Turbo vs Supercharger - 986 Forum - The Community for Porsche Boxster & Cayman Owners

MNBoxster · 11-29-2006, 10:58 PM

Quote:

Originally Posted by NickCats

Jim,

Found another thread about this subject :

turbo or supercharge ?

Look like your opinion hasn't changed much in the past year.

I am surprised you prefer the supercharger over the turbo for the Boxster, though...

Nick

Hi,

Doesn't surprise me that my information (or opinion) hasn't changed at all. I have had a fair amount of experience with Forced Induction both in Aircraft and Automotive applications. Each has their advantages and disadvantages. But these are not generic, rather, they often depend upon the application.

With the Boxster, being mid-engined, I think the Heat Management issues alone (let alone the plumbing issues) would outweigh the advantages of a Turbo. So, I would most likely choose the Supercharger route.

That's not an endorsement, at least without Intercooling, or some other way to prevent detonation given the high CR that the Boxster has...

Happy Motoring!... Jim'99

pecivil · 11-30-2006, 08:34 AM

Trigem2k!

When you get your turbo set up, lets hook up and you can compair it to an NA 3.4l :dance:

If you will get 270 to the wheels, it should be close to mine. I am in San Diego and would love an excuse to get up there to drive some of the canyons in Malibu!!

If you guys are spending 7k for the kit, and 2k for install, why not just go with a 3.4 conversion, with no detonation potential, no real heat issues, and no worries about going to FI on a high CR motor?

Theres no way I would go to FI on with the CR the M96 has with no IC.

I have an eaton SC on my E36 318i with no IC and the CR is 10:1. And that is pushing it but it only gets up to 6 psi. But it kicks ass when a E36M3 can't pull on me in a little ol 318 :dance:

I would imagine that they tune the ECU to accomodate the additional fuel required to match the FI, for either system, right?

ohioboxster · 11-30-2006, 09:03 AM

Yes Jim but what do you do if the car doesnt detonate? You know even when my car continues to run for trouble free mile after mile I have a feeling there are people that will say "Fluke" or "Lucky". I just dont understand why several people say the car will detonate due to the compression ration. I drive my car everyday without issue. Let me clarify, Im not looking for an endorsement or even convince you of anything but just want you be aware 5 lbs of boost does not make the car detonate.

David_J · 11-30-2006, 09:09 AM

Upgrading a 3.2 to a 3.4 doesn't seem a logical choice for what you get. I mean, my 3.2 only has 24000 miles. Why would I want to upgrade that to a 3.4? Adding a SC to a 3.2 sounds like a good choice for me.

-David

MNBoxster · 11-30-2006, 09:39 AM

Quote:

Originally Posted by ohioboxster

Yes Jim but what do you do if the car doesnt detonate? You know even when my car continues to run for trouble free mile after mile I have a feeling there are people that will say "Fluke" or "Lucky". I just dont understand why several people say the car will detonate due to the compression ration. I drive my car everyday without issue. Let me clarify, Im not looking for an endorsement or even convince you of anything but just want you be aware 5 lbs of boost does not make the car detonate.

Hi,

I never said your car detonates. What I said was that at anything over 8.5:1 CR, detonation becomes a concern. At 11.7:1 CR, it becomes a major concern.

Your car may be detonating at certain times and you're unaware of it, it may be doing so under certain conditions (Ambient Temp, Load, Fuel Quality, etc.). The DME may be compensating for it by using a detuned MAP, I don't know, I haven't studied your specific installation and all it's pertinent parts and those of the motor itself. But, if you are at times detonating, it's probably not enough to grenade the engine, but what are the longterm effects?

The rule of thumb is that anything over 10:1 CR requires Intercooling to be safe from detonation. Porsche doesn't force the M96 engine in any of their cars, what do they know that we don't? The Turbo uses a different engine. The TT engine (M96/70) is similar to the M96, but also very different - 8.4:1 CR.

