Barometric fuelling and timing correction

[racingmini_mtl]

Where do I get 3.3.1? Keen to try it. Search does not search on 3.3.1...

The sticky thread with 3.3.1 in the subject: http://www.msextra.com/forums/viewtopic ... 01&t=52147

Jean

[dontz125]

It's stickied in Support, not Development. Got me a little confused ...

[jsmcortina]

I updated the Downloads page.

James

[Philip Lochner]

Have you tried the current release 3.3.1 ?

I looked at it James....

It does not offer barometric timing correction, thus I can not use it.

This is a very, very important feature to me. If others don't see why, I recon they simply have not encountered the barometric issues I have OR they simply don't realise/understand how "big a deal" this really is to run the engine optimised at all altitudes.

[jsmcortina]

What features do you think were being deleted?

James

[Philip Lochner]

What features do you think were being deleted?

James

I thought I read that Barometric timing correction was going to be deleted, but perhaps this does not apply to the regular Extra code since its never been there?

[scottmeister]

Here in South Eastern Australia we do quite a bit of 4x4 driving in the mountainous regions. Often, elevations in a single track will vary from 300 m to 1700 m ASL. For my setup with onboard MapDaddy Baro (see sig), I did try and use % baro but found that my engine had only a mild increase in VE with increasing altitude (due to exhaust back pressure reduction). Too much fuel was added, and timing was too retarded. This meant I have now reverted to speed density with fuel correction only; circa 2.5% additional fuel per 500 m altitude increase. I agree that it would be optimal to alter timing as a function of baro in a similar way. However, since my home altitude is sea level the problem you have is not such a big deal for me since I tune at maximum baro pressure. I imagine it would not be difficult to implement.

Cheers,
Scott

[jsmcortina]

The possibility of Barometric fuelling and timing correction being dropped scares me in a big way

Is it your challenge to make the most posts to this forums about a single issue in one day?

Also, how can baro timing be "dropped" when it hasn't been added?

James

[Philip Lochner]

The possibility of Barometric fuelling and timing correction being dropped scares me in a big way

Is it your challenge to make the most posts to this forums about a single issue in one day?

Also, how can baro timing be "dropped" when it hasn't been added?

James

I panicked. My sincere apology. Won't mention this ever again.

[Peter Florance]

A timing advance retard table vs Baro - similar to MAT based advance/retard.

I never could understand why, when travelling to the coast (dropping from 1500m / 4500ft) to sea level brought with it the onset of pinging, even at partial throttle despite stating out with timing map with 0 pinging. I thought that having an absolute pressure based timing map would eliminate altitude related pinging and that I would only have to tune the high kpa bins once I get to sea level. It is important to understand that I tuned the engine at 1500m where I live and can not tune bins higher than 85kpa because that is WOT at this altitude.

When you have 60kpa MAP at higher altitudes, is it not the same as having 60kpa MAP at sea level? After doing the sums as reported here (http://www.msextra.com/viewtopic.php?f= ... 20#p203139 - and assuming they are indeed correct) I now understand that 60kpa MAP at higher altitudes, may not be the same as having 60kpa at sea level by virtue of different cooling drops over the TB causing different air densities, which could also be contributing to different AFRs and ultimately different timing requirements. Combine this with the effect of changing back pressure at the exhaust....

Fortunately I realised that changing my trigger offset would move the entire table up or down and this is how I sorted the problem on the way to the coast - PC on the wife's lap

Further to the above posting, I have posted this (http://www.msextra.com/forums/viewtopic ... 34&t=52326) hoping to present a case as to why BOTH fuelling AND TIMING barometric correction is needed and should be offered by all FW versions of MS.

There is talk of timing correction in particular being dropped and I'm having a hard time explaining to the devs (and convincing them) why this feature is definitely needed. I was so convinced (and still am) that I need this feature that I PAID a code writer to add this feature for me!! I was having detonation issues on my high compression Rover V8 even when dropping from 1500meters to 1000m.

Phil, was this car dyno tuned for ignition timing? If so, what altitude?
Did the motor detonate at part load or full load?
Thanks

[Philip Lochner]

Phil, was this car dyno tuned for ignition timing? If so, what altitude?
Did the motor detonate at part load or full load?
Thanks

Peter, it was dyno tuned (on a load dyno) for timing at 1500m.

This is the interesting thing, it detonated at partial load around 60-70kpa (around 2600rpm) after having dropped from 1500m to ONLY 1000m!!! Stepping on the gas pushed the load up to beyond 85kpa where we entered conservative guestimates which turned out to be conservative enough to avoid detonation. Once I got to sea level I did tune those bins by "seat of pants" method (advance till ping, retard 4 degs.)

