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Jerry DeMoss

Dual spfi on ea81 dual carb manifold?

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Just a thought here and I was just wondering what some of the spfi guru's thought about it.Wondered if it was possible and as I doubt it really is needed I thought it was fun to think about.Anyone else toying with that same idea or others thought of it before?

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Does the SPFI use a different manifold? I thought it had a different bolt pattern for the TB. Getting a computer to read the two TB's and run both injectors would be interesting I would think...

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You would have to run it with MegaSquirt.... I guess you would run it like a bank fired MPFI. Only one of the TPS's would be hooked up of course. It would probably work, but it would require a lot of tuning and tweaking. Personally I would just use a larger TB off some other vehicle and custom build a manifold.

 

GD

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Does the SPFI use a different manifold? I thought it had a different bolt pattern for the TB. Getting a computer to read the two TB's and run both injectors would be interesting I would think...

 

Yeah, the SPFI TB bolt pattern is not the same as a carb. You'd have to make a manifold. It MIGHT work to have just one of the ECMs running the spark, but I'm not sure. Not sure if it's possible to hook up two ECMs to the same crank angle sensor in the disty. As far as hooking up other sensors and stuff, I think it's doable, but it would not be easy.

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A custom manifold with not so sharp angles and a bigger TB with maybe two TB injectors might be something to think about. I was going to setup a totally custom megasquirt system for my EA81 with mazda parts and a SC for some boost, but I've changed my mind and I'm wanting to go down the root of high comp N/A with twin webers and MSD ignition.

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The SPFI TB is already quite large. I'd imagine with two SPFI TBs on it, you'd get pretty large sensitivity with regards to throttle position. Probably wouldn't be streetable.

 

Yeah, and as GD said, Megasquirt would pretty much be a requirement.

 

It'd probably be more beneficial to find a larger TB with a TBI and make a adapter plate to bolt it up. GM from the 80s/early 90s has quite a few TBI setups. Should be able to find what you want there.

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Great input guys.It was really an idea more than anything cause I figured that MS would be the way to go with that.Allthough very different I still think twin webers sound better and better ,but at the altitude we live at here in colorado carbs can be a bit of a pain.I am pretty sure I am going to convert my hatch to spfi.

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