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harryrcb

TO ALL 986 OWNERS -What do you think?

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Fellow enthusiasts, I am curious to know why more 986 owners have not turned to turbo charging their cars. I know there is a lot of interest in modifying and getting more horse power. The number one complaint of the 986 and some of the 987 has been that it’s underpowered. Is it that you are afraid of the consequences or is it the high price associated with the kits that are available today? I would be interested to know would you consider Turbo charging your car, if the price would be in $ 6500 range and getting results such as 350 hp at the wheel , running a save 5 psi boost? Please let me know, I appreciate your time.

Regards

Harry R Chamness

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Fellow enthusiasts, I am curious to know why more 986 owners have not turned to turbo charging their cars. I know there is a lot of interest in modifying and getting more horse power. The number one complaint of the 986 and some of the 987 has been that it's underpowered. Is it that you are afraid of the consequences or is it the high price associated with the kits that are available today? I would be interested to know would you consider Turbo charging your car, if the price would be in $ 6500 range and getting results such as 350 hp at the wheel , running a save 5 psi boost? Please let me know, I appreciate your time.

Regards

Harry R Chamness

We just finished a rebuild of a customer who had a turbo in his 2.5L Boxster

over boosted it and broke the ring landings on the pistons.

Bore of engine wasn't even close to being in spec -- but no idea if that had anything to do with the turbo

charging -- although I expect it did.

I highly recommend an intercooler.

Mike

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I have one. A supercharger anyway. Great fun. I mutter a hail Mary every time I take it out though and with good reason I think.

-First the ol' 2.5 can barely hold itself together as it is. It wasn't designed for a whopping 100 more hp. So logic says...

- If you live in a state like mine, every 2 years It's time for an exhaustive smog test. You can make it run clean but if they can figure out where the engine is and bother to have a look and see all that plumbing, you get to have it returned to stock by the state at your expense...or donate it for scrap for your favorite charity.

Regards, PK

Mike,

Did you go above 4-5 psi and if so did you have methanol/h20 injection?

Edited by pk2

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I'd do several things before adding a lot of power, or even a little to an S. LNE's IMS fix first. Adding a third S radiator would be next if I had a basic Box. Then brakes. Certainly would re-look suspension, especially on an older car. Maybe add RoW 030. And wheels and tire should be considered.

And my simple answer would be an emphatic NO to forced induction. Personally I'd let Jake Raby work some magic with a bigger bore and some fine tuning. Not cheap, but great and apparently reliable results.

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I think that anyone moving away from normally aspirated versions of these engines is asking for trouble, regardless of the method.....................

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I wouldn't expect great longevity out of unmodified M96's running any kind of forced induction...they're simply not designed for it. Things that I could see being a problem:

1. AluSil (aluminum and silicon) block/sleeves - this material is used so the block is light. Many forced induction blocks are cast iron or something else heavy in order to be strong.

2. Compression ratio - 11:1 is super high! This is why some running FI blow the piston rings eventually. FI engines are typically in the 8:1 or 9:1 range. High CR also increases the chances of detonation.

3. Heads - how much heat can the exhaust valves take? FI cars tend to have sodium filled valves to help channel heat away from the valves into the head. If you're whooping the hell out of the engine on a track and heat up the valves enough, they can melt/fall off.

4. Internals - If I remember right, the crank is forged, the rods are forged, but the pistons are cast.

I'd like to run FI someday but not without upgraded rods/lower compression pistons/LN sleeves/possibly some head work if it's necessary. Given the money required I'll probably just skip it and buy a faster Porsche ;)

Edited by Dr.Strangepork

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DR.

Not to diminish your own basic premise as I happen to agree more less (my car has a blower) but your observations need a little follow through

I wouldn't expect great longevity out of unmodified M96's running any kind of forced induction...they're simply not designed for it. Things that I could see being a problem:

1. AluSil (aluminum and silicon) block/sleeves - this material is used so the block is light. Many forced induction blocks are cast iron or something else heavy in order to be strong.

