Megasquirt - The Advanced Thread -For ADVANCED Discussions

[FridgeFreezer]

Difficult to tell from that picture, you have a MAP spike, an RPM dip and an AFR spike all at the same time. I'm thinking it's a misfire perhaps on one plug.

Although Nige is right about the ideal mixture, I tend to leave mine to hit ~14.7:1 at cruise and haven't had a problem. 14.7 is actually richer than needed on most engines, it's to make cats work properly. Many cars (later Rover V8's included) run leaner at cruise although the P38's ran very lean and also suffered the liner slip problem more the thing is unless you have a wideband lambda sensor you can only really get the MS to trim for 14.7:1 (454mv on the lambda sensor) as you drive - of course with MLVV you can tune for any mixture.

[evo828]

Thanks. How can I identify the one which misfires? From plugs?

[Hybrid_From_Hell]

Tricky

My way is to change the entire bank at a time and then narrow from there :

ie change 2 4 6 & 8 - If no difference then replace originals

and then change 1 3 5 & 7

Which ever bank shows up as the prob then change 2 x plus

ie if is even bank ( 2 4 6 8) then change 2 & 4

if no difference the 6 8

Which ever ones then change them, ie if 2 and 4 change no 2 then if not sorted its number 4

Worked for me a few times in the past, cheaper than a full plug change as this tracks down the viilan

Misfires kills plugs in V8 BTW ..............should that be

Nige

[landybehr]

Hi there,

I know, I´m cumbersome. Hope my account will not be closed just that the cracking block symptom and everything associated is important (possibly costly) for our engines I feel and therefore I try to verify all time what´s true there: B)

1) Have a look there:

http://www.msefi.com/viewtopic.php?f=31&am...st+burn#p190851

second post from Eric Fahlgren and 4th or 5th post from him again.

Short: highest combustion temperature shall be at 14.1 (lower at lean).

If it is wrong what Eric and Lance wrote in that thread, I´d need to know. Up to now I´ve lost my fear against lean mixtures, which in turn allowed me to make the car more fuel efficient, and that´s important for me - running costs need to be kept low if possible.

2) do emission regulations really allow a mid-/end 1990ies car (like P38) to run at anything other than stoich at cruise ??

Des Hammill writes in his book that the Bosch-EMS (Motronic thing for Thor) keeps the engine in 14.7 as much as possible (not possible at WOT obviously). If this is true it´s interesting because I´ve been told the Thor-V8 is the V8 in the P38 that does not suffer from cracking.

To complicate things - that might have sth. to do with the fact that Rover kept an eye an the wall thickness behind the liners in the mid 1990ies -onwards (into which´s category the Thor does fall). So can one conclude that Rover´s engineers saw the reason in casting imperfections rather than mixture affairs ?? If it were as simple as changing a fuel map, I think, Rover would have done so instead of increasing tooling and production costs ??

[evo828]

was playing with the timing today - seems that advancing timing helped to cure it - actually now the cars runs much smoother and accelerates better. The popping went away - hope it stays like this

timing-before

timing after

[landybehr]

EDIT (of my last post): ad 2), the stoich topic:

I think that the 4.6 suffered more than the 4.0, resp. Rover took the better engine blocks for the 4.6 was because the 4.6 has 15% more displacement to breathe in same amount of addition air (compared to 4.0) with more fuel even at the same AFR. Therefore there will be more heat generated after ignition takes place. That includes that an increased amount of heat has to travel through the cylinder wall.

There is something else for lean mixtures at cruising speeds:

http://www.msefi.com/viewtopic.php?f=31&t=34061

(because, BTW, re-Chipping the 14CUx ECU claims the following: http://www.v8engines.com/engine-8.htm#ecu which is 10-15% increase in power and efficiency. My theory, that the re-chipped ECU´s achieve that by a) richening WOT a little and B) leaning cruise a little, so doing something very opposite to what I read before is still subject to falsification. Please believe me when I say that I do not want to sound smarter than others, only want to push the verification process.)

[Hybrid_From_Hell]

Not just dispalcment - qulaity

read here : http://forums.lr4x4.com/index.php?showtopi...;hl=yellow+blue

Run the wrong block too hot / weak / generate too much heat .......and fun will ensue

Nige

[Hybrid_From_Hell]

PS Spark map is werid

Why have you got reduced advance at 20/25 KPA ??

