Does anybody have an idea how much HP the stock 19# injectors will support?
Right now on the 356 they seem to work well.
Just wondering how far I can go before replacing them.
thanx

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'88 RS (originally 2.8)
New 350, .040 over, ported vette L98s, ported stock tpi.
Old 305 injectors & chip
TES headers, 3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
(Damn the 2.8!)

 

19 lb injectors should be able to supply enough fuel to support 320 to 360 hp depending on the fuel pressure. A rough rule of thumb is that an engine will make one hp on .5 lbs of fuel per hour. 19 Lb injectors will support 38 HP per cylinder at stock fuel pressures. If you raise the pressure you will be able to support more then 38 HP per cylinder.

This is just a general rule, the actual application may require different injectors then what this rule suggests.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

the motor in my sig, always ran lean with the 19's. i have just put the 24#'s in but i have some tuning to do, and i have to figure out why its running so rough.

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Brandon
"ScreaminDeamin 360"
350 60 over, TRW forged 9.83:1 pistons,Hooker Comp headers, crane cam 216/228 .484/.512, crane 1.6 RR's, ported plenum, home made ram air, 19 lb SVO injectors, crane AFPR, all going through 3 inch mandrel pipe and a flowmaster.
New project-89 IROC
http://users.argolink.net/bvana
http://ScreaminDeamin.cz28.com

 

Willie's supercharged 305 (that was knocking on 11's door) has 19# injectors and his engine has been dyno'd at 421 RWHP. Only then was he at the point of maxing out on the duty cycles (remember you only have 10 ms to spray all your fuel @ 6,000 rpm).

Willie had a high flow fuel pump and very high fuel pressure though. Now that Willie has a D1SC ATI Supercharger and planning on 15 psi of boost, is he looking at alternatives.

I responded in another post, but when I got into eprom burning, I was surprised how overly rich I was running with my 22# injectors on a basically stock L98. This is with my fuel pressure adjusted to it's lowest setting that still gave a good spray pattern. I could install 19# injectors and with only 46 pis, I would still have to remove some fuel by shortening the injector pulse width to get my AF ratio optimal @ WOT.

And, if I was to further mod my engine, I could still run 19# injectors for quite while by just increasing my my injector pulse width and leaving my fuel pressure at 46 psi.

I do believe in the benefits of higher fuel pressure, but on the stock fuel pump, you'll shorten its life. 46-48 psi is a "happy median" for a good spray pattern while maintaining a reliable fuel pump and fuel injector life. But only when you have optimized your eprom to take advantage of this higher pressure.

I will be much happier when this "myth" of cranking up the fuel pressure on a basically stock engine dies the death it deserves. The only myth worst than this was "installing larger injectors" on a basically stock engine back in the late 80s. Man, people are foolish when it comes to being fuelish.

 

Glenn, I totally agree.

we used to call it the "Mo-Gas" syndrome.

 

Thanks guys.
I think the 19# will work for a while, It will be a while till i'll be making 360 hp.
One problem i have is that the car is running rich at idle with the 19# injectors, even with the pressure set low.
I think it is a computer/sensor problem.

------------------
'88 RS (originally 2.8)
New 350, .040 over, ported vette L98s, ported stock tpi.
Old 305 injectors & chip
TES headers, 3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
(Damn the 2.8!)

 

As I said, adjusting fuel pressure has its greatest effect at high load/low vacuum (like WOT) and least effect at low load/high vacuum (idling/decel).

You COULD get into the eprom, but if you have a relocated MAT or a cold T-stat, that will cause the overly rich condition too.

To take advantage of a relocated MAT (and don't get me going on low temp T-stats), you need to adjust the eprom. The GM eprom was not designed around relocated MAT (or even a TB-Bypass). The ecm thinks you are in "cold start" start mode with either a relocated MAT or cold T-stat.

Those were tricks from the 80s & 90s. We are in the 21st century now. If you are not prepared to get into the eprom, then set the MAT and T-stat back to stock until you are prepared to get into the eprom. I don't think ANY custom prom writer makes any adjustment for those (or possibly even knows about them). TunerCat (BIN editor) was just told about this an will be reflecting these tables in their new Version P of 8D when its released.

Not sure if they are reflecting it in 32 or 6E, unless someone told them where those tables are in the BIN. I'm still concentrating on the 8D (as my car is one), but I will get looking at the others when time permits.

[This message has been edited by Glenn91L98GTA (edited February 24, 2001).]

 

Glenn,
Please tell me about this thermostat deal. I always understood that it makes the ECM give warm-up enrichment, but I just recalibrated everything around that to be leaner. Then I'd use my POT for any adjustments I needed during WOT.
I did everything I could to keep the TPI & coolant as cold as possible, and still believe it works. I did have my own control over the timing & TC-lockup anyway, so what does it hurt?

 

yeah glenn, why you hate 160* T-stat so much man? tells us about it
Rick

 

n0

------------------
'88 GTA 350 Full of Leprosy (rust)
Headers, catback, free mods, Xtreme energy cam, intake pieces and 2100 RPM TQ

13.39@102.50 MPH
1.90 Sec ----- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!

 

exhaust fumes getting to rick's head. rick's on craaack, or rather fumes;;

 

wht the hell is an ICQ number?
a

 

I'm still running 19# injectors w/ my 355 and it does okay. However, it does lean out pretty good once it the rpms start climbing, especially over 5 grand. It would definitely appreciate at least 22 or 24# injectors w/ the big throttle body. Idling it actually tends to run rich which surprised me but I'm still running the stock ECM w/ a stock chip so I don't think it (ECM) knows what the hell is going on.



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'91 Z28 1LE; 355, Sportsman II heads, Edelbrock TPI w/ 58mm TB, Tremec TKO 5-speed, 3.73's & much, much more

 

Glenn hates 160degree stats because it is another mod that makes you run richer.

I too have found that the colder t-stat harms performance, noticeably. My engine currently operates at 176 degrees and has never felt better.

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.