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Post by Zed on Apr 8, 2018 17:38:50 GMT
You can imagine how many circles I went in mapping the EFI with ignition and fuel variables for every rpm / throttle position. In the end I found a good guy who knew what he was doing (found him to solve a sensor problem, then he did the tune after) and it didn't take him long watching the AFR while I drove. WOT is the easy bit, lean cruise is a PITA. I imagine you can at least see which throttle positions give you low load vacuum for advance? I'm thinking of getting a(nother) guage to tee off my vacuum advance. Not knowing where it's doing it's thing isn't helping to picture what's going on. The tiny band of idle driving was a surprise so...
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Post by Zed on Apr 8, 2018 18:50:27 GMT
Meanwhile... certain ranges of jets go with certain venturis. I knew that, but only in a vague "bigger vents = bigger mains" way. I'm using 32 vents and my 145 jets should be too rich, but running at constant speed they're too lean. Only when I'm at WOT they are too rich. Also I should be finding 55 idles about right, but they're far too rich.
So, maybe there's two problems there that aren't jetting.
First perhaps extra fuel is getting into the carb throat/idle circuit. I've had the carbs to pieces checking for "Dell drip" and possible leakage past the unused choke gubbins. Also added some fibre washers to the progression hole cap scews.
Then I had to rebalance them but the one with the servo attached won't behave. Last time I balanced them I had a stock type-4 balance pipe with spur to servo fitted. It messed with the balancing, I thought due to the balance pipe aspect so I disconnected it completely, balanced the carbs and then reattached but just to one pot.
Ahhh, so I'm now thinking I have a servo vacuum leak with is leaning the overall afr readings hence needing larger than expected main jets. What may be happening is 3 cylinders running rich and one running lean. Makes sense but I've doing this all bleedin day and opted for dinner and and glass of red in favour of crawling under the van with a listening tube. It's all new servo and pipe so it must be the connection to the servo where the fitting is just bunged in a hole in the servo body by design. IIRC I had a bit of trouble aiming the stiff fat pipe at the servo in a way not to stress it too much so I'll look there first.
It seems to me that at WOT there will minimum manifold vacuum, so less air leaking in and it goes as rich as it should with the technically oversize jets I have fitted.
I hope I do find a leak or it's be back to the drawing board. I hate it when my theories are wrong. If I do find one I'll reconnect the balance pipe to the second manifold and see if it's possible to balance dual barrel carbs with a balance pipe after all.
All good fun...
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Eoin
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Posts: 101
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Post by Eoin on Apr 8, 2018 18:51:23 GMT
I had the vacuum feed disconnected and tuned on TPS only. Seemed to make more sense to me than using vacuum. The tuner who did the final set up agreed, although lots of people do use vacuum as a signal to indicate throttle position. Ignition advance is on a table with revs / TPS. If you went for mapable ignition, you could use vacuum to avoid needing another sensor.
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Eoin
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Posts: 101
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Post by Eoin on Apr 8, 2018 19:01:43 GMT
The first issue you have is that you have no control over the ignition 'map', so you can't retune the ignition to match the modified fuelling. So if you go lean and it burns slower (yes, I know you disagree), then without extra advance, you may be getting incomplete burn and so a rich AFR reading.
The second issue is connected. You have a large bore, so the flame has a long way to travel. Again, this will tend to mean incomplete combustion, especially as you lean the mixture and slow down the flame speed.
Incomplete combustion may be messing with your AFR readings.
P.S. A glass of something always helps the though process, wine is the right choice.
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Post by Zed on Apr 8, 2018 19:06:27 GMT
I had the vacuum feed disconnected and tuned on TPS only. Seemed to make more sense to me than using vacuum. The tuner who did the final set up agreed, although lots of people do use vacuum as a signal to indicate throttle position. Ignition advance is on a table with revs / TPS. If you went for mapable ignition, you could use vacuum to avoid needing another sensor. Interesting, he's decided from where you would have vacuum based on throttle postion. in relation to TP, how has he mapped the "vacuum" advance? I mean numbers, e.g. all out at 1/2 throttle.
