Safe RPM survey for the modified engines
#1
Nordschleife Master
Thread Starter
Safe RPM survey for the modified engines
Here's an attempt at a quick survey. There are a number of high-performance 928 engines out there at this point making impressive power. Who's got the highest revving engine? I am intereted in how high are people comfortable reving their expensive engines, and where they have set the redlines. Furthermore, what changes were necessary to get the motor to hold at the high revs, especially the short block? How should one build a reliable 928 engine that is capable of running at high RPMs reliably for many thousands of miles and many many hours.
To set some bounds, only 928 engines qualify. Also, only engines that have actually been run qualify, my project and other such I'll-run-a-dry-sump pipe dreams don't. To soften that a bit, a separate category for ongoing projects. Finally, there has to be some reliability expectations, it's not enough just to remove the rev limiter!
To set some bounds, only 928 engines qualify. Also, only engines that have actually been run qualify, my project and other such I'll-run-a-dry-sump pipe dreams don't. To soften that a bit, a separate category for ongoing projects. Finally, there has to be some reliability expectations, it's not enough just to remove the rev limiter!
#2
Race Director
With the exception of Mike Simard.....not very many stroker 928's rev past 7000, or make power past 7000....... Mike used Ti rods to keep the rotating weight down enough to allow such RPM's...... I think Anderson can rev to 7000 under racing condtions....but doesn't have too....most shift around 6500 or so....
Heres some applicable calculators
http://www.wallaceracing.com/piston-speed-velocity.php
http://www.wallaceracing.com/Calcula...-of-Piston.php
http://www.slowgt.com/Calc2.htm#PistSpeed
http://www.slowgt.com/Calc.htm
Heres some applicable calculators
http://www.wallaceracing.com/piston-speed-velocity.php
http://www.wallaceracing.com/Calcula...-of-Piston.php
http://www.slowgt.com/Calc2.htm#PistSpeed
http://www.slowgt.com/Calc.htm
#3
Sorry I don't remember the exact numbers offhand, but of the ones that I've heard of so far, the highest is one going somewhere over 8,000 RPM, and making over 800hp up there. That was the crankshaft horsepower, not rear wheel horsepower, as measured on an engine dyno before the engine was installed in the car. The engine's normally asprated, right around 6.5 liters, is steel sleeved, has an individual throttle body type intake, with coil on plug ignition.
I forgot most of the stuff that one of the mechanics who was involved with that project told me about the details of the engine the last time that we were talking about it. I'll probably see him over the Labor Day weekend, and will try to remember to get some more exact numbers from him again then.
I forgot most of the stuff that one of the mechanics who was involved with that project told me about the details of the engine the last time that we were talking about it. I'll probably see him over the Labor Day weekend, and will try to remember to get some more exact numbers from him again then.
#4
Rennlist Member
25 race days so far. all racing shifts at near redline 6500rpm. (6600redline)
power curve doesnt pay to shift higher even if I could.
Andersons power curve does, however.
mk
power curve doesnt pay to shift higher even if I could.
Andersons power curve does, however.
mk
#5
Three Wheelin'
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cam buckets and the timing belt are the limiting factor.
solid buckets will extend your range upwards of 8000 rpms plus. Greg Gray is using solids in his 16V engines down under.
I have a contact that builds buckets for high HP/rpm record holding ricer engines that will guarantee an additional 1k rpms over the stock hydraulic buckets---I know, you said 928 only but he will make some for any engine including 928--he doesn't care what you're building.....
very good pieces, very expensive.
the was talk some time ago about a new Gates belt that is reported to be much stronger--as to higher rpms....I can't say. not enough info as yet.
rpms do not come cheap.....
--Russ
solid buckets will extend your range upwards of 8000 rpms plus. Greg Gray is using solids in his 16V engines down under.
I have a contact that builds buckets for high HP/rpm record holding ricer engines that will guarantee an additional 1k rpms over the stock hydraulic buckets---I know, you said 928 only but he will make some for any engine including 928--he doesn't care what you're building.....
very good pieces, very expensive.
the was talk some time ago about a new Gates belt that is reported to be much stronger--as to higher rpms....I can't say. not enough info as yet.
rpms do not come cheap.....
--Russ
#6
Former Vendor
I generally move the rev limiter to 7500 when I tune, on my custom engines, although there is little reason to rev these engines this hard. We are severely "camshaft" limited and most of the engines are well past the place where it makes sense to shift, long before this.
#7
Three Wheelin'
My "soft" rev limiter is set to 6600 RPM and I hit it sometimes, but try not to. Steel rods, no special lightweight internal parts. HP curve is still climbing at 6600, but I don't want to risk breaking anything by going higher to find the peak. The "stroker" engine blocks do have a tendency to crack. The solid spacer between the engine block and oil sump I devised should help stiffen the block, but I don't have the funds to be experimental. Don Hanson with the same internals except he had Ti rods ran his to 7200 RPM.
