single turbo with stock fuel rails and 42# injectors

[AC Cobra]

got a 302 single turbo fox body that has 42# injectors, 255lph in tank pump and stock fuel lines and rails...what would be the HP that is could support?

[MY 93 GT]

If you look at my SIG thats my mods, i do have a 340 lph pump tho...Im close to 500 rwhp but im sure its close to maxing out...But ive seen guys over that easy....I dont know my duty cycle on the injectors i have to ask...LOL....i forgot....i was to excited to get the car back and drive it I forgot to ask alot of things...

[AC Cobra]

Originally Posted by MY 93 GT

If you look at my SIG thats my mods, i do have a 340 lph pump tho...Im close to 500 rwhp but im sure its close to maxing out...But ive seen guys over that easy....I dont know my duty cycle on the injectors i have to ask...LOL....i forgot....i was to excited to get the car back and drive it I forgot to ask alot of things...

So, stock fuel rails and lines with a 340 pump 500 dyno HP?

[MY 93 GT]

Originally Posted by AC Cobra

So, stock fuel rails and lines with a 340 pump 500 dyno HP?

Yes thats what i have stock lines...42 lb injectors 340 lph fuel pump..an aeromotive Adjustable fuel pressure regulator...I do run meth injection but i see guys with the same set-up not and they make 500 even seen more then that ..and yes thats to the rear wheels....

[lightblade]

With a 255 pump, 500 would be tops for sure with 42's and pushing it(injectors will likeely be almost static), maybe a tad more with bigger injectors.
Whats your base pressure and is it a static or vac/boost referenced fuel pressure regulator?
This will play a role in the flow of the pump as well.


I've been doing the walbro 405 lph pumps in the single setups I build. Just did one in a 2v fuel hat. The pump flows around 430lph at 39psi 13.5 volts. Going to be pushing this one soone looking for around 650rwhp with 80 lb injectors with it. Then maybe more with a bap later.

[Racerbox77]

My old set up was 30lbs inj, Vortech inline pump, Accel old school reg, stock lines, rails pumped up FP to around 80psi at 10psi of Vortech boost. Made 490 to the tire on a hot day. Wide band did show lean at the top end but never had an issue.

Sent from me

[millhouse]

In a foxbody, typically with a single high pressure 255 pump, 42lb injectors, stock lines and rails (and stock fuel pressure regulator) you can go up to ~ 500rwhp +/- before pushing your luck with the injector DC. There is no need for an adjustable FPR as the stock one will give you a 1:1 rise in fuel pressure with boost. They are extremely reliable and compared to aftermarkets….almost never go bad. Keep in mind that if you put an adjustable FPR on your car before taking it to a tuner…the first thing they’ll do is adjust it back down to stock levels. That’s not to say they can’t be useful, they just typically aren’t necessary if you will be running the stock lines/rails.

[alano6464]

I've researched this extensively and have seen guys making up to about 500 with a 255 and even more with the BAP. Maybe around 600.

I would just be careful when you get into that range because that seems to be where the lines and rails start to become a restriction.

[chevyguy15]

ive made 600+ rwhp with stock lines but a walbro in tank and a bosch 044 inline

[ManicMike]

Originally Posted by millhouse

In a foxbody, typically with a single high pressure 255 pump, 42lb injectors, stock lines and rails (and stock fuel pressure regulator) you can go up to ~ 500rwhp +/- before pushing your luck with the injector DC. There is no need for an adjustable FPR as the stock one will give you a 1:1 rise in fuel pressure with boost. They are extremely reliable and compared to aftermarkets….almost never go bad. Keep in mind that if you put an adjustable FPR on your car before taking it to a tuner…the first thing they’ll do is adjust it back down to stock levels. That’s not to say they can’t be useful, they just typically aren’t necessary if you will be running the stock lines/rails.

Totally agree. I have a 255lph, 42's and stock everything else. My DC is only 70% or so. I'm running 11psi too. Car is actually on the rich side still.

[AC Cobra]

Originally Posted by ManicMike

Totally agree. I have a 255lph, 42's and stock everything else. My DC is only 70% or so. I'm running 11psi too. Car is actually on the rich side still.

OK guys...what is "DC" talking about injectors?

[ManicMike]

Originally Posted by AC Cobra

OK guys...what is "DC" talking about injectors?

Duty Cycle.

[nasty92lx]

The percentage of on, or open time.

[millhouse]

Originally Posted by ManicMike

Duty Cycle.

