Topic: Crankcase vacum for CB750

[chris]

Has anyone used a crankcase vacum system to increase the performance.If so and if it has been successfull approximatey how much has it increased the performance and how was it set up thanks

[kos]

As for a system that was run off and electric air pump...

Yes, we tried this on out AHRMA Suzuki GS750 Vintage Superbike racer back a few years ago, but as it was a roadracer the tech guys were none to happy about the idea of a vacuum system on the bike that might cause extra oil/air to be placed in breather tank and thus might come out on track. We stopped with the idea. Also the bike was constant loss ignition and we did not have enough battery capacity to keep pump running the entire race. So we devised a system with a switch triggered by the throttle grip... that would only activate the electric pump at higher throttle openings. This was only tried once and rider was not happy with the "extra" hit you would get just coming off corners. This would upset the bike when it was leaned over....something a roadracer does not like.


Has anyone used the system by where the vacuum is created in exhaust collector and with a reed valve between the crankcase breather and the exhaust... had any results to report of?

KOS

[Bamboozler]

Has anyone used the system by where the vacuum is created in exhaust collector and with a reed valve between the crankcase breather and the exhaust... had any results to report of?

KOS

Interested in this myself for a boosted application. I'm assuming naturally aspirated vs turbo applications should be no different regarding this subject. I have a friend who implemented this on a turbocharged 2.0l automotive motor to help ventilate the crankcase.  What I'm wondering is how you gauge the effectiveness of the system? My friend didn't really do much more than monitor what accumulated in his catch can.  I can't report on what he noticed as he added the ventilation system at the end of last year and promptly put the car in winter hibernation.  There seem to be a bit of blow by in my CB at idle but no noticeable smoke while loading the motor (that I can see out of the rear view mirrors), I'm wondering how to determine the effectiveness of such a system if it were to be tried?  Vacuum gauge on the crank case?

[kos]

OK, For starters on a Pro Stock Suzuki currently racing today in NHRA... their vacuum pump increases power on a dyno by 60-65 HP, by eliminating parasitic, internal engine pumping pressure.


 Use 350-365 HP as a real number of the HP.. these fours develop for 1/4 mile at a time. And scale down to your engine sizes.

KOS

[chris]

Thanks for information we I forgot to say that we are working on a system where we are creating a venturi system in the exhaust and not using a pump any suggestions ?

[Bamboozler]

Interesting numbers to say the least! 

I plan to take a trip to the dyno with my CB sometime in the near future to see where it sits and would be willing to weld in a 45° bung and run a hose with check valve up to a tappet cover that's cracked and needing some weld attention.  I can do a basic before and after (scavenge system installed) pull and see if there are any notable gains.  Couldn't hurt to try and I'm interested to see if there is anything to be gained.

[kos]

Thanks for information we I forgot to say that we are working on a system where we are creating a venturi system in the exhaust and not using a pump any suggestions ?

Get a hold of the book, "Chevrolet Racing Engines" by Bill "Grumpy" Jenkins... as he explains in detail how to  do a venturi system, like he invented for his Pro Stock Chevy racer of the period, "Grumpy's Toy"!

KOS

[turboguzzi]

some mind readers here..... working on such venturi system right now, it might be even ready for next race, will certainly dyno with and without....

see the pipes coming of cyls 1 & 4

got the inspiration when I go the chance to see valentino's M1 motor up close, it runs such a system. motogp, here i come!

TG

[chris]

This is interesting and some mindreading going on. I will keep you informed of our progress and hopefully you will too thanks

[Bamboozler]

some mind readers here..... working on such venturi system right now, it might be even ready for next race, will certainly dyno with and without....

see the pipes coming of cyls 1 & 4

got the inspiration when I go the chance to see valentino's M1 motor up close, it runs such a system. motogp, here i come!

TG

Thanks for posting that pic of Rossi 's motor, very neat to see.  Wondering where you were at to get those pictures and if you have any detail of which races/championships it may have seen?  Good luck testing out your vacuum system, hope you have promising results.

[turboguzzi]

It was an open day at the motogp HQ... will send you more details in PM.

TG

[Howell]

The Ten Kate Supersport 600 Honda's used also a vacumpump system in the supersport worldchampionship.
The other teams complained about it  , they had to take it off.
It reduced the speed of the Honda's significant.

