Planning a new little project.

[Robby]

This may seem a touch silly, but it should be a cheap fun project.

The plan is to get a simple engine - i'm thinking big single for simple pipework, and get a cheap used car turbo off of ebay.

Bolt turbo onto engine, hook up oil and coolant feed lines as necessary, get exhaust running into turbo and air feed running into airbox.
Start engine.
Count to 10.

Big question is, how much electric stuff does a turbo need to work. If it has no electrics, will it just sit there with the wastegate open and do nothing, or can it happily run dumb until it explodes if I give it no electricity. The oil feed seems to be pressurised off of the bikes oil pump, so nothing for the turbo to worry about there.

Oh also, anyone got a 4 stroke big single they want to get rid of?

I'm looking at you Psychohippy.

[Jimmy]

I think it depends on the turbo/engine.

Some turbos are electronically managed/operated using the ECU and some are more basic and work via linkages etc...
____________________
I've confused my intentions with my abilities

[Kickstart]

Hi

Singles have a reputation for being difficult to turbo.

A turbo will need a very good oil supply. You might find the standard bike oil pump is not up to the job.

It should be fine with no power / control. Most older ones do not need anything like that.

Running it to the airbox is likely to leave you with a problem. Really you either need to run a suck through system (mount the carb before the turbo), which is simple but nasty, or a blow through system, in which case you need to seal the carb and vent it to a pressurised air supply.

Also getting a turbo that will work will be difficult. Chances of finding one 2nd hand with suitable size turbines is limited. Running the stock compression is likely to limit the life of the piston. Ignition timing will also need playing with.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Dup]

Not very knowlegeable about turbos and bikes.

www.zorstec.net have fitted a few turbos as well as other things. Might be worth giving them a shout.

I see a lot of turbos with their own air filter. Not on a bike. But this beetle is a good example, seeing as its a car turbo you are going to use.

[G]

Thinking about it, I believe singles and twins don't take turbos too well. I would expect it's something to do with the fairly uneven pulses in the exhaust, while fours are much better.

I'm sure you could find some fairly simple old four to do (infact, isn't there a GPZ engine some where?)... if you're going to pressurise the airbox it shouldn't complicate things too much.

[Danny]

[Robby]

Right then. I'll try to do away with the airbox then.

Or cut it off and use the pipework from airbox to carbs.

Ideally I'd like to use one large carb feeding 4 cylinders, but that could require thought.

Danny. My good friend. I'll give you a shiny coin for it, the carbs, airbox, electrics and the old knackered exhausts - i'll chop them up a bit but the headers are still good.

[Kickstart]

Hi

The airbox is plastic and may well not take the heat. Also the links from the carbs on to the airbox are unlikely to be strong enough to take the pressure, so will just pop off.

If you just plumb a turbo to the airbox without sealing the carbs then you will land up with stuff peeing out of the carb breather pipes, and possibly pressuring the fuel tank. Won't be a problem for long as no fuel will be drawn from the carbs so the engine will die.

A single suck through carb is a horrible solution. By the time the fuel / air mix has gone through the turbo and up 4' of pipe up to the inlets and round loads of bends, most of the fuel will probably have congealed into large drops that will not burn very well.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Robby]

So ideally I want a single carb after the turbo, running to the inlet ports on a metal manifold, all bolted together.

[Kickstart]

Hi

Why would you want a single carb on a multi cylinder bike? Really screws up the fueling as it is just about impossible to make each inlet flow in the same way (one carb between 2 cylinders can be made to work OK).

Yes you want the carbs after the turbo. The most important thing is sealing the carbs and venting all the breathers to a pressurised part of the intake system (ie, plumb them to to somewhere bewteen the turbo and the carb).

You will also probably need a fuel pump as otherwise the pressure in the float bowl will stop the fuel flowing from the tank.

Metal manifolds or strong rubber ones.

One thing you can do is to put an airbox around the carbs, and pressurise that airbox with the turbo. Saves sealing the carbs! Trouble is that it makes adjusting the carbs a nightmare, and you have to work out a way of getting the fuel pipes and cables to the carb without leaking boost pressure away. This was how the early (non fuel injected) Maserati Biturbo worked.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Robby]

A box around the carbs sounds like a very italian way of fixing a problem, i'd rather seal them.

Electric fuel pump is no problem. Making it stop pumping could be, or stopping it from flooding the carbs.

Vent tubes can be plumbed into the air feed from turbo back to airbox/plenum. Home made plenum of some description looks like the best solution now. Making it could be fun.

[kev]

Not sure how twins do with turbos but I do know twins go very well with superchargers.
____________________
20:02:36 Jammy-R6: any holes a goal
20:02:48 kev: even if its a hairy mans arse
20:02:56 Jammy-R6: hell yes

[Kickstart]

Hi

A box around the carbs is easier than sealing them. It will not take much boost to blow off any pipes which are not very securely attached.

The fuel pump will have to supply fuel at a fair pressure. Remember than a standard pump may only provide around 5psi, but you need a pump that can supply that level of pressure plus the amount of boost pressure, so with 1 bar boost you need almost 20psi of fuel pressure. Most bike bikes only supply fuel on demand, and they would probably get very confused with overcoming boost.

To give you some indicated of the pressures required for turbo cars, a typical Bosch fuel injection pump is capable of supplying fuel at up to around 50psi, which is regulated down to around 30psi (fuel pressure regulator after the injectors). The pump for Charlottes Maserati supplies fuel at up to 120psi.

Best thing to do would be to play really silly buggers and fit fuel injection. Might be easier anyway!

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Robby]

You're making carb before turbo sound better.

[Kickstart]

Hi

It is far simpler, but far worse for power and emisions (not that that will bother you).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing