Ok guys, I wanna start looking into some tuning issues I'll be faced with when I get this engine together, eventually.

The intake is an SBC offenhauser cross-ram, with a custom built top plate, and two LOx style throttle bodies mounted sideways(blades sort of split two cylinders per blade, aligned with the runner pairs as evenly as possible.) I'll post a pic sometime soon once I get a camera. The TB's have 55lb'ers installed, for a total of 220lb/hr of injector. I'm putting this on a 350 motor, maybe hyd roller, somthing on the order of 350-400hp, not too radical, but sweeter than a single tbi can support.

My questions are regarding the ecm choices, and tuning problems I'll face with pulsewidths.

I'll most likely either run a '6965 (caprice ecm), or a '6395(late model truck, higher speed aldl?), or since by the time I get it all together, a '747 with the upcoming speedreader board ?

it seems alot of guys getting close to the limits of a single tbi run into the dynamice range limitation, too much fuel at idle, too lean at wot. will I be able to get a stable idle with that much injector with the tbi firing scheme and pulsewidths? will I be able to run async, with any of the above ecms?

what other issues do you guys think I'll come across?

I've already got the drivers covered, I built an external driver board that has 4 tbi injector drivers in it, so its overkill, but keeps the operating temp down per driver, so I'm strictly asking for problems I'll see with software fueling schemes, not so much implementation.

and to ask why.......never seen anyone accomplish it, and its different. I could easily go with a stealthram, but thats for another project. if its not do-able, then maybe I'll learn something. if it works......well...then, I can say i did it (with a little(lot of?) help

thanks,
Joe

 

At this stage of the game, I'd say, SpeedReader, a 7060, or a P4, are the options.

The C3 TBIs just too often seem to be a contest of wills.

From the latest postings on the SpeedReader with it doing MAT/IAT it's even ahead of the 7060.
The only remaining issue, I wonder about, is if the TBI injector firing strategy is a limiting factor. It really shouldn't be, but, without exception it seems like the C3 TBIs just always take so much work to get right.

 

ok, thanks for your opinions Grumpy, i hoped you would give some insight.........

i figure it will be somewhat tough, but i think the speedreader will be a sweet option. Of course, if I pull all the remaining hairs out of my head trying to get it to run, I might also consider putting port injectors into the top plate, and shoot the fuel down the runners. Idle may not be as smooth as firing at the back of the valve, but I've heard that you can acheive better mixture placing fuel at the top of the runner.....I dunno

Thanx again.......

 

I had a SmokeyRam sitting here in the living room for years, thinking about doing a dual TBI with it.

But, after playing with the really large TB on the GN, I noticed that while you can run huge TBs, and still meter fuel, you lose alot in pedal modulation. With the big TB I had, there was little difference in control from about 2/3 throttle and above. It makes things much more like an on and off switch. Plus you have to use the VE table for some VE coming off idle, since it moves soo much air just coming off idle.

For a mid 13 sec car, 2-2" butterflies will get ya there.

Was also thinking of doing 4 port injectors, just one in each corner. While not the best set up, with the 5-7 timing such as it is, but for a street cruiser it might work out well.

Bump come to shove, you can always use something like a VIC if things get too out of line.

So many ideas, not enough cars.....