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Discussion Starter #1
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?
 

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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...:rofl:
 

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Discussion Starter #3
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...:rofl:
So, stock fuel rails and lines with a 340 pump 500 dyno HP?
 

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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....
 

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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.





 

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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
 

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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.
 

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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.
 

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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.
 

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The percentage of on, or open time.
 

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Duty Cycle.
This...

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).
 

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Discussion Starter #16 (Edited)
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.
 

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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.).
 

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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.
 

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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.
 

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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.
 
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