This...

Originally Posted by nasty92lx

The percentage of on, or open time.

And this.

Keep in mind, once your injectors reach 100% duty cycle...that is all they've got (they are open 100% of the time and are at their max capacity for the set fuel pressure). The only way to provide more fuel is to raise the fuel pressure, which will require a complete re-tune or an FPU (rising rate fuel pressure regulator above 1:1).

[AC Cobra]

Originally Posted by ManicMike

Duty Cycle.

DUH !

[AC Cobra]

here is my situation...purchased this car with the understanding it was tuned and ready to go with 500 rwhp...well, dyno'ed the car, got 360 rwhp at 5300 rpm's it was going real lean at this rpm, dyno guy stopped the pull...the cars set-up: stock fuel rails and line, 225lph pump with 42# injectors, holley intake, e cam iron gt40 heads. Did find a few issues with this cars set up. #1. waste gate was not functioning...10# spring, but boosting to 16...pinched WG diaphram. #2. BOV leaking vac/pressure (cheap'o chinnezz unit). #3. fuel pressure per the gauge was not increasing with boost. #4. O2 sensors are not used in the tune. #5. injectors are at 100% per the dyno guy. #6. the car is running rich, ie black exhaust pipe.

Being a newbee to all this turbo fox 5.0...not sure what the next step should be...without spending a bunch of money! soooooo, as I writing this I think the next step is to determine why the fuel pressure is not rising with boost.

[millhouse]

Originally Posted by AC Cobra

here is my situation...purchased this car with the understanding it was tuned and ready to go with 500 rwhp...well, dyno'ed the car, got 360 rwhp at 5300 rpm's it was going real lean at this rpm, dyno guy stopped the pull...the cars set-up: stock fuel rails and line, 225lph pump with 42# injectors, holley intake, e cam iron gt40 heads. Did find a few issues with this cars set up. #1. waste gate was not functioning...10# spring, but boosting to 16...pinched WG diaphram. #2. BOV leaking vac/pressure (cheap'o chinnezz unit). #3. fuel pressure per the gauge was not increasing with boost. #4. O2 sensors are not used in the tune. #5. injectors are at 100% per the dyno guy. #6. the car is running rich, ie black exhaust pipe.

Being a newbee to all this turbo fox 5.0...not sure what the next step should be...without spending a bunch of money! soooooo, as I writing this I think the next step is to determine why the fuel pressure is not rising with boost.

Yes, the two main things you need to take care of would be the fuel pressure regulator and wastegate.

FYI, under wide open throttle, the 02 sensors are disabeled (open loop). During most other times, they should be enabled and functioning. Some tuners force all-time open loop operation disabling the ECU’s adaptive strategy. While this is not desirable, it typically does work. Your car just won’t have the ability to tune around environmental conditions (elevation changes, temperature changes etc.).

[Mustangmichael]

Originally Posted by millhouse

Yes, the two main things you need to take care of would be the fuel pressure regulator and wastegate.

FYI, under wide open throttle, the 02 sensors are disabeled (open loop). During most other times, they should be enabled and functioning. Some tuners force all-time open loop operation disabling the ECU’s adaptive strategy. While this is not desirable, it typically does work. Your car just won’t have the ability to tune around environmental conditions (elevation changes, temperature changes etc.).

Your car will still adapt with O2's or not. Remember they are narrow band O2's and most of the time with modified exhaust(turbo, longtubes, etc,) their functionality creates more issues with idle and part throttle surges than they help. It will adapt for altitude with the BAP sensor, heat with the MAF and IAT, and coolant temps with the CTS. The 02's are just one small component of a big equation. If all the tables are scaled correctly, the engine will respond correctly regardless. O2's are a nice back up in case there are small variations in a/f that they can address.

On another note, your tuner is getting DC figures from what means?

If he is commanding more DC by adding air to the MAF transfer function, then yes, the DC will increase dramatically, but if the injector opens and only 40 psi or less is passed through it into a pressurized atmosphere(boost), the relative pressure the engine sees is 40 psi - your boost pressure. In your case with roughly 15 psi at 40 psi, you are seeing 25 psi flowing through your injector, and with him trying to band aid that situation by increasing DC, then yeah, it will go to 100% quickly. Does this mean you need larger injectors NO! It means fix all the issues, get the fuel pressure to increase with boost 1:1 and you will be surprised at how pig rich your combo is up top, and as he pulls maf kg of air out, your DC will come down on your injectors. Another issue with turbo cars in foxes is some computers go ape#### when the torque/load jumps through the roof at a low rpm, which can screw the pooch for the tune. I've fought them before.
BBK actually makes a AFPR that is not boost referenced, make sure you don't have that one on your car. As said above, the stockers cannot be beat.

