Go USF1 !!

Richard Casto · **Posted:** Tue Nov 24, 2009 7:49 am

Arthur McDonald wrote:

How did we get here in an F1 thread?

Is anybody else planning to attend the Daytona 24 Hrs? Jan 30-31. It is NOT too early to book your hotel rooms.

I think I hijacked my own thread? :oops:

clinehall · **Posted:** Tue Nov 24, 2009 7:51 am

Arthur McDonald wrote:

How did we get here in an F1 thread?

Is anybody else planning to attend the Daytona 24 Hrs? Jan 30-31. It is NOT too early to book your hotel rooms.

I was thinking about that, I keep saying I'm going to go but haven't. This year is so frigging busy.

Todd Breakey · **Posted:** Tue Nov 24, 2009 9:49 am

Jason Mauldin wrote:

Marty Howard wrote:

Richard Casto wrote:

Thats OK Graham. I really can tell that you are a bit defensive about the pushrod dinosaur in the Corvette. But hey, if people want to tell me how good the pushrod engines are, just let them run the same displacement as everyone else. Then come talk to me. I like this chain yanking thing!

oooo...oooo...can I play too.

How about keeping the engines the same Physical size. Kind pointless to say displacement is smaller when the engine itself is twice the size and weight.

Hrmmm smaller displacement or smaller engine? I know which one I'd pick for a race car.

Hell, the 4.6 SOHC in my Mustang is bigger dimensionally than the 427 that Ford put in the Cobra. Just goes to show that bigger isn't always better (that's what I keep telling myself anyway.)

Marty Howard · **Posted:** Tue Nov 24, 2009 10:10 am

RobLupella wrote:

I like this. I want to see a mix. Let's have the DP or LMP type cars run. Also let's have the GTs, Porsche, Corvette, Ferrari, Masserati, Aston Martin. Then something like the old TransAm class with Mustang, Camaro, Challenger. GT2 or GT3 where we have BMW M's, Pontiac GTO-R, Mercedes xxx, etc... Let's make it entertaining

Agreed, I would love to see a truely stock series. Group them by Price and production numbers instead of Drive train and power. That way people can honestly say "hey, that's the fastest $20K around"

Richard Casto · **Posted:** Tue Nov 24, 2009 10:13 am

Actually for low center of gravity, I prefer a flat six...

Seriously, I understand that each design has it's advantages and disadvantages. The V8 is a good all around design. If it wasn't it wouldn't be so popular. I can't speak as to why the Ford OHC engine is so tall. Other manufactures seem to be able to make quite compact OHC V8 engines.

Jason Mauldin · **Posted:** Tue Nov 24, 2009 10:27 am

Richard Casto wrote:

. I can't speak as to why the Ford OHC engine is so tall. Other manufactures seem to be able to make quite compact OHC V8 engines.

Who?

Donnie Barnes · **Posted:** Tue Nov 24, 2009 11:49 am

Flat 12 FTW!!!1!

Everyone says they want a stock series, but do you REALLY think that makes sense? Each year it would be dominated by ONE car. There's simply no way around that.

I think the SCCA "showroom stock" rules are as close to actual stock as you can reasonably get, and even they have competitive adjustments. *shrug*

--Donnie

Richard Casto · **Posted:** Tue Nov 24, 2009 12:52 pm

Jason Mauldin wrote:

Richard Casto wrote:

. I can't speak as to why the Ford OHC engine is so tall. Other manufactures seem to be able to make quite compact OHC V8 engines.

Who?

Ok, I will admit to overstepping here as I can't give good specific example (not that I don't believe they exist). So let me back down and rephrase...

"I can't imagine that the Ford example above is the most compact OHV design that can be done."

There is no one perfect design. So if you want the things that an OHC engine gives you (general the ability to rev higher) then you have to give up some height of the long block.

You can build a short OHC design. I think the Honda SOHC non VTEC heads are an example of this. The cam is low and uses rocker arms to actuate the valves. But if you want to do tricky things such as optimal profiles for each valve, variable valve timing, etc. (all of which bring additional performance advantages) you typically have to move the cams ups over the valve stems which increases the height of the long block.

I also think everyone gives too much weight or importance to the "long block" height and compactness. It would be interesting to see what the total difference is between a pushrod engine and OHC engine once you factor in things like intake, throttle body and other plumbing. Is it worth everything you give up by not using an OHC?

