LS7 = 8500 rpm
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Originally Posted by jtsc23
On the right track here... The weight of the lifters can be controlled with some monster valve springs so that's not entirely the issue. Problem with the hydraulic lash adjuster is that at some point (~7500 crank rpm on type 5 valvetrains) the lash adjuster cannot respond fast enough to take lash out of the system. The internal check ball physically does not have time to return to it's seat. The rpm limit is of course dependent upon base circle diameter of the camshaft and the valve event durations. Large base circle diameter and smaller event durations give the check ball more time to recover. If the lash adjuster does not fully return each cycle, it will loose lash compensation each cycle in a ratcheting effect. End result is the lash adjuster "pumps down" making it unable to absorb lash and the valve slams closed on it's seat. Doesn't take long at 7500 rpm to break the valve then.
Teching In
Joined: Oct 2002
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From: B.C, MI
Just posted this in the "LS7 Fuel Economy" Thread:
"Just chatted with the engineer that is on the GM account. GM does spin the DoD lifters up to 7500rpm. They run a modified square wave test (idle to 7500rpm) and hold @ 7500rpm for 5 seconds. Test is repeated three times. They are only looking for part failure and not valvetrain dynamics. So in theory the DoD could go into the LS7. But the weight of the DoD lifter is still too high to get stable valvetrain dynamics so they won't put them in."
Also asked him how high GM spins the LS7. He said they run brief excursions to 8000rpm but again they aren't concerned with valvetrain dynamics only part failure. Durabilty runs are at 7000rpm. He confirmed threshold was 7500rpm for the LS7 hydraulic lifter. So brief 1/4 miles blasts where the rpm only touches 7500-8000rpm momentarily (no hanging rpm) are possible.
"Just chatted with the engineer that is on the GM account. GM does spin the DoD lifters up to 7500rpm. They run a modified square wave test (idle to 7500rpm) and hold @ 7500rpm for 5 seconds. Test is repeated three times. They are only looking for part failure and not valvetrain dynamics. So in theory the DoD could go into the LS7. But the weight of the DoD lifter is still too high to get stable valvetrain dynamics so they won't put them in."
Also asked him how high GM spins the LS7. He said they run brief excursions to 8000rpm but again they aren't concerned with valvetrain dynamics only part failure. Durabilty runs are at 7000rpm. He confirmed threshold was 7500rpm for the LS7 hydraulic lifter. So brief 1/4 miles blasts where the rpm only touches 7500-8000rpm momentarily (no hanging rpm) are possible.
Staging Lane
Joined: Jan 2005
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Originally Posted by fastta
NASCAR motors are rebuilt after every single race.
Something else to consider is that they have all of the bearings, cylinder walls, piston skirts, cam lobes, valve stems etc, impregnanted with teflon. For some strange reason, the average guy running a street/strip car willl spend $2K on a set of heads, but will not spend $200-300 to protect all of these components.
Launching!
Joined: Nov 2001
Posts: 254
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From: NC
Based on the advertised rev limit of 7000 rpm, and my past experience with GM racing engineers, you can usually add 400rpm safely to the factory limit. In the past, this has been 6500rpm for a stock 97-00 ls1, 6900rpm for an 01-04 ls1/ls6 (due to the new rod bolts), and I'm going to guess 7400rpm for the LS7. I wouldn't want to rev it past a safe range, even if if breathes well enought to do so. Hopefully, LS1 edit will be available for it near release!
Launching!
Joined: Nov 2001
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From: NC
As I understand it, the LS2's will run the same cam as the LS6 WC engines have run, the "Gib" cam (replaced the ASA in our series). I think it is the cam you mention, but don't have the part # handy.
the rules aren't in print yet.
the rules aren't in print yet.
Originally Posted by Bink
Dave - new car looks GREAT!! Will you run the 239/251 cam in the new motor??
Ooops, sorry not trying to hijack the thread.
Ooops, sorry not trying to hijack the thread.
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TECH Junkie
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From: its fucking cold
Originally Posted by FaSS Blac
The Ferrari Tipo 049 engine has a bore of 3779" and a stroke of, (sit down!!!) 1.629"!!!!!!!!!!!!!!!!!!!!!! 
Do you guys see the correlation between big bore, small stroke now? You are NOT going to spin a 4.000" stroke engine to 18,000 rpm!!!! 
Or make over 800 HP with a 183 ci engine!!!!!!
Do you guys see the correlation between big bore, small stroke now? You are NOT going to spin a 4.000" stroke engine to 18,000 rpm!!!! Or make over 800 HP with a 183 ci engine!!!!!!And that 183" F1 motor probably makes more than 1000 hp.
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the BMW and honda 3.0ltr engines from 2 seasons ago where reputed to make over 950bhp at over 19,000rpm for qualifing. they had to turn them down (ie revs) for last year coz they had to last the race aswell. and this year they will have to go even lower coz the engines need to last the whole weekend this season! so i recon about 750bhp at about 16-17K this year!
thanks Chris.
thanks Chris.
