Fuel Injectors performance

[Chilicat]

94 z34

Im ready to replace lower and upper intakes for a polished and gasket matched set.Also a Borla cat back and carsound cat is going in.
What about injectors? Is there any performance gains in replacing them ? If so , what should I use?

Thanks

[bszopi]

RE: Fuel Injectors performance

My recommendation...

http://www.60degreev6.com/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=29&page=1

[Scott205]

Ok, here is my question. Obviously new injectors seem to help replace old worn out, and miss spraying ect. Does anyone know what flow rating lbs/hr the orginal injectors were in the cars? especially the 92 3.4L and the 96 and rare 97 3.4L DOHC?

Anyone here anything bad about the Accel injectors? 26lbs/hr too much? I think the 96's are 21lbs/hr orginally. Although I swear the 92s were only 19.

Accel rates there as:
Stock: 21lbs/hr
Plus 1: 23lbs/hr
Plus 2: 24lbs/hr
Plus 3: 26lbs/hr
Plus 4: 30lbs/hr

They also tell you how to figure out how 'big' and injector based on HP. Based on that the formula is
(Max HP x BSFC) / (number of injectors x duty cycle) = lbs./hr
we can all figure out what Max HP, i am going to say i find a way to get another 35HP out of my brand new motor and say 250.
BSFC stands for brake-specific fuel consumption. Most non-turbo high performance engines are from .045 to 0.55 Turbos jump to 0.55 to 0.65. I am going to use the 0.55 since we have a high compression engine. Number of injectors.. 24! wait, only 6 and lets say we want to street it just a bit so duty cycle of 0.85 instead of the more conservative 0.80 GM did. that should bring us to:
(250 x 0.55) / (6 x 0.85) = 26.96 lbs/hr
or (250 x 0.50) / (6 x 0.80) = 26.04 lbs/hr which is quite streetable.
perhaps we don't have that much efficency to get to the 0.85 like a C-6 corvette but then who knows what you guys will come up with.

Lets do it at stock
(215 x 0.47) / (6 x 0.80) = 21.05 lbs/hr

We pretty much know ford and chevy both used .80 as there standard OE cycle. And of course they milded out the cams and computer control, even with the MAF in place of the MAP. Of course these numbers can change with the amount of pressure being put through by your regulator, but unless you have changed that from standard to an adjustable one.

Now lets say you just want to go to the strip or you drive at or near WOT at all times, you have played with your cam timing, polished and ported everything, got the new chip, the horribly expensive Granatelli MAF, built a cold air intake and your tranny can handle the 300 HP your engine puts out.
(300 x 0.55) / (6 x 0.85) = 32.35 lbs/hr
so if you do a lot of mods, an adjustable fuel regulator (hopefully mounted outside the plenum so you can adjust between street and strip) might be a good option.

But I want your opinion, especially before i plop down $200 bucks on new injectors.

[SappySE107]

Stick with stock. They are 23# and unless you reprogram the computer, its going to be a major performance loss from larger injectors. Unless you do a lot more to the engine, stockers are plenty of fuel.

[Dave]

a general rule of thumb is that you can go 10% larger with no adverse effects - so if stock is 23# you can go to 25# without needing to reprogram, however, it will take your car some time to get the maps down well enough to make it feel good, so like Ben said, stick with stock - if you still want to replace them, just get 6 injectors, all stock sized that are matched perfectly, that will gain you more in the longrun due to the better balance of fuel flow. If you're looking to have your injectors tested, cleaned, and matched, contact the folks at TPIS (tuned port induction specialties) at http://www.tpis.com they know what they are doin' and they're really good at it.

--Dave.

[blk92z34getrag]

I was also looking at the Accel injectors, the 23# ones... anyone have any experience with them?

[Dave]

every Accel part I've used has gone bad prematurely - I haven't used their injectors, but I would be less likely to do so because of their other parts.

You can have your injectors re-done at TIPS for $25.00 each - which would also balance all the injectors - far cheaper then buying new ones.

--Dave.

[bszopi]

Or you can check out Witchhunter Performance (check out http://www.60degreev6.com/modules.ph...rtid=29&page=1 for the link and a sample of their work) for $12 per injector, with a turnaround of 1-2 days.

[Scott205]

The 96 fuel injectors may be 23lbs/hr but i confirmed from A/C delco the stock one from GM in 92 were only 21lbs/hr. This was from 91-93.

Speaking of that last night when i was searching i ran across this at Jegs.

Accel Performance Fuel Injectors - 24 lbs/hr (each)
Item # 110-150124 1 x $22.88 (reg 39.8

I bought them so I will keep y'all up to date.
6 injectors and 9.99 Handling?? oh well.. for $147.27 better than 21lbs/hr dirty injectors.

Seems cheaper than the one i replaced in the 92 motor for 80 bucks a piece.

[blk92z34getrag]

Let me know how they work for you when you get them in. I'll probably pick up a set of those before the end of the summer... I have a lot of performance plans for my car... but first I need a new knock sensor... =/

[OldSkoolGP]

Long as we're on the subject, does anyone know if the resistance is the same between the 91-95 and 96-97 injectors?

[Scott205]

Actually the split on the injectors were 91-93, 94-97. Pretty much all GM run the same resistance (the fords do the same but slightly different). The big change is the ones in the Hondas and other imports from Japan and Europe.

In 1994 the injectors evidently jumped to 23lbs/hr from 21lbs/hr.

I think this was partially do to the fact that the plenum helped breath a bit better, the 21lbs tend to have to stay on longer (dwell) and they knew the SFI version was around the corner.

[Scott205]

computer programming shouldn't be necessary unless you go to 30lbs or higher injector rate. Keep in mind, if they want x amount of fuel they turn them on or off longer. you just don't want to screw the cycle up to much. but at WOT they can dump more fuel.

[OldSkoolGP]

Ok cool, I'm eventually going to get 96 SFI injectors and just needed to make sure the impedence was the same.