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Re: [ST] Supercharge vs Turbo



Don't forget the GPZ750 Turbo, which was very popular in the 80s, 
despite the turbo breaking down every 2,000 miles or so.  I saw one pull 
away from the lights near college once, and it was quite an experience. 
  A kind of grumbly tug from the bottom of the rev range, then a 
2-stroke-like scream as the turbo pushed it faster than ANYTHING I had 
seen at that age.

Power-valve two-strokes are very much the same thing.  Powering on in a 
corner is always slightly risky feeling.  My Yamaha 250 jumped from 
12bhp at 7,000rpm to 40bhp at 7,500rpm.  At least you don't have engine 
braking so much, so snapping the throttle shut in a panic (which you do 
when you're 19 no matter what you know about riding!) isn't quite so 
deadly or flippy.

I don't see the point of turbos on a bike at all, unless you just want 
gallons of power.  The best thing about the triple is how easy it is to 
ride in any circumstances, and I rarely think about it.  To have an 
engine with any irritation factor like lag would put me off completely.

Oh and I'm sure that the back-pressure will create some kind of effect. 
  The upward motion of the piston on the exhaust stroke will be more 
difficult which equals power loss.  It might not be a lot, but it will 
definitely be there, even in the lightest/easiest to spin-up turbo system.

Enjoy your weekend everyone!

Andrew

Matthew Heyer wrote:
> What would scare me is getting on the throttle out of a corner while leaned..... and the boost building...... and then kicking in some extra power....breaking the rear wheel of traction.....maybe you have to close the throttle....maybe then you high-side.....ugh...
>  
> Doesn't sound great for a motorcycle to me.  Maybe a drag bike, but the dynamics in play while actually riding the bike on the road would make me not want this on my motorcycle.  
>  
> As some food for thought, if this were actually viable, don't you think the major manufacturers would have implemented a bike or two with this?  Yet NOBODY does on a bike......hmmmm...
>  
> Matt Heyer
> 
> ----- Original Message ----
> From: Chris Harwood <Chris@xxxxxxxxxxxxxxxxxx>
> To: ST@xxxxxxxxxxxxxx
> Sent: Saturday, February 04, 2006 7:57:13 AM
> Subject: Re: [ST] Supercharge vs Turbo
> 
> 
> Sorry I can't accept the sweeping statement that a turbo won't create
> added back-pressure.  It might not when compared to a poorly-designed
> silencer/muffler system.  Simple gas dynamics mean that if the device is
> compressing the inlet then is must be putting back-pressure on the
> exhaust.  It is imperative that a free-flow muffler is then used so that
> the maximum pressure drop appears across the drive turbine.
> 
> My point is that superchargers AND turbochargers have overheads besides
> the power to drive them.
> 
> I think the important point for bikes is that getting that drive in the
> first place is much simpler for a turbo.  The linearity of a
> supercharger makes for a smoother power delivery which is more critical
> for a bike than a car in my view.
> 
> Just my 0.04GBP
> Chris Harwood
> 00 RS
> 
> Chris Harwood
> **************************
> Broadcast Computer Systems Ltd
> PROVIDING CUSTOM SOLUTIONS
> **************************
> T: (+44) 020 8559 0001
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> W: www.BroadcastCSL.co.uk
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> Forest Edge, Buckhurst Hill, Essex IG9 5AE
> 
>>>> buellrydr1@xxxxxxx 04/02/2006 05:39:38 >>>
> Properly sized turbo has no added back pressure,turbo is sized
> according to 
> intended use,street,drag racing,ralley,etc.So a good turbo system
> matched to 
> your engine use,compression,etc. will work seamlessly.Look at the 
> Mitsuibishi Eclipse,Rallye,Subaru WRX's etc.The added heat comes from 
> compressing the incoming charge and is overcome with
> intercoolers/charge 
> coolers.Jim.
> 
> 
>> What about back-pressure in the exhaust?  Particularly when
> spinning-up.
>>  Turbos must make it more difficult to clear the cylinder for the
> next
>> charge.
>>
>> Add Jaguar (Ford) to the supercharger camp.
>>
>> Chris Harwood
>> 00 RS
>>
>>>>> robertr@xxxxxxxxxxxxxxxx 03/02/2006 00:58:04 >>>
>> This is always a contentious one.
>>
>> Supercharge:
>> Almost instant response
>> Usually heavier then turbo
>> Usually requires case mods to get a drive to the pulley
>> Sucks horsepower so the first bit of boost is wasted fighting
>> mechanical
>> losses, varies depending if Rootes or vane type
>> Can put undesirable side load on case bearings not designed for the
>> extra
>> pulley hanging off the end.
>>
>> Turbo,
>> Very little wasted boost
>> Exhaust plumbing
>> Lag
>> Risk of overboost without a waste gate
>> Can have problems with shutting down if you don't let it spin down
>> before
>> turning off the engine.
>> Modern turbos minimise the lag problem.
>>
>> If you look at cars, Saab, Audi and others go with Turbo, Mercedes,
> GM
>> others go with Mechanical (though GM have also used turbo), so it
> comes
>> down
>> to the Mfr in-house technical and marketing strategies. Fuel
> dragsters
>> use
>> mechanical, Nissan and Ford used turbo in their group 'c' sedans that
>> were
>> almost unbeatable.
>>
>> Confused?
>>
>> Cheers
>> R
>>
>> <<
> 
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