Hi all, I work at an autoparts store and pulled some injectors for a 3400 and 3800, they appear to be exactly the same size on the exterior has anyone used 3800 injectors on a 3400 for forced induction builds? My plan if it makes a difference is either 225-250 hp here at 5500 feet above sea level, or about 200-225 hp all the way up to 12000 feet above sea level. We have a very tall very fun mountian for hill climbing just outside of town, but by my estimates the monte is hardly making 100 hp at the top of the mountain, and second gear is really slow to accelerate. Do yall think I'd need bigger injectors for either of these goals? And if so what will fit the 3400 stock fuel rails?

 

I'm not too sure if they're compatible. Doing some reading, it appears that V6 Trailblazers have compatible injectors, but you may want to do some reading on 60degreev6.com, or check Grand Am forums - as Grand Ams came with 3400s. I'm assuming you've swapped your 3100 or the top end?

 

No, I've got an 03, came with the 3400. I assume the top swap is either heads, intake manifold, or both. Do I have anything to gain from this or is it a 3100 thing only?

 

To be up front, I don't know anything about the 3400 injectors / modding. For a rough ballpark though, a .8 duty cycle is common on stock injectors. If the 3400s are typical, that would mean you could potentially squeeze 225 crank hp with pegged WOT duty cycle before it started leaning out. Of course that assumes you keep fuel pressure the same, the max rpm the same, keep the fuel type the same, and also keep it NA. Changing any of those would change the results.

I do wonder though- how would you plan to get 225-250 hp out of it? That seems extremely high for a NA build unless it was a pretty serious heads / cam build. It also seems extremely low for any kind of forced induction.

As far as 3800 injectors fitting - one option is to grab your calipers and head down to the local junkyard to measure. I tried searching the various W body forums I'm on and couldn't find a definite answer (although oddly enough found several threads from people asking if 3800 injectors would add power, lol).

 

I am doing forced induction, I'm building an electric turbo system, so it will technically work like a supercharger with a big pulley

 

Interesting, what unit are you getting?

I heard Garrett was working on electric turbos, but haven't seen any available for sale. Also curious what you're doing about the voltage increase? Seemed like all the units I'd seen in development were set up for 48v.

 

I've already got a motor sitting around for this that can operate anywhere 12-48 volts, I'm gonna couple it to a Garrett tp38 compressor with a belt drive and run whatever voltage gets me enough air for 250 hp, which is about 375 CFM. But, that's at sea level, so I'll more likely be around 400 CFM. The only thing I dont know about this build is if the stock injectors can deliver enough fuel for that.

 

Hmm, that's different. More like a centrifugal supercharger style then. Just curious- since youre going to have a belt and pulley anyways, any reason not to just hook it to the engine belt system so it works like a normal SC?

IMO if you're really leaning towards 250 crank hp, I'd just plan for new injectors up front. The chances of the stock injectors being good at about +40% power is near zero. Even if you can squeak by, duty cycle will be near static.

I found a relevant thread on the GA boards that might help:

Larger Injectors [Archive] - GrandAmGT.com Forum

Looks like the 3800 L67 injectors weren't a great fit. The one user claimed they were shorter, the retainer clips didn't fit, and the plugs had to be changed. Not insurmountable, but not a drop in either.

They did note the injectors for the 4.2L were a direct fit, and given those engines were 270-290 hp stock, they'd be plenty for your goals with some room to grow.

 

Sweet, lots of good info there, makes me think my 250CHP goal is a little on the small side lol. So I wonder, how much hp can be made reliable with those injectors? Maybe 275? I'm also not worried about what octane gas I'd have to run.

As for running it like a Centrifugal SC, I hadn't even thought of that untill you said it, however I'm also looking into 3D printing the compressor and getting upgraded parts that the ford guys run on their turbo diesel setups. Needless to say, I wanna keep the compressor away from the heat as much as possible.

 

IMO it's way on the small side for the amount of effort you're talking about.

To put it in perspective:
-Itll still make less horsepower than a bone stock S3 supercharged 3800 swap, and that engine hasn't even been made in nearly 15 years at this point.
-Itll make less horsepower than many brand new sedans and crossover SUVs offered today. Plenty of options out there at 250-300 hp in just the mundane 4 door models, not even getting into actual performance platforms- camaro, mustang, etc.


Not that you're wanting to spend $30k on a new car, just saying it would suck to spend all this time and money just to struggle to keep up with some random person in a rental Accord going to the grocery store, lol.

TBH I probably wouldn't even bother with a custom fab project for less than 300 crank hp today. You should be able to at least get that slapping an eBay turbo on just about any engine at this point.


No clue, but given they come stock with 270-290 hp with stock range of duty cycle, they should be good for 300 crank at least, even with a boosted bsfc.

I wouldnt let the injectors limit your build in any way though. We don't have a lot of members with modded 60 degree v6s in here, but I can't imagine they use some really unusual injector. Id bet one of the injector companies makes something for whatever power level you could imagine.