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Tunning my RR 3.9 V8


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i'm opening this post so, if you are up to it, can help me out how to tunne my V8 :)

this is my every day car.

i'm the 3º owner and i don´t know if something as been donne to the engine or not.

alterations made by me, tubular mild-steel 4-2-1 with just one cherrybomb in the middle. k&n air filter.

it as 112k miles.

after uploading Nige base setup i went for two runs and came up with the next VE maps.

from the original for the next maps it made a big jump in the higher rpm to the 100's bins. is it normal?

another thing i can ear a bit is that when i take the foot of the loud pedal and just let it slide sometimes i ear some poping from the back.

same thing going downhill for example at highway.

where a the 3 maps. original (Nige's base map, first run, second run)

p.s.- PWM disconnected




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Welcome to the wonderfull world of tuning MS ! :D

There is something that is now coming up over and over again as a basic issue, which I will add to the next modifications of the buold manual, and that is PWM Control

Its one of those things that is tricky to explain, but I'll have a go again for all :)

PWM - Pulse Width Modulation

= in english -

An autochoke to help start up from cold, AND a natty little unit that helps maintain tickover

A few techy bits

1. Its programmable !. Unlike the "Stepper" on the std engine where it jumps the revs up, then steps down and then again etc until tickover the Bosch unit I supply is programmable !.

So although I pop some basic values in there which will sort out and staert most V8s from cold to warm with a linear reduction in rpm (ie warmer it gets the lower the revs

become until it is at tickover) you CAN with some fine tuning get the cold starting to be even sweeter than my "Best guess sort of fits all" settings.

2. Tickover control

Ok, this is a real benifit to off road.

Your coinmg down a slope, feet off everything low low rom, and as you reach the bottom you fans kick in etc / and the engine stalls, the reason is that the

extar call of amps has dropped the engine RPM momentarily and its gonme and stalled. The PWM control stops this by having the ECU control the

tickover within a set frange - guess what - rnage is programmable too

3. So, you can set MS to maintain tickover at lets say 860 rpm and the valve will then sense with the ECU engine rpm at lo revs and helps ensure the tickover

is mainatained, it does this by adding in an ammount of extar air which then helps the engine recover etc.

4. On start up from cold the unit is set to (i set to 85%) of it opening, and then the ecu controls how much air vs rpm vs temp of engine it needs.IT POWEERS

shut !!

So, in simple terms a tickover controller and a cold start unit :)

Now the fun bits.............

5. The PWM control reads directly off the VE table.

So, lets say you have a cell value it reads of say 40, and the WUE (warm up enrichment table (Programmable and set by me with best guess for engine type) says oooh at

this temp I would like 130% of fuelling please = the ECU allowing the VE table not to give 40 of fuel but 40 + 130% = 52 "Units".


When you go out and tune, MLV or tuner studio will remap the VE table to give you what it belives is a more accurate MSQ / VE than my best guess

(hold that thought for a while -( calling this HTT !!) ) and rewrites the VE table accordingly.

Ooops !

lets say that on the retune the software decides that the table that was 40 was far far too rich, and rewrites it to 30.

Ok, engine seems fine, but then when you start from cold the program now says "brrrr I am cold, I want 130% of 40 please....

er......sorry 30 please = 39...very different to the 52 before tuning..

So, be aware tuning VE table will cause issues with WUE table.

To sort if you know the WUE was nice, then on the example above it won't be

it was 130 on 40 and was lovely and that was 52 units

its now 30 should be 52, to get the same then alter WUE for that value to rebalance

ie 30 and 130% = 39, wnat 52 change to 175% and not 130 and hey presto WUE is back on - or you can do it manually by starting from cold and

then increasing the cells until it "Seems Right (HTT again) "

Similarly tickover setting will be altered, and the PWM control may be off target now the VE table is changed in the cells it "Liked (HTT() - as

such you might wnat to just reenter the cells where the entire engine was hapy on tickover vs what MLV or Tuner stuido is saying ... (HTT)

Now, the tricky bit :P

PWM control is a POWERED CLOSED.

this means simply DISCONNECTING THE PWM and then going tunining WILL NOT WORK

IF YOU DISCONNECT THE PWM THE UNIT IS OPEMN and will allow air in, when you have remapped and reset the VE table, and reconnect the PWM power it will CLOSE and the engine will be all over the place inc tickover and general running.

YOU MUST REMOVE the PWM COMPLETELY - either via removing the PWM value and blocking the 2 x hose ends with a bung OR removing everything and putting the std hose back on which is ALSO BLOVKEDE INTERNALLY

THEN you can go tune.

Er there is more.

Before trying to tune the VE Table with PWM control, and even after you have removed / blanked off the Hose links you must

6. Calibrate the TPS (Megatune > Tools>Calibrate TPS>burn to ECU

Top box aim for say 10-30 bottom box 250-350 perfection is say 5 and 340 ish !

NOW you must check the ignition timing on the crank pulley vs what MS is saying, if they do not match either retrim the wheel until they do or change internally Spark>spark settings > trim + just add the number and if you wnat minus you must add - ie 5 less would be "-5" plus 3 would be "3"

7. before you tune the VE you MUST set the butterfly to get the tickover base setting right before tuning and DEFO before connecting the PWM

With PWM blocked etc turn the screw on the top of the plenum where the butterfly is and set the tickover to what feels right I use 840-860 autos maybe a tad more.

You cannot do the above unless the engine is warm, hot is even better.

8. You should now understand that you must balnk off PWM to set tickover, without doing this the PWM will try to compensate as you alter

the screw and the butterfly, net result will be a mess !

