Stu 18 Posted December 10, 2007 As above, ive trawled through pages of search results with some people saying they arent big enough, whilst others saying they'll do and such, so, my question is this, how much air does a stock Mi need to work effectively? How much air can a set of 40's supply comfortably? What does choke size mean? i.e, is a 45 with a 36mm choke as effective as a 40 with a 36mm choke? or cant this happen? Is this where the restriction lies? Share this post Link to post Share on other sites
Baz 421 Posted December 10, 2007 40's will be fine for an Mi, there's not really any need to go any larger. It really depends what you want to build the engine for. Chokes will be around 36mm for the best all-round setup anyway. You can go into more detail etc, researching flow, VE etc, but it's really as simple as basically the bigger the carb, the more air/fuel you'll pull at higher RPM, but there's a sacrifice lower down. -In very simple terms as i understand it anyway. Choke size is the size of choke/throat, so a 45 carb with 36mm choke will be exactly the same as a 40 with a 36mm choke. Share this post Link to post Share on other sites
danpug 1 Posted December 10, 2007 Thats the bit i don't get, for example they run much more expensive 45's with 36mm chokes when they could run 40's with 36mm chokes? Is there something i'm missing? Share this post Link to post Share on other sites
Baz 421 Posted December 10, 2007 I've wondered that too, perhaps it's just a case of being able to upgrade to bigger chokes later if need be, or just a pub-talk thing... I'm sure someone more knowledgable than i will come along with a much better definition than I!! Share this post Link to post Share on other sites
welshpug 1,622 Posted December 10, 2007 why not use throttle bodies? cheaper!! Share this post Link to post Share on other sites
Baz 421 Posted December 10, 2007 why not use throttle bodies? cheaper!! That's a bold statement, and a debatable one... Cheaper why? Not as in buying costs when you factor in a Management system that's needed to run them. Running costs, perhaps, but again debatable. prove me wrong though!! Share this post Link to post Share on other sites
welshpug 1,622 Posted December 10, 2007 yeah a rather bold one I guess simply from my observations and from comments by respected tuners, it sounds like throttle bodies are that much better than carbs in so many ways. i.e cheaper to buy the bodies themselves, of course you have to factor in the extra cost of mappable management. But then you have the setup for the carbs, which go out of tune quite readily it seems, not something you have trouble with when using throttle bodies as they only need to be mapped once. and the fact that throttle bodies can start in cold and hot weather, return good MPG (I haven't heard one story about carbs returning good MPG on a 205...) but that's just my viewpoint, I dont run carbs/throttlebodies, only a Motronic converted 8 valver, but I'm sure Miles and quite a few others will agree with me Share this post Link to post Share on other sites
matt-k 0 Posted December 10, 2007 Im about to fit my twin 40 carbs to my Mi this weekend all in its cost me £325 this includes buying second hand carbs & rebuilding them, the manifold, dizzy adapter, leads, everything. Patience & Ebay is the answer! Ive heard people comment on 40s not being able to flow more air than the standard set up but surly thats rubbish as the 2 openings on the standard TB are less in area than on the 4 chokes the webbers provide so of course they'll flow more air! As for fuel economy who cares! I dont drive far in my 205 and im sure it will sound great when it finally runs. Matt. Share this post Link to post Share on other sites
Baz 421 Posted December 10, 2007 (edited) yeah a rather bold one I guess simply from my observations and from comments by respected tuners, it sounds like throttle bodies are that much better than carbs in so many ways. i.e cheaper to buy the bodies themselves, of course you have to factor in the extra cost of mappable management. But then you have the setup for the carbs, which go out of tune quite readily it seems, not something you have trouble with when using throttle bodies as they only need to be mapped once. and the fact that throttle bodies can start in cold and hot weather, return good MPG (I haven't heard one story about carbs returning good MPG on a 205...) but that's just my viewpoint, I dont run carbs/throttlebodies, only a Motronic converted 8 valver, but I'm sure Miles and quite a few others will agree with me I see where you're coming from, as i used to think the same way, but why would a decent carb set-up right just fall out of tune? Carbs also start in hot and cold weather, yes you may have to persevere with them a bit more but they do work, comes down to set-up again i suppose. Also, again if set up properly, then they don't have to be as thirsty as some make out, either carbs or TB's will be thirstier than std of course though! Mapping is expensive for TB's, yes you can learn and do the basics yourself, but i see where you're coming from, although every little change you make will make the need for another re-map! I don't run either atm either, but i've had carb-fed cars in the past, and although i didn't understand them as much as i do now, they were never that bad iirc. I have a set of 40's, just undecided which car to run them on (have to explore class regs etc) or whether to at all, i'd ideally prefer a TB setup soon on the Mi, particularly as i'll be able to tinker and learn with a rolling road. Swings and roundabouts i guess, depends which way you're inclined, there probably isn't that much in it cost-wise all in. Edited December 10, 2007 by BazGTMi Share this post Link to post Share on other sites
matt-k 0 Posted December 10, 2007 Here's a handy link which may help explain things, Clicky Share this post Link to post Share on other sites
Miles 331 1 Cars Posted December 10, 2007 The other thing you need to remember on the Mi16, S16, GTi6 etc (Not to the 8v) is you loose power by dumping the igntion mapping and mid range Finally finding someone who can tune carb's is getting harder these day's as most just map TB's Share this post Link to post Share on other sites
Stu 18 Posted December 11, 2007 My idea was to go to twin 40's with a Megajolt, with the exchange rate being so good at the moment the fully specc'ed MJ is around the £50 posted, thats provided you dont get stung for any import duty. Ill keep looking for some 40's then, ive missed loads of sets on eGay as i thought they werent big enough.. Share this post Link to post Share on other sites
Longun 1 Posted December 11, 2007 I'd be interested to see what gains are given as I've got a set of 40's and would only need to get a few things to fit them on my Mi. Share this post Link to post Share on other sites
