Tuning IAT sensor values
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 812
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From: Metairie Louisiana
Tuning IAT sensor values
2001 6spd. Can a tuner adjust both temperature ceiling and amount of timing deduct for the IAT sensor? I wanted to have the max reconizeable temp set to 90*f, and the max timing pull set to -3*. Then check or adjust igniton timing for street driving on 91 octane.
Former Vendor
Joined: Aug 2011
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From: Tampa Fl
St. Jude Donor '12
what do you mean by temperture ceiling ?
You asking if you can reduce the amount of spark reduction below 90 degees? If that is the question, yes a tuner can do that.
www.TampaTuning.com
You asking if you can reduce the amount of spark reduction below 90 degees? If that is the question, yes a tuner can do that.
www.TampaTuning.com
Last edited by Tampa Tuning; Oct 14, 2011 at 04:16 PM.
Thread Starter
Burning Brakes
Joined: Jun 2010
Posts: 812
Likes: 2
From: Metairie Louisiana
My car is an all stock '01 6spd and it doesn't have any pep. I just put new tires on it (Hankooks), before that it would spin up the worn out run flats in first & a little in second...from punching it. Now with the new rubber it just squats and goes. Soooo after reading some stuff on CAI's I began to wonder if I was losing igntion timing from the IAT sensor baking in underhood temps...hence the question about adjusting it's settings. Now I've spoken to a few tuners and most have recommended not neutering the IAT sensors ignition pull, but to go for a more comprehensive tune. I can buy a "tune in a can" or dyno it...$150 or $250-300. I believe it should run better while realising a stock Ls1 puts out about 300 rwhp. What options do I have and I don't have the money for the bolt ons I'd like to have?
Last edited by had2have-it; Oct 14, 2011 at 08:30 AM.
Platinum Supporting Vendor
Joined: Sep 2001
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First off the IAT is not baking in underhood temps and giving a false reading. It is reading what the intake air temp is and all the intake components can get hot from underhood temps and heat the air. That is the actual temp of the air entering the engine. If you have timing being backed out because of IAT temps, then you want the timing to be backed out, I would not change that. If you want to make a change then figure out how to make the car run cooler and get cooler air to the engine, not fool a sensor.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
You'll get varying opinions on this subject--My belief is that the IAT DOES read underhood temps--and not incoming air temps--However not al the time-When driving it faster like on the freeway the sensor will cool down and finally get close to the outside air temp-But it takes several miles- Get any handheld scanner (buy or borrow) and it will read actual IAT readings in real time---
Especially when driving in town the IAT temp still often spikes to 130-150* where the timing decucts are 8-10 * EVEN though it may be only 70* outside---------
When tuning I remove ALL the deducts at WOT from .52 gram on up up to 122* ---then from 122* and beyond /.52 grams on up remove apprx 65%
At P/T below .52 grams I will remove about 40% up to 122* and beyond 122* maybe 20*
ALSO: with your scanner--make sure your LTFT's are at "0" or slightly negative---AS "just before going to WOT "whatever the positive fuel trims is at that pont is also carried over to your WOT fuel as well as a safety---making your WOT fuel RICH and your engine lazy !!
Especially when driving in town the IAT temp still often spikes to 130-150* where the timing decucts are 8-10 * EVEN though it may be only 70* outside---------
When tuning I remove ALL the deducts at WOT from .52 gram on up up to 122* ---then from 122* and beyond /.52 grams on up remove apprx 65%
At P/T below .52 grams I will remove about 40% up to 122* and beyond 122* maybe 20*
ALSO: with your scanner--make sure your LTFT's are at "0" or slightly negative---AS "just before going to WOT "whatever the positive fuel trims is at that pont is also carried over to your WOT fuel as well as a safety---making your WOT fuel RICH and your engine lazy !!
Platinum Supporting Vendor
Joined: Sep 2001
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The only way a IAT reads underhood temps is when that heat radiates to the intake tract and heats the air passing over the IAT which is the actual air temp of the air going into the engine. The reason it drops with speed is because air is moving faster across the surfaces and does not absorb as much heat from the material. Now a IST sensor will read under hood temps as the intake can get hotter from under hood temps, Corvettes do not have those and only a car with an aluminum intake would need it.
Le Mans Master
Joined: Aug 2005
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From: CA.
