can injectors be too big?

SVT3183 · Jan 27, 2006

sorry for the newb question....is it possible for injectors to be too big or do they simply just act like smaller injectors except when pushed for more fuel?

86bluecobra · Jan 27, 2006

yes they can be to big.

SVT3183 · Jan 27, 2006

well lets say you have a supercharger and you put 42# injectors in to compensate. when you are driving without much boost how doesn't this cause a problem then? what happens when they are too big?

loudpedal99 · Jan 27, 2006

You can only shorten the pulsewidth so much. Injectors being to large can cause idle issues, bad driveability, and bad fuel mileage. I have a buddy with 83lb injectors (Sean Hyland 4.6DOHC, Vortech T-trim) and his car doesn't like to start, especially when warm, and he's custom tuned.

42lb'ers are large for off-boost conditions, but they can be easily compensated for in the tune; the larger the injector, the harder it is to compensate.

SVT3183 · Jan 27, 2006

got ya...thanks for the replies

moneypit94 · Jan 28, 2006

so you guys think i will have problems with my 150 lb injectors i just ordered... ? hehehe

final5-0 · Jan 28, 2006

loudpedal99 said:
You can only shorten the pulsewidth so much. Injectors being to large can cause idle issues, bad driveability, and bad fuel mileage. I have a buddy with 83lb injectors (Sean Hyland 4.6DOHC, Vortech T-trim) and his car doesn't like to start, especially when warm, and he's custom tuned.

42lb'ers are large for off-boost conditions, but they can be easily compensated for in the tune; the larger the injector, the harder it is to compensate.

I agree

Yet one more Q that has to be answered with the starting phrase

"It all depends upon"

Grady

1SLO306 · Jan 28, 2006

what setup and we pretty much tell u what u need:SNSign:

SVT3183 · Jan 28, 2006

i was thinking 42's with a kenne bell at 6-8#'s. stock cobra heads, cam and bottom end, upgraded pump (255), ignition components, exhaust, tb, and obviously maf. sound about right?

1SLO306 · Jan 28, 2006

i would do 24's maybe 30'sif u plan on adding more to it lata

SVT3183 · Jan 28, 2006

damn thats it? i already have 24's stock in the cobra. i'm almost definitely adding more down the road. any other opinions on this?

final5-0 · Jan 28, 2006

I'd be happy to give you my thoughts but first I wanna see your complete combo and what are your long term plans.

Is this your dd?
Is this a street or street/strip car?
Are you gonna stay NA?
If so, how much rwhp do you expect?
Are you gonna try and build this combo with out a Self or Pro Tune?

You did not get much response simply because peeps that may have gone to the trouble to give you their help had no data from you to work with.

Not trying to be a hard azz but

If one wants info ...... they gotta give info

Grady

SVT3183 · Jan 28, 2006

i listed my combo like 2 posts up...you want more specific than that? it's not my daily driver and it will see pretty limited track time. it will be dyno tuned when the blower goes on. it will more than likely see some afr 165's and a mild cam some time down the road. need more info?

moneypit94 · Jan 28, 2006

well if a kb is all your running then 30-36's is all you will need.. actually you may not even need to jump up to that. Your looking at around 300 rwhp so there is no need to to go up all that much.

If you plan on doing different heads and cam later on 42's wouldn't be awful, just need a good tune.

Plenty of people running 300 rwhp with 30lb injectors or less...

final5-0 · Jan 28, 2006

Well

Now that you talk about better flowing heads (AFR's) and a Pro Tune, then here is the deal.

If you can, you want to try and not have to buy any combo parts twice.

Sounds like you are gonna end up with a complete h/c/i combo and it will be blown.

For that combo I would use
a big tb like maybe 70 or 75
a big maf like SCT
42 lb inj's

Now

IF it is gonna be a while until the blower & big heads
you don't need the above three items

however

if you got a tune
the above items could be made to work thus making the most of your money spent

Just trying to help you save a bit of cash

Grady

mustangramair · Jan 28, 2006

My friend didn't listen to me and he put 38# injectors in with worked over GT40 heads, F303 cam, and cobra intake. He was dissapointed in how is car ran, always stalled out. He ran a best of 13.4 at 104. Then we swapped his injectors out for 24lb injectors and he dropped to 12.7 @108.

I8URVTEC · Jan 28, 2006

Your feul pump also has to be able to keep up with the injectors...don't forget to upgrade the pump too if you go with much bigger injectors.

SVT3183 · Jan 28, 2006

well i just talked to the guy that will likely dyno tune my car (craig at radical racing in jersey) and he said 42's. did your friend have his car tuned? and yes i'm putting in 255 lph pump, probably the high psi holley @ summit

mustangramair · Jan 28, 2006

SVT3183 said:
well i just talked to the guy that will likely dyno tune my car (craig at radical racing in jersey) and he said 42's. did your friend have his car tuned? and yes i'm putting in 255 lph pump, probably the high psi holley @ summit

No he never got it tuned, after he ran the 13.4 we just swapped his injectors right out and put the 24lbs in for next weekend. He wasn't happy with 12.7, so now he is in the process of building a 347 stoker.

mo_dingo · Jan 29, 2006

If you put too big of injectors on a too small C.I. engine, it will pull so little air that the pulse width will drop to close to zero ms, which means the computer will literally not add any fuel at all.

Increasing the idle speed will help with this problem in some cases.

So it all depends on your plans for the car, how big of injectors you will need for whatever combo you choose.
Scott

can injectors be too big?

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