L67 TB modded to fit L36...finally, proof of benefit! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
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Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 05-29-2007, 05:11 PM   #1
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Default L67 TB modded to fit L36...finally, proof of benefit!

In this thread, I talked about the fact that I didn't find any apparent benefit at WOT of the L67 TB (70mm bore) I modded to fit my L36 (had a 65mm bore TB stock):

Well, it turns out the benefit is, as I should have at first realized, at LESS than WOT:
Click the image to open in full size.

Torque is directly related to VE, and VE increases with higher MAP value. Thus, with the bigger bore TB, I get higher MAP faster, thus more torque more quickly. This is the very definition of "better throttle response."

Note: In order to realize this benefit, I had to mess around with a table in the PCM that limits the positive change allowed in MAF readings over time. The graph above reflects the stock TB versus the L67 modded TB with that table altered. This MAF-limiting table is why, in previous reporting, I noted the improved throttle response with the L67 TB only when the MAF sensor was disconnected (and the PCM was going by the MAP sensor only).

Note 2: Changing said table did not improve VE at WOT, so there is no "peak WOT torque" or "peak WOT hp" gain...however, this clearly benefits my launch and my freeway passing abilities

I'm working on a home-made mod now involving a spare UIM and about $20 worth of RTV that I expect will give me even better throttle response
2004 Buick Lesabre Limited, Gran Touring; Bone Stock

1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...
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