Topic: Drouin Supercharger

[jpswino]

Anyone running a Drouin supercharger?
Got pics? Or info on what engine mods you did.
How do you like it? Any advice from experience on using one of these?

[scunny]

http://forums.sohc4.net/index.php?topic=46494.0
let the search function be your friend

[Sam Green Racing]

Yes Scun but that story ended 12 months ago without a final outcome.

Sam.

[jpswino]

Not to sound obnixious. But what I asked was if someone is running one. Yes I know how to use the search button and yes I have read that thread. There is no one that posted in that thread that has actually used one. I am looking for someone that has actual experience with the Drouin unit not theory on how to use a supercharger.

The Drouin is a particular unit. In fact it does not "compress" air like a roots style blower. This fact is probably why it was considered to be somewhat not so great. Most people are expecting giant gains immediately off idle from a supercharger but that requires a special build motor in most cases.

The Drouin in fact is the happy middle ground between a turbo and a roots style blower that compresses air. The beauty of this piece allows you to run up to about 11:1 compression since there is no compression from the unit. It works much like a turbo in that it uses a turbine  and really is just a super positive air charge for the motor. It is better than a turbo (in my mind) in that it does not require exhaust velocity to spin the turbine but rather is driven off the crank using the mechanical advantage the roots style blower has off idle. The disadvantage is that since it does not compress the charge the gains are minimal. But as it winds up the gains increase like a turbo.

[jpswino]

The advantage the Drouin has down low in the rpms is the mechanical fuel injector that is part of the set up. I don't think people realize you do not use carbs with this unit. The 1977 review I read describes the throttle response to be absolutely incredible, crisp and super smooth throughout the entire power range.

This throttle response and fuel efficiency is what makes this unit special in the lower power bands with the hp gains coming on after 3000 but even more so after 5000 rpms.

This unit was really designed to be a bolt on item to an otherwise stock motorcycle. It was never meant to be a super high gain unit for drag racing. I am sure this misunderstanding of its intention for use also contributes to the idea its not so good a design.

The other issue that makes my inquiry different from the thread referred to is I actually have the unit in my possession. I am hoping to find someone that has used the unit and may have tips and tricks to its set up. The only one I have seen in use is the one Carpy did. Perhaps he is the only reference out there?
I am still hoping one of you guys here has had or still has one and can help with the install.

[jpswino]

This may make for an interesting thread on its own merit if this unit really has not been used on this forum. You guys know much more about the cb750 than I do.

My plan is to test the Drouin and install it on an 836 motor I got from the HC board. Motor was built by another guy separate from the one I purchased it from. I'll put a set of carbs on to make sure the motor can run and its in time. Then swap over to the Drouin for testing of set up. Plop the motor into my current chop build and run it to see what happens. If all goes well then it will go on an RC 1000 motor I have for another bike I'm putting together.

I've always got several builds going so options are plentiful for testing.

[Bill/BentON Racing]

I ran one back in the day.Mine had a flat slide guillotine set up.One needle, could move up or down w'set screw.Pressure/vacuum made it where I had to install push /pull type cables.Installed on stock CB750K'75 model.Had RC 4-1,Barnett clutch,plastic fenders,drag bars,rear sets,struts,630 chain set up.drilled disc etc.Ran 8-10lbs.boost max.Some problems w/belt alignment.flat belt,not the cogged one.Other people had better sucess with other carbs,or different set ups.Plenum fit and seemed fine.Ran my buddy's Z1-R that weekend @Rockingham,N.C.Beat him by .03.High 7's low 8's. 1/8 mile.Z1-R had just been tested by Cycle magazine as first stocker to run in the 11's! ,Bill

[jpswino]

Thats the kind of info I'm looking for sir. Thank you. Got any pics?
The pulleys I have use a ribbed belt. I am thinking I'll try the slide system to start with as well. I have it complete except for the cable. My understanding is the boost goes as high as 11lbs up around 8k rpms.