For example here is the Corvette LT5 DOHC engine which shows that it's not the extra valvetrain parts that eats up the space...

Basically where I am going with this is that the majority of the production auto and race engines seem to have gravitated to OHC engines for a reason. The benefits of OHC (more power via revs, ability to do more tricks with the valve timing, more flexibility on head design, and maybe even more fuel efficiency via the above items) seem to outweigh the benefits of pushrod OHV (more compact long block, simpler valvetrain, lower overall height of long block, lower center of gravity, lower cost via fewer parts).

IMHO, the only reasons you see pushrod engines in racing environments are for the following reasons...

1. The rules require it (ala NASCAR)
2. Equivalence rules for pushrod engines result in a performance advantage (ala 1994 Mercedes Indy engine)
3. Stock block requirements for production based engines
4. Marketing

IMHO, GM races the Corvette with a pushrod engine because of #3, #4 and #2 (maybe even in that order). When given a straight up displacement rule for a NA purpose built race engine, nobody is going to use a pushrod valvetrain.

Chevy and Corvette fans may give all kinds of reasons as to why the Corvette street car still has a pushrod engine. My opinion is that it all boils down to ...

1. Historic continuity of identifying feature.
2. Cost

The Porsche 911 is a perfect example of #1. I can't imagine Porsche EVER moving the location of the engine in the 911 for marketing reasons. The 911 faithful want to keep it as is. Just like the Corvette faithful like the pushrod engine (does it also still have the transverse rear spring as well?) I am a Porsche fan, but I consider the engine location in the 911 to be just as archaic (if not more so) than the pushrod engine in the Corvette. Sure, both GM and Porsche make both work VERY well, but both features do not exist for engineering reasons.

One day I do expect the Corvette to loose the pushrod engine. It has been done once already with the LT5 DOHC engine. It will happen again. It is just a matter of time. I suspect that at some point it will just be cost that causes the change.

Richard Casto · **Posted:** Tue Nov 24, 2009 2:08 pm

I have probably overshared with respect to my opinions about pushrod engines, etc. Others are probably tired of hearing about it. I think I am about talked out myself.

So... back on topic (USF1)

Does anything think that potential USF1 driver Jose Lopez looks a bit like our own Jason Mauldin?

RobLupella · **Posted:** Tue Nov 24, 2009 2:13 pm

I think racing engines are also ohc because there are a lot of series that run small displacement engines at 4,000,000 rpms and can keep it geared up consistently to stay in the powerband.

I'm not sure that the Corvette will ever or in the near future lose its pushrods. It is less expensive, it produces a bunch or hp, and it is hard to get that much torque out of an ohc motor.

It sounds good too :-)

Richard Casto · **Posted:** Tue Nov 24, 2009 2:30 pm

RobLupella wrote:

I'm not sure that the Corvette will ever or in the near future lose its pushrods. It is less expensive, it produces a bunch or hp, and it is hard to get that much torque out of an ohc motor.

It sounds good too :-)

Last hijack (maybe)...

All things being equal, I don't think cam location has any effect on torque. With the Corvette, it is mostly displacement that generates that torque.

They do sound good. When I was at the Petit LeMans, the large displacement V8 cars were ear bleeding loud. Particularly the Corvettes.

Michael Westerfield · **Posted:** Tue Nov 24, 2009 2:34 pm

Richard Casto wrote:

1. Historic continuity of identifying feature.
2. Cost

The Porsche 911 is a perfect example of #1. I can't imagine Porsche EVER moving the location of the engine in the 911 for marketing reasons. The 911 faithful want to keep it as is. Just like the Corvette faithful like the pushrod engine (does it also still have the transverse rear spring as well?) I am a Porsche fan, but I consider the engine location in the 911 to be just as archaic (if not more so) than the pushrod engine in the Corvette. Sure, both GM and Porsche make both work VERY well, but both features do not exist for engineering reasons.

One day I do expect the Corvette to loose the pushrod engine. It has been done once already with the LT5 DOHC engine. It will happen again. It is just a matter of time. I suspect that at some point it will just be cost that causes the change.

If it were me I would not put those two arguments together.

IMO Chevy has created a compelling reason why not to use a OHV configuration. They have been able to make as much power as needed with pushrods while maintaining a lighter package that has a lower center of gravity. I think they have shown that it doesn't make any sense to use an OHV technology.

