xr2wishy

iTrader: (2)

i have an issue with heat soak on my MAT sensor, it's really screwing with tuning.
i'm using an escort mat sensor, which is the same as a 2i one IIRC.
I know the FRST one is different and wondered if anyone using the FRST sensor is suffering heatsoak issues as i know it sits in a boss, then into the maniflod.
any help welcomed, otherwise i'll have to move the sensor into a inlet pipe further from the inlet manifold

cheers
sean

Karlos G

iTrader: (4)

I know you mentioned this before on my MS thread, but I still dont understand why you are getting heatsoak issues
There is a constant flow of fresh air going past that sensor so it should not really be getting hot enough for heatsoak to cause false readings, i've setup three RST's now using MS and none of them suffer heat soak issues, the last of which is running the latest MS Extra code too.

Are you 100% that the ACT (MAT) sensor is calibrated correctly, and is not faulty?
What readings did it give you when you set it up using a multimeter?

xr2wishy

iTrader: (2)

readings are correct as far as i can work out, it reads the same as my act meter from r&b when cold and when idling.
but as soon as i move off and the cooler starts to work, then the r&b one drops reading and the rst one doesn't.
Input Data Temp, degC Resistance
; 0 96000
; 20 37500
; 80 3750
tried with another rst sensor and still doing the same thing.
on efiextra.com (or whatever it's called) they say to alter the mat correction value and MAT correction table, but this doesn't help when the air temp is actually warmer, only helps when air temp is lower but sensor misreads due to heatsoak.

Karlos G

iTrader: (4)

Yeah they are correct readings.......... hmmmm that is strange?!
Why dont you just turn MAT correction off, then even if it is overeading once it hot it doesnt matter?
The MAT sensor is only used for warm up enrichments etc.. and it works fine from cold!
If you know your ACT's are not high on boost then there is no need to run MAT timing retard either.

xr2wishy

iTrader: (2)

i'm not sure on how to turn it off on the 2.1.1 code.
i'm not on about MAT based timing, there is a section on the code i'm using where MAT correction works with the ideal gas laws and then there is a MAT fuel correction table.
the CLT sensor does all the warmup enrichments.

Karlos G

iTrader: (4)

Sorry yes the CLT does do all the warm up!

The MAT retard and corection is under the Extended Tab, just set all the correction values to 0 and it will no longer effect anything.

xr2wishy

iTrader: (2)

sadly can't set it to 0, 50% is as low as it will go.
it may help though, i was trying to find a work around for this and have so far not got anywhere.
i could just stick my spare sensor in the engine bay just hanging on strut brace or whatever for the time being, can't be that far off.
failing that i'll get a boss to mount it in my charge carrier and wrap it in a load of ptfe to reduce metal to metal contact.
juat tio add for the time being i've had to switch on ego correction, which is somethign i didn't want to do as i tend to log most outings to solve a few issues.

Karlos G

iTrader: (4)

Yes you can mate! In the MAT Correction table you can set all the values to 0, i'll take a screen shot later if you cant find it to show you (on a different PC ATM).

xr2wishy

iTrader: (2)

nah you can't, seriously.
i can set the MAT correction to 0 yes, but the ideal gas law is followed by the code and due to the heatsoak in the MAT sensor it's making it lean out as it reads hotter.
law states that as air gets hotter the oxygen content will drop as molecules seperate more in a given volume, therefore the fuel content must drop in relation to this to retain good combustion.
it really is a ballache and i have it set at 50% aggression already, can't go lower as it won't allow any figure lower than 50%, won't allow 0% as it would ignore the ideal gas law completely and this can't happen apparantly.

Rick

what is your act sensor acutally reading?

xr2wishy

iTrader: (2)

depends, on idle anything upto 60 degrees, but my r&b one reads about the same as this, but as the car gets moving, say 30mph in fourth, then the r&b one will drop to less than 10 degrees, but the MAT sensor will still be high, and may drop to 20 after a while.
it is basically reading more than the r&b one in my charge carrier.

