Timing For E5 And E10 Petrol DJ2.1 Engine Query

[Stesaw]

Re-reading that "how to"

the only clearly visible mark on the pulley is a 5 degree BTDC mark.

Well.. if thats the case I'm at 5 degrees..IF there is no difference between Digijet and Digifant pulleys.... I think I'll do the 3k 35 and see how that goes!

[Robsey]

Looking at Bentley and the VW factory manuals, there IS a difference between Digijet and Digifant.

According to the VW fuel injection manual...and Bentley

VW FI Manual -for ron values.


Bentley for Digijet. Basic timing.


Bentley for Digifant. Basic timing.


Digijet is said to be suitable for minimum 98 ron (VW) and set at 5° +/- 1° after TDC. (Bentley)


Digifant is said to be suitable for minimum 91 ron (VW) and is set (basic setting) for 5° Before TDC +/- 1°. (Bentley).

So 10° difference on base setting. (5 btdc and 5 atdc)

I am sure that one of the gurus will be along soon to confirm, correct, or deny everything

I vividly recall backing-off (retarding) the timing on my mk2 Cavalier (pierburg carb) by 5° when going from leaded to unleaded... so if going from E5 to E10 has a similar effect, then timing would be adjusted in the same manner.

Unfortunately, we are all running on 30 to 40 year old documentation... really, an up to date official VW technical bulletin would need to be used to verify the current situation - if such a thing exists for our vehicles.

[ajsimmo]

That Bentley digijet timing is the US spec, early version on a 1.9, so a DH or GW, and the 5°ATDC is presumably with vacuum retard connected (and often with a lambda sensor). It's not really relevant to or comparable with the European DJ spec of 10° BTDC with vac disconnected and plugged (no lambda sensor).

Sent from my moto g(30) using Tapatalk

[Robsey]

Ah yes...

Just looked at the Haynes book of lies.
Only the DF is after top dead centre.

DG, EY, and SP (?) are all 5° before TDC
Along with MV, SR and SS.

GW / DH and DJ as follows:-
10° before TDC for 98 ron
5° before TDC for 95 ron.

So to maintain relevance... does adding more ethanol lower the ron value?

If it affects one, it would affect the other (in theory).

It never affected my 1994 Cavalier with cat but without knock sensor when I moved from unleaded to 5% ethanol, so I cannot see it needing any changes to bump upto 10% ethanol.

I would assume any difference in running is due to the usual causes -
Need for a service,
Or deterioration of fuel hoses, lines, carb, injectors, or tank. And moisture absorption in older / stale fuel.

As you were, Mr Stesaw.
Apologies for the brief interlude of mis-information and confusion.

[silverbullet]

I have a feeling that the SP was a carb 2.1 for a specific market.

[maxstu]

I have a feeling that the SP was a carb 2.1 for a specific market.

SP 1.9
SR 2.1.
Both are carburettor versions for the Swiss market.
I got chatty with a fella on here living in Switzerland.

[tobydog]

From personal experience with my 1980 Mk 2 Moto Gucci Le Mans which was born to drink 100 octane or the old 5 star juice. It pings under load at low revs with lower octane fuel, premium E5 is usable with a measure of empathy, just have to be wise to not labour the engine at low revs under load. The timing is set at original spec. Not sure if you'd be aware of anything amiss being so detached in a T3/25...

So, if I were dragging a caravan along, I'd go for the nice stuff. There again, Hell would have to freeze over before that happened

[Gavrilo]

If any one is putting E10 in a vehicle with a carburetor they should be aware that E10 contains more oxygen molecules than E5 meaning the engine will run leaner (hotter) unless it has been adjusted to suit, I fitted a A/F ratio meter so I can adjust the carbs to run best on what ever I chose to fill it with, and generally keep an eye on the mixture

[maxstu]

If any one is putting E10 in a vehicle with a carburetor they should be aware that E10 contains more oxygen molecules than E5 meaning the engine will run leaner (hotter) unless it has been adjusted to suit, I fitted a A/F ratio meter so I can adjust the carbs to run best on what ever I chose to fill it with, and generally keep an eye on the mixture

Got some details and a photo?

Another conundrum.....

From a previous MOT for Oct 2022 the fuel injected early 1.9 had the following emissions. Running 5 degrees using E10.



Since fitting the rebuilt 2.1 l've covered two thousands miles using E5 with timing at 10 degrees. Today's MOT recorded double the emissions. Is this good or bad?



Regards,
Stuart

[Stesaw]

My 2.1 sits around 2% stu. That was with a quick fiddle with the o2 screw at the mot station.
I think I'll swap to a FI system at some point, maybe Marco's if I get some burnable dosh in or speedshops kit perhaps. But with Marco's hes offering a turbo setup

[maxstu]

My 2.1 sits around 2% stu. That was with a quick fiddle with the o2 screw at the mot station.
I think I'll swap to a FI system at some point, maybe Marco's if I get some burnable dosh in or speedshops kit perhaps. But with Marco's hes offering a turbo setup

Did it stay at that setting thereafter? Any improvements to note?
Perhaps the low figures from the 2022 MOT are due to running E10?
I'm going to reset timing and run E10 for now on the 2.1 (2000 miles since rebuild) until next spring when l drag the Rapido out from under the carport for next years camping.

[Stesaw]

I run on e10 most of the time currently as Its a daily. To be fair I really should get it on a rolling road to get it adjusted right but its extra £ thats going into other things right now. It was adjusted at the MOT place at the start of the year, haven't checked the emissions checked since.
I did toy with the idea of a wideband sensor as the speedshop exhaust has a bung for an sensor in it. Just so I can monitor and adjust it myself.
Still on the shortlist of potential options.

[maxstu]

Just back from a four night trip to Eastbourne. No caravan this time. Bliss!

Before setting off l put timing at 5° and used E10 over the 450 miles covered.
Averaging around 21mpg of mixed driving conditions, often in rainy and windy headwinds.

However, on the return home we visited someone in Finchampstead, near the M3. After that we hit the M3 motorway and covered 115 miles in just two hours. I didn't sit back at the usual 55mph. This time l decided to flow with the general motorway traffic and maintain 65mph and above at times.

Great fun! I think we made good use of a westerly tailwind!

Satnav on phone against vehicle speedo:

50mph = 52-53mph
55mph = 57-58mph.
60mph = 63-64mph.
66mph = a steady 70mph. Preferred speed.
72mph = touching 80mph? And more for overtaking purposes only.

The engine loved it. The hightop not so.