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Old 05-25-2005, 12:09 AM   #1
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are my injectors just too big?

ok I have ls1 injectors on my new tpi setup. but these are not the regular 23lb injectors @ 43.5 psi (bosch part# 0280155890) these are the larger 28 lbs @43.5 (bosch part # 0280155931) seen here
http://www.racetronix.com/12561462RFM.html
the problem I am having is liquid gas actually coming out the tail pipe through out the rpm range. I have a 305 which I know came with the 19 lbs/hr injectors. I used these injectors because I was able to get them for a hundred bucks and I could use them when I build my 383 engine without having to buy new injectors for the 383. I set the injector constant to 28 lbs/hr and my adj. fuel pressure regulator is set to 44 psi.
the car does run but I get no trouble codes. my fuel pressure reg. tests fine, all the sensors are good, the pump is good, timing is right, plugs and wires are good, there are no vaccum leaks, so this is the last thing I can think of. I was reading th GM high-tech performance article about injectors and I am thinking that my injectors are just too big now. so really what I am asking is that should just changing the injector constant allow me to run an injector this large? does too large of an injector cause an overfueling problem of this nature without tripping any codes? what do you guys think?

Last edited by 1992rs/ss; 05-25-2005 at 12:12 AM.
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Old 05-25-2005, 02:15 AM   #2
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I would go ahead and say that those injectors are a little 2 big
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Old 05-25-2005, 06:46 AM   #3
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Quote:
Originally posted by FactoryFreak
I would go ahead and say that those injectors are a little 2 big
No, they are ALOT too big. It's just plain crazy to run that big of injector on a 305...why would you do that to yourself?
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Old 05-25-2005, 08:22 AM   #4
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Be careful with all the fuel in the chamber, it could wash the rings. I have seen it happen.


But yeah, those are def too big, heck, i am only running 24 punders on my modded 355.
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Old 05-25-2005, 09:46 AM   #5
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Quote:
Originally posted by 9D1BURD
Be careful with all the fuel in the chamber, it could wash the rings. I have seen it happen.


But yeah, those are def too big, heck, i am only running 24 punders on my modded 355.
Yep.....I'm running 24's on a 383 and they work just fine.
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Old 05-25-2005, 10:01 AM   #6
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They will work just fine :-)

I ran 30#'s on my 355 , 24# on my stocker GTA, same 30#'s are on my 383.


As far as too big, I run the Mo Tron 65.5.# on my lil'ole 3.8 :-)

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Old 05-25-2005, 05:40 PM   #7
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Quote:
Originally posted by 3.8TransAM
They will work just fine :-)

I ran 30#'s on my 355 , 24# on my stocker GTA, same 30#'s are on my 383.


As far as too big, I run the Mo Tron 65.5.# on my lil'ole 3.8 :-)

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No they won't work "just fine"....however, they will work. You are going to have to compromise your set-up in order to make them work, and it will be marginal at best. I get a kick out of all the guys who think they need big *** injectors on their motors. Boosted applications however, are a different story.
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Old 05-25-2005, 07:05 PM   #8
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It would only be compromising and marginal at best if you were completely clueless as to how to properly tune a setup for larger injectors.

U can usually easily go about 150% on injector size and be almost okay with only making a change to the injector constant.

I dont do this but have changed injectors on an engine as the only changed and datalogged it with multiple logging programs and using a wideband....

Depending on the injectors, there is a little difference, no two things are the same. Most people here dont bother to do more than make it drive okay and let it go at that.

And by the way, my 350 was pushing it using the 24# inj. Duty cycle was getting a little high, over 80%.

Most stock style 350, unless spinngin to the moon should ber able to survive on either 24 or 30# inj.

And yes I do believe in sizing them to the application, but you have to be an idiot to buy injectors everytime u change something instead of going what you know your plan is.

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Old 05-25-2005, 10:17 PM   #9
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Quote:
ok I have ls1 injectors on my new tpi setup.
Well there is the big problem. The LS1's use Multec 2 injectors. The TPI uses Multec 1 injectors. They use a different signal to operate correctly.

