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injectors

I

insanegt1

Guest
I have an 86 and want to change the injectors. Who knows what stock injectors are in the 5.7? I have a new set that are calabrated at #28.8. Can I use these or not?

Phil
 

Ken

Gone but not forgotten
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1987 Z51 Silver Coupe
I believe 29 lb. injectors were the factory issue, but I'm probably wrong again.
 
I

insanegt1

Guest
Ken -- Put the #29 pound injectors in and now it sugers. The rpms run form 400 to around 900, Doesn't seam to surge when its in gear. Also the retainer clips on the old injectors will not fit on the new oness the injectors are around 1/4inch shorter then the stock ones taken out. So I diden't put them in. Doesn't seam to leak at all. There is no grove going around the injectors like the old ones just slots on the side so even if the injectors were long enought the clips would not rotate to lock then in. ANY HELP ?
 

Ken

Gone but not forgotten
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1987 Z51 Silver Coupe
I don't know why the new injectors won't fit, and I don't know what to suggest. Hopefully someone else will chime in with some help for you.

As for the surging, it sounds like you might have other issues to deal with.

_ken :w
 
Joined
Mar 3, 2001
Messages
314
Location
Andover, MA USA
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1986 "Bright Red" Coupe
I replaced my injectors a few years ago, I replaced them with 22# injectors, these are close to the originals. I have had no problems, smooth idle and more power than the OEM's. I think the 29# injectors are too large for a stock motor, the computer is probably trying to compensate for all that extra fuel and is cycling them to lean out the mixture. You should go with the stock size unless you have done some major mods. When I replaced the injectors I also added an adjustable fuel pressure regulator to zero in the fuel pressure also. Again, it should be set at specification for the vehicle because the computer will always try to adjust fuel delivery to control emissions. You should also look for any air leaks in your intake system such as at the runners, plenum, throttle body etc. Air leaks can cause surging also.
 
I

insanegt1

Guest
I understood that #29lb were factory issue injectors. If not than what is the factory poundage on the 86?. So if the #29lb injectos are all wrong then I don't want to throw anymore money to that Vett GOD in the sky.and I don't want to take this Vett apart to many more times. I guess I will take the old stock injectors down an have them cleaned and put them back in. Seams that no one in this hick town in the mountians of Colorado know how to work on a Vett TPI system. This Vett has been in the garage more that on the road.
 
Joined
Oct 30, 2001
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Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
When starting my car yesterday for the first time after installing an adjustable fuel regulator, it surged something awful until I dialed the pressure down a bit (initially it was at 60-something PSI) to a more reasonable 42-43. It does sound like too much fuel is being pumped in.

How hard was it to get those injectors out?
[RICHR]
 
E

Eagle85C4

Guest
I believe there needs to be more research done here. I was told and have read that stock injectors for the L-98 were 19# and that the 24# came out with the LT-1. Now according to a chart from TPIS the 19# injectors are capable of providing up to 38 HP per cylinder for a total of 304 HP. The next one up for them is the 27# injector which is capable of providing 46 HP per cylinder for a total of 368 HP. The chart is to be used as a reference to allow the user to select the proper injector for your specific application.
 
Joined
Mar 3, 2001
Messages
314
Location
Andover, MA USA
Corvette
1986 "Bright Red" Coupe
When I 1st replaced my injectors I also had the pressure up higher for "more performance". It doesn't really work that way it seems, the on board computer is always controlling the opening and closing of the injectors for optimum performance, all the higher pressure does is put excess strain on the injectors by cycling them more and also you can probably hear them cllicking open and closed when set at higher pressure. I get best seat of the pants performance at 43 psi. I got my injectors from Tim Marren at Marren Motor Sports. These guys were very helpful with advice, they sell balanced flow sets of injectors. Have had zero problems since I installed these. Before installation I had hard strats after the engine was warm and slight hesitation.
 
J

jnsampson

Guest
Injectors

I have an 85 coupe. From what I've read and seen, the STOCK factory injectors for that year pushed right around 19# per hour. I have recently purchased through eBay 8 slightly used (17, 000 miles or so) injectors for a total of $76.00. A single, NEW injector from GM costs in the neighborhood of $125.00.

A 29#/hour injector, from what I've read, seems to be a bit much. But then again, I could be wrong.

Ecklers has a set of injectors for $310.00. Mid America has a set of Accel Injectors for right arount $400.00. Both sets are pushing 24# per hour and there is a "high performance" set pushing more. But again, 29#/hr seems to be too much for a stock engine. I don't think the L98 changed that much between 85 and 86.

Why are you changing out your injectors?
 

maxrevs85

Well-known member
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709
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Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
The factory called them 22# I believe they were actually 18# ...this is according to TPIS......the stock injectors are more than enough for most mild mods. The adjustable fuel pressure reg is a better investment.
 

Ken

Gone but not forgotten
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Jan 30, 2001
Messages
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Hermosa Beach, CA
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1987 Z51 Silver Coupe
Some technical questions answered...

Fuel Injectors

There are a number of Fuel Injectors on the market today the following injectors have been furnished on GM OEM systems: Lucas, Bosch, Rochestor and Multec. The prices vary considerably and performance differences are hard to detect. Basically they are sized for application. The 5.0L injector is sized to deliver approximately 4.05 milligrams of fuel with a 2.5 millisecond pulse or 18.13 lbs per hr at approximately 36 PSI. The 57L injector is sized to deliver approximately 4.83 milligrams of fuel with a 2.5 millisecond pulse or 23.92 lbs per hr at approximately 43.5 PSI. This information is typical for all manufacturers and flow rates will vary slightly even between identicle injectors.

