Fuel Injector Question...
04-13-2007, 11:29 AM
#5
Are you sure your running rich? sometimes people think that because their eyes burn thats a rich condition when it is actually a lean condition. To be safe I would go to your local Dyno shop and pay $50-60 bucks just for a pull or two with a wideband to be sure, beats popping a head gasket..
04-13-2007, 11:57 AM
#6
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Im no expert with nitrous, but I KNOW that a dry shot gets its extra fueling via the injectors.
Being that your installing a hot-cam kit (which should be stretching the injectors a little already) and you need the injectors to supply extra fueling when spraying, Id say that you SHOULD need bigger injectors.
The mileage really has nothing to do with whether or not you need larger ones...
Talk to the nitrous kit manufacturer for an injector recommendation.
Also, you really should have it tuned for the spray, as the pcm needs to control the fueling and I doubt a stock file is up to the task.
Being that your installing a hot-cam kit (which should be stretching the injectors a little already) and you need the injectors to supply extra fueling when spraying, Id say that you SHOULD need bigger injectors.
The mileage really has nothing to do with whether or not you need larger ones...
Talk to the nitrous kit manufacturer for an injector recommendation.
Also, you really should have it tuned for the spray, as the pcm needs to control the fueling and I doubt a stock file is up to the task.
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04-13-2007, 12:07 PM
#8
Mileage matters because Injectors DO wear out like anything else, I see stock motors with high mileage and injector duty cycle hitting max limit, spraying nitrous puts a demand on the engine thus requiring the injectors to work more. If it was a low mileage car I would say it is fine, I ran a hot cam with ported head, headders ect but my car at the time only had 25.000 miles and the duty cycle went up about 2%. That is also a lot of mileage on the motor to be spraying so just beware of everything else, Tranny if its an A4..
04-13-2007, 12:10 PM
#9
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tranny is about to be rebuilt i blew up the t56 thats why im doing all this stuff why its down...but what size injectors and will any kind work like a for example a set of 33lb injectoes from and ls2 goat
04-13-2007, 07:17 PM
#10
LSX injectors are rated at MUCH higher pressure "32lbs> LSx injectors are only about 28lbs at LT1 pressure.
It would be foolish to run a dry shot on stock injectors, not because of sizing or milage or anything but rather because a dry shot injects the fuel by jacking the pressure making the injectors act much larger, not by messing with the pcm as stated above, that can be done with aftermarket management but is not the case here. The stock injectors fail closed if overpressurized which would be instant death for the motor. Other injectors like the SVOs stick OPEN if overpressurized and are capable of handling more pressure to begin with.
It would be foolish to run a dry shot on stock injectors, not because of sizing or milage or anything but rather because a dry shot injects the fuel by jacking the pressure making the injectors act much larger, not by messing with the pcm as stated above, that can be done with aftermarket management but is not the case here. The stock injectors fail closed if overpressurized which would be instant death for the motor. Other injectors like the SVOs stick OPEN if overpressurized and are capable of handling more pressure to begin with.
04-14-2007, 12:11 AM
#11
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Originally Posted by moehorsepower
Mileage matters because Injectors DO wear out like anything else, I see stock motors with high mileage and injector duty cycle hitting max limit, spraying nitrous puts a demand on the engine thus requiring the injectors to work more. If it was a low mileage car I would say it is fine, I ran a hot cam with ported head, headders ect but my car at the time only had 25.000 miles and the duty cycle went up about 2%. That is also a lot of mileage on the motor to be spraying so just beware of everything else, Tranny if its an A4..
04-14-2007, 01:32 AM
#12
Rough guess, 30s or 36s, but currently best prices are on 42s (see Ebay, search 42 pph injector) and it's easy enough to tune for the 42s. (hint... take a LOT of fuel out at idle with the big cam and 42s)
Work with your tuner to select an appropriate injector size... yes, you should get the engine tuned ON A DYNO with the hotcam for best results. It's also CRITICAL to monitor fuel pressure at WOT under load, whatever size injectors you select, to make sure your pump can maintain pressure at the new required volume of fuel flow... and IMHO, you need a fuel pressure safety switch to kill the nitrous if fuel pressure drops too much, set around 35-40 psi active ALL the time
And FWIW, LS1 injectors run at 58 psi, so at 42.5 they flow much less. 28 pph LS1 ijectors flow about 22 pph on an LT1.
Work with your tuner to select an appropriate injector size... yes, you should get the engine tuned ON A DYNO with the hotcam for best results. It's also CRITICAL to monitor fuel pressure at WOT under load, whatever size injectors you select, to make sure your pump can maintain pressure at the new required volume of fuel flow... and IMHO, you need a fuel pressure safety switch to kill the nitrous if fuel pressure drops too much, set around 35-40 psi active ALL the time
And FWIW, LS1 injectors run at 58 psi, so at 42.5 they flow much less. 28 pph LS1 ijectors flow about 22 pph on an LT1.
04-16-2007, 09:09 AM
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moehorsepower- The only way I could see injectors dropping in flow is contamination. They may get a little slower over time from wear, but if the owner consistantly runs good gas the should not get restricted... But if gas has been let to gum up, then a reduced flow would be noted by increased duty cycles. Just like BurningRubber said above, it doesnt mean bigger is neccessary, just clean or replace.
96capricemgr- How does a dry nitrous kit cause an increase in fuel pressure? Ive never installed a dry kit, but Im almost positive that Ive seen lots of them that spray directly through the MAF, causing the PCM to add fuel.
95N2OFormula- You need to do some homework guy. You cant expect people to just tell you absolutely everything you need to know. Talk with the N2O kit manufacturer, AND talk to a experienced tuner for suggestions.
96capricemgr- How does a dry nitrous kit cause an increase in fuel pressure? Ive never installed a dry kit, but Im almost positive that Ive seen lots of them that spray directly through the MAF, causing the PCM to add fuel.
95N2OFormula- You need to do some homework guy. You cant expect people to just tell you absolutely everything you need to know. Talk with the N2O kit manufacturer, AND talk to a experienced tuner for suggestions.
04-16-2007, 09:30 AM
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I dont expect them to tell me everything i just wanted to know about injectors so i dont blow up my car im pretty sure thats what im doing is my homework, just doing it online...i mean what is this site for?
04-17-2007, 09:19 AM
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EVERY EFI dry kit Ive seen sprays the N20 through the MAF... Therefore like I said before, the pcm is in control of the fueling. So then you would need larger injectors. How large, I couldnt tell you because I dont know the common BSFC a nitrous motor uses. Thats why I suggested getting in touch with the nitrous manufacturer for a recommendation.
If someone would care to tell me the BSFC and the target HP (meaning expected flywheel HP on the shot) Id be glad to run the numbers and provide an injector recommendation.
If someone would care to tell me the BSFC and the target HP (meaning expected flywheel HP on the shot) Id be glad to run the numbers and provide an injector recommendation.
04-17-2007, 10:20 AM
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well consindering ive already got the dry kit installed thats a no no, and ill just be hopefully around 400whp...
Heres the mods
Full Exhaust
Hotcam Kit
75 Dry Shot
Moroso CAI
Heres the mods
Full Exhaust
Hotcam Kit
75 Dry Shot
Moroso CAI