Lean burn engine (E85?)

[serialk11r]

Okay yea in that case you should lose fuel economy if you change the maps, because having more overlap should increase your fuel economy assuming you don't have a misfire problem.

Unfortunately, as I'm finding out with my own car, tuning valve overlap is very tricky because you really don't know how much exhaust gas is flowing backwards into the intake and thus you don't know how the optimal ignition timing is affected.

[Juho]

Hmm, this just got weird.
I got frustated of sudden power loss on more than half throttle, and started testing again basically from zero keeping it from hitting lambda correction limit:
Full throttle air mass flow showed 60-100mg/stroke more than previously.

After quick ignition timing optimizing, momentary fuel consumption was around 8l/100km at 100km/h ; stable.
Plus no random power loss.

Then reduced the IPW two times; on the last time it hit the maximum lambda correction and lost power. At full throttle shows again a lot less mg/stroke, and it's noticeable.
Cruising at 100km/h mg/stroke is also ~20mg/s higher = worse fuel economy, around 9-10l/100km and not stable.

So I have actually wasted a lot of time, just because of some odd safety mode.
Time for Speeduino.. maybe I'll see some actual gains and vanos/ignition map tuning actually makes some sense! And lean burn of course.

[serialk11r]

Good luck with speeduino, does it let you use wideband O2 output to get whatever closed loop lambda you want? That would make your tuning much easier, just back off a little exhaust cam retard from stock, and then just jack up the lambda and timing until it is unhappy.

[Juho]

Yes it does allow wideband O2 sensor use, and if I remember correctly; any lambda value that the wideband can read, can be used on closed loop.

[Juho]

I took the engine out of the BMW about 3,5 weeks ago, and disassembled it completely to check if there's anything wrong.. and had to weld the body (rust) and do some painting so was a good moment for doing something for it; and currently have a Volvo V40 1.9d manual because the BMW had too many problems to be fixed and fuel consumption got very high for some reason.

Every oil seal and gasket were leaking, and a few valves (intake and exhaust) had hit the piston, but the valves were straight or straight enough not to cause problems. Probably valve spring's seat/open pressure reduced or worn timing chain / guides / tensioner has caused the valve timing to go too advanced or retarted plus a bit too much valve guide clearance.

Only marks on the pistons, but not on the valves so they've "just touched".
I was very surprised noticing the exhaust valves or seats hadn't burnt; actually in very good condition compared to other similar engines I've disassembled (and heads)!
Pistons were also good, no marks of melting or detonation or anything.. quite clean because of E85.
This is a good sign, because I had ran the engine around lambda=1.20..1.25 mixture and even at lambda=1.40 when trying the lean burn limits and highest advance was 52 degrees BTDC (which only reduced power -> worse fuel economy).

Anyways, I've got now 2.8 liter crankshaft and pistons (which need modifying) so I'm able to reach a lot higher compression ratio.
Sadly I've had a lot of problems with my mira valve seat cutting machine (very old), and haven't been able to finish my cylinder head.. and without those very frustating probelms I would already be driving the BMW.

Maybe some day..

I did start thinking about gearing (for next year), and its benefits.
I have noticed many newer 2 liter diesels fitted with 6 to 9 speed automatic transmission run around 1500-1800rpm @ 62mph.

As an example, one version of BMW N47D20 engine produces about 200nm@1500nm.
The petrol engine; M52B25TU has ~180nm@1500rpm if the engine is in good condition and there are no faults active.

2.8 liter, high compression and E85 should have no problem producing ~220nm at 1500rpm.
A 3 liter straight six engine with 14:1 compression ratio, itb, small cams (stock) and E85 produced 220-230nm@1500rpm with a lot later intake cam timing ; allowing it to breathe at higher rpm's .. peak hp at 7000rpm, but reducing peak torque and power below 3000...4000rpm.

So in my opinion aiming to around 1900rpm@60mph (from ~2700rpm) should have a very dramatic effect on fuel economy on the BMW.. which is possible with 6spd gearbox and 2.93 vs. 3.23 final drive.
And still be fun to drive.

Here's an interesting article about lean burn and port injection strategies:
https://www.speed-talk.com/forum/vie...hp?f=1&t=63866
(there's another link on the site, that opens the pdf)

If I could cause the engine ignite with just compression->heat aided with spark plug for longer time, it should be possible to run with very lean mixtures; like lambda=1.40 or leaner and improving fuel economy.
I'm quite confident on saying the very high compression ratio helps with the pre-ignition mentioned earlier on this thread, caused by too much ignition advance and maybe enough heat in combustion chamber?
Or something else that caused sudden acceleration, reducing also a lot of the momentary fuel consumption because it was possible to reduce throttle and still keep up the speed.

And because there were no signs on the engine of detonation or anything that could have had potential causing an engine failure, I don't see any problem trying to causing auto-ignition while cruising.
Only potential problem is, how to control it.
On gasoline it would be very hard and high risk of detonation or melting pistons or burning valves, but E85 might have the possibility on being "sort of controllable."

[cRiPpLe_rOoStEr]

Last time I saw a souped-up engine running on ethanol at a 14:1 compression which it was not meant to feature, that was a naturally-aspirated carburettor-fed Volkswagen EA827.

Originally Posted by Juho

currently have a Volvo V40 1.9d manual

Is that engine Renault-based or outsourced from Volkswagen?

I did start thinking about gearing (for next year), and its benefits.

Once in a while I think about it too, reminding some old-school engines with a much narrower RPM band and lower compression ratio than modern econobox engines.

[Juho]

It's Renault based, using the Renault F8Q(?) 1.9 turbo diesel engine.
Good fuel economy, even though has some problems increasing fuel consumption.

Probably one reason for shorter gearing is to make the car easy to drive.

Even late 90's Honda Civic with D14A3(?) engine has less than 2500rpm@60mph with 5spd manual gearbox, and it's very economical car but slows down to uphills if not going with 4th gear.

PSA EW10 series engines have also stupid short gearing. About 3000rpm@60mph.
2 liter petrol engine, a lot of torque for it's size = no sense having that much rpm at that speed.

[cRiPpLe_rOoStEr]

Originally Posted by Juho

PSA EW10 series engines have also stupid short gearing.

At least until some 15 years ago, it was still usual for PSA stuff to have even shorter differential ratios in my country.

[Juho]

Citroen C5 2005 with EW10A and 5spd manual gearbox, on winter (from -15 to -25C, or 5 to 13F) had about 31mpg fuel consumption avg. on 25 mile trip.

It had ~3000rpm @ 60..62mph if I remember correctly.

On summer without ac should have been possible 33.6mpg or better fuel consumption.

But it is almost same as the BMW E39 fitted with M52TU or M54 engine.
Only being more economical when driving on city / slower than 50mph, because of the gearing.
Even tho the C5 has lower drag coefficient and frontal area (?) and is a lot lighter.

I did like the engine. Easy to drive and had plenty of power.
Had about 138-140hp/200nm even tho the engine was quite worn since I rebuilt it with original pistons (bought it with very bad oil consumption problem), where a stock 325 E36 can have 150-160hp/200nm depending of the engine's condition.
Not sure how much my light porting to cyl.head and 3-angle seats had effect, probably nothing noticeable.

[cRiPpLe_rOoStEr]

Have you ever tried ethanol on the C5?