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I just bought an A-Mod car with a 600cc motorcyle engine. I have run time trials and autocrosses in a formula ford with the BBR shark and am in awe at how fast that car is. I have been the reading the modified forums and have seen discussion about the 2-cycle vs. 4-cycle engines with weight being the main factor which is obviously a very important design factor with A-mod racecars.

How much does a built 3-cylinder 2-stroke snowmobile motor weigh? At this point, I am planning to put a 1000cc plus turbocharged motorcycle engine in the A-mod car but want to investigate other options before I spend money. I am still in school and heavily involved in Baja SAE so work on the A-mod car will not start until I graduate and start working. I want to see some discussion about high powered snowmobile motors vs. high HP motorcycle engine. Let me know what you think. Thanks.

 Dave

 

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University of Virginia
Class of 2008
1982 Crossle 50F Formula Ford
A-mod Suzuki Katana 600cc Project

Dave

There is really two discussions here. Engines, two vs. four strokes and transmissions, geared trans vs. CVT. I run a four stroke, so here is some pitfalls with those. I do not think with a four stroke you can get to below minimum weight. Even thought the four strokes are very light, they weight more than the two stroke. Also, there is more equipment too package to support the four stroke (more weight). One of the other problems with the four stroke is the oil supply to the engine. These engines are not made to run around a corner flat. Installed in a motorcycle the engines leans with the bike thru the turn so the oil pump and oil pickup are designed accordingly. But, installed in a car G forces will move the oil to the side and the engine can starve for oil. Also, there is the same issue with fuel in the carburetor bowls. We are discussing A mod so the G forces can get pretty big. Four strokes are harder to mount into the frame, but the four stoke cases can carry some of the flexing load.  I am running out of time, so I will try to add more to the post when I get some time.

Stanley

Joe wrote on VCMC:  http://www.vcmc.ca/forum/showthread.php?p=38211

Internet claim of 550hp with a 4 stroke:

Price on the kits start out at $5,000,00 US ($1,000.00 down payment keeps all orders serious)> these kits are ready for immediate shipment in mid December. Lake Race versions are also available at $5700.00 and can be tuned to the 360 + HP range with mild engine mods. This is the same type of package used by the Proline / Simon’s CPR / Knapp Attack racing team that divested the heavy mod and open mod classes at the HAYDAYS grass drags setting a new track record on the RX-1 based engines. For you RX-1 and VECTOR lovers, Jeff also has 195 HP trail turbo kits, which can easily be turned up to 280 hp as well. And now up to 550+ hp on race turbo kits, the same CPR kit that currently holds the world record run 0f 7.97 sec E.T. at 170 MPH in a ¼ mile.

I have a feeling a modified 2 stroke twin makes more than enough power and is the lightest/simplest.

Marlin

Dave,

 Bowland's Shark is absolutely amazing! I normally drive Tommy Saunders' Dragon, but George Bowland offered me a drive in his car at the 2007 Nats, of course I accepted. What a cool car. For B/Mod, Tommy's car is as good. We switched to the Yamaha R1 motor in 2006. This motor has more power than we can use normally, especially at a site like Topeka. My point is that you may consider an inexpensive solution to start with. The Yamaha will live in what we do, many others will not. We have two motors, an 05 and an 06, both bought on Ebay for less than $2000 each. The '06 motor has less than 100 miles on it. These engines are also fuel injected. Run about one extra quart of oil in the sump seems to work fine, trust me, we drive that car hard, so we put all this this to the test. George's car has way more than needed power for autocrossing on asphalt, I was only able to go full throttle two or three times per run at Topeka, it has that much power. All week long he was telling me that I need to drive the car on concrete, it is more fun.

