Solid lifter setup for the 32V - how much valve lash?
11-15-2013, 05:04 PM
#46
Rennlist
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I can tell you this.....when you claim that you've built an engine that has 900hp and it absolutely will not "pull" 5th gear.....you've done something very, very wrong. Sure, you can redesign and stuff in a 6 speed transmission with closer ratio gears, but my guess is that you'd do much better and have a much better race car, with more torque and less bragging.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
11-15-2013, 09:53 PM
#47
Nordschleife Master
Top end HP is only fun in the sense that its the only fun aspect in an otherwise non fun experience.
11-16-2013, 04:45 AM
#48
Rennlist Member
You are a very patient man Greg , not in my nature, I see lots of cars in my Dyno that are supposed to be 500 hp engines and the owners are dissapointed , when I measure them in my unit , but they are convinced when I recalibrate for best torque.
The amount of crap in my industry is close to 100 % . hence the confusion with the torque discussion .
The ones with the knowledge tend to answer questions ..
Best torque wins races end of story , as it is what is measured at the wheels how can you recalibrate for anything else.
The amount of crap in my industry is close to 100 % . hence the confusion with the torque discussion .
The ones with the knowledge tend to answer questions ..
Best torque wins races end of story , as it is what is measured at the wheels how can you recalibrate for anything else.
11-19-2013, 12:33 PM
#49
Nordschleife Master
Join Date: Dec 2004
Location: Guelph, Ontario, Canada
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Piston speed....piston speed.....piston speed.
Do some calculations of the piston speeds when using a long stroke crankshaft....however, one doesn't need to strain their brain cells too far, when there are so many readily available examples.
The "uber trick" Kaltech all aluminum small block Chevy engines (for the GTP program) made 740hp and were limited to 7,600 rpms.....and they were actually frightened that this was too high, but had to allow the engines to rev that high, because peak power was at 7,200. They ran 3.7" stroke crankshafts and were working "hand in hand" with the very best engineers that Chevy had and with the very best pieces that money could buy.
And they had "short gears" that allowed them to stay in the correct rpm range.
High RPM horsepower sounds good....and is fun to brag about....but with the inherent "long gears" that a 928 has, an engine with torque is going to be very difficult to "catch", in rear life.
I'm not sure how many times I need to tell this story, before people begin to grasp reality.
I ran 1/2 of a team that IMSA raced air cooled RSRs. We had two cars....a one year old 964 RSR and a brand new 993 RSR.
The brand new 993 had the factory engine removed (345hp) and got a brand new uber trick Porsche Motorsports "Sprint" engine, which made over 410hp. Bigger cams, bigger valves, aftermarket fuel injection, more rpms. The 993 also had its 6 speed gearbox converted to an "active" 6 speed, with very close ratio gears.
The 964 got the brand new stock RSR engine out of the 993 and still had the old 964 5 speed.
The 964 consistently turned faster laps, at Sebring, even with the "lessor" drivers (The 993 was the "primary effort" and had professional drivers. The 964 was the "rent-a-ride" car.)
Long story short, two of the professional drivers decide to find out what was going on and slowed down the two cars on the back stretch at Sebring, got side by side at 50-60 mph, and raced to the start finish line. The 964 won by 10 car lengths.
The ultimate test of horsepower versus torque.
I build my engines to make torque, with horsepower and rpm a secondary goal.....always have, always will.
Do some calculations of the piston speeds when using a long stroke crankshaft....however, one doesn't need to strain their brain cells too far, when there are so many readily available examples.
The "uber trick" Kaltech all aluminum small block Chevy engines (for the GTP program) made 740hp and were limited to 7,600 rpms.....and they were actually frightened that this was too high, but had to allow the engines to rev that high, because peak power was at 7,200. They ran 3.7" stroke crankshafts and were working "hand in hand" with the very best engineers that Chevy had and with the very best pieces that money could buy.
And they had "short gears" that allowed them to stay in the correct rpm range.
High RPM horsepower sounds good....and is fun to brag about....but with the inherent "long gears" that a 928 has, an engine with torque is going to be very difficult to "catch", in rear life.
I'm not sure how many times I need to tell this story, before people begin to grasp reality.
I ran 1/2 of a team that IMSA raced air cooled RSRs. We had two cars....a one year old 964 RSR and a brand new 993 RSR.
The brand new 993 had the factory engine removed (345hp) and got a brand new uber trick Porsche Motorsports "Sprint" engine, which made over 410hp. Bigger cams, bigger valves, aftermarket fuel injection, more rpms. The 993 also had its 6 speed gearbox converted to an "active" 6 speed, with very close ratio gears.
The 964 got the brand new stock RSR engine out of the 993 and still had the old 964 5 speed.
The 964 consistently turned faster laps, at Sebring, even with the "lessor" drivers (The 993 was the "primary effort" and had professional drivers. The 964 was the "rent-a-ride" car.)
Long story short, two of the professional drivers decide to find out what was going on and slowed down the two cars on the back stretch at Sebring, got side by side at 50-60 mph, and raced to the start finish line. The 964 won by 10 car lengths.
The ultimate test of horsepower versus torque.
I build my engines to make torque, with horsepower and rpm a secondary goal.....always have, always will.
The slower the piston speed, the longer it will last. Basic physics.
10-19-2021, 06:50 AM
#50
Rennlist Member
Join Date: Feb 2011
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That's right, high rpm and high piston speed will reduce engine life. But if you are building a high performance engine to play with, longevity is not the first priority.
Åke
Åke