Adiabatic Heating (a Gas rises in Temp if it is compressed) raises the Charge Temp 11°/1 PSI (10.9°/1 PSI to be precise). So, at 5 PSI, your intake charge is 55° hotter than the Ambient Air entering the Intake. On a 60° day, this means a lot less than on a 98° day, because the Charge temp would be 115° on the 60° day, but 153° on the 98° one. This heated charge will reach a detonation threshold (approx. 268°) a lot sooner in the compression stroke (where it is further compressed and heated) than Ambient Air charge would, which is what the engine was designed for (Pistons, Bore, CR). This means the engine must produce a spark sooner to compensate. How much sooner is it capable of? I don't know. How soon is too soon? Again, I don't know. But, it's the not knowing which concerns me.

Also, one bad batch of fuel and you could have serious problems. That's just too much risk management for me I guess...

Happy Motoring!... Jim'99

11-30-2006, 11:22 AM

Why dont we all cool down. I am a fun loving teenager who is popular and a practical joker, thats my personality. Others may be recluse, obnoxious, meticulous, or just plain grouchy, but thats who we are and we cant change that. The problem arises when 2 grouchy people get into it and gripe at each other, so when the person accuses the other of being grouchy, they themselves are grouchy. Its just a forum, chill out, words dont hurt anyone unless you choose to react to them. We are all smart people on this forum (cant say the same for the integra forum, lol) due to the fact we drive a boxster in the first place. We are all adults, lets act like it.

z12358 · 11-30-2006, 11:32 AM

Quote:

Originally Posted by boggtown

Why dont we all cool down. I am a fun loving teenager who is popular and a practical joker, thats my personality. Others may be recluse, obnoxious, meticulous, or just plain grouchy, but thats who we are and we cant change that. The problem arises when 2 grouchy people get into it and gripe at each other, so when the person accuses the other of being grouchy, they themselves are grouchy. Its just a forum, chill out, words dont hurt anyone unless you choose to react to them. We are all smart people on this forum (cant say the same for the integra forum, lol) due to the fact we drive a boxster in the first place. We are all adults, lets act like it.

Sorry but I can't see what problem you are referring to. Personally, I enjoyed the information and opinions shared in this thread.

ohioboxster · 11-30-2006, 11:34 AM

Boggtown,
Jim and I have a difference in opinion and I dont believe we are out to hurt each others feelings. We have not made inflamatory comments to each other and I cant speak for Jim but Im not looking for a fight. If these comments were directed at us you are mistaken, if not disregard.

11-30-2006, 11:46 AM

I am reffering to the entire forum, not a particular incidence, sometimes people can act a little strange sometimes. Im just trying to remind people that the more friends you have, the easier your life is. Life is your time spent with people you like and dislike, if you dont dislike anyone, your life will be much better. I just want you all to know your all my friends and if I take a long trip, I will try and stop by and say Hi to you all.

MNBoxster · 11-30-2006, 12:37 PM

Quote:

Originally Posted by ohioboxster

Boggtown,
Jim and I have a difference in opinion and I dont believe we are out to hurt each others feelings. We have not made inflamatory comments to each other and I cant speak for Jim but Im not looking for a fight. If these comments were directed at us you are mistaken, if not disregard.

Hi,

OH, I'm not sure our opinions are that different. Detonation is a well-known phenomena and is caused under certain conditions whether it's in a Diesel, Aircraft or Boxster.

It's also true that the DME can respond so quickly to the knock sensors that you may be detonating and not know it. Or, detonating at some times and conditions and not others.

Again, I'm not saying that you are, but I also think that you cannot with 100% certainty say that you're not either. You'd need a data stream from the DME to see if the Knock Sensors are detecting anything.

No malice, it's all good fun and learning. It's about truth, either it is or it isn't. Problem in this case is that there's 'evidence' on both sides of the arguement. Glad you're being the Test Bed on this... Keep up the Good Work!

Happy Motoring!... Jim'99