Many arn't. Porsche started fiddling with AluSil in the mid 70's and did a nice job of it easily accommodating 250-300 hp ( the block doesn't care if the h.p is through normal aspiration or FI). It doesn't mater the material, it maters how it is engineered for strength. Cast Iron blocks can and do crack all over the place.

2. Compression ratio - 11:1 is super high!...FI engines are typically in the 8:1 or 9:1 range. High CR also increases the chances of detonation.
.

The ECU should prevent most detonation BUT your half right, it doesn't prevent severe heat build up in the combustion chamber. This is why the boxsters boost is set at a mere 4-5 PSI. (as opossed to a 15-20 in low compression cars). I can tell you the best critical measurement off cylinder combustion chamber temp, EGT's (exhaust gas temps) are well within range at a 4 psi boost in my car. Further, if you upped the boost or wanted to be really safe, you simply add a WI (water/meth. injection or"liquid inter-cooling") to eliminate excess heat (you can drop the temps 100-200f without much fuss) to below stock.

3. Heads - how much heat can the exhaust valves take? FI cars tend to have sodium filled valves to help channel heat away from the valves into the head. If you're whooping the hell out of the engine on a track and heat up the valves enough, they can melt/fall off.

To the best of my knowledge Porsche does have sodium cooled valves. They did in 1970 (my first build) and also did in '79,( the last I checked). Again, at 4 PSI the EGT's are comfortable, ergo inside the combustion chamber and everything near it are at a comfortable temp. Were I to track my car I would add WI (water injection) for peace of mind. For the record, I'ts usually the pistons that go first in a poorly set up FI car.

4. Internals - If I remember right, the crank is forged, the rods are forged, but the pistons are cast.

Significance? What car doesn't? ( For the record, I'ts the pistons that go first in a poorly set up FI car.)

I'd like to run FI someday but not without upgraded rods/lower compression pistons/LN sleeves/possibly some head work if it's necessary. Given the money required I'll probably just skip it and buy a faster Porsche

Definitely the preferable route, one I'd prefer, but, here I am, it's 81f ambient and PCH is calling...

Regards, PK

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...

I highly recommend an intercooler.

Mike

Mile,

You'll never fit an effective, reliable inter-cooler in a Boxster unless you want to give away your trunk, do a lot of fabrication and have a lot of performance robbing plumbing. WI is really the only, and incidentally superior, option.

Regards, PK

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I have one. A supercharger anyway. Great fun. I mutter a hail Mary every time I take it out though and with good reason I think.

-First the ol' 2.5 can barely hold itself together as it is. It wasn't designed for a whopping 100 more hp. So logic says...

- If you live in a state like mine, every 2 years It's time for an exhaustive smog test. You can make it run clean but if they can figure out where the engine is and bother to have a look and see all that plumbing, you get to have it returned to stock by the state at your expense...or donate it for scrap for your favorite charity.

Regards, PK

Mike,

Did you go above 4-5 psi and if so did you have methanol/h20 injection?

Wasn't my car -- It was a customer's car -- don't know what they had it boosted to.

All the turbo equipment was removed -- when they drove it to our shop.

Here are some pictures.

Block was many mm out of ovality as well. Had to bore it out, replate with Nickel Silicon Carbide and hone back to factory spec.

After we get past the break in period of the rings -- we'll give it a dyno test.

Mike

post-34429-098698100 1287104329_thumb.jp

post-34429-032276000 1287104332_thumb.jp

post-34429-055393600 1287104335_thumb.jp

post-34429-007665100 1287104338_thumb.jp

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Thats really in interesting Mike. I've never seen the sort of damage FI can inflict on one of these motors (assuming it was the fi).. What do you attribute the ring issue to, an over heated charge(I.E insufficient inter-cooling)? Ovaloid cylinders, sort of an over-force projeced in the wrong direction (detonation or over compensated timing? doesn't look like really excessive wear or slap on the pistons? Will the sleeves mitigate this problem if an unavoidable byproduct of FI? and "D" chip potential?

I ask because I want to build a back up engine for what I sort of consider the inevitabilities of my current setup.

Regards, PK

P.S. if you happen to find out the circumstances of this failure it could be pretty instructive to some of us .

