I would also like to add , what about balancing the crankshaft with a lightwheel pulley?? similar to the GT3rs or GT2Rs..?? so that there is no exsessive one side loading...???

To be honest Bob, I'm not 100% sure. That would be a question for GIAC. I'll see if I can dig up an answer. I do know that they can make some provisions in the software for the LWFW, but I don't know exactly how it's done.

We have an identical setup in our 997TT and it doesn't seem to be an issue.

I'll definitely report back with some more information as soon as I can....or I'll ask GIAC to chime in. :)

Tom, thank you.

I agree...I had a 764 and an Aasco in my Ruf conversion, and while there was a little rattle, it worked really well. I was told there is something different about the GT2. Just wasn't sure.

I'm going to guess that launch assist is probably going to be screwed up as the 5000RPM boost loading was set specifically for the OEM boost, timing and clutch/flywheel setup. But I was told that the issue goes beyond this.


bob

We haven't had any issues with it so we leave the stock pulley in place. The RS's have a dampened pulley, but I'm not sure if there's any difference beyond that.

Agree. All I know is that we used the same Sachs 764 and Aasco setup on the previous GT2 we built and there were no issues at all. Launch assist even worked just fine.

I'll get a more detailed answer from GIAC asap...

OK....so here's another update. It seems it's back to the drawing board for another clutch option for this build. Initially we thought the Sachs 764 would hold, but the power output of this car is pleasantly exceeding our expectations by a lot! As you can see from the graph below, the clutch gives out right around 5600 rpm's, which is at 640 lb/ft of tq. Interestingly, the Sachs 764 kit is rated at 650 lb/ft of tq as it's limit....so it's definitely not going to be enough for this package. You'll also notice a dip at around 3500rpm....that's not the clutch slipping, but at this point we'd already done a couple runs with the clutch slipping and were trying to feather the throttle and build tq a little slower in the run to see if it would still slip at the same point, which it did.

That being said....735 WHEEL HP with a slipping clutch is nothing to shake a stick at. ;)

We've got some plans for another clutch option that will hold the power and keep drivability. I'll get some more info on that as soon as I can.

http://farm6.static.flickr.com/5055/...48856086_b.jpg

Theres a thread on rennlist where there is a discussion that GT3s with LWFWs had the pulleys come off when used at the track.

http://forums.rennlist.com/rennforum...track-diy.html

Regarding the pulley diffrences
GT3 pulley is steel, 494 grams which i assume is the same one used in the GT2 ? . The RS pulley is aluminum and weighs 292 grams

There was a TSB that Porsche issued regarding LWFW conversion of GT3s. However, the ECU programming that I was referring to is not related to the under drive pulley. As far as I am aware, I have not heard of the problem afflicting 996TT, 996GT2 or 997TTs.

bob

If the dip at 3500 rpm is not the clutch slipping, then what do you think it is? Boost spike? It was also present in a previous dyno as well so it seems to be consistent whatever it is. I'm also surprised the stock programing worked as well as it did with all those mods on the car.

https://www.6speedonline.com/forums/...eleased-7.html

TTdude-You may have misunderstood. Tom said the 3500rpm dip was not a dip, but where they were feathering the throttle in attempt to get further up the rev band without completely lunching the (764) clutch. Will be interesting to see what their "civilized" Mark III clutch fix will be.

Nice progress Tom! When you get a chance, can you re-post that graph in SAE? Makes for comparing DJ numbers much easier.

Thanks!

Thanks for the explanation!

Hi Neil, I believe those graphs are in SAE...but I'll double check with Louis as soon as I get back in the office.

*EDIT*....the first graph with the clutch slipping (above) is SAE, the second I posted (below) is in STD. I'll post the SAE version of the second graph below when I'm back in the office. We left the earlier runs in there so you could see the comparison.

Thanks bumperpip...that's correct. The earlier dip is Louis feathering the throttle, in an attempt to get the clutch to hold. Didn't work on that pass..lol

So, sorry for the lack of updates today. I've been out of the office most of the day. Anyhow, yesterday before leaving for the day, we let the clutch cool down and went for one more glory run on the Sachs 764 since it's getting swapped out anyway. As you can see from the graph below, we managed to get one good pass without any slipping. On the second run, the clutch started slipping again.

I left the other two runs on the graph for comparison. The red lines are hp and tq without any clutch slipping. So....how does 752 WHEEL HP with VTG turbos sound? ;)

http://farm6.static.flickr.com/5057/...5d7916a2_b.jpg

Sound great to me Tom - Is that what I receive Monday for testing? Next gears throughout, suspension, and Aero, and finally...the big one............internals.:D

Nice results Tom

How much boost on the +750whp ran? Pump or racegas?

Your posted dyno shows runfile# 4 as a basline and you inform us that later on in runfile #14 the clutch is slipping so you explain to us you let the clutch cool down and did another run on the dyno so wouldn't that be runfile #15 or greater ? Why is the runfile #5 after runfile#14 . Runfiles #4 and #14 are started at the same RPM and rufile#5 is started much later. Please explain why you expect us to believe these runfiles are in the order that you say they are in or if they are even from the same car.