wthdidusay82

iTrader: (15)

So I have set up my microtech base timing with timing locked to factory mark set at 5atdc , which the computer will read as 0 timing if static is set to 0 (but it's actually negative).

So I've been looking around for answers about setting your maximum advance in a turbocharged car with 8.5:1 compression (stock ports), and I've found little to no information.

How much timing advance is safe to run in vacuum, and how much is safe during boost (car will be running 15 psi max/ 1 bar).

I've currently got my static timing set to 0 (which skews timing values off by 5 degrees since timing is actually at 5atdc (since only way to make them true is having a 0 tdc mark or any mark at btdc).

So I've taken the setting for maximum timing advance and brought it to 33 (which makes it a true 28 degrees) , I've asked around and looked around and found 30 degrees is about the max advance you should ever have but im not so sure.

Anyways, I set my timing advance to go as high as 28 degrees during vacuum (actually shows 33 on microtech because its 5 degrees off), and I'm really not sure what to set it to come down to during boost. I am thinking my timing might be a bit on the aggressive side at 28 degrees, or am I right on the money ?

I was going to lower it to around 22-25 true advanced timing as per what I've read in a post that bumpstart commented in about what you should run under vacuum in a turbo 8.5:1 engine, now I've still yet to run boost, but from what I've seen the timing under boost tapers down to around 15 degrees at full boost, progressing downwards from around 2 psi scaling up to 15 ish.

Edit - The maps are based on using MAP sensor only for load, Tps is only used for idle.

Aaron Cake

iTrader: (1)

Here's the problem...the Microtech limits you greatly on achieving the ideal timing curve because of its stupid "virtual distributor" paradigm of setting a base timing curve and applying corrections. Instead of every other EMS that has a 3D table.

For example, here is what I consider a good timing table for many applications, this one from one of my Megasquirt (MS3) tunes:

http://www.aaroncake.net/rx-7/megasq...on_table_1.gif

(not sure why image is not showing)

Idle timing on that table is fairly aggressive. Ideally idle timing would be around 10 degrees then have "hills" of about 15 degrees surrounding the idle bin. This helps stabilize idle.

Anyway, this table gives you and idea of how I normally set cars up.

Note how rapidly I drop timing once in boost. The factory ECU runs over 20 degrees of timing in boost! No thanks.

One can actually run more timing in the cruise areas of the map...into the low to mind 30s, but that also greatly depends on AFRs. At stoich 35 degrees would be acceptable. But we often burn leaner than stoich and timing like that could end up creating turbo melting EGTs.

In the high vacuum decal areas, note that it jumps to near 40 degrees. That helps prevent bucking, and cleans up the exhaust.

But again, the Microtech model limits how much of this you can achieve.

General rule is drop about 2 degrees per PSI of boost. By 15 PSI, you should be around 10 degrees on 8.5 rotors. Higher compression requires less timing.

wthdidusay82

iTrader: (15)

Micro tech does timing weird. It has a map for rpm then a map for load.

So if you are at say +25 at 3500 rpm map, you'd use the vacuum\boost map to subtract timing based on boost right ? So you'd subtract -15 to the value to make it 10 at 10 psi.

10 degrees does seem concervative, I've seen more around 15 in my research around 15 psi

Also the idle when timing is advance runs poorly , it seems to like 5atdc , otherwise it is very jumpy. Car is stock port.

Aaron Cake

iTrader: (1)

Yes, you'd set your main timing map to look much live the curve on a distributor. So looking at the default it starts around idle with low timing then ramps up to 25 degrees by 2000 or 3000 RPM, flatlining to redline.

Then you use the t_map (think that's what it's called) to add a bunch of timing in vacuum, then subtract about 15 degrees in boost by the time you're at 10 PSI or so.

OneEyeMick

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