Later Higher compression pistons?
#17
IIRC from reading the rules, as long as it was delivered in a 944 from the factory you can run it... meaning it should be alowable to run an 83 chasis (lighter) with an 88 motor (few more hp)...
#18
http://www.ebay.de/itm/Porsche-944-Kolben-Pleul-Bolzen-4-Zylinder-Motor-ohne-Lager-Sport-Getriebe-/160654056332?pt=DE_Autoteile&hash=item2567ba5b8c#ht_1350wt_179
#19
So the euro pistons are illeagal both because they were never sold on a USA legal car and also they are clearly over 10.5:1 as is.
#20
All cars must come in no less than 2600lbs with driver. So the 83 weight savings is muted to an extent, but if you are big guy it will be easlier to get to min weight in a 924S or 83-84 944 chassis as compared to an 88 chassis.
Any car may run a motor from any year and you may run either piston and/or shave heads. At nationals the this year the winning car used 88 10.2:1 pistons and the second place car use 9.5:1 pistons. Both heads shaved near the limits. Both cars made with in 1-2 hp of each other when tested on the dyno at the event. Now when it comes to actual hp there are many nuances that we in class are a looking at to ensure all cars have similar hp with either piston. We are not yet ready to share everything we have learned yet as we need to make sure we understand it first.
#22
Not really... It is a long story, but that 20 hp bump from 143 SAE net ot 163 DIN is not really 20 hp. 7 or 8 of that HP is due to the difference betwee SAE rating method in the USA vs DIN rating standards. If you look at the native kW rating for both motors the gap is closer to 10 hp. Some of which comes because the euro cars did not use a CAT either.
#23
good pistons are hard to find at reasonable prices. I think factory is the way to go with the iron coating, but there are differences from K-S to Mahle and their weights/shape. I would be curious to know what pistons are being run in spec and why.
#24
Porsche OEM stock only. 9.5:1 or 10.2:1. I don't believe anyone has bought new pistons. Too expensive. Best place to find pistons is in a motor attached to a car. Those will be the best value. 9.5:1 pistons are pretty common. 10.2:1 are more rare and we are always wacthing to limit any performance gain on track from using these. So for nearly 10 years we have been sucessfull in that.
#25
This is theoretical as I have no measurements but it seems to me you can fly-cut the valve reliefs further on the 10.6 pistons, bring them to 10.2 or 9.5 spec and create a non-interference engine. I've asked before but no definitive answer.
#26
I am sure you could try. However you starting to get into things like the shape of the squish area and deep valve reliefs can have big issues. Personally I think the who '"interference engine" deal is way over blown. That and the "fear of t-belt". All the "solutions" are 10x the work of just maintaining the car as is.
#28
I am sure you could try. However you starting to get into things like the shape of the squish area and deep valve reliefs can have big issues. Personally I think the who '"interference engine" deal is way over blown. That and the "fear of t-belt". All the "solutions" are 10x the work of just maintaining the car as is.
#29