bigmac

Andrew, good luck. Your friends in AA are looking forward to a ride to break-in your new 18 inch skins.

AO

Sorry, too late. Before all this, my rigth foot slipped when I was in 1st and I accidetally laid down about 200 feet of rubber. How clumsy of me.

Fabio421

Why couldn't you use a large diameter, low spring pressure, ball bearing check valve. The crank case pressure would keep the check closed while the engine is running, but allow the oil to drain back to the case upon shutdown. This would eliminate the need for any pump that could fail, and wouldn't weigh neerly as much either. It would also eliminate the need for another electrical circuit that could draw the elec. system down. My company uses a similar setup to deliver fuel to a gas driven fuel pump. Head pressure is enough to overcome the spring in between compression cycles. During this period, fuel flows freely to the fuel pump. Once the fuel pump starts to stroke, pressure is sent in the opposite direction and this seals the check valve. I do not have one of DR's SC kits so maybe there is a reason that this wouldn't work. I'm just throwing an idea out there. Brain storming is a good way to reach a solution most of the time.

blown 87

That might work, but you really do not want any crank case pressure.

I plan to run my AIR pump (not the pump that came with the car, but you get the idea) as a vacum pump on the crankcase to make sure there is negative pressure at all times when the motor is running, with the outlet going to the catch can.
This should also help with ring seal and be worth a few HP.
Some of the drag race guys are getting 5-10 extra HP out of negitive crankcase pressure.

I have never liked the way that most modern engines use the intake to take care of crankcase vapors. This causes all kinds of problems, from sludge in the throttle bodys to clogging the egr passageways and more.

There has to be a better way, and I think with all of the smart guys we have here we can come up with something.

Flott Leben

Putting pollution concerns aside for now, we want to vent the pressure in the crankcase. We just don't want to vent oil as well. Or if we vent oil with the pressurized air from the crankcase, we want to collect that oil and return it to the crankcase while the engine is running, especially at full throttle. You either stop the oil from vaporizing and venting with the crankcase air (unlikely) or you collect the oil vapor, condense it to a liquid and return it to the crankcase. If the crankcase pressure is 0 or negative, a gravity feed will work. But if the pressure is anything but those levels, the oil needs to be forced (or sucked) back into the crankcase.

Has anyone thought about tapping into the oil cooler lines to return the liquid oil? Those lines run into (not out of) the oil pan, right?

marton

Hi Andrew,

Only 200ft? Did you miss your gear change?

Marton

blown 87

I think it would be better to have it go back into the pan or into the oil filler neck, less pressure there and if you have a line break it would not lead to a major problem.
External oil cooler lines are a necessity, but man if one gets a hole chaffed in it there is going to be oil everywhere.

Fabio421

Please re-read my post. The oil would return to the system after you shut down the engine. That is when the crankcase pressure would return to zero.

Running an additional pump will help but it will rob you of HP. I used to run a crankcase evacuation system on a drag car and a street car in the past. You can use venturi from the exhaust to draw a vacume from the crankcase. This has no HP penalty and it weighs less. The biggest problem with the 928 engines ingesting oil is due to windage. The crank draws the oil up into it and whips it up. This also causes HP loss and creats additional heat. There is a windage tray and crank scraper on the market. It was designed by a company in Tampa and is sold through Carl at 928 Motorsports. The true solution is dry sumping I would assume. But that aint cheap.

blown 87

I have known some of the drag guys that swear they are getting more HP with a vacuum pump on the crank.
You could be right, as I have no data to back me up here.

Crankshaft windage is a real problem, not only from the heat and HP loss but also of the problem of getting aerated
oil.

Yes a dry sump would solve many problems.

FlyingDog

When looking for dry sump info a year or two ago, I found a site with data on crankcase pressure and HP. They routed breather and oil lines on a dry sumped engine in different ways to get positive pressure, near neutral pressure, and vacuum. HP increased with each reduction in crankcase pressure. IIRC the test car was a Japanese sport compact (Nissan?) and the site was British if you want to search for it.

Louie928

Bill,
I promised myself I wouldn't get into this same discussion again, but I can't help myself. ALL (caps intended) of the oil control issues have the common component of the impossibly small crankcase venting of the stock system causing crankcase pressure. Then mods such as Andy's SC with the cover plate with the same tiny vents don't do anything to help it while close to doubling the blowby volume. There is room in the void under the oil filler plate (over the crankshaft) for a preliminary oil separator while giving the opportunity for a large vent line. By large, I mean 1" diameter or larger. Tony Harkin has some pics on his web site of an example of his version of the fix. Start with that and it will minimize oil loss. Then other remidies to take care of the smaller amount of oil are a lot easier. If you have oil coming from your cam cover vents, the problem is too much pressure in the crankcase. Fix that first. The SC engines will make ~8 cu ft/min of blowby. It has to be vented with low restriction or it'll go up the cyl head drainback passages and carry a lot of oil with it out the cam cover vents. The oil that gets blown up the drainback passages from the crankcase is very frothy/foamy. More so on the right side due to crankshaft rotation.

scott863

Wow, I watched your 0-60 movie, it looks like from the time you launched to 60 was about 4.? seconds !! What type of charger do you run? What psi are you running?

AO

Louis-

That's good information. If the new plate doesn't work, I'll investigate a setup ala-Tony. The new plate from DR, however, does have a larger diameter tube, so it should be free-er flowing.

Scott, not sure if this was directed to me or not. If it was, I'm running the kit offered by 928 Specialists (www.928gt.com). My best 0-60 has been 4.3, but I think I can do better once it warms up.

69gaugeman

And everything is back on


















correctly


























with no spare parts






















or worse yet missing parts

AO

Tru... Tru.