I don't see a compelling reason why Porsche has continued to use the topology found in the 911 other than that is what the marketplace wants. Hell, even they tried to replace the 911 with the 928 and it was the consumer that stopped that rejecting the better handling, faster 928.

Richard Casto · **Posted:** Tue Nov 24, 2009 3:05 pm

Michael Westerfield wrote:

Richard Casto wrote:

1. Historic continuity of identifying feature.
2. Cost

The Porsche 911 is a perfect example of #1. I can't imagine Porsche EVER moving the location of the engine in the 911 for marketing reasons. The 911 faithful want to keep it as is. Just like the Corvette faithful like the pushrod engine (does it also still have the transverse rear spring as well?) I am a Porsche fan, but I consider the engine location in the 911 to be just as archaic (if not more so) than the pushrod engine in the Corvette. Sure, both GM and Porsche make both work VERY well, but both features do not exist for engineering reasons.

One day I do expect the Corvette to loose the pushrod engine. It has been done once already with the LT5 DOHC engine. It will happen again. It is just a matter of time. I suspect that at some point it will just be cost that causes the change.

If it were me I would not put those two arguments together.

IMO Chevy has created a compelling reason why not to use a OHV configuration. They have been able to make as much power as needed with pushrods while maintaining a lighter package that has a lower center of gravity. I think they have shown that it doesn't make any sense to use an OHV technology.

I don't see a compelling reason why Porsche has continued to use the topology found in the 911 other than that is what the marketplace wants. Hell, even they tried to replace the 911 with the 928 and it was the consumer that stopped that rejecting the better handling, faster 928.

Agree with you somewhat. I don't think the pushrod design choice is what makes the Corvette good. I am not sold on the "lighter package" and "lower center of gravity" arguments. I think those same two goals could be achieved in other ways. I still believe that GM is using the pushrod engine for the reasons I list. The others just end up being freebies that come along for the ride and are viewed after the fact as justification for the pushrod design.

Regardless, I do think the Corvette is a more complete "package" from an engineering point of view than the 911 is. My view is the 911 makes more compromises from an engineering point of view with the rear engine placement. It is sad because many features of the 911 are brilliant such as the new DFI engine and the PDK transmission.

I expect to see DFI in the Corvette soon as they are not allowed to use DFI in GT2 racing while Porsche are. I believe GT2 rules require it to be in the production car in before it can be in the racing car. DFI seems to give both more power and better economy all at the same time. This works in both a road and race car.

Jason Mauldin · **Posted:** Tue Nov 24, 2009 4:44 pm

Richard Casto wrote:

Agree with you somewhat. I don't think the pushrod design choice is what makes the Corvette good. I am not sold on the "lighter package" and "lower center of gravity" arguments.

Find a lighter engine that produces the same hp, in a non-exotic car.

Quote:

I think those same two goals could be achieved in other ways.

For example???

Quote:

I still believe that GM is using the pushrod engine for the reasons I list. The others just end up being freebies that come along for the ride and are viewed after the fact as justification for the pushrod design.

Let's not forget that GM also designed this engine for their trucks which are likely sold 10:1 to their v8 powered cars. Honestly, your reasons are probably not even in the top 5 reasons why GM still uses the superior pushrod engine.

I bet it starts more like this.

1) Cost
2) Ease of manufacturing
3) Use of existing knowledge base

P.S. someone should split the engine bench racing vs the race fan discussion.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

Jason Mauldin wrote:

Richard Casto wrote:

. I can't speak as to why the Ford OHC engine is so tall. Other manufactures seem to be able to make quite compact OHC V8 engines.

Who?

A Windsor block 5.0 (the pushrod motor) is quite oversquare: 4" bore x 3" stroke. The 4.6 OHC motor is about square: 3.552 in bore x 3.543 in stroke. The rest of the height difference is in the heads. I'm guessing that the OHC motor's longer stroke was an attempt to retain the old motor's torque characteristics.

OK, back to the my own attempt to hijack this thread. The 24 hrs is the only international pro race between now and February, so there's a lot of well known drivers, and there's a Koni Challenge race on the Friday preceding the big race.

http://www.daytonainternationalspeedway ... ytona.aspx

The 4 day Thursday-Sunday pass is $90. "This all-inclusive pass allows daily access to the infield and grandstands to enjoy all four days of action and includes Sprint FANZONE, garage access, daily infield parking, plus a Rolex 24 event hat. "

THSCC Forums

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