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Discussion Starter #1
alright guys i know the turbo subject has been beat to death, but i just wanted your input on would it be worth it? so i recently aquired a small turbo that works for free, and i have been doing alot of help of a local custom chopper builder that the body shop that i work for does alot of the paint work for him, well i showed him some of the pics of the honda in progress and he imidatly fell in love with the idea of it, well ne way we got on the topic on how i thought it would be kinda cool to put the turbo that was sitting ontop of my tool box on the bike, and he told me that all i had to do is supply all the metal and pipe and he would help me do all of the pipe bending and tig welding on all the exhaust, intake, and mounting if i wanted him too. so u guys think it would be worth it on my 77 cb 750 four K?

the lil guy
 

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worth is in the fun factor?.....i think so

There is the right way, the wrong way and the british way to do anything!
 

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thanks, i was also thinking it would be pretty fun, and with a little help from that guy i think i would be able to keep the cost relativaly low especialy because i have all of the metal and the turbo already, and the only thing that would realy set me back would be just all of the odds and ends of getting the turbo hooked up to the bike (oil lines, ect.)

the lil guy
 

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you will have to get oil to and from the turbo.

are you going to run the turbo as a blow through or a pull through?

There is the right way, the wrong way and the british way to do anything!
 

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be sure to run the oil supply to the turbo thru a line restrictor or you will blow the seals out pretty quickly.
do it draw thru or else you will need a fuel pump and tuning the carbs is going to suck.
external or internal wastegate on that turbo?

'72 cb750
'75 cb750
'76cb750
'82 cx500 (but mine is cool, i swear. Why don't you believe me?)
 

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+1 on the line restrictor - you can modify one of those oil cooler kits to feed the turbo (and even keep the oil cooler).

+1 on the draw through, although the old mr turbo kits were blow through on the stock carbs.

You are probably going to need to upgrade the ignition to something like a dyna 2000 so you can retard the timing when the boost comes on or you could end up detonating.
 

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Discussion Starter #8
awsome, so i am a bit confsed when u say pull through turbo, do you mean have the exhaust spinning the turbine? and sucking air in that way? cuz i thought thats basicaly how a turbo was designed to work, or r u guys talking about something compleatly different?

the lil guy
 

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blow through and draw through refers to the carb setup.

Draw through means that the carb is directly mounted to the turbo intake and outside pressurization. The turbo draws the air/fuel mix into the turbine and then pressurizes it.

blow through means that the carbs are pressurized, that the turbo draws air directly from outside, pressurizes it, and then pushes it into the carbs.

If you look at old car supercharger setups, roots blowers are typically draw through and turbos/centrifugal superchargers are blow through. Personally Your carb will last longer as a draw through and you are likely to get a more even and better atomized fuel charge, with a blow through you run the risk of "juicing" the carb where the pressure wears out every seal, hangs needles, and pushed fuel and air out anyway it can.

a lot of the old turbo setups are are blow through, but those old setups were only good for around 6-8 psi, hardly a staggering amount of boost. With modern turbos, electronic ignition, and a proper carb (those huge honkin mukuni VMs some harley sportsters came with come to mind) you could probably push about 10psi which is enough for you to see a...ahem...noticeable difference.

Ideally you would want fuel injection and a single throttle body with a mass air sensor, but there is no readily available kit for that for the cb750. With FI, it would be feasible to run as much as 25psi on the street (with a knock sensor of course) which would make your motor basically a grenade with the pin pulled (weak stock rods, carillo rods are $1g a set). If you want to build a grenade - nitrous is cheaper and more fun.
 

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A draw through turbo needs to have special sealed bearings on the intake impeller to keep the fuel/air mixture from getting pushed into the engine oil.
There's more to turbocharging a bike than slappin' a turbo on and expecting it run right. Things like impellers, A/R ratios compressor maps and others.
Blow though systems work better and are easier to get the jetting correct. Blow throughs also need to have the complete carb (float bowls,etc) pressureized and need to have a rising rate fuel pump(ie- when your turbo has 10 psi of pressure your fuel needs to have more pressure to overcome the turbo's pressure wanting to push the fuel back into the tank- and they usually have a fuel tank return line to bleed off fuel pressure when the turbo is spooled down). Blow throughs usually have the turbo mounted in the front of the engine and need a special manifold to mount to the stock carbs.
Draw through systems are usually easier to mount, but the jetting is harder to get correct. Most people use a Mikuni HSR 42 for the draw through systems.
I reccomend this book for people wanting to put turbos on their bikes. It goes into detail about the turbos and the draw through and blow through systems and all aspects of turbocharging motorcycles(except for the jetting of carbs).
DG

http://www.themotorbookstore.com/motusuandnio.html
 
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