Turbo tbi

[White Stripe]

I have a 258 straight 6 with 4.3 gm tbi on my 1977 Toyota landcruiser. I'm a bit dodgy programming but I got it running pretty good. I have a afr gauge on it that has helped me a lot. But I want more. I'm looking into how to fuel a turbo. Option A: Split second makes auxiliary independent injector controllers as an option for about 500 bucks for the biggyback and the injector. So I think that may be an option but in not sure how well the factory pump and factory low fuel pressure would handle a 3Rd injector. Option B: A second option, which I'm unsure about, is installing 5.7 injectors and a 2 bar map sensor. I have the 7747 ecm. So my understanding is that at 50kPa in the fuel table would then really be 100kPa with the 2bar voltage signal. And 100kPa in the fuel tables would be 14.7psi boost. So I would first take my current fuel tables, and reduce the values by 20% since the 5.7 injectors flow roughly 20% more. Then move the 100kPa values to 50, the 50kPa values to 25 etc. Above 50kPa I would have to start fresh with boosted values which should be somewhat linear. I'm planning no more than 10psi of boost, so I would think a 1:1 for would suffice without upgrading the stock gm pump. But it may not support 30psi, so something to keep in mind. What do you guys think of either option? My compression ratio is 7.8:1, so I think this motor would enjoy some forced induction.

[89S10_Project]

Interesting thread- followed for a future project...

Another option I've heard of, though a bit kludgy, is a rising rate fuel pressure regulator.

[buddrow]

The fuel and spark tables dont offer the best resolution for 2,3 bar applications, they are merely sufficient for 1 bar lol. Not saying it won't work, but you may have to fiddle with AE and the like to get driveability somewhat livable.
the 7427 has much better resolution, can support multiport injection with few mods and also can control an E trans.

[White Stripe]

The fuel and spark tables dont offer the best resolution for 2,3 bar applications, they are merely sufficient for 1 bar lol. Not saying it won't work, but you may have to fiddle with AE and the like to get driveability somewhat livable.
the 7427 has much better resolution, can support multiport injection with few mods and also can control an E trans.

Well I think I will throw in a 2bar and see how well I can get it to run naturally aspirated. If it works then move forward. If it doesn't then maybe run a piggyback with auxiliary injector instead.

[White Stripe]

Quick question. I'm cleaning up my na tuning. When I stab the throttle hard I get about 19:1 afr for about 1 second, then it comes back down to 14.7 or a little richer if in person mode. How can I fix the little lean spot? Or is that normal?

[billygraves]

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[Six_Shooter]

Consider poor fuel distribution if you use a TBI blow through set up. Blowing a stream of air onto the fuel will tend to steer fuel into unwanted ports. As Buddrow suggested, use the 7427 and a port fuel set up.

Or better yet, use a '7730 or '7749 with either $58 (stock 2 BAR code), or $59 (modified code to use 3 BAR and a whole slew of other improvements over $58).