Baro and MAT ( IAT ) correction.

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Re: Baro and MAT correction.

Postby racingmini_mtl » Tue Mar 10, 2009 11:23 am

Philip Lochner wrote:
jsmcortina wrote:If the temp sensor is supposed to be installed in the manifold, wouldn't that temp drop already be allowed for?


All my logic tells me that it should be so. I remember seeing so many debates, as to whether the MAT sensor should be before or after the TB - and those are just the ones I did see - let alone the ones I did not see. Are we perhaps now arriving, with good reason, at the conclusion that the MAT sensor SHOULD be after the TB (thereby taking into account not only the temp before the TB but also the pressure drop over the TB and its resulting cooling/density effect) ?

The temperature should be measured as close to the cylinder as possible. I don't think there ever was a debate over that. The issue is that this causes heat soak in some cases which would prompt people to move it before the TB which is where the debate lies (at least that's my take on it).

Philip Lochner wrote:Now a new dilemma. I'm driving along at WOT with 100kpa (ie at sea level) and 50degC (122F) MAT (before and after the TB) and suddenly I lift my foot and MAP goes to 40kpa. IF the table I presented above is anywhere close, the inlet air temp after the TB at this new condition should very suddenly move to -74degC (-101F) - too fast for even an open element sensor to register besides being out of range most likely. This is distorting my brain... I MUST be missing something here...

The problem here is that table seems to attribute all of the pressure difference to temperature difference. I don't think that's correct. The lower pressure is due to volume variation from the piston "sucking" the air. The equation is: P1V1/T1 = P2V2/T2
so while there is probably a temperature variation, I'm sure it's far from what you show in the table above. Otherwise you'd see everyone suffering from TB icing at any ambient temperature.

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Re: Baro and MAT correction.

Postby jsmcortina » Tue Mar 10, 2009 11:43 am

I have two temp sensors on my MS1 install, but only one is wired. I presently use the one right at the front of the car below the radiator. The other is in the steel plenum. When I get chance I'll hook it up and do some logs.

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Re: Baro and MAT correction.

Postby pigga » Tue Mar 10, 2009 1:37 pm

Hi.
In my humble opinion the thin wires should prevent the sensor from "heat soaking". The only Thing that could cause wrong measurement would be the infrared radiation inside of the manifold!? However...I think you ALWAYS have measurment errors.
The reason: You NEVER measure the Temperature at the inlet valve/in the combustion chamber. There is alwas some way the Inlet air has to take between sensor and combustion chamber.
I suppose, that a heated up die-cast manifold will heat up the air (especially at low flow speed ot the inlet air) more than a manifold made of plastics does? Well, thats just an assumption.
In my car I noticed this effect very significant after a traffic jam: The stock MAT Sensor is fitted near to the filter element (far away from the throttle/manifold). When the engine is nerly glowing (e.g. traffic jam) and I start off, the car runs far too rich. (This could be caused by an additional heatup of the inlet air that the mat sensor doesn't notice). After a few Kilometers the Air seems to have cooled down the manifold so that I get normal AFR values a usual.
Well, as I said: Just my personal assumption.

Thomas
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Re: Baro and MAT correction.

Postby landybehr » Tue Mar 10, 2009 2:28 pm

Hi,
I realize my problem is too little knowledge to do it right but not enough (I did not say "not too little" ;) ) knowledge just to shut up. Seems to bring me into trouble all time. So if it´s nonsense, just tell me and I´ll be quiet :)

Does it really make a difference where the IAT sensor is put ? I mean it makes a difference when msq´s from different people are shared by setups which differ in the sensor location.
But we have a) temp. of ambient air and b) temp. of the air entering the cylinder.
AFAICS the temperature drop of the air over the TP is predictable ? So in the end it does not matter which´s sensor´s location leads to a tune of the MAT correction table ?

And, can I assess in how much measuring the air just behind the throttle plate reflects the air entering the cylinder ?
I think the amount of air is small in low-MAP conditions, I´ve been astonished that (if the TP is 100% closed and really tight) the engine mainly breathes through a 3mm bypass hole unless there are air leaks or piston blow by fills the cylinder again (if IAC is fully closed and a certain set-screw were 100% closed - which it isn´t). So could the speed of the air entering the cylinder be rather slow and there be more heat than at WOT when the warmer (less pressure-drop-temp-reduction) air runs right into the cylinder ??
Last edited by landybehr on Tue Mar 10, 2009 2:40 pm, edited 1 time in total.
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Re: Baro and MAT correction.

