Ignition timing on megasquirt

[Automania]

Hi guys wondering if anyone here can help. I'm running a 4.6 on ms, I've had a problem with it since fitting, which is a flat stop from idle. I've took it to a garage who've said they think it's a timing problem. Now the map I've been given should apparently run it pretty good. But the timing at idle is 10btdc, the garage seems to think it should be more like 6, which after googling seems like the standard value. Can anyone advise on this? Many thanks mike

[DaveEFI]

If you mean a flat spot from idle, more likely the acceleration enrichment needs adjusting. Are you using speed density or alpha-N?

IMHO, starting out with some else's map is not the best way - as most engines fitted with MS won't be standard. So no standard map. And you won't learn the software. Better to start out from a clean base install, and work thought the tuning sequence.

[sidecar]

The standard figure usually quoted for the idle timing is 6 degrees and in my opinon this is a really poor figure to go for. Even a standard engine will run better with more idle timing and of course this increase in timing is carried all the way through the rev range. On a standard 4.6 I'd be looking to run 12 at idle and 28-30 all in at around 2750-3000 RPM.

When you add a vac advance system into the mix this will also have to be taken into account, I don't know whether your system has this feature or not.

My lump runs a 'warmish' cam, quite big headers and stage III heads so in other words it is not standard, I run 18 degrees advance at idle, 28 at 4700, then advancing to 32 from 4700 to 5000 RPM. (It's a programable MSD system)

As your system is 'clever' like an MSD system you can start to get clever with the advance curve, you can add more advance at the point where you think that the VE is falling like a stone. (But you really need a dyno for this sort of thing). Having said that if you just want a basic curve which means that you can eliminate it as being a problem then just go for 12 at idle, 28 all in at 3000 RPM, with a vac advance system you could get it to add another 12-14 at cruise vacuum (which you would have to measure). It must drop thsi extra advance as soon as the throttle is opened much more than a crack. (Maybe drop the vac advance when the thottle is more than 1/4 -1/3 open)


Like Dave said, you are best off just learning how to use the MS then set up a map that suits your engine. One thing you could get from other people which would give you a start is the air fuel ratios that other people are using with an injection engine, you could then aim for these settings. I could give you my AFR readings but I run a carb and my cam makes my engine dirty at idle so they won't help you much.

[Automania]

If you mean a flat spot from idle, more likely the acceleration enrichment needs adjusting. Are you using speed density or alpha-N?

IMHO, starting out with some else's map is not the best way - as most engines fitted with MS won't be standard. So no standard map. And you won't learn the software. Better to start out from a clean base install, and work thought the tuning sequence.

I initially thought that, but was then told to leave the ae well alone. I'd have to check on the speed density/alpha-n question.

The map I was given was from Megasquirt v8, and nige is confident it should run without any major issues on the supplied map. It has been suggested air leaks etc. but I've checked what I can there and everything seems ok, but the garage seemed to think the timing is out.

This has been on going for about 9 months now but to be honest I've barely used the car as its so bad to drive, the problem being finding someone to look at it, many thanks for your help

[kiwicar]

Hi
from the problems I had with mine can I make some suggestions.
Check that you have the timing reference pointer spot on, not +-2 degrees but dead on and that TDC no. 1 cylinder lines up spot on on the timing marks on the damper, from there recheck that the MSQ thinks the timing is correctly set up, I found the method described in the manual and on Tuner studio gave inconsistent results the first couple of times I did it, this was probably down to me but double check that when you set it up that you have defiantly have it on fixed timing, get every place it can be set to fixed timing not just the first one you find. I am assuming you are using a trigger wheel and have not converted your 4.6 to a distributor.
On my engine, it is a chevy not a rover, I found I need 12 degrees of advance by 700 revs and 18 by 1500 revs, 6 degrees is not anything like enough. Check where you have the cranking advance cutting across to the table values and that this is well below the idle revs, check it has enough advance when cranking.
Personally I would build your own ignition map from the stock one in tuner studio, it is simple to do and it gets you understanding what the bits of the table mean and you get a feel for what the changes you make do to the engine.
Best regards
Mike

[DaveEFI]

My feeling is the timing would have to be *miles* out to give a flat spot. I have EDIS on my bog standard Vitesse unit (with MS) and if you disable SAW so it runs on the fixed 10 degrees BTDC, it just feels very lifeless - but no flat spots.

