racereno

Alright, here's what I'm thinkin' for a "classic" look (and cheaper, increased airflow):

An Edelbrock 2X4 manifold with adapters, 2 TBIs, and the old oval 2X4 air cleaner. Now I'm pretty green at some of this stuff but wouldn't it be fairly easy to run 2 TBIs in tandem with the stock ECU?

What do you think?

NTChrist

Wow, you just whacked a hornets nest squarely with a stick.

There's been a lot of discussion about this lately, here and on the ECM board. Do a search for "dual TBI" and see what it comes up with. The last I heard about the topic of dual TBI's, was that a few experienced GM ECM-ers couldn't get it to work.

TBI305Camaro

there was something about wiring up injectors....thats why it wouldnt work because you can split the voltage going to them and they would have be to reading the same info or it wouldnt work right

i wish holley would just make a 4 barrel TBI that flowed around 700cfm instead of just the two barrel ones...i still may get the 670cfm i dont know yet

racereno

Man, I see what you mean! Only got a couple of good threads outta that search but they were pretty decent, sometimes heated, discussions. Seems as though a couple of guys were on the verge of making this work but I haven't seen any updates.

chooch-88formula

i have been thinking.... why not have 2 ecms and splice the sensors....some of the sensors you can have 2 of them but the others i think you can splice them and run it to 2 ecms!

Nitroburn

Someone thought of that idea, too. (using two ECMS) But they would never be in sync with one another. There was a thread once about an ECM that could drive 4 injectors and it was fully programable! But the ECM alone was like $700 IIRC.

I have this weird idea of placing two TBI's on top of a 6-71 blower!! (Hummmm... someday.......maybe).

Later,
Mike

AlexJH

Does anyone have the specs on TBI injectors? I'm looking for things like current/voltage/pulsewidths/frequencies they run at.

I'm an electrical engineering student, and it seems to me like you could just use the signal from the ECM to drive some power MOSFETs to supply the appropriate power, insetad of burning out the ECM drivers.

I just got a 747 ecm off Ebay and I'm going to check this out myself, but I don't have a scope, so it would be nice if someone already had the info.

chooch-88formula

i don't think that the ecm's would have to be in perfect sync... part of the lag or responcivness in the tbi's now are due to slow ecm's.... so if there is a little lag between the 2 ecm's i would think it would be ok.... how much time difference could there be? a second? i think it would still work.

racereno

Having read some earlier threads, I don't think two ecms are neccessary. I still think it can be done with one and the addition of a circuit to "normalize" the votages/currents to the injectors or as some have said additional injector drivers. There were a couple of guys who seemed to be close to a solution...we'll see.

Snowdog 91 Formula

Holley makes TBI systems that go all the way to 2000 CFM. The problem is that it requires it's own ECM. I know it can be done, but has anyone ever applied the Holley aftermarket TBI systems and have had luck with it?

Snowdog 91 Formula

Here is 1000CFM:

Snowdog 91 Formula

Here is 2000CFM:

Snowdog 91 Formula

Calibration module:

racereno

Thats right Snowdog and I have one of the new MPFI systems for a non-computer Cutlass I own. But my thoughts are that I have a stroker short block I would like to use on my '91 RS and retain factory ecm functions (cruise control being one of them). Now seeing that this motor would need more airflow I wanted to try simply doubling up on the small injector TBI units with a small ecu/wiring mod rather than the whole TPI conversion deal. Seems like the only issues I've read so far are proper v/c to the injectors and a small issue with the IAC.

Snowdog 91 Formula

Closed Loop kit:

Snowdog 91 Formula

http://www.holley.com/HiOctn/ProdLin...IA/FMSFIA.html

This just gives you a general idea that Holley is serious about TBI.

On that page, you will see quite a bit more including the ECMS.

steve8586iroc

Snowdog, I hate to burst your bubble but the two tb's you have pics of are for multiport efi not tbi, however Holley does make a 900cfm fourbarrel tbi. Go to the Holley site again and look around for the 950Comander ecm and efi systems.

Steve

Snowdog 91 Formula

Yeah I remember posting a picture of the 900 CFM one before.
I just can't find it right now..
I could have sworn that was TBI too.

