I had planned to do this months ago as some of you will remember. Well, I finally got around to doing it, and here's a brief report as I promised (I would think that this could be applied to the turbo, but the boost curve as another factor to worry about, and me not having any hands on experience on those cars, I will not comment, yet):
OK, the idea is to increase throttle response, and air flow specially at part throttle-low end/midrange. Basically, drill holes in the flap (reducing the flap's mass, and restriction). But to counteract the reduced restriction, the spring tension needs to be backed off (so that the flap opens at nearly the same angle even though there's not as much air pushing on the surface of the flap), which also reduces 'lag', improving throttle response.
Basically, remove, drill, re-attach, and calibrate. For the last step, I used an air/fuel gauge, and a tachometer, ofcourse your ears are another valuable source of input...
I could back off exactly 19 teeth off the spring adjuster on my car, not to mention all the holes that air can now flow through. Throttle response seems improved, and at least in neutral, the mixture can be adjusted right (though it took me about two hours to get it just right). I did my measurements at idle, 2k rpm, 2300rpm, 2500rpm, 2700rpm, 3krpm, and 3200rpm. After re-indexing the flap/potentiometer (the device that's affixed to the top of the flap, that generates the actual electrical signal), everything seems to work fine.
As you know I can't legally drive on the street, but in my driveway the car seems a good bit more responsive, specially of idle, and during transition from part throttle to full throttle. For a grand total investment of (tada) $0, doesn't seem too bad.
If I have time later, I'll tackle some custom DME work, but I'm not sure the returns will be worth it. I'm planning to sell this car, and pick up a 951 as well as a possible other new/new-ish car right now so don't expect anything else too soon.
The only thing to watch for is taking the bolts off that hold the AFM against the airbox (one of them is in a tight spot, I had to 'customize' a cheap no-name bit "driver", second to last picture shows this tool), and to not get any aluminum shavings into the AFM.
PS: I did a write up of this, and the DME mod a couple of months ago for my computer app. project, more info is at my website.
Please reply here instead of e-mails, concerning this and/or the DME mod(s).
Ahmet
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It's all the driver...
My page over1g@hotmail.com
Porsche owners Gallery.../
My 944
[This message has been edited by 1.2gees (edited 06-26-2001).]