Compression

[utah_sledder]

So what is your opinions on compression? I have a 2008 T-XP 800r. It has a Turbo Performance Aero 66 kit. It currently has a 10:1 low compression head on it. I have the turbo set up to run about 6 lbs of boost on 100% AV gas. I have been toying with the idea of running the stock compression head.

It feels like I might be able to gain some bottom to mid with a little more compression, but I am not sure. It doesn't love to idle real well either.

So help me out here...low compression or not?

 

[Boyko]

What altatude do you ride at, is it the 66?

 

[Silber]

if your running 100% av gas I would go back to stock compression, you are way safe with them low boost levels. I would get some stock heads, which will make your bottom end response better again, and you can probally add a few psi of boost too depending on altitude.

 

[utah_sledder]

Yep Aero 66 kit. I ride 7000-10,000 feet. I have an extra stock head so I have been toying with the idea of switching to the stocker. What about pump gas, 6-7 lbs boost, stock head?

 

[tukernater]

one thing at a time. just saying

 

[Silber]

on pump gas you might be on the edge. I would just lean it off the av gas alittle at the time and see how it runs. Make sure to check your plugs and wash alot to make sure it doesnt detonate.

 

[Boyko]

I do not know how your availability and pricing for AV fuel is for you, I like the stuff. It is only .10 more a liter here in Alberta over the not trustworthy 92 octain, that is the biggest downfall for pump fuel is getting a slug of under octane fuel.

AV fuel has a different specific gravity so you might have to change your low end jetting if you go to pump fuel

With AV fuel I am running 10 psi at 2400 feet and 12 @ 8000 with a cut head on a M-1000 and 8psi on a dragon @ 2400 with the stock head, 15psi on the yamahas with shims no worries so far.

If you could I would stick with AV fuel and turn it up a little, at 6psi the thing is just stating to wakeup, changing the head it is kind of a trade off between response and boost

As Sibler said just watch out for deto either way

 

[brycter]

if your sled is not idiling very well check your exhaus bellows. if they are leaking or have a hole in them you will lose bottom end and throttle response.

pilot jets are you running? and what mains?

you will be ok with pump gas at 6psi on the stock head but not to much more than that.

 

[utah_sledder]

if your sled is not idiling very well check your exhaus bellows. if they are leaking or have a hole in them you will lose bottom end and throttle response.

pilot jets are you running? and what mains?

you will be ok with pump gas at 6psi on the stock head but not to much more than that.

Thanks Bryce,

I am running 15 pilots, 320 mains.

I have just been curious about the effects of compression on a boosted motor. I am not stuck on running pump gas, I can get AV or Race fuel easy enough.

This is my first turbo'ed sled so I am going to be doing a lot of testing this fall. I just want to be geared up with info so I can make the sled perform how I want it.

I may sacrifice some higher boost levels by running stock compression, AV (or Race) and lower boost to gain bottom to mid. But then again the sled rips, so at what point do you just leave it alone....to me never!

Only testing will truly tell but I like to have as much info as I can before I go test.

 

[turbo800]

Utah_sledder

If your willing to run 100LL, I would definately raise your compression back up. I'm running a 800HO w/ MXZ head. If you put your stock head on, I would take ~.010" thou out of the squish band. They came with 12:1 C/R like the MXZ head anyway but have a tighter squish band (Summit).

Right now I'm running .075" thou squish & 12:1 C/R. I'm on the 100LL and run 10~12psi boost. 5000~10K elevation. At 12psi I have to be a little careful on really cold days, other than that it runs great.