I'm really thinking now.
What if....
You had a primary TBI unit and a secondary TBI unit....
Both having their own ECM...
The units would be set up on a dual carb manifold...
The primary unit would be the Holley 502-6 controlled by the GM ECM.
The secondary unit would be the Holley 502-20s. It would be like
a dual carb setup with the linkages, but each TBI unit would have it's own computer.
It might sound a little crazy, but I think it is possible to work it that way....
Have the same injectors all around.
What does everyone think of that concept?
Is it possible?

 

when you are just driving aroudn on teh primary unit things would be fine, because on a dual set up one carb feeds all 4 holes. it woudl get tricky when you got into the throttle and the secondary tbi opened up. once the second carb opens on a dual set up the laws of physics take over and the front 4cyls draw through the front carb abd the rear 4cyls draw through the rear carb. this woudl be a bit tricky.
i can see what you are thinking, adn i think it can work. getting teh tables right for one system to open up at WOT and for one system to actually tune down at WOT woudl take some work. you would have to sample and compare both systems and lay the tables over each other.
if everything worked out perfect you would have the tables match at WOT and teh ramp up of fuel delivery to be sort of a mirror image of each other under part throttle conditions.


later
tim

 

Primary unit:

 

Secondary unit!!!

 

The wonder of it all is this: This system is designed for the Holley 2x2 TBI ECU system....
Imagine getting that to work with the GM ECM...
Or better yet, getting the secondary TBI unit to work off the Holley 502-6!
It's not a dead subject. You're right Tim. There are things coming about.

 

Ooo I had an idea. What bout a tripple 2 barrel carb intake. Holley sells adapters that lets you put monoblade TBIs on a small 2 barrel carb intake. You could put 3 of those crossfire style TBIs on there. :lala: :hail: TBI 6-pack

 

How about 8 tb's off a crossfire system on an old Haliborne(spelling) fi manifold?

Steve

 

I was thinking conservatively. (If you can call 2 670 CFM TBI units conservative...)
The 2+2 combo may even work.... provided you can drive all the injectors.... However, and another thought to hash around is the 900 CFM unit. Now I got a chance to look at it close up, and it does have an IAC and TPS. The only thing is that it is designed for the Holley ECU.
Is there a way we can convince Holley to construct a 2 barrel 900 CFM TBI unit?
The "secondaries" could be just a second set of butterflies on the back end for more air at WOT.
That makes a lot more sense to me. Why not have larger injectors and the secondary butterflies come open at WOT?
That sounds more feasible and economical too.

 

that is a wiring job i don't even wanna imagine, but, it woudl allow you teh opportunity to run a tpi ecm and sensor set up since everything woudl be on teh same linkage rate.. you woudl only have to run 1 tps and 1 O2, i wonder where you woudl wanna locate teh MAP though, i don't know if those intakes have all equal runners or if they have some sort of shared plain inside.
hmmmm, i think yer on to somethin

later
tim

 

1 Holley 4 barrel TBI w Commander 950 system or the older 4Di system.

1 weekend to install, and setup base fuel maps.

1 weekend to drive and tune, or tune on a chassis dyno with wide band O2 sensor.

DONE


I love reading all these ideas on how to make a silk purse with a sows ear. You are working with outdated ecms that have definite limitations. You can't even run a "real" cam because the ecm will have a fit...

I get this feeling you think the stock ecm is better or more reliable than what the aftermarket has to offer. Why? because it will throw you a trouble code if you screw something up??

Now of course someone will chime in about how they went 13s at 90 mph and blah blah blah with the factory ecm and custom eprom. Yeah I'm sure a person with a background in computers and programming can fiddle with a stock ecm. Is the MAP scale adjustable like a Projection 4di or Commander 950. Can you run 2 or 3 bar map sensors for blowers/tubos with the stock ecm?
Btw 13 aren't all that when you're knocking on 11s door.

I'm venting... is anyone on this site over 30 years old, with enough disposable income to actually "build" a car... or am I the only one?!

 

Of course!
I HAVE built a car. Now what you're talking about would make me rip out what has already been done!
Not trying to make a fight, but when you have something that works, and you want to modify it to make it better, what is wrong with that?
I know I could just give it all up, throw in high-PSI pump and injectors, swap out my ECM... Find some sort of system that will work with my existing motor, swap the CAM once again....
...and end up spending double again what I already have in it.
YES I do hope they achieve something that makes this limited system less limited.
YES I don't want to throw my money down the toilet...
I have a different engine all together.
Maybe if you looked at SOME of the people on here FRMULA, you would see that there are people doing other things than just trying to swap an ECU....
These ideas are born here. You want to shoot them down before any of them are tried? Hmmm, I might as well get a stinking 2002 FireHawk.

 

Boring!

Possibly, not me though. 22, university student.

 

FRMULA, what is it that drives your old factory ECMs ancillary funtions (i.e. cruise control) in your example?

 

I hear ya Joker, I'm over 40 and I'll match disposible income anyday! But there may be a point in FRMULAs venting sooo...the question remains, anyone can throw an aftermarket EFI in anything to run the engine...FRMULA, how does your system control non-engine factory functions?

 

Simple... it doesn't

My car was a daily driver for 5 years. Then the transformation began.

AC? never used it, so out it went
Cruise Control? didn't work since I bought the car in '93 so out it went. Kinda useless items on a rag car anyway.


I built the car for 1/4 mile fun and street use, and it does both quite well. Would I drive it everyday? Hell no, but that's my choice. My plan was always to replace the stock EFI, but that was only because I had definite ideas of what I wanted to do with the car. Laptop tuning is a definite plus.

...as far as the comment that anyone can throw on a aftermarket efi system, I beg to differ. There are people involved in this hobby that lack the mechanical aptitude to assemble a peanut butter and jelley sandwich let alone build a drag car, install an aftermarket efi, and tune it to run on the street/strip.

Anyone who thinks that installing a realiable high-performance efi system is "boring" is a dunce. I am not knocking the STOCK OEM system it is very good at what it does however, it has it's limitations and in my application those limitations were unacceptable.

 

FRMULA, since you don't agree with what we are trying to accomplish here, I really don't know why you even got on this thread. I geuss it's as good a place as any to flame everything and everyone.

 

I have been following the threads about the Turbo City modifications too. Try to get one.

 

now kids, play nice. Otherwise:

 

www.google.com/search?q=site:www.diy-efi.org+dual.TBI+-index

dual TBI stuff from GMECM.

Running 2 ECM's won't work because you can't share sensors. Even if you doubled up on sensors, the ECM's will get confused when they try to make changes to the A/F ratio (or spark or whatever) and the other one does the opposite.


edit by Tas: I'm trying to make it clickable

 

stupid vBulletin

cut and paste

google.com/search?q=site:www.diy-efi.org+dual.TBI+-index

 

you may be able to get aroudn that if you only run 1 knock sensor to whichever ecm is controlling the timing. just hafta figure out if you can put a resistor into teh est and knock module leads to make the othe recm think it is there so it doesn't flip out.

later
tim

 

Heheh, thanks Tas.

NJ, there's other sensors that the ECM needs to operate though, MAP, TPS, temp.

We'll see what I think after I get the test bench built, it might be easier to build an external driver board, maybe not.

 

That's been my hope from the start. My need is more airflow to support a stroker STREET motor for substantially less than the cost of a TPI conversion.