[Mustangmichael]

Oh and to answer the OP's original question, on a dynojet 224XLC, I got 538 rwhp on an S trim, 42 lb injectors, suck through ProM 80, stock sn rails and lines, GSS340 in tank, no sign of leaness at all, even at 6k rpm's. Car is still running perfectly a year later. Stock rails and lines will flow alot of power before they become a restriction, but my estimate is 550+ before you see signs of that. jmho.

[millhouse]

Originally Posted by Mustangmichael

Your car will still adapt with O2's or not. Remember they are narrow band O2's and most of the time with modified exhaust(turbo, longtubes, etc,) their functionality creates more issues with idle and part throttle surges than they help. It will adapt for altitude with the BAP sensor, heat with the MAF and IAT, and coolant temps with the CTS. The 02's are just one small component of a big equation. If all the tables are scaled correctly, the engine will respond correctly regardless. O2's are a nice back up in case there are small variations in a/f that they can address.

On another note, your tuner is getting DC figures from what means?

If he is commanding more DC by adding air to the MAF transfer function, then yes, the DC will increase dramatically, but if the injector opens and only 40 psi or less is passed through it into a pressurized atmosphere(boost), the relative pressure the engine sees is 40 psi - your boost pressure. In your case with roughly 15 psi at 40 psi, you are seeing 25 psi flowing through your injector, and with him trying to band aid that situation by increasing DC, then yeah, it will go to 100% quickly. Does this mean you need larger injectors NO! It means fix all the issues, get the fuel pressure to increase with boost 1:1 and you will be surprised at how pig rich your combo is up top, and as he pulls maf kg of air out, your DC will come down on your injectors. Another issue with turbo cars in foxes is some computers go ape#### when the torque/load jumps through the roof at a low rpm, which can screw the pooch for the tune. I've fought them before.
BBK actually makes a AFPR that is not boost referenced, make sure you don't have that one on your car. As said above, the stockers cannot be beat.

Yeah, I don't know what I was thinking. Correction for everything else will still take place. Long term fuel trims however will be affected with 02's disabled.

[AC Cobra]

Guys...thanks for all the great feedback.

mustangmichel..."Another issue with turbo cars in foxes is some computers go ape#### when the torque/load jumps through the roof at a low rpm, which can screw the pooch for the tune." can you define this a little bit more? and any reason why this happens? Can you change the EEC and it goes away? what should a tuner look for?

[Mustangmichael]

Originally Posted by millhouse

Yeah, I don't know what I was thinking. Correction for everything else will still take place. Long term fuel trims however will be affected with 02's disabled.

Agreed!! LTFT will be affected, which in a turbo/supercharged application can be a good thing, especially if one looses it's mind and starts showing lean or rich, which could lead to catastrophic results. And it's always the tuner's fault, even when it's a year down the road. lol.

[Mustangmichael]

By scaling a few tables you can work around it. Get your fuel issues worked out first, then take care of the next challenge. Don't make the mistake of addressing too many issues and possibilities at once. that gets you into a hole that hard to get back up out of.

[JTsStang]

Want some opinions on my setup, How far will 39's will go with 55psi rail pressure, twin gt40 pumps, and on a 6cyl? I have sd 60's here but to lazy to swap them out right now and tune them. Think it might support a 6.99sec 1/8th mile pass with 110/93 mixed 60/40?

[AC Cobra]

Originally Posted by Mustangmichael

By scaling a few tables you can work around it. Get your fuel issues worked out first, then take care of the next challenge. Don't make the mistake of addressing too many issues and possibilities at once. that gets you into a hole that hard to get back up out of.

Okeydoekey....

Just checked the fuel pressure...40 psi with vacuum, 38 psi vented to air, 10 psi of compressed air...50 psi on gauge....so it seems like the regulator is working! On the dyno at boost the gauge showed no signs of increased pressure? guess the leaking BOV was was causing the problem?

do the pressures sound correct?