Lucas is presently pushing their new High Output Disc Injector and is referred to as a High Performance Injector. This product was introduced in March of 9l. They are competitively priced at approx $60.00 each. A wide variety of flow rates are available to include 18lb/hr, 24lb/hr,28lb/hr, 37 lb/hr. These are all 16.2 Ohms and will work well with all GM TPI ECM's Rochestor injectors are presently furnished for the 90-94 GM 5.7L engine. It has an all metal nozzle and performs well. Priced at approx $75.00 each. Bosch injectors are also an excellent choice at approx $87.00 each.

While there are significant differences between the TPI and LT1 induction systems and computers, the injectors are essentially the same. Sequentialport injectors and batch fired injectors are sized in the same manner. We regret that we have not been able to make DYNO comparisons of these products. We will be glad to share whatever we hear on this subject with you when you call. FIS stocks all of the injectors referenced.

For more information, visit Fuel Injection Specialties. ;)

_ken :w
 
I

insanegt1

Guest
I have the 29#in the Vett now and seams to be running quite well. Haven't got a good answer to this question. To run highter pressure injectors or go standard. Some say not a problem run highter.Some say the engine won't handle the excess gas with out major mods. Experts have said to go ahead and run them as they have on there engines and have not had a problem. Then another expert tells me &^%$%& the engine will not run right with a highter poundage injector. I was told by an expert on corvetts that the injectors were leaking down and causeing the hard starting when warm. So after changing the injectors out I find out that there isn't any pressure in the line. I thought the old injectors just leaked down. But in changing out the fuel filter I find no pressure at the filter. Meaning the line isn't holding pressure and not the injectors fault at all. (Must be the fuel punp.) Back pressure valve is leaking I would suspect. Seams my Vett expert should be working on Fords
 

Ken

Gone but not forgotten
Joined
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Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
The computer is going to be controlling the injector duty-cycle now matter how you look at it. So, unless you modify the process monitoring device, it won't matter what size injector you use; the time it remains open and delivering fuel will be controlled by the ECM or DFI, or whatever it is you have.

_ken
 
I

insanegt1

Guest
So as I see it (reading between the lines) it doesn't matter what size injectors you use because either the DFI or ECM control the opening and closeing of the injectors. If the DFI or ECM control the opening and closeing than its the amount of fuel that is shot dureing that opening time. ie- 30# will squirt more than 19# while the injectors are open. but if the fuel pressure regulator controles the pressure to the injectors then the opening in the injectors are what controles that amount??
 
Joined
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Tallahassee, FL
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none right now :(
The computer wants the car to be in balance, not rich, not lean... Bigger injectors help on modified engines because the spray pattern is better on a bigger injector compared to a smaller injector with the fuel pressure cranked up... Your ultimate goal should be to just get the correct balance of air/fuel... if you don't the computer will compensate, and you could actually lose power from a bad spray pattern... If you go with an adjustable fuel pressure regulator, you shouldn't be concerned with the actual PSI of the fuel, but the air/fuel ratio... good tuners (the cars that go the fastest) don't worry about PSI numbers, simply if the car has the proper mix
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
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Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
The numbers that are used to rate injectors are referring to the amount of fuel the injector is capable of delivering in a given amount of time. As such, the most a 29# injector could deliver under optimum conditions would be 29 pounds of fuel in an hour.

_ken
 

-=Jeff=-

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Feb 2, 2001
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909
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Bartlett, IL. (Chicago Suburb)
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1990 ZR-1
Eagle85C4 said:
I believe there needs to be more research done here. I was told and have read that stock injectors for the L-98 were 19# and that the 24# came out with the LT-1. Now according to a chart from TPIS the 19# injectors are capable of providing up to 38 HP per cylinder for a total of 304 HP. The next one up for them is the 27# injector which is capable of providing 46 HP per cylinder for a total of 368 HP. The chart is to be used as a reference to allow the user to select the proper injector for your specific application.

Okay here is the straight scoop on injectors sizes...

85 L98- 24#
86-91 L98- 22#
92-93 LT1- 22#
94-96 LT1- 24#
96 LT4- 28#

Hopefully that will end the confusion.. Also 19# were on F-body TPI 305 cars

I skimmed through most of the posts.. with the 28# injectors on your 86 I bet you are running real rich, you will either need to lower fuel pressure or have th ePROM changed to compensate for the bigger injectors.

So as I see it (reading between the lines) it doesn't matter what size injectors you use because either the DFI or ECM control the opening and closeing of the injectors. If the DFI or ECM control the opening and closeing than its the amount of fuel that is shot dureing that opening time. ie- 30# will squirt more than 19# while the injectors are open. but if the fuel pressure regulator controles the pressure to the injectors then the opening in the injectors are what controles that amount??

Yes this sounds right.. comparing yoru STOCK 22# and your now 28# if you want to adjust you will lower fuel pressure to allow less amoutn through, but without touching the ECM the injectors both stay open for the asame duration.

The optimum idea would be to leave the fuel pressure alone and get the PROM in the ECM changed to compensate for the different injector
 

maxrevs85

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Joined
Dec 17, 2001
Messages
709
Location
Eaton Rapids, Mich
Corvette
!985 ,blue coupe, 4+3 Z51
TPIS told me that with the mods I have ,that I should use 24# inj, at about 44 psi . I purchase the Accel's from summit for $229. Same injector they sell in the Mid Amer. and Ecklers for $399.
 
E

Eagle85C4

Guest
And those mods would be????? I also have an 85 z-51, but alas it is an ...gulp....automatic...
 

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