IAT Correction on tuned engine

[chris72]

Hi
I have recently found an error in the wiring on my bike which resulted the IAT sensor sending a fixed voltage to the EMU (approx 20 degrees)
I have now corrected the error will this affect my existing tune ?

thanks

[Jadzwin]

So if you have tuned the engine in temperature about 20 deg, now it will perform much better in different temperature condition.

Otherwise some fine tuning might be required.

[chris72]

Thanks, i was hoping that was the case

[ihiryu]

Okay, so this is what I'm seeing.

The EMU was getting a signal for 20 degrees, but you tuned it in a different temp?

If that's the case you'll have to open your IAT correction, and take the value in the 20 degree range, and move it to the temp you tuned it. And you'll have to fine tune your IAT correction table.

So lets say I tuned a car in 10 degrees, that would be my 100 marker (meaning no correction). Then I would slowly skew the rest of the temps depending what I needed to do. So for my Skyline, I tuned it in about 35C (95F) so the IATc table shows 35 as my 100. Then as it got colder, I slowly had to remove fuel from my IATc table, so from 20, I put it at 98, and as the table got lower, and lower, I had to remove more and more fuel (98, 96, 94....respectively). And obviously I had to play around with it until I got it right. The easiest way for me was to open up the IATc table, and opened up my AFR/Actual AFR/IAT/EGO Correction gauges. And just hopped on the highway and cruised. I would reference the IAT, and EGO Correction gauges, and would play with the IATc table until there is no correction on the EGO side. It's not perfect,but it's pretty damn close

Since I haven't seen summer yet in TX, I have yet to play with anything above 35c. But I would imagine I would have to add fuel, and remove timing via the IATc, and the Igniton vs IAT tables.

[chris72]

Okay, so this is what I'm seeing.

The EMU was getting a signal for 20 degrees, but you tuned it in a different temp?

If that's the case you'll have to open your IAT correction, and take the value in the 20 degree range, and move it to the temp you tuned it. And you'll have to fine tune your IAT correction table.

So lets say I tuned a car in 10 degrees, that would be my 100 marker (meaning no correction). Then I would slowly skew the rest of the temps depending what I needed to do. So for my Skyline, I tuned it in about 35C (95F) so the IATc table shows 35 as my 100. Then as it got colder, I slowly had to remove fuel from my IATc table, so from 20, I put it at 98, and as the table got lower, and lower, I had to remove more and more fuel (98, 96, 94....respectively). And obviously I had to play around with it until I got it right. The easiest way for me was to open up the IATc table, and opened up my AFR/Actual AFR/IAT/EGO Correction gauges. And just hopped on the highway and cruised. I would reference the IAT, and EGO Correction gauges, and would play with the IATc table until there is no correction on the EGO side. It's not perfect,but it's pretty damn close

Since I haven't seen summer yet in TX, I have yet to play with anything above 35c. But I would imagine I would have to add fuel, and remove timing via the IATc, and the Igniton vs IAT tables.

Thanks for that
I have a large swing in IAT generally from ambient (say 20 degrees) up to 120 degrees at full boost during a run ( not intercooled) my AFR is 12.5 to 11.0 at the moment under high boost but i need to tune this to stay nearer to the 12.5 with IAT correction ( and fit an intercooler )

[ihiryu]

youch.

Yeah....that's gonna suck. So my suggestion is (and this might not be the best way). Would to be to let it idle at ambient until it fully warms up, and figure what temp you are at. After that, everything ABOVE that temp, add correction to it, and it would probably be better to add a lot of correction.

So lets say 35c, is your 100 mark. At the last column of your IATc table, and remove fuel (since you are going rich at the end of your run). Highlight from 35c to the right, and interpolate it (CTRL+H?). And try that. You'll have to fine tune it, but that should get you were you're going. The problem is, when you go intercooled, you're gonna have to start the IATc table from scratch.