St. Jude Donor '13-'14-'15
The radiating underhood heat does not rasie the temp of the incoming air---but rasies the temp of the SENSOR---So even if the incoming air is 70* the SENSOR is heat soaked and may read 130*---It's mounted in black plastic which absorbs heat--and the cooling fans blast the air ducting and sensor with HOT air--The IAT does not stick way down into the airstream anyway--With a 5 pin connector MAF --the IAT is bulit into the MAF which makes it even worse---because how the MAF works is it is heated with voltage and the incoming air cools it down which changes the fuel command - so the MAF voltage also heats the IAT unwantingly
IMHO---
IMHO---
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Pro
Joined: Feb 2003
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From: Detroit MI
The radiating underhood heat does not rasie the temp of the incoming air---but rasies the temp of the SENSOR---So even if the incoming air is 70* the SENSOR is heat soaked and may read 130*---It's mounted in black plastic which absorbs heat--and the cooling fans blast the air ducting and sensor with HOT air--The IAT does not stick way down into the airstream anyway--With a 5 pin connector MAF --the IAT is bulit into the MAF which makes it even worse---because how the MAF works is it is heated with voltage and the incoming air cools it down which changes the fuel command - so the MAF voltage also heats the IAT unwantingly
IMHO---
IMHO---
The simple fact is that yes, the inlet tract can experience heat soak. BUT... That means that the inlet tubing is also heating the incoming air to some extent. If you actually take a thermocouple reading out by the filter versus right at the throttle body, you'll likely see a difference. If the IAT is reading higher than the outside ambient, it's probably RIGHT.
Remember that the PCM is also biasing intake temps based on both measured IAT and ECT on newer vehicles because they recognize that heat transfer doesn't stop at the throttle body. The intake manifold and cylinder head port can both also skew the temp of the air coming into the cylinders. The factory calibrators know this and have tuned the car appropriately to compensate. It's funny how the guys "fixing" IAT heat soak are often the same ones complaining about inconsistent fueling when the outside weather changes. Coincidence?
...and I'll give you a dollar if you can prove that the hot wire element of the MAF is measurably increasing intake charge temp. This is more internet BS from people who have never worked on these things with the right tools at the OEM level.
Le Mans Master
Joined: Aug 2005
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From: CA.
St. Jude Donor '13-'14-'15
"Village wisdom from internet forums "?? C'mon now I said this is a comtroversial issue and it is just "My Opinion "-- AND it is not based on village wisdom or forum chatter but based on 1000's of hours of data logging while tuning over 1200 cars---including dyno testing as well-- My last remark will be you are trying to say in the small 12 " length of a C5 intake tract the underhood radiant heat will also HEAT the incoming air?? taking it from say 60* to 130* ?? even though it may only actually BE in the tract for less than a millisecond???
Not gonna happen--sorry---
Not gonna happen--sorry---
Pro
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From: Detroit MI
It's not controversial, it's science. Heat transfer in fact, and I had a four credit class on it years ago where I got an "A" and continue to use it on a regular basis as an actual engineer.
If you can dig up where I said there'd be a 70*F increase from a 12" pipe length, I'll give you another dollar to go with the one you aren't getting from the MAF heating argument. Don't put words in my mouth. I merely said that the heat transfer does happen. And "for less than a millisecond"? At what flow rate, density, and inlet pipe size? It might be time for you to sharpen your pencil here. You're also conveniently forgetting what I said about heat transfer still happening between the throttle body and the intake valve as well. You can't come in and play half of the technical card on me. Either get your data straight or quit misdirecting people.
If you can dig up where I said there'd be a 70*F increase from a 12" pipe length, I'll give you another dollar to go with the one you aren't getting from the MAF heating argument. Don't put words in my mouth. I merely said that the heat transfer does happen. And "for less than a millisecond"? At what flow rate, density, and inlet pipe size? It might be time for you to sharpen your pencil here. You're also conveniently forgetting what I said about heat transfer still happening between the throttle body and the intake valve as well. You can't come in and play half of the technical card on me. Either get your data straight or quit misdirecting people.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Buddy take a chill pill----Leave your IAT table alone--and tune your cars your way i could care less---I know there is theory and reality
science and religion----But with an IAT table in a GM vehicle--Remove all the timing deducts below 122-131* and remove about 1/2 of it from136 to 167* and you will get More timing in your motor--- which equals More power--- with NO KR or pinging---
science and religion----But with an IAT table in a GM vehicle--Remove all the timing deducts below 122-131* and remove about 1/2 of it from136 to 167* and you will get More timing in your motor--- which equals More power--- with NO KR or pinging---
Pro
Joined: Feb 2003
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From: Detroit MI
I fully recognize that many engines can benefit from increased timing. It's HOW one adds it that is of concern here. The timing vs IAT table is there because of a very real physical relationship between charge temperature and burn rate. If the charge is hotter, burn speed increases, so less timing advance is necessary to hit either MBT or the knock limit.
As long as the actual charge temp is relatively accurate, I prefer to work with the tables set forth by the OEM calibrators that got paid for literally three years worth of development time to fine tune them instead of trying to reinvent the wheel in an afternoon on the dyno. There's a better (and more proper) way to add overall timing, but that won't force the tOOners of the world to do things right I guess...
Le Mans Master
Joined: Aug 2005
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From: CA.
St. Jude Donor '13-'14-'15
Tuning a car's spark table is much easier and faster--not to mention more precise--When you "ask" for say 24* of timing you actually "get" 24* of actual timing----otherwise you are constantly having to factor in IAT deducts as the IAT temp changes---There's no way to use the hi octane table as a reference point for performance tuning IF you are always having to consider deducts---
