1991 Turbo 306 coupe MS3/PiMPxs tuning adventure

I've been talking to Tony at Astro and figured I'd post what he and his builder's thoughts are on the transmission noise in case it might help someone else in the future:

Well, Gerry said he thinks that the 1st Gear is probably touching the 1st/2nd Shift Fork. Which when they are machined correctly, the gear doesn’t touch. But, the noise would only happen while in 1st Gear…not other gears. I can hear the noise really apparent in 1st Gear. That is why he thinks its that. Now, it doesn’t take many miles in 1st gear for the gear to “clearance” the fork…as the Steel Gear will win the battle vs. the cast aluminum fork it could touch. But, we don’t want that extra aluminum flake in the oil. But, I’m not 100% sure that it is 1st Gear touching fork. I would say that the G-Force Cases have shown to have issues with the 1st Gear touching the Case as the castings were a little thicker this last go around than previous….but, not under load. The gear thrust forward when loaded..which is away from the case. That’s why we don’t think its that.

Thankfully he said he'll be sending me a box with packing materials and a prepaid FedEx label to send it back to them.

Right now the plan is to go to the shop tomorrow (Thursday) and do a couple short drives with the latest and greatest tune file and collect some datalogs. Then pull the transmission out, drain it, and get ready to ship back to Astro.

Oh, and my buddy has a 2011 GT/CS and a new Borla cat-back kit that we might try to install if we have time

Hey guys, so I'm at the shop now and wanted to upload some logs real quick before switching gears to do my buddy's catback exhaust. We reset the timing once the engine was warmed up, setting to fixed at 20 deg and offset at 10 and got the balancer to read right at 20. Then went back to use table and went for a drive.

Looking at the logs real quick after we got back, it looks like the AFRs under boost were much better on this tune, all under 12 AFR in the points I checked. I've attached my latest tune (I only changed the EGO PID Proportional gain to 15 as suggested by Steve, and enabled VSS) and log file from the long drive to the gas station and short drive back to the shop.

The coolant temps went up to what I considered scary at like 225, so not sure why that is... We did add the metal upper rad pipe so is it possible there's an air bubble? I've never had that happen before but have heard that it could be a thing Anyway, thanks as always! On to exhaust now and then pulling the transmission.

Thanks Steve! Attaching cold start up idle log. FYI this is before resetting the timing back to 10 offset

Hey guys, just wanted to do a quick update on the transmission saga and what's next on the to-do list. Tony at Astro took care of everything and I got the transmission back yesterday so now I just have to find the time to get back to the shop and put it back in.

Here's the diagnosis per Tony:

Transmission was dyno tested and noise that was considered unacceptable was only in 1st Gear. All other gear mesh/whine while in gear or on acceleration or deceleration was labeled as normal as the reduced helix angle of gear set is responsible for those noises. Transmission was tore apart and it was found that the 1st/2nd shift fork was not the culprit of the noise. The fork was clearance correctly when built. It was actually the outer edge of the 1st/2nd Slider (part made only by the aftermarket) was touching the cluster gear as the part did not have enough of a tapered edge to prevent it from making contact with the cluster while engaged into 1st Gear. Gerry changed the slider to a New 1st/2nd Slider and used marking compound to insure that as transmission was in 1st gear it would not rub/touch the same position it was touching on the previous design slider.

I admittedly don't know what exactly he's talking about but just hoping everything is fixed and the terrible noise is gone.

Other than that, after chatting with @a91what and @stanglx2002 about my MAT temps and moving the ACT sensor, we decided to use the slot style MAF I bought with the On3 kit to read the temperature. This solves the issue of having to physically move the MAT sensor from the lower intake and extend/run wires, and also gets it into the fenderwell before the throttle body where temps should be cooler.

I took some notes from our chat discussion and my plan right now is to wire up the MAF temp signal and signal return wires to the factory MAF harness and then swap pins 9 and 25 in the ECU for the MAT and ACT sensor. This will allow the MS/PiMP to read the MAF temperature for MAT instead of the ACT in intake runner 5. Then in the future I could mount the old ACT sensor in the front bumper before the radiator and use a ADC input on the PiMP expansion connector to collect ambient air temps. Pretty cool stuff!

Once the MAF is wired up I'll need to check the temp reading and calibrate if necessary. I'm hoping to have a few hours tomorrow to get this part done and then if I can get help Sunday put the transmission back in and get back to tuning this thing

Oh, and I'm also gonna pull a plug for Steve to see how things are looking and make sure we're not getting any detonation. Hope you guys all have a great weekend!

Update coming soon! Shiz has been hitting the fan database-wise at work every day at some point so I've been having to play fireman and haven't had a chance to type up my update yet

Hoping I can get on tonight to post pics and what all we got done with the car on Sunday

So here we go! I got down to the shop for a good part of the day Sunday with my buddy and we made a lot of progress on the car. We got the newly fixed A5 transmission installed again and it was a bit more work than normal because of the Stiffler's spider braces and exhaust parts that had to come out with the transmission but overall not too bad.

Since I had a terrible exhaust leak at the downpipe, I got some new V-band clamps from RacePartSolutions (have I mentioned the On3 ones are garbage?) and some steel exhaust gaskets and used them when reinstalling the exhaust pieces.

Once back together, I test drove the car down the road and back and the noise in 1st gear was gone as well as the exhaust leak! Thank you sweet baby Jesus! lol

With that out of the way and the car driveable again, I pulled the passenger fender liner and got to work on installing the slot style MAF. While I was working on that and the wiring, my buddy started working on cutting a bigger hole in the fender area to fit the air filter with 90 deg elbow to get the filter out of the main engine bay and into the fenderwell. I might do a separate post on that since I haven't seen anywhere in my google'n an On3 kit with "cold air intake"...

I think it came out really great. I'm not sure how much difference it'll make temp wise but I like the look and am thinking about making a little piece of cowling that will go around the pipe to help isolate it from the rest of the bay. What's also really nice about the "access hole" we cut is that now I should be able to get to pretty much everything in the fender well (boost control solenoid, MAF, intake piping from intercooler to throttle body) without having to pull the fender liner! WOOT!

So, with that done I finished up wiring the MAF temp signal and return wires to the factory harness and swapped the MAF and MAT pins in the ECU. When I connected tuner studio without the car running, the MAT was reading 83 so it seemed to be pretty accurate. I started the car and let it run for a bit and got worried that the MAT didn't seem to be increasing but eventually it did by about 10 or so degrees. I've attached the log here for you guys to let me know if that seems right or if there's something I need to do with the sensor/wiring/calibration.

I'm so used to the MAT being both very high and increasing quickly that seeing it pretty steady at around 85-90 (idling) seemed like something was wrong. I'm hoping that it's correct though and a good sign since it's now in a MUCH better location than before! Big thanks to @a91what and @stanglx2002 for helping me brainstorm and realize that I could use my MAF to get the temp

I think that's pretty much it for this update... I'm going on vacation Friday through next week (Asheville and N Georgia) so just been so busy trying to get things in order at work so they don't have to bug me while I'm away haha. One can hope anyway

As always, let me know what you guys think and if there's anything you think I should address. Thanks!

Pics in next post rather than sprinkling through here...

Full undercarriage shots (giggedy)






MAF plug removal and install/wiring:








Filter relocation/CAI






Glamour shot

Oh, and logs and current tune since I forgot to attach to the first post

Tune should be same as most recent 9.1.2 but with tweak to the VSS pulses/mile. Cold start log is before adding the MAF and using for MAT. Other log is after installing the MAF and using it for MAT.