Throttle body injection ??????'s

Hello all , I have a question on this fuel injection stuff. I would also like to try it but why do you have to switch over all of your heads , intake and stull like that? The reason I'm asking is another one of my jeep buds that I wheel with just finiished a TBI on his 360 and made a aluminum plate to mate up to the throttle body/360 , then he made his own harness to hook up to the ecm/throttle body. The Ecm was programed for the 360 and was done for 100 bucks. What has me confused is the ecm is controlled for firing/injecting by the negative side of coil so it should not matter what the firing order is, correct? As long as the computer is cal'd for a 225 from some engine specs there should not be any reason why we cant install it now? Anyone have any other thoughts on this or looked in to it more? Thanks in advance for any info.

 

You don't have to swap your heads and intake, just build an adapter for the throttle body and adapt the linkage.
Sparky is right the factory ECM doesn't know what to do with the oddfiring order, it thinks the engine is revving up and then slowing down. This came from a holley tech when I asked about it years ago. The megasquirt home built ECM has a feature on it made for an oddfire, it averages the batch of 6 pulses to get a common reading, that way it knows the engine is at a steady rpm.
You can use a crank trigger to balance out the ignition pulses for a factory ECM and trick it into thinking the unit is evenly firing. Mos people think that a throttle body is like a tuned port and fires the injector at a specific time, but it doesn't really do that, its simply a computer contolled fuel metering carburetor that fires when its told and that doesn't necessarily mean that its timed to a specific event in the engines rotation.

 

Mcruff I agree with some of that but if the ecm takes a pulse off the negative/tach side of the coil, that is when the ecm is told to let the injector fire. I guess that is what has me confused so much, so the egine firing order should not matter?? or so that is what I am thinking. Or does the having points not help things out either??? Have patience here to, just trying to get it all straight in my head to see if I might want to give it a shot or not. Thanks in advance for any info.

 

X3 it is the spacing of the fireing that computers cant understand. But as Mcruff pointed out the Megasquirt can take the signals and turn them into usefull ones only to control fuel there is no ECM currently that can control spark in on an oddfire but there are a few that can control the fuel.

Checkout www.msefi.com there is alot of good info on how fuel injection works you dont have to use this sytem but just read some of the info in the megamanual.

 

Not sure might be something to look into.

 

If it is having problems reading the coil/spark pulses, why not run a v-8 cap and ground the two unused plug wires so it reads a constant signal.

 

Sorry, I thought that the odd fire v-6 distributor was the same internally as the v-8 bop distributor with a different cap.

 

I'm thinking Jim Mccarty is approaching it from this angle...what does the firing order matter with TBI? IMO, TBI is simply a glorified carburetor that is electronically controlled. The injector nozzle(s) provides a steady fuel supply, not pulsed, dependent on load. Simply put, a carburetor doesn't care about firing order, a TBI really doesn't either right?

I've always wondered what if you put a 4.3 Chevy TBI on the 225 with a machined adapter. The Megasquirt computer would (should?) accomodate this nicely.

Who has some labratory space open?


..

 

This is all you need to do Jon, the Megasquirt unit just has a way of dealing with an oddfire pulse that the factory GM and Holley/Edelbrock set up does not, the throttlebody itself does'nt matter so long it is not designed for to large of an engine the 4.3 throttle body is what I'm going to use.

 

A GM TBI with the Megasquirt Controller set up for Odd-fire will work to control the fuel on an odd-fire engine. I do not know of an odd-fire computer that will handle spark control.

You are correct in that firing order does not matter when dealing with a TBI. (actually with MPI it is not that important either as it turnes out.) The ony time firing order is important is when you are dealing with a Direct Injection System. I.E. Diesel.

 

That's just it, there is no pulsed fuel with TBI. Multiport is the main issue with pulsed fuel unless you can program it (IE Megasquirt). If a standard carb can provide steady fuel supply for an odd fire, a TBI will do the same. Making it all work is the REAL challenge 8)

TBI unit --> nearly a fool proof carb

 

Actually, technically you do get "pulsed " fuel with a TBI. But because the air/fuel is mixed at the inlet to the manifold it is delivered to the cylinder that is open at the time so it does not matter.

Yes a TBI is the ulimate in computer controlled carbs.