Your advance is too small, your WOT is far too much for a 3.9

max advance on a 3.9 is around 34/35 degrees .........and no more at WOT / 100 KPA c

Too much spark can do severe damage to piston crowns......... irrespective of VE table so

suggest you reduce. There are a number of VE / Spark configs for 3.9s on the master MS thread suggest

you have a study of them, if you have too much spark its easy without knock kit to NOT hear the damage being done

until too late = POP

Reduice max advance at WOT and increase as KPA drops unless your cam is advanced from std

Nige

[evo828]

Thanks Nige. Will decrease the 90kpa 100kpa - and adjust 20and 25 kpa (although I rarely hit them). however the 60-80 kpa 2000rpm - seems to work well at this moment. Will have to drive a bit more (only did on Sunday).

My previous map was done based on the popular-default map posted by Fridge somewher in these threads - and actually it was working fine with the old spark plugs and cooler weather.

[evo828]

When you are running narrow band with EGO correction ON - based on Fridge's popular defaults it is correctnig to 0.510V all over 1300rpm and above 55 degC (and below 90kpa) - isn't it to soon if the temp is 55 degC ?

Also this means that you are correcting towards a leaner mix than 14.7 (14.7 is 0.454 - so 0.510 is leaner I assume)?

[FridgeFreezer]

When you are running narrow band with EGO correction ON - based on Fridge's popular defaults it is correctnig to 0.510V all over 1300rpm and above 55 degC (and below 90kpa) - isn't it to soon if the temp is 55 degC ?

Also this means that you are correcting towards a leaner mix than 14.7 (14.7 is 0.454 - so 0.510 is leaner I assume)?

0.510 is richer, but only a tiny amount in reality. Although it's better to wait till the engine gets up to "full" temp before turning O2 correction on, again it doesn't matter greatly and when I did that map I was running with no stat so the truck actually couldn't get much above 60deg so I just turned the temperature down so I could actually do some useful logging

[Hybrid_From_Hell]

Plus you can filter via MLV any values you don't wnat for the tuning...

ie 78 / xx degrees and above only

Nige

[evo828]

Thanks. I have not problem with analysing and filtering

I am just preparing to get rid of wideband as I think my VE is more or less fine and want to put a narrow band and stop driving with laptop all the time. LC-1 is a little bit sensitive - so OK for tuning - but not for daily driving. I have a universal narrow band sensor now - so getting ready to plug it in

btw - do you know the thread size of the original titanium o2 sensor - I need to buy a plug for these as I want to take them out. is it 12x1?

[landybehr]

Hi, M12 is probably correct.

What is the benefit of downgrading to a NB sensor ?

AFAICS it will only tell you whether the AFR is higher or lower than 14.7 - sth. you needn´t know because your VE are fine AND tuned for appropriate AFRs (i.e. other than 14.7 all over).

To utilize the NB sensor (closed loop) you would have to re-tune the VE table with a different AFR table again.

You could just ignore the LC-1 (and leave it where it is) or remove the LC-1 (and put a plug into the hole) and simply run open-loop.

Just like the 3.9 from Rover without Cat did.

What has your LC-1 done to you ??? (mine seems to do what it should. But I have it in use for no more than 1000miles till today)

[FridgeFreezer]

The benefit of swapping to a NB sensor is once you've tuned the car with the wideband you don't need to keep an expensive sensor in there and can swap in a much cheaper one. Sensors have a limited life, off-roading can kill them easily (one hit from a stone or branch can shatter the element) so better to kill a cheap sensor than an expensive one.

The narrowband cannot be used directly with a target AFR table, but once you have tuned your VE table with wideband the narrowband is fine for minor closed-loop adjustments to the mixture under many conditions - mostly cruising, which is how 99% of cars these days run. They have a preset fuel map, and then under suitable conditions the O2 sensor is used to trim the mixture for best efficiency. At high load or rpm, the sensor is ignored (open loop) and the fuel map used directly.

You can still tune your car effectively with a narrowband using datalogs and MLVV as has been documented before.

To use a NB sensor you would not have to re-tune your VE table as that is the correct table for your engine, not for a sensor. What you DO need to do is change the O2 settings in MegaTune to Narrowband type sensor and associated values.

[Hybrid_From_Hell]

I have now done tunning with NB and a LC1 on another V8

With MLV for 99% of what we do NB + MLV will give you a rersult with some work that in some ways beats WB, and

at a fraction of the costs. MLV + NB offers incrediable tuning potential, so good that many people belive it can't

be true, and to get anything decent = the need for a WB - IMVHO not at all true

To be honest now I wouldn't spend money on a WB, its not needed, and the costs and the shorter life expectancy

of a WB such as LC1 just isn't justifyable, I think the technology of MLV and the algorithims within have suprased

the huge older differentials between WB and NB. I know BBC did similar comparisons on his V8 and he found the WB was not

the "Hallode god" so many thought it was.

