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MG Midget and Sprite Technical - Weber or not

Hi Guys

I’m currently restoring my midget 1500.

I have been told that an upgrade to either a DGV or DCOE Weber carburettor would potentially increase my fuel economy.

This seems unlikely to me, but could I have suggestions whether to upgrade from the twin SU's to Weber and which to choose if I do?

Could any positives and downsides be listed as well. Would the power output be increased?

Also it is a stock 1500.

Thanks

Rylan
R Williams

The DGV might equal and the DCOE will most likely be worse than the su's
A single big su might better the economy though i do not know about those setups for 1500's

And EFI setup with programable ignition curve will give the biggest improvement though i do not think you will get your investment back soon
Onno Könemann

On a stock 1500, going away from the twin 11/2" SU set up to twin Webers will not increase economy and is likely to result in a drop in power (and especially bottom end torque) owing to the fact that the motor has a relatively mild cam. Indeed there is no point in fitting Webers to anything other than a race motor.

You COULD fit a single Weber DCOE with a crossover manifold (from Moss - ex Triumphtune), or even a single DCOE parallel manifold but this will be expensive (plus you will need a new throttle linkage) and the clearance issues in a Midget will mean problems fitting a decent air filter.

Despite what Moss claim, in my (nearly 30 years of) experience with Triumph 4-pot, even a single DCOE on a stock motor will not improve power or torque and WILL result in poorer fuel efficiency. So whoever was advising you doesn't know what they are talking about!

The only advantage of a single DCOE as opposed to twin SUs is that, once jetted. it won't go out of tune and you don't get balance or linkage issues.

AFAIK there has never been a manifold available for the DGV on a Triumph 4-pot.



If you really want to go to a single carb set up (and I can't see why you would, but hey ho) then you could fit an HS6. To do this you would need to source a single carb inlet manifold and throttle linkage from a Herald 1200 or 1250 and make up an adapter plate.

Deborah Evans

Oops, I meant to say Herald 13/60. The 1200 and 12/50 have siamesed inlets.

Other options would be Triumph 1300 FWD or early Triumph Toledo or 1500 RWD (pre TC and pre-Dolomite).
Deborah Evans

<< "AFAIK there has never been a manifold available for the DGV on a Triumph 4-pot. >>

It's a regular stock item from both Moss and VB over here.

As far as economy goes, I get 30-35 MPG from my DGV Weber (stock 1500, + .010" overbore). Actually the 35 was a test run on flat ground, one tank of gas, very gentle on the throttle. Real-world mileage for me is closer to 30 MPG (USA), plus or minus. Don't know how that compares to twin 1 1/2" SU's. The jetting on mine has been altered (leaner) than as normally shipped for Midget 1500. I can't imagine the car has more HP/torque than your stock setup, but I've never driven the twin SU setup to compare.

Upsides: No carb balancing: set it and forget it. No dashpots. Eminently tweakable (aftermarket jets, tubes, linkages, etc). I've leaned mine out on the primary circuit for economy, and am still working on getting the secondary fatter and stronger. Less apparent heat sensitivity: mine has no heat shield at all and runs just fine thank you.

Downsides: Erm... Not as pretty as the twin SU's? Seriously, if performance is really an issue I would try to find data comparing the two. My gut says the twin Su's are peppier in the low throttle/rpm range (the 1500's bread-n-butter) than the Weber DGV, but that is pure speculation on my part.

HTH, Richard
Richard Reeves

Hi Richard

When we played with a downdraught on my mates MGB we thought the sus were peppier, even though we gained a little top end, it is a shame I didnt have my new rollers back then (is that the makings of an oxymoron?)I could have had detailed bhp differences at all rpms. When we added stiff return springs it felt the same as the sus!

Not suffering from heat problems seems a blessing with 1500s.

Peter
P Burgess

I forgot to add, the 1500 kits for Midgets and Spitfires are available in the UK from Webcon;

http://www.webcon.co.uk/pages/ClassicPowerIndex.htm

Peter
P Burgess

That's what I love about this BBS - always something to learn. :)

Thanks Peter and Richard!


Addendum:

Looking at the DGV manifold does make me wonder as to it's efficiency though, given the nature of the turns in the tract and the differing lengths between 1 & 4 and 2 & 3.

http://www.webcon.co.uk/shop/shopexd.asp?id=10656
Deborah Evans

This thread was discussed between 01/06/2011 and 02/06/2011

MG Midget and Sprite Technical index

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