NefMoto

This is probably the noobest of questions, but here goes:
So on the main tuning - S4Wiki, the first thing to do is start with the fueling, until you're "happy with it", I'm just not sure when I should be happy with the fueling. Any pointers? Do I need to get a certain enrichment at certain RPMs?

It's basically the same for most internal combustion engines running on petrol.  Aim for 12.4 AFR at peak torque, getting richer until the redline.  Aim for 11.8/11.6 at the red line.

It all depends on knock, boost and timing though.  I found the other day with barely any timing or boost I still had loads of knock at 12.4 AFR.  Brought it down to 12.2 and all gone.  Brought timing and boost back in, still no knock.  Got it at 11.6 AFR at the line and it seems good.

I'd get a book to read about tuning.  With these ECU's, you can tune with LAMFA or BTS or both.  I've used both, a little LAMFA to enrich with the pedal and then BTS takes over at 400* (so it's basically always active).  I prefer the resolution available with BTS to use that instead. 

As a footnote, always, always, always do fuelling first.  Ignore timing and boost until you have a fuelling curve you're happy with.  Look at others examples, it's a pretty standard table number wise.  Nothing special, just start at 12.4 and get richer. 

Also:
It means making sure the trims are near zero at all times for both narrowband and wideband in closed loop.

For narrowband, it also means getting the actual lambda to match requested lambda in open loop.

Excellent question, btw.

Thanks guys.

So what I understand is, modify LAMFA (read the whole community 1.8 tune, apparently LAMFA is good for beginners), until the curve for AFR (lamsbg_w while logging) is at 12.4 at peak torque (is this load? or is load boost? RPM? Is there a variable to log torque? Anyway, I’m pretty sure I can read up on this, so no worries),

And around 11.6 at the redline (redline starts at about 6500 on my car I think, but the tunes usually increase max rpm to 7k, so I'm assuming from 6500 to 7000).

And make sure there is no knock (I think this means knock voltage is 0, rkrn_w_0, rkrn_w_1, rkrn_w_2, rkrn_w_3)

Once that happens, you have fuelling "dialled in"?

If you have non-stock fueling (MAF, injectors, FPR etc.), no. See my post.

Okay, thank you.

Let's say I did the opposite of what you're proposing, and started with raising the boost a little bit...  ::) If I'm seeing exactly the same knock voltages and slight timing retard at the same RPM's as I did with the stock file, does that mean I'm still good?

EDIT: That is with a completely stock car btw.

Generally, with good gas, yes.

On crappy gas (e.g. US 91oct), i'd wait for a really hot day and see if the car still performs the same.

Sounds good, thanks!

You can also put your shoes on before your pants. Doesn't mean it's a great idea. You might even ruin something.

Now who's being snarky! :P

IMO a "bit" of boost shouldn't really break anything, if he left KR alone...

Allright, I have been warned.  :) I'll look into the fuelling before I do anything else.

Just some food for thought.. Knock induced timing retardation is a reactive process to try and prevent serious engine damage. The ignition timing retardation only occurs after knock has been initiated. Borderline knock over a period of time often cracks piston ring lands from fatigue. It can also hammer rod bearings and cause warped intake valves from overheating.

In regards to AFR calibration:

Being slightly rich is FAR better than being minutely lean in a boosted engine. ~12.4:1 AFRs at WOT are for NA engines, not forced induction engines. While some folks get away with this lean AFR for some time in a boosted engine, it often requires less timing to prevent detonation and at mid to higher RPM ranges retarded timing reduces power. In addition most O2 sensors can not report accurate AFRs except in steady state mode. In other words under acceleration the AFR reading is typically incorrect as the O2 sensor can not accurately respond fast enough compared to the rate of engine acceleration other than possibly in high gear - if at all. This is also a big issue with chassis dyno testing as well as accelerated engine dyno testing.

IME with WOT engine dyno calibration on a variety of engines a true 11.8:1 AFR in a boosted engine in the lower to mid range is the leanest you want to be for best power without detonation. In the upper RPM ranges most engines want to be in the ~11:2:1 AFR range. Some OE turbo engines use 10.9:1 AFR when in WOT from mid range upwards to allow the excess fuel to cool the chamber/valves to prevent detonation. If you have black smoke out the exhaust pipe of your boosted gasoline engine, the calibration is terribly wrong.

I hope this information is useful. I understand that other people's experience may be different.

What kind of fuel are you refering to with those AFRs?

91, 93?

