Why the low torque?

[Tcoat]

Originally Posted by Ubersuber

It does seem pointless to continue this debate with you but what the hey.

I'm sure you have some theory or other explaining how a variable compression ratio can produce ANY extra power so please feel free to share it with us.

As for variable displacement only supercharging can achieve this so far, although the Stirling cycle engines do create this effect and no doubt you can explain how that happens also. Hint, when is a calculated CR not the true CR?

It is quite clear to anyone who understands these things that the SAAB engine developed its power and torque by supercharging and not by varying the compression ratio. The combustion chamber size was varied precisely to maintain the effective compression ratio more or less constant. The Stirling cycle engine pulls off much the same trick with a fixed CR and a fixed displacement. The Miller cycle version uses supercharging to better exploit the Stirling cycle (Mazda's new skyactiv gasoline engines can run such nominally high CR because they use the Stirling cycle as well as a carefully shaped combustion chamber in the piston head to allow lean burn. Mazda has a lot of experience with the Stirling cycle and the Miller cycle).

To assist you in more fully understanding why the SAAB variable compression ratio engine worked only because it was a very highly pressurized supercharged engine and for no other reason it may help you to recall the F1 engine rules which stated an equivalency between 4.5 litre naturally aspirated engines and 1.5 litre supercharged engines (when running the same fuel) which was a 3:1 equivalency, which later was reduced to a 2:1 equivalency which allowed the 1.5 turbos to literally blow the very successful 3.0 litre normally aspirated engine into the history books. Even 3.5 litre normally aspirated engines could not compete with 1.5 litre blown engines.

Rest assured that you are alone in failing to understand that variable effective displacement is very real. The current C)2 emissions regulations in Europe are pretty much requiring that all powerful engines be supercharged in some form or other.

Displacement on demand won't cut it and everybody in the industry knows it.

FOR GOD'S SAKE GIVE IT UP MAN!!!!!!

[Dipstik-sportech]

All the new engines are going turbocharged not supercharged BTW.

[Ubersuber]

Originally Posted by Dipstik-sportech

All the new engines are going turbocharged not supercharged BTW.

Turbochargers are superchargers.

[Ubersuber]

Originally Posted by Tcoat

FOR GOD'S SAKE GIVE IT UP MAN!!!!!!

No need to shout.

[Dipstik-sportech]

Originally Posted by Ubersuber

Turbochargers are superchargers.

Ugh r we really going to debate this again like on the Subaru BRZ forum?

[CoupedUpSubie]

Originally Posted by Dipstik-sportech

Ugh r we really going to debate this again like on the Subaru BRZ forum?

UberSuber is actually right on this matter. A supercharger is a device which forces more air into an engine, keeping the intake pressure above atmospheric pressure. You have various types of super chargers. They can be belt, gear, electric, and even exhaust driven.

And there have been quite a few things that I do not agree with him on.

[Tcoat]

Originally Posted by Ubersuber

No need to shout.

Would have been the same if it had been Mikem or one of the anti Ubersuber crowd believe me!
I don't profess to have anything more then the basest knowledge in modern engine technology so don't have a clue who is "right" or "wrong" on the subject matter. I think we all get that you have opposing view points and would like to convert the others to them. BUT... it reaches a point where any valuable info gets lost in the bickering and the rest of us actually come out poorer for the whole thing!
We all have our own reason's for being on the forum, be it to find info, give info or just to enjoy the social aspects. Of course with the diverse crowd that owns these cars opinions will vary, but you said yourself "it is pointless to continue this debate" then followed up with yet another chapter. Perhaps your adversaries and yourself would care to present your credentials that make you qualified to make the statements you do so those of us that are less informed can pick a side and support you as these arguments go on from thread to thread ad perpetuum!

