jwalton

I have the opportunity to buy a 3.8 liter Porsche motorsport engine for my car. Plan to install in a 993 RSR and race in PCA. What can anyone tell me about issues associated with this engine. Reliability,maintainance costs,how many hours until it would typically need a complete rebuild,parts availablity now and in the near future. thanks for your feedback. Jon

Geoffrey

You need to find out exactly what this engine is because there are several different configurations. The engine type should be M64/04 on the case, if it is not, then the engine might be m64/04 specification, but I would argue the value has been decreased due to a non RSR case. All configurations have the same heads, 45mm intake ports and are specific to the RSR intake manifold. Stock 964 or 993 heads are not compatible. The heads come with either 51.5mm intake valves (endurance) or 54mm intake valves (sprint) The sprint heads are known to crack between the intake and exhaust valve seats at low hours approx 30 hours. You'll want to understand if the heads have been cut, and how many times they have been cut. Most of these engines are well used and you may not have any life left on the heads and they are extremely expensive new from Porsche. There are several different pistons, the normal RSR piston with 11.5:1 compression and a sprint piston in the 12.5:1 range. Which does this engine have? Some of the engines came with slide valves, others have the factory ITBs. There were a number of camshafts used over the years including the factory cams, Theilert cams (several different grinds) and someone may have installed yet a different aftermarket camshaft. Has the case been shuffle pinned, windage modifications? What engine management system was used? Typically the stock ECU used black injectors, the Theilert ECU engines used orange 993tt injectors, and the MoTeC ones used the green 944 Turbo injectors. When was it last run? How long was it run for? Does it come with a dyno sheet? Does it have any other documentation?

How much are they asking for, who is selling? It is hard to buy one of these engines complete because they were well used engines and to really understand what you are getting, you need to take it apart.

Personally, I think you can build (and I have) a better performing engine out of a stock core 964 or 993 engine with better reliability.

With the new GT classification, your car will be in GT3R/S unless you add a significant amount of weight and drop to GT4R/S. In my estimation, you'll need a 400hp engine to be competitive.

jwalton

WOW Geoffrey, that is as comprehensive of an explanation I could have hoped for. I will check out the stuff you mention. Do you mind if I communicate back to you on this. Maybe a PM if you think its too individual for this thread? thanks a bunch. Jon

Geoffrey

I don't mind. The thing you want to avoid is paying too much for race junk that won't serve your needs and give you enough rebuild cycles. Not all RSR engines are like this, but there are enough out there that you need to be knowledgable about what you are buying.

jwalton

I agree, I have had my share of mistakes buying stuff before thinking through it completely and I pledge to do this no more. Here is some of the info from the seller:
"Some of this I can answer and some I can’t. I’ll have to inspect the engine for stampings. The engine is new never rebuilt from Porsche Motorsports. It was a spare motor from when Porsche and Alex Job racing were joined for the endurance racing. It is the sprint motor. The big valves, crack prone heads and so on. In defense of that though, when I talked to the engineers at Alex Job they said that if you clipped the RPM’s by 500 is should be an easy 50 hours motor. They only ran them about ten hours and shipped them back but they ran them as hard as possible. There are no dyno sheets as all of that work was done by PMNA and they didn’t share, Even with Alex Job, no kidding. The special sauce Alex Job added was the MOTEC programming and this is a MOTEC M48 set up and I have the files from them for this motor. Alex Job did virtually no work on the motors other than installation and the programming. If there was a problem a new one was inserted and the motor with and issue sent back to PMNA. The GT1 block should go a long time."

Geoffrey....Let me know if you think we should take this private Thanks jon

Geoffrey

I did the wiring and MoTeC work on the ex Alex Job #069 RSR (it might have been #067, I get the two confused) for a customer last year so I am familiar with that engine. Is it the exact same configuration as the #069/067 engines? Those engines ran with both slide valves and ITBs depending on where in the development cycle they were and whether or not they were Sprint or Endurance racing. The engine programming and injector selection were not correct on this car, but it was club raced by someone after Alex Job sold it, so it might not have been the programming done by Alex Job. The engine did make 350whp (about 412) and was the most powerful factory RSR engine I have done to date. It is an 8000rpm capabile engine and we set the rev limiter at 7650 which left some power on the table. If it is the same engine configuration, then it should produce the similar power. Does it come complete from intake to exhaust?

Alex Job did the MoTeC programming and also utilized the traction control capability of the MoTeC ECU, so you better believe they knew exactly what the HP was on those engines.

M_Weining

Any feel for how a 2310lb (with driver & fuel) 993RSR type car with an engine like this might do in the new PCA GT class? Assuming good PCA racer driving skills and suspension and fresh tires. If I did my calcs correctly it would fall into GT3 (2310*100)/(3.8*110) = 552.3.

Are there other motors that would be closer to assumed Hp/liter number that PCA has based the rules on. If so, what?

Mark

Geoffrey

Actually the performance index would be 561 because a 102x76.4 engine is 3746cc, not 3.8l as commonly referred to. Since you mention the car is 2310 w/ driver, I am assuming an early chassis because it is extremly hard to get a 964/993 chassis that light. I think that, although the chassis lighter, the later suspension might make for a better car. However, in my opinion, your car would be at the top of the GT3 class and compete for class winner. The closest non 911 competitor would be a 2.5l 944 turbo running at 2800 lbs and I think that would not be competitive in that class. and possibly a 2.1l 911 turbo at 2500lbs.

So, I think that your car would be competitive with the slightly heaver, but better handling 964/993 cars. Although, if you installed a 4.0l engine in a 964 chassis you would decrease the performance index to around 560 and potentially have an advantage on both HP and handling which would overcome the weight. This is my current thinking.

M_Weining

Geoffrey, thank you for the great input. With the new GT classing system It will be very interesting to see what cars end up in what classes and how they do.

jwalton

Geoffrey, If the body panels were carbon fiber and the original tub was a 1970 vintage would that make sense for the weight question? Jon

Geoffrey

I'm looking forward to the Sebring club race where the new rules will take effect. The Scruts will be busy. It was time for a change, and I'm interested to see what the "it car" will be for the classes.

The early tubs can be made extremely light and depending on the equipment (5spd mag case or 5spd aluminum case, 6spd, etc.) you could end up with a very light car. Combined with the nicest suspension available, it makes for a great car. My experience cutting up the various tubs shows that the later 964/993 tubs are reinforced quite a bit which is one of the reasons the tub itself is heavier. I think the geometry improvements of the later tub make for a better handling car, but the trade off is weight. You can build a 1900-2000lbs 3.4l car out of an early tub, but you need to be Kelly Moss with $250k to build a 964/993 under 2100lbs.

The normal wet layup carbon fibre panles weigh the same as the fibreglass panels so there isn't a weight savings there. It isn't until you get the better CF parts that have been autoclaved do you get the weight savings.