I'm seriously considering removing the dividing wall in my dual plane manifold to give me more plenum volume and a better top end. I've heard that this would require a big increase in AE pulse width times. I know some of you are using single plane manifolds on TBIs. How much did you have to change the AE numbers? Does it make sense to say that because plenum volume has practically doubled, then the AE injector times should be almost doubled as well? ...just looking for a starting point.

Is there anything else that will be affected?

 

It gets tricky, AE is one of the hardest bits to tune with TBI. FWIW, parts of my AE actualy dropped, others took a HUGE jump. I still don't have it right. You can't say that it will double, I found that the low MAP change area, had major problems if you added any fuel, where as teh large delta TPS area's need HUGE ammounts of extra.

 

Thanks for the insight. I was hoping I'd get your attention I put 65% bigger injectors on last year, re-tuned the VE tables, but didn't touch the AE injector times at all ...so she should be dumping in way more fuel when AE kicks in. That's with the stock manifold though. Car seems much better responsiveness. I'm thinking the AE times are a little lean from the factory. Any thoughts?

 

its hard to say, i would imagine pump shot to WOT would be a hair rich from the factory.

The real balancing act, is keeping it from flooding and almost stalling when you make smaller throttle movements, but getting it to give it enough fuel when you do open it up.

 

On my 305 I used the stock AE settings from an Astro 4.3 and mine kicks no matter what. A little throttle out of a light will spin the tires. Punching it to the floor will leave stripes even at 15 mph or so. The wideband doesn't even hardly fluctuate. This is with 305 injectors at 17 psi, I might add.

 

When you go single plane, or remove some of the dividing wall on a dual plane manifold, doesn't manifold vacuum drop siginifcantly? Obviously you've got it to work, but doesn't the loss in vacuum throw a wrench into the PROM tuning?

 

Why would the vac drop?

 

I assumed that because larger plenum areas cause less vacuum to be delivered to the base of a carb (and don't pull the valves open well at low rpms) that the same effect would occur at the base of the throttle body. And that's why I wondered whether the MAP sensor would register that and therefore there'd be less useful kPa range over which to tune the VE tables. Ofcourse, I don't consider myself an expert at this, so I could be completely off-base, but that's where I'm coming from. Is this wrong?

 

i think the vacuum is more dependent on the cam. i have had 3 manifolds on car(one single plane) and 3 cams. only change in map resulted from cam swap. i believe all 114 LSA.

one thing i do believe is that my AE is more functional(read efficient) with current manifold. with xram it was directly spraying on plenum floor. *** knows how much engine was seeing(pre WB). not the best designed manifold. IMO.