Reversed Engine Orientation

Technical discussion, questions, answers and information regarding the F600

Is a reversed engine orientation acceptable for F 500 cars with a motorcycle engine?

Poll ended at Tue Aug 26, 2014 7:59 pm

YES, a reversed engine orientation is OK
2
25%
NO, adopt the two stroke prohibition
6
75%
 
Total votes: 8

Bill Butterworth
Posts: 24
Joined: Thu Nov 05, 2009 5:40 pm

Reversed Engine Orientation

Postby Bill Butterworth » Tue Aug 19, 2014 7:59 pm

I am currently designing and building an F 500 car with a motorcycle engine. The design is based on a reversed engine orientation (exhaust ports to the rear). I had a verbal OK from the SCCA, but was told to submit a request in writing. The response today to my written request was that even though the motorcycle engine rules don't prohibit this design (as they do for the two stroke engines) the design would probably not be acceptable because of the rule regarding the two stroke engines. It was suggested I submit a proposed rule change to the Club Racing Board. Before i do that I would like to know if the F 600 community is in favor of allowing this approach.

My reason for this design approach is driver safety. The reversed engine orientation moves the exhaust manifold away from the fuel cell and the driver's back and repositions it over and behind the rear axle. Moving the exhaust manifold allows for a shorter engine bay (< 20"). This in turn allows the pedals and the driver's feet to be positioned behind the front axle line as is done in most other classes of racing. I believe both of these changes improve driver safety.

My understanding of the reasoning behind the rule in the two stroke section is to prevent a performance advantage. There is no competitive advantage to this approach for the motorcycle engine. The reversed engine orientation reverses the rotational direction of the drive train. A jackshaft is required to re-reverse this rotation. This causes additional losses and costs horsepower. The engine is unmodified, and the final drive from the jackshaft to the solid rear axle uses the standard roller chain design approach. No existing designs are made uncompetitive by this design.

I would appreciate your thoughts and comments regarding this design so I can decide if it makes sense to propose it to the rules committee.

Thanks,

Bill Butterworth

Rick Eskola
Posts: 56
Joined: Fri Oct 13, 2006 11:22 am

longitudinal

Postby Rick Eskola » Sat Aug 23, 2014 9:41 am

How about longitudinal? My thoughts were to mount engine in longitudinal and run a short driveshaft to a quick change rear end.
I found a company who builds one that meets our one piece axel rule.

It most definitely is not a performance advantage, (sucks up some HP, and adds weight.) but it would be another option that I would like to try. The only advantage I could see, would be getting the header away from the fuel cell, not having to deal with chains and sprockets, and maybe a cost savings on replacement chains and sprockets.


What's your thoughts!

Rick Eskola

Jay Novak
Posts: 1423
Joined: Thu Mar 15, 2007 10:08 pm
Location: United States, Michigan, Dearborn

Postby Jay Novak » Mon Aug 25, 2014 11:09 am

IMO there is a significant advantage to the reverse engine package and it has to do with engine cooling. This is not to say that it would be an easy implementation.

I would not have done our reversed engine in our original RaKaVon if I was not certain that it provided an advantage. The only reason we changed the design was because of the rules change.
... Jay Novak
SCCA member for 48 years
A special thanks to all SCCA workers

Chris Ross
Posts: 286
Joined: Sun Jul 22, 2012 3:20 pm

Postby Chris Ross » Mon Aug 25, 2014 10:33 pm

I can see numerous advantages to spinning it around. You would have to incorporate a gear box to reverse the drive to the rear axle, but a properly done gearbox will have a very small efficiency lose. It would add to the cost/complexity too so from that standpoint I am against it.

Bill Butterworth
Posts: 24
Joined: Thu Nov 05, 2009 5:40 pm

Reversed Engine Orientation

Postby Bill Butterworth » Tue Aug 26, 2014 1:21 am

This design does not have to be costly or complex. Two idler sprockets and a longer chain will do it. Even using two gears is not complex or expensive. This was designed with this low cost F5 class in mind.

Regarding cooling, the excess energy given off as heat is the same regardless of the engine orientation, and the volume of the engine bay and the components in the engine bay are very similar. Thus the problem to be solved is the same regardless of the engine orientation. If the exhaust system gets too hot, duct more cool air over it. That's my plan.

Thanks, Bill Butterworth

John Rounds
Posts: 2
Joined: Tue Oct 09, 2012 6:35 pm
Contact:

Postby John Rounds » Tue Aug 26, 2014 10:45 am

Please explain how to reverse the rotation of the engine/trans with idler sprockets and a longer chain. I am not grasping the engineering.

John Rounds

Scott Newton
Site Admin
Posts: 532
Joined: Mon Dec 29, 2008 9:01 am
Location: United States, New York, Chittenango

Postby Scott Newton » Tue Aug 26, 2014 12:12 pm

The way you would do a reverse drive chain is to have one of the two sprockets be outside the chain loop. In order to get adequate tension on that sprocket, you'd need to use two idler sprockets either side of it. It's not uncommon to see an automotive serpentine belt reverse drive an accessory or two this way.

For example: Image

The middle sprocket of a bike's rear derailleur system spins the opposite way.

No idea or comments though on if the advantages in packaging such a system would outweigh the disadvantages of the drivetrain power losses. If your setup uses a jackshaft in front of the engine already however, the drivetrain losses would be minimal (if any) since it would actually package better IMHO.

