8388

If your not happy with the results, then your tuner did not tune it properly. #30 is not that much of an injector for a healthy 383 if tuned properly with the right FP. There's alot to the tuning, temperatures of both coolant and air have to be factored in aswell. This is not something you do in just a couple of hours. Unfortunately, some tuners will not take the time it really takes to get it perfect.

Racetronix

A Delphi 42# or for that matter even a Siemens 60# injector can be tuned to provide factory type A/F at idle and part throttle. If fuel is dripping out of one's tail pipe then they should find a person that knows how to properly tune their ECM/PCM with a WBO2. Running an injector beyond 80% DC does not cause meltdown. Running an injector beyond 80% DC in many cases does not give the injector enough time to properly close before the next opening cycle which can cause erratic / inconsistent fueling. Depending on the type of injector, the ECM/PCM driver, injector wiring and vehicle voltage this % will vary. 80% is a good rule of thumb to follow. Consider the lbs/hr required to support your max HP and factor a 20% size reduction into what you can reliably get from your selected injector to make sure you have enough. For example, a 42# injector will deliver 33.6# at 80% DC.

Turbo Buick, import owners etc. regularly use 50# and up injectors as a first step upgrade. These cars have small CID motors but are still able to maintain factory type mileage and drivability while at the same time pass emissions tests.

Racetronix use to tune 42# injectors in many L98 and LT1 motors for over 10 years with great results.

0ski_dwn_it

They are also running turbos, which is a whole nother ballgame.

Again you can't ague with results that people are getting with larger motors than he is going to be running - with much better flowing component and RPMs.

Do you honestly think we would be running 9s with 42# injectors?

8388

wait a minute, weren't you the one that said fuel is fuel ?


Make up your mind.

Racetronix

NA or FI has nothing to do with the idle quality and the injector's capability to deliver a narrow enough PW to target a nice lean 14.5:1 A/F. In fact having a smaller CID motor usually makes things more difficult when it comes to tuning a large injector so you V8 boys have it easy most of the time.

There is always going to be someone who will brag about how they got away with going fast on a budget or w/o something that was recommended to them.... that is until they damage something. Some people who run fast with small injectors only tell half the story (i.e. running FMU's or high base FP). Many people fail to factor in worst case scenarios which can place more demand on the fuel system. In many cases WOT at the track or dyno places less demand on the fuel system than a run against a Porsche down the highway. Heat soaked motors, fuel systems, low voltage and power accessories are not things which usually impact a car at the track but they do on the street. All these things can make the ECM/PCM command more fuel / higher DC from your injectors which could put them over the edge if you chose an injector which is just enough to get you buy based on ideal conditions.

If you have someone that is a good tuner, they should be able to make any reasonably sized injector deliver excellent idle quality and street manners.

Mad-Mic

alot of these so called local tuners don't know squat about fuel injection. it's not bigger injectors = more HP. it's not more fuel, more fuel until you smell it then back it down a jet or 2 like with carbs. what ski said is what my data has shown over the past 3 years surfing these sites. 24 lb injectors are fine on stroker small blocks. it boils down to pulse width and how long the injector is open. too much spray and atomazation does not accur resulting in super rich conditions because the fuel is actually blowing past the air and not atomizing with it as it should. if this happens people think to turn the pressure down. well this won't work either due to the fact again Atomazation will not accur because now the fuel is clumping like a spicket drip.

people don't realize if the fuel air does not properly mix before it enters the cylinder you'll get alot of fuel blow by and you will be scratching your heads trying to figure it out.

my motto is do what everyone else is doing. it's working for a reason.

strokers get 24-27 lbsers and blower cars get 30-36 lbs. no more no less for L98's and LT1's. LS1's with smaller runner length can go 1 step higher and usually do due to the short runner being able to atomize the fuel better.

sometimes you have to think alittle to be able to understand why it works the way it does. this is why all the big car manufacturers went away from Quadra Jets and Carbs to Fuel Injection. you can take a glass of water and pour it into another glass but no matter how slow you try to pour it it's still a stream of water. ie carburation. injection proves again why it's more economical IF you can understand it.

alot of people ask me alot of questions about these ole L98's and the question i get asked the most is "I got a stroker that is running rich. I've done everything and nothing works. What am I missing?" first thing i ask is what pound injectors they are running. i get the same answer! 30 lbs'ers! i tell them switch to 24's and up the pressure to around 47 psi to start. well after alot of debate they finally give in and buy 24's (usually 6 months later) then low and behold the AF is perfect! i always get a chuckle out of it when they tell me down low it's rich as h3ll but on the gas pedal it's fine. turning down those 30 lb'ers to 40 psi works for one part of it but not the other part and this really stumps them.

so the moral of this story is do what others that go fast have done then copy it. if you don't wanna copy it then take the bits and pieces that work and put it to your combo. fuel injector size and fuel pressure might be the only thing that you will need to copy to get it in the ball park.

Mad-Mic

good arguement but we all know aftermarket engine management systems give more control over the injectors. most so called tuners don't know squat about OBD I and they don't wanna know or learn. if they can't plug in and make minute changes at will and see how it reacts then pulling the chip burning the chip reinstalling the chip and hoping what you did was right or better yet them not having the software and hardware then having to rely on an outside vendor to "Get it Right" which is a shot in the dark if they don't do any data logging. i know several big name LS1 tuners that won't even touch OBD I cars (well i should say earlier OBD I cars) unless it's LT1 Edit or have some kind of engine management system like FAST, EFI Live, or DFI. with an aftermarket setup you can make 75 lb'ers work in place of 30 lb'ers. you obviously gotta know your stuff so it don't blow pig rich and melt your eyeballs but it can be done. seen it work on a 388 stroked D1 setup and it blew 12.9:1 across the board on a dyno run after it got dialed in.

