Im running the GT3076R turbo kit with 750cc rc injectors with an agp return line. I have AGP race fmic, 4 inch intake, and 3 inch exhaust turbo back. You just want the number on the top of my ecu?
Im running the GT3076R turbo kit with 750cc rc injectors with an agp return line. I have AGP race fmic, 4 inch intake, and 3 inch exhaust turbo back. You just want the number on the top of my ecu?
Do you have the regulator hooked up as a rising rate? What a/f ratio is it giving you when it stumbles? What static fuel pressure do you have set? Personally I think the 750cc injector is too big, but there is no reason why you should not be able to get it to run good with it. We are all assuming you have 3 bar sensors in the car.
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Im running the GT3076R turbo kit with 750cc rc injectors with an agp return line. I have AGP race fmic, 4 inch intake, and 3 inch exhaust turbo back. You just want the number on the top of my ecu?
Hesitation is common in the 2000 to 2500 rpm range when you run too low a fuel pressure.
I will assume your running a Vacuum/Boost line to your regulator.
All of the computer calculations are done at 58 psi.
When your regulator sees vacuum it lowers pressure enough to cause a hesitation.
I don't know what your tuner has done for you but this would be very difficult to adjust for in the tune.
I suggest you remove the vacuum/boost referance line and or change it to a boost only line and test it.
im not sure about how its hooked up and the pressure on the guage i believe reads 60 but i do know the regulator is hooked into the vacuum line. And do i need the 3 bar sensors or no cause dodge told me the other day when i got my clutch in that i may need to get performance sensors or somem like that
Last edited by sorrellsjm : 06-17-2008 at 10:16 AM.
I would unhook the reference on the regulator and not bother to hook it back up. Of course you will need to retune your fuel curve. There is no reason why you should need the extra fuel from the regulator with that size injector. Rising rate regulators are a way to get more fuel when you're running out of injector. I seriously doubt, no I am certain you have more than enough fuel to tune that car on pump gas without it. I have stage II injectors in my car at 21psi and have no need for any additional fuel. Same turbo same exahust, I do have the bottle neck fix in mine though.
I know that you guys are sizing your injectors based on an 80% duty cycle and the number lands around 750, There is no reason why you cannot run your injectors out to a 90-95% duty cycle. Thats targeting a 420hp number.... one you likely will not attain on pump fuel.. By sizing the injector so large for a peak number (like 525hp) that you feasibly COULD attain with race fuel, you're giving up spray pattern at the lower revs. Then your solution is to reduce the fuel pressure, thats why so many of you guys have all these drivability problems... Now grated we can tune all this out of your car, but how many of you have had their car tuned by a reputable shop? None, let me give you some good practical advise. Choose an injector that makes appropriate sense to the way you will be using your car. Unless you have a race car that sits in your driveway with a tank full of 104 octane fuel, you don't need these massive injectors. These cars are good for about 400hp MAX on the factory shortblock and pump gas, choose an injector that will perform well for how the car gets used 90% of the time... Not an injector that works well 10% of the time. Not to mention the fact that you can keep those 750's in your tool box and put them in when you're going to run race fuel. It's two bolts and 4 connectors and a PCM flash, 15 minutes. You will save hundreds on your gas bill and have a car that will run like stock.
As stated, you CAN get the car to run good with the 750's, but why do through all this trouble? Put a set of Stage II injectors in the car and I will email you a flash that will turn key make your car run like stock and make 390hp. It's just like the rednecks that come into the shop all the time with a 350cid chevy V8 with twin 750cfm double pumper dual quads on the thing. That engine needs about a 650cfm vacume secondary, and about one THIRD the amount of camshaft, then they tell you your dyno is broken with the car makes about 175hp.
Choose a fuel system appropriate to the way the car will be used.
Rising rate regulators should see boost only, not boost and vac, they will work backwards REDUCING fuel pressure by the amount of VAC they see. Your just adding a whole lot of work that can be avoided by adding VAC into the equation.
So even on race fuel and a rising rate regulator you have enough fuel to tune the car with a much more practical state II injector. And if you DON"T have enough fuel? Buy a 2:1 regulator instead of a 1:1
525hp
4 injectors
.65 BFC
95% DC
108psi FP (*edit this number should have been 158psi not 108psi b/c 25 psi boost X 2 (2:1 regulator) = 158pis)
= 495cc injectors
You see where this is going? Even when we only had piggybacks 750's never made practical sense, 50 trim guys were running 35psi in fuel pressure to try to get some fuel out of the lower RPM's. A 2:1 Rising rate regulator is a whole HELL of alot cheaper than a set of 750cc injectors and is going to require about a 10th of the amount of tune work to boot.
Where did the concept of using 750cc injectors come from? I'll tell you where, from they guys who SELL 750cc injectors.
BTW, why do you think Chrysler used 58psi as a static fuel pressure? Because the LOWEST fuel pressure an injector should be flowing is 42psi, take 16psi away from 58 and you just answered the question. It's to conserve a proper injector spray pattern.
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