Rally Cars tech stuff

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Originally Posted by Mirek

I'm no expert but in my opinion the biggest advantage of DI is that it allows the engine to run with high air-fuel ratio. That is good for the economy under low load but not that useful for racing engine where for maximum output You need richer AFR. I guess DI is somewhat more effective for WRC engine as well but I have no idea how much compared to usual way. Maybe Dimviii or someone else can educate us?

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the resume is that with direct injection you have more horsepower because you can control better the air-fuel ratio.
You can control better the timing of injection and the amount of fuel,due to the position of injector inside the combustion chamber.

Dimviii, why does DI accommodate higher compression ratios with higher boost? Is it just the control over the air fuel ratio?

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Originally Posted by TyPat107

Dimviii, why does DI accommodate higher compression ratios with higher boost? Is it just the control over the air fuel ratio?

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allows higher compression ratios because it is prone to less detonation.

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Originally Posted by dimviii

allows higher compression ratios because it is prone to less detonation.

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Think you are very close to the main issue here, to avoid detonating when trying to create an explosion.Pressure changes the gas to be liquefied, or drops. Heat changes liqued back into gas.This happens in the intake manifold, intake channels and inside the engine several times in a four stroke engine. A DI engine does not take account of this issue in the intake section of the engine, but can concentrate on getting the most air to enter. Currently, this is the best way to achieve what we think is the best ratio of air and gasoline (14.5 to 1).

Again, hope whoever understands this on a different level, do not tear off his hair.

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Originally Posted by Coach 2

Think you are very close to the main issue here, to avoid detonating when trying to create an explosion.Pressure changes the gas to be liquefied, or drops. Heat changes liqued back into gas.This happens in the intake manifold, intake channels and inside the engine several times in a four stroke engine. A DI engine does not take account of this issue in the intake section of the engine, but can concentrate on getting the most air to enter. Currently, this is the best way to achieve what we think is the best ratio of air and gasoline (14.5 to 1).

Again, hope whoever understands this on a different level, do not tear off his hair.

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your english are much better to explain proper such tech points.
At fuel injected engines most lean we manage with race fuel is no more than 12,2-12,4 to 1.
to understant the difference a Mitsu evo 9 with 11.8 to 1 with an identical evo with 12,2 to 1, if we accelerate from 30km/h to 220km/h the evo with 12,2 to 1, will be about 3-4 car lengths ahead.
These air fuel mixtures(12,2 to 1) are not safe at all with fuels we use (and can find at petrol stations) at our daily cars.Case of time to break.
In my daily evo i use lean mixtures of 11,9-12 to 1 but i have some gauges to monitor detonation.

WHat compression ratio do they actually use in the 1,6 DI engines? I heard from one guy what he said Ford uses but couldn`t believe it was true..

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Originally Posted by AMSS

WHat compression ratio do they actually use in the 1,6 DI engines? I heard from one guy what he said Ford uses but couldn`t believe it was true..

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so what did you heard? 11?

By the regulations the max. compression ratio is 12,5:1.

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Originally Posted by OldF

By the regulations the max. compression ratio is 12,5:1.

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Than what I heard was bogus, must have been the "calculated" (boost included) CR

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Originally Posted by SlowSon

So I want to repeat the question, when VW is allowed to introduce (homologate) big changes?

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Three years before any major changes to the car. VO, ER etc. homologations possible.

“The rules state that you should be driving the same car three years and we're going through the last season now and VW the first season.”

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