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When looking at your power-graph, there is a dip around 4500 rpm, this is from bad cylinder filling att that point (the sound waves is not right, mostly in exhaust)

If you get them right now, (modified exhaust) there should be a different filling at that part and, maybe, skimming cold be wrong way.

If you show me the ignition curve/map (in the ECU) a better judgement could be made.

Peak torque should be expected to 170 - 180 and should occur around 4500 - 5500, since yours is not, it is hard to predict the result of skimming.
(if we stick to the existing graph, a skimming would have helped everywhere, but maybe not in 2500 - 4000 range)

bmw2101 skrev: ↑fre apr 02, 2021 10:48 am if i was to put carbs on this engine, would a pair of hs6 carbs be too small, as in Su 1 3/4? I can do this legally and there is no restrictions.

There is also the stromberg 175 which is simular.

thanks

They would be better than the F manifold but there is no stock 2 carb manifold for these engines as far as I know.

Erland

i can have a manifold made, that is ok, its just for injection i cant do any modifications.

what is that manifold from? my mate here in the uk has one modded to take split 50;s but as far as i can see the 50 dcoe can only do 46mm choke size. So the zenith or the su is not far off that at all.

i can get a manifold made, or make one myself, i think itll open up the inlet restriction problem. The plan i have for the carbs, i cant really say, but they wont have flat spots etc, itll run " just like injection "

But you are not allowed to use dual Webers?

Erland

no only 2 barrels of the carb, so i can do this/



click here


that is use one side of the carb, or i can use one carb.

One Weber would probably be the best then.

Erland

I have built and used different manifolds with 2 carb inlets, built from both K (no interconnecting plenum) and A manifold (interconnecting plenum), as well as the cast manifold for a single DCOE.
Less work to get the DCOE to run right as you can change the jets instead of modifying the needles in the SU type carbs, but those manifolds leave a little to desire otherwise, so a single plenum would probably be better. You'll might lose some possibilities for length of runners compared to F manifold, but gain some flow most likely.

In older days SSK gave weight reduction to 2 ported cars versus dual carbs.
A plenum manifold built from a B20 E manifold with an 48 IDA carb were said to give more power than IR carbs.
So a plenum manifold could be worth a try.
I have thought about it on my 244 road racer because the dual 50 DCO carbs are taking 20CFM off the flow.

Erland

Who made those cast manifolds for a single DCOE? Never seen them before, only seen the B20 Lynx and Misab single DCOE intakes.

No they were bought, not sure what brand they were, not the best casting as they had a lot of pores.
I've had one for B20 as well, but can't recall if the quality was the same.
I've never had any of them on a dyno to compare, but I my guess is that the twin SU is better if one doesn't mind the extra work. (or a single plenum with straighter runners and a single DCOE)

right i have just bought a set of twin stromberg 175 carbs, where can i get one of those aq140 inlet manifold s from please? I may end up making my own though if i cant get one.


thanks

I'm not sure, maybe search the web for used ones, I think I've seen someone selling modified A manifold as well. But if you know someone that can weld aluminum and machine it for you it's done pretty quickly, the material is good to weld in as long as you clean it well.

Rewelded manifold for B230 and 2x carbs can be found here, klick on "delar"

https://www.mickegron.se/