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MAP tuning with individual runner throttle bodies
https://slantsix.org/forum/viewtopic.php?t=20505		 Page 1 of 1
Author:  Patrick Devlin [ Thu Oct 26, 2006 3:51 pm ]
Post subject:  MAP tuning with individual runner throttle bodies
Recently I have been thinking again about individual runner throttle body fuel injection. For example, setups like 3 TWM DCOE-style throttle bodies on a triple Weber slant six manifold.

What I have been wondering (and I have researched as best I can on the web and in books I have) is can I use MAP sensor with individual runner throttle bodies and be able to tune the car for down low (idle and low RPM) running?

From what I understand, because each of the throttle plates (6 in all) act as a small vacuum leak it is hard to get accurate manifold pressure readings, even with a shared plenum tee'd into each runner.

So, anybody who is using an individual runner manifold setup for EFI, how do you tune it? (any input from Tom Drake?)
Author:  Joshie225 [ Thu Oct 26, 2006 4:46 pm ]
Post subject: 
BMW has used a lot of individual throttles on 'M' engines, but they also use a mass air flow sensor. Getting individual throttle injection to idle well with MAP load sensing isn't easy. This is why Electromotive came up with the blend software that uses both throttle position and MAP load sensing. As you mentioned you can build a little plenum and connect it to each runner, but the signal is still not very accurate for the reason you already stated. My take is if you want individual throttle injection use either mass air flow load sensing, throw down for Electromotive engine management or live with Alpha-N throttle position load sensing.

edit

Have you read this? http://sdsefi.com/techtps.htm
Author:  Patrick Devlin [ Thu Oct 26, 2006 5:08 pm ]
Post subject: 
Thanks for the reply Josh. Yes, I had read that on SDS's website...that's why I figured if SDS wasn't using MAP sensing for that type of application there must be a reason. But I didn't know about about Electromotive's blend software. Interesting stuff I will try to find out more about. Right now I have the parts to use a Clifford 4500-WH intake (the kind with cast in bungs) and a Ford 4.6 TB, but I find it hard to resist an individual throttle setup. I saw that PP&R out of Austrailia is selling a new tripple Weber intake at a good price. I believe th PP&R is Rayman440 of Moparmarket's company. I emailed him recently to get specs on his tripple Weber manifold, and here's what he had to say:
Quote:
The triple weber intake we make has a tapered runner design from approx 2 1/4' @ the carb end to slightly smaller than port size @ the cylinder head end to accomodate for porting and gasket matching. The runner length is 5 3/4' long. Thanks for your email, I hope this is useful.
The runner length is comparable and even longer than some of the runners on the Clifford intake (the middle runners on the Cliford are about 5" to the plenum), so I do not think low end torque should be a problem with that manifold.

I think I would use the smallest TBs available for that manifold, which seem to be 40mm.

The only things stopping me from going that route are cost, of course, and the possibility that it'll never run right. Personally, I don't mind having a car that I have to tinker with if it is not my daily driver...that is a most of the fun of it for me.
Author:  Matt Cramer [ Fri Oct 27, 2006 6:20 pm ]
Post subject: 
There's a lot of guys on the Megasquirt forums who just use a MAP line plumbed to draw a signal from all the throttle bodies at once. Works pretty well unless you have a really aggressive cam, in which case you'd have to use either alpha-N or a hybrid of alpha-N and MAP.
Author:  sandy in BC [ Fri Oct 27, 2006 7:24 pm ]
Post subject: 
So....why not use a MAF sensor? It seems so much easier to get a ecu signal you can use. MAP sensors have their place(I use MAP) but your idea seems to scream MAF.
Author:  Patrick Devlin [ Sun Oct 29, 2006 4:50 pm ]
Post subject: 
Yeah, this is why I'm asking the question. Maybe MAF is best for this kind of setup, especially since that's what the OEMs seem to do. I just want to know how people have gotten around this particular problem. It seems to me that even though individual runners/individual throttle plates might be the ideal theoretical intake system (for maximum power), there are good reasons for a single throttle body intake: that is, strong vacuum signal for good idle and part throttle tuning.

Anybody have the details on the Drakes' setup in the Simca? (I could email them, but if it's on here then everybody can see.) And I realize the Simca is a drag car and mostly concerned with wide open throttle running, but I'm still curious as to how it was tuned.
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