I think there are two different mindsets between us. I feel eric and RBYCC both share a drag racing background while my engine background lies heavily in road racing. Both my mini and my Z have been gone over for that specific reason.

Couple things. When I talk about an engine's ability to rev, it is very dependant on free load revving. The ability for an engine to change rpm's quickly to downshift or upshift is paramount in maintaining traction when cornering, etc. Shocking the drive train with an engine with a heavy rotating mass at the front causes a loss of traction. No beuno.


Case and point, RBYCC, you said you were into drag racing back in the day? You remember when the big heavy A body chevy's with the tiny little 283's were running big heavy flywheels to get those giant bastards moving with the (relative to a BBC) tiny amount of torque those motors put out? You old guys spun those motors TIGHT. Lots of RPM's are not anything new.


For example: Below is an old V10 F1 crankshaft:

http://cr4.globalspec.com/PostImages...9C1419138D.jpg

If you'll notice there's a bunch of heavy metal in that crank, I.e. Tungsten, Bismuth, alloys thereof, etc. By heavy metal I just mean anything heavier than iron (X=22). This allows the crank weights to be much closer to the crankshaft centerline. Those of you fluent in physics should know this means that less energy is required to alter the rotational speed of the crankshaft because of this. These kind of things, featherweight flywheels, etc, are all pretty commonplace in road racing to allow the engine to free rev and therefore revmatch far more quickly than heavier crankshafts. Between autocrossing my mini (which was geared very short) with a standard weight cooper S crank, and after I had the thing lightened with a light flywheel, there was no comparison in the ease one had in getting up and down through the gears smoothly.

In straight line acceleration though, RBYCC is correct and transient torque and the gearing in a car are both very important to how freely an engine will rev under load.


For RBYCC, it's indiana, surprisingly the BBC's and F's I've built around here are for a locak truck puller or two. 468ci is really common due to class restrictions but they live at a pretty constant 7.5k-8.5k depending on what they want to turn them to get the wheel speed they're looking for. At this point it's all in valve train stability. People that don't think pushrod engines can turn tight are idiots. It's just harder to get the GIANT valves that (especially hemi's) rat motors and elephant motors run to reliably close and show no floating. I found that chevy's almost always required a line bore to get into factory specs while Ford's seemed much closer. I ran/run windage trays to keep the foaming down but relatively heavy dampers since they saw a TON of shock loading on those motors and they need to survive.

If you'll notice, the valve train of the M104 is fantastic. The flaw in turning one lots of RPM's is in the hydraulic lifters. Always will be. Compared to other factory I6's (S54 aside), it has relatively small counter weights and can rev sort of freely, but the cams are pretty restrictive (224 deg on the factory intake is pathetic) and the hydraulic lifters aren't exactly the best, and limit ramp angles and maximum valve acceleration.

Pity.

Appreciate you further explanation and clarification...
My response initially was that you were focusing soley on the crank as the component that was responsible for how quickly an engine can rev to redline.

Lot of other stuff involved as you noted in this post.

I still like older setups because they are simplistic...especially push rod engines.
Only to remember the Group 7 CanAm or Formula 5000 builds.

As I posted earlier I prefer the M103-12V for it's simplicity.

Back in the day for me was the mid 60's....
Ran a second tier Chrysler Factory car over a period of six years...
Unfortunately and sadly for me not a lot of pix still exist.
1964 A864 Dodge 330 light weight with the max performance hemi which made its debut in SS/AA and ended up in SS/CA in the early seventies.

The Hemi was an engine that wound up very quickly and had no problem with any of the valve train in spinning up to 9K+ RPM.

Road racing..ran a 1966 Aston Martin DB6 Vantage spec..4.0L 325HP DOHC I6 with triple Weber 45DCOE's in SVRA.
Occasionally ran a 3.8L Jaguar Mark II sedan .
Neither were high RPM engines....

Like RBYCC said: "You have to live with the basic design that the manufacturer provides. All else is esoteric textbook BS...". And like Maggie said: "The ability for an engine to change rpm's quickly to downshift or upshift is paramount in maintaining traction when cornering, etc." And since we are indeed basically stuck with what the factory provided us, I think the V8 has an advantage with it's shorter, lighter crank. I can't wait for when Maggie posts those crank shaft weights. And yes, I understand the desirability of keeping the crank counterweights as close to the crankshaft centerline as possible but again, us poor slobs are stuck with just the relatively mundane, pedestrian, standard issue OEM street stuff, I think the overall weight of the crank is the bigger issue for us. And those I6 cranks are HEAVY. At least the strong ones are. The only ones you would want to run anyways. Another thing to remember, reducing the number of counter weights on those things increases the loads on the bearings so you can't go there either. Well you can I guess but the engine won't live as long.

Also wanted to update some info I posted a night or two ago about the Big Three diesel pick-ups. I just read in the new "Diesel Power" magazine a three way comparison on the latest trucks and it looks like the two V8 diesels are out performing the I6 by a decent margin now. (It only took them about 22 years!) Not too relevant here but again, it's hard to find ANY I6 vs. V8 stuff anywhere.

And for the record, I've done some circle track racing too at El Cajon, the very track that Jimmy Johnson cut his teeth on, a track that is, unfortunately, like so many tracks, gone now.

Speaking of getting the power to the ground, I just read that BMW has now finally as of the 2011 M.Y. put a five link rear suspension design into production. Look-out, they're gaining on M.B. now! They're adopting a design that M.B. brought out in the 1984 M.Y. on the 190E! Contrast this to the days when it was M.B. cribbing BMW's semi trailing arm rear suspension design.

BTW, it's still "RPM" Maggie, not "RPMs" :P:P:P
Regards, Eric

I cut and pasted to make this easier.

Can someone want to school me on this? If not can you recommend a decent site or better yet some books on this?

Try to give you a very basic concept...

Let's use the AMG 5.4L Kompressor engine.
I have this engine in a 2005 G55K.
It drives thorugh an automatic transmission and three ( front, center, rear ) differentials.
The same engine in a 2005 E55 drives through an automatic transmission and the rear differential.

The additional power transmission items in the G55K drive train create more loss then the lesser number of items in the E55.

Simply put the same engine with more losses will not rev as freely as the engine with less drive train/chassis losses.