why people have to lower the compression of the enigne when they add turbo?
sorry for noob question

 

It's provides more of a safe-range when tuning for a turbocharged motor. Lower compression lessens the chance of detonation.

here you go:
https://honda-tech.com/zerosearch

 

you dont have to lower the compression....the reason why we lower the compression is because we are limited by the amount of octane available on the streets, the higher the compression you use the hotter your combustion chamber gets, if you run a turbo on that, you will have more heat in the combustion chamber....then you will need higher octane that doesnt pre-ignite at certain pressures and heat...

alot times you dont really need to lower the compression ratio, unless your car came with like 12:1 from the factory or something.....

when choosing compression ratio for a turbo car you are making a compromise..either high compression and low boost....the turbo will spool a bit better..(high meaning 10:1-10.5:5)
but you will have to have the engine tuned well so you dont get detonation

or lower compression compression ratio higher boost, and a slightly less chance of getting detonation.

 

so the higher compression the engine, the lower boost = less power
and the lower compression the engine, the higher boost = more power?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOL-R &raquo;</TD></TR><TR><TD CLASS="quote">so the higher compression the engine, the lower boost = less power
and the lower compression the engine, the higher boost = more power?</TD></TR></TABLE>

yep

 

There is a fine line between maximum performance and breaking stuff. By running a high compression ratio and decent to high boost numbers, you are pushing closer and closer to this line.

Some NA racers are running insane CR's [I think Bisi is running something like 15:1], and it takes incredible tuning to keep from blowing **** up at that high of a CR. When you add boost, it compounds the difficulty of controlling your engine. But it's people like Bisi that push the envelope and are out there running 10's in a carbeurated 1.5.

Running a conservative CR allows you to crank the boost up with fairly good confidence [all assuming you are well tuned] that your motor will last.

 

thankz

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOL-R &raquo;</TD></TR><TR><TD CLASS="quote">so the higher compression the engine, the lower boost = less power
and the lower compression the engine, the higher boost = more power?</TD></TR></TABLE>

honestly that can go either way......with higher compression it will take you less boost to reach the power goals you are shooting for, but you run much more of a risk of blowing something as to lowering the compression and running more boost is somewhat safer.......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOL-R &raquo;</TD></TR><TR><TD CLASS="quote">why people have to lower the compression of the enigne when they add turbo?
sorry for noob question</TD></TR></TABLE>

b/c race gas is expensive

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOL-R &raquo;</TD></TR><TR><TD CLASS="quote">so the higher compression the engine, the lower boost = less power
and the lower compression the engine, the higher boost = more power?</TD></TR></TABLE>

it's more like higher compression engine, lower boost = lower compression engine, higher boost

the difference is going to be in things like where the turbo starts to spool and where the power band sits in the RPM range.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Haberdasher &raquo;</TD></TR><TR><TD CLASS="quote">

it's more like higher compression engine, lower boost = lower compression engine, higher boost

the difference is going to be in things like where the turbo starts to spool and where the power band sits in the RPM range.</TD></TR></TABLE>

not really..... we made 500hp on pump gas.. granted the engine had 7.8ish:1 compression.. you're not gona do that with a 10:1 motor