Carsnz123 Posted November 17, 2016 Share Posted November 17, 2016 Someone with more knowledge than me lend me your wisdom. I'm doing a bike carb mod on my 1.3 mk2 golf and I've got a choice between a set of Keihin VE64B 34mm carbs off a 1987 CBX750 or Mikuni BDST32 32mm carbs off a 1995 RF400. The plan is to have a hot cam and headers to improve breathing and gain some ponies. so does anyone have any idea which carbs will be better? Quote Link to comment Share on other sites More sharing options...
dave Posted November 17, 2016 Share Posted November 17, 2016 Look on the polo forums In the uk pretty common mod on them My old 1300 polo had gsxr750 carbs Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 17, 2016 Share Posted November 17, 2016 If in doubt with carbs ALWAYS go smaller. Unless you spend 99% of your time at 100% throttle and at near to top speed - air speed is your friend. Small = Better. 2 Quote Link to comment Share on other sites More sharing options...
Carsnz123 Posted November 17, 2016 Author Share Posted November 17, 2016 I was sort of leaning towards the 32s as the original carb is a 19/23. I think the newer carbs probably will perform better as well. 1 Quote Link to comment Share on other sites More sharing options...
Unclejake Posted November 22, 2016 Share Posted November 22, 2016 leaning towards the 32s as the original carb is a 19/23. I may have just messed up these calculations, but right now in theory you have an available 1,385 mm2 of air pass through area in your single twin throat carb, but you are heading to 3,216 mm2 (assuming you're going to 4x32mm carbs). Quote Link to comment Share on other sites More sharing options...
peteretep Posted November 22, 2016 Share Posted November 22, 2016 Because they are cv carbs they should have more room for inaccurate sizing, as the port gets bigger to suit the air speed. I think either size will work OK in this case Quote Link to comment Share on other sites More sharing options...
Carsnz123 Posted November 23, 2016 Author Share Posted November 23, 2016 I may have just messed up these calculations, but right now in theory you have an available 1,385 mm2 of air pass through area in your single twin throat carb, but you are heading to 3,216 mm2 (assuming you're going to 4x32mm carbs). I think you did a little. My calculations show 699 mm2 original carb and 3216 mm2 for new set of 4 32s. Seeing as each carb is going to be independent you really can only look at one cylinder. So it has gone from being able to draw through 699 mm2 venturi at WOT to 804 mm2 per cylinder. about a 15% increase. The next trick is to design manifolds which are tuned to give it a ram effect torque boost. Quote Link to comment Share on other sites More sharing options...
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