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Author Topic: Turbocharging carburated motorbike engine.  (Read 22858 times)
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moirmyster
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« on: August 01, 2008, 03:16:02 AM »

Im just in the procces of fitting a turbo to my honda xr 200,just wondering if it is as simple as plumbing up a pipe from turbo to the carb,then jetting to suit.I have heard from a few people saying,the carb needs to be in a pressurised box,does this sound correct.
any tips or help would be awsom.
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panic
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« Reply #1 on: August 01, 2008, 08:29:53 AM »

Since you prefer not to read this, I'll just take it down.

There, that's better.
« Last Edit: August 01, 2008, 08:01:52 PM by panic » Logged
Sumner
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« Reply #2 on: August 01, 2008, 10:33:49 AM »

I don't know if turbos and "simple" can go together.  I would recommend you read ...


Maximum Boost by Corky Bell

and

Turbocharging by Hugh MacInnes

and yes your friends are correct that you are going to have to at least make some changes to the carb if it is a blow thru system and that is the system of choice.

Good luck and do you have a turbo picked out for the bike??

Sum
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fredvance
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« Reply #3 on: August 01, 2008, 10:59:54 AM »

These seem to be the must read books/authors for turbocharging. Corky Bell's shop is about 5 miles from me, I have hear great thing about him for many years.

Fred
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Dean Los Angeles
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« Reply #4 on: August 01, 2008, 11:49:22 AM »

If you leave the carburetor in the stock location and blow through, the pressure would blow the fuel out of the carburetor, hence the need for a pressurized box.

If you mount the carburetor on the turbo you create a potential explosion hazard because the turbo and all the plumbing has a combustible pressurized mixture.

Other than that, it's just jetting.  grin The carburetor wasn't designed for anything other than non-pressurized running, so modifications have to be made to make it work.

On the other hand, I put a turbo on an Opel Kadett (yeah, a long time ago) with a draw through 38MM Mikuni carburetor. No waste gate. I had minimal tuning problems and put 50,000 miles on it with zero problems before I sold it. The only thing of note was the visible wear on the carburetor inlet from the air flow.
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MattS
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« Reply #5 on: August 01, 2008, 11:51:57 AM »

Im just in the procces of fitting a turbo to my honda xr 200,just wondering if it is as simple as plumbing up a pipe from turbo to the carb,then jetting to suit.I have heard from a few people saying,the carb needs to be in a pressurised box,does this sound correct.
any tips or help would be awsom.

IMO.....
For starters, a four stroke single cylinder is not a good motor to put a turbo on. The exhaust pulses are not close enough to keep the turbo spooled up. A mechanically driven blower, like what Fritz Kott has on his bike, is the way to go. Also don't underestimate the oil requirements for the turbo. I used an extrernal oil pump & tank for my BSA with a Yamaha 650 turbo but still fried the $600 turbo after two runs at Bonneville. I don't know if your motor is gravity fed or has a fuel pump or if you are going to use a blow-through or suck-through set-up. If you put the carb in a pressurized box, you will need to have a fuel pump or the fuel will be pushed back up into the tank. If you use a suck-through set-up that won't be a problem.

On my two attempts on my 500 BSA, I failed to make the turbo increase performance over N/A.  I guess I learned a lot and would do it different, and better, if I tried again.



Matt Shuss
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moirmyster
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« Reply #6 on: August 01, 2008, 07:49:14 PM »

ok so im using a RBH31 turbo preety small.should do the job.
Whats yhe difference bettween a suck through system,or the blow through system,which is the easyest to do and most effective.could any one explain.dont like the idea of a pressurised box.
I think i got oil pressure for turbo sorted us exturnal pump.
Any advice would be sweet.
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moirmyster
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« Reply #7 on: August 01, 2008, 11:34:53 PM »

Since you prefer not to read this, I'll just take it down.

There, that's better.

Lol sorry that was very usfull info,just after peoples opinoins to see whats a better way to do.
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moirmyster
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« Reply #8 on: August 16, 2008, 06:02:14 PM »

ok so iv got turbo mounted up and bike running,went with the suck through system managed to get enough oil pressure to the turbo.
it seems to spool up turbo fine got 5psi out off it,but im having bit off trouble tunning it it runs fine down low soon as u get over half throttle it dies,if only use half throttle ot goes fine and revs right out.
so iv tried bigger main jet and smaller jet doesnt make any difference.
iv tried a bigger carb still the same.
any one hav any ideas iv spent days tring to get right.
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kiwi
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« Reply #9 on: August 16, 2008, 11:21:18 PM »

Make sure you are getting enough gas through the needle and seat into the float bowl. You may be sucking it dry. Though if this is the problem it should at least run on full throttle for a short time.
Another thing to check with your turbo (won't be causing your current problem though) is that it has the appropriate seals for running under the vacum which it gets with a draw through installation. It will suck oil through if it hasn't.
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moirmyster
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« Reply #10 on: August 17, 2008, 03:19:10 AM »

ok cool thanks for that pretty sure it getting enough fuel as it got a 38mm carb on it.
the in take seems ok hasnt sucked any oil yet.
Another thing i didnt mention is when i tried to get full throttle flames come out the exhuast,and backfires,that may make sence to someone.
its weard as it feels like it to lean but then feels like it to rich.
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maj
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« Reply #11 on: August 17, 2008, 04:07:59 AM »

Carb size has nothing to do with it, the needle and seat letting fuel into the carb may not flow as much as the jet, when the jet is basicly being sucked on hard...when boosting
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moirmyster
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« Reply #12 on: August 17, 2008, 04:41:20 AM »

ok well its not even gettin on the main jet to make any boost to suck bowl dry.
i cant just wind the throttle on full will die,but if wind on slowly only using 1/4 to 1/2 throttle makes boost fine.
so to me its pretty much not even getting on the main jet,just using the pilot and the needle.
could be something to do with my setup not sure.
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Dakin Engineering
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« Reply #13 on: August 17, 2008, 07:43:03 AM »

I had a similar problem.
Ran great until the throttle was wide open.
I my case it was too small of hotside.

Sam
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kiwi
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« Reply #14 on: August 17, 2008, 01:54:16 PM »

38mm is too big. Try the stock carb.
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