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Holy crap...that is beautiful. has anyone seen an aftermarket kit for that. maybe for a DOHC...ha i would blow the thing up on the first run.
 

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am I the only one that finds the very tightly cropped pix of this item leaving much to be desired?

reality is you can't really tell much about it and he sure doesn't commit to much in writing

at 500 bucks I'd probably not be as concerned but at 6K and that's all he shows/tells ?

don't think so
 

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and besides

belt driven (takes two belts for this one, one smooth and one syncro) centrifugal huffers ain't much pumpkin and have lots of issues
 

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it is a modified drouin unit. Nice units but old tech by todays standards. Yes they were kits back in the day, no kits now but they are not hard to make if you know how to weld and fab stuff.

They were a favorite with drag racers but finicky to tune on the street and really not good for a "stock" motor. If you wanted street forced induction a Mr Turbo or ray jay turbo unit was better. with any forced induction on a cb750 you run into the head flow restrictions before you every really see the full potential, at least the turbos had wastegates, the supercharger did not.

I've seen them sell for $2K -$3K but $6K is pretty steep. Still it is custom.
 

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I remember seeing these kits many moons ago. I agree that a turbo setup is a little slicker plus I have a problem with something like that hanging off the end of the crank. 6G's ??? - there's a sucker out there that will snap this up. One of my buddies and I were talking about using a turbo on a honda - his comment was that was too old school and that using juice (Nitro) was the only way to go. I told him I didn't want to be immortal for a few seconds and pick up engine parts off the road after the head let go. For me - someday I'd like to build a turbo honda (my buddy just happens to have a turbo unit I'm trying to talk him out of)

My 69 stock'er project is almost completed, pictures will be coming in a few days - stay tuned...
 

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bmartin,

with the technology that is out there now turbo is they way to go. Fuel Injection would also be the way to go. What wasn't around in the 1970s was variable electronic ignitions, boost controllers, and cheap FI parts that make 20 bls boost turbos viable where as the old setups would pull 6 to 8 before you started to lunch stuff. Turbos need a significant amount of timing retard at higher RPMs that just wasn't there with mechanical advance and points.

The one reason a supercharger was more popular in drag racing is it doesn't require you to pull as much timing out at higher boots levels and you can retard you stock system to enough at idle to compensate for like 10-12 lbs. A lot of drag racers used the drouins and I ahve yet to ever hear of a crank failure, and a lot of those guys ran lightened cranks. I do remember an old timer telling me about the hondamatic cranks being popular to use in the cb750 blocks for really stout big bore supercharged motors, but that involved a lot of work.
 

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I find the timing assertions bizarre.............

however, the drouin in pretty much a belt driven turbo

a centrifugal blower anyhow

it is not positive displacement and to be efficient it must be driven many times faster than crank speed

the very real problems?

bearing short life, it doesn't have adequate lubrication and the bearings run at wickedly high speeds

seldom are these setups sized correctly since to do so would require shaft speeds in excess of 100,000 rpm

so they do a much larger (less efficient for the application) and drive it slower

far from ideal

belt, really tiny pulley on the blower shaft required and the problems associated with such execution

no one way clutch to protect the belt from snapping and bearings from exploding

tell me why it needs a sprag in the blower drive ........

at best, those are half baked setups

quote:Originally posted by Geeto67

bmartin,

with the technology that is out there now turbo is they way to go. Fuel Injection would also be the way to go. What wasn't around in the 1970s was variable electronic ignitions, boost controllers, and cheap FI parts that make 20 bls boost turbos viable where as the old setups would pull 6 to 8 before you started to lunch stuff. Turbos need a significant amount of timing retard at higher RPMs that just wasn't there with mechanical advance and points.

The one reason a supercharger was more popular in drag racing is it doesn't require you to pull as much timing out at higher boots levels and you can retard you stock system to enough at idle to compensate for like 10-12 lbs. A lot of drag racers used the drouins and I ahve yet to ever hear of a crank failure, and a lot of those guys ran lightened cranks. I do remember an old timer telling me about the hondamatic cranks being popular to use in the cb750 blocks for really stout big bore supercharged motors, but that involved a lot of work.
 

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Geeto - I believe with a turbo setup you need to use lower compression pistons. Something like 7:1 instead of 9.5:1. I'm not a turbo expert but I've read about turbo powered hondas for years and they look really sweet. With a turbo honda, are you going to kick some new 600/1200 sport bikes ass - nope - but it still it would be a cool project.
 

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quote:Originally posted by HackAsaw

I find the timing assertions bizarre.............
Supercharges always run in a fixed ratio in relation to engine speed because they are driven off the engine. Turbos run in a variable relation to the engine speed because they are exhaust driven - with turbos boost is controlled by a waste gate and/or boost controller because there is no way to adjust the dive mechanism to make max boost at peak hp. Output on a turbo increases exponentially in relation to engine speed.

From my limited expirence with turbo cars, when you start pumping massive amounts of boost into an engine you have to change the entire curve of the timing and retard it a lot. In my buddy's turbo car he is pulling over 40 degrees of timing to run between 30 and 40 psi.

In the old days with carbs, mechanical advance units, it was very difficult to change the shape of the timing curve on a cb750. Anything past 8 psi was not keeping up with the turbo and you could have catastrophic failure pretty quick. With the drouins, you could play with the drive pulleys and get the charger to make 8 or 9 psi at peak rpm so you had no need for a wastegate. However most of the people running drouins were drag racers who were also running ARD Mags and those were easier to recurve to meet the supercharger's needs. You could recurve them to work with turbos but the unit was not able to pull out as much timing as necessary to work with more than about 12-15 psi boost.

one of the bigger problems with any kind of boost is detonation, and precise fuel metering and timing has made that more controllable. I think these days if you want to be serious with a turbo you have to be pushing atleast 14 psi (1 atmosphere), and the old junk just won't get you there reliably enough for use on a streetbike.
 

