Interesting 32v advance/retart timing question
06-13-2006 | 05:45 PM
#16
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Joined: Feb 2003
Posts: 29,956
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From: saratoga, ca
I know you right! however, there was a distinct sound difference, probably due to the out of phase timing of the cams with the .2mm split. I dont know, but i would be curious to know if the block expansion, or belt tension side to side diff, was designed for worst case by the porsche engineers . what I do know is the car ran better and was .3-.7seconds faster on the way home from the race with the cams timed at 2mm a side. my tests going to the track were really disapointing i even tried cheating a little , being in denial, but the results were 6.5 to 6.7 seconds. on the way home, after 2 of the 3 races were 1:40.2 to 1:40.5 vs the first race with stock timing, running 1:41.5 and it feeling and sounding slow! 1 second and the screaming sound of the engine vs the growling sound of the engine, was the difference of the .2mm change making both cams at 2mm lift at 20degrees BTDC.
Later, i went to the dyno, after doing 60-100mph tests all in the 5.8 to 6.1 range and the results were a 15hp gain. sure lots of variables, but the sound alone tells me that setting the cams near equal is a good idea.
Be interesting to see an actual test on this on a dyno on the same day, with no other changes.
Mk
Later, i went to the dyno, after doing 60-100mph tests all in the 5.8 to 6.1 range and the results were a 15hp gain. sure lots of variables, but the sound alone tells me that setting the cams near equal is a good idea.
Be interesting to see an actual test on this on a dyno on the same day, with no other changes.
Mk
Originally Posted by SwayBar
Mark it is too bad you didn't dyno the car after the cam-timing change with the original plug wires. As it is, you really don't know where the hp came from, the cam-timing change, or the new plug wires. If the wires were shot, more than likely that's where the hp came from. I think Louie's dyno chart is much more representative of what one could expect from a cam-timing change.
Nonetheless, you gained 10-15, regardless of where it came from.
The reason for the timing difference on the separate banks is to compensate for the slight discrepancy in belt-tension between the two sides; I would stick to the manuals which were written by the engineers.
Nonetheless, you gained 10-15, regardless of where it came from.
The reason for the timing difference on the separate banks is to compensate for the slight discrepancy in belt-tension between the two sides; I would stick to the manuals which were written by the engineers.
06-13-2006 | 07:09 PM
#17
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Joined: Apr 2006
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From: North Richland Hills, TX
I ran across a write-up from Walley Plumley which he stated an easy way to advance or retard the timing. Here's how I'm going to try it. Set the cams first to factory specs. Then, I will set the crank at 16 degrees in lieu of the required 20 degree position per the shop manuals, and adjust the valve lift to 1.8 for cylinder one and 2.0 for cylinder 6 (for my 1987 S4), then I will get 2 degrees of advance at the cams when the crank is rotated the additional 4 degrees to the 20 degree setting (cams moving at half crank speed). I can then rotate the engine back around a couple of times to the 20 set point and take a reading on the dial indicator. The additional lift at 20 degree crank mark should equal 2 degrees of advance. If you wanted to retard your timing, you would set the crank at 24 degrees and then set the afore-mentioned 1.6 and 2.0 valve settings.
