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It's taken several days (on and off obviously, not a 72 hour binge read!), but I've ready the thread from start to finish, and it's been a thoroughly enjoyable adventure! It's an awesome special, and is clearly greater than the sum of its parts  I'm glad to read that you're getting somewhere with both power and economy now you're set-up with the Megasquirt. I've built/tuned several Megasquirts over the years (all for petrol, I've not played with LPG) and while they can be frustrating at times the end result of getting the car running right is very rewarding. From the last post it sounds like you've sorted it, but if you haven't, then I suggest changing the acceleration enrichment to be triggered from the rate of TPS change (TPSdot) rather than MAPdot. It responds quicker and is easier to get tuned in. If you are generally seeing variations in MAP, due to airflow past the bell mouths, then it might be investigating Alpha-N mapping (TPS Vs RPM). The ITB mode essentially uses Speed-density (MAP vs RPM) for the light throttle/cruise parts of the map and Alpha-N for the large throttle openings and then cleverly blends it together to create a single VE table. So if you're getting large MAP variations, then that could be mucking up your feeling when crusing on the Speed-density portion of the map. When I had an Mx5 running bike ITBS I experimented with both modes. I felt the Alpha-N was ultimately easier to tune and gave me more consistent results. In theory the issue with Alpha-N relates to the large change in fuel needed over the very small change in TPS value when you're on small throttle openings, making it difficult to get smooth light throttle running. I didn't have any issues getting the small throttle openings smooth. This might have been helped by the fact that the throttle bodies I was using weren't overly large? I was also only using a stock cam. Obviously it was a very different set-up to your LPG arrangement though, but possibly some food for thought! Thank you goldnrust, all good points , in this instance with lpg i tend to use no accel enrichment at all ,especially when i found out that AE switches off ego feedback control , and my oscilating map signal was being seen by the ecu as accel ! this meant my ego control was switching on and off all the time . the itb mode seems to drive ok , however i still have that sudden increase in ve in the top 2 rows ...the utube vid on itb mentions this as a drawback , but does not show a ve map with itb ,to compare. my next plan is to keep running itb , but make the y scale have moe rows between 100 and 80 ,and make the lowest row equal to my lowest operating point ,which is around 35 .then persevere with mapping it . regards robert |
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goldnrust
West Midlands
Minimalist
Posts: 1,886
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Aug 27, 2019 11:15:40 GMT
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Good plan to change the weighting of the Y axis rows. This was partly how I was able to get my ITBs to run well on Alpha-N, though my problem was at the opposite end of the table.
My knowledge of LPG is very limited, but I'd be surprised if it wouldn't help to have a little acceleration enrichment? It should only need to trigger for a ration of a second, and only on more aggressive throttle movements. On a petrol engine it makes a huge difference in driveability.
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Aug 27, 2019 11:19:44 GMT
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i have another lpg car , a turbo 8 v 1.4 astra F , i have found i just don't really need accel , the lpg is so light it does not hold back like heavier petrol droplets . however once i get it all a bit closer i will try introducing some just to see ...this is a bit of a different engine , and it does have a 35 lb flywheel for 7.6 litres of 4 valve goodness , so it revs a bit like a bike .
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Aug 27, 2019 12:18:53 GMT
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thanks Mark , i think that works out to the cost equivalent petrol as 24.2 mpg  Which is way better than I get with 4 cylinders less! |
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Aug 27, 2019 13:35:22 GMT
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thanks Mark , i think that works out to the cost equivalent petrol as 24.2 mpg Which is way better than I get with 4 cylinders less! |
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jamesd1972
Club Retro Rides Member
Posts: 2,916 
Club RR Member Number: 40
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Aug 27, 2019 15:14:02 GMT
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Or 8 cylinders less !
James
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Aug 27, 2019 15:51:38 GMT
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Or 8 cylinders less ! James |
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Well done Robert on getting much better MPG.
I enjoy reading about the "innards" of ECU tuning but my practical knowledge came to a halt years ago with distributors and Lumenition!
