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Old 10-31-2009, 02:28 PM   #119
JSarv
Scooby Specialist
 
Member#: 163445
Join Date: Nov 2007
Chapter/Region: MWSOC
Location: Effingham IL (Central IL)
Vehicle:
l33t *******
12.07@115.9mph-EJ205

Default

You need to have a fain idea of your peak torque. You need to have a faint idea of your engines VE - Knowing the efficiency range of your turbo/air it moves/and efficiency of your engine can almost spit numbers out with enough equations.

In boost, depending on your turbo, peak torque should be between 3500-4500 rpms on an EJ205. Look at old logs, instead of looking at the maf - look at the engine load vs rpm vs map. You'll notice as rpms rise so does the map and so does engine load. It may peak or it may hold for a bit but it slowly tapers towards redline (or quickly depending on your turbo). So knowing this and using that spreadsheet I made, in boost you know that your peak torque comes at X rpms, so that will obviously have the highest number in the column. As the rpms go on, unless you have big cams or a big turbo, that number should slowly diminish towards redline. This is saying that as you near redline your VE is dropping.

Out of boost, below 14.7 psiA, your peak value should start very low at a low manifold pressure as you near 14.7psiA it will slowly climb towards your peak torque. So your peak numbers should make a somewhat steady line from 2800ish (VERY low MAP) to your peak torque (mine being 4400 rpms)

At low manifold pressures there is a ton of pumping loss, an engines ve is terrible and throttle position must be taken into account.

It should look like a mountian peak/flat top from 2800ish to 4400ish as the map rises. It could be lower or it could be higher depending on your modifications... << VERY important.

Your timing map should be inversly proportional to your SD map. Meaning where you are very efficient, your timing will be low. Where you are not efficient (a - number or the lowest value) your timing will be high.

Not to be a dick but inversly proportional means 1 = -1, 2= -2, 3 = -3, ect.

As your engines efficiency rises, typically (NOT always) cylinder pressures rise. When cylinder pressures rise, flame front speed increases (takes less time from spark to flame front reaching the cylinder wall, or peak cylinder pressure from combustion). You would obviously drop timing to keep your peak cylinder pressure in check. At low loads, since the engine is so inneficient more timing is needed as flame speed slows.

^^ is the best I can do for you. I'm sure (no pun) Ken can tidy that up a bit but that is my take on it.

Again there really is nothing wrong with maf based, its actually more efficient in determining air density. However, keeping a laminar flow over the sensor and having the amount of resolution SOMETIMES needed to keep fueling in check from fire to fire is not an option for us.

I'm not going to say that SD would benefit anyone with a stock turbo/inlet/intake in any way shape or form. However, someone (like me) who has a 3" turbo inlet, 3" compressor inlet, and needs nearly 80mm of maf housing size to keep from maxing out a sensor, it will greatly benefit.

I'm going to be testing it out again on a guys 2002 WRX with basic stage 2 bolt ons. If I cannot make it any smoother in any way its going back to maf and staying for CEL purposes.

I'm willing to bet the maf tune stays...

-jerod
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