Ewald Posted August 6, 2016 Report Share Posted August 6, 2016 Hello I am new to the forum having recently bought as TR3B. Since I got the car, I suspected the engine was running on a rather rich mixture as the car would start from cold without choke. So when I got a chance I pulled the plugs and found them to be black and soothy. I did not have time to do a full tune of the carbs, so I just gave the adjusting nuts both about half a turn to make the mixture leaner. Since then I have noticed two differences: 1. I need the choke for the first couple of minutes of driving (even though ambient temperatures here are 25-30 C here right now) and the engine is prone to stalling in the first 10 minutes of driving. 2. Engine temperature during driving has gone up significantly. Before it used to be at 185F, unless in stationary traffic. Now during driving it goes up to the next mark on the dial (half way between 185 and 230F). This causes the electric fan to kick in and I am assuming that then keeps it stable. I am rather surprised by the large impact on the engine temp the (small) adjustment in mixture has made. I will spend some more time tuning the carbs better today, however I was surprised by the large effect. Anybody have any experience, or thoughts to share? Thanks Ewald Quote Link to post Share on other sites
peejay4A Posted August 6, 2016 Report Share Posted August 6, 2016 Half a turn is quite a large adjustment. A weak mixture can lead to high engine temperatures. Quote Link to post Share on other sites
Geko Posted August 6, 2016 Report Share Posted August 6, 2016 yes it has an impact on engine temperature. You may also play with the advance knurled knob by a few notches to see what happens... Quote Link to post Share on other sites
RogerH Posted August 6, 2016 Report Share Posted August 6, 2016 Hi Ewald, welcome to the forum, Remove the plugs and check the colour. However on tickover they may well become black. Rev engine at 2000 rpm for 30 seconds then kill the ignition. Then check the plugs. Retarded ignition will increase engine temp. Roger Quote Link to post Share on other sites
Peter Cobbold Posted August 6, 2016 Report Share Posted August 6, 2016 (edited) Hi Ewald, welcome to the forum. Going from a rich mixture to a lean mixture makes the flame spread slower. Roughly speaking going from AFR 13 to 16 needs about 5 crank degrees of retard. ( slide 67 https://supertrarged.wordpress.com/2016/07/21/iwe-2016-technical-seminar/ https://supertrarged.files.wordpress.com/2016/07/combustion-talk-iwe-2016-v2-ppt.ppt Running an engine with 5 crank degrees of retard will only kill about 1% of torque from maximum ( slide 60 ) That means only 1% more heat rejected to water jacket and exhaust gas. That's not going to make any detectable difference on the temp gauge. If we take the temp gauge readings at face value, I suggest the engine is a long way away from correct tune. First step: check the spark timing curve as it may be well off delivering max torque. Correct curves in slide 104. My guess is your sparks are set badly retarded, and leaning he mixture has made combustion even slower, sufficient to heat up the water jacket. And measure the mixture while driving with a wideband UEGO device. Peter Edited August 7, 2016 by Peter Cobbold Quote Link to post Share on other sites
Lebro Posted August 6, 2016 Report Share Posted August 6, 2016 (edited) Half a turn is quite a large adjustment. A weak mixture can lead to high engine temperatures. I was also going to say ½ turn is quite a large change, I usually adjust 1 flat at a time. Try going back1 or 2 flats, & see what happens. Also, check you have oil in the dashpots - that will affect "stalling" or "gasping" when accelerating. Bob. Edited August 6, 2016 by Lebro Quote Link to post Share on other sites
boxofbits Posted August 6, 2016 Report Share Posted August 6, 2016 I would also add it might be worth setting the mixture back to its original setting, then driving the car again under similar circumstances to ensure that the temp rise is not coincidental, before coming to a conclusion. Kevin Quote Link to post Share on other sites
TonyB Posted August 7, 2016 Report Share Posted August 7, 2016 (edited) Peter, to what does "slide no..." refer to? Is it a diagram or figure in the link referred to? If so how do you find it? I've looked and tried but have had no success. Tony Post script Sorry, I looked again, I assume it referred to IWE2016. I can't get it to download. Edited August 7, 2016 by TonyB Quote Link to post Share on other sites
ChrisR-4A Posted August 7, 2016 Report Share Posted August 7, 2016 Hi Ewald, by half a turn do you mean 180 deg. If the carbs were strombergs which have six flats I would suggest no more than one flat at a time between checking results. Quote Link to post Share on other sites
Peter Cobbold Posted August 7, 2016 Report Share Posted August 7, 2016 (edited) Peter, to what does "slide no..." refer to? Is it a diagram or figure in the link referred to? If so how do you find it? I've looked and tried but have had no success. Tony Post script Sorry, I looked again, I assume it referred to IWE2016. I can't get it to download. Tony, My apologies, the link to the powerpoint should be this: https://supertrarged.files.wordpress.com/2016/07/combustion-talk-iwe-2016-v2-ppt.ppt Peter Edited August 7, 2016 by Peter Cobbold Quote Link to post Share on other sites
Ewald Posted August 8, 2016 Author Report Share Posted August 8, 2016 Gents, over the weekend I spend a bit more time setting up the carburetors properly. I indeed had made the mixture far too lean. I also filled up the dashpots. Combined that has made a massive impact! Car drives so much better now and temp has dropped back to normal levels! thanks for the many tips.Peter, thanks for the ppt. I will have a read of that next and have a look at timings... Many thanks everyone! Ewald Quote Link to post Share on other sites
