Throttle tip in ignition retard. Feature request

[sd1nl]

Hi,

Would it be possible to implement a possibility to retard the ignition as a function of tps/dot. This way you could retard the ignition a littlebit every time you touch the throttle.

I have been experimenting with this and it works a treat. It makes throttle transitions super smooth, especially when tipping the throttle after overrun.

Would be a great feature.

Rene

[ol boy]

In the Autronix ecu they have both accel and decell timing table. I'm not sure why you'd need it. My timing table falls away from higher timing values at lower load to higher load so any jump in MAP value will pull a few degrees.

[sd1nl]

It makes throttle response very smooth, almost cushened. I think most oem ecu's do the same.

A decell timing change i don't think is very useful.

[Matt Cramer]

I've heard this feature is often used to make throttle response a little slower to prevent shock loading the drivetrain.

[sd1nl]

I've heard this feature is often used to make throttle response a little slower to prevent shock loading the drivetrain.

That is what it does. it works especially well on manuals. It's just a few milliseconds retard that does the trick.

[muythaibxr]

On speed density, MAP can take a little bit to change relative to TPS input. Retarding while waiting for the MAP sensor to catch up with conditions and therefore the spark table lookup to catch up with conditions could help response I'm sure.

Ken

[sd1nl]

I use spark table switching controlled by a programmable output/input to do this at the moment.

Would it be possible to implement such a feature in MS2/MS3?

[muythaibxr]

I use spark table switching controlled by a programmable output/input to do this at the moment.

Would it be possible to implement such a feature in MS2/MS3?

Possible? Sure. I need to discuss with James, and at the moment timezone difficulties are getting in the way of that.

Ken

[ol boy]

How many degrees of retard are we talking about? 2 or 3? 10?

[lagos]

I actually noticed that a few aftermarket ecus do this. Vipec has it setup for about 3-5 degrees of transient retard for light transients. I was wondering what the idea behind this was when I saw it.

[sd1nl]

How many degrees of retard are we talking about? 2 or 3? 10?

I pull 8 degrees at the moment. But it would be nice to be able to pull less at low tpsdot and more at high tpsdot.

[pigga]

Hi.
This topic came up over here already some years ago.
I have similar problems at low engine load and/or low speed/RPM. Car is jerking under some conditions. So I think an improvement of transition to overrun fuel cutoff makes sense!

Bosch Mono Motronic does this in a similar way: As soon as overrun- cut-off conditions are met, Ignition is being retarded, and then Fuel is cut off.
On the opposite: Fuel kicks in first and then ignition is advanced (and I think that's the more important part!). It is advanced very quickly, but this dampens the jerking during transition from overrun to normal drive in a very effective way.
So if you follow this strategy, it would be possible to couple the ignition retard to the fuel overrun cutoff timer. Unfortunately I have no idea about how to advance ignition at the transition from overrun to normal drive.
The secondary effect is a characteristic "bubbling" sound from the exhaust, but that's another story....

[jsmcortina]

pigga,
I'm not sure where over-run fuel cut comes into this? The topic is about altering ignition timing when you touch the throttle.

James

[mrx79]

I know that topic as well.
There are two points to consider:

1.) general damping of load changes (mostly positive ones from low load to high load)
2.) smooth reangagement after overrun is left.

The 1st problem is solved by modern OEMs usualy by slowing the gradient of the electronic throttle, but could also be realized by an immediate ignition retard by x degree, followed by a linear advance y deg/10ms for example until final ignition value from ignition map is reached again.

The 2nd problem can be solved as described: when you enter overrun cutoff, retard is retarded with x deg/sec until a bottom limit is reached (i.e. -15deg is a common values for modern OEMs). Then switch off ignition. Exhaust sound can be influenced by the time you run with late ignition and of course the later the more sound ;-)
When you then go back on the gas pedal, start with late ignition (-15 deg from above) and reengage injection, then ramp up ignition to ign. table value with x deg/sec.

This would greatly improve drivability with just a few constants... would be great to have that in MS2...
Especialy for the manual gearbox guy's like me with small agile engines with big throttle bodies and small intake manifold volumes a lot of jerking issues can be fixed easily.

Please consider that...

[pigga]

pigga,
I'm not sure where over-run fuel cut comes into this?

