I have a walbro 255lph pump but it seems to not provide my 38lb injectors with enough fuel at higher RPM causing them to work to 99% duty cycle. Does this sound logical. I have an 8# ATI 600b on my 95' LT1. Procharger swears the 38# Lucas injectors I have will do the trick. We can't seem it tune the car past 4400 rpms. Injectors are spent. Keep adding fuel values but she goes lean on us.

Need to know what everyone else is running that works. Inline, or in tank? Brand, and where to get? I know there are 2 versions of the walbro255 so I'm told and I don't believe mine is the "high output". I'm at a loss here and need some advice. Thought about going bigger injectors but the pump is cheaper place to start.

Thanks guys

Adam

 

What fuel pressure are your running? Are you running an FMU?

 

No FMU...running max of 55psi with full boost then it falls back to mid 40's indicating lack of pressure? I'm guessing at this point...can't seem to get this badboy tuned. Like I said she goes lean up top regardless of how much fuel we tell the pcm to add. Injectors are going to 2.3mls I believe, could be wrong but I know its indicating 99% duty cycle.

Adam

 

Get the racetronix intank setup. You can add a boost-a-pump to get more volumn out of it if needed. Just having a 255 lph pump on stock wiring isn't going to cut it. The SIngle intank pump with the wiring harness will work up to 550 RWHP. With a boost-a-pump Rich Krause had his over 700 RWHP on stock lines. You need more injector and more pump. Racetronix kit is under $300 and they have pretty good deals on injectors too. I went with the Twin intank 255's for my setup with 42# injectors on stock lines and regulator. I pretty much max the injectors at the HP in my sig.

 

Ok I'm following you on this. So the racetronix in-tank will also get me new wiring then? I might be able to sneak by without the boost-a-pump. But your saying the 38lb injectors won't cut it? I did quite a bit of research on putting a supercharger on the car and don't remember this much of an upgrade for the fuel system being done with similiar 8# applications. I could be wrong however. At this point I've overspent by "budget" so want to buy only whats necessary. Thanks for the input. Where is the best place to purchase the racetronix kit.

EDIT: Just went to racetronix site. Looks like there 255lph is a "high pressure" unit and the better wiring will help to keep pressure/volume high. Is this correct? Can anyone varify that this is the GSS340 pump and not what I believe I have now, the "regular output" pump. At first I didn't understand but now the voltage and fact that its a "high pressure" pump unlike mine makes sense.

Other suggestions are welcomed ..

Adam

 

The Racetronix unit is based on a modified GSS340 which is rated for higher pressure than the base 255LPH pump.

 

Yes not an off the shelf 340.

 

In our group a few people are using racetronix pump kits. I have a twin intank that with 57 pound injectors I still havn't run out of fuel at over 570 rwhp (have run out of supercharger, s trim) .My brother in law is using same injectors with a d1 at 15 pounds single ractronix pump and he is just running out of fuel at 600 rwhp.

John Carpico

 

what HP range are you seeing right now when she goes lean? and one last thing to maybe consider.. are you absolutely sure that you have 38lb injectors and who makes them and what part number is stamped on them? I know GM has 28lb injectors, but i have not heard of 38lber's at least not often enough for me to have remembered them.. are they accel units?

Chris

 

If the pump is running out of volume (not injector DC maxing) he can add a pump booster to the Racetronix harness as a simple PnP option. The MSD unit is recommended for FI applications.

 

Delphi makes a full range of injectors most of which are listed for sale on our web page.

37's: http://www.racetronix.com/621037.html

 

She's making 322 at the wheels when it goes lean. Full boost of 8lbs and yes they are verified 38lb lucas injectors. I just purchased the racetronix pump kit and harness this morning Hopefully we get it back on the dyno this tuesday to see what happens.

Adam

 

Is it true that the injectors will max out triing to provide fuel if the pump isn't keeping up. They are going 99% duty cycle when it goes lean on me at about 4400 rpm. I just bought your racetronix 340walbro pump kit with harness in hoes to provide the injectors with enough fuel. A friend of mine supported a 460hp LS1 on these same injectors so It leads me to believe the pump I have isn't keeping up. Did I do the right thing buy buying the new pump and kit?

Adam

 

A LS1 runs at 58PSI so the same size injectors will supply apx. 15-18 more fuel than an LT1. The LT1 comes with 24# injectors where most LS1's come with 28# injectors (28# operating at 58PSI = 32.3#). The LS1 cars have fuel lines which flow slightly better as well. LS1 motors are far more efficient than LT1 motors. Regardless you can not compare a LT1 to a LS1 as they are totally different animals.

The Racetronix system will support apx. 550RWHP safely. If you are having fueling issues it is most likely due to undersized injectors. You should be running a fuel pressure gauge in your car to monitor the system. You can not guess at this.

 

If your running lean on 38 lb injectors at only 322rwhp.. something else is wrong!!!!!

i have made 410 rwhp on stock pump, stock 28lb lt4 injectors, and fuel was still around 12.8 : 1 on a wide band at 6700 RPM and although the injectors were very close to 85% duty cycle, it is far above what your seeing at 4400 RPM. you should still have plenty of injector left where she is going lean. is there an inline pump on here as well? this sounds like a bad inline i once had that would shut the motor down at about 5k rpm.. it was fried and I was unaware until the first time i took it out and romped on it and it fell on its face at 5k.

you should not be anywhere near 99% at that power and RPM. If it were me, before I started throwing parts at it, I would identify exactly what is going on there.

Anyone else agree?

Chris