8.4:1 compression

1. gixxa Established Member Joined: Feb 2007 manchester Posts: 1704 vtr turbo

   #1 3rd August 2009, 21:36

   how much boost could a safely run on the above compression ratio, ive run a bar on a higher compression ratio and it seemed fine but just wondering what I could in therey safely run
2. user_15989 Saxperience Forum Bum Joined: May 2007 Posts: 4857

   #2 3rd August 2009, 22:37

   Sorry to say there is no answer persay. It really depends on how the boost is introduced, how good your fulling is controlled, how lean your running, the fuel your using, how good your ignition is controlled, what plugs your using, how good your water cooling is and a many other things.
3. gd16 Frequent Poster Joined: Nov 2003 Tayside Posts: 893 S/c VT!?

   #3 4th August 2009, 00:10

   Ditto the above.
   
   Its not the boost pressure that kills things, its the extra heat thats introduced because of the boost. So saying '1 bar of boost will be fine' is a completely misleading statement.
   
   Saying '1 bar boost will be fine' as long as the inlet temps never rise above 30 degrees, the ignition/fuelling is set up correctly, temp corrections for water and air are in place, etc etc is still a misleading statement, just slightly less so.
   
   Plus you ask 'safely' - safely for the engine, or safely to put the power down? Power delivery on a turbo will be harder on the transmission than a s/c, but either way you'll need to worry about a lot more than just how much boost you should limit it to in order to be safe, you'll need to think how you'll make the power usable/safe at that boost limit too.
4. luthor1 Established Member Joined: Jan 2008 Posts: 1802

   #4 4th August 2009, 02:12

   The answer is you monitor the air intake temp just before the butterfly, you measure the Exhaust Gas Temp, the AFR, and listen for detonation using DET cans.
   
   While all those factors stay within acceptable limits, increase the boost. When one of them goes wrong, lower the boost.
   
   All that is presuming the hardware you have is physically capable of taking the strain.
   
   Note well the comments regarding transmission etc, and always remember: tyres, brakes, suspension THEN power is the safe way to do it.
   
   Andy
5. gixxa Established Member Joined: Feb 2007 manchester Posts: 1704 vtr turbo

   #5 4th August 2009, 07:45

   is there any way of monitoring the intake temps, you last peice of pipe work before the butterfly is allways cold to touch after giving it a blast.
   
   How does EGT effect things?
6. Ste Saxperience Post Whore Joined: Mar 2007 Yorkshire Posts: 5415 Saxo

   #6 4th August 2009, 11:37

   Just so you know, theres a TU running 24psi of boost making over 300bhp with that compression. But it has custom everything and you need a new ignition to run that high boost.
7. gd16 Frequent Poster Joined: Nov 2003 Tayside Posts: 893 S/c VT!?

   #7 4th August 2009, 13:40

   Quote:

   Originally Posted by Ste Just so you know, theres a TU running 24psi of boost making over 300bhp with that compression. But it has custom everything and you need a new ignition to run that high boost.

   There's also a TU engine running about 14psi of boost, running more than 300bhp@wheels. And its running near standard-ish compression AFAIK.
   
   Just pointing out you don't need ultra low compression, or high boost figures to get big power.
8. luthor1 Established Member Joined: Jan 2008 Posts: 1802

   #8 4th August 2009, 16:45

   I like high compression, relatively low boost since it drives much nicer with a better bottom end power delivery...
   
   Andy