Pump gasoline. The octane is irrelevant as far as AFR.  Many race fuels also uses these AFRs while some racing fuels need slightly different AFRs depending on the chemical composition.

With race gas, you don't need to cool the charge to prevent knock. Target lean best torque (12.2:1 to 12.0:1)

With pump gas, you might need as rich as 10:1 to keep IATs and cyl temps under control, but at the cost of torque (if, hypothetically, you didn't have to pull timing to prevent knock/det).

Also, 10:1 (even 11:1) result in black smoke. It does not indicate your fueling is miscalibrated.

As usual, YMMV. Dyno tuning is the only way to guarantee max power.

My comments assumes that the engine being tuned is using an appropriate octane gasoline for the application. Obviously if a substantially lower octane fuel than required is used then there are all sorts of compromises and running very rich AFRs up to a point will help cool the chamber/valves to mitigate some detonation issues at WOT. Note however that one major auto maker discovered that AFRs richer than 10.6:1 at WOT in their turbo engines induced knock due to the heating of the residual end gases from the excessively rich AFR.

Even with racing fuels the AFR still needs to be well below that of NA engines (~12.5:1 for NA), because of combustion chamber heat build up. After a few seconds at WOT the chamber temp increases rapidly increasing the intake charge temp as the cooing system is unable to remove the excessive heat from the combustion chamber fast enough. The engine can go into thermal run away with leaner AFRs causing detonation even with 100 R+M/2 octane race fuel. That is why IME with WOT engine dyno calibration that ~11.8:1 is the leanest reliable AFR typically used in the low to mid-range RPM range transitioning to ~11.2:1 for upper mid-range to max rpm. These AFR's are for non-oxygenated pump and ~100 R+M/2 octane race fuels - excluding the rocket science 110+ R+M/2 octane type racing fuels.

In boosted engines auto/turbo makers do not tune for SAE Leanest Best Torque (LBT), as is appropriate with an NA engine where it is actually safe and desirable to run at Minimum Ignition for Best Torque (MBT), and LBT. In a boosted application where maximum reliable performance is desired you tune for leanest safe AFR based on the thermal load the engine sees. In short duration (drag racing for instance) you might use LBT on a boosted application but you are asking for serious engine damage when doing so for more than a few seconds at a time.

FWIW, I've never seen black smoke out the exhaust on a properly calibrated engine with a true 11.2:1 AFR at WOT. If you are pulling excessive timing or using excessive fuel to compensate for excessive boost or excessive static compression, etc. then it is very possible that black smoke will result. It would be better to lower the boost/compression ratio as late timing results in burn-down of the intake charge in the exhaust manifolds at higher RPMs causing extreme thermal load to the exhaust valves, ex. manifold, turbos, CATs, etc.

I realize that for years some "tuners" have used excessive fuel and retarded ignition to try and eek out a few more top end HP but it's bad for the engine to do this as mentioned above. The auto makers and turbo companies do not calibrate engines this way as reliable performance is the goal not extremism. Proper dyno tuning will result in maximum reliable power. Extremely low AFRs can create fuel build up in the oil causing premature bearing/cyl./ring wear.

BTW nyet, I have been reading here for some time and I realize that you are a great contributor to the forum and I respect this. Now that I am active on the forum I am sharing my firsthand experience to help the community. There can always be exceptions to the norm or individual situations where there is a need to deviate some from established best practices but the above AFRs have proven reliable in a variety of engines in 400 hour WOT engine dyno durability tests and actual highway operation.

I don't want to see newbies damaging their engines from trying to used excess fuel as a crutch for excessive boost, timing, compression, etc. or engine damage from lean AFRs.

Don't disagree with any of the above, but unfortunately, most of VAG's turbo line up has extremely high CRs, and there is no avoiding the realities of a 91oct tune on the west coast.

This means 11.5-11.6:1 and a lot of pulled timing, even with gaskets to lower compression... leading to black smoke on occasion at peak torque and single digit timing. In any case, I ran my 2.7t with 100% stock internals for 150k of very hard miles, at 2+x stock torque, many track days etc. with 11.6:1 and enough pulled timing for 91oct (even with lowered CR gaskets) and it eventually gave out (bearings/rods, not heads/valves/exhaust etc), so your warning should not go unheeded. Pay to play, no matter what you build.


Understood, and your experience and offer to share information is welcomed.

Don't even feel bad. I never knew what dialing in fuel meant for the longest time.

very educational, thank you