HELP! injector swap gone bad?

95 svt cobra · Mar 25, 2008

I just swapped my 24# injectors for 30# and now my car is idleing reallyrough and its dogging bad, i know i need to get a tune but i did not think it would be this bad. what can i do for now until i get a tune?

carbed94 · Mar 25, 2008

what all is done to your motor???...supercharged anything like that???

95 svt cobra · Mar 26, 2008

i have gt40x heads, B cam exhaust,CAI smog delete

Anrev · Mar 26, 2008

Did you turn up the fuel psi? Gotta get an adjustable fuel pressure reg and turn it up to 42psi. And then recheck your timing. 14 deg adv. Then reset the idle and TPS. And lastly try clocking your MAF. You can actually find a "sweet spot" where the engine runs a little smoother by adjusting the clocking of the MAF.

95-stang · Mar 26, 2008

How do you clock the maf? Not heard of that one could be of interest to me too.

Trickflow.GT · Mar 26, 2008

95-stang said:
How do you clock the maf? Not heard of that one could be of interest to me too.

You need a fox maf to be able to "clock" it

Trickflow.GT · Mar 26, 2008

95 svt cobra said:
I just swapped my 24# injectors for 30# and now my car is idleing reallyrough and its dogging bad, i know i need to get a tune but i did not think it would be this bad. what can i do for now until i get a tune?

I thought we informed you this would not work...

Anyhow, if you dont want to tune it you will have to buy a MAF (either C&L, Pro-M, etc..) that is calibrated for #30 injectors.

Nick

95-stang · Mar 26, 2008

Ah thanks, something else i've learnt though.

I have a C+L with a 24lb sample tube, that will have to do atm then.

Anrev · Mar 26, 2008

You dont have to have a FOX to clock it. Just loosen the clamp and and twist it a bit.

Id bet money its just your TPS is off.

kyle94gt · Mar 26, 2008

+1 for the MAF

Schiffy · Mar 26, 2008

just having a MAF that is cal'd to those injectors will make a big difference... nothing like jumping head first into a project without having all the associated equipment to back it up :nonono:

95 svt cobra · Mar 26, 2008

yeah well you may be right on that but sometimes its better to learn the hard way. ill check the tps but im jsut going to get a summit maf probably thats already cal. for it

Trickflow.GT · Mar 26, 2008

Anrev said:
You dont have to have a FOX to clock it. Just loosen the clamp and and twist it a bit.

Id bet money its just your TPS is off.

Ok...stock 94-95 mustangs have a flange with bolts on one side of the MAF it is impossible to "clock" or "twist it...unless you mount the maf a full quarter turn (taking it out and rebolting it in the new position)

And what makes you think its his TPS...he threw bigger injectors in a car that does have the parts to support bigger injectors (ie tuner and or cal'd maf)

95 svt cobra · Mar 26, 2008

i think hes saying that because Anrev is running the exact same crate motor as i am with 30# injectors, him and i have been in contact before about diff problems with my setup so any help that anyone has is appreciated

carbed94 · Mar 26, 2008

why do u need that big of injectors .....just wandering

Anrev · Mar 27, 2008

Because Ford said it could handle them. Ford rated our motors with 24#ers and a 65mm TB @ 340hp. If you do the math, thats right about topped out on those injectors. The tech rep at FRPP told me that you can go with bigger injectors and TB and make more than 340 hp with a good tune.

As for clocking the MAF. Yes one end is flanged. Thus making it hard to clock. But the other is not..... Granted, some peoples setup wont allow for much movement. But mine does.

And I was under the impression that 95 svt cobra HAD got a new MAF. My mistake.

So yeah man, get a 30# MAF. THEN tune the TPS.... :thumb:

Stangbangin · Mar 27, 2008

carbed94 said:
why do u need that big of injectors .....just wandering

well 24# injectors working at 90% duty cycle (how long the injector stays open during a 4 stroke ycle) will support 370 hp. But no one recommends running them at 90% duty cycle. 80 to85 % is wher eyou should be as far as your duty cycle goes. So giving the number 340 which at 80 % duty cycle 24# injectors are being maxed out. 30# injectors at 80% duty cycle will support 412 hp/

Paul · Mar 27, 2008

Anrev said:
Because Ford said it could handle them. Ford rated our motors with 24#ers and a 65mm TB @ 340hp. If you do the math, thats right about topped out on those injectors. The tech rep at FRPP told me that you can go with bigger injectors and TB and make more than 340 hp with a good tune.

As for clocking the MAF. Yes one end is flanged. Thus making it hard to clock. But the other is not..... Granted, some peoples setup wont allow for much movement. But mine does.

And I was under the impression that 95 svt cobra HAD got a new MAF. My mistake.

So yeah man, get a 30# MAF. THEN tune the TPS.... :thumb:

You don't need 30# injectors - 24s would be fine. The motor was originally rated at 240 horsepower, not 340. I'd swap the old ones back in and call it a day if it was running fine before. You don't have a wild combination that needs lots of fuel.

Paul.

95 svt cobra · Mar 27, 2008

no i do not have the original motor paul, its a crate motor directly from FRPP and it was rated at 340 with headers and intake. which i have. im trying to get the most out of what i have without adding a blower cause that is going to come later down the road

95-stang · Mar 27, 2008

Same here, i dont have a crate motor, but i'm planning on a blower later on "down the road", which is probably where the crank and gearbox will wind up.