My car is revod and its spikes at 27 psi and settles at around 24psi. Thats good for revo but my question is why do petrols produce much less psi but tend to be faster ie cupra r?
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Turbo boost psi
- Thread starter chillcupra
- Start date
Should think its down to the type of combustion process in the engine? I can't be mechanical about it, as I don't actually know. Just that diesels require larger boost to get the big power. 1 bar on a LCR for example should be sufficient to see it well over 250/260bhp? 1 bar on a pd160 cupra would be under stock. 
Not a combustion engineer, but I may be able to point some factors out.
Forced induction (supercharging, turbocharging) aims to put more oxygen into each charge packet so that more fuel can be added to produce a bigger bang. It is effectively an increase in the compression ratio. One factor, then, is that diesels start off from a bigger CR, so the effect of a given boost pressure is less.
The biggest factor, though, is that diesel fuel burns slower than petrol. This translates directly into a lower maximum rpm - try to spin a diesel any faster than about 5000 and you simply don't get anywhere, the power delivery drops off, becaue the fuel cannot complete its combustion in the time that the piston is at or about TDC.
The power delivered at the engine flywheel depends on only two things, Brake Mean Effective Pressure (= how big the bang is) and rpm (how many bangs you can get per minute). The lower rev limit for the diesel configuration makes it harder to more power (you have to go to really high compression ratio's, as in the PD engines) from a given boost.
Forced induction (supercharging, turbocharging) aims to put more oxygen into each charge packet so that more fuel can be added to produce a bigger bang. It is effectively an increase in the compression ratio. One factor, then, is that diesels start off from a bigger CR, so the effect of a given boost pressure is less.
The biggest factor, though, is that diesel fuel burns slower than petrol. This translates directly into a lower maximum rpm - try to spin a diesel any faster than about 5000 and you simply don't get anywhere, the power delivery drops off, becaue the fuel cannot complete its combustion in the time that the piston is at or about TDC.
The power delivered at the engine flywheel depends on only two things, Brake Mean Effective Pressure (= how big the bang is) and rpm (how many bangs you can get per minute). The lower rev limit for the diesel configuration makes it harder to more power (you have to go to really high compression ratio's, as in the PD engines) from a given boost.
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