Staging Lane
Joined: Dec 2001
Posts: 85
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From: oregon
don't forget this engine has to survive on a roadcourse at high rpms at high load and varying g's.. or at least it should be able to..
unlike drag racing which only really requires a crazy 1/4 mile spurt at a time.. or street driving, where your not driving a 10/10 100% of the time (although street has its own set of requirements)
*rubs eyes* btw, I never noticed Dave Farmer here till now! (me oblivious)
unlike drag racing which only really requires a crazy 1/4 mile spurt at a time.. or street driving, where your not driving a 10/10 100% of the time (although street has its own set of requirements)
*rubs eyes* btw, I never noticed Dave Farmer here till now! (me oblivious)
Staging Lane
Joined: May 2004
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From: Morrison, Il
454 would spin 8600.
Originally Posted by LPCWS6
Old 4 bolt 454's with factory forged cranks and 7/16 rods are good to 7500 rpm on the bottom end. I don't see a little 8500 rpm action from time to time as that big of deal for the bottom end of this motor but I doubt the valvetrain could handle that kind of rpm's it without some work.
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Originally Posted by FaSS Blac
NASCAR engines are big bore, short stroke engines. Chevys are around 4.125" bore, 3.33" stroke. Bob weight is around 1492g, with pistons at 400g, and rods at 525g minimum weight.
That 4" stroke is a killer. Not only because of the piston speed but because of the angularity. Those Cup motors also have a high rod/stroke ratio.
With a 4.03 bore, my 355 (3.5" stroke) has 515gm 6" Honda-journal rods, 370gm pistons, 87gm pins, and a 36.25# crank. People who went with a 352 (4.155x3.25, we must use a 'stock' stroke) and used the Superfly pistons (320gms, maybe) and Maxi-light -1s or equivalent (485gm) end up with a 32# crank.
This sort of rotating assembly will cost $6-7000 in LS1 sizes. However the crank will be 50-60#. With that, the bottom end can handle the speed.
On the top you have lightweight high ratio rockers (increases spring leverage and reduces lifter/pushrod travel), light valves, lifters, double tapered pushrods, ICD Ti retainers, Ti keepers (saves 2gm), valve spring oilers, coated or micropolished springs of high quality (say $500-1000/set).
This sort of valvetrain will cost $5-7k. Speed costs money...how fast do you want to go?
The Cup teams custom order all their pieces in fairly large batches (how many rods do you think Hendricks, Roush, Everham, Childress, or DEE order at a time?) They are able do build custom setups that the rest of us can't.
Those F-1 engines are 300cc cylinder. The LS7 is 875cc. So there is a lot less stroke, not even counting the different bore/stroke ratio. With much better angularity. And even with a direct action DOHC valvetrain, they have to use pnuematic valve springs to rev that high.
David
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From: Atlanta, GA
Originally Posted by chuntington101
Suzuki Hayabusa. (with a 1.5ltr strocker crank and a rev limit of 11K) mean speed around 25ms-1
metro 6R4 3.0 V6 (very nice race engine that will rev to over 10K). around 25ms-1.
so i recon pushing over 26ms-1 will lead you into trouble. but if anyone KNOWS better then please tell me. shame though as i bet one of these things at 8K would sound very nice!
thanks Chris.
metro 6R4 3.0 V6 (very nice race engine that will rev to over 10K). around 25ms-1.
so i recon pushing over 26ms-1 will lead you into trouble. but if anyone KNOWS better then please tell me. shame though as i bet one of these things at 8K would sound very nice!
thanks Chris.
My view on high revs is "what's the point?" for a street car I preffer making power down low, but I can understand for heads up racing you want to make as much power per displacement as you can.....
-Adam
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From: Atlanta, GA
Originally Posted by chuntington101
Adam, do you know the stroke of your M3? i take its the 3.2ltr. if you do i can try and figure the mean piston speed and see what it is.
Thanks Chris.
Thanks Chris.
PS my motorcycle is 67.0mm x 42.5mm with a 15,000 RPM redline........see I'm so dumb I can't even convert metric to standard
-Adam
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From: Atlanta, GA
Originally Posted by AdioSS
My CBR-600RR
Piston Speed Rounded FPM: 4,183.071
Piston Speed Rounded FPS: 69.718
My M3
Piston Speed Rounded FPM: 4,773.333
Piston Speed Rounded FPS: 79.556
My Trans Am With a blown wrist pin
Piston Speed Rounded FPM: 0.000
Piston Speed Rounded FPS: 0.000
humph I really thought my CBR's pistons would have been moving faster than the M's....wow, guess not.
-Adam
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yeah, i know what you meen. when i figured out the speed for the Busa i was amazed that it was about the same as the 6R4's.
you dont need a calculater to do it.
mean speed is distance/time.
so figure out the time takes to complete 1 stroke - 1/(max rpm X2 /60)
and divide the sroke by that (in seconds). dead easy!
Chris.
PS. if i have got this wrong correct me, im not with it today!
you dont need a calculater to do it.
mean speed is distance/time.
so figure out the time takes to complete 1 stroke - 1/(max rpm X2 /60)
and divide the sroke by that (in seconds). dead easy!
Chris.
PS. if i have got this wrong correct me, im not with it today!
