'97 C5

Anyone successfully used a vaccum pump to evacuate the crankcase and pull rings to the bore? I can use the air pump but it only pulls ~4.5" - not enough to really gain the HP that is available.

But, there are a few 12 volt dc vacuum pumps available that are used to supply vaccum to the brake booster on EV cars and they typicall pull 650 mbar / ~17" hg.

Any pioneers out here or am I pn my own?

THanks

NEPTUNEBILL

Talk to Patrick at Vararam he has the exact setup and quoted me the same numbers yesterday in a phone conversation--this is something I intend to do as well----

Lil Red

Can someone please elaborate and explain (in lemans terms) the theory/principle on how this is supposed to work?

Mag Red Monster

:confused: Care to explain " Pull rings to the bore" for the uninitiated????

Mike Mercury

is this the setup where the vacuum pump runs as the engine runs.... a permanent installation?

YOULLUZ

You can also accomplish this using a one way check valve in the header and using the exhaust gasses to pull out the extra crankcase pressure.. It's used widely on dragsters.. Take a look next time your at the track.

jmX

I did the exact same thing 2 years ago on my LS1.

On the dyno, I switched it on and off a few times. It was worth exactly 0.0 rwhp every time.

Mike Mercury

How can that be? I read about this in a tuner type magazine and they wouldn't have stated the HP gains unless it was true.

:lol:

'97 C5

So, what was you set up...because that's not right at all. I've pulled 12 HP at the crank on stocker (engine dyno) with only 12" hg...

Clearly something is just wrong with your set up. Here's a few issues that would preclude or negate any gains ...

1) you didn't maintain enough vacuum
2) your cylinder walls are glazed
3) the rings are minimal
4) the piston to wall clearence is whacked
5) the VE changed but you didn't tune for it

'97 C5

It's not about tuner magazines it's about the power it gains. If you don't understand the science maybe best not to comment. Sorry to be blunt but I am not going to be the butt of anyone's stupid comments.

'97 C5

I've done headers a few years back and it's fine but not as workable as an elctric pump would be due to varying loads and subsequent drop values.

'97 C5

The set up is a continous duty pump and it runs as long as the engine is running.

jmX

My setup pulled 15" of vacuum, the pump ran whenever the engine was on. It could not keep up with the pressure buildup, and by redline, it was at zero vacuum.

Even in the midranges when there was still plenty of vacuum, there was no torque increase at all. It was because of that finding that I did not pursue a dual electric pump method so that it'd maintain vacuum even at redline. This was the same electric pump that people have been using for years on various other GM cars for crankcase evac. There is nothing new here.

'97 C5

I'd like to hear the actual details because If you could pull 15"hg and then lost it beyond a certain RPM, you had other issues.

Please tell me a few deatails like:

1) Pump P/N or years of cars used (if it's the late model Caddy unit don't worry, it's not capable and I have the P/N)
2) Where did you mount the vaccum gage and how did you determine that you were sealed
3) Where did you pull vaccum (inlet) and what size tubing did you use
4) Where id you vent and did you ever "pull oil"
5) What tubing did you use

If you let me know I bet we can find out why your application failed.

NEPTUNEBILL

Just a thought but doesn't the additional seal of the rings also create a lot more friction that may nullify any gain accomplished by the greater seal of the rings--

Mike Mercury

to quote a funny movie: lighten up; Francis.

jmX

1) Don't have the part #, but it is the one lots of LT1 guys have been using over the past 5 years
2) Vacuum guage was tapped into a crossover pipe between the valve covers in the rear.
3) Vacuum was pulled from the fresh air inlet port on the front of the passenger side valve cover
4) it was probably 3/8" ID, and yes, it would pull oil depending on how I drove the car
5) I at first used some silicon thick walled vacuum hose, before I found out that was not rated to hold oil (it'd seep through). I then switched so some thicker black hose that didnt seep.

The vacuum would be at 15" at cruise, idle, daily driving, as soon as I floored it, the vacuum would decrease slooooowly and by 6500rpms it was at 0 and would actually start building a tiny bit of crankcase boost. I assumed this was from the infamous LS1 ring sealing issue.

A few other LS1's had the same issue, and if I were to do it all over again, I would use a belt driven pump, two electric pumps, or just fix the rings.

Either way, in the mid ranges when I still had 10" of vacuum, there was NO difference on the dyno. The lines actually covered each other up on the printout, they were so close to being the exact same.


[Modified by jmX, 8:48 PM 10/23/2003]

Mike Mercury

do you understand that scientific theories... many times... never pan out in the real world?

BTW, don't you need dykes rings to take full advantage of negative pressure? Does your setup have dykes rings?

TLKSCHP

:crazy: :confused: :crazy: I want all the tips I can get on more HP's but you guys are way beyond me. Good luck, and maybe I will be able to understand this some day. But it does make for good reading. :thumbs:

Tony M

Hello....

I've been around quite a few dyno tests over the years and I can say with a reasonable level of confidence that a vacuum pump will almost always show some sort of power gains....of course some more than others. This assumes that the vacuum pump (electric or mechanical) can produce and sustain at least 8-10"hg @ wide open throttle. More vacuum is even better....usually in the low teens. The reason it helps produce HP is mainly due to better ring seal with a vacuum condition present in the crankcase....ring flutter should be down....ring seal should be up (with a corresponding bump in power as well).
Also, bigger power gains can be had with a vacuum pump because as an engine builder, you now have the ability to run lower tension rings, and/or thinner rings as well. You are able do so because the vacuum pump will be aiding ring seal due to the removal of excessive crankcase pressure that might have normally unseated the lower tension rings and caused compression and power loss. I have seen identical 800-900HP engines gain a solid 25+ HP due to the reduced piston ring friction and the vacuum in the crankcase....Now that figure would be reduced in a smaller less powerful engine, however it would still be something you could certainly see on the dyno as well as your ET slip.

Also, a word about header evac tubes....they don't hold a candle to a vacuum pump in probable power gains as they only generate 1-3'hg in a best case scenario.....certainly better than pressure built up in the crankcase, but not a scenario that warrants big power gains.....also, trying to run an evac tube to a header that is not open (one with an exhaust system behind it), is almost worthless, as the airspeed exiting the collector is not fast enough to pull a significant amout of air behind it out of the crankcase. The mufflers and pipes behind the collector slow the airspeed down enough to greatly reduce the operating efficiency of the evacuation tube going to your valvecovers/crankcase.

This is my "two cents" on the subject, mainly based on things I've read and situations I've witnessed. Certainly adds more fuel to the big "vacuum pump debate"....

Regards,
Tony Mamo