Mapping advise. Misfire
Turbo Mini Forums

Evening all. Dont shoot me but I went and bought an Sc 5 port management kit. I'm mapping it on the road using my wideband and having success, great driveability compared to my carb and megajolt. My spec is 1293cc, Gt17' turbo, metro turbo inlet manifold opened up to 50mm to suit 50 mm SC throttle body, twin 660cc injectors, Delta Ecu. Audi TT intercooler.

Here's the problem. Despite the large injectors i can get a good idle at 14:1 afr, but at 1500, 2000 and 3000 rpm at the sam vacuum as idle, ie stationary, it misfires unless I richen it up to 12:1. This is gonna ruin any king of economy i might get as this is the pootling around/ de-accelleration area of the map and i reckon I should be able to set that quite weak as there is no load. Its ok at all other loads.

Ive tried opening up the plugs to 35 thou, putting a lot more advance in this part of the map (30degrees), but nothing changes. Any ideas. Cheers

So 40 views not one comment i guess my car is too boring, and crap, this is turbominis 2018 dying on its arse i guess.....
Did i forget to mention my car is made from old beer cans, weighs 180 kgs with full tank of fuel, i think megasqirt is better than Vems lol.
Now has that waken anybody up for a discussion or does nobody care no more.? NB this is a mini with a turbo on it that im asking about, thats whats this site was about, once no?

Edited by dazibee on 16th Sep, 2018.

I think the main issue for not getting any reply is that not many people use the SC setup. And I'm not sure how many of them do their own tuning.

If this were a Megasquirt setup I would tell you to make sure you use 4 squirts per cycle so that you have the best fuel distribution possible.

With the SC ECU, I have no idea how many injection events there are per cycle nor if you can change it. If it is fixed at something less than 4, you can very well have serious charge stealing which you won't be able to correct for. And the only way to know is to have at least 2 wideband O2 sensors to monitor the inner and outer cylinders (pre-turbo). With a single post-turbo sensor, you only see an average and that may hide a huge mismatch between cylinders.

It might be something completely unrelated to this but without the ability to check, it can't be dismissed. You could at least check the spark plugs to see if they look similar but that's only valid if you check them just after running in the problem area.

http://www.jbperf.com/

I didn’t have much success with the SC setup. I kept blowing headgaskets, this was due to the timing moving about, we never found why, I would be driving along and suddenly the timing would drop to -2! Nothing in the map we could see was doing it.
So I would do some data logs as and see what else is happening at the misfire.

Someone else on here a good few months ago from across the pond was haveing the same timing issues might be worth searching them out. Will had success with the ecu. I ditched my setup.

Edited by gr4h4m on 16th Sep, 2018.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Im fairly sure this setup runs 4 squirts per cycle.
My timing seems steady at the affected load / rpm site. In fact adjusting it makes little difference.
I was thinking because the throttle body is quite big and the inlet manifold has been opened up to suit maybe the gas speed is very low? i have since cracked open the butterfly a bit to get some air in and slowed the engine to tickover speed by retarding the ignition at idle to 5 degrees.

That gave me a decent idle, but it still wants to misfire 1500-2500 rpm only off load unless i richen it to 12:1 at these sites

Ive dabbled a little with the SC stuff on a K head motor, so not directly the same as not boosed so tps mapped, but I ran into a problem with timing at idle, and IIRC (its a few years back now) the issue was a setting related to the TPS that was fucking with the advance at idle. We got the car to SC and Simon sorted it in about 4 minutes and then mapped the motor.

Hardware wise I think the SC ECU is good but the user interface needs work, obviously Simon has no problems with it, but IMO its not as intuitive as other stuff. so its easy to overlook a setiing that will screw the tune.

timing wise, 30 degrees sounds ok, but you can probably go to more advance at a low vacuum, (I asume your below 50kpa?) Also there soule be no reason to open the plugs up, and i'd say that could compund the problem, a lean mix will be harder to light, so you might need to close them, I'd set them to std, or if i dodnt kow what that was 25-30 thou.

As mentioned I'd be looking at the plugs for an obvious mixture skew, maybe pointing towards an air leak that is leaning off 2 cylinders so you have a lean misfire despite being at around stoich.

Also, if you havent already, validate the timing is what you think it is, at idle, and at the RPM your seeing the issue, and that its not going awol due to an erroneous setting kicking in,
Also I assume your Wideband is calibrated ok to the ECU so they show the same, and Also turn off any closed loop fuel stuff, as this can swing the mixture causing problems, and if you do turn it on make sure its set to somthing low, like 5%, and not around 30 like Ive seen it set to on the SC base maps.

Joe raises a good point. I’m guessing Simon would be money well spent.
The interface is terrible when you look at others on the market. Some of the settings were not easy to understand.

As a side point I’d the trigger and sensor stable?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

I have closed loop turned off. Idle is very steady so dont thing there is an air leak. Lambda has been calibrated and the readings seem consistent. When the misfire starts the afr swings from lean to rich snd lean to reach etc.
I have spoken to the rolling road operator SC use and he told me to richen up the low load parts of the map where the misfire occurs. I have done this, the misfire has gone but it seems silly to have 11.5 afr when you have fuel injection.

With the carb there was no misfires, i am using a different vr sensor, coilpacks, leads now with the injection setup.
I think I will close up the plugs to 25 thou, keep the extra advance in, get it misfiring and using those Lazer spark plug testors which glow red, i can see if anything is happening to my sparks.
Last time I checked my plugs they were all the same, but the time before that number 4 was white. I need to check the plugs again

I’m just wondering if it’s just because you now can measure how rich it is that you are concerned. E.g was it always just as rich with the carb, but you just didn’t know?
I know the theory says with fuel injection that it shouldn’t need to be that rich but as we all know the throttle body injection and Siamese ports mean it’s never going to get anywhere near port injection and single injector per cylinder.

When i used to make my own needles i could get the no load/1000-5000 rpm parts of the needle all to afr 13.8:1 without any probs. Same engine and everything,up until i converted to efi a few weeks ago.

Schrödinger's cat - so which one am I ???

Also, you say that the vacuum is the same at idle as at your cruise/light load, but surely the throttle position isn’t the same. So surely you can set it differently to suit. If it needs 12:1 in a certain box to run nicely then thats just what it is.

Yea rod and tom you are probably both right. After an su I'm probably expecting perfection. If I find there is nothing wrong with the sparks/ecu settings I will set it how the engine likes and go for it. On a plus note I've only been pissing around with it a bit but I already have amazing drive ability. 2:9 diff ten inch wheels, 2.5 first gear, I used to be stuck in first gear round my local hilly roads by the speed bumps Now I can use second or third. Getting there. Cheers

I can set the idle mixture where I like it (13.8:1) same as an su. But no load sat stationary revving to 1.5,2.0, 3k is where it misfires. This is same part of map as deceleration around 30 mph
.

Edited by Rod S on 17th Sep, 2018.

Schrödinger's cat - so which one am I ???

This makes a lot of sense. Good explanation

All in all it would appear to be an engine/general arrangement issue rather than an ECU issue.

As said, all you can do is make it so it runs right and ignore the fact it's rich.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Ok guys thanks for the input. I will put it back together over next few days and try a few ideas