The problem is, is that if there is an issue with your tune, IATc is a band aid fix. What you really need to do, is turn all your IATc to 100, and tune your VE map. Then use your IATc to clean it up, not the other way around. Remember that IATc is a GLOBAL multiplier. Meaning that if you pull out 2%, it pulls out 2% out of the entire VE table (obviously after ASE, and Warm up)

[chris72]

Hi
I think i will set IATc to 100 as you suggest and see if i can get a little closer with VE table first, the main aim with IATC is to build a little more safety into the tune to allow for hotter days. I dont mind running a bit rich under high boost as it only hurts power. VE tuning takes a while as the bike is track only with minimal engine cooling and only runs under load for just over 8 seconds lol.

[ihiryu]

No dyno?

Yeah the IATc is just icing to the cake. You don't really want to band aid it

[chris72]

No dyno?

Yeah the IATc is just icing to the cake. You don't really want to band aid it

Used a Dyno for the original setup around 2 years ago but the wiring error only came to light recently, i generally check the logs after every run and make slight adjustments as required

[RHD]

Okay, so this is what I'm seeing.

The EMU was getting a signal for 20 degrees, but you tuned it in a different temp?

If that's the case you'll have to open your IAT correction, and take the value in the 20 degree range, and move it to the temp you tuned it. And you'll have to fine tune your IAT correction table.

So lets say I tuned a car in 10 degrees, that would be my 100 marker (meaning no correction). Then I would slowly skew the rest of the temps depending what I needed to do. So for my Skyline, I tuned it in about 35C (95F) so the IATc table shows 35 as my 100. Then as it got colder, I slowly had to remove fuel from my IATc table, so from 20, I put it at 98, and as the table got lower, and lower, I had to remove more and more fuel (98, 96, 94....respectively). And obviously I had to play around with it until I got it right. The easiest way for me was to open up the IATc table, and opened up my AFR/Actual AFR/IAT/EGO Correction gauges. And just hopped on the highway and cruised. I would reference the IAT, and EGO Correction gauges, and would play with the IATc table until there is no correction on the EGO side. It's not perfect,but it's pretty damn close

Since I haven't seen summer yet in TX, I have yet to play with anything above 35c. But I would imagine I would have to add fuel, and remove timing via the IATc, and the Igniton vs IAT tables.

Generally lower temps require more and as it rises Less fuel

[ihiryu]

Everyone says that, but for me, it actually requires less fuel for me. On every car that I tune (from my dad's GTR, to my wife's miata, and even the R32), my MAT/IAT/whatever you want to call it always ends up making a U.

I'll have to remove fuel when cold, and as it hit's summer, I have to remove fuel (not as much when cold though). The only difference I have, is when the IAT's are cold, I don't mess with Ignition timing, but when it's summer, I will have to remove timing. I have no idea why that is. My cousin's S2000, he had tuned at a shop, and I had to do the same thing for his IAT table in his AEM. It was tuned in the summer, and I had to PULL fuel when it was cold.

I thought it was strange because everywhere I've read, it says the exact same thing, when it's cold you need less fuel because air is more dense etc etc. When I went to the EFI U class, I asked the same thing, and the guy teaching the course says that a lot of times, this happens due to where the sensor is mounted/how well the intercooler works.

He told me to not listen to what everyone else says, and develop a style that works for you. It makes sense, but it is strange. But every ECU I touch, i end up having to do the same thing. Once I dial in the MAT/IAT tables though, it will run fine throughout the year.

Also, here in TX we really don't ever get colder than 40 degrees F.

[ATS_Scott]

Everyone says that, but for me, it actually requires less fuel for me. On every car that I tune (from my dad's GTR, to my wife's miata, and even the R32), my MAT/IAT/whatever you want to call it always ends up making a U.

I'll have to remove fuel when cold, and as it hit's summer, I have to remove fuel (not as much when cold though). The only difference I have, is when the IAT's are cold, I don't mess with Ignition timing, but when it's summer, I will have to remove timing. I have no idea why that is. My cousin's S2000, he had tuned at a shop, and I had to do the same thing for his IAT table in his AEM. It was tuned in the summer, and I had to PULL fuel when it was cold.

