Tunning my RR 3.9 V8

[Hybrid_From_Hell]

Oh yes snorkels do make a difference !!!!!

I have mine disconnected for road use, as need the extra BHP, it slows it with the snorkel connected.....

Nige

[csimoes]

Oh yes snorkels do make a difference !!!!!

I have mine disconnected for road use, as need the extra BHP, it slows it with the snorkel connected.....

Nige

lol lol yes because your 5.2V8 must veryyyyyy slow ahahahah

[csimoes]

another session of tuning and playing with MS

issue to solve: hunting at idle on LPG and rpm sticking at 1200-1300rpm on deceleration LPG to (not allways but most of the time, i was solving it by sticking a higher gear and let it bog a litle and then it would would start hunting again for idle

on petrol it's okish but LPG was nasty 200rpm hunting

first thought it was the LPG ECU messing it up but then i thought.... i have MS so i have to be able to solve it

after a couple of hours playing with it i solved both problems

solution: i bit of change of VE table for LPG and a lot of change on LPG spark table!!!

VE wise petrol is

44 44

41 46

LPG is

43 43

41 47 (i think LPG ECU as something to do with this values....)

and the big part of the solution was the spark table

here's a pic of the tables. the original one gave by Nige (great table allround except in the idle and deceleration part, for me at least) is on the left and on the right my final result.

basically i had to do that pit marked in yellow and lower a bit the timing around it (marked in red). idle solved, maybe not perfect perfect but more then good enought

i still had the deceleration problem.

i have over run cut off activated at 1500rpm and lower then 30kpa

after a few bleeping of the loud pedal i notice that on deceleration around the 1500rpm mark it couldn't go down because of the very advanced timing, it would accelerate by it self and idle at that speed.

what i ended up doing was that channel marked in blue with low timing so it go down without any effort

the 20 marked in black i left it like that but being at 35kpa i'll probably rise it again

and voilá problems solved

now i would like to get some feed back from the gurus out there about my problem solving.

am i solving this like trying to nail down a litle nail with a sledge hammer?

[Bowie69]

Interesting spark table tweaks, I shall try that on mine at some point I think, albeit ion petrol.

You may find 1500rpm for fuel cut-off a little low, 1800 seemed better for me, otherwise it could trigger hunting.

[AncientGeek]

I found MLV overdoes it a bit on long runs. <30 mins is ideal.

[csimoes]

i've notice that when tuning the idle as time passed it would start to be unstable again.

then notice that the MAT was rising and the more unstable it got.

so i think next step is to setup the correction by coolant correct air density.

can anyone help me with this stage?

[Bowie69]

Automatically tuning the idle cells is a bad idea, do it by hand to get a stable good idle at a good mixture.

Yes MAT will rise when sitting idling, but I wouldn't change it from anything Nige has set up, it seems to work just fine...

[csimoes]

i've been doing it by hand.

but today air temperature is around 13ºcelsius and after 15 minutes of idleing and playing with it, MAT went up to 51º celsius..... that's impossible on a winter day like today

if it was a summer day i would believe it but today.... must be heat sink.

the correction that came with the ECU is set at 100%, if i understood it right at 100% it's neutral

or should i set it to normal correction? (that's not what it's on now)

[csimoes]

little update

idle it's resolved.

at least it seems like it.

didn´t mess with the IAT correction but after Reading another post on here about setting the idle i reduced a bit the base idle (the little screw on the plenun) and the AFR became much richer 13's something and it's great.

the other problem of rpm coming down and sticking and X rpm, wich i resolved with the ignition map, wasn´t perfect and it still happened sometimes. now that i fixed the base idle it wasn't happen again...

so next step is to put back the initial ignition values and see if it's still ok

hope this will help the rookies like me

[csimoes]

Christmas update

idle, chapter two

everything was fine until the IAT's values go up...

after surfing the web ended up at http://www.mez.co.uk/ms15.HTML

applied those changes and bingo!

now idle is allways stable.

i ended up with a few different values but very close. also changed the start and end rpm for correction. i used 1000rpm to 1500rpm

my values are:

100

103

105

107

109

110

111

merry Christmas everybody

[FridgeFreezer]

Excellent, another problem solved!

[Hybrid_From_Hell]

That is a very interesting bit of info....I am going to look at this maore, but great idea.

Mez (elliot) is a true MS enthusiast, nice guy, and top chap BTW...and clever too boot !

[AncientGeek]

I also use that technique but I go further.

First of all beware of using examples from England if it gets hot where you live. A real air temp in the high 30's is not unusual for me.

• I moved the mat sensor out the engine compartment.
• Modified the airdenfactor.inc to reduce correction by approx 50% and recompiled. Subsequently fine tuned by analysing log files looking for ego correction at different temperatures. I admit I am defying the laws of physics by doing this.
• Also added IAT correction like yours but mine starts at 40 degrees. Stops at 1500 rpm.

If you modify airdenfactor.inc you might consider another mod which I came up whith after having a sensor failure. MS is designed to default to a limp value if the sensor fails but it did not work for me as you never read 0 ohms or infinite ohms across even a disconnected sensor. Consequently my engine was being fueled for -40 degrees. So I extend the use of the limp home value.

for example the top of my file look like this:

DB 100T; 0 - sensor failure, use limp home value.
DB 100T; 1 884 474 10 ohms
DB 100T; 2 654 346 20 ohms
DB 100T; 3 554 290 30 ohms
DB 100T; 4 494 256 40 ohms

[csimoes]

good info

i think that i ended up in Mez page after Reading a post by you on megasquirt fórum

one thing i'm going to do is to change my steel air box for a plastic one from a later RR Classic (300tdi). and put the sensor on that box.

this way the heat soak will be a lot less, the sensor won't be right over the headers and connect to a piece of metal.

i hope this helps with that problem.

indeed it can get a lot hotter here then UK, after changing to the plastic box i'm going to try your numbers.

here did you put the IAT sensor?

Some more hollidays tuning

when i touched the acelerator very slowly ( slower then the slow point of acceleration enrichment) the car would bog down and then when i pressed the pedal more it then picked up the rpm... annoying.....

looking at the AFR gauge i could see that it went very rich at that moment.

what i concluded was that when i touched the pedal it would close the PWM and it didn't have enought air at that moment.

my TPS is set at 27 - 254

my TPS threshold point at Idel Control was at 35

i then moved the TPS Threshold point to 45 and Voilá.....

i can now press the pedal at idle very slowly that the car does die and after the threshold it picks up rpm without any problems