Last edited by Louie928; 08-14-2009 at 04:35 PM. Reason: Added pertinent information
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#8
Three Wheelin'
Join Date: Jun 2005
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Hi
Standard 928 S2 engine - 310hp (no work done and 142,000 miles)
Rev limiter moved up to 9710 by John Speake.
Have run at over 8000 a few times on Nitrous...but only for 10 to 15 seconds a time....no problems at all..
My shift lights are set at 7500 so I can shift then if I wish...
I seem to gain no more power over around 7800 so I usually shift at somewhere around 7700 ish...
All the best Brett
Standard 928 S2 engine - 310hp (no work done and 142,000 miles)
Rev limiter moved up to 9710 by John Speake.
Have run at over 8000 a few times on Nitrous...but only for 10 to 15 seconds a time....no problems at all..
My shift lights are set at 7500 so I can shift then if I wish...
I seem to gain no more power over around 7800 so I usually shift at somewhere around 7700 ish...
All the best Brett
#10
Without having solid lifters or high compression 12-13:1 our engines will run out hp b4 they hit 7k! A balanced and Blueprinted BBC will hit 9-10k. If you have the funds anything is possible!
#12
Nordschleife Master
Maybe I remember wrong, but didn't MarkA run his 16v motor over 8k?
Below is a cut and paste from JME racing,
8SR-14 for 944 performance/928 race
Best power band 4000-6900 rpm. 1000 rpm idle. .503 cam lift (In & Ex) with near stock base circles. Uses 944 Turbo or race valve springs (recommended) for best results. Motronic chip must have rev limit raised for best results. 25+ bhp over stock camshaft with race exhaust. Needs custom Motronic chip or aftermarket engine management. No equivalent competitors cam. Used where lift is un-restricted but racing cam is allowed.
B13-10, B13-14 for 944 race/928 race
Best power band 4400-7200 rpm. 1100 rpm idle. Off idle lope. .539 cam lift (In & Ex). Modified hydraulic lifters required. Race valve spring & retainer package required. Motronic will not work. Bhp available depends upon tune of engine. No equivalent competitors cam. Used where lift is un-restricted but racing cam is allowed. RH B13-10 has better midrange power, RH B13-14 has better top end power.
Race Solid Lifter RS 304M2/280M-10 for 944/928
Best power band 5000-8200 rpm. 1300 rpm idle. Off idle lope. .595 cam lift In, .510 Ex. Race solid lifter, valve spring & retainer package required. Motronic will not work. After market engine management only. Bhp available depends upon tune of engine. No equivalent competitors cam. Used where lift is un-restricted but racing cam is allowed. Best results with unrestricted intake, fully ported cylinder head with larger valves, racing header.
#14
Nordschleife Master
Thread Starter
Based on this math, with the standard 78.9 stroke, one could run Simard's short block much higher, at least to 9000 rpm. His dry sump etc. might really make this possible in reality as well.
Sterling, how did you determine the number 7200 rpm? I am looking at your short block and I don't understand what would limit you to 7200 rpm. Is it all valvetrain that is limiting you? Or do you mean that you get no benefit from spinning above 7200 rpm?
Sorry I don't remember the exact numbers offhand, but of the ones that I've heard of so far, the highest is one going somewhere over 8,000 RPM, and making over 800hp up there. That was the crankshaft horsepower, not rear wheel horsepower, as measured on an engine dyno before the engine was installed in the car. The engine's normally asprated, right around 6.5 liters, is steel sleeved, has an individual throttle body type intake, with coil on plug ignition.
cam buckets and the timing belt are the limiting factor. Solid buckets will extend your range upwards of 8000 rpms plus. Greg Gray is using solids in his 16V engines down under. I have a contact that builds buckets for high HP/rpm record holding ricer engines that will guarantee an additional 1k rpms over the stock hydraulic buckets---I know, you said 928 only but he will make some for any engine including 928--he doesn't care what you're building..... very good pieces, very expensive.
I generally move the rev limiter to 7500 when I tune, on my custom engines, although there is little reason to rev these engines this hard. We are severely "camshaft" limited and most of the engines are well past the place where it makes sense to shift, long before this.
My "soft" rev limiter is set to 6600 RPM and I hit it sometimes, but try not to. Steel rods, no special lightweight internal parts. HP curve is still climbing at 6600, but I don't want to risk breaking anything by going higher to find the peak. The "stroker" engine blocks do have a tendency to crack. The solid spacer between the engine block and oil sump I devised should help stiffen the block, but I don't have the funds to be experimental. Don Hanson with the same internals except he had Ti rods ran his to 7200 RPM.
How often do the stroker blocks break? Is this because of the longer stroke or because of something else?
Your spacer: Are you talking about just the oil pan spacer ring or a whole web a la Simard?
Hi Standard 928 S2 engine - 310hp (no work done and 142,000 miles) Have run at over 8000 a few times on Nitrous...but only for 10 to 15 seconds a time....no problems at all.. My shift lights are set at 7500 so I can shift then if I wish... I seem to gain no more power over around 7800 so I usually shift at somewhere around 7700 ish... All the best Brett
Why not higher? No benefit?
Let's see if he chooses to join the thread.