[Slippi84]

Originally Posted by dsm-onster

HMMM, boost and compression only raise the rate of burn. Which LEADS to detonation. It's not that it directly causes it.

Let me say this based on your private goals which we've discussed in PM.

High CR means that the fuel/air mixture burns faster. 93 octane means the same thing. Timing the spark to the burn rate is all that's needed. Unless you're running high enough CR to preiginite the fuel (like +22:1). Then the higher CR isn't a cause of knock. A timing curve that doesn't go along with the faster burn rate is a cause. Pulling lots of timing retard with a fast burn rate doesn't lose lots of power. Infact, firing the air/fuel mix later because you have to time with how fast the burn rate is just means their is LESS pumping loss, resistance to the piston, during the compression stroke. The compression stroke shows the most pumping loss and affecting the loss here does the most. So full timing control and high compression with a good tuner or plenty of dyno time will net you higher Brake Specific Fuel Consumption.

The same goes for boost in a lesser sense. Buscher boasts of running gt35R powered evos with +8.8 CR with pump gas and 30 psi using apropriate timing changes. High power is still there even with HIGH timing retard.

Higher BSFC means more power per unit airflow or fuel flow. This is where big pumpgas numbers can be seen. Less boost or airflow is neccesary to achieve a certain power.

A better flowing turbine will net more power without the need to raise the boost because thesytem VE goes up. Better VE means less pumping loss AND more air without heat ,which high boost yields. But as mentioned, this means lag. A twinscroll setup will negate alot of the slow spool. Also, a very efficient turbine wheel and compressor wheel will negate slow spool because not as much turbo rpms will be needed to reach a certain flow. An efficient pair of wheels will also assist in peak flow, overall VE, pumping loss, and BSFC because more gases can be simply shunted to the wastegate uninhibited.

IMHO, you're on the right path as you are looking at the more efficient borge-warner and holset turbos. A more efficient engine (high CR, high VE, low pumping loss) loves an efficient turbo. Without an efficient turbo, it's pretty difficult to show the benefits of the efficient engine. This is why many tell you to run low compression with high boost and high timing to achieve mid/high power. They don't choose an efficient enough turbo.

Yeah but even slowboy with their shop evo with 10:5:1 could only squees 15psi out of their old borg setup and like 19psi out of the new setup? I would love to run 20psi because I know at 20psi with my compression this turbo would be everything I need it too. Maybe with A LOT of timing pulled and meth I might be ok but not running enough timing will make it spool slower unless I lower it so much that egt's raise and then it would spool faster.