Try analyzing tire temps across the tire tread: inside, middle and outside of each tire. I use a digital tire probe to check and keep that info, but you can use a cheap infrared temp reader to get a general idea. Note wear to the tread blocks as well- too much wear to the outside of the tire usually means overinflation. You'd like to have relatively uniform temps across the tire for best traction, but setup and driving style can alter your results. Try not to make big air pressure changes, as one or two PSI changes are usually the best to try on a single axle.

 

With the current Goodyear SuperCar R3s I run 35 psi hot, start them at 30 in the morning, then bleed off the pressures after each session as the temps increase.
If your rears are going up in pressure quicker than the fronts I would definitely take a look at your suspension setup and geometry as this should not be happening. Your rears and fronts should be going up at about the same rate with the outside tires (left on clockwise tracks, right on counter-clockwise tracks) going up slightly quicker than the inside tires.

 

Just got back from a test day at Summit Point. Glad to report the headers and the tune are working well. Especially in the midrange 4-6k there is more power available, although between 6-7K it feels about the same as before. My top speed didn't improve, still around 131-132, but I did improve on my personal best lap time, I'll need to review the data to know exactly, but it should be a 1 second improvement or so. Also with the headers the car actually sounds less drony inside the cabin, it's still loud but not as annoyingly trombone like as before. So overall a very successful test day and I feel much better about the winter mods and about taking the car to Watkins Glen next month.

I just checked the videos and the front camera for some reason didn't work. But I do have some data. My previous best was 1:23.3, the new one is 1:22.8 so just half a second improvement. I'll be very curious how it does at VIR, but for that I'll need to wait probably until fall.

 

Back from 2 days at Watkins Glen with NEQ Audi. Great time and great weather, I can't say enough about how nice that area is to visit, with tons of wineries, bars, restaurants and unbeatable views of the finger lakes. We went there a day early and spend the first day just driving around and exploring.
But back to the actual track event. This was my first time back since 2011, so I don't really have a good reference for performance. Back then I was driving my Audi as a student and my best times were in the 2:29 range. This time around once I refreshed my memory of the track and figured out the shift points, which are quite a bit different than what I had in the Audi, my best laps were in the 2:13 range. The event was fairly low attendance, only 100 cars total, so the track was not very busy, but there was a wide range of cars so there was a bit of slower traffic to manage. Here are a couple videos from the event, the first one is my chase of a yellow Cayman that was fairly close matched to me, I had to work at catching him. The second is a few fast laps from the Tuesday, last session before I had to pack up and start the 6 hr drive back.

 

Passing Porsches left and right!
Z sounds amazing. that drivetrain is doing well after all the events you've done.

I wonder how many of those Porsches have been strengthened for track use? the 987.1 and 997.1 engines need a baffled oil pan. and so many of the drivers, of course this is just my opinion, think that they need to push those cars to red line. no! maybe with a Metzger GT3 engine, but peak torque is 4400, not 7000.

in my opinion, the only time to hit red line is on a long straight. and there are none in California. I'm still jealous of your track videos on those beautiful gently curving tracks. 😉 all of them out here begin with a 90° turn which is just so unfair. hehe or in the case of thunderhill, a 180. by the time you get up to speed, it's time to brake.

 

Thanks. The sound is better with the headers, still loud but not as much drone, sounds less like sitting inside of a trombone.

I did note that the car seems to be running richer on the new tune, there is more soot buildup on the rear diffuser and looks like it's getting higher temps, so there might be some unburned fuel making it to the exhaust. My buddies there were behind me said they didn't see any visible smoke but could definitely smell it running rich. Might need to reach out to the tuner about that.

Does the '06 up-rev model have wideband O2s? Based on the different multi-lead plugs I would think maybe? Wonder if I can hook up a wideband gauge to one of them to see what the actual AFRs are when on the track, that would tell me a lot.

Yeah, the glen is a fast course, it's a nascar track, so really only the boot section (after the back straight and the long right sweeper where it turns to the left and goes up hill, then comes back around to the main track) is interesting, the rest of it is fairly straight, just plant your right foot and hold on.

 

I did a bit of research and my car uses the Bosch LSU4.2 wideband primary O2 sensors. So can I use an ODB based wideband gauge with it? Would something like the AEM one work?

https://www.aemelectronics.com/produ.../parts/30-0334

 

According to AEM this doesn't work the way I thought it might. The gauge OUTPUTS AFR readings from the O2 sensor to the OBD port, not the other way around. So I went ahead and ordered a wideband gauge with separate O2 sensor that matches my other center console gauges and I'll be swapping the pretty much useless exhaust temp gauge for a wideband gauge and welding in a new bung for the sensor. I'll probably locate it on the Y pipe, not on the headers, since I don't really want to drill holes in the headers. Should work just as well.