Snowdog 91 Formula

I found it.
But even so, it still uses that funky 4D / 4Di system ECU thing....
The only ones that hook up to the GM harnesses are the 502-x series....
The 1000/2000 models are without the injector pods.... you add them. (At least that's what I thought at first...)
I read down, and yes it is for MPFI.... Would be kind of cool to add an injector pod to the top of that thing....
I'm sure Holley can do it.
(Or we can?) Hmmmmmmmmmmmmmmmmmmmmmmmmm........
Okay that one has the TPS....
Where is the IAC?
A 1" TBI spacer with IAC in it?
And that funky 4D/4Di harness connector....
(Adapt that to a GM harness? Voltage again?)
I am thinking out loud folx... sorry...
Hmmm the more I look at it... It has the std 4 connector to the injectors... what is that 2 connector thing? Is that IAC?

Snowdog 91 Formula

4 to 4-4?

Looking at this stuff is getting me dizzy....

Russ-So Cal

I think Turbo City is building two tbi set ups. You might checkwww.turbocity.com

racereno

Thanks for the link Russ. That stuff is interesting considering they say they're using GM ECUs. Makes me wonder how they've worked the injector driver deal. That's the sticking point I've run into. All this seems fairly easy with an aftermarket ECU but I want to retain the ancilliary functions of the factory unit (got to have cruise, converter lockup, etc.) and I wonder if thier units support these functions.

kevm14

I think it would be better to use a current amplifier (MOSFETs) to supply the necessary power to each of the 4 injectors...it's sure as hell possible, imo, without going to an expensive and compromised aftermarket ECM.

racereno

That's what I was thinking too Kevin. Just haven't seen anyone do it successfully yet. I think it was JPrevost who had this schem that looks promising.

kevm14

Damn, I had to go to 1600x1200 to view that sucker. In fact, I'm still in it...I can't see what I'm typing! j/k

Anyway, I was looking at the schematic, trying to follow it. I could implement it in one of my ECE CAD programs (EWB, Multisim or even PSpice) to see what happens. I noticed a couple 0-ohm resistors in there. that makes sense

racereno

Sorry for the size Kevin. Thats the size from JP's original post and I just hadn't changed it. Any help on this would be appreciated.

MX265

I really , really wish I did not read this post!!!! I am trying to keep my '89 IROC stock with original 305 TBI, but this is starting to look pretty darn tempting! Good info!

kevm14

I did a search on the LM1949 IC on google and here is what I found (sorry if you already knew this):

The LM1949 linear integrated circuit serves as an excellent control of fuel injector drive circuitry in modern automotive systems. The IC is designed to control an external power NPN Darlington transistor that drives the high current injector solenoid. The current required to open a solenoid is several times greater than the current necessary to merely hold it open; therefore, the LM1949, by directly sensing the actual solenoid current, initially saturates the driver until the "peak" injector current is four times that of the idle or "holding" current (-). This guarantees opening of the injector. The current is then automatically reduced to the sufficient holding level for the duration of the input pulse. In this way, the total power consumed by the system is dramatically reduced. Also, a higher degree of correlation of fuel to the input voltage pulse (or duty cycle) is achieved, since opening and closing delays of the solenoid will be reduced.

Normally powered from a 5V ± 10% supply, the IC is typically operable over the entire temperature range (-55°C to +125°C ambient) with supplies as low as 3 volts. This is particularly useful under "cold crank" conditions when the battery voltage may drop low enough to deregulate the 5-volt power supply.

Sounds like what we need

Russ-So Cal

I think they are using the ecm from the 90-92 speed density tpi's to operate the two tbi units. Of course they have to rewire the plugs since the pin positions for the tbi is different than those for the tpi. What they are doing inessence is making the tpi ecm think the two tbi units are a stock tpi.

racereno

Thanks Kevin, that's excellent info. I haven't seen that before but I agree with your observation.

