I was talking to a mechanic about dynamic compression many moons ago and how exhaust gasses effect turbo spool etc and I just wondered if a Subaru with low compression kept in the powerband would be faster than a Subaru with no compression losses?

I.e if two STI's were launched at 5,000rpm would the knackerd one leave the healthy one behind?

I've pondered the question for a while but was always embarrassed to ask.

 

 

What makes me ask is that my car doesn't hit boost until 4,000rpm but when it does it's an animal, my mapper thinks my turbo is lazy but I think it's due to the fact I've barely 3 cylinders in CC.

I think once I make power the plume of emissions is like NOS for the Turbo. The last time I ran the 1/4 mile my back bumper partially melted.

Am I right in thinking running a turbo engine slightly rich isn't just for cooling benefits?

 

Ill stick my neck out and say a knackerd Subaru is defiantly going to be slower then healthy one

 

Matt have you thought about starting all your post's with Once upon a time and finishing them with The End.

 

lol.

Is soot the main reason why Diesels make boost so low in the rev range?

 

Sounds like you've inhaled too many gases Matt.
Got to be one of the strangest questions I've ever heard,and you do ask some strange ones lol

 

I was just thinking about exhaust gases dictating how fast a turbo spools up and it did make me wonder what happens when you have excess exhaust gases from burning oil etc.

Would extra gas make a turbo hold boost better?

 

If you are saying because you have a low compression ratio due to wear, then no, because you will lose good compression made up by the turbo down the bore or valve wear. But the lower compression with piston or thicker gaskets, the higher and bigger boost you can run.

One of the first turbo a BMW 2002 ran low compression and a big diesel truck KKK turbo that was the same ran like a 1600cc car till 4700 rpm then all hell broke lose.

The melted bumper sound like valve leak and turbo turning in to a flame thrower (overboost) think your engine is on borrowed time.

 

 

Dont talk daft.

now if it was a wrx with a duff engine its gonna be faster than an sti anyway

 

What about a 3 cylinder sti? Do they get the same "boost"?

 

I was told in 2008 it had 6 months life left. Basically a few mechanics have told me over 4000rpm dynamic compression means the cylinders technically seal themselves and power is restored but you still get the added benefits of burning oil that seeped into the cylinders, almost like a poor man's antilag.

 

What rev range?? 1-4k

 

Got to be one of the best posts on here in a long long time
Keep up the good work Matt

 

There are literally no words!

Could an OP please close this thread? This threads plumbing new levels of stupid and im concerned it may be contagious.

 

Can your mechanic fit me in come pay day?

 

They are if i'm selling one.

 

This is a new level of stupid.

 

...

 

So if you get some 91mm pistons instead of 92mm and *** the rings off You can get extra exhaust gas and lower compression. Don't worry about the oil Wow quote of the day "the poor man's anti lag"

 

It must be even harder for the STI boys knowing a shagged WRX is beating them at the lights!

....with less power and compression!

Joking aside we`ll just all asume compression losses make no discernible performance increase.

 

Glad I never mentioned dirty uneven compression!

 

Once upon a time....

Oh dear Matt.

If an engine is designed to have low compression then the chambers in the head are opened up or a thicker head gasket used to increase the chamber size and lower the compression in general. In normally aspirated cars this will decrease the power output. However in turbo'd cars this means you can run more boost and actually achieve slightly more power before you damage things beyond repair.

HOWEVER.... if your car is naturally exibiting lower compression from wear rather than by design then it will be because of piston ring wear/failure. The compression gasses will be lost down the bore and you will not achieve more power.

So in the answer to your stupid question.... NO. A f****d engine will not be faster than a good engine!

Please close the thread.

p.s. there was no need to dig & jab an argument provoking STI - WRX comment in your thread Matt. That's just plain trolling on your own thread!

The end.

 

No wonder scoobynet is dying on its ****

 

BrownPants, your a braver man than me.

I wrote quite a long ranty reply last night about what ***** Matts going on about, but got to a point where I couldn't be arsed to post it as I couldn't dumb it down enough.

Matt, you cant keep popping up on here with uneducated and unfathomable theories based on your interpretation of completely misunderstanding what someone might have said many moons ago without coming across as a prize plank.

 

I could have written a much longer reply going into more detail and explaining it to him in more depth, but quite frankly I suspect it would still fall on deaf ears.

Some 20+ years ago I was playing around with race prepared minis including a classic MK1 mini turbo (one of the 1st built) to understand compression, effect on boost, methods of raising boost, extracting power etc etc and using a book that Alan Jeffery was published in even back in those days (allbeit in black and white). Always best of you find these things out for yourself or talk to someone that understands it.

I suggest that Matt goes to Plymouth and has a cuppa with Alan and a nice long chat about his WRX theories.

 

I put a rod through a block, it wasnt very fast after that

 

Did it affect the compression at all?

 

Raised compression