- just bought 24# bosch3's for my 85 from FIC. 4X repeat customer - great customer service, and never an issue! 
Fuel Injector Selection help...
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
I took a perfectly running car and sent injectors off to him although everyone said it was a waste of money, the injectors are fine, throw some snake oil at it and life is good. "Before" test showed one was way off and the rest were kinda varying. "After" test showed that the set was pretty matched. The one that was way off had a collapsed filter basket.
Know what? I did borrow a tech school's bench and wasn't sure I was reading it right that one was off. Now we know why. 100K for daily driven cars and 3 years for powersports and the Vette that sits in the garage during winter.
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Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
when the 85 TPI engine was being engineered, it was the first ECM controlled multi port injected engine in a mass produced car for GM, so there was a couple of "over engineered" things going into it,
the injectors were slightly bigger than they needed to be, so there was no nasty lean outs, eventually in production fuel pressure was lowered to compensate. The industry standard for measuring injectors is 43 psi.
The engines were fitted with TRW forged pistons, again taking no chances with lean outs or engine damage.
They ran batch fire to ensure plenty of fuel flow (and thats pretty much all the 870 computer could handle)
The engineers were probably crossing their fingers for the first year, and everything went all right, so in 86 they went to 22 lb injectors and upped the ECM computing power.
you can run 35 psi, you can run 43 psi, depends how hard you drive your car really ?
when you re attach your vacuum line it runs less pressure during normal driving anyway.
the injectors were slightly bigger than they needed to be, so there was no nasty lean outs, eventually in production fuel pressure was lowered to compensate. The industry standard for measuring injectors is 43 psi.
The engines were fitted with TRW forged pistons, again taking no chances with lean outs or engine damage.
They ran batch fire to ensure plenty of fuel flow (and thats pretty much all the 870 computer could handle)
The engineers were probably crossing their fingers for the first year, and everything went all right, so in 86 they went to 22 lb injectors and upped the ECM computing power.
you can run 35 psi, you can run 43 psi, depends how hard you drive your car really ?
when you re attach your vacuum line it runs less pressure during normal driving anyway.
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
True, with the hose it runs less than max but if you hit WOT, it will run lean if you crank the pressure down. And if you are not going to run WOT now and then, why even get a Vette?
Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
I don't follow. IF the ECM was set up with 43 and you run 35, wouldn't it go lean? I would think that it is best to run whatever the factory pressure, be it 35 or 43 since that is what is calibrated for. Sure, you maybe can run 35 even if you are set up for 43 and maybe you can get away with it but I would think that if you want to run off the reservation, wouldn't you want to datalog to be sure before you burn a hole in the piston or run too rich?
True, with the hose it runs less than max but if you hit WOT, it will run lean if you crank the pressure down. And if you are not going to run WOT now and then, why even get a Vette?
True, with the hose it runs less than max but if you hit WOT, it will run lean if you crank the pressure down. And if you are not going to run WOT now and then, why even get a Vette?
the pulsewidth of the injector is not a set value, the ECM constantly changes it to suit the feedback it gets from the sensors, particularly the O2 sensor.
so 35 psi is probably good if your on a Sunday afternoon club cruise, and 43 (or even higher in some cases) is probably good if your doing some Sunday afternoon autocross.
Last edited by blackozvet; Dec 7, 2015 at 02:36 AM.
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
the pulsewidth of the injector is not a set value, the ECM constantly changes it to suit the feedback it gets from the sensors, particularly the O2 sensor.
so 35 psi is probably good if your on a Sunday afternoon club cruise, and 43 (or even higher in some cases) is probably good if your doing some Sunday afternoon autocross.
so 35 psi is probably good if your on a Sunday afternoon club cruise, and 43 (or even higher in some cases) is probably good if your doing some Sunday afternoon autocross.
I don't know about the driving you do but every day it is in my hands is at least 2 or 3 WOT runs.