Speed Density OS - made "Cylinder Charge Temperature" Disable

[TXjeepTJ]

I tuned my friends car and switched it to 1bar SD OS, which I noticed it disabled the cylinder charge temperature

I've been having issues tuning my car, which has a 2bar SD OS, and I noticed that my cylinder charge temperature is still enabled. Is this because I'm boosted and his was just 1bar SD?

I'm wondering if the issues I'm having is caused by this being enabled. I tune the VE table and by the time I'm about an hour in, all my fueling goes super lean before I made any corrections


Can I disabled cylinder charge temperature if I'm boosted?

[lukearmstrong1990]

I would recommend disabling that with a boosted car. I personally do it on all boosted gen 3 SD cars, but its particularly important with PD blown cars that have the IAT sensor in the manifold

[scoob8000]

You are talking cylinder charge temp complex model, correct? If so disabling it just banks all the chips on the IAT sensor so to speak. Where in a boosted app, folks will move to after the SC or turbo to get a more accurate reading.

[mowton]

The only time you would disable this function (actually forcing to 100% IAT) is when you upgraded an NA setup to a roots style blower (per luke above) and moved the IAT to under the lid or post boost. Then it is all IAT as temp equals the boosted value. Centrifical Blowers (Procharger, ECS) still use the function as the boosted air is still measured at the MAF and needs to journey to the cylinder.....

Ed M

[kingtal0n]

I thought this was just IAT vs CTS for fuel bias....

[mowton]

I thought this was just IAT vs CTS for fuel bias....

To help develop cylinder charge temp more accurately which is a major component of the Injector Pulse Width calculation....so yes, it is fuel based

Ed M

[kingtal0n]

I always disable this for typical forced induction applications because you can get a very accurate IAT in the pre-throttle body pipe using a quality IAT sensor and do not want coolant temp factoring into the IAT. Its one less influencial variable to chase. Presuming the iat sensor works accurately and is responsive I see no reason to include cts into the equation. But I wonder why when using the MAF they enabled this feature when the iat is so far from the heat soaking manifold.

also as to "major part of injector pulse" isn't the cts bias only ~0.70-1.5% global fuel adjustment during acceptable temp rise as 230*F coolant for example?

[mowton]

I always disable this for typical forced induction applications because you can get a very accurate IAT in the pre-throttle body pipe using a quality IAT sensor and do not want coolant temp factoring into the IAT. Its one less influencial variable to chase. Presuming the iat sensor works accurately and is responsive I see no reason to include cts into the equation. But I wonder why when using the MAF they enabled this feature when the iat is so far from the heat soaking manifold.

also as to "major part of injector pulse" isn't the cts bias only ~0.70-1.5% global fuel adjustment during acceptable temp rise as 230*F coolant for example?

As the air travels from the MAF where the IAT is normally loacated to the cylinder, the ECT will still have an influence on the final temp as it journeys towards the cylinder and velocity will play a role in determining the amount of influence regardless if its NA or running a Centrifical FI. To this I keep the function enabled as the OEM intended. I do not see any viable reason why, if the air has been reported previously and there is a function that the OEM selected to "fine tune" the charge temp as it was traveling into the cylinder, and I have not altered that physical setup why I would disable that (sorry that is a rather long sentence :-)). Yes, with a PD blower and relocated IAT sesnor after the screws, I can see the need for disabling.

As far as the term "major part" I was more alluding to the overall charge temperature does play a role in calculatiing the fuel mass based on the airmass....again, I assume somwhat significant or the OEM wouldn't have developed this complex model in the first place.

JMHO

Ed M

[kingtal0n]

To this I keep the function enabled as the OEM intended. I do not see any viable reason why, if the air has been reported previously and there is a function that the OEM selected to "fine tune" the charge temp as it was traveling into the cylinder, and I have not altered that physical setup why I would disable that (sorry that is a rather long sentence :-)). Yes, with a PD blower and relocated IAT sesnor after the screws, I can see the need for disabling.

As far as the term "major part" I was more alluding to the overall charge temperature does play a role in calculatiing the fuel mass based on the airmass....again, I assume somwhat significant or the OEM wouldn't have developed this complex model in the first place.

JMHO

Ed M

I do enjoy reading and appreciate your knowledge in this matter. It was/is my simple understanding of the nature of this system that if any air-charge heating occurs along the air path, that air density drops (or is reported as dropping) and that means fuel is being subtracted (the logic of less dense air). Apparently it depends on which OEM because I did look through HPtuners OEM settings and notice they are adding fuel (if I read correctly) when temperatures increase even though density is going down, I believe this is for additional engine-cooling and detonation prevention of hotter air going into an engine.

That said a couple things still don't quite add up for me yet. I am not necessarily hoping you have an answer, just throwing this out there.

A. The maf sensor measures accurately the fuel required for an engine, that is basically the 1 major thing it does better than any MAP sensor because hot-wires measure density directly and negate the need for IAT. Therefore I don't usually see IAT related corrections on MAF equipped vehicles. Now, taking into account the fact these engines equip both MAP and MAF it makes me wonder at the function of the IAT beyond calculating air-mass: it seems to be there for other reasons, i.e. detonation resistance and engine cooling provided by extra fuel when things get too hot.

