Octane ?

[zoomer]

What do I need to run for octane with a 25 series Boondocker turbo and a headshim?

1400ft 8lbs= ?
1400ft 12lbs= ?
6000ft 8lbs= ?
6000ft 12lbs= ?

If I'm using the boostcalculator right
a 0.057 headgasket (headshim?) gives me 10.08 comp

1400ft with 10.08 comp at 8lbs boost needs 87.6 octane?
1400ft with 10.08 comp at 12lbs boost needs 92.0 octane?

6000ft with 10.08 comp at 12lbs boost needs 90.1 octane?
6000ft with 10.08 comp at 15lbs boost needs 93.4 octane?

Is that right? Am I using the boostcalculator correctly?

 

[zoomer]

Here is boondockers chart. Using the boostcalculator these octane requirements seem higher. Is that just for Boondocker to protect themselves or what? Please explain. Thanks.

 

[JIM]

did you change your cam timing? that has a huge affect on how that chart reads. what are your lobe centers at now?

 

[zoomer]

I have no idea on the cam timing. I'm looking at buying a sled with it already turbod and a headshim.

 

[TomKat]

Look at the boost calc in the thread. Make changes to allow for your compression difference and it should lead you in the right direction. Good Luck! http://www.ty4stroke.com/viewtopic.php?t=23214

 

[zoomer]

That's what I used to get the numbers in my first post. My ? is did I get the right numbers using 10.08 new compression? And why are the numbers so much lower than Boondocker recommends?

 

[JIM]

I think their kit has a log style header and creates alot of heat and needs more octain to be safe. It you set you cam timing on the chart you will see it needs more octain if the cam are not set at 114. In the chart you need play around with the "intake valve close abdc" it should be 58 as exsisting that is the stock number and 71 as new is if the cam are done for boost. set them both at 58 and you will see it needs alot more octain. you need to know these things to make an acurate octain estimation.

 

[zoomer]

I still don't understand how to use the boost calculator.

I tried changing the "intake valve close abdc" both to 58 and it didn't change anything.

So I take it just used boondockers chart as far as what octane would be needed? Would I go by the 9.0:1 since it has a headshim? Or somewhere in between the 11.8:1 and 9.0:1?

 

[zoomer]

Also can you run leaded race fuel? Or should it be a unleaded race fuel?

 

[TomKat]

You can run either one. Most around here run the leaded version. The one issue it can cause is to foul the O2 sensor after a while. According to Bosch I think it like 5-10K miles or longer.