Im getting stuff together to fit Dells on my motor but aiting for summer for this. Ive been running a single twin choke weber for a long time (DFEV I believe) bit of a pig in cold weather as starts fantastic but bogs badly once the choke comes off and before the engine is properly up to temp. I fancy having a go at sorting this Theres been a lot said over the years on this conversion, particularly regarding the tendency for fuel to condensate on the runners due to their length, low mass and lack of the preheat you would have on a type 1 motor. Ive seen various adaptations on the net for "boxing" the filter and feeding it warm air from the standard heat riser for the original solexes so I may have a go at this and possibly use a standard air filter box. Another option is to electrically heat the runners and as luck wouldnhave it I have a 12 v heater that should do the trick. Had a play tonight and it looks as though it will provide a=enough heat to get a resonable temp (about 50 deg) but that will fall when the engines drawing fuel through. Anyone any experience of IMDUs and whether they have any affect at all. Anyone got a well fettled twin choke on. let me know . ta
IMDUs don't have a great reputation, and are generally regarded as a bit of a bodge. I'd buy the Dells now!
I'd be interested to see what you come up with, I've just bunged one on until i do a full rebuild of the engine with some upgrades and i can see what you mean about the bogging down, though i'm currently running a 009 i reckon changing this will help, are you running a vac advance distributor? for manifold heating i was looking into 12v element wire and possibly making a kind of wrap for the pipes. though tbh i'm not sure about carb icing it very much seems to be a case of loads of people say it can happen but no one has ever actually seen it. There's loads of info about jetting on the net too, and again from what i've read if you get this right the weber progressive can be quite a good carb. I will be playing with mine over the next few weeks to see what i can do with regard to tuning and also i'm waiting on a accuspark vac advance distributor to see if this helps with the bogging down, but mine fires up very quickly too, (a lot quicker than the dual solex's on the other bus)
IMDU will warm the manifold.... eventualy. I experimented with one on a manifold in free air and came to the conclusion that by the time any possibly beneficial heat transfer had taken place the engine would have been running underload for 10/15 minutes anyway. One possibility was to have it switched on as a manifold pre heater an hour or so prior to firing up. Since I was not living within the Arctic circle it was really pointless.....exit IMDU... should have saved my money IMHO.
Thanks guys. Im running a vac advance dissy from a 2 litre T 25. The issue isnt (in my mind) just to put heat into the mainfolds when the motor is cold but to keep them warm all the time as the temperature atop the engine is pretty damn low due to the amount of air being shifted through the cooling system. The cold manifold with little benefit from conduction of heat through it from the head due to being constantly cooled by the air changes in the engine bay and also the vapouristaion of fuel through the carb also cools it as it takes the heat it needs to vapourise from the air being inducted through the carb. Theory is theres insufficient heat to properly vapourise the fuel or that the fuel re-condenses into droplets instead of being a mist in the manifold. From what ive read and a bit of common sense then feeding the carb some warm air and heating or keeping the manifold warm should have some benfit to warm running but should help as the engine waems up. The imdus ive seem so far only heat the centre and thats only partly where the issue is. Ive got some heaters but not sure the wattage is high enough. They are taking 2 amps each so around 24 watts. Read somewhere imdus are around 120 watts!!
Perhaps IMDUs have been uprated a bit since I tried one where the wattage was more like 12 to 20. ) 120W would be of more use but being tagged through the ignition feed as per the original design would not be an option. I like the idea of initial induction manifold heating but haven't pursued the idea further.
Thats a little more reassuring as my heater got a 6 inch piece of pipe-lagged 1,1/2 box section up to a temperature where I couldnt compfortably hold it for long in about 5 minutes (seems my thermometer is a bit off!. I think Ive got two twin element heaters which should give me up to 96 watts if Ive got my measurements right. (need to use a more accurate meter). Would be 8 amps if I used all, would run a relay off the coil I think and connect to the battery. Need to find some sort of heat resistant insulator now that will fit in the gap between the manifold and tin. Its a bit tight for pipe lagging.
with the dells you will be doing the oposite and trying to stop the fuel in the carbs boiling off when you stop .Don`t wait till summer fit the dells now . The IMDI i had on a beetle years ago was a waste of time . Twin carbs is the way
Agreed, I think the electric heating element will need to be very powerful for your idea to work. I had an Imdu on a beetle years ago and it was useless, exhaust heat was really needed to warm the manifold. It might heat a manifold at room temp but when it's got vaporised petrol whooshing through it it'll be a different story. Use the money spent on this to put towards the dual carb setup
I take your point and I will but this will cost bme next to nowt and Ive a bee in my bonnet. Also no way Im swapping to dells as ive next to no chance of setting up in this weather. I dont have to do anything really!