Russ, from the discussions I've read before I would lean that way too but I don't understand how they convert for the peak and hold TBI injectors.

snflupigus

i can say this again because ive said it before. there is somebody who is making an adapter so that you can put TPI injectors over the tbi unit. that way you could get the tpi ecm, and have 4 injectors... I forgot who it wasand i lost all my links last time my computer crapped on me. force efi maybe? but ive seen em.

spray pattern might not be very good though.

AlexJH

I just ordered some samples from National's website. We'll see if they send them to me or not. Someone on the GMECM list said that Holley, Accel, etc. were buying all of them, not leaving any for hobbyists. I'd appreciate it if other people didn't order any samples for a couple of weeks, I'm hoping to slip under the radar. If all of a sudden, they get 100 sample requests for the 1949, they might get a bit suspicious.

Alex

racereno

:sillylol: Hold me back!

JPrevost

Yeah, I told you that and I heard that from Grumpy. I haven't been able to locate any of the drivers so I might end up taking some out of another ecm, just need to be careful not to burn up the ICs.
Russ, TPI ecm won't run 4 peak and hold injectors. I believe the only ecm that came with peak and holds was the sy/ty 4.3 turbo's which has pretty beefy injector drivers. Still not sure if that is what turbocity WAS using. Turbocity stopped doing the TBI kits and such because no interest. Everybody was either too stupid to understand EFI or they wanted to go all out with the newer multi-port EFI kits.
Grumpy is working on a cheap mosfet circuit (if he isn't already done testing it) and it's suposed to be pretty simple.
I wouldn't want to run TPI injectors over a TB unit for 2 reasons. One is that they would have to be HUGE since instead of having 8 injectors for the engine, it would need to flow the same amount of fuel for 4 (not exactly the same but close enough). Next problem is the fuel pressure. Have fun running some high fuel pressure to some custom injector pod, just don't use rubber line. Oh yeah, and the larger injectors would need to be peak and holds anyways because they don't make standard saturated injectors that flow the level you would need.
My final say is this: Run a GM_ecm with an external injector driver board, end of story. The only trouble now is finding those darn injector driver ICs.

snflupigus

now stop me if im just being dumb.


Ive seen electronics books etc... there is always something that is very very similar when it comes to electronic components. If they have canceled one item, there has to be at least 10 others that have slightly different function or specs but does the same thing. And they are usually right next to eachother in the parts lists. Has anybody gone to a wholesale electronics supplier and asked for something similar etc.???

Isnt there a way to get in touch with somebody who could make a few more runs of them? Or get in touch with somebody that has more. I find it VERY hard to beleive that Holley or anybody would be able to 'buy up' ALL of one electronic peice.

I guess i just cant beleive that these things are SO rare, and SO unique.

racereno

Thanks for checking in JP. I think you and Grumpy are close to working this thing out in the way I had theorized. I think the potential for increasing airflow beyond TPI for less $$$ is very good.

Buck268

Sorry that I cant really add anything (I am still pretty new to cars), but its great to see some truely tech discussion on here! :hail: I hope that someone does eventually get this to work, it would be pretty sweet!

AlexJH

<grin> Don't talk to me about MOSFETs, I fried 4 of them in an amplifier my group made, about 10 mins before we presented the project to our professors. Doh!

Here's the National automotive website:

http://www.national.com/catalog/Automotive.html

Lots of neat things here.

And here's a quote from a EFI FAQ:

"How do I drive a 2ohm injector? Older GMs use a Nat'l Semi LM1949 with a few support chips. Another option is an MTP3055EL, clamp zener, and a big resistor. The resistor is necessary to prevent roasting of the injectors (ref Dale Ulan -- DIY_EFI email on 8 Feb 95). "

AlexJH

Woohoo! 3-15 days from a warehouse in Singapore. :lala:

------------------
Hi Alex,

Thank you for your sample order from National Semiconductor
for the following device.

NSID: LM1949N
Quantity: 4
-------------------

racereno

Go Alex!:hail:

RacerXWS6

for your viewing pleasure..... check the link, but theyve even stopped making them.


http://www.turbocity.com/EFIDualDtail.htm

racereno

Yeah Racer that's what JP told us earlier and that's OK. This, to me, is the type of setup that ought to be a DIY deal. We've come to the conclusion, I think, that the only thing needed for this is an external injector driver (more or less). And I would gladly pay for plans or a kit for this. I'm a dope so far on this stuff but we have some extremely bright people in our midst so I've got my fingers crossed!

