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Steve

Charge Temp Correction tuning.

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It seem like a good option to have and i think i will try it out when i get my car back together. It will need a retune so i might just as well try CTC.

However! How would you go about tuning it. Thinking about it i forsee ALOT of tail chasing trying to dial it in. As i see it if you dont have a good CTC you will not be able to dail in a good fueltable, but then again, if you dont have a good fueltable you wont be able to dail in CTC. As i read it the only temp CTC does not do anything is at 18 degrees so to avoid it seems impossible.

Only way i can see is if you tune the fueltable with AIT correction and coolant temp correction first and THEN got to CTC. But then again this is double work and it wouldnt be perfect either.

Im sure im missing something so please fill me in.

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Hi, by using this method it is a more accurate way to tune.

I agree it can be a lot more time consuming however more accurate.

Previously we had just straight air temp inputs and engine coolant temp inputs.

This is fine and with the available trim tables can still lead to very accurate tuning.

However by using the Charge Temp Correction method the ECU is calculating the desired fuel required to make the AFR/LAMBDA levels more accurate again.

For example the incoming air temp is measured by the IAT sensor, it measures 18 degrees celcius, however the engine coolant is measured by the ECT sensor and it is 80 degrees celcius.

So therefore what is the true air temp temperature and therefore DENSITY.

By using the Charge TEMP """APPROXIMATION""" table the ECU can work out the approx. air temp inside the engine to include latent heating via the heated engine effecting the air temp and density.

As the help file states, by using certain values you can make the fuel table favour the IAT sensor or the ECT sensor to effect the fueling.

So for example you may wish to use the values favouring the ect at low engine speeds which equates to slower air speed which can cause higher heat soak to the incoming air charge.

At high rpm and road speed you may trend your table towards the IAT sensor as the air temp will be less likely to be influenced by latent heat build up and the engine temp itself should be at a constant, therefore leading to a cooler and more dense air charge.

You can also use your IAT and ECT correction tables to fine tune the Charge Temp Estimation table.

Just remember what the name states ""ESTIMATION"" table.

I hope this clears things a little for you.

Regards

Dave.

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I hope this clears things a little for you.

Not really Dave. Appreciate the the effort though.

Where/how do you start if you start building a map from scratch? Do you build a map the "regular" way with AIT comp and finish the fueltable first THEN turn of AITC and CTC on. Then try to get the AFR to match the target with the CTC table? Or is there another aproach to it?

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Hi,

as I stated this is a more complex way to tune, however more accurate.

To be honest I haven't tuned with this new method as yet on the i SERIES, I have still been using IAT and ECT until I get some time to do some test tuning with the Charge temp correction table.

However the concept does seem to be very similar to Autronics version of Charge temp tuning.

With Autronic software they had a default table that worked fairly well straight up and you fine tuned from there.

If it was my own car or the customer wasn't in a hurry for his car to be returned quickly I would prefer to tune using the Charge Temp Estimate Table and use the IAT and ECT to fine tune if required.

Simon or ASHLEY may want to add their comments regarding this tuning method, to clear things up.

Regards

Dave.

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Yeah, a predefined CTC table is something that would make it easier. Actually thats what i would have expected with a feature like this.

Now you have two unknowns with one result. Its a lottery to get the two unknowns right.

Well Ash and/or Simon, you`re up!

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Hi Steve

Its early days on this, so we don't have a lot feedback on the numbers that are working well.

It will of course vary depending on engine and fuel type.

Over time as we get some more engines through and complete testing we will build the base files up.

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Both Simon and Dave are spot on with their responses, actually Dave's insight into the functionality of the charge temp estimate tables is about the most simplictic and informative I've seen. It's quite hard to appreciate this if you haven't seen it before, however the extra effort can prove to be quite rewarding. Believe me, this is a huge effort which has great promise.

I would echo Simon's response by asking for added time to build generic table data to aid your transition. However, as Dave indicated you can easily turn the feature off by zero-ing the table. I can tell you that Autronic had extensive research into this particular feature prior to making it available and it worked really well as it complimented their VE model quite well. However, their extensive research allowed them to offer tailored customer support for different engine platforms.

For a millisecond based model this may seem like just an addition but it's quite a huge step as far as the model goes so I would ask that you exercise a little added patience so that the support team can better facilitate the transition for users who may need assistance with this new functionality.

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I'm preparing to start using the Charge Temp Approximation table with my new engine setup, and I'm wanting to get some clarification around my thinking.

In earlier posts, Dave states that if the table is Zero'd then it will turn off the function. Reading the help file, my understanding is that a zero in the table will force the charge temperature parameter to read the same as the IAT, then in that case I would have thought the following from the help file would still be in effect:

· If the Charge Temperature is below 18°C the ECU will increase the injector pulse-width, leading to increased fuel delivery to the engine.

