themacuser.org

hahahahahahahahahahaha. you rock.

MIGHTYMOUSE

on pump gas you can definitely make more torque by lowering the compression.

on 115 or higher octane, the static compression ratio starts going out the window and you get people like above running over 10:1

my motor is 8.75:1, fairly low compression, just like any aftermarket or factory engine ever designed to work well on pump gas forced induction... thats just how it is.

google

Thats why if you run a high comp setup youll need to either have a awesome tune and a rich map, or retard the timing enough to escape detonation problems.

EEK

the type-R turbo from my crew, has a 96 itr motor jspec(all stock internals), 3mm headgasket by inline and its tuned by inline..i believe compressions is 9:1...he dynoed 327@12psi

Boosted2003

Yeap, Everyone makes it alot easier then it really is.

SCOOBY STEVE

thanks guys

now that i have a platform to work with, im looking at every angle

B16bEJ1

hahaha my turn im thinking about boosting my jdm b16b any thoughts on that? the compression is 10.8:1most say that is too high i was thinking like 7 or 8 psi? thoughts?

keyd

"By reducing compression, thereby increasing combustion chamber volume, we have provided more room for more mix to occupy...Not only is it obvious this additional amount of fuel will now be capable of a higher force generated once ignited, but less obvious is the sheer amount of additional mass in itself provides a cooling effect of the end gasses left in the combustion chamber and a denser inlet charge of the remainder filling it... This is the basic fundamental reason for elevated output when utilizing forced induction principles." -Joe Sumen or Corky Bell (can't remember which)

Anyway, a friend of mine used to work for DME and years ago they analyzed a 2.3 liter Ford SVO motor for turbocharging...I saved all the data as it was VERY good stuff. It dealt with the whole boost/CR/Timing issue..

10.3 to 1 compression
92 octane
188 @ 6700
A/F 13.6-13.8
35 BTDC

Turbocharger installed..
10.3 to 1 C.R.
92 octane
236 @ 6500...Ping caused boost limiting to 5 p.s.i.
35 BTDC
A/F 13.6-13.8
Timing retarded to 30 BTDC
Richened mixture to 12.7-13.0
Allowed boost increase to 7 p.s.i.
279@ 6500

Further reduction in ignition timing in attempts to apply more boost became futile as the exhaust gas temps rose dramatically with less than 2% per lb of boost increase.

Next they ran the motor on 116 octane sunoco race fuel...This is pretty amazing..

They kept feeding more and more boost and just kept making more and more power..Finally they had to install secondary injectors and change to a loose scroll huffer...

From 7 p.s.i and about 280 h.p they were able to pump in 23 lbs of boost and made 522 H.P.!! This was with 32 degrees of ignition..

Next they rebuilt the motor with 6.8 to 1 slugs
The curve below boost was lazy so they remapped the ignition curve to feed more timing down low maxing out at 35 degrees again...

Now they could feed 33 p.s.i. into it and H.P. shot up to 639@7700.....

So if you can determine the boost, CR, and timing in your engine - why would you run a CR based on what someone else said worked good for them unless they have the exact same car and goals as you?

What are you doing with your car? What's your driving style? Are you shooting for all out HP with some track time? Is this a daily driver that you want to be able to gets some extra power when you need it? Are you concerned about mpg?

Higher CR means you can't run as much boost and can't make as much power once you are on spool. This is established fact. It also means that your car will be more sluggish when off-boost. You can advance the timing (off boost) to compensate and it will also make your car spool up faster but is that what you want? If you want maximum HP then go lower CR. If you are rarely on boost but want some power when you need it and are concerned about mpg then go higher CR. Or find a happy medium inbetween. Don't just run a CR based on whats good for so and so's car or just to be different.

Now what I am NOT saying is that an engine with 2:1 compression and max boost will make even more power. We are dealing with a bell curve, and power/efficiency will drop at either extreme of the curve. The application is critical to what you want to achieve, there are many examples where an engine with more HP will lose the race, since the transient response "can" have a huge effect on lap times. It doesn't matter in a drag race when you know (more or less) when you have to take off, but it's another story entirely on a road course, or even worse on the street (when you don't know when some wanker is going to challenge you, you'll know when he's pulling away, and the faster engine is the one that responds RIGHT NOW instead of waiting to come on boost).

Captain RS

i like the lower comp. bigger boost myself. no chances just boost. lol

boostjunkie

changed my mind....



10.6:1 compression...