[Project Ron Burgundy]

are you running a mass air meter? my stock one with the single turbo was only good to right about 340hp on the dyno. swapped out with a 90mm Ford Lightning one and with 42# injectors, a 255 pump and stock rails and lines running 10 pounds of boost on the stock block we made 441hp and 555 torque at the rear tires. We are close to maxing out the 90mm MAF, but the car makes plenty of power with the stock rails and lines right now. And we are using the stock ECU for now til the 363 goes in.

[Raptor Jr]

I have stock fuel rails, lines, 255 pump with turbo 450-500hp no problem.

[AC Cobra]

Originally Posted by Project Ron Burgundy

are you running a mass air meter? my stock one with the single turbo was only good to right about 340hp on the dyno. swapped out with a 90mm Ford Lightning one and with 42# injectors, a 255 pump and stock rails and lines running 10 pounds of boost on the stock block we made 441hp and 555 torque at the rear tires. We are close to maxing out the 90mm MAF, but the car makes plenty of power with the stock rails and lines right now. And we are using the stock ECU for now til the 363 goes in.

yep, running a 3 inch ProM unit.

[Mustangmichael]

Originally Posted by AC Cobra

Okeydoekey....

Just checked the fuel pressure...40 psi with vacuum, 38 psi vented to air, 10 psi of compressed air...50 psi on gauge....so it seems like the regulator is working! On the dyno at boost the gauge showed no signs of increased pressure? guess the leaking BOV was was causing the problem?

do the pressures sound correct?

No, they don't. With vacuum on, the pressure should be lower than with vacuum off. Think about it, when you put boost to it, the pressure should rise, right? So when you put vacuum to it (the absence of pressure), the fuel pressure should lower. They way it SHOULD be is around 32 to 35 with vacuum line connected, then remove the vacuum line and the pressure should jump up to your static setting of 40.(static means absence of vacuum or pressure outside of atmospheric pressure). So something is amiss with your setup. The increase in pressure with 10 psi applied to the regulator is correct for a 1:1 regulator.
Your leak at your BOV could have been the culprit, or you could have a fuel pump that is not up to the task of the amount of power your car is making, thus the fuel pressure fails to raise with boost as the pump just can't keep up with demand.
Hope that helps a bit.

[AC Cobra]

Michael...that does make sense, the increase in pressure did not make sense to me, I'll check it again. and post the values.

just a note: the number posted were at an engine idle and manually adjusting the vacuum/pressure to the fuel regulator. I can not veiw the gauge during driving conditions.

[Mustangmichael]

Driving conditions don't come into play. Idle is where you adjust and check your vacuum/static settings. When you take it to the dyno, the pressure should raise with boost at a ratio of 1:1, meaning for every 1 lb of boost, your fuel pressure should raise 1 lb as well above static. So if your static pressure is 40 psi, it may show 34 at idle, but at WOT it will go to 40, then as boost raises, say to 8 psi of pressure, the fuel pressure should read 48 psi. Whatever total boost pressure seen is, add that to your static fuel pressure and that should be your total fuel pressure at peak boost.
My 600 rwhp car had 40 psi static, had 34 at idle, and at 13 psi peak boost, I had 53 psi of fuel pressure showing on my dyno graph. Just as it should have been.

[AC Cobra]

OK...checked pressures again. 40 psi w/o vacuum, 35-36 with vacuum on, 12 psi on regulator 52 psi fuel pressure. I guess I had a brain fart? looks like all is good on the fuel pressure side with no load. drove the car, BOV is working, wastegate seems to be working...but it's holding at 12 psi with a 10# spring? its a 38mm tial unit, not sure why, but I think I'm going to be trying a 8# or 6# spring.

Any trick to record/monitor fuel pressure under boost?

[Mustangmichael]

Just have a gauge where you can see it. Run a length of braided -3 line up to a large fuel pressure gauge and tuck it under a wiper. I have a sensor on my dyno I can use to monitor fuel pressure, or I have a guage like I mentioned that I picked up at a swap meet years ago, and I just use it for verifying pressures.

[AC Cobra]

Originally Posted by Mustangmichael

Just have a gauge where you can see it. Run a length of braided -3 line up to a large fuel pressure gauge and tuck it under a wiper. I have a sensor on my dyno I can use to monitor fuel pressure, or I have a guage like I mentioned that I picked up at a swap meet years ago, and I just use it for verifying pressures.

ordered parts from summit be here today. 3AN fitting, hose, gauge, and cup...hopefully fuel pressure will follow boost presure, now that I have my vacuum/pressure leak fixed!

[Mustangmichael]

I would think so. I hope this fixes your issue so you can move on. Good luck with it!