Intercooler on Diesel...

[Bush65]

Petrols just do not need as much air.

So, let me see if I understand you here. You're saying that a three litre petrol engine running 10psi boost doesn't need as much air as a three litre diesel engine running 10psi boost?

I'm afraid I'll need you to explain this to me.

Intercoolers with give added preformance no matter what the boost pressure is, as it has been stated cooler air = more oxygen content = more power

Did u read any of the above

He may have read it, but I don't think he understood it.

kempster,

Ben has explained how an incorrectly sized intercooler can INCREASE the temperature of the intake air. Wrong intercooler = HOTTER air = less oxygen in the cylinder = less power.

If you can find an error in what he's posted please feel free to set us straight.

Scott

This is all too simplified.

A diesel engine does not have a throttle. The cylinder is always "pumping" the maximum amount of air that it can, regardless of load or engine speed. The engine speed is controlled by a governor, which meters the amount of fuel injected. The driver's right foot adjusts the governor setting (within limits).

A petrol engine has a throttle (usually a buttefly in the inlet) to control the amount of air to the engine. The average petrol engine spends most of the time with only a small throttle opening.

Most petrol engines can run to higher rpm than a similar size diesel, so they may "pump" more air at wide throttle openings, while running at higher rpm. But again this is usually for short durations for the average person. Not too many diesels will rev much over 4000 rpm, and they are best around the rpm corresponding with maximum torque output.

It is because of the higher flows created by high rpm that performance petrol engines place so much emphasis on flow through the heads etc.

[-Scott-]

Petrols just do not need as much air.

So, let me see if I understand you here. You're saying that a three litre petrol engine running 10psi boost doesn't need as much air as a three litre diesel engine running 10psi boost?

I'm afraid I'll need you to explain this to me.

Intercoolers with give added preformance no matter what the boost pressure is, as it has been stated cooler air = more oxygen content = more power

Did u read any of the above

He may have read it, but I don't think he understood it.

kempster,

Ben has explained how an incorrectly sized intercooler can INCREASE the temperature of the intake air. Wrong intercooler = HOTTER air = less oxygen in the cylinder = less power.

If you can find an error in what he's posted please feel free to set us straight.

Scott

This is all too simplified.

A diesel engine does not have a throttle. The cylinder is always "pumping" the maximum amount of air that it can, regardless of load or engine speed. The engine speed is controlled by a governor, which meters the amount of fuel injected. The driver's right foot adjusts the governor setting (within limits).

A petrol engine has a throttle (usually a buttefly in the inlet) to control the amount of air to the engine. The average petrol engine spends most of the time with only a small throttle opening.

Most petrol engines can run to higher rpm than a similar size diesel, so they may "pump" more air at wide throttle openings, while running at higher rpm. But again this is usually for short durations for the average person. Not too many diesels will rev much over 4000 rpm, and they are best around the rpm corresponding with maximum torque output.

It is because of the higher flows created by high rpm that performance petrol engines place so much emphasis on flow through the heads etc.

That's why I specified boost in my example - thinking positive manifold pressure should remove throttle and manifold vacuum from the argument.

You're saying petrols need MORE air than diesel - I'll let you take it up with kempster.

Cheers,

Scott