Its more a question of using NB MLV and then some effort to interpret and human effort to understand whats going on, I leave

my NB in for closed loop and it gets a good dunkin water wise, and LC1 would go ping and in the bin with a big wallet shock

and hence why its still sitting on the bench

More expensive a la LC1 vs NB doesn;t actually always mean "Better" MLV is a superb bit of kit with a NB, with some

thought work and intervention you'll be stunned what you can achive, actually without Thought work and intervention

even with a WB you'll not get what is needed

Nige

[evo828]

For me - LC-1 is good for tuning the map. For daily driving - in case you want to use ego correction - a narrow band sensor is the way to go because LC-1 likes to play crazy from time to time. And if you do not see its values (do not have laptop on) - you will not realize the weird thing with the ego correction trying to beat the incorrect readings.

Atlhough it happened to me only twice during last 3 years - it is enough not to leave it in the car all the time. Mine was reading constant 14.6-14.8 during the failure - no matter what actually was in the exhaust. Just a simple connecting of the LMprogrammer (not reprogramming - only connecting) - cured it - but strange behaviour anyway.

I bought a brand new universal narow band sensor bosch ls07 for 55EUR - will see how the car will ike it?

[Hybrid_From_Hell]

Two things to be also aware of with WB units generally

They have a limited laifespan

This lifespan can be brought to an abrut end if you have a WB and go off road and dunk hot 4x4 in cold deep water - they go "Ping"

Just in case anyone reading this wasn't aware.

they are also VERY expensive as well, a narrow band will survive much long and better even in deep water, and are cheap

GTM 7002 (unipart) around £33 for a new heated Lamda sensor

Nige

[FridgeFreezer]

Also worth reiterating that all types of Lambda sensor will die if you use silicone sealant ANYWHERE on your engine - you need to buy sensor-safe sealant (most proper stuff you buy from auto factors should be safe these days) or stuff such as Loctite 598. This applies to any application on your car where the fumes from the sealant could get into the engine - snorkels, air filter, coolant system, engine gaskets, ANYWHERE. Obviously with cheap NB sensors it's less of an issue if you kill one but WB ones it's an expensive mistake.

Although universal NB sensors are ~£30 from the auto factors I tend to buy them for £5 a time from the scrapyard, just look for a 3 or 4 wire sensor (most are these days), an adjustable spanner and a pair of snips and it's out, especially if the car is up high and you can stick your head under the front.

[landybehr]

Hi,

that´s interesting news. Think my LC-1 hasn´t had a hard life. Even though it probably will only need replacement of the sensor (it´s the controller that represents most of the costs) = http://www.diyautotune.com/catalog/product...products_id=125 (Bosch LSU4.2) for 79$ which equals to 45Pounds today, that´s not the point - the WB sensor IS more expensive.

My thought was - the VE table represents the the %age of air in the cylinder at the certain load/RPM condition so I can follow that it is not EGO sensor dependend. (I start to talk about stuff I really don´t fully understand).

OTOH I see that the VE table seems to be influenced by what I did with the AFR table. The WB sensor allows me to have rather lean cruise AFRs of, say, 15.5:1 and I see that MLV will reduce the corresponding VE bin compared to the VE-value that would have been there with 14.7AFR in the AFR-table.

If I turned to the NB sensor (and you gave good arguments for doing so!) - how would MS deal with the bin just described ? The NB sond will notice just a "LEAN" (not knowing by how much and whether it´s been desired or not) and now:

Do I get myself corrected by thinking that EGO-correction will NOT do anything because the AFR table suggests! a "lean" (i.e. 15.5:1) condition. So it doesn´t matter how far off from 14.7:1 the current VE bin is ?? MS is happy with NB saying "lean" because 15.5 IS lean ? That´s why the once-with-WB-tuned-VE-table can stay ?!!

But after all - isn´t the NB sensor ONLY good for closed-loop control if you are aiming at 14.7:1 ??

Which is ok for all the modern cars because they are told to run at that AFR due to the cats working best then. If current regulations are so strict that even X-tau corrections (MS2) or EAE-corrections (MS2x) or sth alike is necessary to not exceed emissions, I cannot believe (but cannot prove/disprove) that propper changes in mixtures (away from 14.7) are allowed (unless at WOT). At WOT Ego correction should be disabled for any sensor, ok.

AFAICS a lot of modern, new cars run WB sensors, P38 included (?) but that shall be no argument; didn´t mention to argue, rather because it popped into my mind

I get that you can tune with MLV because MLV can calculate/interpolate. But how about the closed loop running with a well-made-once-with-WB-sond-tuned-VE-table ??

[evo828]

Any idea what needs to be adjusted when the cars tends to stall after first start after being parked over-night or longer? My after-start enrichmnet is cca 40% - but somehow doesnot help - after re-start it still has some 1 or 2 drops in RPM - but then it goes well. Also any following re-start are without problems.