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Post by Zed on Apr 8, 2018 19:10:52 GMT
The first issue you have is that you have no control over the ignition 'map', so you can't retune the ignition to match the modified fuelling. So if you go lean and it burns slower (yes, I know you disagree), then without extra advance, you may be getting incomplete burn and so a rich AFR reading. The second issue is connected. You have a large bore, so the flame has a long way to travel. Again, this will tend to mean incomplete combustion, especially as you lean the mixture and slow down the flame speed. Incomplete combustion may be messing with your AFR readings. P.S. A glass of something always helps the though process, wine is the right choice. I think we eere both right depending on which side of stoich. Rich of stoich, richer needs more advance. Lean of stoich, leaner needs more advance. 👍
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Eoin
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Post by Eoin on Apr 8, 2018 19:12:46 GMT
Vacuum and TPS are the same thing, vacuum is the result of throttle position (low TPS = low MAP).
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Post by Zed on Apr 8, 2018 19:23:47 GMT
Vacuum and TPS are the same thing, vacuum is the result of throttle position (low TPS = low MAP). Yes, but you know the numbers, you have them on a table where I'm in the dark as I can't monitor the vacuum or the vac advance. I do have a fair idea where my foot is but that's it. If I had a meaningful idea of how the vacuum signal relates to throttle position it would help my imaginings for now. Pretty sure I'm going to rig up a vac guage, see what amount of vacuum operates the advance mechanism, then by watching the gauge, I could even mark it's dial in degrees, I could see what's going on. For instance, I cruise at 70mph on the flat at about 1/2 pedal and have no idea if I have any additional advance operating.
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Post by Zed on Apr 8, 2018 19:31:13 GMT
Vacuum and TPS are the same thing, vacuum is the result of throttle position (low TPS = low MAP). Could you post your maps? This being the tuning thread, it would be great to see some real life pro tweaked customer proved ignition and fueling maps.
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Post by Zed on Apr 8, 2018 19:39:56 GMT
Where's boris when you need him. He loves this stuff. He hasn't been here for 9 months but maybe he'll get an email alert to the tag.
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Eoin
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Post by Eoin on Apr 8, 2018 20:16:14 GMT
I'll have to extract the latest maps. Ignition is correct but fuel may out. The tuner just set it up how it worked well with closed loop switched off, so the AFR table is not the reference, rather what the tuner thought was right. TBH I'd had enough at that point and was happy ot was running right.
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Post by Zed on Apr 8, 2018 20:28:23 GMT
I'll have to extract the latest maps. Ignition is correct but fuel may out. The tuner just set it up how it worked well with closed loop switched off, so the AFR table is not the reference, rather what the tuner thought was right. TBH I'd had enough at that point and was happy ot was running right. My main interest (at this point) is the TP/timing relationship.
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Post by Zed on Apr 8, 2018 21:41:36 GMT
Minimum Timing for Best Torque.
As timing is increased at fixed revs the torque increases then plateaus before falling. Pick the start of the max torque plateau = min timing max torque. That's dependent also on afr, in turn chosen for coolest egt no doubt in ever decreasing circles for many samples of revs and load.
I'm glad I don't have mapped ignition and fuel injection, Carbs and a distribitor are bad enough.
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Eoin
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Post by Eoin on Apr 9, 2018 7:58:51 GMT
Minimum Timing for Best Torque. As timing is increased at fixed revs the torque increases then plateaus before falling. Pick the start of the max torque plateau = min timing max torque. That's dependent also on afr, in turn chosen for coolest egt no doubt in ever decreasing circles for many samples of revs and load. I'm glad I don't have mapped ignition and fuel injection, Carbs and a distribitor are bad enough. Shaun who tuned mine was a bit more pragmatic and didn't try to make it 'perfect'. Lot's of people on STF keep working on advance and leaning the cruise to get optimum economy, but it's a huge amount of work and after a while you get bored of driving round with a laptop / looking at data logs. Also, to get the on / off throttle transitions right you need someone watching the AFR as you make the transition and adjusting and then going again. Shaun was cheap enough, £70 to do the map riding along, Sleaford.
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Post by Zed on Apr 9, 2018 8:28:07 GMT
Shaun sounds like a good guy. I'd do similar if I went down that road but I wouldn't be able to stop myself twiddling with it after. Every time I've used a rolling road I've changed things as soon as I got away. Just round the corner last time! Right, it's a glorious day in sunny Lancs, I'm off to hunt for a servo leak.
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