hay guys im running a 5.7 tpi l98 stock engine... my fuel pump(47.5 psi) just went out so i got a 100 psi bbk hi perf fuel pump, fuel sending unit and asembly, fuel regulator adj, and fuel filter... My question is that i want to replace my injectors too but dont want to buy 8 stock 21lb injecters because im going to do some serious mods with a new engine in 6 months from now... i want to get 30lb... if i get 30lb injectors do i have to replace anything else i realy dont want to replace ecm... would it run ok on this old engine 190,00 miles... or would it be better to leave stock injectors... before the fuel pump went the car ran realy jerky so im thinking injectors too... any sugestions???? can the car still run good with the stock ecm and same fuel pressor with the 30lb injectors till i have the money to buy the new engine that can withstand this pressor... or can i have a 30lb injector run like a stock 21lb injector with keeping rail presor the same...

 

30lb injectors are way to big for a factory set-up. they are to big for even a mild build or a L98 with bolt-ons. get some 24lb fms injectors. they should be good to about 300-350hp

 

I DONT KNOW I THINK 24 LB ARE TOO SMALL IM GOING TO BE PUTING A 350-400 HP ZZ4 ENGINE IN 6 MONTHS FROM NOW AND DONT WANT TO GET SMALLER THAN WHAT I WAS TOLD FOR THE ENGINE... CAN I RUN 24LB OR 30LB INJECTORS AT STOCK SPECS UNTILL THIS CHANGE IS MADE... WITHOUT INCREASING FULL PRESURE AND CHANGEING ECM... I WANT TO DO THAT THE DAY OF THE NEW ENGINE.. MAINLY I WAS HOPEING I CAN RUN A 30LB INJECTORS AT ITS STOCK 21LB ....

 

Stock is 22#

....the 24 pounders are what you'll need, and they'll run OK, but rich. A tune is recommended.

30 pounders won't run well if at all. Plus they're too big for what you're plannin'

 

Get AFPR,

24# svo (m9593-a302) 17# @ 20# and 29# @ 60# fuel line or

30# (m9593-b302) 21# to 37# either one will cover your stock and performance setup.

$100 at auction.

 

I'm not so sure on 30's being too big but you will definitely need a tune in order for the car to run right. 30's on a stock ECM tune will most likely be constantly fouling out your plugs, dumping fuel into your oil, and destroying your cat(s).

 

I'm not sure exactly what that all means, lot's of # and @.....but if you're suggesting using a AFPR to compensate for the wrong size injectors, it's terrible advice. It may be a bandaid fix that works temporarily, or if you're lucky, it'll never cause you any problems, but you shouldn't ever RECOMMEND a hack as a fix. Sure, we've ALL taken short cuts, but you don't recommend it to someone as the way to do it "right".

There are plenty of threads explaining why this may appear to work, but isn't actually the proper fix. ....but then, I'm not sure what you were recommending, and maybe thats NOT what you were suggesting at all.

I suppose TOO BIG, and BIGGER THAN NEEDED are two different things. I've heard of people tuning 30# injectors to run on a mostly stock motor. Again, it's not needed but.......

 

SO WHAT DOES EVERYONE SUGEST I NEED NEW INJECTORS RIGHT NOW TO GET BYE.. DONT WANT TO CHANGE THE ECM TILL I GET THE NEW ZZ4 330 HP ENGINE AND PARTS IM KEEPING EVERYTHING TUNED PORT INJECTION... THINK I SHOULD GET SOME CHEAP INJECTORS TO GET BYE OR SHOULD I GET BIGER ONES AND WILL IT BE ABLE TO RUN ON EVERYTHING THAT I HAVE STOCK TILL I CAN HAVE USE FOR THE BIGGER ONES WHEN I GET THE ZZ4 ENGINE... CAN THE ECM AND STOCK PARTS RUN THE INJECTOR FROM 30 OR 24 LB TO 21 LB OR WHAT WOULD YOU GUYS RECOMEND I DO BECAUSE IM CONFUSED...

 

HAY ALSO WHAT SIZE TPI INJECTORS SHOULD I GET FOR A 330 HP ZZ4 ENGINE WITH VORTEC HEADS WITH NOTHING BUT PERFORMANCE PARTS MADE FOR DRIVEING AND SHOW... MAY GO ALL THE WAY UP TO 400 HP...

 

If Trav installs an Adjustable fuel pressure regulator and the m9593-b302 30# fuel injectors. It will run his stock motor, because at a fuel line pressure setting of 20# they will flow at 21#/hr.

When he upgrades the motor and wants to produce more hp, at a fuel line pressure of 60# they will flow at 37#/hr. Enough for around 600 hp (flywheel).

These differant flow numbers come from the factory calibration sheet. It would be hard for me to believe, that they are wrong.

This is not the way I would do it, but he only wanted to buy/install one set of injectors. Maybe not the best, prefered, or optimum.

This will be less perfect on the stock motor (over kill) but better at 400 hp (flywheel).

The 24#/hr injector (a302), at 60# FLP will be a 27#/hr. Good for 430 hp (flywheel)

There are hundreds of posters on this board and everyone will have a differant opinion.

BTW Caps mean you are shouting. I can hear you.

 

OK, I understand that pressure/pounds per hour logic on paper. ....but the AFPR is intended for minor adjustability on a properly tuned car.

At 20# of pressure, I'll agree with the math, but you'll have so poor fuel atomization, the car may not even run. I know a lot of new cars at insanely sensitive. A TPI might run, I'm not sure. .....but even still you're giving up power due to poor line pressure. ...and even IF you have no poor effects from pressure, and everything works great, you've still tricked the computer into adjusting for the large injectors. It sees a WAY rich condition, and drops back the amount of fuel. It may run at THAT point, but what if the computer needs to cut back MORE fuel? ...it can't, because it's been cutting back the whole time and doesn't have the adjustability to cut back MORE.

I'll agree with you that people do it. I'll agree that often it works. But, as even you said, it's not really the way to do it.

I also agree that everyone has opinions, and they're certainly all not correct. My opinion 24 pounders, and get a tune.

 

FROM EXPERIENCE....DO NOT use an AFPR to reduce pressure to compensate for larger injectors. I attempted that & the car barely ran. I was using 36lb/h @ 25psi. The car ran better at stock psi but WAY too rich

 

My vote would be 24# and a good tune. Then when the injectors run at 80% Duty Cycle upgrade.

Or run stock 22# with stock engine and AFPR when at 80% DC upgrade.

Or when doing a big upgrade to motor do the injectors too.

Remember I was talking about one very specific injector, do not include all the rest.

Each injector type and size have advantages and disadvantages. Get the data sheets. Talk to the designers.

Talk to people that have used that exact injector and used it exactly the way that you are trying to use it.

Trial and error is a long, slow, and expensive road to walk.