 Stuart Lumpkin

#99 B/Mod Dragon SR-1

When I went thru the process to deicide what power plant I would use, I came to the conclusion that the CVT was a must. But I was mixed about the 2 vs. 4 stoke thing. I did go with the RX1 with a turbo, and this RX1 has big HP numbers. Like Stuart posted, this car also has way more than needed power for auto crossing on asphalt. When sport bikes became popular, buyers wanted to purchase the fastest bike, a engineering war was started with the manufactures. Each year engines have gained in HP and lost some weight. Then because of environmental reasons they started to put the 4 strokes into snowmobiles. In spite of there additional weight these 4 stroke snowmobiles have just about dominated the 2 strokes in all snowmobiles racing venues. In Amod there is a lot more to the car then the motor, it is a complete package.  The top Amod’s all run the 2 stoke, but they have had years of brilliant development and are driven by very experience and excellent drivers. How many 4 stroke Amod's have gone thru the development the top 2 strokes Amod cars have. If you look at last years Nationals times you will see the FSAE top car was just a couple of seconds off from the top Amod and that is with 600cc’s 4 stroke, a restrictor in place, a lot less wing, and a gearbox. (I know that there are a lot of other factors, but it does tell part of the story).Can a 4 stroke Amod beat a 2 stroke, sure I have done that. Can a well developed 4 stroke beat a well developed 2 stroke, the verdict is still out. I feel that the needed HP power can be obtained with both the 2 or 4 stoke power plants. The choice could really come down to the packaging, the sound, the cost, the weight, availability, personal likes or dislikes, or what challenge you want to take on.

Stanley

I wanted to address the oiling issue a bit more with a couple of questions. If you look at the roadracing ranks in C/D SR's you find a pretty even split in the wet sump vs. dry sump cars. As far as I know all the wet sump guys use a specially baffled pan and a higher oil level. My R1 for instance uses a baffled pan and I run the oil to the top of the sight glass when it is warm and idling. Never seen the pressure drop with this set up. Any dry sump users in Solo?

Does anyone know if the RX-1 (essentially an R1 with a CVT set up for a sled) have a substantially different pan than the R1 bike? Anyone use that pan as is for solo? Will it fit a bike R1 engine?

Also, for Amod why aren't there more 1300 cc plus Hayabusa or ZX-14 based powertrains? I would imagine that while a bit heavier, the strength and power potential are much better than a liter bike engine. Liter bike parts are built as light as possible due to AMA and WSB competition, limiting the durability somewhat. That is not the case with a Hayabusa or others.

While the CVT and two stroke are seen in Solo, there is not a single national contending two stroke (save for maybe one of the Kohler powered cars) in SCCA club racing. While the CVT may not be an advantage, the two stoke power and weight should be.
 

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Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY

The CVT has an efficiency of 75% to 90% depending on construction and what "ratio" it is in.

There aren't many big bike engined cars because there aren't many purpose built A-mod cars.  Goodale's Dragon has ZX14 power.  Brian Pimm's converted F500 has 'Busa power.

Aren't DSR 2 strokes limited to 800cc?  Didn't Aaen build a 800cc V4 for DSR? The CVT efficiency might negate the advantages.

Marlin

The RX1 and the R1 are basically the same engine design. But not really the same, first of all the bottom end of the two are totally different. The RX1 has one gear reduction drive off the main crankcase, a complete dry sump system, and a DC Generator, and if my memory still works with no water or oil, with starter installed, but not the carbs or clutch installed, it's about 66 lbs. There are many other differences, for example the intake ports are spaced different that the R1. So far I have not found one major R1 part that will bolt to the RX1.

Stanley

Stanley,

You mention carbs, I thought all the RX's and just about all bike engines (liter bike and above) after 2003 were fuel injected. That typically eliminates all of the carb slosh issues.

Later model sled based two strokes are also injected right? Or only some of them? 

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Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY

The RX1 uses carbs, the newer Apex uses the fuel injection. I am pretty sure they put the carbs on for the power, all of the RX1’s I have seen or heard about have the carbs. OK, sure you might be able to produce the same kind of power with injectors, but many of injected motorcycle engines have been converted to a nice set of flat slides. I use a different system,  the intake cylinders draw directly from a small plenum box that is pressurized directly with a draw thru turbo using a big Mikuni Smoothbore. There is no turbo lag with this system.