Please see the pics from the log:

1st start

http://i548.photobucket.com/albums/ii352/s...8/v8/start1.jpg

re-start after 1st start

http://i548.photobucket.com/albums/ii352/s...8/v8/start2.jpg

[landybehr]

Hi,

I experience similar behaviour. I don´t know if my thoughts will be of any help for you - sometimes thoughts I rate high are rather dumb. Anyway, I´ll tell you and you decide on your own.

I am quite certain that the engines stalls in your and my case due to not enough fuel in a cold start condition. One solution is to increase WUE to keep it alive after cranking. But ... I experience (have posted on msefi and comments were like that this is not an exceptional observation) that it matters if the specific coolant temp is there when cranking OR when the engine was already running for a while and passing that temp during warming up. In the latter case the engine needs less of WUE because there IS already considerable heat from several ignitions before. Therefore I decided to tune the WUE table to those bins, that give me a proper AFR on the already-running-for-a-while engine. In other words, I start the really cold engine at, say, 0°C, and tune the WUE bins for those numbers that give a similar AFR (I aim at 14.2:1) at 10°,20°,30°,40°,...,82°C of coolant temp. If having done so the engine will certainly stall after cranking. Well, the cranking pulses are fine and the engine fires into life immediately. The Revs shoot up same time which I deduce to excess "cranking-fuel" (there are twice as many squirts than after cranking) which is burnt. This happens for the fraction of a second and then the Revs fall - and the engine stalls. So it´s time to increase ASE and ASE-taper time to compensate for the fuel that I was saving by tuning the WUE the way I mentioned before. If the engine stalls after the first trial and is fine on the second attempt then I think this speaks for too-low ASE again as a) on the second trial there have been some ignitions which have left some heat and counteract condensation=loss of injection fuel and B) you start with a "fresh" ASE number. To decide whether ASE or ASE-taper time needs being increased I start the engine and take off immediately. If it stalls then, ASE needs to be increased. If that is ok but there is hestitation or jerking within 5-20sec then ASE-taper time needs to be raised.

I am quite embarrassed by ASE of 50% at 10° and 140%WUE for the same temperature (numbers out of memory, but will be close), but I think if put into perspective of the low ReqFuel the numbers sound higher than they are. My ReqFuel is 12.0 (and I think you, evo, are not much higher).

[Hybrid_From_Hell]

I have spent considerable time effort and have had / still have a bit the same problem.

When I get a mo I'll answer here long and hard, I think maybe with 3 of us (and others here) on it we can crack it,

the starting and cranking I have read somewhere takes 2/3rds of the ECU powers, the final 1/3rd runs it !

Its complex and minor cghanges can have dramatic effects

When I get a mo I'll post thoughts and questions on this

Nige

[FridgeFreezer]

Things to consider:

- Cranking pulsewidths, esp. on larger capcaity engines, can be quite long. I'm sure I've had to increase mine at least once.

- After-start enrichment (ASE) which is applied for the first ~250 engine cycles after cranking may also help bring it to life rather than just increasing the warmup value.

- There is also a "first start" enrichment that can be applied although I don't know of any RV8 currently using it.

- When you say "40%" enrichment I assume you mean 140% is the value in the warmup table, as 100% is zero enrichment, 140% is plus 40% and a value of 40% would actually be -60% from "normal" (I.E warmed up) value.

[Dave W]

Not sure if it'll help on all engines but I have had similar starting problems on both my 3.9 and on my LS1. I left the after start stuff as it was as I eventually decided that the problem is more down to the engine starting on a borderline mixture than anything that was happening afterwards. I think the "multiple starts" thing is down to the cranking opening PW being set too low. The first start it's too weak to fire, second start it's got a bit more fuel and will try, 3rd start and the cumulative build up of fuel gives it enough to start. Mine used to be a real pig, especially when it'd been left for a few days or more. It always started but some days you needed to be confident in your battery !

As well as the cranking pulse width the idle air control is also important and it's no bad thing IMV to crank the engine with enough idle air to run at 1500+ rpm in normal circumstances. Mine is 100% open when cranking due to a bug in the MS-Extra code, not sure which versions of the code have that bug in them.

Getting enough air in and a suitable equivalent of fuel makes starting the thing a lot easier, mine will start first time and idle from cold when it's not been started for a week without touching the throttle and the biggest difference between now and the original "will it or won't it starting" has been opening out the idle air during cranking.

The ASE is OK to bridge the transition between cranking and running but if your engine is running optimally from idle speed and you get the cranking pulse width correct to suit a wide open idle air control (and have the IAC open during cranking) the transition should be fairly smooth and painless.