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IYO Is a sidedraft Weber bad choice for road racing

Old 02-06-13, 12:12 PM
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Red face IYO Is a sidedraft Weber bad choice for road racing

What's some thoughts . I just picked up a weber 45 for my 12A Streetport from a guy for a good price that has all the right jetting for the streetport. I don't want to replace My Holley 465 with something that's going to have the same problems in corners. My question is the problem of bogging. Is this an intolerable issue with the sidedrafts?
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Old 02-06-13, 02:34 PM
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GAH they are horrible for road racing. thats why formula mazdas have been using them since the 80s

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Old 02-07-13, 06:53 AM
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Holley's will bog when used in road racing. It is a symptom of their fuel bowl design. You can minimize it with all kinds of tricks, but the high G bog will still be there. The Weber is a completely different design of carb and the work extremely well in road racing and have been used since the 60's with minimal to no issues.

Buy it and put it on. You will love it as long as its in good shape and tuned properly.

Eric
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Old 02-07-13, 07:23 AM
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The carb design is fine for road racing. The manifold you need is the problem. Runners are too long to make top end power.
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Old 02-07-13, 07:32 AM
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Okay so the weber I got will work, but the IDA is what would work best obviously that's what people are running these days. I will loose Horsepower in the upper powerbend in comparison to the IDA counterpart because of the longer runner.Got it
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Old 02-07-13, 08:21 AM
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Originally Posted by Adam12A View Post
Okay so the weber I got will work, but the IDA is what would work best obviously that's what people are running these days. I will loose Horsepower in the upper powerbend in comparison to the IDA counterpart because of the longer runner.Got it
For a PPort with a Weber 51 IDA

http://rotaryeng.net/Weber58-24.5inc...yno-curve2.jpg

http://rotaryeng.net/Weber58-28inch-...dyno-curve.jpg

Port dimensions for the R26B

http://rotaryeng.net/Lemans-rotor-di...ns-overlay.jpg

Go to page 5 in this link and you can read and look at the graphs to see how intake runner lengths affect performance (torque, which will translate to power through big boy science)


Mazda 4-Rotor Engine Le-Mans
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Old 02-07-13, 06:24 PM
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Originally Posted by REAmemiya_fan View Post
For a PPort with a Weber 51 IDA

http://rotaryeng.net/Weber58-24.5inc...yno-curve2.jpg

http://rotaryeng.net/Weber58-28inch-...dyno-curve.jpg

Port dimensions for the R26B

http://rotaryeng.net/Lemans-rotor-di...ns-overlay.jpg

Go to page 5 in this link and you can read and look at the graphs to see how intake runner lengths affect performance (torque, which will translate to power through big boy science)


Mazda 4-Rotor Engine Le-Mans
Some of the tracks here have descent size hills so I'm hoping the torque might actually benefit me being able to pass on the climb
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Old 02-07-13, 07:20 PM
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Looks like 24.5 is better for racing but 28 would be much, much easier to drive on the street.

That said, with proper gearing the 24.5s would be lightyears faster than the 28s, even up hill.

Torque only matters on a race track when your gearing or driving sucks.

The powerband that gives you over 220 HP is 1300 RPMs wide (assuming a 7,300 rev limit) with the 24s but only 900 RPMs wide with 28s. By comparison, the powerband that gives you over 180 foot pounds of torque is 1500 RPMs wide with the 24.5s, and 1600 rpms wide with the 28s, which considering how much HP you gain, is not that much of a loss.
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