crankcase breathing?

M

madrabbit15

New member
Do any of you guys who run the small valve head (1.5, 1.6, 1.7) have trouble with crank case breathing. I get a ton of oil in the catch almost a quart can after a hard driven race. The rings are sealing, the compression is nothing less than spectacular, we are already running low, low oil level. We cant think of any reason why it does this except for the fact that the small valve heads has such smaller drain hole through the block and because of that is pressurizes the oil out the valve cover. Does anyone have to run a crank case breather? We had no problems with a 1.8., we are just kind stumped.

Derek Ketchie
 
Derek, I never had any issues when I ran ITC. Even now with the GP car, I still only use the valve cover breather to vent the engine. Are you using the plastic cam cover/baffle? That helps a lot, although I never raced without one.

Have you tried running with a crank scraper?

http://www.crank-scrapers.com

It might help reduce the amount of oil in your breather. It also added almost 5 hp at 7200 RPM in my GP car.
wink.gif


MC

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Mark Coffin
#14 GP BSI Racing/Action Digital/Airborn Coatings/Krispy Kreme VW Scirocco
 
Just remember that you can not over breathe an engine.
 
Derek, you need to breath both the head and the block. My original IT car had an mech fuel pump blacking plate with a vent tube in it. In the course of many cars and motors later, running it and not running it, I choose to run it. When I didnt' run it, I would notice lots of blow by into the catch tank. Once you vent the block, the blow by almost goes away.

I still run both vents on my LP GP motor. Not quite as much compression as Mark's full prep Scirocco, but the theory is the same.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

racer_tim @ yahoo dot com

[This message has been edited by racer_tim (edited August 01, 2005).]
 
I really appreciate the Ideas. I might be experienceing more crankcase pressure running this 1.7 because its under square and the pistons rock in the bores more than all the other vw motors allowing for more blow buy. Thats a guess anyway. I think I am def. going to add a breather, I mean VW add a big drain hole to the later engines for a reason. Mark, I like the scraper idea, that teflon scraper looks pretty trick. That is def. somthing we will look into.

Thanks,

Derek Ketchie
 
Derek,

I had Walt make a crankcase breather for me out of the aluminum cover that holds the warmup regulator and covers the old fuel pump cam. Just TIG weld a -6AN fitting to that cover and run a hose from there to a "T" on your valve cover breather. I haven't had to use it yet.

You might ask: where do you put the warmup regulator? Well, that should be moved away from the block so you can better control its temperature, making your hot control pressure more consistent and adjust it to where you want it (wink, wink, nudge, nudge). All perfectly legal in IT. If you want to know more about my adjustable control pressure regulator setup, e-mail me at Scirocco14gpATbellsouthDOTnet

MC

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Mark Coffin
#14 GP BSI Racing/Action Digital/Airborn Coatings/Krispy Kreme VW Scirocco
 
My 1.6 Scirocco ITC engine once blew out nearly a full quart of oil in the first track session after sitting over the winter. I thought maybe I had a broken ring, but the problem mysteriously fixed itself after that. Weird. Maybe a "stuck ring"?

Al Seim
 
Mark,

Which one of those scrapers are you using?

Derek,

I've heard of people putting a flow restrictor on the inlet side of the head. The theory is, that it's not so much a crankcase pressure issue, but an oil volume issue. Those motors weren't designed to run at 5k - 8k all the time, so you're really moving a lot of oil around. Since the small bore (1.5/1.6/1.7) motors have a smaller central (and missing auxillary) oil return hole, you can't get the oil out of the head fast enough. Solution, don't put as much oil to the head, so you don't exceed the drain-back rate.

I've also heard of people putting a secondary return line from the head, straight back to the pan. Don't think this is IT legal though.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Originally posted by Bill Miller:
Mark,

Which one of those scrapers are you using?
Click to expand...

Actually, none of them. What I do is for each engine I build I make a cardboard template once I have the bottom end assembled. I try to get the scraper as close to the crankshaft as possible (.030"). Then I send the template to Kevin at Ishihara-Johnson and he makes a custom scraper for me. Since every engine is a little different (different knife edging, polishing, different rods/bolts, etc.) I need a slightly different scraper to maximize its effectiveness.

A lot more effort for probably minimal gain, but when you're trying to win a national championship you're looking for every little bit of horsepower you can squeeze out of the engine. The basic off the shelf scrapers probably do 90% of what a custom scraper will do, so it's cheap horsepower.

I'm also thinking that with the extra stroke of the 1.7 in Derek's car, the oil cloud around the crankshaft might be inhibiting the drain back of oil from the head. The scraper would cut that down dramatically.

MC


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Mark Coffin
#14 GP BSI Racing/Action Digital/Airborn Coatings/Krispy Kreme VW Scirocco
 
Bill Miller is right
biggrin.gif


Did you replace the oil pump with a "universal" hydraulic or "high volume" pump?

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Bill Sulouff - Bildon Motorsport
Volkswagen Racing Equipment
 
Originally posted by Bildon:
Bill Miller is right
biggrin.gif


Did you replace the oil pump with a "universal" hydraulic or "high volume" pump?
Click to expand...

Maybe that's why I haven't had problems, I only use the original 1.6 pumps. They use less horsepower.
wink.gif


MC


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Mark Coffin
#14 GP BSI Racing/Action Digital/Airborn Coatings/Krispy Kreme VW Scirocco
 
Originally posted by Bildon:
Bill Miller is right
biggrin.gif


Did you replace the oil pump with a "universal" hydraulic or "high volume" pump?
Click to expand...

biggrin.gif


Thanks Bill!



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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
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