Jeremy_84_F41

iTrader: (3)

Ok, I'm finishing up my plans for the fuel system side of my car to get this blower setup going. I'm using 24lb injectors for now because, well, that's what I have, and I'm on a budget. I'm also only looking at 6-8psi on a stock engine, so it's nothing radical right now, maybe 340 or 350hp at the crank, but eventually it will be much more (yeah yeah, just like everyone says, I know)..

Anyway, I see that Vortech sells an 8:1 FMU in their kits for the stock engines, so I know they're figuring on 22lb injectors, and they include a 155lph inline booster pump in their 3rdgen kits (seems sorta weak, but whatever). So, I'm thinking, ok, I'll buy the 8:1 FMU (or maybe the adjustable one, but the standard one is half the price), and I'm looking at this fuel pump.. http://www.racetronix.com/product/RX..._Pump_Kit.html I figure a high flow, high pressure in-tank is the better way to go (and cheaper), than to use a 255lph intank with a booster, or a stock pump with a booster.. even though some people swear this is ok, I don't know. I like the fact that the Buick guys swear by these pumps, and well, they're faster than I am, so I'll listen to them. So, that takes care of the fuel pump and FMU.. but obviously, this is going to be a lot of fuel pressure.. am I going to possibly have TOO much fuel for this basically stock engine?

I know an FMU really isn't optimal but I'm stuck with the stock GM computer right now (speed density car).

Thoughts? Am I going about this wrong? Maybe I don't need such a large FMU with the bigger injectors at this point? When my setup gets more extreme, I'll get injectors that are more suited to the application, so I think I can keep the same FMU down the road as well.

Thanks guys..

posi

I installed the walbro gss340m that is for superchagers and the hot-wire kit from racetronix. that pump will feed a ten second car.I have 24 pound injectors on my camaro that sc,also no inline fuel pump will be needed the gss340m will push what is needed

89ProchargedROC

the 340m pump will MAX out a 10 second car....not support one. 125mph is about the limit for the one pump then you can add another or add a boost a pump

Jeremy_84_F41

iTrader: (3)

That's really no problem, I doubt my car will ever see anything faster than 12's, I just want the boost because of my altitude, plus the way it enhances the powerband is awesome compared to just building an all-motor engine for the same basic power level.

So, considering I doubt I'll ever see 125mph traps, the 340 should be great. If I ever have to go faster, I'll look into sumping my tank and running an Aeromotive pump and larger lines, since I'm sure the stock lines become a huge restriction at that power level.

I'm still stuck on whether or not the FMU will be too much pressure at that ratio.. I guess the best solution right now might be to run an adjustable style, so I can dial it in exactly as I need it, or at least to get fairly close so I don't kill the engine right away..

89ProchargedROC

Just to let you know you.....as the fuel pressure rises the fuel flow goes down

i'd just get some larger injectors, a custom program, and the in-tank. But using the FMU WILL work, it just isn't the best thing for the injectors

Jeremy_84_F41

iTrader: (3)

I agree, I was looking at the flow chart or whatever for the 307 pump, and you can see clearly that the volume goes down a LOT when the pressure gets higher. But, the 340 pump is supposedly designed for forced induction, and gives a higher volume of fuel even above 60psi.

The reason an FMU or a programmable computer that is boost sensing (like with a 2 bar MAP sensor) is more favorable to me compared to a custom burn is because I drive the car at different altitudes.. mainly 4500-5000ft at my home, but occasionally up in the mountains, and occasionally sea level (Northern California).. a custom burn that is perfect up here at 5000ft would be rich at 8000ft, and would be lean at sea level. I don't want to make different chips for different altitudes, where something that is boost sensing would sense the extra airflow or lack of airflow and compensate without me having to think about it. I might still go with a larger injector, but above 30lb/hr or so, I'm worried about it running rich at idle with no boost, and loading up.. the computer can only compensate so much without a custom chip. I really don't think I'll need that much injector for that power level anyway, but maybe I'm mistaken.. supposedly a 24lb/hr injector can support 350hp, and that's figured on ~40psi, where it would obviously be higher with an FMU. As for not being good for the injectors.. I guess I'll just have to upgrade if I ruin these.