Why not NOS?

[dmcutter]

I feel compelled to rat Jay out now that he's joined and is posting. HE is the one who instigated all this.

[jay3000]

Originally Posted by dmcutter

I feel compelled to rat Jay out now that he's joined and is posting. HE is the one who instigated all this.

And, we've all learned something.. Hopefully Kirk will tell us more. He seems to know alot more than "it'll blow it up"..

It does seem to be a difficult engine to get much more performance out of.

[Kirk]

Originally Posted by jay3000

It does seem to be a difficult engine to get much more performance out of.

I'm not sure there's really anything in particular about this engine that makes it more "difficult". The high compression ratio is great for a naturally aspirated engine. It's only when you try some form of induction that it's a problem. The lack of improvement from headers, exhausts, and intakes on performance just tells me that Porsche makes a good, highly tuned product from the factory that is already pretty much at the peak.

The tight packaging is a bit of an issue though. Where do you even put a supercharger, turbo, or intercooler? The engine bay is really tight, which makes these issues more difficult to overcome.

But back to the engine... again I don't think it's so much "difficult" as it's just underdeveloped. If you could buy some pistons that would drop the compression ratio to 8:1, a forged crankshaft, forged connecting rods, etc., then you could rebuild the bottom end for not 4 psi of boost but more like 14 psi of boost and run that all day long with no problems. But nobody out there is really developing these kinds of parts for the Boxster engine. That's a shame... but for the same money or less people would just rather drop in a 911 engine, which makes a lot of sense.

[dmcutter]

I talked to Marc at Turbowerx a lot when he was developing the kit for the 3.2 and he said he could do a monster build with low compression pistons and such and run high boost and get around 500 hp. He estimated the cost would be about what most people are talking about for a 3.6 transplant. I would really worry about that much power being tractable, though...last year on the TOD in the rain my PSM kicked in a few times. Twice the stock power would be pretty hairy unless I kept it about 2 gears high and below the powerband.

[Adam]

Originally Posted by dmcutter

I talked to Marc at Turbowerx a lot when he was developing the kit for the 3.2 and he said he could do a monster build with low compression pistons and such and run high boost and get around 500 hp. I would really worry about that much power being tractable, though....

It wouldn't be usable power in the first couple gears since boxsters don't have an LSD. You would have to budget in an aftermarket limited slipper if you did something like that.

[Kirk]

I'm re-reading the book "Forced Induction Performance Tuning". There's a chart on page 77 that's helpful. It shows what boost level is recommended for a modern stock engine (most of the book is focused on race engines) at different compression ratios. With a 10.2:1 CR and a nicely 80% efficient intercooler you're looking at maybe 5 psi as being safe. I think that helps to illustrate why our 11:1 engines with no intercooler would be pushing it with any kind of boost - whether from a turbo or nitrous.

An interesting website I found today is this one:

http://www.flat6innovations.com/performance.htm

It will be interesting to see what these guys can develop. It looks like some lower compression pistons and stronger connecting rods for the 3.2L may be on the horizon. It sure would be fun to build one of these engines for boost, but their prices make it a pretty costly proposition.

To really push it though you need an intercooler and they point out that there is a real packaging issue with fitting an intercooler on the Boxster. But with a good front trunk I would definitely be willing to sacrifice my rear trunk, it's close to the engine, and you could fit a very big intercooler back there. You'd have to modify the trunk to bring air in - maybe a scoop facing forward on the trunk. Then you'd have to vent air out the bottom of the trunk, but that's all do-able.

Seems like with a rebuilt bottom end for strength and low CR, plus an intercooler, twin turbos, and some exhaust work you could push 400 HP pretty reliably. Fun stuff to dream about! Throw in a wide body kit and wider rear wheels and you'll help that wheel spin problem.

Kirk

[insite]

the problem with going strong on forced induction with these cars has always been cost. it's much cheaper to drop in a 3.4 or 3.6L motor and go from there. hell, you can even add a set of schrick cams, sick exhaust & intake, etc for MUCH lest than the cost of cracking open the motor to lower the CR & upgrade the rods & go turbo.

BTW, one of the nice things about nitrous is that the gas cools the charge by nature, so detonation won't occur until cylinder pressures are quite high. obviously no need to intercool a nitrous charge.

kirk - i have seen a turbo app on a boxster where they put a large intercooler in the trunk. i will see if i can find pictures.