TBI Thoughts

I have had my megasquirt unit assembled and tested sitting in my garage for more than 4-5 years, time to get serious about it!
I have a GM TBI unit from s 4.3 v6 and the full wiring harness from under the hood and all the sensors and such.
I want to build this setup so it can be duplicated by all on here including the tuning program on the cheap.
Right now I have $45 in the TBI and wiring setup. My main concern is the factory intake, I can build a nice adapter but do you guys think the factory 2barrel intake will work ok?
If this will work OK it would cut cost dramatically for the whole setup.
Just add an o2 sensor, fuel pump and remake the wiring harness to fit the jeep and then deal with air cleaner setup.
I will not be tuning this myself but have a friend who is a genius with this stuff who can do the tuning in probably under an hour and then I could post it for others to use later on. He runs a megasquirt on a 1200+ HP blown big block race car and on his RZ350 and RZ500 Yamahas, these are both 2 stroke bikes and boy do they fly now. He is quite good at tuning with fuel injection as well as carbs. Ideas??

 

Is this going on an odd fire :v6:?

 

I would expect so. MegaSquirt works fine on odd-fire motors.

I think you would have a hard time justfying a different manifold from the factory 2G manifold on the basis of performance. This is the Rochester small 2V pattern, no? The same as the Carter BBD? I don't think there is any inexpensive TBI-to-manifold adapter for that pattern. I made one from a chunk of scrap aluminum, since the cheapest I could find was sold by AFI - http://www.affordable-fuel-injectio...dapter_Plate_For_Two_Barrel_Intake-49-23.html ... I think Bill USN-1 of Hamilton Fuel Injection is also making adapters.

One reason to go to a 4V aftermarket manifold for a 225 is ... expense of the adapter. You can buy a GM TBI to 4V adapter for a reasonable cost http://www.summitracing.com/parts/trd-2210/overview/ which may offset the cost of the manifold switch.

Too bad my Ford 3.8L CFI throttle body does not get any love. It will bolt to a 2G manifold with a $13 adapter from Speedway http://www.speedwaymotors.com/Holle...D5HqreTDgQivdCmI3ayJ4-UVcHvKikfSi5xoCQRrw_wcB or to a Carter BBD manifold with a $20 adapter from Summit http://www.summitracing.com/parts/trd-2086 (may be the same pattern...)

 

Well of course!
My 71 Buick 225 oddfire

 

I though I read somewhere about an issue with the dual plane manifold

 

I was thinking about this past week. What about a plastic carb adapter for the stock intake on the v6? I could see the heat and ethanol potentially being a issue, or another issue I am not aware of.

I was also thinking if the plastic was a issue, make a casting of it. However, that thought process is from someone with no machining tools and other things to do first.

For most of the jeep guys here, I think the factory intake would work fine. If you had a hotter V6 I could see wanting to go with the dual plane manifold.

 

Just a question, why would you want a plastic adapter over an aluminum one?

 

For an adapter that can adapt, insulate and is resistant to most fuels and chemicals Phenolic resin based materials are by far the best.......same old yellowish brown layered material used in old radio & TV chassis.
Aluminum is the worst thermal insulator while wood is really the best..............Polymer's could also be considered but Phenolic's far surpass all the needs of all the other choices for Carburetor type spacer uses..........easy to find in sheet form and various thickness's at most Plastic houses.

 

The easiest is to use an aluminum adapter with phenolic gaskets to seal and insulate.
Remember that almost all boughten adapters are aluminum, why reinvent the wheel, just sayin!

 

I hear you!............Marine grade plywood treated with a fuel resistant resin.

 

I agree aluminum would be better if I had access to a mill and the know how. Seems to be a hard thing to learn these days. I looked for classes.


However, I do not know any machining stuff but I do know quite a few people who are proficient at cad, and my thought was after looking into the cost of someone to make a aluminum adapter via machining. One might try looking into alternative ways like into a shop with a Cnc machine to make the piece or even 3-d printer. If you can make a ar lower why not.

That was my thought process.

I didn't realize you could buy phenolic plastics in pieces or use a marine grade plywood. Interesting, I always like this forum makes me think.

 

You don't need a mill to make an adapter. I made my TBI-to-258 adapter with a drill press and die grinder.



I had thought that insulating the TB from the manifold is not needed with fuel injection. This was a carburetor thing, where gasoline sits in a float bowl and moves through the carburetor at atmospheric pressure or lower. A throttle body holds the gasoline at high pressure until it is atomized into the air stream for delivery to the cylinders. Looking at factory setups, you typically do not see the thick plastic (phenolic) or paper insulation that you see under carburetors.

Aluminum has an obvious advantage structurally, if you need to make blind threaded holes to secure the carb or adapter.

 

A little terminology confusion here..."dual plane" refers to the intake design. It simply means that each barrel of the carb feeds alternate cylinders on either side of the engine. On a v8, each barrel would feed 2 cylinders on each side. On the V6, it's 2 and 1.
Most aftermarket intakes are this way, too, but some are one big opening that feeds all cylinders-this is better for high RPM use.
Regarding the material of the carb adapter-Tim is correct about phenolic plastic or wood. Those are used to insulate the carb from engine heat. On a TBI, there's no fuel bowl and there's a constant flow of fuel so heat becomes less of a problem.

 

If you used a 2V TB on a 4V manifold, I'd think you'd want to pick a manifold with a plenum underneath the carburetor. Regardless, it's not ideal, since the manifold was designed to flow at high volume from the secondaries, which won't be there. So, do you put the TB where the primaries would be, where the secondaries would be, or somewhere between? With the original 2V manifold, there's no question what to do.

Realize that these TBs have fairly large barrels, because they do not have to maintain a high vacuum in order to power the carburetor fuel circuits. Manifold vacuum is simply an input to the computer, and as long as you can reliably and accurately measure a change in manifold air pressure (MAP) over normal operating range, then who cares how much vacuum there is. Also, this means that the TBs have a much higher CFM rating than a carburetor for a similar application. So performance should improve some. You might not see much of that performance increase if the original manifold is as restrictive as the original carburetor.

 

My idea was to make the adapter out of aluminum and see if I could make them cheap enough to offer them for say $35 including shipping and send the tuning program via email.

 

Possibly!!
He's even got access to a cnc laser now and a plasma table.

 

He's working on it Howard.
Waiting on a new toy really sucks!