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** MegaSquirting a V8 - "Basics of How to" ... The A-Z Saga

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Hi and welcome !

We are all still around....

Will post up when I have a few more mins just off out !


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Hi and welcome !

We are all still around....

Will post up when I have a few more mins just off out !


Thanks Nige,

Waiting with baited breath and crappy running engine...although I made it idle nice ;-)

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What exactly are you after

Quoting a quote here so not sure how it will look, but here goes...

FridgeFreezer, on 10 Sept 2007 - 7:37 PM, said:snapback.png

Since this is turning into a bit of an MS-tech thread, here are a couple of maps for people:

First off is a standard (B&G standard code, 8x8 tables, fuel only) settings file from my RR 3.5 V8 after a bit of datalogging & tuning, the idle isn't perfect but the rest of it is close and I have been running these settings (albeit with a less well tuned map) for years now:


I would use this as a base settings for any stock RV8, just up the fuelling (REQ_FUEL in constants) by a certain % for larger engines.

Second is an MS'n'S-E setup - the engine is 4.6 V8 with "stump puller" cam, running version 029V of the MS'n'S-E code, EDIS-8 ignition, again this has been datalogged & tuned up and is actually pretty good, certainly I don't feel the need to tweak it any further right now (although if Bill & Dave turn up next weekend it may get fiddled with):


There's plenty of reference on this thread and others to finding msq files all over the place.

My Google Foo is strong and yet I cannot find any of the little buggers.

Everywhere I look they are old, expired or deleted links.

Would be great to have an updated list of files here on the forum somewhere to centralise the known good msq library.

Mean time, I have put together my own VE and Ignition tables from the various screenshots herein and have got her started but would be nice to have seen an MSQ from scratch.



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email it to me at megasquirt.v8@gmail.com and I'll have a lookie and report back here with findings :D


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email it to me at megasquirt.v8@gmail.com and I'll have a lookie and report back here with findings :D


Nige - you should ask little Dave to make a basic "msq library" page for your website with a few base maps to download. Even just the .VEX files for fuel/spark would be useful.

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On 12/17/2007 at 2:24 PM, Bull Bar Cowboy said:

Close Loop Idle Valve

For me the inclusion of a valve was going to serve two purposes……..

1. Provide a fast idle with a linear degradation to operating temperature.

2. It seemed good idea that if I could get it to work in closed loop mode then in some off road situations it would allow me to idle over obstacles without intervention of the throttle……..

The valves work by applying a PWM (Pulse width Modulation) signal to the solenoid coil of the valve ………….. the true DC (volts) value will depend upon the length of the pulses applied …………… therefore this gives an infinitely variable voltage between 0V and the vehicle max volts (14V). These valves come in two flavours……… rotary or plunger………. the solenoid coils also come in two flavours……… single coil where the valve has a sprung return, or dual coil….. one coil to open and one coil to close.

I opted to use a single coil sprung return rotary valve …………. Taken from a Volvo 940 2.3L turbo . The valve itself has 20mm inlet and the ability of move a large amount of air…..

Installation is easy………. throw away the plenum stepper motor and replace with a blanking plug (thanks HFH) and then plumb the valve between the throttle body air outlet and the plenum EAV inlet. If the valve is mounted just behind the plenum then the valve to plenum pipe can be ETC6370 and the throttle body air outlet to valve can be the same pipe from the Volvo 940.

These valves work in the following sequence ………… @ 0V the valve is slightly open…..@ low volts the valve is closed……..@ low volts and increasing volts opens the valve. The reason for this is if there is an ECU or wiring fault then the default value is a fast idle.

Most documentation about these valves show @0V slightly open …….@ 25% duty cycle, valve closed ………@ 40% duty cycle, normal operating area….

Bench testing the valve on a variable power supply showed this to be true …….. circa 3.5V and valve was closed and it began to open as the volts were increased to around 4V………….so, as 3.5V is 25% of 14V then the 25% duty cycle rule is correct.

You may think this is a lot of faffing around …………. but its important later.

Here I will detail my errors (that cause a lot of head scratching), because I know that others will encounter the same issues.

