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SU's vs Weber's....... again

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Westfield_XI

Westfield_XI

Jedi Warrior
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Interesting comparison test in the current Classic Motorsports magazine. It seems they both make the same power, at least on the engines they tested,(a stock MGB engine and a 1380 A-series) the numbers are the numbers after all. But there is room for disagreement at least regarding their comments on tuneability and driveability. The article isn't online, so no link, sorry.
 
Vizard says the same thing in his book but no one can explain (to me) why a Weber equipped 1275 goes much faster than the same 1275 with SUs, HS2s or an HIF6.
And if the Weber gets 20 mpg and the SUs get 30 mpg, again on the same car, something doesn't add up.
I had a 45 DCOE on a Sprite and it was great, that same Sprite now has dual 1.25 HS2s and is still fine just not as fast.
Same test was on an Austin A40 with a 40 DCOE, much faster off the line with the Weber but 20 mpg at best, now it gets 32 mpg with a single HIF6.
Vizard shows in his book how the HIF6 and the DCOE flow the same amount of air.
But he says nothing about gas. My engines run on GAS :wink:
 
spritenut said:
Vizard says the same thing in his book but no one can explain (to me) why a Weber equipped 1275 goes much faster than the same 1275 with SUs, HS2s or an HIF6.
And if the Weber gets 20 mpg and the SUs get 30 mpg, again on the same car, something doesn't add up.
I had a 45 DCOE on a Sprite and it was great, that same Sprite now has dual 1.25 HS2s and is still fine just not as fast.
Same test was on an Austin A40 with a 40 DCOE, much faster off the line with the Weber but 20 mpg at best, now it gets 32 mpg with a single HIF6.
Vizard shows in his book how the HIF6 and the DCOE flow the same amount of air.
But he says nothing about gas. My engines run on GAS :wink:
Click to expand...


Now granted I've never had a 45DCOE on my 1380 but I have had a HIF6 and now run HS4s. Noticeably more power. I'd bet the gain from a Weber (love 'em..have them on two of my Land Cruisers)over twin HS4s would be negligible.
A 45 DCOE would surely have more go than a HIF6.
Those twin HS4s dump plenty of gas for my 1380 with a cam,
head and header. The exhaust is louder with the HS4s vs HIF6.
No kidding. It's noticeable. Fuel mileage? I haven't checked but I'd bet those HS4s suck way more fuel than the HIF6.
I just like the "look" of twin carbs on a Sprite.
Goes plenty fast enough for me.
:jester:
 
Failing memory, but I believe that one of Vizard's thoughts was that the size of the fuel droplets - the success of the air/fuel atomization - was different between the Webers, SUs, and (I think) Dellortos, and that might have accounted for some of the differences. I think he did some pretty solid comparisons using the same engines and different intakes as well, but my book is currently loaned out.
If anyone is seriously interested in understanding the A series engine, his book is excellent even though it was put together a fair number of years back.
Doug
 
A weber sidedraft is kinda like a adjustable coil over shock, tube frame race car, it is very tune-able, enough so much, that the average guy can tune himself right out of the park :smile:
 
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