Has anyone ever put a Holley 4bbl TBI unit on using the original computer (PROM change though) and just some custom wiring? If so, how well does it work and how does it do on gas? Just curious, thinking about paring a set up on my 427 so I have a reason to put the bigger cam in.

 

I believe the GM type computer can't get it to work right at high RPM. you'd probably have to use a holley computer which would drive the price up.

------------------
-Tas
'89 Formula WS-6
[soon to be Torch Red with black hood and headlights =) ]

305, TBI, auto, 14x3 chrome flat based open element with K&N, Milodon 160* thermo, functional Formula hood, cross-flow Flowmaster, '99z28 rear pipes and tips....

Super GRK_Taz World
EFI & Intake Options
AOL IM: superGRtaz
ICQ 82881207

 

No gm ecm has the right injector drivers, to run 4 TBI injectors.

 

It's been done, the 7747 supports 4 injector drivers. This is how DanW has his done, I believe. http://www.fbody.com/members/workman/tech/techindex.htm

------------------
1989 Camaro RS LO3 WCT5 0-60' 2.34 1/4 15.8@87mph
http://350.StreetRacing.org
The posi unit breaker.

 

Get Blown: There are only 2 inj drivers in the 7747.

I've wondered about putting the factory inj pod on the 4bbl holley. Two GM injectors at higher pressure would support the fuel needs and you wouldn't need any extra inj drivers. You also wouldn't have to deal with the rumored lousy holley inj's.

 

not real sure about this theory:
since all you are really looking for the ecm to do is maintain a general air/fuel ratio couldn't you just splice the wires into 2 pairs and run the system that way. i don't think there is any feed back from the injectors so i don't think it would cause any probs.

lata
tim

------------------
91 Camaro RS-LO3,Auto.
14.301 @ 94.39mph

Check Out The East Coast F-Body Nationals Home Page
www.geocities.com/njspeeder

My MAFB.ORG Home Page
www.mycar.net/mafb/registry/detail.cfm?id=299

DSI Racing Home Page

www.geocities.com/foff667

 

I think someone tried splicing the wires to run all four injectors and it didn't work right. Those wires supply a limited amount of current, and at higher rpm, it's not enough to fire all four injectors.

 

thanks andy. I knew this came up before and there were HIGH RPM problems. For most of the cars on this board this wouldn't be an issue. And Dan W is running a performer inake last I heard which is not a high RPM intake.

 

My bad, I'm not sure what DanW did then...

 

When you run the series parallel non sense thing fall apart at 3K rpm, stop by with a few (TBI injectors) and I'll show you on an ecm bench, where your not guessing about what going on.
Like I said no gm ecm has the right drivers for 4 TBI P+Hs

 

I don't know if running a single 4 injector throttle body is different than running two 2-TBI throttle bodies or not. But Turbo City has programmed a chip to run two TBI units.
http://www.turbocity.com/EFIDualDtail.htm

 

I've seen the Turbo City thing and I've wondered about it also. Notice how the plugs for the ECM come out of the side? I wonder if they're using a TPI computer to control them? I thought they (the TPI injectors) had a different impedance?

Ken

 

If its anyone that's figured out all that crap, its them or Howell.

 

You can run EIGHT MPFI injectors with a 7747, like the Edelbrock MPFI conversion does, FYI.

 

I saw where a guy once turned his TBI 2.2 cavalier into a multiport car, he got the multiport head and just spliced onto the injector wires for all 4 wires, if he went from 1 to 4 why can't we go from 2 to 4?

------------------
1989 Pontiac Firebird Formula LO3 Auto
-180 degree stat
-Hooker Cat-Back
*****Possible summer '01 mods*****
Open Element, Auburn Posi, Keyless Entry, wonder Bar off the IROC, 4th gen seats, T/A tail lights

1985 Camaro IROC-Z LB9 Auto
http://www.geocities.com/krt80/

 

because most of us are not computer programers and electrical engineers.

 

Well, as Grumpy mentioned above, he's tested things and the injectors don't work well above 3,000 RPM. I would assume that the duty cycle gets to a point where the injectors need more current, and the single injector drivers just can't handle it.

Just a guess (Grumpy??) but it may be possible to use an opto-device in conjunction with a resistor (the drivers are not current sensing, correct?) to drive a completely seperate set of injector drivers. Hence, as many injectors as you want, I would imagine. The trick is engineering up such a monster.

Ken

 

with a little engineering. anything is possible.

I'll see if i can locate one today at school.