Pierburg 2E3 choke

[itchyfeet]

Awesome stuff CJ!

proper nerdy I love it

still need to know why my point bit is longer than yours?

[CJH]

still need to know why my point bit is longer than yours?

That's a good question. My suspicion is it doesn't matter and they both do the same job. If you look at the flat on my pointy bit and the equivalent flat on yours, they are both parallel to the flats on the spindle hole, and both seem to be a similar perpendicular distance from the spindle flats. So I suspect yours has the same function as mine - namely to act as an end stop when the choke flap is fully open. I'd even suggest that the one in my carb(s) could be the 'improved' design, since the pointy bit is shorter and maybe stronger. All of the carbs I've looked at (the two T25 carbs I have on the bench, as well as the LT carb I took delivery of today) have the the same design - yours is the odd one out. The only thing I'm hesitant about is the chamfered edge on one side of your pointy bit - is there something else inside your carb that this is supposed to engage with somehow?

[itchyfeet]

Will split my spare when I get a chance and investigate, the long one is in the carb on the van, fast idle is not working so at some point it has to come off too.
Just finishing central heating for the house after 11 years of being cold so not had much tinkering time recently.

[CJH]

I didn't get the parts from the laser sintering machine today - it was out of service for some reason. Hopefully next week. In the meantime the fella there did me a sample using a different machine. It's like a better version of the one that produced the earlier blue pieces. I didn't catch the name of the process or the material, but apparently it has a much higher melting point (a couple of hundred degrees) than the SLS nylon 12. The Nylon 12 melts at around 180 degrees but has a maximum working temperature somewhere below that - maybe 100 degrees. I'm not completely happy that that's high enough for this part. I think it probably is though, as I don't think it will get hotter than the coolant passing nearby in the choke heater housing.



The filament size is quite a lot bigger than the resolution of the SLS process, so although the spindle holes in this part are quite tight I'm fairly confident they'll be a better fit in the SLS part. If they're not I'll tweak the Autocad model.



I asked about prices for a small batch and was advised that a commercial service would be a better bet. 'Digits2widgets' was recommended. I looked into their pricing. The price for a single part would be £30 (ouch!) but they have a tray system, the smallest of which costs £40 and might just about fit around 60 pieces in. I don't really see there being a demand for that many (even the OP no longer seems interested), but given a choice between 1 for £30 and 60 for £40 I know which I'd go for.

[kevtherev]

I think even Bromyard might be interested.

[itchyfeet]

I'd buy some/chip in

[ajsimmo]

I'd keep a couple in my useful things drawer. Great work!

[CJH]

Not quite 60 to a tray - but 56 will go in fairly easily. At £40 (plus VAT) that makes them just 86p each. Once I'm happy with the CAD file I'll probably do a tray of 56 and then just post a link to the files.

[itchyfeet]

this other shape part is nagging at me, unless you are in a hurry perhaps wait until 'we' have investigated why there are two versions?

[CJH]

Not in a hurry at all. It would be easy enough to split the tray to have a mix of the two types. If you can take some measurements I'll draw it up for comparison. If you can't do that without dismantling your carb I can probably scale some approximate dimensions from your photo. My guess is that the flat on your pointy bit is on the same line as the flat on my pointy bit, meaning it would allow the choke flap to open to the same angle.

[kevtherev]

The one I have allows the flap to open completely vertical.
It rests on the carb body when doing so.

[itchyfeet]

I will have a look this afternoon
vans not running on petrol right so got to take a look anyway

[itchyfeet]

My guess is that the flat on your pointy bit is on the same line as the flat on my pointy bit, meaning it would allow the choke flap to open to the same angle.

I agree, just looked at the carb the longer one came out of and the mark on the body it presses against is lower down than the spare carb which has the shorter one.

The longer one is now in the van carb and the choke flap opens to vertical, same as the spare carb with the shorter one so they do the same job, I suspect the shortened it because it was breaking.

I guess 'we' need to road test one or two in carbs in summer heat before you sell them to anybody who's not prepared to be a guinea pig.

[CJH]

That's good then - just the one part to worry about then. So that chamfering on one side of your pointy bit doesn't have a specific function then? Gratuitous styling perhaps, on a part that's never visible?

Yeah, I was proposing to cook one of the nylon samples that I'm having made at various temperatures in my oven. It should melt at around 180 degrees, so I won't take it that high, but it'll be interesting to see what it's like at, say, 150 degrees.

[itchyfeet]

vans not running on petrol right so got to take a look anyway

Seen this many times before, something faulty you take it apart put it back , no sign if a fault but now it works ok.
Van won't run on petrol well, it lacks power, LPG is ok.
Check vac pipes all ok
Check dizzy vac module ok
Check 2e3 second barrel opens under vac ok
Check bypass cut off valve ok.
Check carb conical filter ok
Check fuel delivery from pump into jar ok
Check pilot jet ok
Try to split carb to check main jets but it won't split easily, it's getting dark so stop.
Start it and runs great, what was it?

Sometimes taking something apart and reassembling is enough to fix a fault.