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Charge Temp Table


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Hello there, 

first time posting here. 

I would like to ask how do you approch Charge Temp table while tuning the main fuel map?

Im tuning my car on the road havent yet have any access to a dyno.

Seem like the fuel swing is quite a lot when my intake is heat soaked at idle.. do i remove fuel from the IAT trim without adjusting the charge temp table? 

From the way i see it, the only way to properly tune the main fuel map with charge temp table in mind is on the dyno or is it possible to do it without one? 

Chasing my tails here sometimes

Right now ive zero out both IAT and Enrichment table 

Thank you

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On the dyno I generally test with constant water temp but vary the air temp by directing hot air from exhaust or radiator into the air box.  That is a bit hard to do with road tuning.  Probably if it were me I would export a big log into MegalogviewerHD (so you can generate a lambda error math channel) and do a scatter plot of lambda error versus charge temp to see if a trend pops out.  

You may be able to do something similar directly in PC Link by turning on CLL and scatter plotting CLL fuel correction vs Charge temp.

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  • 4 months later...
On 3/5/2020 at 9:18 AM, Adamw said:

On the dyno I generally test with constant water temp but vary the air temp by directing hot air from exhaust or radiator into the air box.

And while doing that, you watch if the measured lambda goes rich/lean and make a correction in the charge temp approximation table until it stays relatively constant? I was thinking to try a heatgun (set to low temp).

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2 hours ago, Rozsko said:

And while doing that, you watch if the measured lambda goes rich/lean and make a correction in the charge temp approximation table until it stays relatively constant?

Yes, but you will need a whole lot more energy than a heat gun.  It not only needs to heat all the air, but the whole intake system, pipework, and anything else before the air temp sensor.  You also want quite a noticable change in air temp - at least 5 deg, preferably 10.  Blocking the intercooler airflow on a turbo car usually works or ducting hot air from exhaust or radiator into the airbox on a NA car is needed. 

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On 7/12/2020 at 1:10 AM, Adamw said:

Yes, but you will need a whole lot more energy than a heat gun.  It not only needs to heat all the air, but the whole intake system, pipework, and anything else before the air temp sensor.  You also want quite a noticable change in air temp - at least 5 deg, preferably 10.  Blocking the intercooler airflow on a turbo car usually works or ducting hot air from exhaust or radiator into the airbox on a NA car is needed. 

You were right. The heatgun has no use. So, as I have no way of ducting the the exhaust back to the intake, I figured I'll remove the coupler between the CAI and the turbo inlet and will close the bonnet. This way it is going to breath much hotter air as the engine temp is increasing.

One more question on this though, when you are on the dyno doing this exercise, would you turn off the blower, so it heats up quicker then when you try to cool it down you turn it on, and repeat?

Thanks

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13 minutes ago, Rozsko said:

One more question on this though, when you are on the dyno doing this exercise, would you turn off the blower, so it heats up quicker then when you try to cool it down you turn it on, and repeat?

No, you want to keep the water temp as constant as possible while trying to vary the air temp only.  Not always possible but that is the aim.  Cardboard blocking the intercooler air flow may work.

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22 minutes ago, Adamw said:

No, you want to keep the water temp as constant as possible while trying to vary the air temp only.  Not always possible but that is the aim.  Cardboard blocking the intercooler air flow may work.

Thx Adam. I have front cooler, so cardboarding would result pretty much the same as turning off the blower, I guess. Anyhow, Thursday is the next session on the Dyno, so will play a bit.

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  • 5 weeks later...

My issue with my current tune is that the car is very lean before it truly warms up (idles around 1.08). The coolant temps will go to 90-100 in few minutes, which only makes the situation worse by shortening the pulse width due to higher charge temp. Before the engine truly  warms up it will take around 20 minutes driving. Then my lambda readings will hit the set targets. I think the area over 2500 rpm works better because it has quite low charge temp numbers.

I'm unsure how to solve this issue. My idea would be to zero out the charge temp table and make a 4D correction table based on MGP and oil temp since it takes a lot longer for the oil to heat up. Would this be the way to go or do you have any better ideas? I know I could use closed loop, but I would like to get the base tune closer rather than making big corrections with CL.

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If your lambda is varying too much with coolant temp then you need smaller numbers in your charge temp table so it is biased more towards air temp as that will vary less during warmup.  

 

2 hours ago, pvainola said:

The coolant temps will go to 90-100 in few minutes,

What charge temp approximation is trying to do is estimate the temperature of the air that is entering the chamber.  Typically at low speeds the intake port wall temperature would be the main influence.  100deg C coolant in a few minutes seems very unusual, so I would be asking myself these questions:  Why isnt your intake port wall the same temp as your coolant?  Is the coolant temp sensor in some part of the cooling system where it doesnt indicate the temperature of the bulk of the coolant that is circulating in the engine?  Has the cooling system been modified, plumbed wrong, or some other issue such as the head gasket on backwards preventing a proper flow path through the engine?

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Ok I think I get what you are saying. If I set the charge temp closer to 0 (was around 60 ) then the ecu will see charge temps closer to IAT. This will cause the ecu to think that the air is colder and therefore it will add more fuel. The change compared to cold engine is smaller so the cold AFR and warm AFR should be closer to each other. 

The plenum is thermally isolated with an spacer which reduces heat transfer. Also my IAT sensor is rather close to the plenum. 

The coolant flow is modified, but it's a standard pathfinder mod on my 350z. I surely hope and highly doubt that I put the headgasket the wrong way around. Removing the heads in this engine is a huge pain. I hope I have some pics to verify that it's installed correctly.

But I do think the engine warms up too fast. The sensor location is stock, but something might be preventing proper coolant flow and could cause too high temps. I tried to bleed the system several times, but I guess I have to try a vacuum pump to be sure. Thanks for the help!

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Charge temp will remove roughly 4% fuel for every 10degC increase of charge temp.  So if you have 100% in the charge temp approx table (fully biased to water temp) and your water temp was 20°C for a cold start and 90°C when warmed up then the charge temp increase of 70°C would mean 28% less fuel when warm.

On the other hand, if your charge temp approximation was fully biased to air temp (0%), and you started with an air temp of 20°C for the cold start and it raised to 50°C when warm then you only have an 12% reduction in fuel from cold to warm.

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