I have little doubt many people on here find some of my mindless drivel and participation in random thread hijacking obnoxious but I like to have fun and enjoy the company of others that do as well.
And again BUT... I can also ask for and provide information without writing a 500 word dissertation that does not include any supporting references or material sources as evidence. I am not just talking about you but also the guys accusing you of this that do EXACTLY the same thing.

I will climb down off my soapbox and wander away now.

[Dipstik-sportech]

Originally Posted by CoupedUpSubie

UberSuber is actually right on this matter. A supercharger is a device which forces more air into an engine, keeping the intake pressure above atmospheric pressure. You have various types of super chargers. They can be belt, gear, electric, and even exhaust driven.

And there have been quite a few things that I do not agree with him on.

All thumbs are fingers but not all fingers are thumbs.

My debate wasn't whether one was the other. I said engine are going turbo ie exhaust driven now for fuel economy. 99.9% of people believe a supercharger is engine driven and a turbo is exhaust driven. Times change though and now they pretty much have their own classifications.

Turbochargers were originally known as turbosuperchargers*when all*forced induction devices were classified as superchargers. Nowadays the term "supercharger" is usually applied to only*mechanically*driven forced induction devices. The key difference between a turbocharger and a conventional supercharger*is that the latter is mechanically driven by the engine, often through a belt connected to the*crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's*exhaust gas. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive.*

[stonenewt]

Originally Posted by Dipstik-sportech

saab svc engine concept promo 2000:

Show me one point in that video where they say increased effective displacement. You can throw around your theories all you want, in the end "effective displacement" is not a real thing. You're attempting to say that it makes the engine seem bigger due to the supercharger, that's nothing new bud. The only way to alter ACTUAL displacement it by increasing cylinder volume not combustion chamber volume. Also BMW did have the same free valve system in the works i just checked but it hasnt made it into production and that was back in 2001 i believe. Oh, FYI Saab did kill itself off GM cut them loose like other companies did before due to there no profitable design ideas.

An engine is basically a very complicated air pump with a net power gain. The more air, by weight, you can get to flow through the engine the more power you make. A high CR engine allows for a higher air mass to flow through the engine so you want to run the highest CR as you can get away. The problem is when you add forced induction, higher levels of boost require lower CR to counter pre-ignition which means when air isn't being forced into the cylinder it's sluggish.

Saab developed a system that allowed them to have a high CR N/A engine for good off-boost performance and a low CR for high boost forced induction. Net result is you have a low-lag, high throttle response big-boost engine. This variable CR technology seems to be only useful when combined with some kind of forced induction. Also this seems like it's been superseded by direct injection petrol engines which can run a higher CR without pre-ignition issues.

[Dipstik-sportech]

Exactly ^ not effective displacement. Using his theory and engine that is boosted has higher effective displacement. Saab just designed that so they could as you said make more power without detonation.

[Tcoat]

Originally Posted by stonenewt

An engine is basically a very complicated air pump with a net power gain. The more air, by weight, you can get to flow through the engine the more power you make. A high CR engine allows for a higher air mass to flow through the engine so you want to run the highest CR as you can get away. The problem is when you add forced induction, higher levels of boost require lower CR to counter pre-ignition which means when air isn't being forced into the cylinder it's sluggish.

Saab developed a system that allowed them to have a high CR N/A engine for good off-boost performance and a low CR for high boost forced induction. Net result is you have a low-lag, high throttle response big-boost engine. This variable CR technology seems to be only useful when combined with some kind of forced induction. Also this seems like it's been superseded by direct injection petrol engines which can run a higher CR without pre-ignition issues.

Credentials please!

[stonenewt]

I've read & appear to have fully understood Four-Stroke Performance Tuning & Force Induction Performance Tuning by A. Graham Bell as well as Street Turbocharging by Mark Warner. The first two might be considered fairly light bed time reading... along the lines of War & Peace

[sklimo]

I can count to potato

[stonenewt]

Originally Posted by sklimo

I can count to potato

You now owe me a new keyboard. This one is coffee coloured!