Economy Tuning, Afrs, Timing Etc

[zoomzoom]

I am fine tuning the cruising area of my ECU. Recently on a long trip, I had a chance to do a comparison vs the stock ECU on the same journey, and the new tune returns around 12.4l/100km, while the stock was around ~12.5L/100km.

While not totally disappointing, it could improve. At least my tune is about the same as a stock tune in terms of consumption, while being better on full power.

I have been reading up on what AFRs people run on partial throttle. The thing is, light/partial throttle can mean anything up to 110kpa manifold pressure on the stagea (heavy car, AWD, takes throttle to keep it moving).

I have attached my target AFR curves (the actual fuel map is very close), plus the timing map. Are there any areas low down that could do with some tweaking? Is the timing too conservative for the highway, or is it likely to be in the AFRs? For example, what AFR could be safely run at 100kpa engine load? Thanks

PS engine mods include turboback exhaust, high flowed R33 turbo, FMIC

[zebra]

you can run it much leaner than stoitch at cruise.

I ran my old 33 at about 16:1 afr at cruise at 100ks.

takes a bit of time with the laptop and a long freeway.

Its a balancing act between throttle position, map and what the car likes.

then adjust the timing to get the most vacuum while cruising.

just make sure the throttle enrichment settings richen it back up quickly if you need to stab the throttle

[zoomzoom]

you can run it much leaner than stoitch at cruise.

I ran my old 33 at about 16:1 afr at cruise at 100ks.

takes a bit of time with the laptop and a long freeway.

Its a balancing act between throttle position, map and what the car likes.

then adjust the timing to get the most vacuum while cruising.

just make sure the throttle enrichment settings richen it back up quickly if you need to stab the throttle

Thanks, though can you estimate how your 16:1 afr richened as the load increased? Not up to boost, just up to 0 manifold vacuum.

Eg, on my AFR table, I guess you would have around 16 at 50kpa. Im wondering what the safest AFR is for 0 manifold vacuum (around 100kpa).

I would only need to tweak the 1000rpm and 3000 rpm columns for cruising. That should keep it safe for revving the engine out. Plus the ECU uses map prediction for quick throttle changes.

Edited March 18, 2015 by zoomzoom

[GTSBoy]

Zero vacuum is already a reasonable amount of load and so you want to be back below stoich already by the time you are there.

The cruise mixture and timing "optimisations" are really only to lean it out as far as you can and add as much timing as you can in that really narrow window where you actually cruise. So that's like whatever load and revs you cruise at 50 in 4th through to whatever load and revs you cruise at 120 in 5th. That paints a diagonal region on a typical 2D map and you just tweak that area, then roll off back to more "sensible for load" figures as soon as you fall off the sides of that region.

[Kinkstaah]

This is something I liked to play with a lot, but I was never really 'sure' of the settings.

Though my car was quite happy to sit around 15.5-16 and idle there, cruise around there at 100 etc, never really knew if it was right and backed it off a bit. (e85). Infact I could get it to cruise and idle at like 18:1 AFR, but I .. its numbers I was uncomfortable with but the car itself seemed to be happy enough to just rumble along like that. I ended up going for 14.7 or as near as possible when cruise/idle because it just 'felt better' (mentally, the car itself won't cough or splutter until like 20-21:1 AFR!)

My main query is what about things like part throttle, 3-5psi, my AFR would usually be about ~13 or so, which 'felt' fine.

What about things like in OP's post, high AFR at high RPM at 0 boost or vacuum?

Is THAT safe?

I realise you're on decal and most likely decel fuel cut when you hit 7000RPM at 0 psi or -5psi.. but what if you're on say, 1.5% throttle. Is this going to still work?

I realise no one should be driving around at 7000rpm, in gear, at 1.5% throttle, but.. in the interests of tuning..

[GTSBoy]

I suspect it's a lot easier than you imagine. At such massively light loads mixtures really don't matter too much at all, either from the point of view of the amount of heat produced or from the point of view of the amount of fuel consumed. So OEM fuel maps for high revs light loads are reasonable guidance and they always look like pretty close to stoich. You could therefore go stoich or a bit leaner there and not have a problem. Same with the timing. OEM timing maps usually have a lot of advance there. There is so little cylinder pressure that you'd be hard put to cause yourself any problems.

So, going past that one aspect, in general, if there is any noticeable load - ie more than cruising load, then the mixtures need to already be at or below stoich. If there's any boost at all then you really need to be heading down to 13:1 territory. That boost transition region is important to get some fuel into so you don't get hot pinging before you even get into proper boosted load.

So as I said above, the cruise areas where you might go for quite lean mixtures really are an island that needs to have fairly steep slopes back to more reasonable stoich mixtures close to its edges, and as you move away from the edge towards load, you need to get the fuel back into it fairly rapidly.

[zoomzoom]

Well, I have added about 3 degrees of timing across the light load area up to about 80kpa and 3900 rpm, and about 2 degrees around 93kpa. I have changed the 1000 and 3000rpm 50kpa target AFRs to 15.2, while the 100kpa target to 14.0

Hopefully that is a small, safe but measurable improvement

[zebra]

No point guessing timing, It may have had too much advance already.

Really needs to be done whilst driving (using a mate inthe passenger seat) so you can feel/hear/see what the car is doing

[breaker1845]

Road tuning will take a long time to perfect cruise and idle so you get good fuel efficiency or whatever you are chasing. You are going to have to alter some values slightly and test your car on the road then come back and change more values, etc, its a repeated process.

