johntorg

Hot oil pressure is around 50 lbs. I will do a compression test and leakdown test today and report back. I will also check for new leaks. The confusing thing for me is that it isn't really smoking very much. I'll also check the oil level after the enduro.

BTW, here's is a video of the opening laps of the enduro.


http://www.youtube.com/watch?v=c_9deQ3_SnQ

Matt Romanowski

I've seen motors consume enough oil to put them down over 50 hp and not smoke much.

M758

It can be the valve stem seals. I replaced these on my 944 Turbo when it used alot of oil at the track. I helped alot. Using compressed air replaced these with the head on the car. I have never had that issue with my 944 NA race motors, but I useally have the head work done by shop so I am sure that gets addressed.

mark kibort

probably rings. I think its not uncommon for a race car to require a 1/2 a quart every 15 to 20 laps. so, when you posted 109 laps, thats like 3 -4 weekends of racing. at that level of oil use, it possibly could be valve guides, but then you would have some black plugs and lots of smoke on every decel. (where the oil gets sucked in through the guides if there is a leak) otherwise, its oil control around the rings as was said.

johntorg

The horsepower is 147 with torque of 148 and the car pulled most other 944 NAs on the straights at Sebring. I asked the PO exactly what head work was done. It was done by a reliable shop. I can't find the invoice right now.

johntorg

I checked the throttle body and boot. There was no oil in either one. So unless its going somewhere else, blow by doesn't seem to be the issue. I guess it the compression rings are good, oil could be going by the oil rings and burning in the combustion chambers. I'll run compression and leakdown tests tomorrow, as well as looking for new leaks. In the 90 minute enduro the engine burned a little over 2 quarts of oil.

FrankyV

John, enjoyed the video and racing with you- you and I were dicing it up good out there.

MUSSBERGER

The rest of the car seems pretty good

johntorg

Frank, the whole weekend was great and it was a lot of fun racing with you and the other D class 911s. I can send you a DVD of the first 13 laps of the enduro, if you PM your address. Did you get any video of my car?

Other than the oil consumption and a spongy brake pedal, the car ran great all weekend.

johntorg

OK, the mystery is a mystery no more. I did a compression check: Cylinders 1,3,4 190-200 Lbs, Cylinder 2 175 lbs.

I also did a Leakdown test Cylinders 1,3,4 3-5% Cylinder 2 18%

So it looks like a problem in cylinder 2. I could hear the air escaping through the rings through the oil filler on that cylinder only. I injected some oil into cylinder 2 and got 220 lbs compression, so its definitely rings. Sounds like maybe a weak or broken oil ring or bad bore.

I will run the engine in the NASA Sprint races at CMP this weekend and then reseal my race engine, install new rod bearings and a new clutch and put it back in the race car, hopefully in time for the March 11 NASA races at Road Atlanta

Droops83

Glad you figured out the problem. Well, of course rings are a bit more of a job to deal with than valve guides but it sounds like you have a few engines/cars to choose from to get around the problem for now!

Your compression/leakdown numbers are a classic example of how much more meaningful a leakdown test usually is than merely a compression check. The 175 on cylinder 2 is not that much lower than the others, but the leakdown test told the tale. It is no wonder that the engine wasn't using much oil on the street (yet) but did under constant heavy load on the track (the opposite of my daily driver/time trial 951).

BTW awesome video of the race, that looks like a hell of a lot of fun. I can't wait to get my race license! The long straight and then the last turn leading to the front straight at Sebring looks pretty fun.

f1rocks

John was that you or the kid on the video....you found 7 seconds from earlier in the weekend!

johntorg

That was Matt, my enduro co-driver. The battery ran out shortly after our pit stop. He blew his clutch in the 2nd sprint race, so I invited him to co-drive with me. I actually found 6 seconds and he found one more on a single lap. He is younger, braver, lighter and probably more talented than I am. It was my 2nd time at Sebring and his first. So you can teach an old dog new tricks, it just takes us a little longer.

In the early sessions I was running on old Hoosiers. In the races the Hoosiers were new fronts and almost new rears, I also switched to 275/35/15s on 15X9" rims.

f1rocks

Hoosier Hero's.....we need to throw you out on my ratty old Toyo 888's....

Can't wait to finally burn those up at Nashville in a few weeks and be rid of them forever.

IcemanG17

It appears cylinder 2 is the problem.....while the compression is still okay, the leakdown is the issue....so its either a valve sealing problem or rings...my guess is the rings themselves are fine...but there might be a scratch in the bore causing the leak....fairly common in 928's too....