Latest F600 CRB Proposal

[sathorp]

Posted by Jay Novak on the SCCA F500 & FModified Facebook Page
January 1 at 10:48 AM

Ok guys let’s get together to save the F500 class. As you know under the new rule the 593 engines simply cannot live long enough to be competitive for a long enough time period to be a functional and low-cost engine for F500. Hp is not the problem imo. The problem imo is that the engine, with the inlet restrictors, must turn 8800+ rpm to make the needed power and the resulting imbalance forces causes the crankshafts to fail, and or the crankcase to crack.

How to fix this and make it so that the 593 can be both competitive and live. I propose the following basic concept.

1. Implement an Rpm limiter that limits the maximum engine Rpm to 8300 rpm. This will significantly reduce the imbalance forces and the Rocking couple of the engine. Thus, reducing or eliminating crankshaft and crank case failures Please note that the production 593 engines all make their power at about 8200 rpm. Thus the 593 should then live just like the production engines do. The stock ecu can then be recoded to a max rpm of 8300 or an aftermarket rev limiter can be installed for about $150

2. Remove the current mandatory inlet restrictors that are in the intake boot, this will allow the engine to produce 112 to 116 hp

3. The biggest downside to this concept is that it will might require a new pipe to be developed

4. I will also propose that the 494 and the 493 engines be allowed twin pipes but no internal mods allowed

I think that this proposal just might save F500 as an SCCA racing class, if we do nothing the class will be gone within 2 years as the current entry numbers are very poor.

Please post your comments here or send me an email to jaynovak@comcast.net. I welcome any ideas or suggestions.
I should have some dyno data in a week or 2.

Perhaps we can form an Ad Hoc committee too

Please help save this great class! Any and all comments

I am preparing a letter to the FSRAC & CRB that imo will greatly reduce the complexity of optimization of the 2-stroke package.

FYI

[B17overhead]

Seems like this collection of well-researched ideas may solve a lot of problems.

[Daryl DeArman]

I like the idea of not using inlet restrictors to restrict HP. The unintended consequence is all too often an increased operating RPM to obtain the needed HP (TQ x RPM/5252=HP).

[B17overhead]

I like the idea of not using inlet restrictors to restrict HP. The unintended consequence is all too often an increased operating RPM to obtain the needed HP (TQ x RPM/5252=HP).

I don't quite understand the science completely here, but have heard from several with 593's that an unexpected consequence of inlet restrictors on 2-strokes like 593 is less crankcase cooling, thus, a more difficult to cool motor.

[Daryl DeArman]

I don't quite understand the science completely here, but have heard from several with 593's that an unexpected consequence of inlet restrictors on 2-strokes like 593 is less crankcase cooling, thus, a more difficult to cool motor.

Reduced volumetric efficiency with the restrictor at higher rpms. Less A/F charge for a given rpm. That A/F charge in a 2stroke is responsible for lubrication and to some extent, cooling.

[Jnovak]

I have not yet sent my letter into the CRB system. My last letter was very similar in concept and it was turned down!
I am hoping for some additional ideas.

Any thoughts welcomed!