I really don’t know much about 2 strokes. I really think that as sound limits are placed on us at events, the 4 strokes will be able meet limits. 2 strokes just might not meet some new nose limit without big reduction of power.

 

Stanley

More on the oiling issue, I have blown a engine because of oiling. In C/D SR’s classes there has been more than one engine let go because of oiling. The dry sump cars have had some issues to, not sure why, but I think in some of these failures are because to much of the stress loads where being supported by the engine cases. I also think that in Solo we are not in steady state turn for as long as a road race cars and our runs are much shorter, so the problem is reduced. We also do not have as much of a oil temp. problem as the road race cars.  There are some things that can be done, more oil in the sump has been mentioned (works in some cases), specially baffled pan (helps), accusump (works good, but extra weight), and the dry sump (best, but more weight than the accusump). The dry sumps are very expense, if fact you can normally have spare engines for less money than installing a dry sump.

Stanley

I lost a Yamaha V-Max car engine due to lack of oil. I added an Accusump and had no more problems. Accusump isn't as expensive as a dry sump, and good enough for Autocross (most of the time).

Del Long   D/E Mod

Also, for Amod why aren't there more 1300 cc plus Hayabusa or ZX-14 based powertrains? I would imagine that while a bit heavier, the strength and power potential are much better than a liter bike engine. Liter bike parts are built as light as possible due to AMA and WSB competition, limiting the durability somewhat. That is not the case with a Hayabusa or others.

Joe,

In B/Mod, Tommy and I looked at the Hayabusa, we would have to add some weight, but quite a bit more power. I think it was 2004, we went to the Run-Offs at Mid Ohio, every one of the Hayabusa's blew up, the Yamaha's seemed to be way more reliable.

Stuart

How much does a 2 stroke triple or twin weigh?

Stuart,

There's a whole cottage industry in Europe building Lotus Seven clones with Hayabusa power. Also most Radical sports racers come with either stock or enlarged Hayabusa engines. They can be made to live in a SR chassis. I think it has a lot to do with the proper oiling set up as well as the mounting in the chassis to control flex. While it was more attractive last year with the CSR weight loophole in the Solo rules, it is less attractive today, but still a viable option in my opinion. You can make a lot of horsepower with a Hayabusa and not even be close to stressing the engine. Also, the clutches and transmissions are stronger than the literbikes. I ride a modded Hayabusa as a street bike and would love to move that engine into the Legrand! I'm not sure it would be a help at HPT though from the sounds of things.

If I'm not mistaken, there is a proposal out to determine interest in limiting sound at National tour and Divisional Solo events. If this type of thing takes hold, I would imagine that it would not be a good thing for two stroke machines. My R1 engined car is able to easily meet low 90's dB regs at several local events using an after market sport bike muffler.
 

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Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY

Has anyone ever thought about divorcing a R1 engine form the tranny with a custom block. Then mounting it to CVT trans.

Crank speed is to high for the CVT. Thats why the RX-1 has the output shaft geared down.

 

What is a typical RPM limit for a big two stroke triple or twin?

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Joe Gonzalez
1979 Legrand DSR- B Mod
Gilbertsville, NY

bpimm:

Crank speed is to high for the CVT. Thats why the RX-1 has the output shaft geared down.

 

I think, and I could be wrong that the slower crank speed makes tuning the CVT clutch easier. Heavier weights, more variation in ramp angles, all contribute to more flexability of engagement RPM.

I don't own a snowmobile, never adjusted a CVT, and don't remember staying in a Holiday Inn Express, but I did look into using a CVT on a type 1 VW engine for D Mod. That was before CVT's were disallowed.

Del Long, D/E Mod

Big twins ~7500rpm

Triples- up tp 9500rpm

Typical CVT starts at about 3:1 reduction and can overdrive up to 1:.75 (but not efficiently).  

I think these numbers are right.     -Marlin