OK, just when you think you've got it you realise you don't.

For simpletons, why does the relationship between boost and power go all skewhiff instead of a nice linear increase?

Just from memory -
standard .8 bar = 400 bhp.
Power kit .95 = 430bhp
Kevins stage 2 peak 1.3bar = 480bhp

Ruf 1.1 bar = 510bhp

Basically, why would lower boost = more power
Why does higher boost = danger? Surely the weedly little 1.5 bar of intake pressure on the heads is nothing compared to the mighty big bang of combustion?

 

Greg H.

 

I'll add my 2 cents... Ruf adds their own special cams, so that may explain the skew in the graph. As far as how this affects combustion pressure.... If you were to cram twice as much air into the cylinder before compressing and firing, you'd have a GREAT deal more compression pressure... not just thye additional 1 bar of boost. Does that make sense?

 

ACE,

for a very very simple answer, think of the engine as a water pump. Power is basically how much the pump will flow. The pump has a hose/nozzle that pressurizes the water coming out. You can use a larger hose/nozzle and have less pressure and still flow more water than a smaller hose/nozzle with higher pressure - compare a firehose dumping out water with a garden hose with a sprayer. The RUF makes the engine a "bigger hose" by increasing the flow capacity with the cams and headwork(?) and larger turbos. Because it runs less pressure, the components should also last longer.

 

The Ruf 490 package uses the K16 turbine wheel and turbine housings. The boost that I have seen with the Ruf ECU is closer to 1.25 bars when I have had the car on the dyno.. Anotherwords, I have the data acquistion. However, if you are running pump gas below 92, boost and timing is reduced..

The very same thing is true with my Stage 2.. If you have crap gas you won't be running 1.3bars.

Now with the added camshafts the extra HP is a added benefit.

The short story is if you run 1.4 bar and 1.5 bars you will lift your heads, you will have a exhaust breach between the interior of the cylinder liners. On the down stroke of the piston, your engine will be ingesting oxygen from outside of the intake tract. This will cause a VERY lean condition and you will turn your combustion chamber into a plasma torch.

 

Well put, I like the plasma torch bit too.

 

Boost has no direct relationship to power, it has relationship to torque, and torque has relationship to HP once you get RPMs in between. Do a search for the BMEP thread and you will find all your answers.

I have graphs for real life datalogged road tests and real life HP and torque for all these cars that you mentioned above, and those numbers don't lie, they are "road dyno" numbers, the findings are extremely interesting.

Dyno data is not a reflection of what happens on the road unless you are lucky to use a $1/2 mm. engine dyno.. high Peak torque is not a reflection of a fast engine at all, be it at 2K RPMs or 4K Rpms regardless, it is how many RPMs you carry that torque, and that you can only see on the road too due to heat and load factors that you cannot simulate on a dyno.

To improve HP you need a well setup and tuned ECU and matching components that can keep that torque at the higher RPMs...in real life..