REDTEK Engine Build
01-04-2014, 11:37 AM
#91
Burning Brakes
Assuming a 40% transmission loss through the C4 drivetrain then 350bhp @ crank will give 210bhp @ wheels? The corrected DIN figures shown should in theory mean that figures between dyno's can be compared regardless of the climatic conditions on the day.
Last edited by ras62; 01-04-2014 at 12:26 PM.
01-04-2014, 02:41 PM
#92
Three Wheelin'
A bit OT but; 40% transmission loss would make a c4 really slow surely? giving away at least 50bhp at the wheels to a c2 in stock form. Most 4wd cars are under 25%. The gearbox and front and rear diffs are a known quantity most are going to be similar in terms of losses in most cars. I've read planetary gears as used in the 964 centre diff which are less common can be 97% efficient. What's the thinking behind 40%?
01-04-2014, 03:30 PM
#93
Burning Brakes
A bit OT but; 40% transmission loss would make a c4 really slow surely? giving away at least 50bhp at the wheels to a c2 in stock form. Most 4wd cars are under 25%. The gearbox and front and rear diffs are a known quantity most are going to be similar in terms of losses in most cars. I've read planetary gears as used in the 964 centre diff which are less common can be 97% efficient. What's the thinking behind 40%?
Alex if you use Frank's BB dyno results as an example they show engine hp 317 with wheel hp 209. That is a 35% power loss. Once DIN corrections (for temp etc) were applied the engine power was recorded as 338 bhp. Worn transmissions or poor oil could quite easily see a 40% reduction while a perfect example might be 30%.
Adrian Steather shows comparison for acceleration between the C2 and C4. The C2 is on average 0.5 seconds quicker in each 20 mph increment in 4th and 5th gear, 70-90 mph in 4th for example 5.0 vs 5.7 seconds. That is quite a significant advantage to the C2 and nothing to do with weight at those speeds
01-04-2014, 05:44 PM
#94
Three Wheelin'
Google MAHA dyno's and drag losses - they are known for their stupidly high drag figures.
I can't argue the Streather/Porsche published through the gears figures, the engine is the same as the c2 and the c4 undoubtedly has more transmission losses so it will be slower once you get past the traction benifits, but Streather also quotes a 28% drive train loss for the C4, make of that what you will.
I can't argue the Streather/Porsche published through the gears figures, the engine is the same as the c2 and the c4 undoubtedly has more transmission losses so it will be slower once you get past the traction benifits, but Streather also quotes a 28% drive train loss for the C4, make of that what you will.
01-04-2014, 07:00 PM
#95
Burning Brakes
Alex, yes a 28% loss on a new car is believable. 35-40% on a 20 year old car is also believable, old oil, wear etc. The modern Porsche 4wd systems are considerably more efficient.
Sorry for getting off topic Jack. Enjoy your new engine
Sorry for getting off topic Jack. Enjoy your new engine
01-04-2014, 07:31 PM
#96
Three Wheelin'
Thread Starter
01-04-2014, 08:03 PM
#97
Three Wheelin'
Agreed with Alex & Frank,
Dino and road fine tune is best but a before and after reading is alway good, depend how far you guys are but at Emerald they have a very accurate AWD Dino , they use it all the time.
Dino and road fine tune is best but a before and after reading is alway good, depend how far you guys are but at Emerald they have a very accurate AWD Dino , they use it all the time.
01-05-2014, 12:34 AM
#98
http://www.weissach.net/964-993_RoadTestSummary.html
01-05-2014, 05:28 AM
#99
Burning Brakes
Simple really. Different cars/days/tests....there are big variation in all those figures. It is also worth remembering the early C4's had a lightweight flywheel and the C4 has shorter 2/3 gears to aid initial acceleration.
It is generally accepted the C4 is fractionally quicker to 30, after that the C2 has a distinct advantage.
It is generally accepted the C4 is fractionally quicker to 30, after that the C2 has a distinct advantage.
01-05-2014, 06:17 AM
#100
Alex so happy for you mate. I know exactly the feeling just prior to getting the engine back in. I actually think I lost sleep for days. I have to say that ***** waggling about power is something that as car nuts we are all to some extent guilty off, and the search for more or justification to its very existence can sometimes detract from the point. I consider us all very lucky/ hard working individuals that have great machines at our disposal. I don't think I've ever got in Peppa and thought first she needs more power. In fact I only really think they come when reading forum posts about other peoples monsters. But i do believe that our machines were gifted adequate power from factory but we were not gifted Walter Rohrl abilities as drivers and surely that's where we should be directing a little more of our energy and to a certain extent time, hence the whole track day thing. I not opposed to a little arms proliferation indeed I intend to add something to the arsenal at some point but to get back to the point a once leaky asthmatic 964 engine has just had some major surgery and lives to breathe again. Something to celebrate? Definitely. I love it jack well done mate. The shiny bits look awesome and when transplanted back into that gorgeous blue featherweight you will have have fun aplenty regardless of final figures. Hope to see you next week.
01-05-2014, 06:50 AM
#101
Nordschleife Master
Alex so happy for you mate. I know exactly the feeling just prior to getting the engine back in. I actually think I lost sleep for days. I have to say that ***** waggling about power is something that as car nuts we are all to some extent guilty off, and the search for more or justification to its very existence can sometimes detract from the point. I consider us all very lucky/ hard working individuals that have great machines at our disposal. I don't think I've ever got in Peppa and thought first she needs more power. In fact I only really think they come when reading forum posts about other peoples monsters. But i do believe that our machines were gifted adequate power from factory but we were not gifted Walter Rohrl abilities as drivers and surely that's where we should be directing a little more of our energy and to a certain extent time, hence the whole track day thing. I not opposed to a little arms proliferation indeed I intend to add something to the arsenal at some point but to get back to the point a once leaky asthmatic 964 engine has just had some major surgery and lives to breathe again. Something to celebrate? Definitely. I love it jack well done mate. The shiny bits look awesome and when transplanted back into that gorgeous blue featherweight you will have have fun aplenty regardless of final figures. Hope to see you next week.
