Dazz01

Hey all,

I was just wondering something, does a smaller capacity engines affect turbo efficiency in terms of spooling times etc?
Also with a smaller engine would you require less boost to acquire the same amount of compression form a bigger engine i.e would the EJ20 require less boost than the EJ25 would require to get the same power results because I would have thought if 15psi of boost went into both engines, the 2.0 would have higher compression therefore more power (however the EJ20 would probably have a harder time getting the boost than the EJ25).

Cheers, Dazz

boosted

Hi, power has nothing to do with compression.
The bigger engine will always make more power and torque at the same boost level as the smaller engine.
A bigger engine will spool a turbo sooner than a small one due to the increased VE and exhaust volume, however too small a turbo on a
Big engine will restrict maximum boost and rpm potential, ie the turbo need to be big enough to flow the extra cfm for the extra flow of te engine.
Bigger is always better

SmurfyBhoy

Surely it must ?

High and Low Compression at same boost must make different power ?

I thought it was as simple as half the compression double the boost kinda thing

Like Speed,Distance,Time ???

gazney101

iTrader: (5)

Lower compression allows a little more boost and a little more top end power but compromises a little spool and response.

Higher compression is limited by det

SmurfyBhoy

Be good if an engine builder could explain it a little better ?

Must be benefits and downsides to both.

Or failing that good old google always helps

RS_Matt

Unequal compression, any benefits?

SmurfyBhoy

Lol

gazney101

iTrader: (5)

It's not that difficult really, an engine with really low compression will be fairly dull and slower to spool a turbo and have a lazy transient response but will make high top end power for the applied turbo.
A higher compression will be more urgent and responsive.

The higher the compression the closer you get to the knock threshold so it limits the amount of airflow it will swallow

gazney101

iTrader: (5)

If blow by or leaking valve seats are your goal then yes, mucho benefito

boosted

What do you need explained better? The op was saying that a smaller engine has a high compression ratio and this makes more power with less boost. Not one piece of this information is correct.
His conception of adibatic compression vs static compression is a bit mixed up, then even further adding to the mix up engine size and spool rate.
So to summarise you want the biggest engine with the highest compression ratio and smallest turbo with the best quality fuel and intercooler to make the power you desire. This will yield the best response and effecientcty possible.