$8D 730 guys ditch the stock IAT / MAT
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$8D 730 guys ditch the stock IAT / MAT
After dealing with fluctuation BLM's due to temperature on my $8D 730 TPI I decided to do something that I have been meaning to due for awhile. The stock IAT \ MAT sensor on the 730 TPI is actually a coolant temperature sensor. The whole casing of the sensor is metal, so it is not measuring the temperature of the air coming in the intake; it is measuring the temperature of the plenum. To get more accurate reading of the temperature of the air entering the intake I have decided to change the IAT / MAT sensor to a real IAT / MAT sensor. Below you can see a picture of the stock MAT sensor versus the new one I have put in. The sensor is a direct swap except for the connector. The resistance vs. temperature rating of both sensors are identical.
The stock connector on the harness will not fit the new sensor so you must also change the connector. Here is the part numbers needed to complete the sensor change.
Air Temp Senor: GM # 25036751
Pigtail: Motormite # 85110
Just cut off the old sensor pigtail and solder on the new one. You can also buy a new weather pack connector for the harness end and make a whole new connector pigtail like I did.
After changing the sensor you must also change the "Inverse MAT term Lookup Delta Multiplier Vs. Airflow" table. I used a table already created by Glenn91L98GTA for a remote mount temp sensor found here
After doing this modification I have definitely noticed more stable BLM. The table could be slightly edited make it even more accurate but I am happy with the improvement. It should also be noted that this mod will do nothing on a TPI MAF car. The MAF computer calibration does not use the air temperature sensor for fuel calculations.
Here you can see the difference between the stock IAT / MAT (which is a coolant temp sensor) vs. the better IAT / MAT sensor (a real IAT sensor). The real IAT sensor has a plastic top with the sensor element in it so it is not affect by heat soak of the plenum.
The stock connector on the harness will not fit the new sensor so you must also change the connector. Here is the part numbers needed to complete the sensor change.
Air Temp Senor: GM # 25036751
Pigtail: Motormite # 85110
Just cut off the old sensor pigtail and solder on the new one. You can also buy a new weather pack connector for the harness end and make a whole new connector pigtail like I did.
After changing the sensor you must also change the "Inverse MAT term Lookup Delta Multiplier Vs. Airflow" table. I used a table already created by Glenn91L98GTA for a remote mount temp sensor found here
After doing this modification I have definitely noticed more stable BLM. The table could be slightly edited make it even more accurate but I am happy with the improvement. It should also be noted that this mod will do nothing on a TPI MAF car. The MAF computer calibration does not use the air temperature sensor for fuel calculations.
Here you can see the difference between the stock IAT / MAT (which is a coolant temp sensor) vs. the better IAT / MAT sensor (a real IAT sensor). The real IAT sensor has a plastic top with the sensor element in it so it is not affect by heat soak of the plenum.
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Here you can see the difference connector used on each sensor and why a new pigtail is needed.
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Here is a picture of the stock pigtail and the custom one I made for the new sensor.
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I'm about 90% sure the curves aren't an exact match. Close, but not exact. That is of course if the stock IAT is the same part number as the CTS. If it isn't then these curves might very well line up. In either case they're usually close enough.
FTW, the CTS takes 20-30 seconds to report 63% of a temperature change and the open end IAT takes less than 15 seconds. That's info straight from the source, delphi product data.
One other consideration is how the IAT is used. It is upstream of the base/runners. Maybe the code knows this and wants to know the intake manifold temps. Think of it this way, if the air coming into the plenum is 50d and the intake manifold temp is 200d, then through thermal conductivity the temp of the air entering the head port will be greater than 50d! Now let's say the same air temp coming in (50d) goes into an intake that is 50d, then there will be very little temp change and approx 50d air will enter the head ports. An engine moves a LOT of air and the intake plenum, runners, base all have a LOT of surface area. This is why (I think) GM used the slower heat-soak prown sensor. In the utbi code it uses the fast reacting IAT sensor but there was a need to blend it's signal with that of the CTS to get the fueling correct.
In short; I would look at the code and change it accordingly to understand the faster sensor because the intake manifold temp is a BIG factor
.
In an ideal world the perfect upgrade would be thermocouples (~1 second response time).
FTW, the CTS takes 20-30 seconds to report 63% of a temperature change and the open end IAT takes less than 15 seconds. That's info straight from the source, delphi product data.