With the valve plumbed in and unpowered the idle was about 1800 rpm ……….. I decided that was a bit high and reduced that the 1200 rpm by closing the throttle stop a little ………. WRONG ……… but more about this later………

With the valve connected and following the MS (idle valve) tuning info I got a really good and stable idle using the following settings………



One of the reasons for using 100 (arbitrary number to set the frequency) as the PWM frequency is that the duty cycle is only true at 100 and that it gives the valve 1% resolution. At higher or lower frequencies you need to calculate the duty cycle.

DUTY CYCLE% = Lower or Upper dc * 100 / Idle Valve Frequency value

The test of idle stability was to quickly turn on and off the heater and 750Watts of lights…… the idle would take a slight dip from 850 rpm and very, very quickly return to 850rpm ………….

With Meagtune, its best to set up an “idleDC” gauge so that the operation of the valve in terms of % duty cycle can be clearly seen. The operation was very clear……… with no engine load it was running @42% - 44% DC ………. by loading the engine the valve was opening to 58% DC……….. on open throttle it was closing to 25% DC …………..

The only real problem at this stage was the ‘settle’ time from an engine start……. However, the first test drive produced another issue ………. after a decent overrun (say coming up the standing traffic or lights) the idle would dip and an engine stall would occur before the idle control had chance to recover…………..not good…

After a bit of lateral thinking ………… idle control systems must have to rely on a good base idle as the mechanics of the valve would not allow huge quick changes in open/cloe to find the correct idle valve ……….. in this respect a stepper motor would probably perform better and the changes could be more precise, but, without a base idle reference the performance would be far from perfect.

So … to set the base idle I used the following procedure ………… disconnect he valve from the plenum and blank the plenum air inlet. Then set the base idle (using the throttle body butterfly stop) to a value that is just below the required controlled idle ……… I set mine to 800 rpm as I wanted a controlled 850rpm……

Reconnecting the valve and test driving, confirmed that the stalling issue was resolved and the idle was perfectly stable @850rpm………….

The next issue was the settle time from an engine start ………

Even on a hot engine the valve was taking too long to settle, thus giving an oscillating idle for maybe 10 or 20 seconds immediate after an engine start…………….once settled the operation was fine.

If the first start sequence is carefully watched ………… the valve opens to the cranking duty cycle, then closes to the ‘closed value’ as the engine fires & runs (provided the throttle is open….which it will be) and then as the throttle is released, it goes back to the cranking duty cycle value and steps down from that to try and find the correct idle………

Where as …………. Once the engine has been started and idle has been found, then following that point the software uses the minimum duty cycle setting to find the correct idle value …………. big difference

So ………….. to over come the start issue I tried setting the cranking value to be much closer to the minimum value ……….. in that way the valve has a much smaller operating range in which to find the correct value ……… as the operating value is 42% - 44% (@ normal operating temperature) and the minimum is set at 40% …………… setting the cranking value to 45% means the valve only has a small window in which to ‘find’ the correct idle. On a cold start the value opens up to 52% (dependant upon IAT).

This setting has now completely cured the start up issues on both warm and cold starts………….


megatune shots..................Warm engine


Cold Engine................


It seemed to me that the engine / software responds better to the valve opening, rather than closing from a high open value …………. I guess that makes good sense if you think about.

Its not absolutely 100% perfect to my liking (probably about 98% perfect) as there is a very slight overshoot on load variation ………… I can see it because I am looking for it, but I guess it wouldn’t be noticeable to anybody else driving the truck. However, I am reasonably sure that this can be resolved with a little bit of fine tuning of the settings.

The final test was to go up the farm and see how it performed in low range 3rd without any throttle input ………….. it behaves just like a diesel driven in the same manner, only maybe a little more controlled ………..it took a very steep slope to stall the engine and literally walks over obstacles that would have need to have been ’driven’ previously.

Have fun !



I don’t suppose anyone has the images from this post? I’m struggling get get my valve and idle working nicely.

Alternatively, can anyone share their settings. I have a standard 3.9 with Nige’s kit bolted on.



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