Track report:
Went to Pocono this weekend. Took the car out on the track Sat morning. I took it easy and kept the revs down, after all, it is a new engine. Car really goes pretty well, but after about 15 minutes, it started running like crap, and was oil smoking out the tailpipe very badly. I believe that the turbo is getting way too much oil feed, has bad seals, and just fills the turbine up with oil. So, I get smoke and killer back pressure. I parked it for the rest of the weekend, except for five laps of the South couse in the afternoon. Gotta relearn how to use the throttle in the turns.

Couldn't dyno the car, as the A/F was at 13-14:1, and never dropped. I tweaked the WUR and got the control pressure down in the 11's:1 range. I really need a supplemental enrichment.

However, the car drove home just fine, and works well in street service; ie, occasional boost. Not good enough to suit my purposes.

Pat

You do have a 1/8p oil restrictor on the supply line right? That line can be -4 but you need to go AN -4 to 1/8p.

I'll pull it off tomorrow. I'm pretty sure the connection is a 1/4 pipe. It's a pretty big line. I am thinking I'll put a 1/4 nipple and full port ball valve with a tee for a pressure gauge, and throttle the flow down with the ball valve.

Does my back pressure theory make any sense?


Pat

I don't know about back pressure but a 1/4 oil feed is way too big. Keep it simple and get the 1/8p. With a ball valve, sure its adjustable but it's not like you can tell where it's set at. Burning out all that oil in there will take a lot of miles.

So, I have evrything sorted down to three problems:

Oil return for the turbo...getting an electric scavenge pump to pump back to the cam cover.

Fuel enrichment...getting a modded 930 WUR.

Runs great cold, sounds like a lawn tractor warm....this is very disturbing. It has gotten progressively worse. I am pretty sure that #6 cylinder head has become loose. I'm going out to do a compression test in a minute while it's warm. I used the black 993 head studs, but I think (hope) this is just a retorque issue. The engine becomes seriously down on power when the oil temps get to operating temp. I am not looking forward to pulling the engine back out.

Sometimes experimental stuff doesn't really go so smoothly.

Pat

Good luck. Lets hope you can just retorque with the engine in the car. I bet you can. But holy crap.

Holy crap is an understatement. On the bright side, I sure am gaining a lot of experience in this application. Conversely, looks like we'll be bringing the 968 to Watkins Glen this weekend.

It's not all bad. When my porsche is down, thats it. No more porsche till it's fixed.

#1 160
#2 160
#3 160
#4 150
#5 135
#6 130

Sounds like a lawn mower on the back right side. Leaking oil onto the rear of the right side heat exchanger. Hmmmmm.

Plugs are good, good color, no shrapnel damage. Hmmmm.

I don't know what the compression pressures should be, but it is the stock 78 3.0, rebuilt with 700 Km on it, CIS pistons (somewhere around 8.3:1, IIRC) Boost at 5 PSI

I wish it was so easy.

Make sure you study the control pressure temperature charts in Bentley Fuel Injection 240 for your year SC. Different WURs have different charts.

There are four separate p/ns 1978, 1979, 1980 and 1981-83 for the SC.

I have no idea what a 930 WUR chart looks like or if they are the same year for year with the SC. at least for 78 and 79 maybe they are. I guess not for 80 and later.

With the wrong WUR you may wack your control pressure curve throughout the range.

I did see the post and the idea is sound but it seems 25 years ago we would have just swapped WURs and I'm certain we didn't.

The ugliness continues here