I hope you have some sort of wide band logging that way you can see where you are getting problem AFR's. What GTSBoy has said is extremely important though so make sure you take in his advice or you could be doing quite a bit of harm to your engine without knowing it.

[zoomzoom]

Well I scrapped my timing changes, but kept the new AFRs, Ill see how it goes. Yes I have a wideband.

[Guilt-Toy]

you will find the car will drive nicer on richer mixture, you can lean it out in the cruise / light acceleration areas but you will find that you will need more tps to produce the same power to move the car and end up using the same amount or maybe more fuel then it would normally.

if you want fuel economy, buy a prius.

[simpletool]

As above. Your fuel consumption seems reasonable. Having it too lean on cruise can be counter-productive. Sure it theoretically would use less fuel but then you use more throttle and end up in the next load part of the map, which uses more fuel anyway. (It does help to reduce pumping losses on a high efficiency engine but we're talking 1% and and old RB and ECU ain't going to make that happen).

OK every car is different since it has different parts and have difference sensors with different calibrations but......

From the look of your tune I wouldn't worry about the cruise part too much. I'd be looking at the transition area 80 to 140kpa. You're probably spending a lot of time in that area with a heavy Stagea to get it moving.

Personal preference is that area is too lean. You should aim for 12.5:1, not 13.5. By being too lean the car is not responsive and makes less power and you end up using more throttle and hence more boost than you need. So you drive it no boost, push throttle, 3 or 4 psi and uses heaps of fuel just to move.

Seems to be too rapid to drop timing between 80kpa and 93kpa. I have 31-33 degrees of timing at 100kpa between 2800rpm and 4400rpm. The timing drops faster after 3 or 4psi (120kpa). I still have around 27 degrees at 130kpa. This is compounding the problem from my point above about AFRs. Again you use too much boost just to move the thing along.

But but but, remember I have more fuel in that region as I am already at 12:1 and timing and fuel are linked. Anyway if you are going to change anything make sure you have something to listen for knock and an AFR meter, and you know what you are listening for.

[Kinks]

if you want fuel economy, buy a prius.

There is some excellent advice in this thread, except for this line. I'm self-teaching as well, so thanks all who responded (including Guilt-Toy for your other advice). Since fitting my Adaptronic my fuel consumption has gone up 10-15% with the same driving habits, I put it down to my (lack of) tuning ability but I am keen to close the gap. I don't enjoy visiting the petrol station 60km sooner on every tank.

My ignition map is similar to zoomzoom's, so will try adding a bit more timing at 60-80kpa and keep an ear out for knock. Cheers all!

[breaker1845]

There is some excellent advice in this thread, except for this line. I'm self-teaching as well, so thanks all who responded (including Guilt-Toy for your other advice). Since fitting my Adaptronic my fuel consumption has gone up 10-15% with the same driving habits, I put it down to my (lack of) tuning ability but I am keen to close the gap. I don't enjoy visiting the petrol station 60km sooner on every tank.

My ignition map is similar to zoomzoom's, so will try adding a bit more timing at 60-80kpa and keep an ear out for knock. Cheers all!

The problem there is any amount of knock is dangerous and very small values are extremely hard to hear at all, hence people using knock monitors that regularly road tune. If you add timing, be careful that any changes are reflected in the rest of the map/s so you don't create more issues.

On a side note, road tuning is the best way to get optimal fuel efficiency for cruise speeds and idle unless you spend significant time on the dyno.

If you are good with computers, what you could do is take multiple logs over a period of time/drives and do some mathematics with it through simulations to get some expected averages or something with afrs and you can see where you have high and low points on your map. Timing is much harder to do properly without a dyno (or the right equipment) so having safe values is more ideal.

[zoomzoom]

The adaptronic lists both the target AFR as well as the measured AFR when it makes a log file. The only downside is guessing the delay of the sensor to react to the changing AFR under acceleration.

The knock detection issue is a concern. I tried to log some power runs yesterday with very conservative timing, in order to get a background noise reading on the engine through the RPM range. Even then the knock reading was variable over 3 runs.

Still, I regularly listen to the engine through the ECUs headphone output, Ive never heard any knock. Not a guarantee, but I have no evidence so far that its occurring.

[zoomzoom]

The new highway average over 1000kms is 11.5L/100km. That is with an extra 3 degrees of timing at the low load areas and light load AFRs between about 14.5-15.3. AFRs drop rapidly as you approach atmospheric pressure.

[discopotato03]

I don't think I've ever seen great consumption out of any R series Skyline . I think its a combination of short JDM gearing and the era these engines existed in .

By todays standards they can't run lean mixtures and still perform acceptably .

Correct me if I'm wrong but didn't ADM S14s and 15s get taller gearing than the JDM ones , something like 3.7 vs 4.1 diff ratios ?

I always thought my GTS25T could have used a 3.9 or even 3.7 final drive just to have a bit more speed , or less revs , in the gears . I reckon slightly lower cruise revs and a slightly more open throttle would work better with decent tuning .

Just my 2c cheers A .

[iruvyouskyrine]

Yep ADM 200SX came with 3.7 and 3.9's

[harks]

This thread is actually providing me some useful insights on my current tune. thanks for starting it Zoom Zoom.

Looking at my AFR and IGN tables they definitely need some tweaking.. my AFRs are down to high 12s by 30- 50kpa on the Y Axis. judging by the comments about being closer to stoich at cruise im confident that some changes can be made there. my ignition table looks a bit wierd too, i think it may need some serious work. When i get my laptop sorted ill post up my AFR and IGN tables for reference

[Ben C34]

Tables don't mean much without knowing if your afr's match the commanded value.