One other consideration is how the IAT is used. It is upstream of the base/runners. Maybe the code knows this and wants to know the intake manifold temps. Think of it this way, if the air coming into the plenum is 50d and the intake manifold temp is 200d, then through thermal conductivity the temp of the air entering the head port will be greater than 50d! Now let's say the same air temp coming in (50d) goes into an intake that is 50d, then there will be very little temp change and approx 50d air will enter the head ports. An engine moves a LOT of air and the intake plenum, runners, base all have a LOT of surface area. This is why (I think) GM used the slower heat-soak prown sensor. In the utbi code it uses the fast reacting IAT sensor but there was a need to blend it's signal with that of the CTS to get the fueling correct.
In short; I would look at the code and change it accordingly to understand the faster sensor because the intake manifold temp is a BIG factor
.In an ideal world the perfect upgrade would be thermocouples (~1 second response time).
Last edited by JPrevost; Oct 16, 2005 at 03:41 PM.
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The coolant temp sensor and the air temp sensor on TPI are in fact the same part number to verify that.
As far as the code goes I still have no idea how to read code so I hope RBob or someone can clue me in on that. I am very interested to learn how the code calculates out the temperature of air entering the cylinders.
I assumed, which is a bad thing to do, that the code gets the temperature of the MAT / IAT sensor in the plenum then uses the MAT table to calculate the actual temperature of the air entering the cylinders. Which is why I figured modifying the MAT table to account for the new sensor would be a good way to fix this. I know the temperature of the air in the plenum in not the temperature of the air entering the cylinders from the air adsorbing the heat in the intake tract but I figured the MAT table was there to account for this.
I didn't even think that the code may use the coolant temperature sensor and MAT / IAT sensor together to figure out the temperature of the air entering the cylinders like you said. If the code uses the coolant temperature sensor and the MAT sensor together to figure out the temperature of the air entering the cylinders then changing the MAT / IAT sensor may be a bad thing. The code could calculate the difference in plenum and coolant temperature to try to figure out the temperature of the air. But to me this seems like a more complicated way of doing it. Hopefully someone can take a look at the code and clue me in.
As far as the code goes I still have no idea how to read code so I hope RBob or someone can clue me in on that. I am very interested to learn how the code calculates out the temperature of air entering the cylinders.
I assumed, which is a bad thing to do, that the code gets the temperature of the MAT / IAT sensor in the plenum then uses the MAT table to calculate the actual temperature of the air entering the cylinders. Which is why I figured modifying the MAT table to account for the new sensor would be a good way to fix this. I know the temperature of the air in the plenum in not the temperature of the air entering the cylinders from the air adsorbing the heat in the intake tract but I figured the MAT table was there to account for this.
I didn't even think that the code may use the coolant temperature sensor and MAT / IAT sensor together to figure out the temperature of the air entering the cylinders like you said. If the code uses the coolant temperature sensor and the MAT sensor together to figure out the temperature of the air entering the cylinders then changing the MAT / IAT sensor may be a bad thing. The code could calculate the difference in plenum and coolant temperature to try to figure out the temperature of the air. But to me this seems like a more complicated way of doing it. Hopefully someone can take a look at the code and clue me in.
Last edited by 89 Iroc Z; Oct 16, 2005 at 05:26 PM.
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I think you'll be fine with just spending some time on the IAT fuel table. I was just being super sceptical and playing devils advicate.
If anything, faster reacting is almost always a plus... let's just hope somebody that has looked at the code comments with their thoughts. It's always good to brain storm and if anything, you should do some datalogging for me of both sensor types on a cold started engine. I'll process the data and tell you how it's effected the overal tune . It might not even be noticed in the BLM/INT's!
If anything, faster reacting is almost always a plus... let's just hope somebody that has looked at the code comments with their thoughts. It's always good to brain storm and if anything, you should do some datalogging for me of both sensor types on a cold started engine. I'll process the data and tell you how it's effected the overal tune
. It might not even be noticed in the BLM/INT's! 
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This is funny to me. During my TPI swap I ordered an IAT from several different parts suppliers thru work. I sent them all back complaining that they kept sending me the CTS.
I finally went to AutoZone (shutup...) and dug thru the IAT drawer until I found what I was expecting. An IAT with a plastic cage and a little element inside.