TonyB Posted August 9, 2016 Report Share Posted August 9, 2016 Tony, My apologies, the link to the powerpoint should be this: https://supertrarged.files.wordpress.com/2016/07/combustion-talk-iwe-2016-v2-ppt.ppt Peter Thanks Peter. I thought I might ft a supercharger to my 3A one day...... just a pipe dream really though. Like most things it's more complicated than I thought. Tony Quote Link to post Share on other sites
RogerH Posted August 9, 2016 Report Share Posted August 9, 2016 Hi Tony, 'just a pipe dream' - well that's a start. Stick as blower on the pipe and a big SU on that and off you go. Rogre Quote Link to post Share on other sites
TonyB Posted August 10, 2016 Report Share Posted August 10, 2016 WANTED supercharger, must work and be cheap. 12volt vacuum cleaner considered if it blows as well as sucks. Also, pipe, fat and bendy with a smooth bore. Prefer one with low Reynolds number and good laminar flow. Tony Quote Link to post Share on other sites
Geko Posted August 10, 2016 Report Share Posted August 10, 2016 WANTED supercharger, must work and be cheap. 12volt vacuum cleaner considered if it blows as well as sucks. Also, pipe, fat and bendy with a smooth bore. Prefer one with low Reynolds number and good laminar flow. Tony check this post from Down Under http://www.tr-register.co.uk/forums/index.php?/topic/58349-should-i-be-tempted/?p=484725 Quote Link to post Share on other sites
Peter Cobbold Posted August 10, 2016 Report Share Posted August 10, 2016 WANTED supercharger, must work and be cheap. 12volt vacuum cleaner considered if it blows as well as sucks. Also, pipe, fat and bendy with a smooth bore. Prefer one with low Reynolds number and good laminar flow. Tony .....and high adiabatic effciency. Peter Quote Link to post Share on other sites
TonyB Posted August 10, 2016 Report Share Posted August 10, 2016 .....and high adiabatic effciency. Peter Of course Tony Quote Link to post Share on other sites
Peter Cobbold Posted August 11, 2016 Report Share Posted August 11, 2016 Of course Tony Tony, 'Reynolds number....laminar flow '. I've been struggling to analyse the role of a venturi in SU carbs. You dont happen to know if Bernoulli's equation requires laminar flow....what if the air is turbulent? Peter https://supertrarged.wordpress.com/2013/08/24/tr6se-16-no-venturi-effect-in-an-su/ https://supertrarged.files.wordpress.com/2015/05/the-operating-limits-of-an-su-carburettor12.pdf Quote Link to post Share on other sites
Ian Vincent Posted August 11, 2016 Report Share Posted August 11, 2016 Peter, If I recall my university thermodynamics there are two types of Bernoulli equation, one for compressible flow and one for non compressible flow. Because I was studying Civil Engineering, we focussed on the latter and I don't recall turbulence being an issue. It would make sense for turbulence to be an issue with compressible flow as the introduction of turbulence in aerodynamics has quite a marked effect on lift. Rgds Ian Quote Link to post Share on other sites
Peter Cobbold Posted August 11, 2016 Report Share Posted August 11, 2016 (edited) Peter, If I recall my university thermodynamics there are two types of Bernoulli equation, one for compressible flow and one for non compressible flow. Because I was studying Civil Engineering, we focussed on the latter and I don't recall turbulence being an issue. It would make sense for turbulence to be an issue with compressible flow as the introduction of turbulence in aerodynamics has quite a marked effect on lift. Rgds Ian Thanks Ian, I'm completely new to the subject, it never figured in biology. If there is a venturi-generated depression over the jet I think it will tend to suck the piston down onto the bridge !! So its a puzzle. It would be convenient if turbulence killed the effect. Yesterday we walked by Telford's Horshoe Falls at Llangollen. He built a venturi flowmeter about 3-4 feet diameter to measure the flow out of the Dee into the Llangollen canal. Civil Eng 1800-style. Just 60 years after Bernoulli published the theory. Peter Edited August 11, 2016 by Peter Cobbold Quote Link to post Share on other sites
Ian Vincent Posted August 11, 2016 Report Share Posted August 11, 2016 In the 1800s there were really only two types of engineering, Military or Civil. Rgds Ian Quote Link to post Share on other sites
TonyB Posted August 12, 2016 Report Share Posted August 12, 2016 Tony, 'Reynolds number....laminar flow '. I've been struggling to analyse the role of a venturi in SU carbs. You dont happen to know if Bernoulli's equation requires laminar flow....what if the air is turbulent? Peter https://supertrarged.wordpress.com/2013/08/24/tr6se-16-no-venturi-effect-in-an-su/ https://supertrarged.files.wordpress.com/2015/05/the-operating-limits-of-an-su-carburettor12.pdf Peter, you credit me with far more intelligence than I actually have. Either that or you are, in the nicest possible way of course, taking the mick. Sorry, I can't help with that one. Tony Quote Link to post Share on other sites
Peter Cobbold Posted August 13, 2016 Report Share Posted August 13, 2016 Peter, you credit me with far more intelligence than I actually have. Either that or you are, in the nicest possible way of course, taking the mick. Sorry, I can't help with that one. Tony Tony, Not taking the Mick. Thought you might be an engineer after you mentioned Reynolds number etc. Peter Quote Link to post Share on other sites
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