dime1622

I met with a mechanic today to discuss options regarding my upcoming engine rebuild. I'm trying to figure out everything I want to accomplish while it's being done. My goal right now isn't to build any sort of horsepower monster. I'm trying to get the motor solid before I think about upgrading the turbo. My mechanic has several long blocks sitting around so he'll just rebuild one of those until it's time to pull the old and drop in the new. He's also built a lot of 944 spec cars, so I'm pretty confident that he'll be good to deal with. Because I'm not building the motor that's in the car now, I can take all the time I want and make sure I do things RIGHT. The stuff I'm looking at now, aside the usual new waterpump/new hardware/clean everything/new piston rings/yadda yadda are:

- Nylon crank scraper
- Oil pan baffles
- 3-piece crossover
- O-ring the head

What else do you suggest I do during my rebuild? I'm planning on running a Vitesse stage 3 or similar sometime next year (2008). I want this motor to be BULLETPROOF. How about a bigger oil cooler?

Naplesguy06

well this is my plan - OLD SCHOOL AND PROVEN. First, get a 2.8 liter stroker crank, wastes little time in any gear, Blueprint the motor, smooth polish the intake and exaust ports, get a cam from a normally aspirated 944, get 100mm Mahle pistons, custom built with the special wristpin location to ensure clearance from the valves and head, increasing compression to 8.5. Carillo rods,Suspension to handle it all. Get some sway bar from the escort series, 4 corner balance the car, the goal here is to Eliminate turbo lag and this amount of displacement and stroke should do it. Right now on Ebay you can find a Magnesium intake from Porsche, hasnt been made in 10 years (part#951 110 152 04) magnesium oil pan (#944 101 204 01) after all this play around with your Turbo, chips, wastegates, housings, etc.

Ski

It's a 3.0L crank and I wouldn't touch the ceramic liners on the exhaust ports. The problem with the Mahle 2.8L pistons in 100mm is finding a block that's not egg shaped with age and gravity that you don't have to rebore/finish. Finding Mahle 8V 100.5 2.8L pistons is damn near impossible. HMR has Mahle make a 16v version.

I see a lot of these build threads and I don't see anyone mention about checking the cylinders for actually being straight and true - that would be my first step to see if you need to bore and get oversize pistons, then finding a good machine shop that's familiar with the Alusil refinishing process; otherwise your starting with a band aid.

333pg333

What about sleeving?

Ski

Chris Whites MID sleeves are a great thing and great success, he worked hard with those people to get it right. The other stories about sleeving that I've seen, prior to MID developement, have ended badly but I'm sure they're success stories out there.

RKD in OKC

I am currently in-process of rebuilding my 89 turbo motor, well...Lindsey Racing is doing it. BUT, my goal is bulletproof more than peak HP. The motor was 2.5L with pauter rods, nikasil cylinders, coated stock pistons, o-ringed head, and knife edge crank, 89 pan scraper, no pan baffle.

When I orginally got the car it had 10,000 miles on the rebuild, and a wet K27/8 turbo. With the stock wastegate and MBC it was basically free boosting, ie. 21psi as the turbo hit and dropping linearly to about 17psi a red line. The only problems with the car was that is was running lean on partial throttle acceleration and getting realatively high EGT peaks, over 1650°F. WOT throttle runs it was right on both AFR and EGTs.

I added a few things to the car to try to get the tune more under control; dual port wastegate, injectors, adj fuel pressure regulator, Mafterburner. While all this helped I was still a little disappointed with the 17psi max boost by red line so swapped K27/8 for a Super61. While the Super61 helped make a lot more power and my afr and temps were now under control, I had decided to install the turbo dry. At every Autocross even after this install I had problems with my oil getting hot and low pressure at idle after 3 runs close together.

This was what would be described as a bulletproof motor and I started hearing the slight knock that brought about the rebuild.

Now for the interesting part...the fornesics after 20,000 miles.

First discovery was worn enough to knock at idle, but not spun #4 rod and rear main bearings. Crank in great shape. On later inspection the wear on the bearings looked to be some sort of Hard foreign object coming out of oil hole in crank. Best guess was there was some thing not cleaned out of the crank when it was machined before it was installed and it took some time for it to dislodge and do the damage. The good think was no damage to crank so it could be re-used.

