Boosted Compression

[bholmes]

I was just curiouse what alot of you boosed guys are running as far as dynamic compression ratio. Also what type of chage cooling are you using for your set up? Intercoolers, meth/water injection, etc?

This is a calculator to calculate the dynamic compression

http://www.wallaceracing.com/dynamic-cr.php

Any here is a link to the stock camshaft profile of the 951 and 944's, some info from it is needed for the calculation.

http://members.rennlist.com/951_racerx/ (go to camshaft diagrams)

Thanks for your help!

[bholmes]

anyone?

[legion]

I'm completely stock in that department.

[blown 944]

using this formula at 5800 ft and at 12psi

I'm at 13.37:1


specs as follows
bore3.94
stroke 3.11
rod length 5.90
9.7:1 factory compression
12psi boost
intake closing @49 Deg

However the air generally measures to 7500 ft and higher so it comes out to 12.77

At sea level it comes out to 15.49

I ran some fantasy numbers @ 25 psi on 9.7 @ 7500 and it comes up to 18.99. for this some custom pistons and other mods will be necessary I'm sure.

What I will probably do is to run some turbo pistons when I go the high boost route

It appears tat to get the same erformance I am getting at sealevel 8 psi would work.

There are o many other variables as to how an engine will handle the pressure thoughie: fuel, timing... condition,etc

thanks for the links

[bholmes]

http://www.turbofast.com.au/tfcalc.html There is another fun calculator, it's for turbos, but i'd say you could plug in the right SC numbers and get a pretty accurate estimate on HP. Looking at your dynamic compression at sea level I think with your current set up you might experience some detonation LOL.

[bholmes]

By the way, length on our rods are 5.906" according to rods available from Lindsey Racing.

Legion, I calculated your dynamic boosted compression ratio for 500ft and it's 12.64 :1 thought you might want to know. This is assuming 12psi of boost, which I think is the max that a 951 sees in stock trim.

[bholmes]

Just comparing numbers Sid, looks like you are almost dead on with the upper end range of the 951, however with more bottom end naturally due to the SC. At least with the 7500ft calculation. Either how, that's nice to know.

Does anyone have any clue what kind of max dynamic boosted compression you can run provide you have control over timing etc. WITHOUT detonation?

[legion]

Originally posted by bholmes
Legion, I calculated your dynamic boosted compression ratio for 500ft and it's 12.64 :1 thought you might want to know. This is assuming 12psi of boost, which I think is the max that a 951 sees in stock trim.

Thanks!

[ilikemy944]

Mine said 16.16:1

[bholmes]

Holy Crap!!