Bill Butterworth
Posts: 24
Joined: Thu Nov 05, 2009 5:40 pm

Postby Bill Butterworth » Tue Aug 26, 2014 1:21 pm

Scott - Thanks for the explanation and example. Hopefully this will help people understand the concept.

Chris - Does Scott's explanation help allay your concerns about cost and complexity? McMasters stocks all the parts at low prices.

Thanks, Bill Butterworth

Jay Novak
Posts: 1423
Joined: Thu Mar 15, 2007 10:08 pm
Location: United States, Michigan, Dearborn

Postby Jay Novak » Tue Aug 26, 2014 1:42 pm

Reversing the drive directions with chain idlers is certainly possible. However to say there are no advantages to this system is simply wrong. I will not go into the advantages as they are based on my own engineering and experimental testing.

Fact: There are significant advantages.
... Jay Novak
SCCA member for 48 years
A special thanks to all SCCA workers

Bill Butterworth
Posts: 24
Joined: Thu Nov 05, 2009 5:40 pm

Postby Bill Butterworth » Tue Aug 26, 2014 3:31 pm

Jay - I've tried to be open and straightforward regarding my reasons for advocating this design and what the pros and cons are. If there are significant advantages to this design please tell me and the rest of the F600 community so we can learn from your engineering and testing experience. When this topic has been raised in this forum earlier your position was that such a design is feasible but that a direct drive approach is better.

If this proposal is accepted, your knowledge and insight will have once again helped the F600 community. If this proposal is not accepted, you have lost
nothing by sharing your information. Without your information, this just becomes an argument without facts.

Thanks, Bill Butterworth

Chris Ross
Posts: 286
Joined: Sun Jul 22, 2012 3:20 pm

Postby Chris Ross » Tue Aug 26, 2014 5:00 pm

Jay already did it with the two stroke engine. He was the one who caused the rule to be implemented. He designed, built, and raced the car. The car was protested and the powers at be determined the car to be legal. However, after the powers at be studied his car they decided the competitive advantage the car had would quickly obsolete all other cars. To prevent this from happening the rule was implemented to make it illegal to turn the motor around. While it is perfectly legal to build a MC engine car with it turned around, I would expect the rule to be immediately "clarified" by the BOD to make it illegal.

Jay is a very smart car designer. He doesn't give up hard earned secrets very easily! :D

Chris Reinhardt
Posts: 1195
Joined: Sun Dec 04, 2005 12:18 pm

Postby Chris Reinhardt » Thu Sep 04, 2014 9:16 am

Just a simple observation.... Turning the engine around puts the headers at the rear of the car, taking heat away from the firewall/Fuel cell.

The other advantage I can see would be header design... You probably could go straight back with headers, without a lot of turns...

Also makes a smoother air flow to the throttle bodies....

Diasio had a design with the motor mounted sideways and drove a quick change rear. Seems really over kill???

CR
CR2 MotorSports
Home of Cobalt Superkarts
www.cr2motorsports.webs.com

Scott Newton
Site Admin
Posts: 532
Joined: Mon Dec 29, 2008 9:01 am
Location: United States, New York, Chittenango

Postby Scott Newton » Thu Sep 04, 2014 9:31 am

An argument for allowing reverse orientation: Flipping the motor around would probably also help those with wheelbase concerns. With all the hot bits facing to the rear, you could feasibly have the motor sitting right up to the rear axle - and then you could push the jackshaft right back to the new front of the motor, and then the firewall right up to the jackshaft. The new limiting factor would be the length of the trailing arms you wish to run, and the jackshaft's orientation with them. If you're comfortable with a slight mismatch here (which should be safe to do), you could feasibly have the seat moved back several inches behind where it can be located on the 2 stroke powered cars.

Because there wouldn't need to be anything forward of the jackshaft, you could have the jackshaft and fuel cell/firewall in very close proximity - in fact you would probably want the jackshaft right next to the firewall so you can use that bulkhead as a mounting point for the idler pulleys.

Really for both the 2 stroke and the 4 stroke motors, a reverse orientation makes a lot more sense for many reasons... but the argument that got it banned from the 2 stroke cars (that it obsoleted too many old cars) will likely also get it banned from the 4 stroke cars (because it obsoletes so many 2 stroke chassis that could be used for conversions).

Chris Reinhardt
Posts: 1195
Joined: Sun Dec 04, 2005 12:18 pm

Postby Chris Reinhardt » Thu Sep 04, 2014 10:00 am

Scott Newton wrote: but the argument that got it banned from the 2 stroke cars (that it obsoleted too many old cars)


Isn't that what old cars are??? :D
CR2 MotorSports

Home of Cobalt Superkarts

www.cr2motorsports.webs.com

Jay Novak
Posts: 1423
Joined: Thu Mar 15, 2007 10:08 pm
Location: United States, Michigan, Dearborn

Postby Jay Novak » Thu Sep 04, 2014 10:15 am

I would prefer to see the wheelbase increased to fix any problems. A longer WB will help every car in the class including the 2 strokes.
... Jay Novak
SCCA member for 48 years
A special thanks to all SCCA workers

Jonathan Whorf
Posts: 112
Joined: Fri Jan 23, 2009 8:04 am
Location: United States, New Hampshire,

Postby Jonathan Whorf » Thu Sep 04, 2014 10:20 am

will likely also get it banned from the 4 stroke cars (because it obsoletes so many 2 stroke chassis that could be used for conversions).


Usually the rear clip gets replaced when converting a 2 stroke, so I would not think the reversed engine shouldn't really make a difference for that argument.


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