small turbos

[nsr Bassett]

hello guys n girls


iv been reading a build that a member has done on here a few years ago (b12turbo) ... a friend of mine has been talking about a small turbo (IHI RHB31 3T - 505) as far as iv read they seem to be okay "/ has any body had any experience with these

ino they can only with stand 14 psi boost , THEY SAY !!! they can handle up to 125 bhp but im very unsure of this , from what hes told me they can be run on engine sizes between 200-650cc

any knowledge would be greatly received
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Nsr125 jc20..was 28Bhp but now seized :/
Mc3
Suzuki marauder 125 Daily ride

[P.addy]

The tiny coke can sized turbo?

If you are lucky to see an additional 15hp before it explodes I'll remove ribs and chong my own wang

[Wonko The Sane]

What a turbo can withstand (your quoted 125bhp) and what it can reliably deliver without causing issues for the engine running it can often be two very different things.


For example, the turbo on a rally car is one component in an engine that is stripped down and re-built every other week.

The exact same turbo on a road car is part of an engine that might have it's oil checked every other month and perhaps an oil change every other supposed service interval.
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[dydey90]

[stinkwheel]

Last time I was very vaguely taking an interest in motorcycle turbos, the consensus seemed to be something along the lines of "Why would you want a small turbo when big turbos are so effective and readily available?"

In that you can run a big turbo at a low pressure and gain lots of power without stressing the componants.

They did make a few bikes with factory fitted, small turbos back in the 80's and while they were regarded as great fun, they were also peaky, difficult to control and fairly unreliable.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[chickenstrip]

The Kawasaki 750 turbo I had was completely reliable in something like the 12k miles I put on it. It was quoted as running 11psi boost, but if IIRC, they actually ran a little less than this. Quoted bhp was 112.

At the time, I heard various things about problems with them. The main one I recall was that if you shut it off too soon after it got really hot, the oil would crystallise in the turbo bearing and wreck it. No idea if that's the case or not. I used to think it never happened to mine cos I always had a slower run through residential streets after fast riding, giving it time to cool somewhat. Nowadays, that sounds a bit bullshit, but I really don't know.

They were not peaky, but delivered boost from about 4k rpm - the key I think was that Kawasaki got the turbo mounted quite close to the exhaust ports, which apparently helps to reduce lag?

It also ran flat-top pistons as standard, reducing the measured compression to something a little over 7:1. When I replaced the turbo, due to a snapped chain smashing the airbox casing - all the little bits of metal went straight into the turbo unit - the replacement didn't deliver any boost for a couple of miles - I'm guessing it was just a bit gummed up from old oil where it hadn't been used for a while - but it soon came back on line; thing was gutless during those few miles

I had absolutely no problems running that bike just like anything else one might have owned at the time.

[kramdra]

Turbos get very hot. The exhaust side can be 800c+. What do you think happens when oil gets to 800c? the hydrogen buggers off and leaves a thick carbon, which blocks the oil way. Its common for turbo cars to be fitted with timers to keep engine running a few minutes.


Id like to ride one, but I imagine hitting boost whilst leant over on a corner could upset things a little.

[chickenstrip]

[MarJay]

I read an article in Performance Bikes a few years back which basically said that small turbos were completely pointless on bikes.

Bikes are peaky anyway, so the small amount of peakiness you're going to add is hardly going to affect the riding experience. Lag isn't really too much of an issue because bikes are so light that a low compression engine is still going to perform reasonably well at low revs. All turbocharging seems to do is to add a monster top end to an already fairly quick bike. This assumes of course that you're using a large turbo.

If you have a small turbo on the other hand the midrange would be fat but you'll run out of puff at the top end, and the power delivery will be scary. Personally I see no point in turbocharging a bike until you've already got the fastest bike around and you want it to go faster. Turbocharging a ZX12R, Hayabusa, Blackbird or ZZ-R1400 makes perfect sense. Turbocharging an R6 or CG125 does not.
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Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[notbike]

pls put a turbo on my bike

[Kickstart]

[smithyithy]

Bigger turbo running at lower pressure. Less stressed, so less wear and heat.. and more boost in the upper rev range where bike engines want to be.

If you want more low down - supercharger.

[Pete.]

True story from my dad years ago:
My old man worked at a Ford dealership doing quality control (test driving after repairs etc) back when the RS Turbo was a new model. This customer kept complaining that his new car was boiling over after he parked up and the car went back in several times but they could find no fault. In the end my dad had to go to his house so it could be demonstrated.
The guy lived right by the A2. He would set off at a scorching pace and thrash the motor on the dual carriageway. He went up a couple of junctions and came back flat out, screeched into his driveway and they got out. Sure enough after a short while the motor boiled over.
My old man went back to the workshop and suggested to his manager that they hook the fan to a permanent live rather than the switched live it was on. They did that and the boiling-over problem was cured. Next month in the internal newsletter there was a congratulations to the branch manager for winning a good ideas award (cash prize) for curing a fault on the new car - he had put my dad's idea forward as his own and got a tidy reward for it.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[The Shaggy D.A.]

Does the manager still have his kneecaps?
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[skatefreak]

I'm up for having a stab at this on a cbr600 f3 but will be going for a reasonably sized turbo, blow through with pressurised float bowls etc.

TBH, the bike is a commuter at the moment, could do with a little work to get it running stock sweet before modding it (balance carbs, valve clearance etc) however want to try get an inter cooler, oil cooler and all the gubbins in there as well

Its more about tinkering/learning and the pleasure in getting it all together/working.

I cant say I push the bike to the limits commuting etc and I could get a bigger bike but a turbo would be cooler

It can improve fuel efficiency if you don't kane it about everywhere (on top of the 50MPG I seem to get everywhere!).

Need to have a good look through the CHR!S's build.

Will start my own thread if/when I get round to it.

Am listening with interest

-Jvr

[chickenstrip]

I'm a bit out of touch now, but when I was more interested in these things, it seemed to me that turbo-ing a non-turbo bike was a very expensive thing to do. So if I were to do it, I think I'd be looking to build a real show-stealer of a bike to make it (more) worthwhile. But remembering the costs of doing a proper job back in the late 80s , I couldn't see me ever wanting to go down that road now.

[stevo as b4]

You'd definitely need to do a lot of research and reading up on it first, and have very clear goals, expectations and a healthy budget you won't mind doubling to get it finished.

I don't see it being impossible to add forced induction to a pretty much bone stock engine, but there'd be a lot of compromises and limitations, when you would have to spend a fair bit of what doing a proper turbo/supercharger specific motor build would cost.

Also ideas and technology has changed a lot since the 80's now. Turbochargers and superchargers have been developed to be far more efficient, less laggy and more reliable too. For a lot of applications low compression builds are not seen as the way forward anymore, as people are going high compression/high efficiency with better matched components and a lot more advanced electronics/control.

[Wafer_Thin_Ham]

[Aff]

I wouldn't say turbo timers are common on stock cars, in fact I cant think of a car that came with one stock (in all markets)?

What I have seen fairly often is an auxiliary coolant pump that runs for a while after the engine shuts down.
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Current Bikes:Honda 929RR Fireblade, Honda CD200 Benly (Project), Stomp Z2 140
Electric Bike Project

[Wafer_Thin_Ham]

[kramdra]

[Wafer_Thin_Ham]