HORSE POWER VERSES EFFICIENCY

[TWIN TURBO]

I know most everyone, if asked, would say yes to more Horse Power as it seems that the belief is the more HP the faster you go. I’m here to go just slightly against the grain. No doubt, it requires HP to go fast but just how much? What about using what we all have more efficiently. I have seen firsthand that not everyone will go faster by adding just HP. Just the opposite, I have seen cases where reducing HP, the customer did better. I believe this happens mainly due to the lack of ability to transmit this power efficiently. I’m guilty, for years our shop has persued more power, but this past September at Haydays Grass Drags I finally realized we have other issues to address. I have a very high end data collection system on our race sleds that can collect information far beyond just boost pressure and water temperature. What we found is at increased power levels, transmitting that power becomes much more difficult. I don’t what to give specific HP numbers here as it very’s from one to another as dyno’s and testing procedure’s vary thus different results. For more on this go to my web site and under the Information Tab, I have tried to explain this. What I have been concentrating on is Belt and clutch efficiently. I think if you talk to 10 different successful racers and ask them to share their clutch setups you will walk away with 10 different setups. This leads me to believe that what I was looking for is not simply what helix or what clutch weight I need to run. That’s what leads me to clutch speed. Many of us 4 stroke turbo Yamaha guys are spinning the engines up much higher than the stock 10250 or 10500 RPM. What happens to clutch speed when you spin the engine 12000 to 13000 RPM? Let me give you a couple of examples. A RX1 at 10250, the clutch will spin 8600 RPM. Now spin the engine 12000 and clutch speed goes to 10100 RPM. A Apex has a slightly different reduction ratio. Yamaha knew that efficiency would drop when they decided to spin the Apex engine 10500. They adjusted the reduction ratio so an Apex at 10500 RPM the clutch spins 8500 approximately. Now spin an Apex 12000RPM and clutch speed goes to 9750 RPM. In both cases the belt speed goes out of site, especially with the relatively short belts Yamaha uses. I went back to some of my old clutch tuning manuals by Aaen and Cutler performance , Some of you older guys may remember them, And read about how inefficient this belt speed can be to say nothing about trying to grab hold of the belt when the clutch is spinning that fast at engagement. IT takes less than ½ second for an engine to go from 5000 RPM engagement to 12000 RPM clutched RPM. Did you ever wonder why your clutches are hot?
This is what I’m doing about it. I should have, by the end of the December, a limited number of Gear Reduction Sets. These are precision made of billet steel, heat treated and ground to the highest standards required by their environment. It will require only a slight modification to the gear cover to allow for larger diameter driven gear. They will be available for Apex and RX1 in 2 different ratios. A RX1 or Apex at 12000 now will spin the clutch 8330 RPM with my gear set with most reduction and 8500 with the 2nd ratio. Think about this, a RX1 will drop from 10100 to 8330; an Apex will drop from 9750 to the same 8330 RPM right back to where Yamaha knows well, belt efficiency is far better. Now we can add the weight back in the clutch we had to remove to let the engine RPM go up there. Obviously, the more weight the more force to apply to grabbing the belt. Another advantage of gear reduction is Torque multiplication. By reducing clutch speed with gear reduction, you will multiply the torque. It’s like putting a 4.88:1 gear in your car’s rear end. The wheels see a torque multiplication.
I welcome responses to this. I believe this is a topic that can help all levels of racing

 

[HYFLYR]

Very interesting, i like where you are headed with this and have wondered the same thing before.

 

[gunnerthesnowman]

Very interesting , i wonder if anyone else is doing this ?

 

[TWIN TURBO]

I think when you look into it and find out what it costs to do this, you better have a strong HEART. I truly believe this is important and I've put some resources to the project. These are High precision gears and very difficult to make.

 

[zross1]

Good info.

 

[gunnerthesnowman]

I think when you look into it and find out what it costs to do this, you better have a strong HEART. I truly believe this is important and I've put some resources to the project. These are High precision gears and very difficult to make.

Did not mean that it could be done cheaper , Your cost seems good ,just wondering if someone else (race team )may already be doing this!

 

[kinger]

So your regearing the clutch so you can spin the engine at a higher RPM? What happens to the engine at 12,000 is this for a race sled or trail/mtn use?

 

[gunnerthesnowman]

So your regearing the clutch so you can spin the engine at a higher RPM? What happens to the engine at 12,000 is this for a race sled or trail/mtn use?

I think the R1 street bike engine REVs like 16000rmps to make the power it does , in sleds the revs are limited by the clutch RMPs ,

 

[aja636]

John from PROLINE has the gear reduction in his RX1. I talked to him about this last winter. There was a guy planning on doing this and Posted up on here about it. This gear reduction make perfect sense for race sleds.
Not 100% sold on the cost and work needed for the boosted trail sleds.
Not sure for mountain guys, aren't they looking for track speed???

 

[TWIN TURBO]

I've done some Dyno work with that one and only set of gears, at least that I'm aware of. I was waiting for the guy who made them for John to make more but couldn't get him to do it. I guess the investment was too high, so I decided to do it.
There may be others doing it but the cost is very high to do one or two sets. It's not just manufacturing costs, you also have engineering and tooling costs to deal with. Those crank gears have a internal spline in a blind hole. Too make it worst RX1 and Apex are different. Believe me when I tell you it was painful.

 

[aja636]

I bet, I talked to the guy last year, and he worked for a company that had the means to make the gears. And he didn't have the funds to go and make a couple sets. He was trying to get guys to give some money up front to cover costs, but I don't see dozens and dozens of sets being made or sold. These gears will benefit a small percent of the small percent of boosted sleds. The drag races will love'em!!

 

[TWIN TURBO]

AJ,
Your not thinking hard enough. I wouldn't go as far as to say everyone can benefit from them, but I believe more than what your saying for sure. Anyway, there won't be enough of them to find out.

 

[aja636]

I didn't mean it that way Greg. Just saying that your normal stage 1 boosted trail guy wouldn't consider these gear sets, they aren't pushing the power or RPMs to need or gain the benefits.
But every boosted yamaha sled on the lake, grass, asphalt, Ice race tracks should be looking into them.

I can't speak for mountain guys, I have never seen the big mountains so I don't have an opinion on that.

When I first seen the info about these last year I was trying to get my hands on a set for my sled. I know what the gains would be!!!

 

[TWIN TURBO]

AJ,
I didn't take offence to your comment, just want everyone to think about the efficiency thing. I get tired of hearing "I NEED MORE POWER"
I have wanted a set of these since the day John got to try the Prototype set on his track dyno. I wanted to get his engine back on my dyno after that to play with it but he had to give them back for evaluation.

 

[aja636]

AJ,
I didn't take offence to your comment, just want everyone to think about the efficiency thing. I get tired of hearing "I NEED MORE POWER"
I have wanted a set of these since the day John got to try the Prototype set on his track dyno. I wanted to get his engine back on my dyno after that to play with it but he had to give them back for evaluation.

That is the right phrase, Just most people forget to say "to the track" after it....