Here is some food for thought, I know this doesn't exactly relate to the boost question but it may help.
The first three are just some DCR calculators and the last may be helpful or just a pissing match because I didn't get too far into it.
https://ls1tech.com/forums/showthrea...hlight=dynamic
https://ls1tech.com/forums/showthread.php?t=512946
http://www.kb-silvolite.com/calc.php?action=comp
https://ls1tech.com/forums/showthread.php?t=305151

 

9.5 is way too high for a stock engine to run even w/ premium. There was a thread that said basically the stock LS1/LS6 was around 6-7.5 DCR stock. If I knew the cam numbers at .006" for the stock LQ9 cam I could try and figure it out.

 

Yep, that's the big problem

I also found another problem. I'd done my 408 right before that and forgot to change the stroke and the rod length on the dynamic stroke form lol. Now it says DCR = 8.85 using 230/238 and 117 lsa and icl. That's better.

 

Why would a preferred DCR for a boosted engine be different than N/A?

 

I don't think it would be -- that's why I'm partially confused here. There's no way I can adjust for boost and hit 8-8.5:1 DCR at high boost. I'd need a PR of 1.45, so max boost would be 6.6psi? I make waaaay more power at higher boost, so it seems we're missing something here.

The chart Zick posted is also interesting but doesn't seem to account for good intercooling. Maybe that's the difference on the FI side since intake temp affects detonation as much as octane and DCR.

What prompted me to start this thread was trying to figure out the maximum "safe" boost I could run. Maybe I need to be looking at dynamic cylinder pressure...

 

That is the question that preoccupies our people.


Seriously though,

https://ls1tech.com/forums/showthrea...36#post4788636
SStrokerAce makes a good point. A FI engine is going to have much higher temps and I'm sure more volume from all the air its cramming into the engine that it may throw off the standard DCR rates.

 

Or you could skip all the #'s and use the old school method. Make sure you have a good stout short block then push it till mild detonation, then you back off. It has worked for years for many/most. I prefer to stick to the old methods, call me simple minded.
If you push the envelope without good parts then carniage you may have.
Although, I do find the theory of DCR interesting.
I just feel there are too many variables to start counting pennies thats all.

 

It would not be different but I think you're forgetting all the things we do to prevent detonation because we are a higher DCR with boost : race gas, intercoolers, water/meth injection, much less spark advance, 11:1 too rich AFR instead of an optimum 12.8:1, 165* thermostat, colder plugs, etc.

If you plan a boosted engine for just pump gas and driveable then it's 8:1 static CR with a bigger cam and 6-8 lbs boost and it'll be right about 8:1 DCR. If you want more then we have to do the above added things. Also keep in mind that if you plan it for very high boost near an 8 DCR the engine will be a dog while out of boost or at low rpms.

 

BOOST DCR calculator: http://www.rbracing-rsr.com/comprAdvHD.htm

 

And another... http://kb-silvolite.com/calc.php?action=comp