trinydex

iTrader: (12)

was waiting for you. what's "low boost" kakakaka

Aby@MIL.SPEC

iTrader: (161)

~5 psi = rules.

trinydex

iTrader: (12)

oh... that is low boost :[ so you guys up the compression to compensate? or is there a difference reason to up compression? is there a cap on compression ratio?

BenJ

iTrader: (21)

if were talkig about keeping things streetable, lets not forget that extremely high boost and compression ratios equals frequent rebuilds of the motor But if not then I'm all for it

EVO8YOU

A proper designed high compression turbo engine has a couple advantages over a lower compression one. It will spool the turbo quicker, It will make more power all the way to the peak horsepower level, especially off boost and during spool up. It does however give you alot less margin of error on your tune. Its really not worth doing on a "street car".

feldguy

iTrader: (4)

I didnt read the whole thread, but it is also noteworthy that the bump in compression is necessitated by ethanol's difference in stoichiometric ratios to make the same power. As we know, gasoline is 14.7-1
Ethanol is 9:1
Methanol is 6.4:1

So you either need to burn the fuel 40% more efficiently by adding pressure to the cylinder bia compression turbo, or supercharging...or you need to add 40% more fuel, and in a performance aspect, methanol is great because it does burn cooler than gasoline, by I can't remember my numbers.

I used to fly R/C helicopters and soon changed over from nitro model engines to zenoah weed whacker engines....and they ran so hot due to the confined spaces, I had to switch back to alcohol with oil mixed in, essentially a nitro engine. I soon switched from methanol to ethanol, after I was burning more than TWICE the amount of fuel with methanol, and much less with ethanol.

It burned cool, clean but the performance was notably lower until I added a high compression piston and leaned things out a bit.

Ted B

iTrader: (6)

I wonder where people get this? In fact, the effect on spool tends to be the opposite.

VRSF Tiago

iTrader: (138)

Really? I thought I remembered reading that you spool would benefit from a higher compression ratio.

Would you mind elaborating a little?

Ted B

iTrader: (6)

Higher SCR (static compression ratio) benefits off-boost response somewhat, but lower SCR is less thermally efficient, which tends to raise EGT. Higher EGT equates to greater exhaust gas energy, which spins the turbine faster. We're probably talking about peanuts with a SCR difference of one full point or so.

EVO8YOU

The VE of the engine changes with compression. If you have a higher compression engine at the spooling RPM the engine will be making more power, and correspondingly moving more air. Hence the quicker spool. The real issue with any engine combination is how does one wish to taylor the cylinder pressure. After the blow down stroke the rest of the stuff is meaningless for spool up.

Ted B

iTrader: (6)

That is incorrect. Compression itself is not directly affecting VE. The higher compression engine will make slightly more power using the same volume of air, but better thermal efficiency means lower EGT, all else being equal.

trinydex

iTrader: (12)

compressions doesn't affect the ve and if you'd like to say that it is the way it affects ve would be that the higher your compression is the sooner you'll reach knock and the less air you can cram (boost).

turbo motors running higher (by higher i mean lower number) afr should already suggest that they run hotter. plus more fuel means more gases to move the turbine wheel.

it might feel better at the low end in a response kinda way and the enhanced n/a characteristics of the motor may make it feel quicker on the low end.