Supercharger

[Frosty]

Hardcore I can see your point, but you must remember that you are going to build an engine to withstand 1 bar of boost (for arguments sake) and so if it gets from no boost to 1 bar in 3,000 revs (super) of 500 revs (turbo) the engine is still going to see 1 bar in the end. If the engine is built to withstand it, there will be no problem.

Your example with the paper is not really valid, because:

a) When you do snap your hands apart, you will have applied much more force than just applying pressure gradually due to the sudden movement. The paper has torn because of more force, not because of a sudden force!

b) In terms of an engine, boost from a turbo does happen gradually. Lets say in our example that our turbo provides no boost below 3,000rpm, starts to spool at 3,000rpm, and is blowing fully by 3,500rpm. A typical turbo setup.

Lets say it takes half a second to reach full boost - in the 3k to 3.5k rev range, the engine has completed between 25 and 29 complete combustion cycles. Each time with progressivly more boost. Thats fairly linear and gradual.

As you said though, the transmission suffers a bit. Thats another can of worms though.

 

[RobFenn]

The way the fords problems is nothing to do with the engine! Its just track biased

 

[Frosty]

If you took off that torque biasing differential and fitted it with a standard or fast road LSD, it would be a great car for the road. Theres always a compromise somewhere.

Besides, most of the people that buy them will be more worried that it has an RS badge, but a rear wing only a fraction of the size of the Escort Cosworth. LOL!

 

[HardcoreSax]

"the engine is still going to see 1 bar in the end"

Your not just designing the engine to withstand just boost though are you...

I cant be bothered to go into this in great lenght so lets just look at MEAN PISTON PRESSURE for a 4 stroke engine

p= (4 x pie x M) / VH

p = pressure

M = Torque

VH = Displacement of engine

The more torque an engine produce the greater the pressure on the piston

Pressure = Force / Area

=> Force = presure x Area

Same piston area, larger pressure (ie more torque) = larger force

Turbos produce far more torque than superchargers even if they produce the same power, that is pretty much without question. More torque equal more pressure on the piston which means more force on the con rods, which means more force on the crank blah blah blah...

matbrown > Hows things going... cant believe PGTI mixed up my photos! I emailed them about it and they said theyd sort it out in the upcoming issue, not sure exactly what that means but well see. Im going to another PGTI shoot out in april its just cit vs pug this time though should be fun!

 

[Tom]

Erm im confused i drove a RS about two weeks ago, its a great car with no real problems and i didnt think it was "track biased" at all

the only problem i had was the seats bloody horrible (im only small)

 

[Frosty]

Hardcore - What your saying is correct in that a turbo will produce that 1 bar for a longer rev range. I know that you dont just build an engine to withstand 1 bar, I wasnt going all scientific, but its making really good discussion, so Ill carry on.

Based on what you have said, the force on the piston will be greatest at the point of peak torque. This may be the case, but clearly the engine is under the most stress at PEAK POWER. If the engine can withstand the stresses imposed at peak power, it can handle those at peak torque. Your last post has hit the nail on the head - remember I said my preferance would be turbocharging? Thats why - greater torque during most of the rev range.

"the engine is still going to see 1 bar in the end"

That quote was just to outline that 1 bar at peak power will impose more stress than anything else (on saying you dont over-rev your engine).

Laurence