Racetronix

When Racetronix was providing tuning services an emulator was used. This allowed for quick changes to be made on the fly. The system was much faster than flashing an OBD1 PCM. Tunercat, TTS, Datamaster and Diacom+ where all part of the deal. After a while a library is built up which also helps speed the tuning process.

Mad-Mic

hehe right on your one of the few one of the guys in my car club deals with one of the guys from pcmforless does tuning sessions for 300 plus dyno time for 6 cars i think or something like that in NJ area sometimes. i only got knowledge from forum members and friends with vettes and fbodies really but i've been on an intense learning pace since day one of purchase. i also know a few shop owners around baltimore and try to pick their brain as much as possible.

i eat and breath this stuff......lol literally. i got 5 motors, 5 intakes all fuel injected, 2 700R4's, T56 6 speed with all needed parts for 3rd gen FBody swap, 2 rears 1 10 bolt built with 3.42 gears and 1 9 bolt with 3.73 gears, soon to be 4 sets of heads, 3 full set of rims, and a bunch of other parts to go with it.....lol

ok so i keep this on target and not stray too much let me throw another piece to the puzzle. nitrous? upto a 250 shot? how should i handle that? obviously i don't think 24's will handle it. 30's? guys with D1's run 30's-36's. eventually i am going to do a direct port setup.

0ski_dwn_it

Yes fuel is fuel....you are confusing the two ideas here....

He mentioned GNs running 50# injectors as a first mod/upgrade...they are also running turbos - this ups their requirements for fuel since much more air is passing through, hence the reason they are run 8s in a v6. As I said its a whole nother ballgame.

Put some 50# injectors on your car and report back how well it runs.

In your case you mentioned that our motors would not last...here I was pointing out that my motor can run a 12.8 AFR at higher duty cycles, and nothing is going to change that running for a longer period. Hence fuel is fuel.

Don't make this subject harder than it needs to be.

All I am trying to point out here is that there are a good many very reliable, consistant and driveable cars here from 383-434CI that make some tremendous power - most running 24# injectors. Their is nothing erratic about dialing in a car to the .01 sec and having it run it. And To my knowledge, none of them are hiding anything....although corky and I have been accused by many when this subject and MAF use used to come up on the TGO, until one of their own came to the track to inspect the cars himself, and the cars checked out and ran .5 sec quicker than his cloned copy of our setup, with larger injectors.

If someone wants to put in huge injectors to say they have BIG injectors, I could really care less - its their motor. This fella asked a questions, like I do, and I like to have my questions answered with real life examples and results, rather than speculation. Theory is theory, and reality is reality. I don't think John Force's team runs on theory much - they most likely work in the direction that gets results. The above examples too get results.

Off to the track to beat up on some race cars...

jerkyboy

I've got a DFI system on my car. The shop who put my 383 together had an Accel certified DFI tuner there. They put my car on their dyno (which they just got and hadn't figured it out yet...another story) and told me my 30lb injectors were maxed Not knowing any better at the time, they talked me into 48lb injectors!!! When I questioned that size, they said the "DFI could be tuned to make any injector run ok" as someone noted above. Well guess what? They couldn't. After hours and hours of tuning time, it still spewed gas out of the exhaust. I retrieved my ride and flatbedded it down to Woodbridge dynotech here in VA and John (who is well respected and is also a "certified Accel DFI tuner") immediately pulled the 48s and put the 30s back in. Turned down the FP and I picked up over 50 hp without any other tuning. He said that the 30s were still too big but after spending tons of $ already on injectors, I was done. In addition, since I ran so rich for a while, the rings never seated and I ended up pulling the engine. I don't buy the fact that you can run any injector and just tune them down. My $.02

8388

That's funny, one of my cars does use 50# injectors @ 80% DC and I'm very happy with my tunning. BTW, no fuel dumps out of the exhaust

Mad-Mic

i think i remember you having this problem. we talked about it on the forums or thru email and i suggested http://www.JimsPerformance.com for DFI tuning and or http://www.FBodyCentral.com both shops are reputable for DFI tuning in the baltimore area. Jim did my friends 91 Z/28 388 stroker with D1 SC setup with the 70 lb'ers or whatever they were. like ski mentioned forced induction is a different ball game thats why they worked i am guessing.

i'm glad you got your setup straightened out!

Zix

Would that happen to be a Callaway turbo motor?

8388

Well the Callaways have the supplemental injectors, even at the factory power level it was very important. The car I'm refering to is my 383 mini ram car.

bmalec

When you say "383 mini ram" car, are you referring to the supercharged 35th anniversary car on your site? That engine bay... scares me!

Ben

8388

Yes, but remember, there's no boost at idle, and gas is not coming out the exhaust as previously mentioned. It's all in the tunning, if you spend the time to do it right. Btw, I also have it map for running it without the blower with the same 50# injectors, and it runs beautifully.

bmalec

Just curious, do you know the injector pulse width time at idle? I'd guess... under 1ms when warm?

Thanks!!

Ben

Racetronix

Correct!

There is much more to this subject but it would take many pages to cover all the basics.

There are many things which impact injector performance that should be considered.

Injector design impacting opening and closing speed, spray pattern, atomization and flow linearity
Injector supply voltage
Injector operating temp
Injector firing pattern (batch, B2B, SEFI)
Injector timing / phasing relative to intake valve action
Injector positioning within the intake tract relative to the intake valve
Intake runner air velocity and flow patterns
Injector operating pressure (pressure across the injector not just MAP)

Not all injectors perform the same in all motors given the same flow rate. Ask your tuner about these things. If they can not give you straight answers then it is time to find another one.

8388

I've been looking for a diskette I made a few years ago of the mapping. when I find it, I'll post it. This car uses the Haltech E6GM.