[turboguzzi]

The Ten Kate Supersport 600 Honda's used also a vacumpump system in the supersport worldchampionship.
The other teams complained about it  , they had to take it off.
It reduced the speed of the Honda's significant.

They still know how to make motors in Ten Kate, even if the rumor is that Rea's motor might come straight from HRC Japan....

But that pump story put a big shadow on all of those world supersport championship they took, it was electrical by the way, not driven by exhaust venturi

BTW, I know you been busy but if you get the chance to see replays of this last weekend's world superbike races in Assen, do it, some of the best racing I've seen in years, and honda took a double header.

If Yrjo has trouble with drum brakes, he should learn from Rea, this guy just doesnt use his brakes at all

TG

[Howell]

The Ten Kate Supersport 600 Honda's used also a vacumpump system in the supersport worldchampionship.
The other teams complained about it  , they had to take it off.
It reduced the speed of the Honda's significant.

They still know how to make motors in Ten Kate, even if the rumor is that Rea's motor might come straight from HRC Japan....

But that pump story put a big shadow on all of those world supersport championship they took, it was electrical by the way, not driven by exhaust venturi

BTW, I know you been busy but if you get the chance to see replays of this last weekend's world superbike races in Assen, do it, some of the best racing I've seen in years, and honda took a double header.

If Yrjo has trouble with drum brakes, he should learn from Rea, this guy just doesnt use his brakes at all

TG

I saw the races on Eurosport already on sunday evening , we were early home from Spa.
Indeed one of the better races.
To go fast you must have bad brakes or no brakes an old tuner once said to me.

[kos]

Very exciting racing...to say the least! To win at the Circuit ven Drenth Assen, Holland(the Cathedral of Speed)... is is big deal in Europe, as this is a track that was designed to race motorbikes only and until very recent...no cars were allowed to race on this track. Every corner has a slight banking and is very exciting to be there and to watch.


I hope to go back again, but I must attend classic bike races at Spa... first!

KOS

[Howell]

Very exciting racing...to say the least! To win at the Circuit ven Drenth Assen, Holland(the Cathedral of Speed)... is is big deal in Europe, as this is a track that was designed to race motorbikes only and until very recent...no cars were allowed to race on this track. Every corner has a slight banking and is very exciting to be there and to watch.


I hope to go back again, but I must attend classic bike races at Spa... first!

KOS

Hi Kos,

It was the Cathedral of Speed ,  they changed the circuit from 2006 till now every year , all the real bankings are gone  
This because of the safety and also for the cars.
We raced there three weeks ago.

Old and new circuit:

[kos]

Sad, BUT there is one left. Road America in Elkhart Lake Wisconsin! 4 Miles long... a true Grand Prix track where you have two very long straightaways, one being almost a mile long! With extreme elevation and every different type corner possible....Sir Jackie Stewart, Dan Gurney, Bruce McLaren,  Denny Hulme & Mario Andretti...pronounced it one of three best tracks in the world.

I think they rated Spa and Monza as the two other, true GP tracks.

KOS

[Old Scrambler]

Now you've said it..........and think what a vacuum pump would do to a CB750CR on those long Road America straights.

Are we going to see you June 11-13?  Last year the Norton Manx bikes were really stepping out from the rest in their class. There were 6 or more CB750s and more are expected this year. 

[brandon]

Does one system have more benefit(s) over the other? I'm not on the up and up with the electrical pump system so I'm asking with experience using the vacuum/venturi style systems - which are relative to throttle position/intake velocity, have less parts, and a few other little things.

One obvious thing is that the electrical pump needs...electricity and thus puts that much more strain on an old CB system. So...one better than the other? Personal preference? Yes/no maybe so?

I would be interested to know!

[bucky katt]

i found the parts from the crankcase evacuator system i ran on the mustang when the motor still had a carb and no turbo. i'm thinking about experimenting with the mac header i have, see if it helps or hurts performance.

[BLUE71TURBO]

 I can see a purpose for a race engine. As for the street........forget it, useless.  I run up to 20lbs of boost on my bike and have two
vents, one from the valve cover and one from the crankcase. Both have clear hose and i have not seen alot of blow by at all.