[DaveEFI]

I doubt the average garage would know where to start with MS. You'd need a specialist who knows them.

I'm sure using someone else's map works sometimes - but there are a lot out there which won't (for your exact engine and setup), and simply cause frustration.

IMHO, you either need to give the vehicle to an MS specialist and get them to install and tune it - or DIY, including starting the tune from basics. I don't think there is a decent middle ground.

[Automania]

Well if I'm under the bonnet and a blip the throttle, say half throttle, it almost stalls its that bad, further up the rev range is fine just from idle. It also hunts at idle, I presume that its the same problem causing both issues but I'm only really bothered about the flatspot given the choice. Air leak on the inlet was suggested but I'm not sure as I've done a hell of a lot of work to check that out to no avail.

Thanks again mike

[Cobratone]

My first thought was that your fuel table is too lean just off idle. Find your idle point on the map and just above and to the right increase the fuelling by 20%in a 4x4 block and try driving the car, it'll probably be too rich then but it should answer whether being too lean is the fault. If it makes no difference then go back to as it was. HTH

[Automania]

My first thought was that your fuel table is too lean just off idle. Find your idle point on the map and just above and to the right increase the fuelling by 20%in a 4x4 block and try driving the car, it'll probably be too rich then but it should answer whether being too lean is the fault. If it makes no difference then go back to as it was. HTH

Ill give that a try tone, thanks.

[SimpleSimon]

Cant see how you could use a RV8 generic map and get away with not touching AE there is just to many variables from one motor to another, and if that timing figure you have is what the motor is actually seeing thats not going to cause a flat spot but like Sidecar says you can generally get away with more adv at idle with benefits

[stevieturbo]

Unless it is an actual crank signal error causing a total spark loss, it is highly unlikely your problem is spark related.

It does sounds fuel related. Flat spots can just as easily be too much fuel as too little though

Has the engine ever been tuned properly, or just guessed ?

[daxtojeiro]

Its highly unlikely to be an ignition timing issue if its not under load when you have this stumble.

For starters have you tuned the base fuel map using a wideband lambda and got it running nicely? Have you checked the timing using a strboe?

Until the fueling is done (VE Table) you cant setup the Accel enrichment, so forget blipping the throttle until the fueling is sorted.
If you are simply using the base map then this will never work, there is no such thing as one map that will generically fit. Ive sold so many MS ECUs for RV8s and non of the maps ever end up the same.
Get yourself a wideband and start tuning it, then once the fueling is sorted start playing with the AEnrichment.

Idle advance should be 10 -16 depending on your cam, 16 is the norm for a performance cam, but that wont cause your issue,
Phil

[daxtojeiro]

PS, if you need someone to tune it for you then have a chat with Shaun from www.MS2tuning.com but be prepared to get it swapped out for an MS2, the MS1 isnt really worth using these days, even though I wrote a lot of the code for that processor I wouldnt use an MS1 on an RV8, the MS2 is much much better,
Phil

[Automania]

Its highly unlikely to be an ignition timing issue if its not under load when you have this stumble.

For starters have you tuned the base fuel map using a wideband lambda and got it running nicely? Have you checked the timing using a strboe?

Until the fueling is done (VE Table) you cant setup the Accel enrichment, so forget blipping the throttle until the fueling is sorted.
If you are simply using the base map then this will never work, there is no such thing as one map that will generically fit. Ive sold so many MS ECUs for RV8s and non of the maps ever end up the same.
Get yourself a wideband and start tuning it, then once the fueling is sorted start playing with the AEnrichment.

Idle advance should be 10 -16 depending on your cam, 16 is the norm for a performance cam, but that wont cause your issue,
Phil

Thanks Phil. I had done some tuning and had also fitted a wideband mtx, but I was told not to bother with the wideband yet and that the map I had ended up with after tuning was all over the place, but it did run better, the issue I had with this was that it could have just been tuning out an underlying problem with the engine??

Yep I originally checked the timing with a strobe and it was pretty much as mt said

It's a crower cam, can't remember the number of hand but something like 30229.

It just worries me that In tuning the maps I may still have an underlying problem, and the tuning is just covering it up. The engine wasn't run as it is now.

Thanks again for your help guys