From: Tom Middleton [midlman@seanet.com] Sent: Sunday, March 04, 2001 1:11 PM To: 928 Subject: [928] Re: Ott Dual Cat Dyno Results Long post for those interested!!!!! Like Adam posted, we had a great day at the third Pac NW dyno day. Lots of different models ranging from a freshly rebuilt 91 GT to a 83 US Auto with 177,000 miles on it...I haven't received all the data from the participants so I can't update all the results yet, but I wanted to give some comparison numbers to Adams since the configurations we are running are a couple of good examples of exhaust system setups that I believe most people would contemplate doing. My car is a 87 A/T , 133000 miles, ADj FPR, flushed fuel injectors and custom Louis Ott X-crossover (no cats) into the stock 87S4 2.25" mufflers back to the RMB. Adams specs are listed in his message but his exhaust system is a complete Louis Ott manifold back 2.5" with high flow cats and the X crossover . I also ran with my stock chips this time to see if there is any difference from the Autothority chips. First for comparison to Adams numbers here is the breakdown by rpm (3000 - 295.2/168.6), (3500 - 268.9/179.2), (4000 - 278.9/212.4), (4500 - 272.2/233.2), (5000 - 257.5/245.2), (5500 - 256.8/268.9), (6000 - 236.1/269.7). Quick summary the peak torque at 3000 rpm 295.2 ft/lbs and the peak HP at 6000 rpm 269.7 HP. I think what this shows is that a well designed exhaust system including cats can be as good as one without cats! Now to make a true comparison I would need to add 2.5inch pipes and mufflers from the x crossover back. I will be installing Adams GT mufflers in the future (replacing the stock S4 ones) to see if those make a difference. The final stage will be to go to the custom 2.5" all the way back... The second part of my experiment was to compare my runs with the Autothority chips. For those interested the details of my runs are posted on my web page under the Vancouver dyno runs link http://www.seanet.com/~midlman In summary, with the exact same car config and the Autothority chips my peak torque was 302.2 ft/lbs at 3000 rpm and the peak HP was 284 HP at 6000 rpm. Comparing to the stock chips (ft/lbs at 3000 rpm - 302.2 to 295.2) and (HP at 6000 rpm - 284hp to 269.7). So as far as I can tell there is a gain of 7 ft/lbs and 14 hp that can be attributed to the chips........Not bad but not nearly as great as the manufacturer suggests! Next lets look at the stock S4 system (including cats) with Autothority chips peak torque at 3000 rpm - 293 ft/lbs and peak HP at 6000 rpm 274.5HP. When compared to the numbers I got with the stock chip and no cat system there is not much difference! Stock exhaust and chips vs. no cats with stock chip (293 ft/lbs vs 295 ft/lbs) and (274.5HP vs. 269.7HP) Looks like adding chips to the stock system is the same as adding the x crossover no cat setup to stock chips....... Two ways to go and the pipes are cheaper!.....Of course in combo it gets better when adding a freer flowing exhaust. So in summary: Cats are not bad, chips do provide some gains, freer flowing exhaust system is a good way to go........ And as a final note I did my first runs (four in a row) and then disconnected my battery for 10 minutes to "reset the brain". Then I ran two more times. The numbers showed a slight GAIN after disconnecting. Torque went up 6 ft/lbs and HP was the same. Now I know that we run WOT on the dyno and in theory there should be no difference. I think it is related to other factors and that disconnecting the brain didn't do anything. If someone know of a way to truly test this "learning" function let me know....... More data will be posted as soon as it comes in. Thanks for listening.. later, Tom midlman@Seanet.com 87 S4