The next discovery was a chunk out of the #4 cylinder wall Nikasil at the top of the bore and coresponding gouge down the side of the piston. Rings still looked good. Closer inspection of the other cylinders showed some slight scratching where a similar chunk could happen any time. It was found that the previous owner had used stock chrome rings with Nickasil cylinders. I understand that is an 18K to 20K combination before the chrome rings start taking chunks of Nikasil off the cylinder walls.

The decision was made to bore and hone to 100.5 to remove the Nikasil and line bore the girdle. The girdle was deformed from pre-detonation, but the block did not need decking. The shop has the equipment to make sure everything is straight, and true and does Alusil.

After receiving the pre-detonation warning from the machine shop the wrist pins were checked an found deformed from .001" to .00075". Another effect of pre-detonation.

The rods are out being checked to make sure they are still straight and true after the other pre-detonation caused problems were found. I haven't heard about them yet, but we are hoping for a good report.

While I am not specifically a mechanic or engineer, I am a very good problem solver in any field and here is my diagnosis. The bearing problem while specific damage was done by the foreign object, I feel was brought on by the higher oil temps brought on by the dry turbo. The higher temps probably loosened a bit of drill chip from cross driling that didn't clean out before assembly. The deformed girdle and wrist pins were most likely due to both the previous owner running the K27/8 wide open without proper tuning and the harsh treatment done while trying to get the good tune that was finally achieved.

Now with all that behind me how does that effect my rebuild and bulletproofing?

Things that are basically staying the same...
Pauter rods - stock length
Coated Pistons
Raceware fasteners
O-ringed Head

Things I am changing/adding
3.0L crank
pan baffle
8.5:1 pistons, coated, for stock length rods
Super61 Turbo - going wet.
KISS oil cooler

The way I see it I had two problems. One was pre-detonation effecting the wrist pins and crank girdle, the other the oil overheating. I am not reallly counting the foreign matter and the bearings except that I feel it was aggrivated by the high oil temps.

I am going with 2.8L stroker not just for more power, but also more power with less boost and therefore less pre-detonation issues. LR has been talking about larger wrist pins to make them more bulletproof, but I don't know of any solution to make the crank girdle any stronger. So, the plan is to set the car up for 18psi of max. boost. I am thinking a 2.8L with 18psi will be as much power as the rear wheels can realistically get to the ground yet be low enough boost that pre-detonation is not an issue. I've seen a 2.8L with a smaller turbo that made 450rwhp at 18psi.

I am hoping to solve the oil overheat issues by both adding water coolling back to the turbo and adding an extra oil cooler. I am also rebuilding the oil thermostat and cleaning the stock oil cooler and all the lines to make sure they are not gooked up after the oil got so hot.

So there you have it. What happened to a car that was called bulletproof and what is going to be done to increase the dependability without sacrificing the enjoyment of ....more power

Ski

I understand your concern over the dry turbo issue but honestly I don't think the small amount of oil going through the turbo is going to heat up the whole system that much to cause and oil related failure. The reason I say that is because on the track car, dry Kokeln V, we have the oil temp probe drilled and tapped into the banjo bolt off the turbo oil return. That sender sees about 25-40° degrees more(depending on ambient temps) than what's going INTO the first cooler from the oil cooler housing, and that sender is reporting back, so far, that the max has been 275-280°, so the oil from the engine going to the first cooler is about 250-260° on average, as we've shot this with a laser temp gun.

I think keeping your cooling system in great shape is just as important with regards to oil cooling as twin coolers are if you're going to track the car or drive the hell out of it. I know a lot of track cars close off the back head port that went to the heater valve, we did not. We hosed that back to the hard line and fed it back to the pump. This does two things IMHO; it keeps the water moving at the back of the head around #4 and gives you another continuous feed out of the head for a bit more flow. That particular hose, should you choose to do that, is also an excellent place to put a tee and place an extra water temp sensor there. The flow is small, but it does work and that feed back to the water pump still helps pull some heat out of the system.

RKD in OKC

Ski - I am also considering seeing if I can get the turbo turbine thermal coated.

Ski

LR's guy going to reassemble it after that? The Kokeln V on the track car is one that he rebuilt and man, it has been great; that guy does good work.

RKD in OKC

At this point I don't know if I can get them to do it, but I would hope so.

tconn

My experience has been that the engine runs much hotter Autox-ing than
during a DE.
At a typical Autox your running the engine hard but have less airflow for shorter
periods of time and therefore less cooling than a typical DE event. A cool down
lap at the Autox consists of idleing back to the start grid.
I've just installed an oil temp sensor so it will be interesting to compare temps
between Autox and DE runs.