B. the coolant temperature of an engine once warmed to thermostat temp is relatively stable and unchanging, or at least should be, in a majority of applications. That means any influence the CTS has on the IAT calculation (or fuel being added for the purpose of high IAT) is going to be relatively constant also. Say an engine sitting at 200*F is always at 200*F that means CTS is always 200*F and the % adjustment will be continuous. It could be "tuned for" or "tuned out" in other ways and the CTS would never know the difference because it doesn't move. Furthermore, the CTS tends to lag behind engine warming, full throttle performance situations. For example the CTS is reporting 200*F and you make a WOT pass, then several seconds later the CTS begins to climb as a result (after the run is already done). This sort of "after thought" behavior isn't going to provide any fuel cushion for the engine when it maybe could have used it.

C. as we tune the engine (ourselves) we see many OEM, PCM/ECU related features which are routinely disabled or re-configured to match our tuning styles. For example the stall saver feature and DFCO spring to mind. It is commonly asserted that these features are merely an 'extra layer of behavior' that was intended for the majority of untouched applications, where individuals are driving their vehicles without tuning them and need that extra bit of compliance in the system to keep it happy at all times. Once we understand what they do and are comfortable with disabling them or re-configuring them it is often done so. This is one such feature that I feel could be done without, for it seems to serve merely to skew only slightly the fueling of an engine which is often been radically adjusted by modifications and no longer follows to suit the factory methods. For example turbo LS applications often run 11 to 10:1 a/f ratios and have much less timing advance than the OEM engine does, so depending on the OEM engine to discern the fuel or timing requirements based on CTS settings is only viable when we are the ones setting those external features up, and no longer using the factory's algorithm (which happens if you enable a feature without 'tuning' it first) as many things have changing including but not limited to intake manifolds, thermostats, oil system components, underhood air paths (i.e. radiative/reflective cooling), additional/modified air intake pipes, and so forth.

[TXjeepTJ]

I disabled it, but am still having issues tuning the VE table. It looks like if the IAT goes from 100 degrees to 110, it pulls a lot of fuel. When the car reaches operating temp, my idle AFR is 13.3, if I go and drive for 30 minutes or more, my idle AFR becomes 15.0

Maybe the IAT sensor is not getting an accurate reading due to the radiator fans pushing air onto it (heat sinking)? I'm running a MAF w/ the IAT built in. This issue is driving me nuts, haven't been able to tune my car for the past year because the AFR error constantly changes depending on how long I drive it. Car is in OL, LTFT/STFT disabled, DFCO disabled, but something is still screwing with the fueling

[kingtal0n]

I posted this in another thread maybe it will help you track the issue

technically the hotter the air gets, the less dense the air is, the richer it should run.


However this is rarely the real world result. Often things such as:
1. rising temperature increases resistance of electrical circuits such as injector driver circuit, things as the alternator gets hot, voltage output seems to diminish
2. rising temperature means fans run longer and put more electrical load on the alternator which can lower voltage
3. "" does mean less dense air, and since the friction/power requirement of the engine is only barely reduced through thinning oils the engine still needs more air volume than when it is cold, which means more power is lost on the intake stroke and needs to be made up for somehow, which usually results in higher open throttle position (higher IACV counts) when fully warmed up compared to when the climate is cold.
4. "" will/may have a slight effect on wideband readings, depending where they are located. For temperature and possibly pressure reasons. Hotter exhaust gas is expanded more and there will be higher pressure and temp.
5. fuel specific gravity may change significantly if it warms up enough to alter a/f ratio slightly leaner, remember air, water, gasoline are all fluids with specific weight which is density times gravity.
6. Because of all the changing variables, the engine will typically 'run' and 'idle' in a different region of the VE map. It means when you tune the idle cold (say 550rpm and 45kpa) you might not be tuning the engine for when it is hot (550rpm and 52kpa) it could infringe into other cells when warm that it does not when cold
7. because the injector delay map is vs voltage, and voltage is affected by warming resistance of electrical system, the voltage injector delay map may not be compensating enough for electrical voltage drop at the injectors

8. I am sure there is more. The bottom line is there are many reasons why it could happen and many ways to compensate for it. And perhaps most importantly to know that you are not alone. You pretty much described an extremely common occurrence and the ideal method for dealing with it may vary, i.e. your ultimate solution may not be the same for every engine you visit.

I pretty much experience a similar situation with many cars. Fine tuning seemed to help but also recognize something like fuel cling, or fuel leftover between events, can be a thing. If I see it start to get rich and the engine isn't really "hot" (just because cts says 180*F doesn't mean everything is also up to temp) yet I can run it hard for a moment and watch the A/F swing back up near idle once resting again. I guess because each injection event is 'perfect amount of fuel you wanted' it means that if there is anything leftover from the event before it now combines with the new spray, which in turn leaves some behind again for the next event, and so forth, perpetually leaving you rich. And then the motor truly, fully warms (watch oil temperatures as they climb to +190*F 30 minutes later) and fuel can no long stay 'clinged' to the hot engine parts so you get more accurate readings as it all vaporizes and enters the chamber, leaving you lean because you had it tuned for the 'cling' behavior which no longer occurs on a truly hot engine. I'd say if you think this is happening then first only tune the VE while the oil is 200*F, then when you see it rich the next day "cold" (CTS 190*F, Oil 130*F) try adjusting things like IAT and CTS and fuel injection end of injection period to lean it back out.