Quote: posted by sutherlandm on 10/03/2005 12:50:07
So are all these Dyno's wrong then?
The vast majority of them, Yes!
Do they need you to recalibrate them all?
No. They just need to give standard figures, give or take, for standard cars to be believable.
Where's a "proper" one?
I believe VW have some rather accurate engine dynomometers at their factory.
Are your figures of a million horsepower actually right?
I don't claim a million horsepower, and am extremely skeptical of a lot of the big turbo kit makers claims. I just know that Subaru use my turbo on 300hp PPP'd stis. The limitation of the turbo is how much air it can move, and thus power it can make. From fairly extensive data logging I can tell you that I have maxed out this turbo, so all I claim is that the car is somewhere between 300 and 320hp.
Does sticking a turbo on a car mean you can quote any bhp figure you fancy?
No. It's just that torque is about airflow. You can only get so much air into a normally aspirated engine, and therefore maximum torque is fixed. Forced induction gives you the ability to effectively increase the cubic capacity of the engine to whatever the maximum airflow volume of the turbo dictates.
How come some cars have very low torque but high bhp and vice versa then if bhp is a function of torque?
As I've said torque is a function of cubic capacity. If you want to make high power from a normally aspirated engine, you have to increase it's volumetric efficiency at higher rpm's to produce peak torque at higher rpm, at the cost of low down torque.
All small engines producing high power have torque peaks at much higher engine speeds than the R32 does.
To improve volumetric efficiency, you need to keep pressure drop in the intake and exhaust system to an absolute minimum, and if you play with intake tract and exhaust length you can actually achieve slightly more than 100% VE. This is using the momentum of the air in the intake tract and gasses in the exhaust to effectively force air into the combustion chambers, instead of relying entirely on atmospheric pressure.
You might notice that most production engines other than highly tuned engines from Honda, BMW, Ferrari and a few others, all produce 75lbft/l and 75hp/l give or take.
This gives a tractable engine with a 6-6.5k redline that is flexible for normal drivers who don't want to rev the knackers off their cars.
alfa 2.0lJTS engine 76lbft/l, 82hp/l. 16v variable valve timing, twin spark etc gets it to a little over 75hp/l
astons 6.0 v12 engine -70lbft/l, 75hp/l, big lazy low revving V12. Slightly down on torque but it's torque peak is produced low in the rev range.
Audis 2.0l fsi -74lbft/l, 74hp/l. Clever new FSI technology.
Bmw's 3.0l -74lbft/l, 77hp/l
Mercedes 3.2l - 72lbft/l, 68hp/l
I can't be bumd to pick any more for you, But do you see a pattern forming.
Now for the high revving screamers
Bmw M3 engine 84lbft/l, 107hp/l. Flat as a pancake until 5000rpm, them hold on.
Honda 2.0 (type R) 72.5 lbft/l, 98.5hp/l
ferrari 3.6l 76lbft/l, 111hp/l.
Now which of the two categories do you think the r32 engine falls into? Low revving plodder with a 6.5k rev limit, or high revving screamer with a 9K rev limit.
You might see how clever the M3 engine is now as well. Shame they go bang so often.
The 6364 update cures an oversensitive knock control sensor - So the timing has not been advanced.
If the update has gained any timing at all I will be surprised, especially if the cars are run on 98ron fuel. They will however have played with the throttle response and exhaust switchover valve to get rid of the odd torque dip in the mid range. Something the remappers did quite successfully.
Basic questions following over complex answers.
Simple questions, and fairly simple answers.