Going back to the OPs question.... Is where we needed to be at.
So you are saying that the OP would not make more power on lower CR?
There is a reason your last 9:1 tune is seeing so little advance at 30psi this needs looking into.
What's there to look into? It is completely normal that this is going on.
Boost any 5 valve head to this amount and you will see exactly the same thing. Take a stock 2.7TT, boost it to 30 psi, you will see the same timing advance.
Take a RS4, boost it to 30 psi, it's almost as bad.
I personally know I can run 400-450bhp with same CR on 98ron fuel and make 20deg+ advance in the power band. I would have a bet the Ibiza dude above would have seen the same results?? As I know one of his customers running 400bhp+ 9.5:1 with oem Ibiza pistons 20deg+ with zero knock.
You completely ignored that I pointed out your numbers did not match up. Or am I a super mega tuner and can make the same power as you at 3 deg advance, as you at 21 deg advance? Fact of the matter, you were not running 30 psi @ 6800 rpm, or your setup had other issues.
I see lots of statements but no logs. I can make 450 hp on 10:1, I will just have to rev the crap out of the engine. What is your point?
My point is, that these engines are forced induction, not N/A.
Surely the principles of a Forced indution engine are the same? 1.8T runs a 9.5 or a 9.0 on a BAM and the Edition 30 BYD lump runs a 9.8:1 compression ratio? So surely the air entering the cylinder through the inlet is the same as that of the lower compression engine? So why have VW opted for a higher CR engine on a FI engine?
Matchew - I think he meant in a 1.8T application
Surely If I can run more boost on a lower CR application, does this not cause excess heat produced by the turbo and higher exhaust gas temperatures? Something which should be as controlled as possible??? as im sure we all know what happens when EGT gets too high..
You got it completely wrong. You don't need to run more boost to make more power at a lower compression ratio.
For the final time, you are not running a perfect fuel. Your fuel has an octane rating. Get that through your head and everything will make sense.
1. No one ever stated high CR does not work, it was stated that lowering CR will allow you to extract more power.
You said my setup had serious issues in your first post on this thread due to running a High CR on GTX3071r?
Yes, because I like cars to make power.
You will see gains across the power band by dropping CR, that is why I said it is not optimal. Plain and simple.
2. You will not notice any difference driving the car until about 8.0:1, because down low throttle response is governed by pedal mapping more than anything on DBW cars, the difference in CR is not really noticeable.
I think I will be going for linear throttle mapping on this one, to retain how a cable driven throttle body would function....Not into this you get 80% power at 50% throttle position crap from stock VW mapping
That doesn't matter. You will not notice any difference between 8.0:1 and 9.0:1 on part throttle.
Also, the throttle on cable cars is not "linear". Low down the range, you have effectively full power output at 50% and lower of the throttle, simply because the engine can not breathe anymore and the throttle is not the restriction.
The reason the OEM maps the car the way it does, is to give the engine a linear feel between off-boost and on-boost behavior. So that you do not instinctively floor it, then lift the throttle when the car starts coming on boost, as you do with a DBW throttle. The idea is to map a certain produced torque to a pedal position in all RPM ranges, that is why it is calibrated the way it is.
Dissing the stock calibration without understanding it seems a really popular thing.
3. With higher CR rpm vs boost will look better, but time vs boost and time vs RPM will look worse.
Back to my above point of more boost equals more heat?? killer of engines?
If you actually understood anything of what I am saying, you would understand that this was describing spool characteristics.
Breaking it down for you. If you plot the car WOT from 2000 to 4000 rpm, then a lower CR engine will get from 2000 RPM to 4000 RPM quicker than the higher CR engine, unless the CR is so low that it is not restricting timing anymore. Now re-read what I wrote with this in mind, and you will understand.
4. The factory runs high CR due to emissions and even the factory drops the CR on the K04 engines, although this is travesty from their standpoint of emissions.
If anything, thats quite the opposite that happened.....Early 1.8T engines (AGU for example @ CR of 9.5:1 )with no emissions stuff such as VVT or SAI ran a HIGHER compression than those of the later variety using SAI and VVT for emission purposes where CR was dropped to 9.0?
Incorrect. Go and educate yourself a little bit on the compression ratios of different 1.8T engines.
