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| Engines & Gearboxes for Dummies http://international2cvfriends.com/forum/viewtopic.php?f=7&t=882 |
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| Author: | samfieldhouse [ September 29th, 2009, 1:59 pm ] |
| Post subject: | Engines & Gearboxes for Dummies |
I didn't want the vans for dummies thread to go off topic and for other mechanically challenged people like myself I thought this might be useful so stuck it here. Jono wrote: The M28 and M28/1 engines are siblings of the 435cc engine, and all 3 were totally new units when introduced in around 1970. The M28 is fitted to most Dyane 6s, and has a 9:1 compression ratio, whereas the M28/1 is the 2cv6 engine, with a compression ratio of 8.5:1. I'm guessing the later Meharis has the M28 9:1 engine coupled to the low ration gearbox of the AKS400? Is that gearbox the same as a 2cv4 gearbox? |
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| Author: | toomany2cvs [ September 29th, 2009, 4:16 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
samfieldhouse wrote: I'm guessing the later Meharis has the M28 9:1 engine coupled to the low ration gearbox of the AKS400? <fx: checks Mehari parts book> No - 8.5:1 compression, no "turbo tube", and air filter on top (2cv position) rather than over the LH cylinder (Dyane position) or RH cylinder (Ami position). Quote: Is that gearbox the same as a 2cv4 gearbox? <fx: checks again> Can't tell - the part number for the box isn't an AY/AM/AK/AZ/A format one, but one of the awkward generic ones. HOWEVER, it does give two "replacement for:" part numbers, one AY (for USA) and one AK (for rest-of-world), which suggests that non-US Meharis did indeed have AKS400 boxes, may even have been the same as late 350s. The AY part number for the US box suggests that it was a Mehari specific set of ratios, since it was sold more as a fun car than a load-carrier, hence an expectation of lighter load, so wouldn't need such low ratios. There's no way it'd be a Dyane car set of ratios. 4th'd be unusable. There were umpteen different sets of ratios fitted over the years. Dyane 6 is different to both 2cv6 and Ami 8, f'rinstance. 'course, it's damn near impossible to tell now, because there's no way of knowing if a box is original to any specific car. The internals are a right mixed-bag of part numbers - 2nd gear is an AM part number, f'rinstance, so was first used in an Ami-ratio box. If anybody wants the Mehari parts book, I turned it into a 160Mb PDF a few years back. It only goes up to 9/74, though. |
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| Author: | JRW_91 [ September 29th, 2009, 5:57 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
Ooooh this is something i've been wondering for a while now.. 2cv6 box v Dyane6 box.... do the dyane gearbox's have longer ratio's equalling higher top speed? also if i had a dyane gearbox would i also need to put the heavy flywheel and the spring clutch back on with a dyane thrust bearing or can i mount a later 2cv6 flywheel to a dyane gearbox? thankssss 
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| Author: | toomany2cvs [ September 29th, 2009, 6:25 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
Gay_Joe wrote: 2cv6 box v Dyane6 box.... do the dyane gearbox's have longer ratio's Yes. When I bent my first 2cv, I moved the shell to a Dyane chassis - 4th was noticably higher ratio. Quote: equalling higher top speed? Not necessarily... A 2cv's top speed is rarely limited by running out of revs - unless you're tonking down a long steep hill. It's more normally a lack of power to overcome drag - easily demonstrated by tucking behind a big wagon or coach on the m'way. It's all horribly complex, and there's a large element of "You might not be able to accelerate to that speed without help, but once you're there you'll stay there" |
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| Author: | Sean [ September 29th, 2009, 9:59 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
IIrc Dyanes had lower 1st gear to haul its lardy arse off the line top was/is higher than 2cv top speed of a 2cv limited by it aerodynamics too  (i always laugh when those two words come together in a sentance) another benifit of the superior Dyanesean |
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| Author: | rebel2cv [ September 29th, 2009, 10:28 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
[quote="Gay_Joe"]Ooooh this is something i've been wondering for a while now.. 2cv6 box v Dyane6 box.... do the dyane gearbox's have longer ratio's equalling higher top speed? im not sure about dyanes being longer ratio, but i think the acadianes did as it gave it a bit more torque for pulling, or something like that.... wether normal dyanes had the same box.... not sure. |
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| Author: | rebel2cv [ September 29th, 2009, 10:32 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
also if i had a dyane gearbox would i also need to put the heavy flywheel and the spring clutch back on with a dyane thrust bearing or can i mount a later 2cv6 flywheel to a dyane gearbox? thankssss [/quote]i 'belive' that its all to do with the teeth on the shaft, you have to be careful and check that the shaft has the same amount of teeth, or you end up with a mess |
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| Author: | Lars E [ September 30th, 2009, 8:54 pm ] |
| Post subject: | Re: Engines & Gearboxes for Dummies |
I run with dyane gear box which original have run with the heavy (old) flywheel, now sits one of the new type. and it was just to swap things out. But you can not go the other way (using the old type of flywheel and clutch on a new type of gearbox, |
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