Bink

Great explanation....Thanks.

jtsc23

Thanks - Sometimes I can pull something from butt that sounds intelligent. Most times it just a brrrrrt sound.

chuntington101

your right mate, that does sound very intelligent. so we can all say that the bottom and top end will probaly not take 8.5K. so what will it rev to??????

thanks Chris.

jtsc23

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.

BowtieFreak

Right, but when one considers that the engines spin 8000-8500 rpm for hours, not just 10 seconds, its an amazing feat. The goal is of course to get an engine to last all season with only replacing cheap components, and you would be surprised how many times bearings get reused today in them.

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.

Dave F

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!

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.

Dave F

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.

BlueSix

Now that's a big bore!!

And that 183" F1 motor probably makes more than 1000 hp.

chuntington101

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.

ynneK

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)

dvzz28

my old man raced big blocks for years with factory rods and crank and spun them 8600 rpm. he drag raced them bout 3 years between rebuilds. these modern motors should do it no problem.

DavidNJ

FaSS Blac, you are definitely on the right track. I believe the Cup cars are actually 4.155x3.335. There is a 525gm minimum? When I last looked they had qualifying piston-guided rods at 440gm in 300M. These engines also use lightweight pins and other pieces.

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

Shinkaze

FWIW my Honda CBR-600RR doesn't start to make power until 9,000 RPM and redlines at 15,000 RPM. Of course it's only 0.6 Liters so it doesn't ahve much mass to spin against. The smaller the bore displacment the easier it is to get a fast complete light off of the mixture so you can take the motor to higher RPM and generate higher HP/Liter. (my bike is pushing 200hp/Liter). For that reason I think HP/Liter is a BS measurement because it doesn't factor the overall package... At any rate my M3 starts making power at 5K-6,000 RPM and redlines at 8,000 RPM. I want to say I remember BMW claiming the e46 M3 had the fastest piston speeds (at 8,000 RPM) of any production street car on the planet (at that time....year 2000). I could be wrong.

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

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.

Shinkaze

It's 3.43" x 3.58" with an 8,000 RPM redline. I have no Clucking Flue how to compute piston speed off that data so I'll just sit back and be in awe of the egg heads on that one..

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

AdioSS

iTrader: (2)

use this http://www.csgnetwork.com/automotiveconverters.html

Shinkaze

Well that made it easy.

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

chuntington101

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!

98vert6spd

8500 and well have to call it the honda z06