Priorities: RPMs vs VAC

[tpwalsh]

Originally Posted by Old Tele man

...how about enlightening us by telling us what "magic" boxes & software you used that enabled you to "get" that data from ECU so that it could be reviewed?

On some stock ECUs you can do that. One that comes to mind is VW. All VWs in the OBDII era can be datalogged. See: Ross-Tech: VAG-COM I'm sure there are other products out there that are similar, ie scangauge already gets the data out of the blackbox, I'm sure that there's another product that will get that data into a computer to analyze.

jjf,
Sorry about the confusion, normally "going lean" is refering to lamba's over 1, or over 14.7:1. One instance of this is the 09+ Subaru STi's. They use a fuel cutout rev limiter. In the autocross world where I come from this is a very bad thing. When the fuel gets cut out, the mixture goes from "safe" in the 12.5:1 range, to lean, nearing 14.7:1, which promotes detonation. Normally this isn't a big deal in roadracing, or on the street, since when you hit the limiter, you shift. In autocrossing we've been known to ride the limiter for up to a second, or a second and a half, since shifting would actually make the car go slower. During this time, you're you high boost and load levels but leaner than the safe range. This has caused detonation which has destroyed multiple multiple engines in under 10,000 miles.

[tasdrouille]

Originally Posted by tpwalsh

On some stock ECUs you can do that. One that comes to mind is VW. All VWs in the OBDII era can be datalogged. See: Ross-Tech: VAG-COM I'm sure there are other products out there that are similar, ie scangauge already gets the data out of the blackbox, I'm sure that there's another product that will get that data into a computer to analyze.

Vag-Com does that, but much more too, I can adjust injection timing and quantity adaptations on the fly with it, or change the EGR duty cycle, idle RPM, etc. It's pretty cool.

[tpwalsh]

Originally Posted by tasdrouille

Vag-Com does that, but much more too, I can adjust injection timing and quantity adaptations on the fly with it, or change the EGR duty cycle, idle RPM, etc. It's pretty cool.

It's very cool, I've been looking for an excuse to buy one(my wife has an '05 1.8T GTI), but it hasn't had any issues to speak of... yet.

[jfitzpat]

Originally Posted by Old Tele man

...how about enlightening us by telling us what "magic" boxes & software you used that enabled you to "get" that data from ECU so that it could be reviewed?

Well, the software is all free, but our data acquisition modules or not, so I don't think it would be right to give a plug. I think that there are some important advantages to some of our stuff, but you can learn a lot from even a slow and simple OBD-II interface.

Some of the make/model specific handholds from Superchip, Diablo, etc., actually do a pretty good job of basic logging. Some even put the vehicles in factory modes and get access to information not normally available via generic OBD-II.

So, I wouldn't want to give the impression that the way I did it is the only way to get it done, or come across like an advertisement.

-jjf

[jfitzpat]

Originally Posted by tpwalsh

Sorry about the confusion, normally "going lean" is refering to lamba's over 1, or over 14.7:1.

Actually, that is the myth, once you go past 14.7, temps plummet.

Originally Posted by tpwalsh

One instance of this is the 09+ Subaru STi's. They use a fuel cutout rev limiter. In the autocross world where I come from this is a very bad thing. When the fuel gets cut out, the mixture goes from "safe" in the 12.5:1 range, to lean, nearing 14.7:1, which promotes detonation. Normally this isn't a big deal in roadracing, or on the street, since when you hit the limiter, you shift. In autocrossing we've been known to ride the limiter for up to a second, or a second and a half, since shifting would actually make the car go slower. During this time, you're you high boost and load levels but leaner than the safe range. This has caused detonation which has destroyed multiple multiple engines in under 10,000 miles.

Look at your instance. The problem isn't that the mixture is leaner than lambda 1.0, but *just rich* of stoich ('nearing 14.7'), where CHTs and pressure soar.

Remember, stoich is the peak thermal reaction. The most heat that can be released from a quantity of fuel. As you go leaner, there is less fuel and the flame front alters, so temps drop. As you go just richer, there is still plenty of fuel, but you get a slower front and longer burn, so pressures soar.

As you continue to enrichen, the flame front continues to slow, but it also changes compositionally. Simply put, we get more exhaust gas pressure, but released more slowly. So, the peak pressures are lower, and more of the released energy goes into work (pushing the piston), then into heating the cyl head.

You see the myth at it's worst in general aviation. Literally, you manage mixture with a red knob and an EGT gauge (or, in some cases, engine roughness!). A lot of times, 'economy cruise' will be peak EGT, but people think that 'lean is bad', so they peak, then just go a bit richer. But this is the worst place to run the engine for CHT's and detonation. Better to go 25 degrees lean of peak (if your engine can do so without running rough) and get great economy, or go 100 degrees richer, and get terrible economy and best power, but either way, CHTs are a lot lower.

You can actually get away with running in the 'hot box' on a normally aspirated aircraft engine, because the air outside is already getting thinner. But, if you want to maximize engine life and reliability, it is not the place to run.

-jjf

P.S. Virtually any MY '96 and newer vehicle can be datalogged for basic ECU params.

[gone-ot]

Originally Posted by jfitzpat

Well, the software is all free, but our data acquisition modules or not, so I don't think it would be right to give a plug.
-jjf

...pardon my ignorance, but who is 'our'?

...I have a SGII installed now, but it neither records nor "passes" through data for concurrent analysis (ie: no, pass-thru port).

...I'm aware of the DAVIS OBDII plug-in; but, to my knowledge, it only records and doesn't "pass-thru" data in realtime for analysis, only post-event analysis.

[jfitzpat]

Originally Posted by Old Tele man

...pardon my ignorance, but who is 'our'?

No ignorance. Just careful choices of words on my part. I say things like "our", because I want to make it clear that I work for a company that makes and sells this stuff for cars. I think that folks should know I'm biased, not just a user.

On the other hand, I am trying to avoid any appearance of being a viral marketting slime. I've lurked here for months while working on some fuel economy related features in a product. Having taken from the community, I figure it is better to give back without a profit motive.

But, if I am going to continue to contribute, this will get tiresome. When I get a chance I'll re-read the forum usage agreement and then post a suitable 'intro'.

-jjf

[ECONORAM]

Intersting article here:
Lean Burn Combustion, 101.

[gone-ot]

Originally Posted by jfitzpat

I think that folks should know I'm biased, not just a user.

-jjf

...I believe a simple footnote disclaimer stating: "I work for XXX YYY ZZZ Company" is commonly sufficient.

...last I heard, employee's (and not just management) were allowed to have external interests and opinions.

[Superturnier]

How much does the amount of charge in the cylinder affect to temperature?

Is the amount of mixture more significant than the A/F ratio of the mixture?

At least the ignition retard is usually controlled by the loading of engine.