Why not NOS?

[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.

[Kirk]

I agree insite. It's not just cheaper to drop in a 3.4 or 3.6, but you also get OEM reliability. Still there's more power potential by going to forced induction.

I said it was fun stuff to dream about because it's really a dream for someone like me. See I live in the communist state of California. Here you could do an engine swap (and then get it approved), but a custom turbo setup would be completely illegal.

Right, I understand the cooling effect of nitrous, which is why some folks use it to cool their intercoolers... The point is that A. Graham Bell claims a stock 10.2:1 CR engine can maybe do 5 psi boost with a very efficient intercooler. The original question here was what can a Boxster do on nitrous. Based on Bell's chart I'd estimate that our 11:1 CR engine could probably handle 3 psi with a cool charge. What would be the HP shot equivalent in nitrous of a 3 psi boost from a turbo? Hmmm... maybe around 40 HP or so is what I'd guess.

Pics of that intercooler install would be "cool".

Kirk

[dmcutter]

Turbowerx includes an intercooler with the 3.2 turbo kit. Marc says he feels like he has a good factor of safety with 5 lb of boost with stock internals. Of course I don't know what sort of longevity testing their mule went through and I don't know how many of their kits have been installed.

The orginal question about NOS was driven by a curiosity about cheap horsepower. Obviously a system that is properly engineered for our engines would not be cheap relative to an off the shelf kit for a big block V8, but may still be "cheap" relative to a turbo or engine swap. I like the idea of a turbo better though because as Randall said it's always right there at your right foot. And since our cars are not about straight line power and I think a hefty shot of NOS would be tough to modulate in a curve, the turbo is more real world usable.

I was discussing this with Jay this am and I said one of the appealing things about the 3.2 is that it makes about 80% of peak torque at such a low rpm. If you went with a low compression piston to boost boost, I think you would give away low end. With a turbo, you still have stock low end with the extra forced induction power being icing on the cake.

NOS is an interesting academic exercise, but I don't think a practical app for the Box. I do still plan on going the turbo route this fall or winter, though, as finances allow.

[Jake Raby]

After recently cutting a stock Boxster piston in half to do a cross sectional study on it, I'd say it would not be very kind at all to the cylinder pressure increases associated with fogging the engine...

Turboing the Boxster is certainly the best all around way to gain performance.. The Turbo specific engine combination we are developing now, coupled to the cylinder upgrades is sure to make serious power, reliably.

Jake Raby
www.flat6innovations.com

[ekam]

^Now there's some sound advice!

I read the post over at 6speed about a Cayman S that gets turbo'd by Evolution Motorsports making 400+rwhp and the engine still has stock internals...

I'm sure it'll be fun while it lasts but the guy's basically driving a ticking time bomb.

[RandallNeighbour]

Jake, please develop and sell a 3.4 turbocharged motor for the boxster with all the cylinder sleeves and other great parts I just saw on your web site.

I'm betting you'd sell enough of these now that cars like mine are 12 years old and on the second motor. I won't replace my motor again with a 2.5, that's for sure. I'm going for wicked-fast next time around.

[Jake Raby]

The issue with the 3.4 would be the cylinder wall thickness. Even with our proprietary Nickies cylinders and installaction processes, cylinder integrity under boost would be a concern with the 3.4 bore size.

At the current we are working on two Turbo engine sizes, one is based off the stock 2.5 engine and remains 2.5L, but uses much thicker cylinders and is designed to see serious boost levels. This engine package will reliably create 300RWHP easily at low boost, using all Turbo specific components like our billet rods, upgraded rod and main bearings as well as thermal barrier and friction reduction coatings, dished (boost specific) pistons and a camshaft thats further optimized for boost.

The other is based from the original 3.2 engine, but we use an even thicker cylinder for serious levels of boost. This combination is still being designed, but I expect 400HP at low boost a possibility..

More power could be made, but we are engineering reliability into these packages, not maximum output and thats the rreason why we want to create big power from lower boost levels, not putting the engine "on edge".

Any power adder has the capability of enhancing output, or blowing the engine to bits- effectiveness is 100% in the subsystems and engineering that goes into them, from the fuel tank to the exhaust pipe..

I'd certainly never add boost to a stock 9896 engine, it doesn't have the proper CR and has inherent engine issues that create failures when being driven mildly while being well maintained.. Adding boost has proven to be a catalyst for most, while some have gotten decent mileage from them..

I won't replace my motor again with a 2.5, that's for sure. I'm going for wicked-fast next time around.

Guys like you and their desires are exactly what we hope to fill, both normally aspirated and forced induction.

Anyway, hate to steer the topic way off track, especially since I am a new guy here.. So if you want more discussion maybe we should start a new thread and allow the NOS conversation to ecape from the Hi-Jack :-)

[dmcutter]

Since I started the thread, you have my permission to go off on the turbo tangent.