Postby landybehr » Tue Mar 10, 2009 2:33 pm

Besides all that - you cannot be aware of how happy this thread made me again. I too had so much trouble with the AFR´s that changed "unpredictably" and MLV once making the idle-VE´s lean, once making them rich. I saw changes of AFR from 13 up to 15 !
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Re: Baro and MAT correction.

Postby KaPower » Tue Mar 10, 2009 8:19 pm

Why does this mat correction issue effect large injector setups worse then smaller injector setups? The only explanation I can think of is pulsewidth control issues, or injector control issues...
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Re: Baro and MAT correction.

Postby vinister » Wed Mar 11, 2009 12:15 am

Obviously the smaller your idle PW the more your setup being affected, because there is less and less resolution for PW.

I agree that the sensor position is not all that crucial. That is what the MAT correction table is for, and I find it works very well. I would not bolt a sensor directly to a cast manifold without an insulator, and try to keep it away from the exhaust. Expanding the MAT table is a good idea, some more tuning points would be very welcome.

I also throw in my vote for WUE to be a table of CLT vs RPM, or at least have some rpm corrections.
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Re: Baro and MAT correction.

Postby GintsK » Wed Mar 11, 2009 1:16 am

I suggest to implement 3D MAT correction table. Load/Rpms/correction factor. Small table 5x5 or so.
At lower loads (low air flow) more heat soaking affects final calculation. But even at same rpms but higher load signal from air temperature sensor is more reliable.

I notice interesting feature on one of famous Aussie ECUs. They have a proportional table for IAT calculation from CLT and IAT signals. Also 3D. So at idle air temperature can be calculated lets say 100% from CLT, but as load goes higher more and more IAT signal can be taken for calculation.

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Re: Baro and MAT correction.

Postby evo828 » Wed Mar 11, 2009 2:47 am

I've seen those 3D IAC comp tables as well - but usually they seem to be flat (kpa wise) - see an exmaple.

http://i548.photobucket.com/albums/ii35 ... ATcomp.jpg
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Re: Baro and MAT correction.

Postby GintsK » Wed Mar 11, 2009 4:04 am

Problem with 3d will be that 95% of users will never touch this table. Solution can be some good start maps or clear instructions for tuning this table.
I suppose most of users didn't touch curent MAT correction too.
Some of my instalations:
VW TBI, VW 16V 60-2,
BMW M50 COPs 60-2, BMW M20 and M50 ITBs as Alpha-N, BMW M20 turbo Wasted spark
Opel 20XE Wasted Alpha-N with ITBs
Audi 10VT Audi20V
MR2 3S-GE.............
and over 100 tuned
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Re: Baro and MAT correction.

Postby jsmcortina » Wed Mar 11, 2009 5:06 am

GintsK wrote:Solution can be some good start maps

Agreed. Once the next beta is out people can try out the scaling factor and see if it is helpful and whether there is a one value that helps everyone.

On the CLT/MAT table - that's something I mentioned a few days ago. This won't go into 2.1.0, but possibly a later MS2/Extra code series.

James
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Re: Baro and MAT correction.

Postby Philip Lochner » Wed Mar 11, 2009 5:13 am

jsmcortina wrote:Once the next beta is out


Not rushing James, but any idea when that is likely to be +- ?

I for one am awaiting this code with great anticpation :D
Kind regards
Philip
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Re: Baro and MAT correction.

Postby landybehr » Wed Mar 11, 2009 8:23 am

GintsK wrote:I suppose most of users didn't touch curent MAT correction too.


Most likely. I am one of them. But seems like I heavily underrated the MAT function. Reading this thread and figuring how big an impact the MAT has it is remarkable that "we" did not touch MAT correction.