I mounted the IAT in the plenum. Would this call for adjustment to the "Inverse MAT term Lookup Delta Multiplier Vs. Airflow"?
I finally went to AutoZone (shutup...) and dug thru the IAT drawer until I found what I was expecting. An IAT with a plastic cage and a little element inside.
I mounted the IAT in the plenum. Would this call for adjustment to the "Inverse MAT term Lookup Delta Multiplier Vs. Airflow"?
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V8Astro Captain,
If you are using a real IAT sensor you will need to change the inverse MAT table to be accurate. Though a real IAT will not plug up to the stock TPI harness like i mentioned above. Did you change the pigtail on the harness?
JPrevost,
I did not get before after data logs, but there was a noticeable difference in BLM stability across temperature range, nothing huge but there was a difference. The table I am using is probably a little off since it was used on a setup with the IAT / MAT sensor mounted in the air hose before the TB.
If you are using a real IAT sensor you will need to change the inverse MAT table to be accurate. Though a real IAT will not plug up to the stock TPI harness like i mentioned above. Did you change the pigtail on the harness?
JPrevost,
I did not get before after data logs, but there was a noticeable difference in BLM stability across temperature range, nothing huge but there was a difference. The table I am using is probably a little off since it was used on a setup with the IAT / MAT sensor mounted in the air hose before the TB.
Last edited by 89 Iroc Z; Oct 19, 2005 at 10:13 PM.
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Originally posted by 89 Iroc Z
V8Astro Captain,
If you are using a real IAT sensor you will need to change the inverse MAT table to be accurate. Though a real IAT will not plug up to the stock TPI harness like i mentioned above. Did you change the pigtail on the harness?
V8Astro Captain,
If you are using a real IAT sensor you will need to change the inverse MAT table to be accurate. Though a real IAT will not plug up to the stock TPI harness like i mentioned above. Did you change the pigtail on the harness?
Funny how dumb luck worked in my favor.
Here's what I found in my MAT inverse...table:
Code:
gm/sec Multiplier
0 ------------- 1.000
16 -------------- .630
32 -------------- .400
48 -------------- .280
64 -------------- .210
80 -------------- .160
96 -------------- .13
112 -------------- .13
128 -------------- .13
144 -------------- .13
160 -------------- .13
176 ---------------.13
192 -------------- .13
208 -------------- .13
224 -------------- .13
240 -------------- .13
256 -------------- .13 Last edited by V8Astro Captain; Oct 16, 2005 at 08:39 PM.
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Depending on what your wanting to do, you just might want to know the manifold temperature.
There's also an all composite MAT (the sensing element, isn't exposed to the airflow, like in the IAT/MATs, shown). It seems to react to delta temps as fast as the exposed sensor ones.
There's also an all composite MAT (the sensing element, isn't exposed to the airflow, like in the IAT/MATs, shown). It seems to react to delta temps as fast as the exposed sensor ones.
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Originally posted by V8Astro Captain
Here's what I found in my MAT inverse...table:
gm/sec Multiplier
0 ------------- 1.000
16 -------------- .630
32 -------------- .400
48 -------------- .280
64 -------------- .210
80 -------------- .160
96 -------------- .13
112 -------------- .13
128 -------------- .13
144 -------------- .13
160 -------------- .13
176 ---------------.13
192 -------------- .13
208 -------------- .13
224 -------------- .13
240 -------------- .13
256 -------------- .13
[/B]
Here's what I found in my MAT inverse...table:
gm/sec Multiplier
0 ------------- 1.000
16 -------------- .630
32 -------------- .400
48 -------------- .280
64 -------------- .210
80 -------------- .160
96 -------------- .13
112 -------------- .13
128 -------------- .13
144 -------------- .13
160 -------------- .13
176 ---------------.13
192 -------------- .13
208 -------------- .13
224 -------------- .13
240 -------------- .13
256 -------------- .13
[/B]
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From: Costal Alabama
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Just for further clarification here is a comparison of stock values and what I am using
As noted before Glenn91L98GTA's values are for a relocated MAT. He has is using a LT1 type MAT relocated in the rubber hose just in front of the throttle body. The LT1 MAT is an all plastic casing MAT that is designed to be mounted in the hose before the TB.
