turbo experts

[aarion]

Hi, i have been hearing ppl saying about lower compression and upping the boost. But have to loose torgue. What about up the compression and maintain the boost? Will this give good power too? eg. stock comp. is 8.5, up to 9. and stock boost, will this not give any performance gain? or maybe up the boost by 0.2 bar with 9:1 comp. Isn't this better for overall performance?

Instead of lowering the comp. to maybe 8 or 7.5. and up the boost to 1.2 or 1.5 bar? Sorry if it may sound stupid. I'm just wondering. I'm new with turbo stuff still learning. B)

 

[flamefox850]

yes. u can do that, but i can't figure it out how much comp ratio u have to raise, how much thick metal gasket should use and boost..and so on. can't calculate.
but the theory u use has been available in most stock turbo cars. the benefit behind this is...u have a very smooth torque and HP curve..ur car dun jerk (u can say tersentap) on a sudden flooring the throttle, but u have an instant torque at the low RPM and u can use lower RPM with high gearing without jerking. BUT remember to use small/medium size turbocharger. with this specs, u can't use high boost and the peak torque and HP is not quite amazing

if u use big turbo, low comp ratio and high boost, u can have a high power (at the highest boost achieve), high torque and a pitchy torque/HP curve. and ur car is like no power at all at low/mid rpm...and suddenly on high rpm it is like a rush, suddenly become powerful, like a wild buffalo (ayat majalah :lol: )

 

[Hmark]

People seem to prefer to boost it over rather to compress it because if you want to play it in compression , things can get really tricky.

I suggest you to work with various boost before work on the compression. beside boosting is much faster and cheaper to play with. :lol:

 

[vestax]

fueling plays an important role :lol: rather then boosting up the car

 

[f8.]

the problem with high compression and high boost is that the engine will knock with much less ignition advance than before, especially with standard petrol where the octane rating is not so high. you have to map the car very carefully and give enough safety margin for changes in conditions such as temperature and fuel quality, otherwise there is a great risk that the engine will succumb to damage due to knock. if you don't even have a fully programmable ecu, ie running stock ecu with piggybacks then this shouldn't even be attempted.

high compression and relatively high boost(0.9-1.2bar) can work well, which is what you get with many modern turbo cars like the saab 9-5 aero and porsche 911 turbo. it gives good response even before the turbo comes on boost and quick turbo spool up. however, if you want much more boost, there will come a stage where with the standard fuel, you have to retard ignition so much that in the end, you would have gotten more power with less compression, more boost and more ignition.

basically, high comp. and high boost emphasises the need for a good ecu and tuner far more than low comp and high boost.

 

[SDF]

f8 must be horny lately...all da porno stuff on his avatar n sugnature !! hahaha.... :P

 

[navigator]

sadly, it's hard to find a mech that can extract out da max power for hi comp + 1.2bar..... although it's possible and seen in some exotic cars...

 

[SDF]

hmm...extracting power also depends on wat goodies u got in ur car for the TUNER to use as his tools....

;)

 

[cmng]

SDF
i disagree that statement

it depending how thick the owner wallet

;)

 

[f8.]

Originally posted by sum-dum-fuk@Jul 3 2004, 02:01 AM
f8 must be horny lately...all da porno stuff on his avatar n sugnature !! hahaha.... :P

wei milf hunter er hem er hem i guess i don't have to say more lah heheheh.

cmng,
money + no knowledge = the best customer in the world.

money + no knowledge + internet connection = forum champion.

no money + no knowledge + internet connection = http://www.winternet.com/~mikelr/flame61.html

money + knowledge = http://www.exvitermini.com.

no money + no knowledge = pitiful f8.

 

[cmng]

Originally posted by f8.@Jul 5 2004, 12:49 AM
no money + no knowledge = pitiful f8.

F8.
wondering who going to believe you for this word
:lol:



:huh:

:o

:lol:

 

[Torment]

ha ha, definately not me! :lol:

 

[SDF]

f8..

..|. .|..


:lol:

 

[ShaunSG]

The real problem with high boost high compression is how the knock is dealt with. Retarding the ignition you do move away from knock, but the engine is now very inefficient because peak cylinder pressure is not in the sweet spot of 10-15 after top dead center. Useful work from the burnt mass goes down, and EGTs go up as fuel completed burning closer to exhaust valve opening, or even beyond it and into the exhaust port/system.

So for a race engine, the only real proper thing to do is properly match compression to boost and run optimal ignition timing under load. Everything below that just has to be compromise (spool up and power wise). The driver has to work hard to keep revs up and reap the rewards of a powerful and thermally/fuel efficient engine. If you want to create a high compression engine and hope to boost it high to get both great response down low and big power up top, it just isn't going to work. You have to build and tune to optimize for the range that is truly important.. and in most performance and racing, it is the upper RPM, high load ranges.