I am asking myself if :

a) the MAT is not important for everyone, as some setups just do fine without (in which case it would be very interesting - why?), or:
b) people had their closed loop EGO correction do the job and mask the need for MAT correction. Which must have been insufficient sometimes (if fuel (e.g. with differing ethanol content) changes etc. the AFR might change and if that change coincides with MAT-dependent change I can assume the controller authority not always was set high enough. Therefore:
c) I too think it is desirable to have all the corrections "spot on" so that Philip´s AFR-error-gauge will not move :) Good news in this thread that some have achieved this when bothering with MAT correction already.
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Re: Baro and MAT correction.

Postby arlo#1 » Wed Mar 11, 2009 9:01 am

jsmcortina wrote:
GintsK wrote:Solution can be some good start maps

Agreed. Once the next beta is out people can try out the scaling factor and see if it is helpful and whether there is a one value that helps everyone.

On the CLT/MAT table - that's something I mentioned a few days ago. This won't go into 2.1.0, but possibly a later MS2/Extra code series.

James

I am very excited. I was wondering if it will be worth trying to have a rpm vs temp corection as well or do you think the way the calculations are it should work perfact once you have the right amount of scaling/mat athority? I am interested to see if there is a common place people will end up scaling to as well.
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Re: Baro and MAT correction.

Postby landybehr » Sun Mar 22, 2009 9:32 am

Hi,

someone on a german forum gave me a smart hint, I think.
Is it possible that the sensor calibration table follows a different line than the MAT correction table as we are inclined to design it (temp spacing) ?

Maybe it is just impossible to make a good default value, because we all choose different temp.spacing on the 3-point calibration table ?
Apart from that, my roughly made values are not very far away from those of Philip

Thinking about this I wonder which points of temperature I should have chosen for the 3-point calibration table.
The sensor I use is a Bosch with calibration table: http://www.bosch-motorsport.com/pdf/sen ... _M12-L.pdf
I took -40°C, 0°C and 82°C, but possibly changing the "0°C" for another point would have made MS thinking more in a "linear" fashion than it does now for me ??? :)

I do not "feel" all that to be a problem for the WUE curve, but this has 10 points to choose so the WUE curve can be made to follow the sensor-calibration curve easily.

FWIIW ;)
But I managed so far to get the idle-AFR´s fluctuating from 13.6-14.1 rather than 13.6-15.3 as before. MLV will change the idle-VE (around 60ies) by just "1" now, but still will now add "1", next time subtract "1".

Another thing I wonder about is whether the idle speed after warm startup could be improved by only the MAT correction. When the warm engine stood for some, say 15mins and is restarted, the idle speed will be 50-100 lower than when the car has been driven again and idles several minutes later.
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Re: Baro and MAT correction.

Postby zmanco » Fri Oct 30, 2009 2:01 pm

I had missed this thread earlier this year, but thanks to Philip just saw it. I live in Colorado at 6200 ft and regularly drive down to the Denver area at ~5300 feet. I have been using % Baro since I took a drive out to California a year ago and found that my tune was more and more off the lower I went. I only wish I had been using it BEFORE the trip so I would have had the chance to gather more data.

Nonetheless, I found that as I went down in altitude that I needed to increase VE values to hit target AFRs. This is the opposite of the default Baro correction setting in MS2/E. Given I was tuned for 81 kPa as my baseline and didn't want to retune, I found that I was able to correct to a reasonable level by changing the Baro correction values to 57 and 65 respectively.

Capture9-18-2009-2.18.53 PM10-30-2009-2.42.10 PM cropped.jpg


The net effect was that with a good tune at 81 kPa, the % Baro correction increased VE by 11.3% (instead of decreasing 8.2%) and got reasonably close to target AFRs without too much EGO. Again, keep in mind, at that time I was not running % Baro so I was beginning to richen the target AFRs at MAP levels around 60 kPa, so don't have a good feeling if the values for % Baro correction were optimum (I don't think they were).

Since then I've played around with the % Baro correction values but it's hard since it's a trial and error approach in Excel. I really like Philip's suggestion to in effect negate the % Baro values by using 100 and 0 and instead use the barometric correction table for all of the correction. That will make it much easier to adjust when tuning at a new altitude. I have made the changes to do that, along with adjusting my VE table to reference 100% at sea level (to make it easier to share with others), and will begin to try that out over the weekend as the snow clears. Weather willing, I'm supposed to go on a drive up into the high country >9k ft on Sunday so will hopefully get some more real world data to share.

