Need help paring down a 3.6L C2 stock intake to bare min w/ Motec

jeffstev · 03-24-2007, 10:57 PM

I am considering selling my 3006 TWM throttle bodies on my race engine to 1) help pay to fix my front end from the crash last season and 2) to further comply w/ a new class we've created in the PRC called GT-L; Intakes on 3.6L engines need to be of the stock C2 variety for this class.

I will be replacing them w/ a stock C2 intake system and controlling everything w/ Motec M48. I want to eliminate all the noodles and crap that is crawling all over this system and get down to the bare bones. I assume I can remove almost everything and plug all the holes, remove the air box and then put on a Zucz air filter or equiv. I have a Motec map I used on a different stock 3.6 as a starting point.

The intake I have is an older aluminum intake and it has a flap valve on the lower portion of the plenum. With the Motronic brain, I'm sure that valve opens/closes at some predetermined RPM and/or throttle position to induce (or reduce) chamber resonance and increase power? I know I have outputs on the Motec that could control this valve but my question is at what RPM/TP might you open it for max power? I'm sure it depends on a ton of variables but I need a starting place!

Anyone have any experience in this area??

Jeff

Porschekid962 · Porschekid962's Garage

Sell the Motec while you are at it and save some more money. You dont need it to operate the engine unless you feel like logging data. Just get a custom chip for the stock motronics and call it a day.

Bill Verburg · Bill Verburg's Garage

964 and 993 use 2 slightly different strategies
early 964 w/ aluminum intakes
closed from 0 - 5500 rpm, open above that. On trailing throttle it closes below 5400rpm. Closure by spring, opened by vacuum.

they also open then close briefly at each start.

993 (and I believe late 964 w/ plastic intakes but I can't find the documentation for the 964s)
open from 0 - 3500 and from 5520 - 6640

closed from 3500 - 5520 when throttle opening is > 60&deg

again they cycle at each start.

There are 2 pipes connecting the 2 sides of the intake. The larger is always open and utilized. The smaller is selectively
utilized to enhance torque in a given rpm range.

philipguziec · 03-25-2007, 06:43 AM

Why not make two dyno runs, one with the valve open, one with it closed? You can pick the switch point where the curves cross with your cams, etc. based on the differences in the curves, or just disable it in one position or the other.

jeffstev · 03-25-2007, 10:04 AM

Thanks for the info Bill! That's exactly what I was looking for.

To the other comments, I've become used to the Motec unit and really like it, it integrates well w/ my AiM systems AND I dont even have a motronic unit or stock wiring harness, so it would cost time and money to switch everything. And I may go down to a dyno shop and do some pulls once everything is installed.

Any stabs at what kind of hp reduction this change would induce, assuming I can tune for max hp w/ this intake?

Jeff

Mahler9th · 03-25-2007, 11:25 AM

Jeff: I have all of the information you need. I run a similar intake, and I control the flapper door. Mat and I have it all figured out... which parts you need, which parts you don't, throttle linkage, cold air box air box design, and everything else. Bill's information is for a bone stock motronic car, and you can do better and still be legal. I am willing to help, until I build an engine for GTL, so get it while its hot!

jeffstev · 03-26-2007, 10:22 AM

I've looked at your motor a dozen times but never realized you had this injection system on it! Haltec on yours? mapping? Let's share info here - that way other folks can benefit from what we know.

Jeff

Mahler9th · 03-26-2007, 12:53 PM

One benefit of a system like Haltech, Motec or DTA is that you can dial in on the track in real driving conditions. I would guess that mapping up a chip on a chassis dyno would yield less optimal results. If you wanna read about the theory of the 993 intake's flapper door, you can ready the white paper on 993 technology that was published in Pano when the cars first came out. of course the ultimate rpm points for flapper actuation in our situations is different because the parts are different leading up to the TB, and the air flow is different getting to the air filter, and likely the cams are different. You can optimize the rpm setpoints by dialing in at the track with a good recording uego and Mr. Motec.