Why has no one built an MX bike with a turbo?

Arlen Lehman at LED Performance(used to be LRD) in Gresham Oregon has turbo kits for dune quads I am sure he could do a bike if asked. His motors are works of art...........

I don't think the OP is asking for more power as much as he is lighter and easier to handle bike. If you can get the same power from a 150 or 200 cc bike with a turbo as you get from a 450, that might make it lighter and easier to handle but not forfeit the power.

I'm definitely not a tech guru but is there not a way to have the turbo constantly running rather than kicking in at a specific rpm? That might eliminate the turbo lag.

I was waiting for somebody to think outside the box. Smaller motor and more reliable parts(SS valves, less agressive cam profiles) could produce good power with less maintenance problems than the current bikes.

I'm not an engineer, but I believe a supercharger would work without the lag as it's run mechanically from the motor instead of driven by the exhaust.

Turbo Reif?

well done

It would probably be unrideable, as the turbo would spool up, deliver an enormous hit of power each and everytime the wheel left the ground over bumps, and then when the wheel lands, the added load on the drivetrain would cause additional issues. And there would also be issue with a hitting a pop off valve that would control a maximum boost pressure.

Most turbo cars seem to be more drivaeable with twin turbos.

Don't forget that F-1 at one time had 1200 lb/ 1200 HP cars with only 1.5 litre engines, and you had to hear one on a tight street course to understand how hard they were to drive, when dealing with bumps, turbo lag, and the fact that when they hit a bump, the revs rose quickly, the turbo spooled up, they hit the pop off valve, and all the pressure was released.

But I believe F-1 is returning to turbo engines with the 2014 season.

No need for a turbo. We just need 3 more cylinders.

The blowhard two-stroke fans complain enough about the cost of 4-strokes even though everywhere has 2 stroke classes and nobody is forcing them to ride a 4-stroke. Can you imagine how those people would blowup on this board if they did something like that?

All 4 Japanese mfg's made turbo bikes.
The CX Honda's were originally 500cc horizontal V-twins, then moved up to a CX650T. Typical Honda, it was a technological leader. The other 3 mfg's used inline 4's.
Yamaha built the Seca 650 Turbo with pressurized carbs; the others were Fi.
Suzuki introduced the XN85B, the best handling and rarest bike of the bunch.
Kawasaki's 750 turbo would easily lay waste to the other 3 in any sort of acceleration test. At one time it was the quickest production bike available.

Today you can get around a lot of the problems that are discussed. The biggest one is they are not legal.

You don't need to turbo charge a 450, but a 125 would work well and make the power of a 300 or so easily. As far as the lag, valving is an easy fix, along with proper crank weight. The power could be explosive, but it could also be smooth but I would guess the first - much like two stroke with a light switch power band.

The biggest issue with turbos, they aren't real dirt friendly and lets face it, we ride in the thick of it. The air needs to be filtered, the bearings and encasement needs cooling and if you think a MX thumper is expensive to repair after a piece of dirt gets sucked through the airbox, replacing turbos - I cant imagine a rebuild, would make the majority of the users here freak the freak out.

Then there's the OTD price tag. Our sport needs more high priced bikes because the prices today aren't hurting the market at all are they?

I think the problem would definitely be the transient response. Turbo's are designed for a set point and then certain characteristics are designed in to widen the map, that is, to increase the RPM range for which they are useful. With MX bikes the rev range is too large compared to passenger cars to not get lag. You could make it incredibly rideable but sacrifice your top end, or make it incredibly peaky. So yeah, maybe it would make a 4 stroke ride like a 2 stroke. I haven't looked in to any turbo 2 strokes in the past, but i imagine that it wouldn't work great, due to the fact that you need to put it in the expansion chamber without interfering with the wave propagation. Unless you stick it before the muffler in which case you're gonna end up with a lot of piping.

With emission standards coming in, the world is shifting towards downsizing engines and turbocharging to reduce fuel and emissions for the same power. I would imagine it would be the same for bikes if it happened, basically make a 250 perform like a 450 as opposed to chucking one on a 450.

At uni a had the pleasure of racing an open wheeler with a supercharged R6 and that is by far the most unreal thing I've ever been in. We raced against a turbocharged CBR600 and while that had significantly more top end, because of all the lag it was almost undriveable, it couldn't corner and we smoked it in acceleration too, the straights just weren't long enough for it to be useful.

For what it's worth, I am an engineer for the largest turbocharger company in the world. Although I have only been there a few months and am working on some different projects, so my knowledge is far from complete on the subject.