Disable high Rev cold start

[troek]

my neighbors might be happier about me getting OFT more than me, lol.

[Td-d]

Originally Posted by mad_sb

I will look at my logs in a bit for overlap and throttle angle but, a big component is the afterstart timing. The default after start timing is -15, when the high cold start idle drops the timing does back to the normal +13 - +15 degrees... this is easy enough to edit and does change the noise level but it also creates stability issues for the idle system and can throw numerous codes.

I'l still messing with it. at one time i had set the after start timing to 0 and it would throw an ignition timing out of range code or somethings like that but it was a lot quieter.. The idle rpm also went up. at the time i was not messing with the idle speed tables.

I found these for the STI's, just a word of warning from one of the experienced techies:

Originally Posted by andya

A word of caution for those who would automatically zero these values:
I believe this table serves more than just catalyst warmup as observed with our project 07 STi with Mahle (low silicone) drop in pistons. After start, the engine is quiet below +5 degrees then the pistons begin the Hawaian fire dance beat which intensifies to +16 degrees until the engine reaches operating temps. Too much timing during warmup will cause scuffing, but E fuels may react differently.

[arghx7]

High RPM & retarded spark provide heat to warm up the cat. -15 degrees (BTDC firing, so 15 ATDC firing) is about average spark retard on a modern direct injected engine during cold start. I'd have to take a look at the injection timing. If it's running just DI, you'll usually have two injection events, roughly 50/50 or 60/40 split between the first and second event. The first is in the intake stroke, around 240-260 BTDC firing. The second is on the compression stroke, roughly 40-70 BTDC firing. This stabilizes the combustion enough to allow retarded spark. If the engine is cold enough you'll just see a high rpm idle, single injection event, and maybe less retarded spark. It's focused more on warm up and less on emissions, because there are no emissions tests taking place colder than 20F/-7C ambient.

I haven't seen charts on the cam grind vs crank angle, but the valve overlap burns up the HC emissions if intake valve ends up opening BTDC intake. It's commonly used on Japanese cars.

What happens is, the HC emissions are ejected mostly when the exhaust valve opens and when it closes. If the intake valve is open at the end of the exhaust event with piston still ascending, that HC goes back into the intake port where it can be burned up on the next cycle.



One last thing to keep in mind. The stock tune was designed to start and idle ok on really crappy fuel (does not vaporize well) in very cold climates. That's one of the reasons why it behaves the way it does. There are special lab-grade "heavy startability fuels" that's used to test this. So there is a certain safety margin you are seeing in the stock tune. One of the side effects to that can be NVH concerns.

[7thgear]

unless you take prestine care of your car (high grade fuel, warm~steady climate, frequent oil changes and meticulous observation of the various readouts... i wouldn't fuck with the car's warmup algorithem.

[mad_sb]

OK, looked at some logs. Cam timing does not change after it kicks down from high retarded timing idle. Direct injection timing does though. During the retarded timing high idle, the DI fire angle is 45* as soon as it bumps down to regular ignition timing fast idle the injection timing goes to 320*.

So, during the high retarded idle the injection is also retarded to help put more energy into heating the cats. So far i have not seen a table that has an injection timing adjustment for this phase of the cold start.

[DylanFRS]

Some of the posts in this thread seem to be talking about the valve overlap changing for cold startup idle. I was under the impression that the FA20 doesn't have the ability to to change valve timing... Am I missing something?

[350matt]

its dual VVT so you can change inlet and exhaust timing and overlap between

whether you can access the cold start functionality to cure this high startup revs is another matter

[arghx7]

Originally Posted by DylanFRS

Some of the posts in this thread seem to be talking about the valve overlap changing for cold startup idle. I was under the impression that the FA20 doesn't have the ability to to change valve timing... Am I missing something?

Yes.

It has AVCS on intake and exhaust cams. Basically, a hydraulic cam phaser moves the cam centerlines. Intake cam can be advanced from the most retarded position, and exhaust cam can be retarded from the most advanced position. This allows overlap if the cams are phased far enough.

Now, it depends on the grind of the cam. If the intake valve opens at 20 degrees ATDC intake, and exhaust closes at 10 degrees BTDC intake, you need over 30 degrees of intake cam advance to create overlap and backflow into the port.

[arghx7]

Originally Posted by mad_sb

OK, looked at some logs. Cam timing does not change after it kicks down from high retarded timing idle. Direct injection timing does though. During the retarded timing high idle, the DI fire angle is 45* as soon as it bumps down to regular ignition timing fast idle the injection timing goes to 320*.

Is PFI running in your log?

[DylanFRS]

Originally Posted by arghx7

Yes.

It has AVCS on intake and exhaust cams. Basically, a hydraulic cam phaser moves the cam centerlines. Intake cam can be advanced from the most retarded position, and exhaust cam can be retarded from the most advanced position. This allows overlap if the cams are phased far enough.

Now, it depends on the grind of the cam. If the intake valve opens at 20 degrees ATDC intake, and exhaust closes at 10 degrees BTDC intake, you need over 30 degrees of intake cam advance to create overlap and backflow into the port.

So is the valve overlap messed with for higher RPMs? Because that would means these engines have variable valve timing and I would be surprised that it isn't making more power in the top end. Granted it wouldn't change profiles as vtec engines do.

[wparsons]

Originally Posted by DylanFRS

Some of the posts in this thread seem to be talking about the valve overlap changing for cold startup idle. I was under the impression that the FA20 doesn't have the ability to to change valve timing... Am I missing something?

Valve timing it can do, valve lift it can't.

[DylanFRS]

Originally Posted by wparsons

Valve timing it can do, valve lift it can't.

Makes sense, thanks!

[Td-d]

Originally Posted by wparsons

Valve timing it can do, valve lift it can't.

Interestingly, there was a generation of Subaru engines that did have both AVLS and AVCS (i.e. timing and lift) - the older H6's.

[Raven604]

IF its so important to keep the idle to high on a cold start why can you start the car cold, immediately drive the car a foot or two and have it drop down to normal idle. Why wouldnt it continue to have a high idle until its "warm"