Rick

That sounds normal. At idle and light load there isn't enough airflow to completely eliminate the effect of radiation given of by the surrounding hot engine parts. When more loadis applied, you will find that the temperature will drop, at least initially if your intercooler is any good.

Whilst it might be diffucult to get the transfer function spot on for your particular install, it should never be so bad as to make the engine run hugely lean. Just how lean is it going? What is your idle afr after you have come to a stop before the "heat soak" takes effect?

Maintaining a constant AFR at idle in all conditions on a speed desnity system is difficult, that's why the OEMS use closed loop - have you tried this?

Rick.

xr2wishy

iTrader: (2)

basically i have an idle afr of 14.9, after a run, after being stopped for a little while it can creep up slowly.
the other day i switched engine off for a couple of minutes and then back on, inlet temp on both sensors read 50+degrees, the engine leaned out to 17.2 afr on idle, which made it really difficult to idle, but as the temp of the engine had dropped below 70 degrees, the closed loop wasn't active.
i find it needs to have at least 10% authority to combat this problem.
i am thinking of mounting the temp sensor in a hose in the charge route after the intercooler, this would eliminate most of the heatsok i would have thought, or even in the charge carrier pipe running over the rocker cover would be better than the heated inlet manifold.

Rick

14.9 idle before any heat soak effects is too lean really - you're fighting a loosing battle. You are not giving yourself any sort of cushion.

The amount of fuel injected is so small, it is very suceptable to small changes. Reducing ignition timing at idle so the engine needs more air will help stabalise it and make it less sensitive to temperature effects, but it can only help so much.

I would tune it to idle in the high 13's so that when it does get hot, it doesn't creep up to a very lean condition. Without closed loop you have very little hope of running it at 14.9 idle in all conditions. As an example, on MSD's live maps which don't use closed loop, the idle will be in high 13's normally to allow for pressure an temperature changes. There is no sense at all in trying to get it to idle any leaner. If you were tying to pass a modern MOT test, you'd have a CAT and closed loop.

With closed loop, the mixture should be tuned in open loop slightly richer than you want to run. The closed loop then trims off the excess fuel to give you your desired AFR. a 10% correction at small pulse widths isn't excessive. The closed loop is that good in MS2 that you can have a fuel map that is 50% out and it will still pinpoint your exact AFR, but obviously this is very bad practice.

Rick.

xr2wishy

iTrader: (2)

i've altered the EGO correction a little so it can play a part a little more and given full authority to the mat correction settings (i.e. 100%) and zero'd the mat correction table too.
richening the idle is possible though, always thought a lean idle is much better for economy, not a big issue though i guess, only a few digits to change to get it right.
only went for 14.9 as i had a carb turbo setup running previously and ran superb at that, minimal hesitation and kept fuel economy up.

i also raised the ve recods on idle so ego can swing from that to lean out when cold and richen up without maxing out to 15% which is what i've changed too.
my plan is to use my spare MAT sensor and just fit it in the engine bay, as i have no issues really on boost as the ACT's are quite cold.

cheers for the input, much appreciated.
sean

JesseT

Take a small NTC temperature sensor like this:

and glue it to the IC core close to the outlet. This will give quite good indication of inlet temperature with no delay or additional heat soak.

xr2wishy

iTrader: (2)

i've enriched the mixture on idle down to 14.3:1 AFR, and given ego correction it's job to sort it out a tad, seems to have brought inlet temps down a little, i'll be bringing timing down tomorrow when tinkering again, it's at 16 degrees advance on idle as it is, maybe down to 12 should make it more needy for airflow.

xr2wishy

iTrader: (2)

i've now taken a little timing out, just down to 14 degrees and seems a bit cooler, intake temps are rising much slower now.
sadly the side effect is more fuel consumption, but it has helped the issue a bit, although ego correction has to be kept on.