Hi James.
No offense, it was not my intention to cause (additional) confusion.
I assumed that "tip in" of throttle means a transition from 0%TPS to any higher value. But maybe that's a misintrepretation from my side, sorry.
The transition cruise <-> overrun is the most common point where I use to notice a lack of drivability and where I would appreciate such a feature. That's the reason for my description how some OEMs have implemented it.
I am not sure how a general ignition retard/advance feature (based on TPSdot) would follow physics?
Then I'd rather suggest Ignition Advance based on RPMdot makes more sense. High RPMdot at WOT indicates lower engine load and allows a bit more aggessive ignition timing whereas low RPMdot indicates higher load and needs more retarded ignition. That would follow physics to my eyes. But that's another Story.

[muythaibxr]

pigga,
I am not sure how a general ignition retard/advance feature (based on TPSdot) would follow physics?

Actual MAP lags behind TPS, our reading of MAP lags behind that (lag factor, table lookup, etc..). TPS gets out ahead of all that, so you could retard based on TPS or TPSdot a little ahead of the lookups happening so you have the right timing sooner.

Then I'd rather suggest Ignition Advance based on RPMdot makes more sense. High RPMdot at WOT indicates lower engine load and allows a bit more aggessive ignition timing whereas low RPMdot indicates higher load and needs more retarded ignition. That would follow physics to my eyes. But that's another Story.

What about that follows physics? As long as you have a wheel with a decent tooth count the right timing should be right period. I've heard a lot of people talk about doing something RPMdot based, but I've never heard a convincing story physics wise for why that is necessary. It seems more likely people are making up for the timing calcs being behind the actual conditions due to low tooth count wheels (which can be made up for with prediction).

In either case, we're not adding new features to ms2 unless there is a REALLY good case for it. We'll likely add something to ms3 (TPS based) for the 1.5 firmware.

Ken

[pigga]

In either case, we're not adding new features to ms2 unless there is a REALLY good case for it. We'll likely add something to ms3 (TPS based) for the 1.5 firmware.

Hi Ken.
I totally understand you point of view. I was not expecting you (the developers) to implement new features into MS2 but saw this as an interesting interchange of some ideas.

What about that follows physics? As long as you have a wheel with a decent tooth count the right timing should be right period. I've heard a lot of people talk about doing something RPMdot based, but I've never heard a convincing story physics wise for why that is necessary. It seems more likely people are making up for the timing calcs being behind the actual conditions due to low tooth count wheels (which can be made up for with prediction).

Yes. You are right. This is one aspect. That's for sure.
Furthermore, I am not sure if I am 100% right, but consider the following:
Did you ever notice that motorcycles have a high compression ratio, often in combination with a lower Octane Rate recommendation?
I know from my circle of acquaintances about some cases where motorcycles Engines were fitted into some Cars/Buggies for Race applications.
It was common to all cases, that the engines who were swapped with the whole OEM and Ignition stuff into the "car" faced problems of Knocking. Even high octane fuel could not cure the problem. Re-Mapping the ignition table (with some aftermarket-ECUs) cured the problem i.E. the OEM Ignition settings were too aggressive for the new application.
So, to my conclusion the Engine load has influence to the maximum pre-ignition that is possible. On a motorcycles you never have constant RPMs at WOT unless you reach Vmax at top gear.
So -that's my assumption- the speed of revving-up influences the maximum pre-ignition and the tendency of the engine to start knocking. The one extreme is constant RPM at WOT, the other one is revving-up the engine at neutral.
Anyone any idea?

[muythaibxr]

That is an interesting example. It could still be the low tooth count issue though. Most bike engines don't have a large number of teeth because they rev higher than car engines.

[dontz125]

On a motorcycles you never have constant RPMs at WOT unless you reach Vmax at top gear.

I'm hard-pressed to think of ANY land vehicle that sustains constant revs at WFO, unless you are -brutally- lugging the engine. In that case, that's not knock you're listening to, but rather the engine typing out its CV to go find another job ...

[pigga]

On a motorcycles you never have constant RPMs at WOT unless you reach Vmax at top gear.

I'm hard-pressed to think of ANY land vehicle that sustains constant revs at WFO, unless you are -brutally- lugging the engine. In that case, that's not knock you're listening to, but rather the engine typing out its CV to go find another job ...

true....true....
The bottom line of my statement was the assumption, that not only TPS/MAT/MAF indicates the actual load, but also the actual braking torque (<-don't know if thatś 100% the right term) at the crank.
So WOT at 1st or 2nd gear is not the same situation as WOT in top gear. Of course, if your car has thousands of BHP and a huge turbo lag you will have other problems when you hit the throttle, no matter what gear. If you have automatic transmission in combination with a torque converter you will not face these problems, either. I was rather thinking of NAS engines with manual transmission.
However, glad to see that my posting causes exhilaration. Better than nothing.