comes on it. Is this something that will be "tuned out" or is my car not ready for the dyno? I have switched out regulators and same thing. This is what I know comes into play in this system:

The fuel pump rate - it changes from low to high at some point (I have not done resistor).

Vacuum/Boost - as it changes the FPR changes fuel pressure to rails.

Fuel map - is it possible the way the first two things relate in the new system can put this map way off?

The other things that could be suspect:

I pulled the injectors when I tapped the rails - and didnt replace O rings. They are only a couple of weeks old but do they need to be replaced everytime?

The tapping/fittings are restricting - I used earls everything and 6 an hose but is it possible that removing the FPD and making these changes is causing turbulence or restrictions to high fuel flow?

I have adjusted the pressure higher on the regulator and as low as I could with keeping an idle and got the same problem.

I am going to switch out the filter (which is earls) to K&N billet this morning.

Sorry for the long post but I wanted to try and give those who reply as much info as needed.

Thanks,

Shawn

shawnk

I drove my car around today with a friend watching the PFC map trace while I tried different things. I was able to get to full boost (well the 7psi that my external wastegate is set to since I took my controller of to limit variables) without hesitation or symptoms if I did it WOT from the start. All other times I had a power drop at some point whether I slowly accelerated up or medium acceleration. I did not try this too many times because I am afraid of breaking something as fuel problems have seemed to take a lot of engines. I did notice again today very strong fumes when this stumbling would happen. I would stop immediately and stick my nose to the vent between the hood and the windshield and smell no gas what so ever so I really dont think that the fumes are coming from the engine bay. It seems to be map related because it was always around the middle of the map where the problems were. For you guys with a PFC that went from stock to aftermarket FPR did you have to retune your fuel map immediately?

Shawn

maxcooper

Hi Shawn,

My first thought -- does the PFC know about your injector sizes? If it still thinks you are running 550/850, it will get very rich when the secondaries come on line. I remember the settings for this were a little tricky, so you might want to double-check what is entered in the injector settings screen.

-Max

Wargasm

When I changed from 1300 -> 1600s and also did a FPR and so forth at the same time, I had some hesitation and bucking under part throttle acceleration. Under WOT, it was OK. I was able to tune all this out with the help of Dave/KDR.

What is your idle fuel pressure? Is your boost compensation port on your FPR hooked up on the same vacuum line as your MAP sensor? If so, move it. That jacks up your MAP sensor and makes your car run worse. The only thing on the MAP sensor hose should be the MAP sensor.

B

Dragon

did you even hook up the vaccume line to the FPR so that the fuel pressure will come up with the boost?? If you did, your fuel pressure is probably just off.. you need to get a FP Guage, summit racing sell's a cheap one for about $30... also what kind of FPR are you using..? If your running one of the FPR that the honda guys run it will increase the **** out of your FPR.. Make sure your reg does a 1:1 ratio ie. you boost 1psi and the fuel pressure goes up 1 psi.. some of the ones they sell for honda's will have a 1:2 ratio or even more. They usually have a really big diaphram in them...

shawnk

Thanks for the replies!

It is a 1:1 regulator and I have an in engine gauge on it. I have the FPR set at 40 psi at idle which is where the idle seems to do best. Any lower and it tries to stall out. I have put it as low as 30 at idle which is what it was with my stock regulator but I still have the same problem. I do have the injector size adjusted in the PFC. I also have the vacuum line hooked up on a hose by itself to the intake near the throttle body.

It sounds exactly like what wargasm saw so I have scheduled a dyno tune session for next Tuesday.

What should I tune my car to as far as a base pressure at idle? I was thinking about 36psi or so at idle (-19 inHg-850RPM). This being a little higher than stock and enough to get me to 350rwhp.

Also do you think I am hurting the engine when I get the hesitation? Should I not drive it til then? If I am flooding as I suspect are there any major problems that can cause over a couple hundred miles?

Shawn

zyounker

Yes, you can wash the oil off the housing if you are running extremly rich.. i would lay off the driving or start adding some premix to be safe..


-Zach

maxcooper

Shawn,

Disconnect the manifold reference signal (the vacuum line) from the regulator when you set the base pressure. That takes the vacuum away so you can know your true base pressure. I would set it at something like 45 psi.

-Max