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| Vacuum advance https://www.ausmini.com/forums/viewtopic.php?f=2&t=94460 |
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| Author: | Minicooper4me [ Wed Dec 21, 2016 12:27 pm ] |
| Post subject: | Vacuum advance |
When the Cooper S came out with twin su's, there was no vacuum advance unit on the 23d distributor nor was there a little stub on either su for a vac advance connection. I have twn su's and a 29d distributor with vac advance but not used. Has anyone out there tried to fit a connection on either su for the vac advance or am I wasting my time trying to do this. Thanks. |
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| Author: | timmy201 [ Wed Dec 21, 2016 12:36 pm ] |
| Post subject: | Re: Vacuun advance |
The 997 & 998 Cooper and normal cars had the vacuum advance barb on the body of the carb. There's no reason why you couldn't swap one of the carbs to one with a barb as long as it is the same spec as your other carb. |
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| Author: | Minicooper4me [ Wed Dec 21, 2016 1:49 pm ] |
| Post subject: | Re: Vacuum advance |
I did look at this Timmy but my carbies have just been reconditioned and are in very good nick. Is there a way of machining what I have and install a small connection ? |
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| Author: | greyghost [ Wed Dec 21, 2016 3:02 pm ] |
| Post subject: | Re: Vacuum advance |
put it in the spacer |
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| Author: | simon k [ Wed Dec 21, 2016 3:16 pm ] |
| Post subject: | Re: Vacuum advance |
or in a vacuum port on the manifold (if you have one spare) vacuum advance is an economy device, it won't make it go faster... |
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| Author: | timmy201 [ Wed Dec 21, 2016 3:25 pm ] |
| Post subject: | Re: Vacuum advance |
You can get the ones in the spacer, but they get vacuum from the opposite side of the throttle blade. This means you'll get advance at idle, with the factory position you don't get advance at idle. http://www.minispares.com/product/Class ... FA132.aspx |
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| Author: | Minicooper4me [ Wed Dec 21, 2016 9:33 pm ] |
| Post subject: | Re: Vacuum advance |
simon k wrote: or in a vacuum port on the manifold (if you have one spare) vacuum advance is an economy device, it won't make it go faster... That's exactly what I want Simon. A bit better economy. |
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| Author: | minimanic [ Thu Dec 22, 2016 8:48 pm ] |
| Post subject: | Re: Vacuum advance |
The vacuum advance is designed to advance the timing at small throttle openings and little load conditions. This happens basicly only at light throttle cruise. The port in the carb is designed to supply the vacuum signal at this time. Connecting the advance to full manifold vacuum at a manifold port or a spacer plate will pull full advance at idle, which is not what you want. I have drilled and installed a barb into many S.U's and it works quite well, BUT you have to get the position EXACTLY correct or it will not work as intended. The benifit of a vac advance distributor will only be noticed when driving in the conditions where there is vacuum applied, ie small throttle openings and little load conditions. If you get the vac signal wrong it can pull on advance or not let it go at the wrong load settings. This almost certainly will cause damage to the engine if not a major failure. Ignition wise there is no substitue to having the advance curve properly set by someone with the specialist machine. This can make a huge difference to a motor. Fuel wise if you want to set the motor up properly for best economy / power then the mixtures need to be checked with a wide band 02 sensor or similar. Many factors can effect fuel usage and power. I.e if the cam timing is out even by a few degrees. This is common when a reground cam is fitted and the timing gear refitted without dialing in the cam. A fresh motor may also not be as efficient as when it is run in. Hope this helps, Ben. |
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| Author: | Minicooper4me [ Thu Dec 22, 2016 9:40 pm ] |
| Post subject: | Re: Vacuum advance |
Thanks Ben, have compared the twin Su's that I have with a single type with the vac advance port fitted. It looks relatively easy to fit a vac adv port in a similar position on to one of my carbies, will do that, not losing anything out of it. Most of the time the engine will be running under light throttle opening so the vac advance would be beneficial for economy. It's not the price of the petrol, I just want a better range out of a tank. I'm getting 30mpg now, so 35mpg or better should be quite achievable. |
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| Author: | minimanic [ Fri Dec 23, 2016 9:51 am ] |
| Post subject: | Re: Vacuum advance |
I have had almost 40mpg out of my performance 1275 mini on the last run to Beechworth. If I push it gets alot less! No Vac on the dissy, but a fair bit of time into getting the tune spot on. My 998 moke is lucky to get 35mpg, but the thottle is usually a further open, even at cruise as the engine is fairly standard and works a bit harder. |
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| Author: | deluxe67 [ Fri Dec 23, 2016 11:20 am ] |
| Post subject: | Re: Vacuum advance |
I just got 30 mpg on a 350 km round trip. Thought I'd get more as I drove fairly sedately. The 110 km/h at 4500 rpm in parts of the Western Freeway wouldn't have helped I guess... |
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| Author: | simon k [ Sat Dec 24, 2016 8:50 am ] |
| Post subject: | Re: Vacuum advance |
even though the carbs have been reconditioned, I'd still swap the S carb body with a standard version. Everything that's been done to the S carb for reconditioning is bolt-on, other than a bit of a cleanup. I'm sure you could give the standard one a polish and swap the new parts to it... the risk of stuffing up the S carb is too much |
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| Author: | 1071 S [ Sat Dec 24, 2016 10:55 am ] |
| Post subject: | Re: Vacuum advance |
"....Everything that's been done to the S carb for reconditioning is bolt-on, other than a bit of a cleanup.".... Except if the bodies have been bushed or reamed for an oversize throttle plate spindles... But I would agree that replacing the right hand carb with a standard unit would be a better option than getting out the drill Cheers, Ian |
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| Author: | slide [ Sat Dec 24, 2016 10:58 am ] |
| Post subject: | Re: Vacuum advance |
Using timed / ported or full manifold vacuum advance all the time is a contentious issue. Many of the muscle car owners prefer full manifold advance at idle which they claim provides smoother idle, stronger take off and makes the engine run cooler at idle. This is with 4 barrel carbs of course. Not sure if the same reasoning applies to an SU. I've always used Webers and S dissys (non vac) on my Minis so can't say, though I always get the advance curve modified to suit the engine spec. http://www.hotrodders.com/forum/ported- ... 51264.html |
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| Author: | Minicooper4me [ Sat Dec 24, 2016 3:49 pm ] |
| Post subject: | Re: Vacuum advance |
1071 S wrote: "....Everything that's been done to the S carb for reconditioning is bolt-on, other than a bit of a cleanup.".... Except if the bodies have been bushed or reamed for an oversize throttle plate spindles... But I would agree that replacing the right hand carb with a standard unit would be a better option than getting out the drill Cheers, Ian You're got me thinking now. Maybe not so bad after all. Don't want to touch anything until I complete the economy run on Christmas Day. Plan to do a near full tank to get proper numbers to work with. But will definitely sus out changing one of the su bodies for one with a vac nipple. Thanks for your advise all you guys. Much appreciated. |
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