yoeddynz Posted November 26, 2011 Share Posted November 26, 2011 OK- anyone else here have a wideband gauge running on a car with carbs? I'm just curious to see what readings other people are getting at idle. My SU seems quite rich- at idle its hovering about 11.5 to 12. The exhaust is not overly rich smelling (for a rotary burning 2 stroke mix..) and if I do the old lifting pin thingee the revs go up slightly and then drop back. Plugs are dark- not sooty and not wet or oily. Most driving has been around town which always tends to foul plugs up a bit on rotaries a touch. Tonight while Hannah was in the supermarket I decided to weaken the mixture just a tad. 3/4 turns out. Idle now sat at 13 but straight away I noticed that out of gentle corners it would bog a touch and the gauge would soar round to 16-18 (flashing red on the outer ring of Leds!! ohhh) Drove the car up to my bros about 2kms away and checked the plugs. Now the bent over electrode (don't know what that bit is called..) was light grey/almost white! Hmmm- dodgy. I have wound the mixture screw back in as I definitely don't want it detonating on boost. So my question is... do most carbs run slightly rich at idle to avoid bogging down ? Or maybe the fact I am burning 2 stroke oil premix (100:1) is fooling the wideband gauge a bit? What else could cause it to seem rich at idle but then ok further in the rev range. It pulls well as it is but when coast down hill it just seems odd to see the gauge reading rich when it should be lean off throttle. Maybe I sound just a touch anal eh but I do love tinkering and I really like to get engines running as efficiently as possible while running carbs. Plus I like to be able to drive along with the windows down and not smell a rich running engine. One day when money allows I may fit injection to this engine but by then we'll probably have a little austin 1300 or something Anyway- i love this little setup for its simplicity and looks well retro too. Quote Link to comment Share on other sites More sharing options...
tortron Posted November 26, 2011 Share Posted November 26, 2011 you could go for a needle with less taper at the end (letting less fuel through at idle) Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted November 27, 2011 Author Share Posted November 27, 2011 I was thinking about that. I wonder how much needles cost and what range of sizes there are? Who are the best people in NZ to speak to about SU carbs and parts? Quote Link to comment Share on other sites More sharing options...
tortron Posted November 27, 2011 Share Posted November 27, 2011 as far as range goes there is everything you could imagine (even more if you have a good eye and some sand paper) http://www.teglerizer.com/suneedledb/index.html have a play on here Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted November 27, 2011 Author Share Posted November 27, 2011 Wow- yep that looks like an idea. Hopefully the code stamped on the needle is visible without having to remove it but if not no real hassle. I just remember older SUs being a bit fiddly to re-centre the needle? Cheers for link. Quote Link to comment Share on other sites More sharing options...
tortron Posted November 27, 2011 Share Posted November 27, 2011 some are self centering, even if they arnt, it will only take 5 mins to move it till its fine Quote Link to comment Share on other sites More sharing options...
Roman Posted November 27, 2011 Share Posted November 27, 2011 Slightly off topic, but why do people remove the factory oiling system in rotary engines in favour of having to use 2 stroke oil in the gas tank? (Not being facetious, I literally have no idea) Quote Link to comment Share on other sites More sharing options...
Rookie Posted November 27, 2011 Share Posted November 27, 2011 Mostly because the factory OMP puts sump oil into the engine and at the end of oil changes you are putting well used oil in which doesn't lubricate the seals as well. Also by running premix you are burning oil that is designed to be burnt and then you can run synthetic oil in the sump. Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted November 27, 2011 Author Share Posted November 27, 2011 ^What he said. Burning dirty sump oil is no good plus because its not designed to burn it leaves alot of carbon deposits which given enough time can break away and starting scoring the housings. Plus I have had the OMP (oil metering pump) fail on our first series 3 rx7 and we didn't realise until after a few hundred miles the engine failed due to excessively worn tips. With premix you always know the engine has protection. Adding 2 stroke is an extra bit of pissing about when filling up but I guess Mazda would never have sold rotaries if customers had to premix. Quote Link to comment Share on other sites More sharing options...
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