Can you tell me more about this vacume issue? Does the unit make the motor run hotter? I know by design the unit itself should not heat up since it does not compress. Did yours stay cool, somewhat?

Was it a pain in the ass to tune? There are only two adjustments right? Idle and air?
Seems there is not way to shut off the gas with no float bowls. The article I read says you need to shut the petcock off immediately upon shut down. How does that effect start up?

Still sounds like your bike was quite fast. Overall, did you enjoy the set up?

[jpswino]

For those interested. We are talking about this unit.

[andy750]

Im sure 1080 and 754 will be along shortly to give you their info but I just wanted to say what a cool shop/builds you have! Very very nice.

Good luck with the supercharger.
cheers
Andy

[Bill/BentON Racing]

Damn,those pics brought back memories.Engine did not run hot.Two adjustments as you said.Hard to get it right @ both ends,but when you did it was a hoot.Made a nice sound.I remember cutting out belt cover,painting plenum and brackets.Two inch hole in dyno cover center probably most challenging.I had Drouin do it if I remember right.I'm telling you for price and results had he had a better fuel delivery system he would have sold a ton.Definitely took some time to get right but worth it.....ould also outrun my buddy's 811cc 750F '76.Had to be careful not to use to much cam or compression.Will look for a decent pic.Good Luck,Bill

[Ricky_Racer]

JP, the Drouin in the CCC posted pics is mine. As some of you know, I picked up a second complete kit in the last couple of weeks but I'll be going through this second one since it needs a good detailing. The impeller spins freely but I want to see if I can find modern performance bearings (ceramic?) to replace the originals. Supposedly, the speed at which the impeller spins may be past the design limits of 1970's bearings and this is the major problem with the standard Drouin.  If anyone has info on bearing numbers/interchanges for the Drouin please chime in.

I like the Drouin precisely because it was engineered as an upgrade to a stock engine. Compared to an all-out performance redo, the Drouin is an inexpensive upgrade that can be transferred from bike to bike.

Bellcow, how did you install push-pull cables on the Lakes-type injector of the Drouin? Getting this thing to close under boost is of sufficient concern that I've been looking into adapting a carb to replace the injector, but I'd like to try playing with the injector first. I'd just rather not be hospitalized from my "playing." 

ANYONE who has personal knowledge of the Drouin.. please contribute to this thread so the entire community, including those who will try this huffer in the future, can benefit. Some time back I researched sourcing replacement belts for the blower. I'll go through my notes and post the info as soon as I can.

Thanks!  RR

[jpswino]

Now there is someone I know from HC. Thanks man. Didn't know or realize you were running a Drouin. I have a few sources for the belts that have been given to me. I'll post em' as I see fit after calls to confirm they do have them.

I never heard of the vacume coming off throttle being a problem but I certainly see the issue now that it has been suggested. I'd like to know how that was handled as well.

Originally I was toying with the idea of running sportbike injectors like 23tbucket did on his matic. Not sure if it would work but having the microsquirt to manage the system would be badass! But for the Voodoo Chop perhaps keeping things mechanical better fits the look I am after. So I'll try the slide deal first. And I have it already so why not?

There is a fitting right in the center of my log manifold. Do you have one as well? Whats it for?

[jpswino]

And thanks Andy for checking in on my stuff. Your comps are well appreciated.
The Voodoo Chop will ultimately be home for the Drouin....hopefully.

Thinking about testing it in the Lowlife Build though with the 836 motor.

[Ricky_Racer]

Hi Joe. I assume it's for the plastic tube to connect a boost gauge. Of course you could always use it to plumb in NOS!    

Since this whole thing is just for the S&G's of it, I've been looking at small single-port throttle bodies to replace the "injector" as well as the usual Mikuni HSR. Not quite to that point yet, though.

