dbex

How DO you get more power from an NA engine with chip-tuning? I have a dim sense of how it works on a turbo engine, but when it comes to the NA engines, I am definitely <a href="https://forums.audiworld.com/s4b6/msgs/170852.phtml">in the dark</a>. Anyone care to explaint the basics? Verruckt? Darin? Others?

No agenda here; I'm both a "B5 guy" and "B6 guy," and both my cars are essentially stock (and will probably stay that way). Just curious about what the real issues are.

MachtigAvant (v3.0)

Take advantage and refine fuel maps for larger and better flowing exhausts, I'd assume.

VerrÜckt

It's not easy with an N/A engine. Without external modifications, you have basically a fixed volumetric efficiency which limits how much air you can take in. That leaves you with a few other tricks such as advancing the ignition timing and playing with the variable valve timing. Audi cannot design in an overly aggressive ignition timing map as there will always be someone filling up their S4 in South America with craptane (or Cali for that matter). However, the Motronic system is very advanced and does a fairly efficient job of "adapting" to different fuel grades so really there's only so much you can do in this area. On pump fuel, you won't be able to advance the timing much past stock before you face knock.

You can also increase the rev limit which will only be effective if the engine can breathe at the higher revs. Raising the rev limit on a B5 S4 does basically nothing because K03's are choked as it is but it is of benefit to a B6 IMO. Long term durability does come into question with increased redline as does less safety margin in respect to over-revving.

Other than that, there isn't much to play with. On most N/A engines, 5-15 hp can be eeked out that way. I've never seen a legitimate company claim 40 hp out of an N/A chip.

When we get data, it will be important to compare the MAF values, injector duty cycles, and ignition timing values. If we see no significant differences between the chips, it's fairly safe to say there won't be much power difference either.

Hopefully the dynos will tell the tale too.

MachtigAvant (v3.0)

What vag values are important other than timing and MAF?

dbex

....and that there is therefore a margin within which output can be increased, without nasty side-effects like harm to durability?

I guess I'm not really sure what "detuned" means in this context - does it have to do with fuel maps and ignition timing? Or with things like more restrictive airflow that are outside the engine itself, and require other mods like aftermarket exhaust, like Wes suggests? (If that were the case, I don't know why a chip-only mod would allow such significant gains...)

VerrÜckt

Also, O2 voltage can give you a very rough indication on how rich/lean the car is under WOT, but a wideband would be much better. I'm not sure if VAG-com is capable of telling you anything about the valve timing as I've never tried it, but this could be useful. Throttle position is good (because with DBW, putting your foot to the floor doesn't guarantee WOT) and maybe even load. I would put the heaviest emphasis on MAF, timing, and knock sensor activity.

MachtigAvant (v3.0)

suit. Then we can compare with other owners.

I'll keep you posted. Some interesting findings should be made very soon.

Charlie_Iliff

Unfortunately, knock sensors have to have a pretty definite rattle, and overhead cams mask some. Even with a good lamda meter, we have trashed 12/1 or 13/1 CR engines on a dyno with "Unleaded Race" gas allegedly in the high 90s octane. When you run the spark advanced and mixture a little lean, to get peak power, detonation came come on pretty suddenly and do damage while the sensors are still getting sorted. I don't want to take any street engine anywhere near that line. A modern street mixture map is so complex that race motors are a lot easier to deal with. Audi has to write not only for power and safety, but for emissions, which usually means lean mixture. You can assume you'll get a bit more power at some points on the curve just by richening, but not a lot. a point either side of stoichiometric won't get 10% horsepower at peak, but that much move can melt things if you're already lean. "Detuned" engines keep running.

Captain Sheetmetal

As several people have said, with a given pumping efficiency (an engine is just a complex air pump), there is not a whole lot to do. Turbo cars are easier to deal with because you can simply increase the boost (more air in allows more fuel to be burned=more power).

With an NA engine you cannot force more air into the engine so the best you can hope for is to make the air's journey into and out of the engine as easy as possible (free-flowing intakes and exhaust). That way, the "bottleneck" so to speak is the engine's own efficiency at ingesting and evacuating air.

So what can you do to make an NA engine "process" more air? Increase revs. Unfortunately, our engine is a "stroker" engine (stroke is longer than the bore is wide) and wasn't really born to rev. Five valves help, but aside from changing the cam <b>profile</b> (not just its timing), there isn't a great way to allow our engine to make use of increased revs. If the valves cannot allow enough air past them to supply the engine at higher rpms, the only result of high rpms is more noise. Honda's engines make such high power from low displacement because they switch between two sets of cam lobes. One makes the engine drivable at low rpms and the other is a "breather" cam profile that allows huge amounts of air past the valves for high-rpm efficiency. So I would say the next frontier for our engine is a new set of cams+maybe an increase in revs. I think some people are working on it.

You can muck around with the ignition timing as many here have said, but you won't be able to increase it much without some serious detonation. My car detonates already (before the knock sensors reign it in) on 91 octane.

Scourge

Most n/a chip tuners also make them run leaner. Lean is mean you know There's quite a bit of power to be had in that too.