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quote:Originally posted by bmartin

Geeto - I believe with a turbo setup you need to use lower compression pistons. Something like 7:1 instead of 9.5:1. I'm not a turbo expert but I've read about turbo powered hondas for years and they look really sweet. With a turbo honda, are you going to kick some new 600/1200 sport bikes ass - nope - but it still it would be a cool project.
with any boosted engine you need to run lower compression. When we put the eaton roots blower on my father's Harley, we needed to drop compression to 8:1.

8:1 is about as low as you want to go with a turbo because remember at idle the engine is not getting any boost, it is basically an NA motor, unlike a supercharger where you can go to 7.5:1 and gear the pulleys to make up the difference.

on a cb750 you can get low compression pretty easy, it is just a matter of mixing K and F pistons and heads, but the problem with the stock stuff is it is all cast. Good for up to about 14 psi but not much over and you will probably have rod failure before then since the stock cast rods are weak also.

I think with a 20psi turbo honda with the right work you would most assuredly kick modern middleweight sportbike ass in a straight line. I figure 20 psi should put you right around 135hp.
 

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I still find the rhetoric bizarre

enough so that I must refrain from reading it
 

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Geet.......... I did some welding today and had fun with my human ground lead trick

is this stuff about advance specific to the cb750?
 

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Generally speaking, most turbo kits are designed to work on the stock engine with the stock compression and are more of a bolt on to the stock engine arrangement. Heres a cost comparison (Hi Po VS Turbo charged). Note the turbo uses the stock engine.

http://www.mrturbo.com/turbo_charging/charge2.html

Of course if you have put 12/1 pistons in your engine they will need to be replaced with a set of lower compression pistons. Given the same turbo/wastegate specs, lowering the compression will add turbo lag.

On my KZ 900 Turbo, the engine was left stock and the turbo was bolted on it. My Blake turbo kit had an adjustable wastegate and when drag racing, I would dial it up to 12-14 PSI and on general street riding I would use 6-9 PSI. I had a Mallory Sprint Mag on it , but it was removed as the timing was fixed (No advance or retard)and a Dyna S was installed, the Mikuni VM 38 was removed and a Mikuni HS 40 (accel pump) was added at the same time. I probably could have used more boost, but the KZ's have a pressed together crankshaft and arent ideal for Hi Performance applications (The crank should be welded together for Hi-Po Applications).
DG





 

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it is retarding timing and the conservative rule of thumb among turbo car racers is .75 degrees per PSI of boost over stock. Mos of them use a piggy back timing retard box like those made by MSD to pull degrees out as the boost climes, the other way to do it is to re-curve the distributor. This what what I have seen with car guys running 20-40 psi of boost and FI. Most of these guys started with stock honda 4 cylinders and basic turbo kits. they found that between 2 and 8 psi boost their cars were no less reliable than stock, but the moment they crossed 10 psi the cars began to suffer detonation and hole pistons and warp heads. The more timing they pulled out the less detonation they experienced. MY buddy makes over 800 dyno proven hp at the front wheels, runs on average 34 lbs of boost, and had to completely remap his ignition curve to compensate. This is on a stock honda engine block.


this is his civic on a 10 second pass (near lane):

his brother Bobby tunes most of the High Performance turbo Subarus in NY and is helping me with the turbo setup for the LSR attempt if we can get a bike. He and I talked briefly yesterday and we agreed 5 psi is about where we want to be with the turbo, that way the sucker is pulling its own weight and we will have to make few changes.

I will be the first to admit I have no idea what is going on when it comes to turbos. I have supercharged two vehicles in my life, one was a mccullugh supercharger on a jeep engine and the other a roots blower on an evo, and the turbo stuff is alien to me.
 

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ok, have a a couple boosted bikes and have fooled with both turbos and positive displacement huffers

blow thru with pressurized fuel....... boost control fuel regulators

one with not easily programmable timing and the other an advance-less magneto locked down

drag machines (bikes... not the fast and furious stuff) typically are simply set up for max boost and locked timing

turbo or blower

am working on a blower project with recirc valves in hopes of fuel mileage being improved over stock

with normal street riding rider inputs





I was trying to follow and reconcile the info and it made my head hurt sorta (but not nearly as much) like trying to read this stuff about

something as simple a dual plugging heads

check this guy out....... he seems to want to cover all the bases here and goes from one extreme to the other

ie... delimit the amount of full advance by the advance unit

make it come in faster

make it come in slower

limit the amount of advance

but he fails to realize his notions conflict despite representing them as from the burning bush

this is an extreme example and really takes some patience to get to the end

http://bmwmotorcycletech.info/dualplugging.htm

the content of that particular page is about 70% wrong

and about 90% indecisive



an interesting bit of old stuff to look at is

the ignition timing controls on say a late 60's MB

dual points and vacuum advance and retard control

lots of crazy control boxes and relays


Fischer........ are you saying the Mallory Sprint mag, once on that bike, had an auto-advance unit?
 

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quote:Originally posted by HackAsaw

Fischer........ are you saying the Mallory Sprint mag, once on that bike, had an auto-advance unit?
No, it had no advance or retard and was strictly a drag racing unit with fixed timing(no box, or anything, timimg would stay the same all all RPM). It sure looked nice and shot a 2 inch spark, but the Dyna was more useful for the street.
 

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ok, I reread that and was just hoping such a beast existed

Mallory's literature indicates that it does and sorta by omission leading one to think there is something other than the timing lockout to couple the shaft

I have one set up for a 45 degree vtwin single fire
 
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