Hello everyone,
I have a 90 speed density 355 auto with the following mods. SLP claw CAI, power coupler, 52mm TB, ported matching plenum, port matched Eldelbrock high flow runners and intake (just had them bench flowed after porting and flowed 245cfm), APR 195 cc heads milled to 58cc, comp 1.6RR, comp cam 485 lift 265/275 duration 112 lobe separation, adjustable fuel pressure regulator, 24lb injectors, racetronix 255lph pump, MSD 6al ignition box, MSD blaster2 coil, MSD 8.5mm wires, FAST EFI system, exotic muscle long tube headers, no CATs, true duals, X pipe, corsa cat back, 354 gears and a new rebuild tranny with all the heavy duty components. Hope that's all... my heads will be here soon and the intake is off the car. I'm hoping to make around 425/450hp at the crank once put back together. My question is according to the fuel injection charts on the web I need around at least 30lb injectors to support 450 crank hp. My tuner said we can crank the fuel pressure up. From what I see if I cranked the psi up to 63psi my 24lb injectors would now produce the same amount as 30lb injectors at 43psi. Seems my pump will run 225lph at 58psi and it takes 137lph to produce 450hp so I know my pump will work fine. Its my injectors I'm worried about. Will turning up my fuel pressure tax my injectors I would like to stay around 80% duty cycle. Should I buy 30lb and stay at 46psi? Will my 24lb injectors even support 450 hp? Thanks for all replys.

 

Call Jon at fuel injection connection add is to the right

 

What is the reasoning for turning up the pressure when you can put the appropriate injector for 43 psi?

 

I think my guys trying to save me some money or maybe he believes that there is no need to buy different injectors because the 24ls are capable. I have read that the L98s with the fast system like the fuel psi turned up to at least 48psi. I have not messed with the fuel rate yet thought. He has a dyno and I would like to mess with the fuel pressure and base timing. My thing is I don't want to keep taking the TPI system off, if I need new injectors then great if my 24s will work even better. I would just like to get some different options. I have read that some times bigger is not always better when it comes to the injectors.

 

Spend all that money on everything else and skimp on the injectors? Doesn't sound like a plan to me. Why would the FAST system care about the fuel pressure? Supposedly people have speculated that it atomizes it finer. Not sure if anyone has proved it conclusively that it helps.

I checked Jon's site and according to the calculations, you will need 39pph injectors. I know you said 450 is max. I'd rather err on the side of caution and go 500.

Why are you looking to mess with timing and fuel pressure? I thought the ECM can adjust the advance and pulse width for you?

What I read is that if the injector is too large, it might not work well for idle situations when the pulse width required is too small for it to adjust properly.

I am doing 420RWHP and running 42pph @ 43psi if it helps

 

[QUOTE=aklim;1591634129]Spend all that money on everything else and skimp on the injectors? Doesn't sound like a plan to me. Why would the FAST system care about the fuel pressure? Supposedly people have speculated that it atomizes it finer. Not sure if anyone has proved it conclusively that it helps.

I checked Jon's site and according to the calculations, you will need 39pph injectors. I know you said 450 is max. I'd rather err on the side of caution and go 500.

Why are you looking to mess with timing and fuel pressure? I thought the ECM can adjust the advance and pulse width for you?

What I read is that if the injector is too large, it might not work well for idle situations when the pulse width required is too small for it to adjust properly.

I am doing 420RWHP and running 42pph @ 43psi if it helps[/QUO

I cant say for sure about the FAST system and higher fuel pressure as not many L98s are running them and posting info, its just what I've read. I'm not sure about my fuel injectors that's why I'm trying to get some info. I've read LOTs of post saying 24lbs is fine and people are making well over 400 plus whp but yet the injector carts state 24lbs only supports mid 300hp. Just trying to get info from guys who have been there done that. And base timing still has to be set, I would like to play around with that and see what the car likes and doesn't like.

 

I guess I would definitely go with what the calculators say as opposed to what someone thinks it does and give a little bit extra, just to be safe.

Why do you care about base timing? Mine used to be set at 6 and the tune was worked around it. When it was re-written and the value of 0 was used, oh well. The tune was worked around it.

 

I most likely will pick up a set of 30 to 36lb injectors I was just hoping to get some info before I blew another 300 plus dollars. Thanks for the response. Question with the mods I have do you think 425/450hp is a reasonable goal?