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thanks phil |
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WELL , i had a tiny window of opportunity to get the monster onto the dyno last friday . i have not been able to set the fuelling very well at higher rpm , basically because its so bloody fast at accelerating ...being under a ton and over 350 lbs ft of trq , and big tall wobbly tyres ,means i keep ploughing into corners way too fast ...or going well over my winnebago 7.50x 16 tyres speed limits , i don't mind going over it on the dyno cos i can always run away. so strapped her down ,and did a few minutes working on the low down tickover and below fueling , so it has a lot more low down trq for trickling in traffic , made a little progress ,still too rich , but its hard to hold steady state over 300 lbs ft at below 1500 rpm ...more work to do on that area it kept falling in a big rich hole at higher throttle opening . then onto a couple of full throttle runs , with the ecu set on auto tune , so it would set the fuelling for me ,after a fashion . now judging by these piccys ... 30 mph light throttle..  higher rpm full chat max trq..  i may have just found the trq limit of my rollers with little narrow tyres and no loading ! i am not sure if it shows very well ,but there was a churn load of blue smoke coming off the tyres , also you can see the grated tyre rubber being thrown across the cave as my gritted rollers hone down the treads a touch . however i did manage to get some readings.. bhp is now up to 354..  that's a graph of my best venturi run with the 2 spinning injection runs , and my theoretical max with grip ...i reckon at around 380 bhp. then torque at 419 lbs/ft ..  here i reckon on around 435 lbs/ft max theoretical ..however my 419 is still 58 lbs/ft up on the old fueling system...noice inj run number 2 had more ignition advance , 1 degree more made a fair bit of difference . now i am aiming for around 13.5:1 air fuel ratio , here you can see the fuelling logs for both runs on both engines ... engine 1 , the 3.6 litres .. run 1  run 2  engine 2, the 4.0 litre.. run 1  run 2  you can see how the autotune has modded the fuelling , sometimes over shooting and going too far the other way ,also i am well over 100% duty cycle with these injectors at this 15 psi fuel pressure ,which is a surprise ...and basically means they are wide open non stop ,hence the leanness in the places at the higher rpms . also these power runs where done on a low load so the tyres had a chance to grip ,so the ecu only had a few seconds to adjust the fuelling before it was run over ...so i am pretty impressed the ecu was able to take a car that wouldn't rev ,to one that would , in just a few pre run rev ups . also it revved to 6k with little vibration i think with better fueling and timing i should reach 400 bhp and 500 lbs/ft ....but maybe nor be able to grip it lol. .... for all i know its there already ...it does explain why a blip of throttle in 3rd at 40 lights up the tyres like a volume control. ok ok ,geekness over regards robert. |
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glenanderson
Club Retro Rides Member
Posts: 4,318
Club RR Member Number: 64
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Why is it I can only "like" that post once? It needs a whole row of thumbs-ups!  |
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My worst worry about dying is my wife selling my stuff for what I told her it cost...
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Sept 2, 2019 12:19:54 GMT
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Why is it I can only "like" that post once? It needs a whole row of thumbs-ups! You and me both. The fuelling maps are way over my head, but this... "i think with better fueling and timing i should reach 400 bhp and 500 lbs/ft"
I understand! |
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Sept 2, 2019 12:21:19 GMT
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Why is it I can only "like" that post once? It needs a whole row of thumbs-ups! You and me both. The fuelling maps are way over my head, but this... "i think with better fueling and timing i should reach 400 bhp and 500 lbs/ft"
I understand! There you go guys.....👍👍👍👍👍👍👍👍👍 Of course, these work too....✅✅✅✅✅ |
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Sept 2, 2019 15:20:19 GMT
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Best keep them skinny tyres or you will be making new gearbox to engine fittings!
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Sept 2, 2019 16:24:21 GMT
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Best keep them skinny tyres or you will be making new gearbox to engine fittings! Your not kidding , i read the transit box is rated by ford to 220 lbs/ft..the current 420 + may be twisting it a bit , although its running in 4th on the dyno so not going through any gears ,and any lower gears just wheespin .....at least so far.....so good ...  |
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Last Edit: Sept 2, 2019 16:25:08 GMT by ivanhoew
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Sept 2, 2019 20:22:14 GMT
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The Transit runs reduced torque in each of the lower gears 1 to 3 as well, in reality though the capicty is based on fatigue life for a commercial vehicle used and abused over 150,000 miles the ultimate capacity is far higher it just won't last as long, look up B10 life if you are interested.
If you do manage to break it the mt82 6 speed is much stronger and more or less a straight swap.
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oh thats interestign kevin , i will look it up , i could do with a taller gear .
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Sept 4, 2019 17:11:12 GMT
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A quick Google of the transit forum suggests that the 6th gear is about the same as 5th on the old box unless you build yourself a hybrid box in which case it looks like 0.65 might be achievable.
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Sept 4, 2019 19:24:39 GMT
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yes i saw that DR , it looks like there is a new improved version the d4 ? with 4th as the 1:1 ,and then 5th and 6th as overdrives with a 0.6 something top gear , that would be nice , however they were only made 2018 and on i think .
do you mean a hybrid of what i have now or a hybrid 6 speed ?
RR
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Sept 4, 2019 20:32:12 GMT
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yes i saw that DR , it looks like there is a new improved version the d4 ? with 4th as the 1:1 ,and then 5th and 6th as overdrives with a 0.6 something top gear , that would be nice , however they were only made 2018 and on i think . do you mean a hybrid of what i have now or a hybrid 6 speed ? RR You could build a hybrid transit mt75 by using (from memory) the diesel ford Scorpio 5th gear set up which gives a lower ratio than standard, or possibly the same trick mixing and matching with the new box to get more overdrive in 5th and 6th. I think your set up will probably not have a problem pulling that gearing Alternatively do you have the length to add a self contained overdrive unit after the mt75? |
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