Accel Junky

Got a last minute invite to do a baseline today on a 2WD Dynojet.

I assume turn off the TC/SC completely but with the shorter gearing thanks to the .2 RS 3.89 R&P, what gear should I dyno in and anything else I need to know? Not sure this shop has done a 997 before.

Looks like 5th is 1.06 closest to 1:1 but I wasn't sure if the R&P change mattered for the dyno and if there was anything I needed to do to fool the car on a 2WD dyno.

Thanks!

Accel Junky

Found out the hard way how to do this.

Shoutout to Dundon Motorsports for helping me via phone. I called a few major Porsche shops who were all out of the office and eventually talked to Charles who let me in on the eventual solution to some RPM pickup issues we were having. Very nice of them for helping out some random GT3 owner!

I will post results in my build thread soon.

ScottArizona

Glad you figured it out, and sorry I couldn't help. However, I am very curious as to how you like the 3.89 R&P. Thinking about doing the same for my 996. Was it a pretty dramatic seat of the pants difference, or relatively subtle?

Accel Junky

Hard to say since my "CPO" car came with the trans already worked over

That being said, I can't imagine the car without it. The gearing seems so perfect at least on the street and to my taste. First track day in it is coming up in June unless I decide on an earlier event...so can't comment yet on suitability for the track.

996FLT6

Had the Copans 4.0 r/p on my 6gt3. My 3rd gear feels like my 2nd gear. Great for technical tracks where 3rd gear stock feels too long. Nice trq. You'll lose abit of top end speed and 1st gear is very short but not a big deal for me. I like trq going thru tighter corners vs a lazy long 3rd gear- way more control. Mike

garyever

I recently had a Dynojet baseline run for my .1 GT3 at a performance shop that specializes in helping the racing community build higher performance engines as their only business. I wanted to see if my engine was getting tired after 10 yrs, 25,000 mi, and a lot of tracking. Instead, I was amazed to see dyno readings at the "wheels" of 390 max HP and 316 ft lbs max torque which using a conservative +10% conversion factor would put HP at 433 and torque of 351 at the "engine," well over the original OEM specs. of 415 HP and 297 ft/lbs. found in the owners manual. They do 100's of these dyno runs a month, factor in humidity, ambit temperature, etc,, and are considered the best shop in the area. They ran the tests in 4th gear, 4 runs, and all produced close results.

I used my OEM 19" rims and Michelin PS2 tires for the tests. i track with 18" Forgeline rims and Hoosier R7 slicks. The dyno manager told me that if I had used the 18"s the HP and torque would have been lower due to the way dyno is calculated? I had to scratch my head on that one. Those 18's take 10 seconds or more off my lap times.

Anybody have any thoughts about the high readings and 18's posting lower HP/Torque?

SLC-C4S

I just swapped my 997.2 GT3 to the 4.00 R&P and it was a huge change. I also did the RS 4.0 clutch and flywheel at the same time, but that really just helped my rev matching between gears. The low end torque is very noticeable! You do lose some top end and yes the gears are shorter, but it's definitely a lot more fun to the drive! With my current setup your max speed is reduced to 162MPH, but I rarely get above 90 so who cares. I would definitely do it if you have the funds

JasonAndreas

I think Mark Dobeck will be the first person to tell you that absolute performance numbers from a dynojet are nearly meaningless.

HarmonyJim

SLC-C4S, considering you mentioned "do it if you have the funds", what is the approximate cost of a R&P exchange? I was thinking the 3.89 - as in the .2 RS. Mine is a .1 RS. Thanks in advance.