Turbos

[scumdog]

cos it isn't sexy orange, and doesn't look menacing like mine does..
I just wanna hear some whoosh..
like this, but not as much power 499bhp (~12.7mb)

I'm in contact with the TMIOA (Turbo Motocycles International Owners Association) and one member has taken his XN out to 836cc (normally 650) and his dyno reading is 118hp and 79.4ft/lb of torge, nothing to be sneezed at for a 22 year old bike eh?

[Jonty]

Dead right, a lot of the time the first bit of turbo boost is just getting the engine into thinking it's running at 11:1 comp instead of 8.5:1.
A hi-comp engine under lightish load is going to be more fuel efficient than a low-comp one under the same load i.e. will run a higher vacuum.

Interetsing post - sorry silly question scumdog, but what to the compression values mean? ie 11.1 vs 8.5.1. I realise one is a higher compression than the other but in terms of how it is calculated.

Cheers

[Ixion]

The Lancia Delta S4 had both fitted during the heady days of Group B rally cars..

I shoud'a known 'twould be Lancia !

[Ixion]

Dead right, a lot of the time the first bit of turbo boost is just getting the engine into thinking it's running at 11:1 comp instead of 8.5:1.
A hi-comp engine under lightish load is going to be more fuel efficient than a low-comp one under the same load i.e. will run a higher vacuum.

Hm, there's more than compression involved. There's things like valve and port sizes. They have more effect on consumption than comp ratio. (Low comp engines are usually good on fuel cos they also have small valves and ports).

Thing is, with a turbo you can have quite small inlet valves and ports (assuming the donk is designed for turbo from the start).

Cos the turbo can shove the mixture in through a (comparatively) small port happily enough. You've got heaps of boost pressure to force it in

Normally aspirated, all you've got to get the mixture in is the vacuum suck. So you need bigger valves (and/or lots of them) and big ports.

The big ports and valves are fuel inefficient at low revs (for lots of complicated technical reasons around air velocity and turbulence and such like). Meanwhile, the turbo, when running at low (non turbo) revs is very fuel efficient cos of those small valves and ports (May be pretty gutless at low revs mind you, until the turbo kicks in. But if you're the sort of person that runs a turbo you probably don't care about low rev performance)

[bugjuice]

I'm in contact with the TMIOA (Turbo Motocycles International Owners Association) and one member has taken his XN out to 836cc (normally 650) and his dyno reading is 118hp and 79.4ft/lb of torge, nothing to be sneezed at for a 22 year old bike eh?

most definately not!! Rebuild every few days...??


Thought the anti lag system fed the over boost from the waste gate back to the inlet of the turbo, to keep it spinning?

Lancia's rock. I want a Delta Integrale HP (the 200bhp+ version)

[ajturbo]

Why bother, look up Trademe, Ebay and buy yourself a Suzuki XN85.....

or you could offer me a small fortune for mine!!!!

i would trade it on a TL1000s..........

[scumdog]

Interetsing post - sorry silly question scumdog, but what to the compression values mean? ie 11.1 vs 8.5.1. I realise one is a higher compression than the other but in terms of how it is calculated.

Cheers

11 to 1 means the volume in each cylinder is 'squeezed' in effect into one eleventh the volume if you know what I mean i.e. when piston is at the bottom of its travel the cylinder has 11 times the volume it has when the piston is at top dead centre at the top of its travel..

A turbo 'fools' the engine into believing it is 'bigger' than it really is by cramming more air/fuel mixture into the engine than it could 'suck' into itself normally.

More air/fuel = more 'bang and energy released, that's why (all things being equal) a big engine puts out more grunt than a little engine.

Low-comp motor - not much compressing of the fuel/air mixture so less efficient burning of same i.e. a weak bang.

Hope the confusion is not too bad, maybe somebody more erudite than I can elucidate??

[Blackbird]

I used to run a Shorrock C750 vane supercharger on my drag bike and it produced huge no-lag torque from way down low. This characteristic can actually improve fuel consumption under normal road-going conditions on a car or bike. As Scumdog said, horsepower absorption is an issue and you have to match applications carefully. Physical size is a further issue. Both the vane and Rootes screw-type superchargers were also quite high maintenance through the drive train and vane bearings although the newer developments which Vifferman described may have improved this aspect.

Many years ago, there was a legendary road-going Bonneville in the UK called Ghengis Khan which was equipped with a Shorrock supercharger. Not only would it see off any other road-going vehicle, it would give most track bikes a good seeing to as well. This was presumably only on a straight line given that early Bonnies had a hinge in the frame. I should know, I owned one for a short time!

Geoff

[Lou Girardin]

Quoting peak torque figures is meaningless unless you can see the entire curve.
An engine with a lower peak torque may have an actual curve that starts sooner and is flatter than the other giving a much more flexible engine and one that'll accelerate harder in the real world. And regardless of how you do it, X amount of power requires X amount of fuel once you reach optimum volumetric and thermal efficiency.
And I'd rather hear supercharger scream than that asthmatic gasping that turbos do.

[bugjuice]

I think speedpro has some 80's 1000cc turbo thingy.. Saw it once, the turbo sit just under your left thigh, and the pipes go just a bit further out. That looked mental. Also looked like it'd handle like a boat and had similar brakes to match, but having never rode it etc, I could quite possibly be wrong.. Think it was a Kawa come to think of it, but probably wrong about that too..

[chickenfunkstar]

Dead right, a lot of the time the first bit of turbo boost is just getting the engine into thinking it's running at 11:1 comp instead of 8.5:1.
A hi-comp engine under lightish load is going to be more fuel efficient than a low-comp one under the same load i.e. will run a higher vacuum.

Is this approximatly the change in compression from when an engine is 'off boost' to when it is 'on boost'?
Is there any way to relate PSI of boost to the change in compression?

[chris]

The BMW turbo charged engine fitted to the Brabham F1 cars in the early eighties gave around 1500bhp in qualifying trim...........from a 1500cc four cylinder engine with a production car block!! 1000bhp per 1000cc aint bad.

[RiderInBlack]

Would increasing the O2 percentage, by say a bottle of pure 02 adding control amount to the carbies, increase an engine's output? Or is there to bigger risk of it causing the fuel to pre-ingnite? Could a dive bottle with air be used to increase the pressure pre-compression?

[Blackbird]

Doug,

This is what superchargers/turbochargers do by cramming in more air and fuel. Stuff like Nitrous Oxide and Nitromethane also do it. Can't remember my chemistry but I think Nitromethane liberates about 55% of its weight in O2. Extra power = extra heat and all that implies. Can't remember how many piston crowns I melted on the drag bike, not to mention splitting the crankcase!

Geoff

[Motu]

All these pros and cons go out the window with turbo diesels,they are a natural for turbo boost and it's a win/win situation all round - you don't need lower compression,you don't need more fuel,temps are cooler not higher,no strengthened parts...more power,more torque,less fuel consumption.Nearly every haulage truck,locomotive,ocean going vessel will have a turbo - it's for efficiency not power.2 stroke diesels like the Foden V12 ran twin blowers/twin turbos.