Quote:
Originally Posted by Piwoslaw
I've been thinking about the freer flowing intake today. I don't know about the TDI turbo, but my HDi's turbo has variable geometry, and this lead me to a thought experiment:
The ECU is constantly checking boost pressure and tweeking the turbine's geometry to keep boost where it is supposed to be. So if the pre-turbo intake is opened up (less restrictive = lower pressure drop = higher pressure delivered to turbo) the ECU adjusts geometry to 'scoop up' less. Post-turbo pressure is the same (ECU made sure of that), but the turbo is doing less work, i.e. less work is extracted from the exhaust.
So, opening up the pre-turbo intake has the same effect as reducing exhaust back pressure. And is probably cheaper.
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TDIs have VNT turbos.
My thoughts have led me to conclude this won't work. The inlet side is cancelled out by the turbo - it boosts to the same pressure as long as enough air is coming in. If you improve it then it makes no difference.
The same for the exhaust - remember better exhaust flow only works for high-revving petrol cars. The exhaust diameter on my TDI is larger than any petrol car I have ever had.
Nope - this engine has all the air it needs. I still maintain if Julian removed everything else and kept the remap the power gains would still remain.
I'm willing to bet a bottle of wine on it.