3k Compression Ratio

[Pongwow!]

hey all,

 

I'm currently running a compression ratio of 10:7 and we have been told we can run higher by our Dyno bloke??

How high would we be able to go?

 

Thankss

[Redwarf]

What fuel are you/ do you want to run?

[Trev]

The N/A VG30DE has a C/R 10.5:1 and runs happily on 98, anything over 11 and you are in methanol or toluene mix territory.

[altezzaclub]

Altezza runs 11.5 to one straight from the factory. That's what VVTi does!

 

What do you want the car to do?? If you are racing it then 13 to one is possible, but it won't last long.

 

We had a couple of racing heads given to us for the rally car but we couldn't keep them together. You work a motor harder for longer when you're rallying.

 

Road use and weekend warrior stuff would be OK at 11 to 1 as Trev said. I don't know when the valves will hit the pistons for you, it depends on what cam you're using & how its timed.

[Clapped out]

I'm running 13.1 ratio in my 3k, 98 plus a few bottles of octane boost! Never runs right and hard (almost impossible) to tune unless on methanol or the sort,

 

cheers phatke30!

Edited September 4, 2010 by phatke30

[Pongwow!]

Yeh thanks people its for speedway running on bp 98 and we been told we can go up to 13 but dontt expect the motor to last long.

 

thankss

[Trev]

I'm running 13.1 ratio in my 3k, 98 plus a few bottles of octane boost! Never runs right and hard (almost impossible) to tune unless on methanol or the sort,

 

cheers phatke30!

 

I would be careful as you can overdose the mixture with octane booster which will make it lower the octane, ever wondered why people don't just use straight toluene?

[Pongwow!]

we got told by the dyno that its better to use no octance boost because it does somthing to the spark plugs??

[Trev]

we got told by the dyno that its better to use no octance boost because it does somthing to the spark plugs??

 

Not so much the plugs but it can mess with the tune, you can see orange spots on the plugs when you use octane boost.

[Pongwow!]

yehh new it was somthing like thattt anyways the more we go up in compression the more we back of the timing? correct??

[altezzaclub]

Yes- pinking is always the killer..

 

How about a knock sensor kit from an electronics shop. At least you will hear it pre-igniting on a dyno run.

 

I assume you still have a mechanical dizzy/ignition on it, so you can alter the weights & springs to give the curve you need.

[Redwarf]

Of you want it to be reliable, leave it where it is. 10.7:1 is fine.