9. YOU CANNOT TUNE IN ANY WET WEATHER - even driving through a puddle will chill the lambda and send wrong

values and screw up your tuning, its gotta be dry guys !!

10. If the engine is super rich, say something big time wrong, or say CTS fails, then tuning may richen it even more !!

11. Too rich feels like too lean

So what does HTT mean ??...HOLD THAT THOUGHT

MLV is damned brilliant - in some ways Tuner studio even more so, but in some ways not.

You have to LOOK at what the engine VE is being altered to and think why, siometimes you may find a human number

added from say a value that it tickover happy with is nicer than what the software thinks, you can get the odd value creep in,

So some basica for tuning VE

Plugs NGKBR6RES and gasped properly

NO and I mean NO EXHAUST LEAKS - lambda will be waaaay off

Butterfly and tickover set with

Tickover checked and verfified as correct against MS

DRY weather no puddles

Check all gauges on Megatune are working

Concentrate on

Tickover and timing and PWM removed and then VE table tune

Then reset VE to give Tickover

THEN add Pwm in and reprogram PWM values if required

along with WUE table


When you tune you can ONLY match the datalog with the MSQ being tuned. When you have run the log and

uploaded the new MSQ uits the NEW msq that you then relog, the OLD MSQ and the OLD Datalog are now irrelevent in the tuning process.

MS creats dreadfull fiole names - I use

date - Time - where


23rd Oct13 MSQ 1 Motorway run.msq

Call the Dta log the same and then I know what goes with what.

NEVER run a log and then apply to any other MSQ than the on it has logged from !!

There is a huge amount on tuning basics in the MS Forum index thread here that I have popped in over the years worth a read for any tuner to be :D

Hope this helps


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Nige... you're the Man :)

basically i'm going to load your original map and start over.

i'll be posting updates.

another thing i notice is that when a light touch the loud pedal from a stand still it doesn´t go, the rpm goes down.

and i looked at the TPS signal and it goes dead link.

if i step it harder the signal comes back on and it goes ok.

the TPS is 3 months old Lucas part.

allready calibrated TPS with 24 down and 254 high(can get higher then this value even if i turn it by hand)

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Ah ha

No, the AFR souldn't flicker like that

I would expect it to sit at 14.7 / 12 o clock on cruise, when you boot it to wind to a lower number (lower = richer) and when at high RPM backing off go clockwise higher number

Would suggest you check your lambda wiring ?

2 x whites - 1 x white goes to 12 volt power, the other white to a chassis GROUNd / earth

Grey to ecu earth

Black to Blue on harness


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Question :

about TPS threshold, if my TPS is closed and calibrated with a value of 17 and the threshold is at 35. as i open it, the idle valve will still be open until the TPS hits 35, adding to much air.

shouldn't it be set to a closer value as 17TPS - 22Threshold, making a smaller overlap?

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TPS Threshold is the point above which the idle valve closes in ADC (as it is no longer needed).

Idle Activation (rpm) is 'how many rpm' above idle that the idle valve returns to operation after the throttle has been opened and closed again.

This follows the idle speed as it is interpolated from Fast Idle RPM to Slow Idle RPM

ie touch the throttle and the TPS will jump and also the rpm, yes you can tweak the TPS Value but fairly acedemic


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It's hard to tell when you type stuff on yer bl**dy iPhone, it's like someone's dropped a bag of scrabble letters...

I always think beyond about 3k you're just making noise, unless it's a situation where changing gear would kill momentum (hill climb, thrashing through a mud run) just use a different gear.

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eheheh i usually don´t rev it that hard.

most driving around town don't go over 2200rpm.

about the weird lambda signal, confirmed the wires color and everything is right.

it's raining like hell for the next couple of days so only next weekend i can get under the car and check continuaty signals with a multimeter.

any other suggestions to find out what's wrong?

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Is the serial cable wobbling at all?

The AFR gauge is pretty meaningless with a narrow-band lambda, the row of dots along the bottom of the screen shows you the sensor voltage.

I know Nige said you shouldn't tune in the rain because the lambda can get cold, which is true, but you can tune by the seat of your pants, especially things like accel enrichment.

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It's hard to tell when you type stuff on yer bl**dy iPhone, it's like someone's dropped a bag of scrabble letters...

I always think beyond about 3k you're just making noise, unless it's a situation where changing gear would kill momentum (hill climb, thrashing through a mud run) just use a different gear.

Eh, mine wakes up a bit above 4k :ph34r:

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FridgeFreezer don't remenber if the plug was just pluged in or if it was screwed to.

could you look at the video above and see what you think about the signal?

it looks like the dots are more stable then the afr gauge, but i don´t now what they should look like

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I'm doing something wrong when this is correct:

Would suggest you check your lambda wiring ?

2 x whites - 1 x white goes to 12 volt power, the other white to a chassis GROUNd / earth

Grey to ecu earth

Black to Blue on harness


I thought I read somewhere the 2 whites are for +12V... Am I wrong? Then it explain why I read wrong. The white back to the ECU earth is not good I suppose?

Why they didn't create 4 different colors wires for that sensor :glare: ...

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I'm I readng it off, this is a email from last year:


lambda easy

White + Purple is Power to Lambda - 1 x of the white wires
the other white wire is +12v feed (ie one is heater and one is power)

The blue joins to the signal - Black, and yes grey = Earth, yes I know it doesn't make sense !!


I know, a bit late on my response, just started tuning (RR is running great, even with base map of you)!!!

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