pmotts

Brian,

I will look at how my vacuum hoses are routed and get a pic when I get home. I do remember there is a 4 way tee. I think I know where they all go but I better confirm.

pmotts

Well I am not going to be much help, off the brake booster my line Y's with both lines going to the fuel dampners.

BrianG

I was concerned about the vacuum actuators seeing positive pressure(boost) as opposed to only ambient-to-negative (vacuum), because they are certainly designed to see vacuum, but might be damaged by pressure. One definitely doesn't want to have to go digging around in the bowels of the 928 replacing vacuum actuators of various types.... particularly things like the power brake booster!

I decided to consult with Tim Murphy of SuperShark fame, even though he has nothing to do with Andy's orphaned SuperModel project. Ever the gentleman, and champion of everything 928, Tim related that, in his system (being a "blow through" design) every vacuum system in the car sees boost when the engine does. (except for the PCV system, of course, because we wouldn't want to pressurize the crankcase)

Apparently + 1/2 atmosphere of pressure (+7 lb) means little to the vacuum actuators found on this car.

Comments???

Bill Ball

Tim is right - it seems to work OK with boost at times. However, with Andy's set up it can all be hooked up so that the actuators that normally only see vacuum, still do.

I have the fuel dampners, AT module and cruise all taking vacuum of one or another of the throttle body taps. Only the fuel pressure regulator gets vac/boost from tha manifold (except for the separate fitting for the vac/boost gauge). The brake booster vac hose is fed by a fitting at the base of the boost bypass valve. I have the boost bypass valve fed vac from the throttle as well. Note that Andy has this running from a T in the manfold vac/boost line that feeds the fuel pressure regulator. Andy's way does provide faster acting valve and higher very low-end torque (proven by my dyno both ways), but I thought it was contributing to rough idle, so I went off the throttle. Now, swapping it back and forth does not seem to affect idle. Take your pick.

BrianG

Thanks for that, Bill.....
I think I'll go your way with each of the items you listed.

The only question left is about the vacuum taps in the throttle-body. It seems that some might be ahead of the throttle butterfly (timed vacuum signal), but I can't tell which is which. I have 2 open on the bottom and one open on the top, and one OEM-capped on the top.

Anyone know for sure?

Bill Ball

I can't say I understand the difference in the taps. Perhaps study of the 85-6 vacuum diagrams would help answer which should go where.

BrianG

For the time being, I'm going to spider the required vacuum systems off of the brake-booster, and leave the non-critical systems dangle for the initial start-up. That might be a good way to avoid phantom air leaks as I get the idle, and various other initial issues sorted. I'll be able to sample the throttle-body taps when it's idling, too.

Sab

Why would anything change with the vacuum system?
The vacuum gets created by the small venturi pipes in the throttle body and that stays the same.

BrianG

You are right, Sab, I just don't know which is which.............

Rick Carter

I emptied my catch cans for the first time today, about 2 OZ in each after aprox 5 months of driving. I haven't done any track days but will report again after Sharks on the Autobahn. The aluminum cups that replaced the rubber boots of Andy K's kit are fantastic, it looks like DR will be getting right of first refusal on selling them. Rob has come up with another great idea that he will be talking about to DR, I'll keep you posted on that upgrade as well. For those who asked, my SC belt is a CarQuest K060 434, 6ribs aprox 43 inches long and the PS ALT belt is a K060 495, 6 rib aprox 49 inches long. The power steering pulley has 5 grooves but doesn't have a lip so teh 6 rib bel tis OK, my ALT pulley is a 6 rib pulley. The SC idler pulley works better on the "loose" side of the belt.

Bill Ball

This weekend at open road racing I blew a lot of oil. I was boogying at 160-170 for 5-10 miles at a stretch and went 141 for 133 miles (83 of those miles at 145 average). I must have blown out 2 quarts. I started a quart low, thinking that might reduce the problem. At the turnaround I put in a quart and returned it to a quart low. By the end of the race I was another quart low.

ALL of the oil exits from the oil filler breather. The breather from the passenger side cam covers never throws a drop. I have Andy's standard breather configuration.

George Suennen, with a Murph kit, used to blow a quart in 50 miles of racing. This time he said he blew nothing despite speeds up to 190 and a 160 average.

I definitely need to work on this. A catch can obviously isn't enough. How should I change the breather system?

mspiegle

Do you have an oil separator? I believe DR includes them with his kit. A stock 928 has separator-like devices, but that's all been removed on a supermodel kit.

BrianG

I agree with Mike.... We can take a lesson here from the world of piston driven aircraft engines. In that world, engines are run at high power settings, for prolonged periods of time, unlike street-driven automobiles, but quite like race-cars. Also, these aircraft engines tended to have their crank cases vented to atmosphere, rather than having a PCV system.

Our SuperModel systems eliminate the OEM PCV system with the expectation that Andy's "trapped Brillo-pad" tubing system will contain the oil vapour and allow it to condense and then drain back from whence it came. This is probably OK for most street-driven applications, but isn't going to be sufficient for racing application.

The lesson that we can take from the aircraft environment is the air/oil separator. Essentially a sophisticated catch can. Some aircraft units provide a drain-back path to the engine for the condensate, and some just require periodic drainage.

Another really interesting idea is what Tony has devised. Essentially he has built an air-oil separator that fits into the void in the engine block, below the old oil-filler housing. Obviously, this system would provide for it's own drain-back path, being inside the block. I have tried to locate Tony's diagrams, but can't. They are on this forum somewhere. For Tony,it works great, as he says he never sees any oil from that side of his system. I don't think Tony races, though, so YMMV.

The only part of Tony's systen that I find disconcerting, is that, if his separator starts to shed any bits, they will be shed directly into the engine.....

Shane

In preping Helmut for boost I added DRs' Provent Mann breather. It vents to atmosphere and has a drain that I run back to the oil pan. There is a blank cover there on my MY anyway that I drilled and tapped for a 1/4" hose barb.

Mann Provent

Rick Carter

My catch can drainage had a mix of mostly oil with some water.