cfm for the carbs?

[ohgoodtimes]

Just wondering is anyone could ball park the air flow for the gs'. I have an 83 750e but any bike would be useful info. I am working on a project and need to know so I can calculate boost and no it is something extrememly crazy. You will have to wait and see.

Also how much can the carbs handle before needing to be upgraded, rejetted extensively, etc.

[49er]

Flow Calcs

Just wondering is anyone could ball park the air flow for the gs'. I have an 83 750e but any bike would be useful info. I am working on a project and need to know so I can calculate boost and no it is something extrememly crazy. You will have to wait and see.

Also how much can the carbs handle before needing to be upgraded, rejetted extensively, etc.

The theoretical flow rate for a 4 stroke engine is capacity x 0.5 rpms . In your case 0.750 x 5,000 = 3,750 litres per minute. This is using a 10,000 rpm max.
The reality is quite different. It all depends on the efficiency of your engines state of tune. Things that influence this are CR, camshaft profiles, timing and lift, porting, carb sizes and types, inlet track length/size/shape, exhaust design and tuned length, ignition timing and total advance, exhaust gas temperatures,etc,etc.

The ballpark figure as a percentage of theoretical flow for a highly tuned naturally aspirated road going machine is usually in the 85-90% efficicency rate. Your 16 valve TSCC designed engine should fall into this area.

I believe that your 83 750E runs VM26SS carbs as stock. These carbs will flow adequately for engines up to 1000cc. They were fitted to the 78-79 GS 1000's.
It all depends how radical your tuning plans are as to whether the VM's will flow enough. If you are planning forced induction, you can afford to go bigger with the carburetion or injection, if that is your plan!

[ohgoodtimes]

that is probably the best answer I could have asked for. I am planning on adding 2-4 lbs of boost with an electic motor and thus needed to see how much more air i needed to add to achieve the boost. Will the air density matter in my calculations? I am in Denver and the air up here just aint as thick.

P.S. I am trying to improve mountain performance which can be around 7000-9000.

[49er]

that is probably the best answer I could have asked for. I am planning on adding 2-4 lbs of boost with an electic motor and thus needed to see how much more air i needed to add to achieve the boost. Will the air density matter in my calculations? I am in Denver and the air up here just aint as thick.

P.S. I am trying to improve mountain performance which can be around 7000-9000.

Firstly, I misled you with the info on your stock carb specs. The info I got from the motorcyclespecs.co.za website is not always reliable.

http://www.motorcyclespecs.co.za/model/suzu/suzuki_gs750ez%2082.htm

The picture supplied of the '82 model clearly shows a set of CV carbs fitted. The write up below the specs also confirms that they run CV's.
This makes sense, as Suzuki almost exclusively fitted CV carbs to all it's road bikes from '80 onwards. One notable exception was the '85 GSX750R that was fitted with a set of VM29SS carbs.

How are you going to power an electric motor capable of forcing 2-4 psi boost, for prolonged periods? The GS electrical system barely handles it's stock electrical demands as it is!

Are you planning to blow through or draw through the carbs? I'm not sure how your CV's will appreciate being blown through!
You will need to experiment with the jetting. Theoretically, your added boost may help correct the air/fuel ratio at 7000 -9000, but there'll be plenty of tuning required, to get it right.

Keep us informed as you progress.

[ohgoodtimes]

Well I have a few ideas in mind one being a higher tourque motor, with lower current draw and low rpms just geared to a blower. Obviously this will take a good deal of wiring and planning, but i am considering other alterations to help with the charging (i.e. solar panel?). I figured the bike would be easier to try the lectric motor idea on because of its smaller air volume intake compared to a car. Yes I was planning on doing a blow through. it would be the easiest way to get the blower on the bike. I know jetting is going to be a pain but I will do a lot of number crunching. Lastly I will be rebuilding all th carbs to handle the boost, this has always been on my mine; the gaskets etc. After I do all the math and look for parts my next update will tell if this is really even possible or I will have to start from scratch.