If you want, pm me an I'll give you a call. RR

[jpswino]

Hell yeah, keep me posted. I don't really know squat when it comes to options here. Just want to get it right. Glad there is someone with firsthand experience. For a moment I was begining to think everyone had given up on these units!  lol

Yeah, and now that you mention it, I was told by themotorcycleguy when I got it that there was a guage originally. I obviously don't have that. That makes sense for that fitting. duh!

hhhhmmmm? I like you "other" idea. Now where do I hide a bottle?  

[Bill/BentON Racing]

You will.

This is the best I can do right now. It was FUN!Bill

Good Luck.I had more time in making push/pull WORK than anything else.As they said hole was for fitting for boost gauge.

[jpswino]

Very cool. I like it!

[Ricky_Racer]

"Good Luck.I had more time in making push/pull WORK than anything else."  Bill, do you remember any of the particulars? Thanks. RR

[SWEETPEAUK]

Mine used a Bendix carb so can't comment on the standard setup. It would idle no problem down to 1000 rpm and pull clean to the redline. Mine went tits up when one of the bearing let go and the impeller ground away in the casing. Still have it in a box somewhere just needs a new impeller and man shaft. Would also add high flow tap,rev limiter and ear plugs to your wish list. Also if you have long legs the blower can get in the way.
Paul

[Ricky_Racer]

Okay, I spoke with Denis Cavalier today. He's been dealing with Drouins for years.  Got some interesting info: He recommended "Air Bearings" as replacements (but I think he meant ceramic bearings), having the impeller Magnafluxed and balanced to 30K RPM, checking all the mating surfaces for flatness and having them milled if necessary, and the use of gasket sealer rather than the original paper gaskets. He also indicated that Gates Belts could supply the replacement belts of both the Gilmer and flat varieties.

Interestingly, I thought the Drouin was limited to 8 PSI, but he told me the the Honda Drouin model would put out 15 PSI!  That's a good way to hand-grenade a motor..  

We also discussed the slide injector... He said that the majority of people using the Drouin long-term have been successful with the stock injector, but that the cable adjustment was very critical; the slide had to close completely.

BTW, if anybody does a little research, you'll find that Drouin made a blower package only for the Kawasaki Z1 that used a Rootes-type blower rather than the rotary style that we're using. Yep, I know it looks like a Magnacharger... but it ain't!    RR

[traveler]

That...has got to be the most badass Kawi I have ever seen.

I SERIOUSLY would LOVE to be able to buy that.  THAT would make me a happy man.

~Joe

[Big Jay]

The Drouin is a particular unit. In fact it does not "compress" air like a roots style blower. This fact is probably why it was considered to be somewhat not so great. Most people are expecting giant gains immediately off idle from a supercharger but that requires a special build motor in most cases

A roots style blower does not compress air, that is why it is called a blower, not a supercharger. It simply moves a given volume of air from the entrance to the exit. The boost comes by having more volume moved that the motor can inhale. All of the pressure increase takes place in the manifold and bottom of the blower.

A screw type supercharger like is used in top fuel dragbikes and alky dragsters and funnycars is a true supercharger as it compresses air inside of the devise.

[Ricky_Racer]

Just some helpful links:

Reference material:
http://commando.yolasite.com/drouin.php
http://atlanticgreen.com/ndsc.htm
http://victorylibrary.com/supercharger/super-c.htm

Kawi:
http://mikesbikebarn.com/photos/index.php?cat=5
http://kzrider.com/index.php?option=com_kunena&Itemid=116&func=view&catid=11&id=310001  RR

[jpswino]

Thanks Big Jay for the further detail.

RR, seems the fellow you spoke to is the guy for sure. I'll find a way to scan and post the magazine article I have with the dyno and road test from 1977. In that article they mention 11lbs of boost and tested up to 8k rpms.

Did the guy you spoke to mention the push/pull throttle cable and/or another way to address backing off the throttle? I'll make sure the slide closes all the way for good measure.