Engine hours on RSR sprint engine

[pranqster]

I currently have an RSR sprint engine in my 2002 Cup Car. It was put in by the original owner. Porsche motorsports recommends a rebuild for this engine every 30 to 35 hours.

By my estimation the engine has not quite 45 hours on it. It has been raced only 8 of those hours. I have not had a mechanical overev in the car and the other two owners have told me they did not have any mechanical overevs either.

My query is two fold.

First, does anyone have any knowledge of running a sprint engine to 60 hours or more?

Second, can anyone discuss the merits of a 3.6, 3.8, 4.0 sprint engine versus a 3 ring 3.8 cup engine?

Thank you in advance for the answers.

[Skypalace]

I don't have specific knowledge of the sprint engine per se, but the Motorsports recommendations are basically for full-on pro racing, I think they can be relaxed if you're not running as hard.

I went over 120 race hours on my 2004 Cup, and had virtually zero leakdown (3% max), finally had PMNA do a rebuild as I was getting worried about hours. PMNA said they'd never seen as clean a high-hour engine, and to keep doing whatever I was doing. Unfortunately (I guess :-)) the new engine wasn't any stronger than the old one, I was hoping to pick up a little speed :-)

My secrets were: Regular Mobil 0-40w oil changes, warm up the engine before fully revving (I'd warm up in pregrid to 170+ before hitting the track, then do a warmup lap), always do a cooldown lap, and the big one, never miss a shift! Overrevs are of course harder on the engine than anything else. Having full data that's automatically logging all engine behavior is very helpful here.

On the other hand, I've seen plenty of lower hours engines in poor shape.

I'd let leakdowns and analysis of overruns give you the news. If leakdown is good but you're not 100% sure about overruns, it would be a lot cheaper to have the heads pulled and have someone look at the valvetrain etc., than to do a full rebuild.

Re merits of various engines, what is your usage, and what are your goals? Hard to answer without knowing more about what's important and not important to you. Max power? Competitive running in a spec class? Resale? Lowest overall cost? Lowest cost per hour? etc. etc. My personal answer would be to run a stock 3.6 cup motor, as I like running a spec class and a stock Cup car will keep reasonable resale, but that's just me and everyone has their ownd desires and goals etc.

[pranqster]

Sky

Thank you for the reply.

Because of the sprint engine and a host of other modifications that were completed before I purchased, I believe it would run in the unlimited PCA class. I am still aquiring seat time, and thus far have not raced it. I like the car and would not plan on selling it if I did a rebuild. I do not necesarily care about the lowest cost per hour, but care more about fun per hour. I have been spoiled with the current engine, but the car is and would remain much more capable than the driver (me) for at least another 20 to 25 hours. Under the lowest cost scenario the 3.6 cup motor would definately be the way to go, but I may need to change out the ECU if I go that route. I think the 3.6 sprint engine is around 15k more than the 3.6 cup engine.

[Thusly]

Tim,

Go with a 3.8 cup build. An rsr engine isn't a cup motor, and you are playing with fire trying to rationalize how long you can go. Btw - the 3.8 cup likely has the same hp as the rsr engine with restrictors.

I haven't tried my 4 liter 997 GT3 RSR motor yet, fresh from PMNA - I am sure it is a monster, but the conversion costs alone from a 3.8 rsr motor was close to $80k.

Best,

F

[pranqster]

Fred

Thank you for your reply. From what I have discovered thus far, the 3.8 cup engine might allow me as much as twice the hours as the sprint motor with similar horsepower. Not sure of the torque though.