 

that sounds really rich. like less than 10.0 AFR. but I'm not sure what's normal for these engines. maybe all engines are similar? like if it leans out more than 14.0, danger of detonation? but if too rich, it's going to ruin your O2 sensors.

that happened to my Roush Mustang years ago. the last time I tuned for AFR the tuner wanted to see it at 11.0 at WOT. but I added a bigger TB which tweaked the tune just a bit to go rich. the OBD codes for clogged O2 sensors are screwy. sometimes the ECU doesn't get it. I thought it was bad fuel. but replacing all four O2 sensors solved the problem after fixing the tune.

I agree, it's a better solution to add another bung and aftermarket wideband sensor post-cat. in my Mustang at the time, the tuner welded in the bung near the x-pipe. you just don't want to go pre-cat for wide band.

 

There are no cats so that's not an issue.

Not sure why you say you don't want wideband before cats, the stock O2 primary sensors are pre-cat and are wideband.

The theoretical optimal afr for power is 12.5:1, however in reality that can vary depending on the octane, timing, combustion temps,etc. 14.7:1 is optimal for efficiency, like idle or cruise with minimal load.

 

A couple pics from the event courtesy of etech



2nd pic is from the sweeper between the bus stop and the boot. Of all the tracks that is the most sustained lateral g force turn I've experienced. Full suspension compression.

 

you're right, the AFR sensor needs to go pre-cat. it's been a long time! my memory recalled that the shop welded the bung post cat and it was not very useful at the time.

but yeah that doesn't matter with a track car.

 

I received the ISR y pipe and the wideband gauge. The gauge comes with a control box that connects the gauge, the sensor and power and has an analog output with 0-5V wideband and 0-1V narrowband leads. Theoretically I could hook up that output to one of the existing primary O2 sensors and reuse the bung, however I'm not sure the signal would be the same as the stock sensor, so it's probably not worth the headache. I'm going to go ahead and install a new bung on the y pipe just for the gauge. The included O2 sensor lead is about 10 feet long, so plenty of run to mount it in the common exhaust of the Y, but I'll need to see how much space there is under the car for such setup as the sensor needs to be mounted 10 degrees higher than horizontal so that moisture doesn't collect on it. In the worst case I can mount it on one of the arms of the Y and read just one bank, there is plenty of space there. Gonna pick up a new bottle of shielding gas for stainless and weld it probably next weekend.

 

Got the wideband sensor installed in the ISR y pipe and got the pipe installed and the wires run back to the center console.
I always thought the oem y pipe had the same diameter as aftermarket ones, but once I measured I realize the stock y pipe was dual 2" pipes going into single 2.5" whereas the IRS is dual 2.5" going into a single 3". So I was running 2.5" headers going down to 2" in the y pipe, which I'm sure wasn't optimal for top rpm power. Maybe now that it's dual 2.5" going into single 3" all the way down I can get a couple more mph on the top end....

Stock pipe diameters



ISR ypipe with wideband sensor installed





installed showing the sensor location and clearance

 

When I was pulling out the floor mount to put it in the z3, I peeked at the Z1 Y pipe I installed three years ago and it does have the wide band bung pre fitted.

Curious about where you ran the sensor wire. But I think the fuel tanks are above that spot So it has to be run from below.

 

You can kinda see the wire in the photo I posted, it's secured to the cross bar above the exhaust and below the driveshaft, then I have it secured to the O2 sensor cables coming from the header and going up with those up behind the block and into teh cabin

 

finished the inside wiring. Managed to crack the replacement fascia around the lighter plug, but I'm too lazy to try to print it again, with some glue it'll be fine.

 

Ok, I'm annoyed because this wideband gauge is reading 10 all the time no matter what I do. I followed the troubleshooting on the ProSport site and made sure the accessory power, battery power and ground was good but it just refuses to work. I did the factory reset and calibration and afterwards it did read 20 (engine wasn't running) but after I let it sit a few hours it's back to reading 10. Could be a bad sensor or a bad controller? Sigh....

 

It seems unlikely, but maybe try pulling the sensor out of the pipe to check it.

 

they are sending me a replacement sensor and control box to troubleshoot, one or the other is likely bad