New Katana 1100 carbs installed.

[skids]

Alright Snow, put away those steam tables!

Originally posted by Snow
Looks like I was just a little confused - I was thinking of thermodynamic efficiency, which for a gasoline engine is typically around 25% thermal efficiency.

[Dan Hodges]

Air Flow Requirements & V.E.

I will touch on this subject once more and then I will move on. The formula for determining the air flow requirements of a 4-cycle engine is, R.P.M. X C.I. divided by 2 X 1728 (3456) X VE. = air flow requirement of engine at it's peak volumetric efficiency. Volumetric efficiency reaches a maximum at a speed close to that where maximum torque at WOT occurs and then falls off as engine speed is increased to peak rpm. An ordinary low performance engine has a V.E. of about 75% @ maximum speed; about 80% @ maximum torque.A high performance engine has a V.E. of about 80% at maximum speed;about 85% @ maximum torque.An all-out racing engine has a V.E. of about 90% @ maximum speed; about 95% @maximum @ torque.A highly tuned intake and exhaust system with efficient cylinder head porting and a camshaft which takes full advantage of the engine's other equiptment can provide such complete cylinder filling that a V.E. of 100% or slightly higher is obtained @ the speed for which the system is tuned.The stock camshafts in the XS-XJ Eleven were a compromise by the factory to meet emissions standards while maintaining good driveability and low end torque.Unless you increase the camshaft timing and lift, more carburetor air flow will not help you as the cams act like a switch by letting the fuel/air mixture in and letting it out.Cams have to be chosen based on the motors size,compression ratio and what the motors intended purpose is,ditto for the carburetion and exhaust system as every component acts and is part of the system. An 1100 F Honda which made 108 HP S.A.E. had 33 MM Keihin carbs, an 1100 4 valve Susuki made 110 hp S.A. E. and had 34 mm carbs and a 1000 Kawasaki Eliminator made 115 hp S.A.E. and used 34 mm carbs. I have a Cycle World magazine article from 1987 of a build up of an 1100 F Honda by Byron Hines of Vance & Hines where he used Wiseco Pistons,Web Cams,ported heads,V&H 4 into1 header,trick clutch and some carb tuning with the stock carbs and with Terry Vance riding went 10.50 et in the quarter mile. A stock 1100 F would travel the quarter in about 11.25 et. A CV carburetor is very forgiving and as such most combinations come from the factory with carburetors that will flow more air than the engine will actually use.Of course if you are a doubting Thomas and don't believe anything you hear,only half of what you read and believe Byron Hines to be an idiot you will either have to; a. do an Av. B dyno test or; B. take it to a drag strip and find out for yourself because your behind cannot detect a plus or minus of 3 hp at WOT on the road.Gateway Motorcycle Salvage in St. Louis has a room full of used carburetors and if your BS 34's from your XS are junk and you do not want to spend the money to fix them,there is a set of Susuki carbs out there waiting for you.It's too bad we all don't live in St. Louis,then we could meet on I-55 in Illinois and see once and for all who spent their money in the right place.Unfortunately we don't and so I shall rest my case. Dan.

[MAXIMAN]

Touche'

[petejw]

hey dan,
that was a good read,
never knew how to actually work out
how to obtain V.E.
Now I'm curious, Im sure youve worked out yours,
any chance of sum figures?

[pggg]

Well, I always try and read the stuff Dan Hodges writes on this site, usually pretty interesting, but I'm certainly not interested in arguing anymore with that other J.A. all I can tell you is a good set of modern carbs can give your bike a REAL performance boost, end of story.

[AlanB]

Hi Guys,

My dyno charts have been fading on the shop wall too long to scan to show you, But my SG made 72BHP "stock+pipe" and 94bhp with Slingshot carbs, K&Ns and a days worth of dyno flogging. The midrange gains are bigger, and the respose to the throttle is incredibly better.

Shop was owned by a good friend of mine, who recommended the swap. They did it many, many times on a lot of bikes- but only one XS! Air-cooled GSXs like the swap even better than XSs do.

I was told to expect between 20 and 25 BHP for the swap......Pretty close!

There is more to this than the theory; the modern carbs plain work better.

