really, the only way we'll get an answer to this for this particular application for a particular setup, is for someone to do it
really, if anyone wants to try a higher compression ratio, i'd love to compare notes/figures when it happens
either way, it's not like it'll totally ruin the N54, at worst a little less power in the top end with some more low-mid, and probably still happily make NEAR as much power as you would stock
I mean given the MAXIMUM octane theoretically possible, an intake and turbo capable of delivering X theoretical psi and Y air flow rate (whatever you can dream of), and the stock N54 block/internals increasing the CR from an already octane limited tune will likely result in pulled timing (less power).
true, if there's a bit timing pull, any power gains are pretty moot - that would all come down to tuning though no? not like you can just throw the pistons in and leave it.
Agreed its all down to the tuning, but we're talking about compression not tuning. I don't disagree that the tuning will play a role in this, but academically there is a point where, assuming you have "perfect" tuning, increasing compression ratio is NOT a valid way to increase power. The issue now is that there is a complete lack of REAL data as far as the ideal compression ratio is concerned. While its fun to debate the academic merits of increasing or decreasing the CR, there's no conclusive evidence as to which will make the most (or best) power yet.
Bottom line is that @WDBi should spend his $$$ to experiment for us and let us know how it goes... :awesome:
lol wow this thread kinda blew up.
i was just looking around and came across this http://www.modularfords.com/f17/incr...ressure-51059/
i what im probably going to do is wait for a good turbo upgrade to come out like the vargas set and when that happens i will port my head and build the motor and possibly raise compression i have to look into it more
Obviously there are application specific concerns (what is the maximum N54 MEP (Mean Effective Pressure) at detonation for a given fuel (and stock internals)?) but this rule makes mathematical sense to me now...Quote:
Therefore, for any given fuel and AFR, etc., one can make more power & torque at any given engine speed by reducing CR and increasing boost pressure, than the other way around for the same peak cylinder pressure
Why rather than the way other around if peak cylinder pressure is the issue? Isn't it a wash?
correct me if i'm wrong, but the n54 gets on boost around the high 1xxx-2k ish rpm, and full boost 3000ish?
You'll only be better off power wise when your turbos are below max cylinder pressure, and you'll see most difference off boost, up high you'll probably have to pull timing, so almost no matter what, less up top, and maybe similar midrange at best
if you want more in the mid range and peak, bigger turbos, more boost (rb turbos spool like stock almost don't they?), cost less too.. Dzenno's recent results show slightly lower compression leads to buttloads more power and a much healthier tune.
if you want more off boost and JUST on boost, raise compression, a more pleasant daily driver, not as fast, LOTS harder to tune, less timing, less boost.
That's what i'm getting out of this.. You can't just go crazy raising compression and expect good results, where lowering makes it a fair bit easier to get more power on-boost... It's very 'what you want' specific, as to whether you raise or lower or stay stock.. Never see redline? Well kinda strange to be doing this work or driving this car, in the first place..
I'm not looking for the cheapest way to make power. And i just say stock turbos because im waiting for more options to come out. I am looking into doing motor work pistons, rods, and head work. So i can have fun on the turbos before nee options come and when those come it will be really worth it.
I really do think you should do it if that's what you want, it's a cool thing!
Just don't *expect* the same numbers you'd see on stock or lower compression, but be pleasantly surprised if they're still decent lol.
If you're not making more power with more compression it's because you don't have enough octane.
you make more power with higher or lower compression, it can't be both ways just the same... if you make more power with higher compression then it'd make sense to lose power with lower compression...
If everything else stays the same and you lower the CR then YES YOU WILL LOSE POWER. You will have to raise boost/run more timing to make the same power. The only thing lowering the CR does is provide a pump gas friendly safety net.
i thought we were talking 100% e85 in both the low AND high compression situations
no, lowering the compression lets you run more boost and timing for MROE power, not just the same.. why do you think when evo owners swap to a 100% E85 tune, they magically gain 70 odd wheel horsepower over their pump gas tune? magic?.. raising means you have to lower both variables (or at least timing), if you've advanted the timing as far as you can before knock on 100% E85, then raise the compression you WILL have to retard it.
Check this out
shouldn't the supercharger be spinning at the same RPM in the same pulley/intake setup for the same boost?
if so, that would explain a lot of the power difference, more than JUST the lower compressoin?
this makes no sense to me and i've read it twice >_<
"The uninitiated may be tempted to attribute the drop in power on the supercharged applications to the drop in boost pressure,"
well, that's PART of the problem isn't it? :/
i can't fina any info on CR effecting supercharger output anywhere, i'm still trying though.
i get that's the only differing factor, but i was always lead to believe that a supercharger of a certain size with a certain pulley etc. will always (well, in theory) produce the same amount of boost and airflow.. i didn't even really know that backpressure into the intake manifold was a major thing! i just thought exhaust backpressure was the main issue usually