Tuning DCOE 40's

[RichP]

Hi

Been searching Amazon for a good book on tuning Weber DCOE's, but those listed seem to get very mixed reviews, some ok and some distinctly critical.

Can anyone recommend anything? I don't doubt a RR session is the best solution but at the moment I've no idea how they work, which bit is which or even how to adjust the mixture (ref previous post concerning popping noise which may be due to running lean).

Cheers

Rich

[xflowphil]

Hi Rich

A good place to start on info for weber set up is dave Andrews home page at: http://members.aol.com/DVAndrews/

Books that I can recommend would be Des Hammills book on 'How to build and power tune Weber and Dellorto DCOE and DHLA carburettors' (from Speedpro). Also, Haynes do a weber manual which covers the DCOE carb and i found it quite useful for explaining exactly how the DCOE works, though i'm not sure if it's still in print.

Hope this helps

Phil

[Tigger]

Have you seen THIS ONE

Apparently quite good or go to the local library and ask them to order it in for you. Cost = couple of quid

Tigger

[RichP]

Hi xflowphil

I'm also running xflow and would be interested in what you find works - I'm not convinced mine's running right at the moment.

xflowphil & Tigger,

I'll take a look at the books 'n link - thanks.

[Hammy]

Whilst you are carb fiddling bear in mind that the carbs will show up "faults" elsewhere; plugs ignition etc need to be spot on. There is a lot of stuff on this forum

I particulary noted that fitting Mega jolt  igntion (plug again!) made my car perform a whole lot better in terms of drivaviblity -reducing pops/bangs etc.

If you have any distributor based ignition system , you won't have vac advance, which means your part throttle ignition advance will be wrong (by about 20 degrees!) and drivabilty suffers- giving the appearance that the carbs are set wrong, hesitation, spitting and so on.

[RichP]

Hi Hammy

I also think this may be a problem. Ive only just bought the car - the spec sheet says it has Aldon ignition but I've yet to determine how effective this is. I think mid throttle performance is off - seems to missfire quite a bit.

Is the megajolt fitment an engine out job or can I retrofit with the engine in situ, should I decide to take that route?

[Hammy]

Megajolt is an "add on" igniton system  requiring no internal mods or engine out - There is tons on the forum about it and on the web. Basically it consists of the Megajolt unit ( which is the brain/ECU/ copmuter parts). Using a crank poistion and throttle position sensor it allows a map to be generated to give you the correct timing advance at a variety of rpm and throttle openings. Cost about £170 for all the bits for DIY install.

With a distributer based system you only get a mechanically set advance curve related to engine rpm. Mega jolt allows you to have further advance settings dependant upon the throttle opening (simplicstically the approximation usually provided by a vacum advance, which is not fitted if you have twin 40's)

- you might just be missing that extra part throttle advance. Carb knowledge is well worth having too!

- there are a few pics on my web link

[RichP]

Thanks Hammy

Do you know if Bill Shurvinton still builds the units and if so how I can get hold of him?

[Hammy]

Bill no longer builds the units -there is someone else who now does 'em -can't recall name tho- have a look tho other postings name should pop out.

[Jenko]

Going back to books on carbs.....It's very useful to understand them...BUT, IMHO, you cannot really get the best from them until you visit a rolling road........Of example, on my car the calculation for main jets cam out a 145's, however, on the rolling road it was found that 130's gave better performance. So although you can get close, the rolling road is the place to tune them correctly......

I would have a sit back and think ahead...if you do decide to go for Megajolt (which to add to Hammys post will make a huge difference over a distributor based system)...then you would be better of fitting that before you make changes to the carb jetting.....THEN, you can visit a rolling road, set up the jetting, and also write an ignition map for megajolt......

HOwever, you can set your idle mixture, and balancing yourself  by reading the Dave andrews article....well worth a go.....

Good luck...

Paul.

[RichP]

I'm fast learning that things are not as simple as they first seem!

Following responses to this post plus other boardroom research I'm thinking of going for the Megajolt system first (scared to death of screwing it up though!) and leave the carbs alone. After that, a trip to NMS for a RR session and to map the megajolt.

I've sent a message to Martin (martin@millener.com) to source the MJ unit etc

Might also buy the book on Webers tho just to understand what's going on!

My first plans for a cost-free quick tweek with a screwdriver have already expended to ignition system replacement and I've only had the car 6 days!!

Thanks all

[bill shurvinton]

Personally I think the speedpro book is a waste of money. I sent mine back. DVAs website, combined with Dave Walkers book on engine management (which has a carb section) and a copy of Passini (sadly out of print but I can lend people mine) gives you 90% of the information you need. The final piece is Webers own DCOE handbook, which Ihave mislaid at the moment. This is good because if you have that, it tells you what all the silly f numbers acutally mean.

To learn how webers work is not hard, but takes some time. I keep meaning to put together a weber 101 talk I can give but as ever the kids have other ideas