Thoughts on Throttle bodies and computer comp.

[CJ455]

Looking for thoughts on the computer's (stock in this case but otherwise also) ability to handle increased air flow by way of a larger TB. Is it able to compensate on it own without effecting drivability to point where a retune must be done. As in will the MAF tell it whats going on. Now I understand that this is all within an acceptable spectrum of operation but here's my idea.
Everything about the stock intake system (lower/upper/TB) is significantly restrictive. I've done some things to deal with the manifold portion of this but now it's time for the TB. I know that the 5.8 TB is an easy choice for larger but there's a difference in TPS range? So how about using 2 TB instead of 1 for something like a 4 barrel setup with them synchronized instead of progressive. I would imagine the sudden increase of Air flow from a progressive setup would "shock" the system but maybe not. If they were to open together from Idle to WOT and both be plumed through the single MAF and get sensor and idle air from only 1 TB and the other would just be an extra valve (no sensors) would it run decent? In theory that is?
Or just to make life easy is there a mustang style (single blade) TB with the correct or swappable electronics?

 

[MustangSix]

Don't think of TB's the same way as a carb. In a carb, you have to size the venturis to keep the velocity up. With a TB you are only controlling the pressure drop in the manifold or plenum. Velocity thru the TB is not an issue.

I'm using a single 70mm TB on the crossflow hybrid. Typically, that is large enough for a pretty stout 5.0-5.7 engine. If you were to flow a typical TB at the same pressure drop as a 4bbl carb you might see flow rates of 700-1000 cfm.

As long as the TB weren't so huge that you go from idle vacuum to zero instantly, you would be ok. Basically, any reasonably sized production TB would work fine on our sixes.

As far as the TPS, that also doesn't really matter as long as the output is linear. Most ECU's sense two positions; idle and WOT. Unless you are running pure Alpha-N, all the other calculations are going to be based on rate of change on the TPS, airflow (if mass Air), or manifold pressure (MAP). Factory ECU's are looking for a specific voltage output for those positions, so if you switch to something else you have to recal the ECU.

 

[fordconvert]

I figure if MAP is basically reading ambient at WOT then the TB, inlet, filter system is not restricting things.

 

[CJ455]

I've had the entire EFI intake on a flow bench and each piece: lower, upper, TB take the flow down. The thing I found was that after porting to gain over 50cfm in the head, bolting on the intake and TB knocked the flow all the way back to just 3cfm better than stock.

 

[StrangeRanger]

Other people have played with a larger (2 x 50mm from a truck 302/351) T/B and reported no appreciable gains. The intake manifold would appear to be the bottleneck.

At one time back when Jack was still alive, Clifford was selling a variant of their intake manifold which was machined for injector bungs and had a large single choke T/B that bolted to the carb flange. I seem to recall that the late model Cliffy carb manifolds have the bosses cast in but obviously are not machined. Machining a manifold for the injectors should be no big problem nor should sourcing a larger single T/B from a Mustang or such like. That should alleviate any choke points in the intake

 

[MustangSix]

Those long, tiny runners will always get in the way. They are sized for low rpm torque, not high flow at WOT.

A fabricated tubing intake would certainly flow better and the runners would not need to be as long if you weren't concerned with maximizing low rpm output.

 

[CJ455]

Yea i've been looking at sources for aluminum tubing for fabricating a manifold.
One problem is that in order to clear the fuel rail the runner's cant be shortened by much and still have the plenum in the same location for the the TB and throttle linkage to match up.
another thought i had was switching to a bottom mount fuel injectors and have the runners make the bend next to the head. And then make just over a 90 degree turn into the plenum...this would make for a much shorter runner and would flow alot better.