Throttle body injection ??????'s

Oh, Yup, AFIK there is no GM computer known to man that will run an odd fire (properly).

 

Correct, unless the ECU can average the pulses received from the tach signal. This is what Megasquirt does to maintain the fuel flow on an odd-fire engine.

 

OK, now we'er getting somewhere. Thanks sparky and mcruff for getting me the odd fire info. I did some more research and as it seems the trick of this is to get the 150 degree firing order to get to 3 evenly spaced ones. I emailed John over at Custom EFIS and he explained the finer points of the matter. He said I had 2 options; 1) to put GM EFI on an odd fire engine is to use a crank mounted trigger wheel with 3 evenly spaced trigger magnets such as that sold by MSD. (around 250.00) and 2)Another possibility is to add the trigger wheel to the distributor and this is something I could do with my milling machine if I had the distributor here to work with. So with those being said it makes me go hmmmmmmmm????? This sounds better to me than the megasquirt, just easier to plug and play than all the programming. Plus every thing is more readily available at parts store and u-pull it yards ie; ecm's O2 sensors , map sensors, throttle bodies and so on.

 

But you are still only controlling fuel not spak why go through all that hassale of milling and fitting when MS will just take the signal from your tach wire or points and run the fuel for you and yo ucan tune it for optimum performance with a sock ecu off of a GM it is calibrated for GM and is not garantead to run the motor that well.

 

Well green71jeep I have not done to much research on the MS. I have had more dealings with TBI from all my 258,304,360 and 401 buddies. Plus I should have explained that I was talking about 2 different systems when in some of the post's. Some buds are using howells fuel system while others use custom efis systems. The system I seen from howell uses a negative tach signal to send to the ecm but Custom efis actually uses the stock spark controler piece which is where the ESD trigger device comes from, that is how John from custom efis sets his up. While both of these systems work great or at least the folks who have them say that, the more feasible option would be custom efis with the controler already in system. That way the ecm will pick up the pulses from the esd trigger device or the milled one he would try to make on the dist. itself. All though with this much being said , heck, might be cheaper to just buy a complete 4.3 liter from junk yard with harness and ecm and install it, LOL.

 

You are probally right if you can find a good running complete 4.3 it would probally be cheaper to do that.
Question did custom efi tell you that you could control spark on the 225 odd fire because he told me it was not possible by any means and from all the reasearch I have done tells me the same thing.
most of the after market systems can control fuel in the 225 but most need to see an even fire pulse and as you said you can put crank trigger wheel or there has been guys that have simply put an even fire modual in with the odd fire in the HEI there is many ways to accomplishj what you want to do if it is just controlling fuel.

 

The other way (or should I say another?) to do it is to modify the harmonic balancer (and use an additional sensor) to provide a 3x signal to the ECM. Basically you'd be creating a signal that would imitate the ignition signal on a stock 4.3 engine. McRuff and I were hoping to go somewhere with this a loooooong time ago but I sold my 225 and have gone to the dark side with a Chevy engine.

 

Hey Green71,

Have you checked to see if Megasquirt-N-Spark will do spark for an oddfire? I do know they have spark for evenfires with the Megasquirt system. I wish Ultra MegaSquirt would come out, I have a Jeep and a Datsun I would like to put that on. It should have spark built in natively, along with wideband O2 and a bunch of other stuff.

 

Mark..
I have check MSNS Extras and no it still wont work on an odd fire to control spark.
The UMS will be great but unfortinatelly I think it is a aways off.

 

Well mruta its looking more and more like both of us be going to the dark side and having chevy engines, LOL. Just dont want to have to change motors as long as the 225 still runs good, have a lot of time and money in it to just dump it. But more research shows that a 4.3 will bolt up to my sm420 soooooooooo as they say in the wheeling world "built jeep tough with chevy parts", LOL

 

I hate to add another option to the mix, but my Holley Pro-Jection system works just fine on my 225. The only complaint I have is it throws too much fuel at WOT. If you back off the stupid pedal a hare it goes away (just need to adjust the throttle linkage). I found an old Analog system on E-bay for $250 that had never been used. Everyone said it wouldn't work, so I had to give it a try.
I've run it for about a year and it still purrs. Only thing is you have to re-adjust the settings when the weather gets cold/hot. Anyone with a Jeep will be constantly playing with them anyhow so that's not a problem. Definately cheaper than a 4.3 swap or going throught the trouble of trying to convert another system.

 

My pro-jection on my 225 works fine too. Someday I might find a closed loop kit for it. The holley manifold fits too.

 

It has an analog module with potentiometers for manual adjustments. The newer Digital systems require a Lap top and program for adjustments. Got an analog system on the shelf waiting to go on something. May end up on the 231 when my daughter inherits it. Nickmil.

 

Just out of curiosity...whats the smallest v6 gm made that used throttle body injection? Also coulndt you use smaller injectors on the tbi to compensate for the size problem of using the 4.3 tbi? Just a thought.

 

The size of the 4.3 throttle body or injectors isn't a problem. The way the 4.3 ECM interprets the ignition signal from the 225's distributor is the problem.

 

I understand the oddfire thing...i know the megasquirt will run oddfire. Just thought the 4.3 tbi might be to big for a 3.8 so was thinking smaller injectors could compensate for that. Also read some where that in like 87-9? gm used two different size injectors on thier tbi for emission purpose.