Code:
"Inverse MAT term Lookup Delta Multiplier Vs. Airflow" Table
(As labeled in Tuner Cat's definition)
Stock Glenn91L98GTA
AUJP Values
gm/sec -------- Multiplier --------
--------- --------- -----------------
0 1.000 1.000
16 0.750 0.805
32 0.500 0.523
48 0.281 0.297
64 0.211 0.117
80 0.156 0.094
96 0.125 0.086
112 0.125 0.078
128 0.125 0.070
144 0.125 0.070
160 0.125 0.070
176 0.125 0.070
192 0.125 0.070
208 0.125 0.070
224 0.125 0.070
240 0.125 0.070
256 0.125 0.070
Increasing the values in the table will lean out the mixture,
decreasing the values will richen the mixture. Last edited by 89 Iroc Z; Oct 16, 2005 at 10:43 PM.
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Originally posted by Grumpy
That looks like a CTS/IAT blend table, which is different from the inverse look up table.
That looks like a CTS/IAT blend table, which is different from the inverse look up table.
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Here's the Sticky that talks about what your doing.
8D MAT & PW calc
In my research, I found guys using the Fiero AT sensor also.
The ZR1 uses a threaded sensor w/plastic cage like the pic above.
I found that the ZR1 bin uses the exact same table ( $87FD I think) as AUJP.
I checked and the table is called in the ZR1 bin code.
So it didn't appear to be a leftover.
I'd imagine the air flow table is different.
Personally, I don't see why you're changing the sensor. The code is setup to use that all metal sensor to
compensate for the plenum heating.
If your having problems, then tune the table in that area. Swapping to a new sensor is like starting from scratch.
Glenn's table will just give you a head start.
Here's the all the related code:
So it's (tbl 880E air flow comp l/u * (cts-mat) ) * 2 + MAT = T<sub>1</sub>
T<sub>1</sub> is then used as the l/u in tbl 87FD = T<sub>2</sub>.
Then its T<sub>2</sub> * 128 +233 = T<sub>3</sub>
Then it's cyl vol ($86DD) / T<sub>3</sub> = L006D = T<sub>corr</sub> mass of cylinder air
8D MAT & PW calc
In my research, I found guys using the Fiero AT sensor also.
The ZR1 uses a threaded sensor w/plastic cage like the pic above.
I found that the ZR1 bin uses the exact same table ( $87FD I think) as AUJP.
I checked and the table is called in the ZR1 bin code.
So it didn't appear to be a leftover.
I'd imagine the air flow table is different.
Personally, I don't see why you're changing the sensor. The code is setup to use that all metal sensor to
compensate for the plenum heating.
If your having problems, then tune the table in that area. Swapping to a new sensor is like starting from scratch.
Glenn's table will just give you a head start.
Here's the all the related code:
Code:
;--------------------------------------------------
; LK UP (COOLANT - MAT) DELTA MULT
; FOR INV TERM L.U. vs AIR FLOW
;
; TBL = MULT * 128
;--------------------------------------------------
ldaa *L006B ; gms/sec, LIMITED AIR FLOW FROM IDEAL GAS LAW
ldx #0x880E ; Table (COOLANT - MAT) DELTA MULT
; FOR INV TERM L.U. vs AIR FLOW
jsr LE3D8 ; 2D LOOK UP, NO OFF SET (Is LE3D0 in ANHT)
ldab *L005D ; FILTERED COOLANT TEMP
subb *L0063 ; Filtered CTS -INV A/D MAT
bcc LD7FA ; BR IF Carry Clear (Goes to LD7F2 in ANHT)
; ... else
clrb ; B = 0 (limit to zero)
LD7FA: mul ;(A x B) INV TERM L.U. vs AIR FLOW * (Filtered CTS -INV A/D MAT) ; CRef: 0xD7F7
lsld ; MULT * 2
bcs LD802 ; BR IF OVERFLOW (Goes to LD7FA in ANHT)
; ... else
adda *L0063 ; Add INV A/D MAT back in
bcc LD804 ; BR IF Carry Clear (Goes to LD7FC in ANHT)
; ... else
LD802: ldaa #0xFF ; FORCE MAX VAL ; CRef: 0xD7FC
;--------------------------------------------------
; MAT COMP Vs MAT
; TABLE is MAT COMP COUNTS
;--------------------------------------------------
LD804: ldx #0x87FD ; MAT COMP VS MAT TBL (^.5) ; CRef: 0xD7E7,0xD800
jsr LE3D8 ; 2D LOOK UP, NO OFF SET (Is LE3D0 in ANHT)
ldab #0x80 ; VAL = 128
mul ; * 128
addd #0x7480 ; MAT = ((MAT^.5)+233)*128
pshb ; Store acc. B to stack
psha ; Store acc. A to stack
pulx ; ((MAT^.5)*128)+233, (Denom)
ldd L86DD ; CYL VOL & UNIT CONV, 159d, (LITRE)
fdiv ;
stx *L006D ; MAT (not Inverse) ; SAVE MAT, CYL VOL & SCALING TERM
; CYL VOL/((MAT^.5)*128) + 233 T<sub>1</sub> is then used as the l/u in tbl 87FD = T<sub>2</sub>.