· If the Charge Temperature is above 18°C the ECU will decrease the injector pulse-width, leading to decreased fuel delivery to the engine.

Is the support team able to share the charge temp calculation equation, or advise how much the pulse width is changed as the charge temp moves either side of 18deg?

This would be helpful so I can build my initial Charge Temp Approximation Table knowing how the engine used to respond with normal ECT and IAT corrections.

Thanks

Jason

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Charge temperature is used in the air density estimation in the fuel equation. As there is no sensor right at the intake port and due to air temperature changes between the IAT sensor and port, an estimation is needed of the temperature at the port.

When charge temperature is turned on for use in the fuel equation, it is always used. Charge temperature correction is not turned off by putting zeros in the table. A zero in the table means charge temperature will match IAT. A 100% means charge temperature will match ECT.

The assumption is that at low air flows, the air temperature is closer to ECT due to being heated by the port and intake runner. At high air speeds, the air temperature is closer to IAT.

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Thanks, that's what I had gathered from the existing documentation.

Did some logging today and noticed that the charge temp estimate is locked at 18deg when the function is disabled so I guess that's a constant for the equation.

Would still be nice to have a rough idea of how much the injector puslsewidth is impacted given a 10deg change in charge temp estimate.

eg with Autronic, there's approx. 3.2% change in injection time per 10deg change in charge temp estimate, with their formula being Charge temp = ((water temp – Air temp) * charge EST) + Air temp

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I was doing some initial experimentation with the Charge Temp Correction (CTC) feature on my (Blue) Storm. 

First, when I turned CTC "on", I noticed there were values in the Charge Temp Approximation Table which looked like a sensible starting point.

Then, on a graph, I logged the ECT, IAT, and Charge Temp.  However, what I noticed is that the logged Charge Temp with CTC "on" was the same as with it "off".  Turning it on or off made no difference in how the Charge Temp value responded to RPM and MGP.

I thought maybe with CTC turned off, it used some kind of default response.  So with CTC turned on, I modified some values in the Approximation table.  As expected, changing these values caused the Charge Temp to change as well.  However, when I turned CTC "off" the Charge Temp response stayed the same as if it were on.

So what I am experiencing is that it seems like CTC is always active, whether it's turned on or off.  But when it's on, I can edit the approximation table.  when it's off, the table is blank.

Am I misinterpreting what I'm seeing, or is there something wrong?

Edited by PitBull

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Okay, I understand that.

Can you clarify for me -- is CTC a better way for the Link to have a Charge Temperature value for it's fueling equation?  As in, if it's turned off, it uses another less-accurate method (i.e. the IAT value)?  Or if CTC is turned off, is there no charge temp correction going on except for what's in the Warmup Enrichment and IAT Trim tables?

Edited by PitBull

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If using traditional fuel equation mode then using CTC will usually give a more accurate/consistent tune over a wider range of operating conditions.  The downside is it is more difficult to correctly tune the CTC table.  Usually the best way to tune it is on a dyno & while keeping water temp relatively constant, you vary the air temp.  You can usually do this just with simple ducting etc so that the intake temporarily sucks hot air from say behind the radiator or off exhaust manifold etc. 

If CTC is turned off then you will use the IAT correction table to do most of the correction. 

Edited by Adamw

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With CTC turned off, is there some form of temperature compensation going on in the fuel equation and the IAT trim and Warmup enrichment are tweaking that?  Or do those tables represent the only compensation when CTC is off?  So if they are zero, there is essentially no compensation for charge temperature going on?

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In traditional mode there are no background compensations like modelled mode has. So with ctc off and iat and wue zeroed there will be no temperature based fuel trims.

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Hey here's an idea for tuning CTC, basically hijacking the mixture map function by making an overlay fuel table that has ECT and IAT as its axes.

Get your engine tuned "right" at a given temperature that you can keep it stable at then turn off corrections.

Then datalog some driving where you get fluctuations in ECT and IAT with closed loop turned off.

Then create an overlay fuel table with the axes set to IAT and ECT, set all values to 100.

Then use the mixture map function to load the datalog results and build the fuel table, filter the results so its only reading one rpm region say 250rpm either side of 3500rpm

then when you update mixture map it'll adjust the values up and down by a % needed to reach goal AFR, you may see a trend here that can be used to fill in your CTC table

Then keep changing rpm and resetting mixture map values to 100 to find values for each rpm range

(Havent tested this myself, but seems a good way to gather data over a long span of time to find the trends)

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