DJ fuel consumption and ignition timing.

[KINGPRAWN]

valve arrived today....all is fine and dandy......running 98ron at 10 deg btdc and idle sweet at 850rpm. wether or not the 98 fuel has made the big diffrrence or just having it all set right i'll not really know but in all the years i've had it its NEVER gone so well and on so little fuel. thanks guys for all your input

[mm289]

Nice when a plan comes together eh?


MM

[hotpod]

KINGPRAWN, when you say "so little fuel" am i correct in thinking that's a relative thing?

[KINGPRAWN]

KINGPRAWN, when you say "so little fuel" am i correct in thinking that's a relative thing?

well yeh.....guess thats a given.tragic relative to terrible!!!!!

[PetenAli]

I guess once its all set up then a fill up with Shell every four or five tanks full would do the trick. In between you can then use Sainsburys high octane which is not quite such high octane and doesn't have all the additives but is about 10p per litre cheaper. I'd be interested to know what Syncrosimon thinks on this as he started this whole thread and again I've learnt a load from it.

Pete

[toomanytoys]

If the octane is high enough then thats what matters.. these engines were designed to run unleaded in any case so no "memory effect"...

yes maybe the "premium" brands have other addatives in there that may assist in some smaller way, but remember our engines are very old technology.. they prob wont benefit much from the "fine tuning" in Shell V power etc... your turbo nutter jap import impreza would though...

I always found my old Audi 100 went so much better on the tesco's 99 stuff than all the others..

Soon be able to experiment with the fresh engine going in the syncro.. may even get it on a dyno to see what really happens... worth doing that before and after my new zorst...

[silverbullet]

I recall an episode of Tw@t Gear when they went out to buy some "cheap" classic italian supercars. Lambo Urraco was one of them, Maserati Ghibli and a Dino. They put them on the rollers and the reaction to all of them was:
Is that all it's putting out?
You'll only be upset when you find out it's making the same as an 1147

[Mudlark]

I dont know if its all in the mind or what but i and others have also felt the vans run even better on fuel from France, Belgium etc. Seems to be a suggestion that their general fuel quality is better than ours !

[toomanytoys]

Dyno.. I wont be dissapointed.. surprised... LOL.. but I meant with the fresh engine... would be good to chuck this on and see tho.

Pretty sure the french ptrol has 10% ethanol in it.. something about it is different, it smells different (neat and from exhaust)..

Diesel, didnt see any difference when we went a few weeks back in the beemer.. apart from a bit more black smoke booting away from the toll booths..

[tencentlife]

When the ignition was set to 5 degs I noticed that the DJ would run rich at a cruise, up to lambda 1.10, ( I have an exhaust lambda gauge fitted) since reverting back to 10 degs she now cruises at lambda 1 and I am getting the economy.

Not here to nitpick, but thought I might point out the lambda 1.1 is lean at 16.17 AFR.

The lambda number is a multiple of the air component at stoichiometry (aka "lambda") for your particular fuel. Fuels vary as to how much air by mass they should be mixed at for complete, or stoichiometric, combustion, wherein all the hydrocarbons and all the available oxygen are consumed in the combustion process. Gasoline has a stoich AFR of about 14.7:1, but straight ethanol is stoichiometric at about 9.8:1 air-to-fuel by mass.

So if you read the WBO2 meter as lambda (you can set most of them to read in AFR instead), the air component of the air:fuel ratio is, for gasoline, 14.7 multiplied by the lambda number, so in this case the air component is 14.7 x 1.1 = 16.17. Numbers higher than 1 have more air than a stoichiometric mixture so they are lean, numbers lower than 1 have less air so they are rich. The fuel component in the ratio is always the second number and is always 1.

So going in the other direction, a rich high-load gasoline mixture such as 12.5:1 is a lambda 0.85 (12.5/14.7 = 0.85).

I suppose your entry must have been a typo, Simon, just thought I should set the facts straight since some people were wanting to learn about lambda. Wouldn't want them getting off on the wrong foot.

[mm289]

I love it that 10c, one of the engine building legends in the US, pops into this forum at midnight our time to check we've got it right

10c, your a star mate

MM

[toomanytoys]

Bloody nice chap that Chris...

[tencentlife]

Cheers fellas.

I hope what I wrote makes sense.

And actually, a lambda 1.1 is a nice cruising mixture anyway, oughta pick up one or two mpg with that.

[PetenAli]

Cheers fellas.

I hope what I wrote makes sense.

And actually, a lambda 1.1 is a nice cruising mixture anyway, oughta pick up one or two mpg with that.

Thanks very much. As the one who asked the original question on this thread about lambda you'll understand that my knowledge is limited. So I had to read your first post several times but now it is starting to make sense. Presumably then if you have an exhaust lambda guage and sender as Syncrosimon does then you can set up your own AFR

[tencentlife]

If you have a wideband oxygen sensor and controller (WBO2), feeding either a gauge or PC, you can read your air:fuel ratio in real time.

Setting up your own AFR is another matter. Whether you can do it, and then how to do it, varies from engine to engine, depending on what engine management controls that engine uses.

On carbureted engines it involves making adjustments and/or changing fuel jets in the carb.

On a fuel injected engine it can be rather difficult, especially for the inexperienced, to make changes that would get you the desired AFR's under load and at cruise. On wbx's with Digijet or Digifant systems, the air flow meter (AFM) can be manipulated, involving a lot of trial and error, to get to the desired mixtures, but I have to say having played with these a lot, it's not for the faint of heart.

But at least having a WBO2 system lets you see accurately the results of changes you make. But just because you can measure the results does not mean you can go directly to where you want to be, making changes requires having a thorough understanding of how the AFM influences mixtures. And on Digifant, the AFM also has a direct influence on ignition timing, so with that system you can find yourself at cross-purposes playing with the AFM signal.

And of course, if you are returning the O2 sensor signal to the ECU in a closed-loop configuration (many WBO2 systems can emulate a narrowband O2 signal and feed it into the ECU as if it was using the stock narrowband O2 sensor), the ECU's lambda control program will make the system seek 14.7:1 AFR at idle and mid-throttle positions no matter what changes you make to the basic signals that the ECU uses to determine mixture (that is, once the coolant temp rises above the threshhold where it enters closed-loop operation; before that point, adjustments you make may make the engine start and run very poorly, or not at all). An unmolested (factory settings) AFM will also give a high-load mixture in the low 12's as well, the problem with the stock setup is it takes too long to get to that richer high-load mixture when you go to wide-open throttle.

There are ways to force the system to run at your specified mixtures under closed-loop operation using some WBO2 systems that have more than one programmable analog output channel, but once again doing so requires an intimate understanding of how the system you are overriding works in the first place. It's alot of fun, but the learning curve is pretty steep.