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Old 09-09-2006, 11:57 PM   #66
shvrdavid
Scooby Specialist
 
Member#: 86078
Join Date: Apr 2005
Location: Central Pa.
Vehicle:
2005 Sti
4094R Twin Scroll

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This is an interesting thread...

The one thing that I see lacking in this thread is the theory of why it is there in the first place.... And what we can do with it to gain power...

The reason that it is there, is to control nitrogen oxide emissions...

For years engines had an EGR valve to control nox emmissions, but that has been replaced by phasing the cams...

But what exactly are they controlling with the cam phaser???

To make it real simple, they are controlling the temp of combustion...
You might ask how this is done with just a cam phaser...
It works the same way the old egr valve did, it allows exhaust into the cylinder...
Instead of letting it into the intake, it uses the overlap to leave it in there...

So the real question would be... How can we use this to make more power???

Lets look at how it is mapped...


Look at all of the "20" blocks... They are all heavy load, low rpm...
The same area you need an egr to work or it will ping like crazy under heavy load...

Now look at what Clark pointed out, there isn't anything on the upper part of the map above 5200 rpm... Guess why??? There are zippo IM test that are done at 5k, and why make it make anymore hp stock... It is allready 300......

The point I need to make is that this has more potential than most people realize... The bottom part of the map is allready based out from the factory for IM and controlled combustion temps...

The top end of the map is what we are interested in to make power...

If I had a dyno I know how I would go about tuning for power with this setup... I might not be correct, but I think I would be close...

Now, how to make power with it, and a turbo...

Start with about 11 to 1 afr, and keep it there all the time... for all of the runs... run fixed timing, same boost, etc
Map EGts as close to exhaust valve as possible, there is a reason for being close to the valve...
Using the high load column, find number for each cell that drops egt 200-300 degrees... It will basically be overlap blowthru doing the cooling...
Now smooth the map out and go from there...

Now before anyone flames me about this...

I used to do blower engines sort of this way by changing rocker arm ratios and clearances to find the optimum blow thru to develope a desired cam choice, those new grinds always made more power than the old ones...

With AVCS you can do a lot of playing, without ever opening it up.....

I guess the main point I am making here is that you have to find the optimum blow thru for your setup... Worry about everything else after you figure that out...

After all, engines are air pumps... Make them pump air... If they don't like it, force feed them....
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