Edited by pk2

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PK,

Good elaboration on my observations, definitely cleared up some things that I wasn't positive about in regards to these engines.

That really in teresting mike. I've never seen the sort of damage FI can inflict on one of these motors (assuming it was the fi).. What do you attribute the ring issue to, an over heated charge(I.E insufficient inter-cooling)? Ovaloid dylinders, a sort over-force induced? doesn't look like excessive wear or slap on the pistons? Will the sleeves mitigate this problem? and "D" chip potential?

Correct me if I'm wrong, but that looks like the ring lands failed - my guess would the weak cast pistons as I mentioned as I've seen ring lands be the first to go on other NA engines running FI. Could be catalyzed by an older, worn engine; obviously can't tell a whole lot without inspecting the rest of the engine or knowing what the heck they were running. I'm definitely curious whether there's more tell tale signs of what did the engine in.

4. Internals - If I remember right, the crank is forged, the rods are forged, but the pistons are cast.

Significance? What car doesn't? ( For the record, I'ts the pistons that go first in a poorly set up FI car.)

My previous car, an Audi TT with the 1.8T engine, had forged Mahle pistons from the factory. Despite some people pushing 700+ whp on them, nobody had managed to get them to fail...one reason why I believe forged pistons instead of cast would be a good precaution smile.gif

You'll never fit an effective, reliable inter-cooler in a Boxster unless you want to give away your trunk, do a lot of fabrication and have a lot of performance robbing plumbing. WI is really the only, and incidentally superior, option.

What is wrong with an appropriately sized water to air intercooler setup? (or is that excluded due to your mention of reliability?) I've often seen water/methanol injection used in conjunction with an intercooler and sometimes as a replacement if an IC is difficult/impossible to accommodate.

Edited by Dr.Strangepork

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PK,

Good elaboration on my observations, definitely cleared up some things that I wasn't positive about in regards to these engines.

Thanks...I made it all up... (kidding) It's been a long time since I cared about this stuff. Best not to quote me.

Correct me if I'm wrong, but that looks like the ring lands failed - my guess would the weak cast pistons as I mentioned as I've seen ring lands be the first to go on other NA engines running FI. Could be catalyzed by an older, worn engine;

There was a guy around here with 2.5l with 110k mi, and twin turbos at about 300whp...don't know what happened to it...or him

obviously can't tell a whole lot without inspecting the rest of the engine or knowing what the heck they were running. I'm definitely curious whether there's more tell tale signs of what did the engine in..

So am I, really curious what goes bad and why in these things. Love to know more about this one. I want to build a GT "also ran" one day that won't blow apart. It's seems 67 HP per hole isn't unreasonable. They do more in Subaru's.

My previous car, an Audi TT with the 1.8T engine, had forged Mahle pistons from the factory. Despite some people pushing 700+ whp on them, nobody had managed to get them to fail...one reason why I believe forged pistons instead of cast would be a good precaution smile.gif.

700whp out of a 1.8 turbo and they don't break! Are you sure? If the engine held together I'd think the drive train would twist itself into a pretzel. amazing. Stock Mahle pistons eh, I wonder how they stack up against whatever the Box has. I've see some wasted pistons out of other FI cars but Mikes are the first out of a Box.

What is wrong with an appropriately sized water to air intercooler setup? (or is that excluded due to your mention of reliability?) I've often seen water/methanol injection used in conjunction with an intercooler and sometimes as a replacement if an IC is difficult/impossible to accommodate.

Water injection For the Box, I think its great: Something must have got lost in translation. Maybe it's my acronym "WI" it = WATER/meth INJECTION. Maybe should be WA. I'm a big believer. I schooled myself on the minutiae of the science and built a pretty trick system (now sitting on the shelf waiting for me to get interested again and find time). The whole engine pretty much has to be rtuned

As I tried to state, there is really no place to put an effective air to air intercooler set up in that car, unless you kiss your trunk goodbye, butcher it up & turn half of it into a big plenum. With that said, air-to-air has a nice advantage of having no moving parts ergo no maintenance. But for the box, WI wins hands down

Sorry for the misunderstanding, PK

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