As I think James said, perhaps we will find that there is a set of default values for the Baro Correction table that is close enough to use as a default for most people.

I'll make another post with some thoughts on MAT correction later.

EDIT: I should have added that I am running with a second MAP sensor and the engine is now turbo'd.
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Re: Baro and MAT correction.

Postby hassmaschine » Sat Oct 31, 2009 9:31 am

landybehr wrote:FWIIW ;)
But I managed so far to get the idle-AFR´s fluctuating from 13.6-14.1 rather than 13.6-15.3 as before. MLV will change the idle-VE (around 60ies) by just "1" now, but still will now add "1", next time subtract "1".

Another thing I wonder about is whether the idle speed after warm startup could be improved by only the MAT correction. When the warm engine stood for some, say 15mins and is restarted, the idle speed will be 50-100 lower than when the car has been driven again and idles several minutes later.


if a change of 1 in your VE table makes the AFR change from 13.6-14.1, the issue may be the resolution of your VE table rather than randomness or MAT measuring error. There are some tricks to get more resolution at idle, like rescaling your REQ_FUEL (making it smaller) and enabling multiply map if it's disabled.
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Re: Baro and MAT correction.

Postby zmanco » Tue Nov 03, 2009 9:09 pm

I took a long drive up into the mountains this weekend. Barometric pressure ranged from 83 kPa down to 73. To recap, I had set the Barometric Correction using Sensor Calibration as Philip had suggested so that there was no correction from it. I then used the barometric correction table exclusively to manage it. Unfortunately I forgot to transfer the msq file to my work laptop before I left on this trip, but I think the table ranged roughly from 0% at 100 kPa down to -33% at 60kPa IIRC. This is based on the drive this weekend up into the mountains and also the drive I took last year down to sea level in California.

I'll post a copy of the table I settled on when I get back this weekend and will be curious if this table is accurate for others.
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Re: Baro and MAT correction.

Postby Philip Lochner » Fri Jan 29, 2010 12:34 am

Earlier in this thread we were talking about the effect of pressure drop over the throttle plates on MAT.

Just for kicks, I installed the IAT sensor on my V12 cobra inside the manifold, after the throttle plates, but directly in line of the air flow through the throttle plates. The idea was to be sure that any air flow through the throttles would be sensed by the sensor and report it.

It is interesting to note that MAT stays rather constant regardless of throttle position. In fact, I've noticed MAT INCREASING with low MAP values. That seems to indicate that the sensor is heated up more by infra-red radiation from the surrounding manifold than the cooling effect of low density and low volume air flow at low MAP values. As I go towards WOT the MAT value would DEcrease by 3 - 5*C.

I have also noticed that MAT values are significantly higher with the sensor in the manifold. Eg, on the Jag XJS I typically get MAT values between 25 - 35*C whereas on the Cobra (also fitted with cold air intakes) I get 55- 65*C.
Kind regards
Philip
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Re: Baro and MAT correction.

Postby wes kiser » Fri Jan 29, 2010 6:48 pm

Philip Lochner wrote:Earlier in this thread we were talking about the effect of pressure drop over the throttle plates on MAT.

Just for kicks, I installed the IAT sensor on my V12 cobra inside the manifold, after the throttle plates, but directly in line of the air flow through the throttle plates. The idea was to be sure that any air flow through the throttles would be sensed by the sensor and report it.

It is interesting to note that MAT stays rather constant regardless of throttle position. In fact, I've noticed MAT INCREASING with low MAP values. That seems to indicate that the sensor is heated up more by infra-red radiation from the surrounding manifold than the cooling effect of low density and low volume air flow at low MAP values. As I go towards WOT the MAT value would DEcrease by 3 - 5*C.

I have also noticed that MAT values are significantly higher with the sensor in the manifold. Eg, on the Jag XJS I typically get MAT values between 25 - 35*C whereas on the Cobra (also fitted with cold air intakes) I get 55- 65*C.


Same thing I have observed on manifold mounted MAT sensors.
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