FiTech EFI for 350 TBI/Vortec

[RickardEriksson]

Hi, i'm currently building a new engine for my 1990 K1500. I bough a L31 Vortec Longblock and i was planning to use the TBI from my old motor when i found the Fitech EFI 400hp Throttle body injection.

The problem is that the Fitech is unable to control timing, do you guys know if it is possible to use the Stock computer to just control the timing with stock TBI distributor and let the Fitech control the fueling?

Thanks!

 

[JScott23]

It would probably be in your best interest to run an HEI distributor. My thought on the factory distributor would be that its not going to keep firing spark when its not getting the corresponding signals from the rest of the TBI system. Disclaimer I have not actually tried it. But for the money, I'd just pick up an HEI. they're pretty easy to set up and make adjustments on.

 

[RickardEriksson]

Can i still use the computer to control lockup? Or should i buy a seperate lockup controller? Thank you.

 

[Chewy1576]

I think it's possible to use the stock ECM to control spark and the transmission, but you would need to find a way to leave the existing TBI system sensors in place. The coolant temperature and MAP sensors shouldn't be difficult to leave. The throttle position sensor will be tricky because you're getting rid of the stock TB and I'm sure the one on the FiTech TB is internal and can't supply the same signal to the stock ECM. You would also need to disable any fuel delivery related codes so you don't have a red light on the dash all the time.

 

[RickardEriksson]

Hm, i found this earlier https://www.summitracing.com/int/parts/cei-108103. That maybe is a solution to the TPS problem?

 

[Chewy1576]

Just by looking at the pics on the FiTech website, I can't tell which wire loom or plug is for the TPS, but if it is indeed on the outside of the unit and can be spliced into it could possibly work. The stock ECM is looking for a 0-5V signal, anything around 0.55V is considered 0% TPS and 4.5ish V is 100%.

 

[RickardEriksson]

It should be possible to make custom external TPS for the stock computer and hook it up the the wire or linkage, like with a potentiometer or something?

 

[Chewy1576]

That is exactly what the stock TPS is. If you can mount it and get it to supply those readings reliably, it will work.

 

[RickardEriksson]

Okey, i basically have two options, I am trying to find pros and cons with the two different setups;
GM TBI with Dynamic EFI (430USD) + Computer controlled distributor (180USD) + Heated O2 (80USD) = 690 USD (897 USD with taxes)
+Cheaper
+No need for making new linkage for transmission
+Computer controlled ignition timing (Better MPG?)
+Lockup Control
-Older parts
-Harder to tune

or

FiTech (800USD) + HEI Distributer (90USD) = 890USD (1157 USD with taxes in Sweden)
+ More expensive
+Easier to tune
-No ignition control (Less MPG?)
-Requires separate lockup control


I'm driving a few miles a day, used parts are not easy to find in Sweden, what would give me the best mileage? Would the Fitech give my more horsepower, even with a properly tuned and bored GM TBI?

There are no emission regulations on this truck in Sweden.

210/220 112 LSA 0.480/0.480 Lift Hydraulic roller
Dual Plane intake
Shorty Headers

What do you guys think? It's hard to find experienced people in Sweden since most of us just build turbo Volvos

Thank you.

 

[Chewy1576]

Tuning with the Dynamic EFI is more involved, but totally possible. Their software automates the VE table tuning, as opposed to doing it manually in a spreadsheet. Although I do know of a few places to find really good spreadsheets to help with this. Use of a wideband O2 sensor (which is included in the FiTech system) helps a lot.

Could you try to run a vacuum advance on the distributor, so you could at least get some kind of timing adjustment to help get the most out of the engine? It looks like the FiTech system will work with an ignition box to control timing too, but that will drive cost of the system up.