I've read a lot of old threads on 19 lb injectors on the 3.4 motor. Generally it seems as though the 19 lb injectors are too big. My question is to the guys with 3.4 pr motors using a truelo intake and ported exhaust or headers. I've got a 260h cam and some mild port work, will be using the truelo intake and truelo headers and magnaflow cat. I know the 17 lb injectors are good to 200 hp, my car won't be anywhere near that so am I wasting my time, money and fuel using new accel 19 lb injectors in my car? I plan to have it dyno'd to use the information to fine tune the chip.
welcome anyone's input on this.

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1986 Fiero GT Fastback 3.4Lpr with 4T60
1998 Jeep Grand Cherokee with "big boy" 5.9 motor
1983 Honda Goldwing 1100 Interstate

I'm using a 3.4 V6 crate engine with the Trueleo intake and exhaust, and the SSI Stage 3 camshaft (roughly equivalent to the Crane H272). The intake was specially made to fit a Buick GN throttle body (59mm). And the headers dump into a 2.5" exhaust. I tried 17 lb/hr injectors at first, but was having trouble getting enough fuel at high load in the upper RPM range. So I traded up to 19 lb/hr injectors, and re-adjusted the fueling tables.

That may or may not be an issue for you. The only way to know for sure would be to do some WBO2 datalogging.

That said, if you have the ability to tune your ECM, then it's usually better to err on the big side. As long as the injectors aren't ridiculously oversize, you can reduce fueling to match. But once an injector hit its maximum capacity, no amount of ECM tuning is going to help.

I am using 19 pound Ford injectors but also have a turbo in addition to the 3.4. Yes, it did run very rich until I had some custom fuel table programing work done.

Nelson

The reason that the cheap, common 19# Ford injectors make the car run too rich is because they flow like GM 22# injectors. So when you tune thinking 19, you're still too rich. Learned this the hard way on both my 4.9 and 3.4 ...
Some people think it's the voltage flow rates (GM rated at 13.8v and Ford at 12v) others say it's that they are rated at a different fuel pressure. Whatever - they just flow more than you would normally think and require either the base pulse width vs. battery voltage table turned down to run right and not have that big dip in A/F when you hit the throttle...

I'm using GM 19 lb/hr injectors (for the N/A 3800). I don't get the rich spike when hitting the throttle. Actually it would go lean for a moment, so I had to make the acceleration enrichment more aggressive.

[This message has been edited by Blacktree (edited 03-13-2014).]