RacerXWS6

I have no idea how that did that..... I do have one thing that might help. Anyone thought about emailing Turbo City to see if theyll share exactly how they made it work? I mean come on since theyre no longer selling them, they should fess up to how they worked it all out, or if they even did.

racereno

:sillylol: I know what you mean Racer, Go for it!

RacerXWS6

While Im waiting on a reply from them heres the harness they make to run a dual TBI set up maybe one of you can make heads or tales from it...

RacerXWS6

ok email sent..... whatcha think?

I know at one time your site said you had quit making this system, but I dont see that now. Some of us have been looking into this type of system. We keep running into problems trying to figure how you can actually run both TBI units off of one ECM, and make it work properly. How did you solve this problem? Were looking in several directions as hobbyists, not to sell or market. I want to make that perfectly clear.. no one is trying to step on anyones toes here. Heres something were looking into, and maybe you can at the very least let me know if were going in the proper direction theoretically for parts to use.

The LM1949 linear integrated circuit serves as an excellent control of fuel injector drive circuitry in modern automotive systems. The IC is designed to control an external power NPN Darlington transistor that drives the high current injector solenoid. The current required to open a solenoid is several times greater than the current necessary to merely hold it open; therefore, the LM1949, by directly sensing the actual solenoid current, initially saturates the driver until the "peak" injector current is four times that of the idle or "holding" current (-). This guarantees opening of the injector. The current is then automatically reduced to the sufficient holding level for the duration of the input pulse. In this way, the total power consumed by the system is dramatically reduced. Also, a higher degree of correlation of fuel to the input voltage pulse (or duty cycle) is achieved, since opening and closing delays of the solenoid will be reduced.

Normally powered from a 5V ± 10% supply, the IC is typically operable over the entire temperature range (-55°C to +125°C ambient) with supplies as low as 3 volts. This is particularly useful under "cold crank" conditions when the battery voltage may drop low enough to deregulate the 5-volt power supply.

I know Holley is making what they call a Primary, and Secondary TBI units, which is operated by their ECM, and its a nice little setup, but Id like to know more about useing a GM ECM currently in my TBI car. To see what weve been chatting about please feel free to join www.thirdgen.org, and check out the TBI board. You can find this very discussion under the X2 TBI thread. I appreciate any information youre willing to share with us in our quest to stuff TBI down the TPI owners throats as a viable performance option.

Thank you
Andre Gavion
Pres. Carolina Third Gens

JPrevost

Well I'm about 6 months ahead of you. I already e-mailed them and talked to them on the phone. They won't disclose any of the information for buisness and legal reasons. It's but I already know how to do the dual TBI. It's the same as running a 4 barrel TBI system. If I can get a hold of normal injector driver ICs then there isn't a problem with any of this. It's getting a hold of THEM that is the tough part and then making sure you've got enough smarts/knowledge to tune a 2xtbi setup.

snflupigus

cmon how hard could it be??

Snowdog 91 Formula

I am wondering if anyone has seen/tried this combination...
It looks pretty good, but I am wondering if it would be worthwhile?
Edelbrock TBI conversion system
Would this be practical?
I know after looking at it, it wouldn't be for me, because of the current modifications of my vehicle. I have to figure out some other route to go for myself.
However, for people with stock 305 TBI systems, would this be a good way for them to go? Has anyone tried or done it?

JPrevost

It's been around for a long time and I'm going to be tuning a pickup that has it on a 350 with vette heads. I don't know how they did it exactly but I think they either just used one injector driver to power the 8 sat. injectors as in a batch fire mode OR they would have had to do some fancy tuning with the BPW and other variables to get it to run with both injector drivers firing all 8 (twice a rev isn't batch fire). I'm pretty sure they just didn't use one of the injector drivers because last time I "looked" at the edelbrock eprom it had a stock 135 BPW value and everything looked pretty normal.