Not related to F-bodies but is to the situation:
I did an engine swap on my 88 z24 Cavalier. The 2.8 uses Multec 1 injectors. I swapped in a 2000 3.1 which uses Multec 2 injectors. With the Multec 2's the engine run way too rich. In order to run them correctly your gonna need the ECM programmed for the correct signal.
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Old 05-25-2005, 11:39 PM   #10
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some of these ls1 injectors, like these, are 12 ohm resitance like the stock tpi ones, there are quite a few people on this board running ls1's without any problem
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Old 05-26-2005, 07:26 AM   #11
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Quote:
Originally posted by 3.8TransAM
It would only be compromising and marginal at best if you were completely clueless as to how to properly tune a setup for larger injectors.
Yup, that's me, completely clueless

I operate on the principle of work smarter, not harder. Let me ask you this....how long does a guy have to dink around with making an overly large injector work versus just getting the right size to begin with? If you spend 8 hours tuning a car to make a set of big injectors to work, you would have paid for a set that would have worked right from the start. Where you and I come from, time is money
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Old 05-26-2005, 12:35 PM   #12
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"In order to run them correctly your gonna need the ECM programmed for the correct signal."

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Old 05-27-2005, 11:27 PM   #13
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I think 28#'s on a batch fire 305 is just a Taaaaaaaad bit to big. But if you got a deal i would take that as compensation for tuning around it.

You need to tune it quick though before something gets burnt.....good luck
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Old 05-27-2005, 11:58 PM   #14
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Don't confuse condensation with fuel.
If you haven't fully warmed up the exhaust you could have water mixed with exhaust that "appears" to be fuel. Mufflers can hold a fair amount of water that could take half an hour or so to dry out.
Just thought I'd throw that out there.
If it is definatly fuel then keep bumping up the constant in the bin.
they do seem to be a bit much for that size motor but should not be dumping fuel out the rear unless your fuel gauge is lying to you.
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Old 05-28-2005, 01:15 AM   #15
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Yeah, JP86 its condensation from the exhaust, it running rich as all heck, but vacuum leaks have a way of doing that lol

Its a massive vacuum leak :-)

We had 10inches on the guage running at idle and about 15inches when we revved and held it.

Ran thru all the obvious sources and were unable to pinpoint it thus far.

I met up with curtis today and we spent 6 hrs in his mechanics parking lot working on it.

Fixed various vacuum leaks that we found and even some new plug wires.

We were limited by where we were and what we had to work on it, but it looks like the intake manifold itself is leaking somewhere.

10 inches of vacuum is about 1/2 of where it should be if it was running right. Basically a TBI engine with TPI on top.

We will up date as we know more, he's going to tear it down and look for anything obvious as he does. He going to call me so I can come over and check out the base when he pulls it

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Old 05-28-2005, 10:36 AM   #16
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One thing that might be obvious but overlooked is the PCV or Canister line run into the TB behind the throttle plates instead of in front.
I had mine that way and couldn't figure where the extra air was coming from.
Simple but very effective vacuum leak that can be made when the car was not setup for TPI originally.
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Old 05-29-2005, 09:03 AM   #17
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We pulled them all and plugged them off and results were still the same.

hit all the dumb obvious stuff and eliminated as much as humanly possible....

He tore it down(to the base) and said theres almost no silicone near the frt and rear chinawall.

I'm heading over ther today to take the intake off with him(base) and get it resealed hopefully for him too.(fingers crossed)

later
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Old 05-29-2005, 10:05 AM   #18
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Quote:
He tore it down(to the base) and said theres almost no silicone near the frt and rear chinawall.
Was it leaking alot of oil?
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Old 05-30-2005, 10:08 AM   #19
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28's are too big for a 305. I ran a set of 25's on my 305 when I had Mega Squirt. What I had to do was turn the firing mode from "batch" to "alternate" so I could achieve effective pulse widths. I then switched over to GM 730's and tried the same thing with not as much luck. Even putting them as 19's yielded too low pulse widths. Any way, large injectors without tuning correctly will either go way rich or to uncontrolable at low VEsor what ever method you have.
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Old 06-02-2005, 01:07 PM   #20
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should have ran straight fuel line into the intake. Your drowning that baby motor!!!!
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Old 06-02-2005, 01:34 PM   #21
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If it's really running that rich you should be able to confirm by looking a the spark plugs. Maybe you should drop the fuel pressure two or three psi and see what happens.
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Old 06-02-2005, 01:34 PM
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