944 2.5 8V Race car #55
08-20-2015, 10:51 AM
#47
08-20-2015, 11:51 AM
#48
Rennlist Member
Thread Starter
Could get more peak hp with some mods but guessing it would kill the nice torque curve.
Head work was quite simple, stock valves, valvejob, removed the bump next to valve seat and some widening on the sides before intake valve. Exhaust was left almost as it is. Sorry No pics from head, was too busy week trying to get the engine built up.
08-20-2015, 11:53 AM
#50
Rennlist Member
Thread Starter
I'm 99% sure the 944S2/968 used the same pipe sizes as the 944 NA for the header primaries, the collector, and the system piping until after the cat. So you should be OK until at least 236 hp 
something im looking into for my car and power-testing is adding an abrupt step up in pipe diameter somewhere along the length. idea is that at this step a negative pressure wave is created in the exhaust that shoots back towards the exhaust valves. depending on the length of the system before the step you can tune that to an RPM to help extra-scavenge the cylinder which makes for a small power boost. i have to keep a catalyst installed so i dont know how the wave tuning would be affected by that but...it's something id like to try eventually.
something im looking into for my car and power-testing is adding an abrupt step up in pipe diameter somewhere along the length. idea is that at this step a negative pressure wave is created in the exhaust that shoots back towards the exhaust valves. depending on the length of the system before the step you can tune that to an RPM to help extra-scavenge the cylinder which makes for a small power boost. i have to keep a catalyst installed so i dont know how the wave tuning would be affected by that but...it's something id like to try eventually.
08-20-2015, 11:54 AM
#51
Rennlist Member
Thread Starter
The Stahl Headers have the reputation for BEST in North America. They aren't cheap... but when the 330 hp n/a 4 cylinders are being built & tested by Michael Mount, these are the headers he uses. The other top 944 engine builder (Jon Milledge) endorses them. Worth the money YES. I bought mine here: http://www.mantissport.ca/Products/P...s/Default.aspx Mine have a 3" collector & 1 3/4" primaries (external measurements). The gaskets fit PERFECT, no grinding needed.
08-20-2015, 12:12 PM
#52
Rainman
Rennlist Member
Rennlist Member
The S/S2 used almost the same exact 2-1 collector pipe as the regular 944 NA.
08-20-2015, 12:22 PM
#53
Race Car
Yeah Porsche really complicated the communication & added to the confusion with all these engine variations, didn't they? I always thought since the 16v 2.5 was the same block and different head, that the 8 valve 2.5 exhaust should bolt up, no?
08-20-2015, 12:45 PM
#55
Rainman
Rennlist Member
Rennlist Member
Any experience on header pipe diameters for N/A? measured ours today - seems to be 54mm in the end of exhaust header after two header pipes connect, 2'' inside diameter.
Do you consider this to be limiting factor to go over 200hp? just read this article.. Header pipe sizing might be different than overall exhaust..
Our header is some aftermarket header but don't know exact type. it is 4-2-1 style, with longer primer pipes than what stock has.
http://www.exhaustvideos.com/faq/how...pipe-diameter/
Do you consider this to be limiting factor to go over 200hp? just read this article.. Header pipe sizing might be different than overall exhaust..
Our header is some aftermarket header but don't know exact type. it is 4-2-1 style, with longer primer pipes than what stock has.
http://www.exhaustvideos.com/faq/how...pipe-diameter/
08-20-2015, 12:55 PM
#56
Rainman
Rennlist Member
Rennlist Member
Stock is best for the stock car or mildly modded daily driver/street car.
The varying pipe lengths spread the torque curve on a wider range of RPM making it friendlier on the road. Not to mention, they don't cost anything, and flow plenty.
But if your intention of the engine changes, like Matti's race car or your dirt-bombing toy Wilson, then the header design can be changed to suit.
Equal length (or more-equal length) narrows the RPM tuning range with the tradeoff being a higher tuning effect = more torque in that range than the stock pipes would provide. And more torque = more power.
The merge style (4-2-1 or 4-1) and collector size difference vs primary/secondary pipes also affects this tuning range.
08-20-2015, 03:55 PM
#58
Rennlist Member
Thread Starter
Some vids from 2013 and 2104
Our race 1 2014 (1st in class 8A, wet race)
http://youtu.be/feGfWZSVzVM
Our Race 2 2014 (1st in class 8A)
http://youtu.be/JrYIFv9cCwk
2014 trophy vid
http://youtu.be/YWXarvY4vbU
2013 Festival vid
http://youtu.be/P9DLT5dqG-A
