JBenko
Enthusiast
\'99 ACR vs. \'01 ACR - Cams, lying dynos, Corsa
A few weeks ago my buddy Smas posted that he and I ran our ACRs against each other and the '99 was a little quicker, maybe a car length and a half, from 30mph - 120mph than the '01. Both cars were absolutely bone stock.
Being curious as we were about this we had both cars dyno'ed and we were suprised when the '99 pulled 393 hp (corrected) and the '01 pulled 406 hp. The '99 pulled 446 ft/lbs and the '02 pulled 444. Both cars had very similar shaped curves on the graphs, and relatively the same amplitude of noise in the plots.
I know at this point you are thinking driver differences but these were multiple runs, from a rolling start, and I can assure you we are both very competative with each other.
I showed the dyno slips to John Archer last week and his first question was did we check the tire pressure before the pulls. I answered no, but that they were probably pretty close to each other. He then asked if we measured to see that the cars were on the dyno at the same EXACT spot when they ran (side to side, front to back). Again, no, not exactly. John said that he has seen dyno's show as much as 25 hp difference depending on tire pressure and where on the dyno the run was made. This would seem to explain how the '99 could pull ahead of the '01.
Just for fun I was on the Mopar site and saw that the '97, '98, and '99 cars all show the same part number for the cam (4763-708). The '00 and later all show a different part number (5037-151AA). According to my manual, and some research on this site the difference is that the earlier cam has 66deg of overlap and the later cam has 60deg. "Cream-Puffs", no. Different, yes.
Last note in this long post - I added a Corsa cat back exhaust, and pulled the cats on the '99 car last week. We ran the cars again today and the '99 pulls another car length or so on the '01. Seems to have made a reasonably decent improvement.
A few weeks ago my buddy Smas posted that he and I ran our ACRs against each other and the '99 was a little quicker, maybe a car length and a half, from 30mph - 120mph than the '01. Both cars were absolutely bone stock.
Being curious as we were about this we had both cars dyno'ed and we were suprised when the '99 pulled 393 hp (corrected) and the '01 pulled 406 hp. The '99 pulled 446 ft/lbs and the '02 pulled 444. Both cars had very similar shaped curves on the graphs, and relatively the same amplitude of noise in the plots.
I know at this point you are thinking driver differences but these were multiple runs, from a rolling start, and I can assure you we are both very competative with each other.
I showed the dyno slips to John Archer last week and his first question was did we check the tire pressure before the pulls. I answered no, but that they were probably pretty close to each other. He then asked if we measured to see that the cars were on the dyno at the same EXACT spot when they ran (side to side, front to back). Again, no, not exactly. John said that he has seen dyno's show as much as 25 hp difference depending on tire pressure and where on the dyno the run was made. This would seem to explain how the '99 could pull ahead of the '01.
Just for fun I was on the Mopar site and saw that the '97, '98, and '99 cars all show the same part number for the cam (4763-708). The '00 and later all show a different part number (5037-151AA). According to my manual, and some research on this site the difference is that the earlier cam has 66deg of overlap and the later cam has 60deg. "Cream-Puffs", no. Different, yes.
Last note in this long post - I added a Corsa cat back exhaust, and pulled the cats on the '99 car last week. We ran the cars again today and the '99 pulls another car length or so on the '01. Seems to have made a reasonably decent improvement.