 

A 350 with a small cam and TPI intake will most likely be under 400 hp,
thats probably the reason your tuner is telling you to stick with the 24 lb injectors.

 

Your probably right blackocvet, I just want replace the injectors while the TPI systems off if I have to, thanks for the reply.

 

I know where your coming from, the TPI is a major PIA to work on, so if youve got it apart then do whatever else needs doing.

Keep in mind that an engine needs rpm to make horsepower, and this is the downfall of a long tube intake, it does make lots of torque to make up for it. So if your not using rpm to make horsepower then the 24 lb injectors should work with your engine setup.

 

I believe your 24 lb injectors will be fine. These are my reasons, don't shoot me for these reasons.
-I do not believe you will have 450 HP, more then likely you will be closer to 350 HP. Long tube runner engines do not support power above 5000 RPM very well and to make 450 HP on a 350 you will need to be well north of 6000 RPM.
-A 24 lb injector running at a BSFC of .4 will support 480 HP at 100% duty cycle, and yes you can run 100% duty cycle for brief periods of time. Street use and drag racing it will be fine. If you plan to run the 24 hours of Daytona then you would have to go bigger if you were running 100% duty cycle which you will not be.

 

Why would you want to set the BSFC to 0.4 and run a 100% duty cycle? I thought the number is 0.45-0.5? Using those numbers, your wanting to use 24pph injectors make sense but most of the calculators don't use that number or recommend at 100%

 

Most engines will run fine at .4 bsfc and what I am showing is that will support 480 hp. I believe his engine will make 350 which means the 24 lb injectors will be fine. Even at .5 the 24 lb injectors will support 384 hp at 43 psi and if he needs more he can add slightly more pressure.

 

Thanks for the reply's guys, are you thinking 350hp to the crank or wheels? I was shooting for 350ish to the wheels which is around 405ish to the crank with 20% drive train loss. Also how much is a little when turning up the fuel pressure?

 

I don't think the injectors care about RWHP. They have to feed X amount of fuel and that is all they do. So for measurements for the injectors, I would suggest going with crank.

If you are making 350 at the crank, if it were me, I don't personally feel comfortable at 100% duty cycle. When I went to an LPE 383 that wasn't producing more than 425 (IIRC what I was told the motor was rated for), I was advised to go with 32 pph injectors at 43 psi.

As bjankuski said, the most cars will work with the 0.4 BSFC number and you can simply send your injectors for cleaning and testing and be happy. Me personally, I don't mind spending the extra 3 or 4 hundred on the injectors and sell what I have and be done with that just so I don't have to have any doubt that my injectors are up to any miscalculations.

Give Jon at FIC a call and ask him how much his reman 32 pph injectors are and figure you spend about $22 per injector to get them cleaned and tested unless they are new or recently done and under $400 for a new set of 32pph. From there you can make your decision

 

350 at the crank, but it may be higher or lower, only one way to find out, build it and test it.

 

Good answer.

 

I just had my car dyno'ed on 8-15 and it made 275hp and 345tq to the wheels, that's 343 crank hp if you calculate 20% drivetrain loss. I just ordered my APR 195cc heads milled to 58cc (to keep the compression the same as before), a set of comp 1.6 RR and had my whole edelbrock high flow TPI system ported where it is now flowing 245cfm They should be back this weekend so im hoping to be 400 crank once re assembled.

 

D. And f. Performance flow test
date: 2/19/2016 cubic in
name: Davis gantt per cyl.
Cylinder head afr 195 sb chevy rpm range `
hp
int valve 2.05 stem 8mm length
exh valve 1.6 stem 8mm length

range 1 2 3 4 5 6
intake 34.5 71.2 149 297 446 602
exhaust 38.5 76.4 156 316 477 637
25" to 10" *.632 28" to 10" * .598
intake port
valve lift 0.1 0.2 0.3 0.4 0.5 0.55
range 3 4 4 4 4 4
50 51.5 71 86 92 92.4
@28" 74.5 152.9 210.8 255.4 273.2 274.4
head w/ flow plate


w/ manifold 49 50 66.5 75 81 82
@28" 73 148.5 197.5 222.7 240.5 243.5




exh port
valve lift 0.1 0.2 0.3 0.4 0.5 0.6
range 3 3 4 4 4 4
43 75.4 54 63 67 68
@28" 67 117.6 170.6 199 211.7 214.8