Thoughts on Crank case evac systems?

[Superdave]

I've got to modify my headers this spring for a different exhaust setup anyways so i was thinking about adding in one of the old school crank case evac systems like the one that Summit sells. http://www.summitracing.com/parts/SUM-120108/


My ITB setup combined with the cam cause very low engine vacuum at idle and cruising speeds, my oil is trash after only a few hundred miles. I'm sure the PCV system is doing very little.

Most reports on these types of setups say you can usually pull 2-3" of vacuum in the crank case at the cost of some exhaust smoke. Mechanical and electric pumps are out of the question for this season


Anyone have any direct experience with this setup?


Thanks

[geoffinbc]

Never used them but you still see them now and again.

[NateD4]

I don't understand why your oil is trash after only a few hundred miles...

[NateD4]

What kind of oil do you run?

[Superdave]

Royal purple, with basically no airflow through the crankcase all the blowby is contaminating the oil pretty quick. It's probably closer to 1K miles.

[dskopek]

I have used this style before and they work great! Just place them in the collector right after the merge. The only problem is if you want to run a exhaust system they will not work at all, only on open pipes. You might be able to run them if you weld them in after the mufflers and only have short pipes after, don't know for sure.

[NateD4]

So what exactly is happening to the oil that makes you decide to change it?

[robertisaar]

gah, 1K mile oil changes using the most expensive oil known to man? i'd just jump straight to the electric pumps, but i have no idea how these exhaust based ones work. if i had to guess, i'd say they work on a vacuum pulse being generated by the exhaust pulses?

[geoffinbc]

Yes they work on a savaging effect. Low pressure in the exhaust will draw the higher pressure air in the crankcase out.

If you want a good system then a belt driven pump is best. Plus it will actually reduce blow-by by improving rings seal and it makes life easy on oil seals. It will also return some horsepower not only from the improved ring seal but also from the reduction in windage. If you don't want to drop big money on a new system I am sure there are tons of used ones on E-Bay. I want to put one on my pickup where the old AIR pump used to sit.

[Superdave]

So what exactly is happening to the oil that makes you decide to change it?

The last time it was so fuel contaminated after a day at the strip that i could actually set the oil on fire with a lighter, most of that was probably from the o2 crapping out and the engine flooding though. I had to drive home from the track in open loop and that's never a good thing in my car.

Usually it's just pretty black. I've set samples side by side and it's almost identical to my truck's oil after 4K miles. Pretty similar looking under the digital microscope as well.



The system is pretty cheap, i'm going to pick one up and install it in a few weeks once the weather stays warm for more than a day. I've also got quite a few more goodies in the works, possibly even a water-methanol injection system.

[bob442]

You can't pull vaccum through you your iac setup?


Sent from my iPhone using my iPhone at work cuz I have nothing to do

[robertisaar]

IIRC, Dave doesn't run an IAC.

[Superdave]

I've got one in there now, i was having stalling issues pulling up to stop lights and it helped. The IAC is in a very small common plenum with the rest of the vacuum ports, everything is providing just enough air for the engine to idle at 1K RPM pulling around 6" of vacuum. That's ok for idle but blowby is at a minimum there, it's under load and WOT that's the problem.


Cruising at 70 MPH in 4th gear with the TCC locked is around 2400 RPM, the engine is pulling 2-4" of vacuum there. If i downshift to 3rd and keep the TCC locked i can get it back up in the 15" range and the engine is so much happier but there goes any sort of gas mileage. lol


These ITB's are really proving to be less street friendly than i originally hoped. Good thing it's not a daily driver.

[Mars]

Yup, I have slashcuts on my Camaro and the Fiero. They work MINT ! Do it up and you will not have any further issues.

[Superdave]

Yup, I have slashcuts on my Camaro and the Fiero. They work MINT ! Do it up and you will not have any further issues.

Pics?