MAT location question

Converting To Delco ECU From Carby Or Other Injection Systems
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delcowizzid
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Re: MAT location question

Post by delcowizzid »

I would move it to a similar to stock location and then tune the tables to suit engine reversion characteristics of your engine
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VK_3800
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Re: MAT location question

Post by VK_3800 »

With my conversion I put the sensor in the manifold runner as close to the head as I could, but still had some big issues due to the cold air intake and different characteristics of the manifold compared to the VN setup. I'd get heat soak from idling for a bit which would give very high air temps, then as soon as you drive down the road in winter the cold air would dramatically drop it almost immediately whereas it seems that the original tune was designed for a more gradual change.

Unfortunately it seems to be just trial and error with a lot of cold to hot driving and logging to get it right, but it did seem to help to get a base tune that works at warmed-up temperatures (not heat soaked but operating temp) and go from there, something you can readily reproduce that represents a reasonably 'normal' driving situation. The coolant temp contribution table can be quite sensitive to changes but once you start making progress from the base temperature it gets easier to trim. You really need a wideband oxygen sensor and spend a bit of time comparing logs against coolant and charge temps. Make sure you have a reasonable tune at the base/operating temp before you even start trying to change this or it will just frustrate you.

Having said all that if you're only getting 10 degree differences you probably will struggle to get a good result, if its possible to move it that would be my first step.
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Re: MAT location question

Post by Hof360 »

Hi All,
bit of an update,

I moved my MAT to the intake manifold, I now see up to 78 deg C.
So now it has a more realistic range.

I then changed Charge temp Inverse table and %coolant contribution back to standard 12p tables.

I Chased and altered the Inverse table on warm up to match commanded AFR and wideband, which seemed to respond well.

I now have a lean condition on restart after about a 20 - 30 min cooldown period.
I will log from cold again after 24hrs and then from the restart, hopefully this will give me some insight.

Luke
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Re: MAT location question

Post by vlad01 »

Where abouts did you put it in the manifold?

This problem of lean hot restart is a common issue. It can be somewhat tuned out but because it's fundamentally effecting the MAT sensor readings with heat soak and not actual air temps so trying to tune it out is like trying to tune the main fueling with a warm up table as an example, can sort of work but it's basing calibration on the wrong input data so to speak.


The factory actually fudged the inverse temp term on the v6 BLCD tune. Open that up and have a look at how they did it. It seems really botched but actually helps fudge the hot lean restart issue. I have had reasonable success on another engine of the same where I worked with Dylan to make a new charge temp table and made the inverse temp linear again. It was better but still impossible to get rid of it completely as the sensor was right at the bottom of the runner and would heat up a lot after shut down.

This is why I mentioned earlier that moving the MAT sensor to the plenum can help a lot. Also what is worth doing is having the sensor mounted in phenolic as we did on a v6 race engine, it had a spacer so it was mounted in the spacer insulating it from the alloy. After that the cold to hot AFRs and even heat soak restarts were bang on once we made the inverse temp linear, because the MAT was left alone to measure air temps and not heat soak anywhere as much. It could be that you can make a phenolic spacer for the 4 barrel TB and drill and tap into that and get the sensor to poke out in the incoming air stream.


Is your intake port injection of TBI?. Can you post some pic of its placement?
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delcowizzid
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Re: MAT location question

Post by delcowizzid »

Check the after start air fuel ratio for the engine temp you are restarting at you can offset it and delay how fast it decays out
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Re: MAT location question

Post by Hof360 »

Where abouts did you put it in the manifold?
at the rear where runners 7 & 8 meet and there was a vacuum takeoff (that I relocated)

This is why I mentioned earlier that moving the MAT sensor to the plenum can help a lot
It seems as though there is always going to be a trade off with the placement (heatsoak vs accurate measurement at running temp), so I hoped that where I have it now which is technically the plenum of the 4 barrel manifold will be the best of both worlds as it is not right at the base of the runner.

It could be that you can make a phenolic spacer for the 4 barrel TB and drill and tap into that and get the sensor to poke out in the incoming air stream.

I already have a phenolic spacer, but have not yet drilled and tapped for a sensor still an option however.

Is your intake port injection of TBI?.
port

After that the cold to hot AFRs and even heat soak restarts were bang on once we made the inverse temp linear
having adjusted the inverse table initially from cold, it is now more linear up to running temp.


delcowizzid wrote:Check the after start air fuel ratio for the engine temp you are restarting at you can offset it and delay how fast it decays out
Im not sure how long the decay is at the moment but it seems to stay lean for too long to utilize this function, I will look into this also.


Cheers
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Re: MAT location question

Post by vlad01 »

Ok, so sounds like we are on the right track.

when you do a hot restart, take note or better yet log the calculated charge temp. You can add that data plot in the monitor by right clicking and adding it, then log it as you start the engine and let everything normalized.

We should see a peak charge temp during this period which will give you an idea on what points on the inverse need tweaking. It can be fudged in the inverse as the factory did on the V6 here. So under normal running conditions it's never reached but only does when a heat soak restart happens. The normal thing for the V6 to do it go really rich on a hot restart, the reason is the fudge from factory was overly aggressive, but making it linear makes it got way over the other side and become really lean, like 16:1 lean. Where as target might be 13-14. For the fudged v6 factory it typically goes around 11 if i recall, but making it closer to linear but still roll over around the 100c mark does the trick

See this screen shot of BLCD implantation of the inverse temp the factory did.
inverse temp.PNG
inverse temp.PNG (67.46 KiB) Viewed 4192 times
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