Try it before you shout about it!

AlanB

[snowdog51]

new bike parts

i put on a front master from a 99 zx1100
on my 80 xs1100g. the diff was so big i thought i had 4 piston brakes are so good
even the mid 90's stuff is so much better.
i have a 2003r1 shock i going to install this wk end.
as ever bill

[Dan Hodges]

Air Flow

Originally posted by petejw
hey dan,
that was a good read,
never knew how to actually work out
how to obtain V.E.
Now I'm curious, Im sure youve worked out yours,
any chance of sum figures?

I'm assuming you want to know what the air flow and VE is,or what I think it is for my motor. The more elaborate dyno facilities use a probe on the intake side of the engine which provides among other things, air flow entering the intake tract/tracts and V.E.I have not had my motorcycle at such a facility and so I don't know what the exact V.E. is however it isn't 100% but should be in the 85% range and so based on the fact that my motor has 1179cc's which is 71.92 Cubic Inches and my rpm limit @WOT is 8500 rpm,my figures are thus.Because the XS employs individual runners and carburetors (no plenum) I will use one cylinder for my example. Cylinder # 1 possess 17.98 cubic inches and at 8500 rpm will pump 44 cfm @100% V.E. and 37.58 cfm @ 85% V.E. An XS carburetor @ WOT will flow about 80 cfm @ 1.5 inches of Mercury or 20.4 inches of H2o.Some shops use 3 inches of HG or 28 inches of H2o for the vacum drop and in that case the carburetor would natually flow more. 1.5 inches of mercury is the pressure drop used by Holley to flow all of their 4 barrels and so that's the pressure drop I used when having my XS carb flowed.The moral of this story is that a good set of properly prepared 34mm CV carbs with 30 mm venturis will flow more air than an XS can pump even at 100% volumetric efficiency.Hopefully this info will help you.

[Dan Hodges]

Re: new bike parts

Originally posted by snowdog51
i put on a front master from a 99 zx1100
on my 80 xs1100g. the diff was so big i thought i had 4 piston brakes are so good
even the mid 90's stuff is so much better.
i have a 2003r1 shock i going to install this wk end.
as ever bill

I'm glad you are confident of your bikes stopping power now,because with the roads and bridges in the Twin Cities area you better have good brakes!Thankfully you were not on that bridge when it collasped.What a nightmare.

[snowdog51]

bridge

when on a bridge i go as fast as i can,
[less time on less chance of bridge breaking when i'm on it.
as ever bill

[Dan Hodges]

Re: bridge

Originally posted by snowdog51
when on a bridge i go as fast as i can,
[less time on less chance of bridge breaking when i'm on it.
as ever bill

The mighty Mississippi here at the Gateway is a big mutha and with the exception of one,all of our bridges are much older than the bridge separating Minneapolis/St. Paul and so I shall keep your suggestion in mind the next time I cross the Poplar Street bridge.

[petejw]

Thanx for the info Dan,
I find all this stuff really interesting,
as i said before its been over 20 yrs since
ive been at tech, and around 15 yrs
since leaving the trade and the subject of V.E
was only ever touched upon.

[petejw]

Dont know how that happened,
wouldnt let me delete them,
perhaps a mod could delete the other
2 posts for me.
cheers


(Duplicate replies deleted - KT)

[Shappers]

Originally posted by pggg
all I can tell you is a good set of modern carbs can give your bike a REAL performance boost, end of story.

I wish you would make your mind up

When Ben made a post recently listing "Carb Replacement, Alternative Carbs, Different Carbs, Carb Options, Fuel Injection, Modern Carbs". You chimed in with this comment:

"I've heard that fancy F.I. /bigger/better carbs etc.. won't do much for an XS11 as far as performance goes."

I think you are just naturally antagonistic..

Just for the record, 95% of people looking to fit modern carbs and FI to their bikes are not doing it for performance. They are looking for a modern, reliable solution to providing accurate fuelling for their bikes. 25 year old carbs can be a pain in the arse!

[red bandit]

OK...so if someone wanted to do a carb swap/up grade which carbs from which bikes should he go with and what should he look for or stay away from? Simple question...right!!