I thought it was strange because everywhere I've read, it says the exact same thing, when it's cold you need less fuel because air is more dense etc etc. When I went to the EFI U class, I asked the same thing, and the guy teaching the course says that a lot of times, this happens due to where the sensor is mounted/how well the intercooler works.

He told me to not listen to what everyone else says, and develop a style that works for you. It makes sense, but it is strange. But every ECU I touch, i end up having to do the same thing. Once I dial in the MAT/IAT tables though, it will run fine throughout the year.

Also, here in TX we really don't ever get colder than 40 degrees F.

Are you using Charge Temp Table, and Advanced Lambda Fueling mode?

[ihiryu]

Charge temp tables are used for when coolant runs to the TB correct? Megasquirt calls it the "MAT/CLT Correlation" table. But I don't use coolant through the TB.

Currently I am using Basic AFR. I plan to move over to advance when I get my new injectors since I have to retune anyway.

[ATS_Scott]

Charge temp tables are used for when coolant runs to the TB correct? Megasquirt calls it the "MAT/CLT Correlation" table. But I don't use coolant through the TB.

Currently I am using Basic AFR. I plan to move over to advance when I get my new injectors since I have to retune anyway.

No, Charge temp allows you to give more or less "weight" to either the CLT OR IAT. Give it a shot, I think you will find yout IAT "correction" problems go away. I believe Charge Temp is still active even in the Basic AFR mode.
I only use IAT correction as a safety measure above what I consider safe IAT, to add fuel, reduce timing, and trim boost for these HOT Texas Summers.

[ihiryu]

Scott,

So let me get this straight.

On the Charge Temp Table

0% = IAT reading
100% = CLT reading

I'm a bit of a noob here, so forgive me, but I don't see how this really works. Obviously when you're at a slow speed, the actual IAT is hot because the FMIC isn't really working. As you begin to move, the should get cooler so the IAT drops. Obviously you're never going to idle at 3000 RPM's.

So this is basically a correction table of the IAT table, using MAP vs RPM?

Could you screen shot me an example of your charge temp table, so I can try to get my head wrapped around it. I'm willing to give it a go.

My assumption would be at idle, and close to idle, my Charge Temp Table (CTT) is going to be higher, due to heat soat, and as we go up in the RPM's, it should taper to 0.
And obviously the higher KPA reading we have, it should be closer to 0 as well. Is this correct?

[ATS_Scott]

Scott,

So let me get this straight.

On the Charge Temp Table

0% = IAT reading
100% = CLT reading

I'm a bit of a noob here, so forgive me, but I don't see how this really works. Obviously when you're at a slow speed, the actual IAT is hot because the FMIC isn't really working. As you begin to move, the should get cooler so the IAT drops. Obviously you're never going to idle at 3000 RPM's.

So this is basically a correction table of the IAT table, using MAP vs RPM?

Could you screen shot me an example of your charge temp table, so I can try to get my head wrapped around it. I'm willing to give it a go.

My assumption would be at idle, and close to idle, my Charge Temp Table (CTT) is going to be higher, due to heat soat, and as we go up in the RPM's, it should taper to 0.
And obviously the higher KPA reading we have, it should be closer to 0 as well. Is this correct?

You have the gist of it, but it's a fueling correction based on CLT AND IAT, you get to blend them to get the results you want, and to better maintain AFR from temp fluctuations. I'm not on my tuning laptop, or I'd attach my charge temp table. But there is a good example in the help menu too.

[gips]

Now that was very helpful. Now i understand why my idle and low load AFRs going lean, when the engine bay gets freakin hot. 10x a lot, i was a bit frustrated that i will have to adjust the VE table, when summer comes Now i guess the charge temp will fix that for me. 10x learned a new thingie today, very happy

[ihiryu]

Hey Scott.

So I'm doing a little more reading on the CTT. So if you're closer to the Coolant table, does it offer the same enrichment like from your warm up table?

I added 100% to the bottom rows (just to see what it does), but it just goes to rich lol