[49er]

Well I have a few ideas in mind one being a higher tourque motor, with lower current draw and low rpms just geared to a blower. Obviously this will take a good deal of wiring and planning, but i am considering other alterations to help with the charging (i.e. solar panel?). I figured the bike would be easier to try the lectric motor idea on because of its smaller air volume intake compared to a car. Yes I was planning on doing a blow through. it would be the easiest way to get the blower on the bike. I know jetting is going to be a pain but I will do a lot of number crunching. Lastly I will be rebuilding all th carbs to handle the boost, this has always been on my mine; the gaskets etc. After I do all the math and look for parts my next update will tell if this is really even possible or I will have to start from scratch.

Great. Sounds like you've done a lot of the research. Can I suggest that you fit slide carbs such as the VM's instead of those CV's. I think that you will find their design and operation will work better when blowing through. A set of VM29SS carbs would work well. They may be hard to find though!
There are plenty of used VM26SS available on Ebay, and they would still work OK.

[tkent02]

Why not just throw in an 1100 motor?
I'm all for doing goofy stuff like this but a stock 1100 motor will go a lot better.

[Zook]

And to have solar panels that will put out enough current to be of any benefit would be huge.
I would find a turbo off a small automobile engine and plumb it in.
An electric motor that's capable of making 2-4# of boost would be big and heavy.

[49er]

If this is your daily ride, I would probably listen to the "don't do it brigade".
If not, have a go. Nothing ventured, nothing gained!
But be sure you can afford to do the repairs, if necessary.

If I had listened to many of our long time owners of GS850's, I would have believed that their performance couldn't be improved too. They go so well in stock trim (that's why you can't get any O/S HC pistons for them). The O/S piston mods I did have made a huge difference to my 850's performamnce.

They are probably right about the solar panels though. We did have an Aussie member last year who had a solar panel fitted to his GS1100G sidecar. He swore the solar panel was only used to keep his beer cool!

And no, I can't say that my bike is older than me, not even close to it! But if I could, I would still be prepared to have a go.

You may just discover something special!

[Steve]

A couple of things to consider (beyond those of which you have already thought)...

If you are going to blow through your carbs, you will have to totally seal them so that you pressurize the float chambers, too. Otherwise there will be some serious starvation issues. By "sealing the carbs", I mean that you will have to build a chamber completely around them, sealing the openings for the throttle and choke cables, too.

You might think that simply blowing extra air through the carbs would be the same as hooking small carbs up to a big engine, meaning that you would have extra airflow. Not so. You have to consider the pressure differentials. With a large engine/small carb setup, you will always have atmospheric pressure in the float bowls and a vacuum in the venturi that will draw fuel through the jets, even though the jets might not be able to supply enough fuel. If you pressurize the air going into the venturi, it may not drop enough pressure as it goes through, and will actually push fuel down the jet and back into the float bowl, instead of sucking it up into the throat where it will go into the engine.

I also agree with the thoughts about electrical supply for a sufficient motor. Even though you are planning a low-rpm motor, it will require a lot of amps to provide sufficient torque.

[drhach]

Is the charging system capable of running that electric motor? I would think that your biggest hurdle would be that. A DC motor with a squireele cage shouldn't be too terribly big. But it seems with all that gets said about GS charging systems, maybe that woul dbe your sticking point. Although, some people have run FI. A motor should consume less than a fuel pump and an ECU. Maybe.

[ohgoodtimes]

I have been looking around a lot and the space i would have to cover with solar panels to power the motor independently is crazy. So I was thinking of other options. From the way it is sounding I am going to have to wire the turbo to engage around 4 grand, this would reduce draw from the battery until it is charging system is putting out more. Hopefully this combined with the solar panel could closely balance the power. Kind of like under 4000 rpms the solar panel will be charging the battery and then after 4 g's the bikes system would take over. This is starting to sound a bit complicated for a pretty standard bike. With that said any other ideas? Maybe I should attach a gear to the rear wheel to turn the turbo and have an electric motor to keep it spinning when it is stopped?