Now that I have Baro based timing correction (compliments of gslender) I no longer have this issue and no longer need to fiddle with MS settings as I travel along varying altitudes.

This issue is a particular problem on high compression normally aspirated engines which are subjected to varying altitudes - and ever more so if fuel octane is lowish. Someone who's engine was tuned at sea level may not ever know that his engine may have untapped reserves (with advanced timing) when going to higher elevations but most likely will ascribe diminished performance to altitude only (less dense air) - thus won't even understand / see the need for this feature.

[Peter Florance]

Phil, was this car dyno tuned for ignition timing? If so, what altitude?
Did the motor detonate at part load or full load?
Thanks

Peter, it was dyno tuned (on a load dyno) for timing at 1500m.

This is the interesting thing, it detonated at partial load around 60-70kpa (around 2600rpm) after having dropped from 1500m to ONLY 1000m!!! Stepping on the gas pushed the load up to beyond 85kpa where we entered conservative guestimates which turned out to be conservative enough to avoid detonation. Once I got to sea level I did tune those bins by "seat of pants" method (advance till ping, retard 4 degs.)

Now that I have Baro based timing correction (compliments of gslender) I no longer have this issue and no longer need to fiddle with MS settings as I travel along varying altitudes.

This issue is a particular problem on high compression normally aspirated engines which are subjected to varying altitudes - and ever more so if fuel octane is lowish. Someone who's engine was tuned at sea level may not ever know that his engine may have untapped reserves (with advanced timing) when going to higher elevations but most likely will ascribe diminished performance to altitude only (less dense air) - thus won't even understand / see the need for this feature.

Interesting...
I'm wondering whether cars should be tuned at two different altitudes or if this can be modeled somehow.

[Sellig78]

Hi

As posted before that matter is the cylinder pressure. If you're lived in high altitude the cylinder air mass filling will be less important than at sea altitude. So in order to avoid this a real engine load should be use in the spark table instead of a pure MAP. With this when you're travelling across different altitude the engine load vary and MS hit the good spark advance in the table (of course you need to set the table at sea level).

It's easy we have already the VE values.

Cheers

Gilles

[subwoofer]

Excuse me for barging in like this, but is there really a difference in cylinder filling for a given MAP depending on if it is caused by altitude or throttling? If tuned for max torque at all high MAP cells, will this deviate at altitude?

[racingmini_mtl]

I must add that I don't see how the pressure differential across the throttle has much to do with the pressure differential across the intake valve. So if you measure the intake manifold pressure correctly, you should have the correct cylinder filling regardless of baro pressure. The only difference would be the exhaust pressure difference but I thought that this is what is already taken into consideration.

Jean

[masterx81]

I've read somewhere that who drag at high altitudes uses higher compression ratios than at sea level.
In ms3 is possible with table blending, but would be nice a specific function for decrease timing based on the altitude, both on ms2 and ms3.

[E4ODnut]

Philip,
I, for one, read your post with great interest. And I will read it again, many times to make sure I understand what you are trying to convey.

Thanks for your point of view.

[Sellig78]

Hi,

The MAP sensor doesn't measure the engine load. It measure the difference of pressure before and after the TPS.
If you removed the TPS, the MAP will give close to the atmo pressure=WOT.
But even at WOT the engine load is not always 100%. If you look at you're look at your VE table you will see a maximun value for a fix MAP/RPM (if you have the AFR incorporated) witch correspond to the 100% engine load.
That's why a engine load/RPM ignition table is better, the spark advance depends only of the quantity of air inside the cylinder. So if you're travelling at different altitude the engine load will change and the spark advance too.

All OEM use this in their EMS for the spark table.

Cheers

[jsmcortina]

But even at WOT the engine load is not always 100%. If you look at you're look at your VE table you will see a maximun value for a fix MAP/RPM (if you have the AFR incorporated) witch correspond to the 100% engine load.
That's why a engine load/RPM ignition table is better, the spark advance depends only of the quantity of air inside the cylinder. So if you're travelling at different altitude the engine load will change and the spark advance too.

All OEM use this in their EMS for the spark table.

Cheers

I'm not seeing how the method you describe would give a different result from the existing MAP/RPM spark table ? Or rather, you didn't discuss how your "engine load" is determined.

James

[kjones6039]

The MAP sensor doesn't measure the engine load. It measure the difference of pressure before and after the TPS.

Huh? Is this correct? If so, how is the pressure measured on both sides of the Throttle Position Sensor? I thought I understood Manifold Absolute Pressure, but apparently I don't!

Did I just misunderstand this post? Maybe I shouldn't have sold that QuadraJet!

Ken