[arghx7]

Originally Posted by Shankenstein

The detail at the end about early port injection + late-ish direct injection was really helpful for me. In engineer-speak, it seems that they're creating a stratified charge situation that is sufficiently rich to ignite in open-loop and cold conditions (even with high compression helping) and still gives you the fast warm-up benefits of a lean-burn engine. That's incredibly cool and probably the reason for the knocking we hear during fast-idle warm-up.

It's hard to say. We're going off an advertisement. They are describing a very late port injection timing, which is normally terrible for HC emissions unless you're very careful with AVCS. And we don't know the valve timing under the conditions they are describing. They talk about a late direct injection event, but we don't know what % of the fuel is delivered there. It could be one very quick spray to affect mixture motion--it's kind of hard to have stratified combustion when a bunch of fuel was sprayed into an open intake valve.

Just an FYI, the European Audi engines that are turbo with port + DI use DI only during cold starts. They have two injections per cycle, which is basically a conventional way of doing things. And that engine meets stricter emission standards than an FT86.

On a similar note, I heard about Ford and VW using the variable exhaust valve timing to do a controlled backfire to spool up the turbo.

I think you're just referring to scavenging during spool up by advancing the intake cam and retarding the exhaust. That's normal. STi's can do it, but they are limited because they are port injected. Audi has a different exhaust cam profile they use now during spool up.

Would be interesting if our cold start strategy does this to warm up the catalyst too

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I don't see the cat lightoff strategy on the FA20 surviving the upcoming emission standards. There's too much HC and particulates to overcome. That's one of the reasons why Audi uses DI only.

Word on the street was that many of the OEMs were using inefficient methods to speed up their catalyst light-off times, in an attempt to game the EPA emissions requirements.

If the cat doesn't light off in time, or the engine-out emissions are too high, the engine doesn't get certified and doesn't go to production. So I'm not sure what the original source of that claim is from.

Invest fuel (and reliability) early so that you can get to closed-loop fueling faster than the competitors. They were also trying to "game" the oxygen sensors into getting useful data before they reach their minimum rated operating temperature.

There are a bunch of tricks in the bag. Some involve lean burn and expensive o2 sensors that light off very quickly. Some involve smog pumps (secondary air injection) or HC trap catalysts. Some involve tumble control valves, or expensive DI systems, or valve timing tricks.

Does anyone know how the dual injection timing is controlled? I've seen the variable that controls the quantity split, but I haven't seen much on timing. I take it they are independent (not simultaneous like in the video).

The left map is start of injection for the DI, in decrease BTDC firing. All those values are in the intake stroke (except the oddball ones at 370 degrees).

I haven't seen the PFI injection timing maps. Sometimes there is a fixed end of injection and a varying start of injection. Sometimes the SOI is fixed and the EOI changes. Sometimes it sprays into an open valve, sometimes it doesn't.