HP, how much can a LIL 2.5L take? How do they Blow?

[Gary in BR]

I second Bruce...An engine swap is a good option, you get about the same power as you do with a turbo or supercharger.

Sc and Turbo will run around 7k
An engine swap runs around 15k last time I looked into it a year ago.

[porsche986spyder]

If you go to a 3.2 or 3.4 ltr engine swap, do you also have to change out the trans or gear box for a 6 speed if you only have the base 5 speed? Sounds like even more money is needed.

[Gary in BR]

From my research the 5speed tranny can handle the 3.4 upgrade without any modifications.

[Topless]

Unlike Honda, Nissan, Ford, and Chevy a 2.5L 986 doesn't make a very good platform for hot rodding. At 80hp per liter there is not much left in there without driving reliability over a cliff. Most of the guys who supercharged them promptly removed the SC, quickly sold the car, or quickly blew them up. Heat and cylinder pressure are the enemy.

I will drive mine until the motor gives out and then quietly drop in a 3.8L X51. As it is I can still get into plenty of trouble with 201hp.

[pk2]

Originally Posted by Topless

Unlike Honda, Nissan, Ford, and Chevy a 2.5L 986 doesn't make a very good platform for hot rodding. At 80hp per liter there is not much left in there without driving reliability over a cliff. Most of the guys who supercharged them promptly removed the SC, quickly sold the car, or quickly blew them up. Heat and cylinder pressure are the enemy.

I will drive mine until the motor gives out and then quietly drop in a 3.8L X51. As it is I can still get into plenty of trouble with 201hp.

Your thoughts are intuitive and make sense. Mine aren’t & don’t, I guess. But, are you saying Nissan and Hondas, etc. have much lower hp per liter and with lots of tweaking would max out at 80 hp per liter too? Or (god forbid), are you saying they’re stronger motors?

What do you see as the negative effect of more cylinder pressure, rods, rod bearings, the crank? What’s going to break as opposed to wear out faster?

I’ve heard lot’s of anecdotal stuff about them blowing up to, never met someone who had that experience though. Whereas I’ve also heard and met many who drove/drive them uneventfully for years, probably much harder & more often than I do.

Rationally I agree & understand most of what you say but dam it’s fun. can’t see someone going back even if thy knew better.

Regards, PK

[Gary in BR]

Originally Posted by pk2

Rationally I agree & understand most of what you say but dam it’s fun. can’t see someone going back even if thy knew better.

I AGREE 100%

[Topless]

PK2,

Yes, In a word I think the Honda, Nissan, Mitsu. motors are much stronger as a Hot rodding platform. They are also low compression so they adapt well to variable boost turbocharging. Complete sets of racing pistons, rods, cams, etc. are cheap and available everywhere. They are easy to keep cool and there is usually room under the hood for lots of HP add ons. It is not uncommon to get 200hp/liter on a built VTEC motor and have it hold together pretty well.

The 986 2.5L is a very highly developed, high compression N A motor. At 11/1 compression it doesn't adapt very well to forced induction (detonation is a problem). Essentially zero internal parts are available and there is no aftermarket for internal racing parts. The radiators are far away from the motor so it is harder to get rid of excess heat. And no room under the hood. From what I have seen I think that 100hp/liter is the ragged edge of a reliable performance envelope on this motor and you are already there.

Pushed to the breaking point, cause of death could be: blown head gasket, broken pistons, thrown rod, IMS failure, broken crank, failed main bearings, slipped cyl. sleeve, seizure due to overheat etc. The blown head gasket is the only one that is repairable. Quite a different story than a Chevy small block or Honda VTEC.

You are a pioneer. You are blazing a path over the dead bodies of others who have pushed the performance of the 986 and lost. I hope you succeed. This country was built by those who didn't accept conventional wisdom. It's your car. If you want it I say go for it. What would Chuck Yeager or John Glen say?

[pk2]

Originally Posted by Gary in BR

I AGREE 100%

Thanks Gary for the encouraging words. Glad yours is holding up well. I’m actually holding it up as a benchmark.

I kinda studied the crap out of cooling (IC; air to air, air to water, etc) and the water/alcohol seems to make the most sense for an SC in this car. In the past I've pooh pooh’d it as a kludgey solution but the more I’ve read…it’s legit, not really tricky and not really a big hassle.

The concept and implementation was actually developed for super charged fighters and bombers in WWII. Got them up in the air... fast.

Aside from heat, the super charger itself has limitations. It needs to be the pretty small form factor it is to fit the car physically. How much more it can be milked at the low end without actually being a drain at the top end or, spining the sc to fast, isn’t clear yet, pretty much a matter of doing some math though.

So, if your getting 270hp comfortably, thats what I'll aim for. According to the manufacturer, I’m already there and then some, but I’m not buying…yet.

Regards, PK

BTW, how many miles have you chalked up on your turbo?