alright guys, i gotta idea about making some horspower utilizing the TBI system but i don't know ANYTHING about them. i want to use a 144 (or comparable) supercharger with a tbi sitting on top. question is, what fuel pump/computer/tbi unit/pretty much everything; should i use? any help appreciated

edit: this will start out on my 305 and be transferred to a big bore combo later.

Try posting this on the power adder board. They would be able to help you.

It has been done but it costs $$. Many people don't do it because of that reason. You can get more power out of a 350 with a mild heads/cam set-up.

well, i am looking to run the EFI class in the NSCA for the 2005 season and you are allowed one poweradder. while centrifugal superchargers are cool, i have always loved the way a roots blower looks. it's kinda hard to run a MPFI system on a roots blower without getting into some serious cubic$$$'s, you know what i mean? so, i am just throwing around a few ideas. any help would be appreciated.

It is deffinately a cool set-up but I don't think anyone has done it yet successfully. You may be the guinea pig. But don't give up..you could be a TBI power adder forefather.

I think Ezey Go is right, the Power Adder guys will be able to help you out a lot more on this one...

Bruce (90RS305)

should be pretty straight forward.

by far the hardest part is going to be getting it to run correclly. and by that i mean fuel. i assume that with a FMU you could get the fueling close enough to be able to fine tune it with custom PROMs.

the hardest part is going to be that with the possitive displacement blower, you can build boost at part throttle, that will be the biggest tuning hurdle.

i know that it has been done at least once on this board, but he used a command950 to run his, so he likely had at least a 2bar MAP sensor. if you put a 4bbl Holley TBI unit on, with the commander computer, it should be very straight forward.

the fuel pump, will likely depend on the ammount of HP you make, but i would bet the racetronix's intake would be fine up to the ammount of power a little 144 is capable of making, then you just need to regulate it down to the correct level.

computer, depends on how you go about it, the stock 8746 or 747 ECUs are probably not the best choice, but with a FMU, it would probably work ok. i was reading on the DIY PROM board yesterday, about using a 749 ECU from the syty's that might be a very good route, as it can sense boost. you will need to do more research on that though. the command950 is also a valid option. you can get a 4bbl holley with ECU, harness ect. for about $1300 from summit.

personally, i think you may have a easier time if you switch to multi port....


some kind of fuel rail/injecter combo on top of the blower, with a plenum and a throttle body...


then its pretty straight forward to run a 749 ECM....

because they're all OEM parts, or somthing you can do deciently cheap, it should save money compared to getting a aftermarket FI system..

and i assume you're asking because you want to save money... right?

how exactly would running port injection on a roots blower be easier?

730 SD harness plugs into the car.

repin for the 749.

swap map sensor.
swap fuel pump.

and the hardest part, make a top plate/plenum to hold the throttlebody, injectors and fuel rail.

you then can set it up for the ECM to handle the boost without a problem.

to save some cash, you could get the harness and TPI setup as one unit off a doner car, then reuse the FPR, fuel rails, heh, even use the plenum, cut a hole in the bottom, fill in the sides...... and then get some money back by selling the base, runners, ect...

just a idea... :lala:

btw, id like to point out that its not really port injection.. just 8 injectors....

if you could run the TBI injectors off the 749, that would work too.... i donno if you can or not..


but my idea does allow for you to ditch the TBI throttlebody.....

MrDude.

Reference this post.

https://www.thirdgen.org/techbb2/sho...hreadid=216261

the 749 CAN drive 2 TBI injectors.

much cheaper to get a $20 adaptor plate for TBI than it is to try to rig up 8 injectors to fire into a plenum that fits onto a carb flange.

what gains are there from going from ditching the TBI throttle bodie, the holley 670, or 454 TBI has a 2" bore, that is abotu 50mm, larger than a stock 48mm TPI unit. granted it is a wet flow, so there is a diffrence there, but i doubt there would be any gained airflow. and for clearance, and easy of install TBI is a better choice in the application. the amount of fab work to get port style injection on this, would likely cost more than a 900cfm holley 4bbl unit with a computer than can already handle 2bar or 3bar MAP sensors.

cool.. well if the 749 can run thoes injectors, then its even easier....

see, i was thinking the commander950 with the 4bbl cause i have a laptop now that could run the programs. what about fuel pump though. i don't even know what kinda pressure i should be running. what does a stock tbi unit push out? it's more then a carb but less than tpi, right? this is all new to me and i would like to learn as much as possible.

it varries from the factory, usualy between 9-12psi

mines running 11psi as set from the factory

ok, so would a blue pump work?

i don't know, i am not sure if the injectors used on the 4bbl holleys run at the same pressure as factory TBI injectors. you can run a pump that was designed for higher pressure, then regulate it down.

maybe i should give holley a call.

Check out the picture of my car in the post pics of power adder. I am doing basically everything you are talking about. It was a tbi running through a roots blower but then I converted it to mfi and kept the tbi for air flow. Running it with a 749 ecm. Look for 67 ss.

The commander tbi are designed to run at 21 psi. You need an inline pump. The blue wont cut it.

I run a roots blower and tbi on commander 950 albeit a 2 barrel 670 unit on a 6 banger.

In fact Ive got a commander 950 and a new tbi inline pump with the mounts, rubber insulator , fittings etc , I might sell.

let me get the new car to the house and road worthy 614, then i will let you know if i am still interested. i have been following your Fageol (or whatever) 2.8 buildup for several months now and was hoping that you would chime in at some point.

Curious what blower your looking to slap on? The Camdens are pretty slick , very rare but they are a real treat to see . The 144 and 142 are common, they are still cool. Or did you have something bigger in mind?

I think the camden is at www.camdensuperchargers.com

144 on a 305 at first (as long as the motor is OK) then probably on a 4" bore motor later on down the road.


not looking for anything SUPER FAST, but wouldn't mind a streetable low 11 second car with a roots blower sitting underneath a cowl hood...people will go "Woah! what's that!" seeing as most superchargers are all centrifugal now and not many folks see roots blowers anymore. i like them, always have. a tbi sitting on top would be the ultimate in cool (to me anyway)

Yeah sounds like a plan, Definately get a 4 barrel tbi unit. Im sure with 5-7 psi it will be plenty fast on a good 4" bore motor, even the 305.