Then its T<sub>2</sub> * 128 +233 = T<sub>3</sub>
Then it's cyl vol ($86DD) / T<sub>3</sub> = L006D = T<sub>corr</sub> mass of cylinder air
Last edited by Z69; Oct 17, 2005 at 06:37 AM.
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Based on the above, and to reiterate what Rbob posted.
Maybe a little more clearly.
The air flow comp has no effect until the cts is > than the mat. The air flow comp table determines how much effect the (CTS-MAT) has on the PW.
The MAT itself has a direct (indirect?) effect on the PW. Changing the air flow comp table will change how much the cts-mat (cts) effects the PW.
Changing the 87FD table will determine how much the PW is effected by the temp in general for the most part.
It will take some thought on how to prove one change vs another is actually helping. There are to many variables to try and hold constant to isolate the MAT in the PW equation.
Swapping to a plastic caged sensor simply removes the plenum heat from the PW equation and makes the PW respond faster to changes in the IAT.
So if you take the time to tune the air flow comp table with the stock sensor.......
Dyno runs or similar with a near constant starting cts at a minimum I'd think. Or if you could log L006B & L006D morning and afternoon while using a WB, locked INT, and trying to keep everything else the same.
That would tell you. After you did some back calculating
Also, when you change these tables, it will affect the calc'd mass air flow which will then change where the l/u is at too.
Maybe a little more clearly.
The air flow comp has no effect until the cts is > than the mat. The air flow comp table determines how much effect the (CTS-MAT) has on the PW.
The MAT itself has a direct (indirect?) effect on the PW. Changing the air flow comp table will change how much the cts-mat (cts) effects the PW.
Changing the 87FD table will determine how much the PW is effected by the temp in general for the most part.
It will take some thought on how to prove one change vs another is actually helping. There are to many variables to try and hold constant to isolate the MAT in the PW equation.
Swapping to a plastic caged sensor simply removes the plenum heat from the PW equation and makes the PW respond faster to changes in the IAT.
So if you take the time to tune the air flow comp table with the stock sensor.......
Dyno runs or similar with a near constant starting cts at a minimum I'd think. Or if you could log L006B & L006D morning and afternoon while using a WB, locked INT, and trying to keep everything else the same.
That would tell you. After you did some back calculating
Also, when you change these tables, it will affect the calc'd mass air flow which will then change where the l/u is at too.
Last edited by Z69; Oct 17, 2005 at 07:33 AM.
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Originally posted by Grumpy
There's also an all composite MAT (the sensing element, isn't exposed to the airflow, like in the IAT/MATs, shown). It seems to react to delta temps as fast as the exposed sensor ones.
There's also an all composite MAT (the sensing element, isn't exposed to the airflow, like in the IAT/MATs, shown). It seems to react to delta temps as fast as the exposed sensor ones.
Which might be another reason GM used the sensor it did.
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Originally posted by Z69
Got an application or p/n? Sticking one of those open cage ones into the plenum might lead to some fouling.
Which might be another reason GM used the sensor it did.
Got an application or p/n? Sticking one of those open cage ones into the plenum might lead to some fouling.
Which might be another reason GM used the sensor it did.
I could see the need for a faster reacting sensor if you've got a cowl with hot-air intake. At idle the engine bay gets HOT, even with the fan on. Start moving and the intake air temps drop almost instantly. That's just something I noticed with my TBI which has a full composite/plastic open cage IAT/MAT.
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I went to the plastic LT1 sensor in the plenum on a LT1 converted intake. I just filed down and threaded the plastic sensor to fit in a 3/8 NPT hole. I didn't replace my weatherpack fitting either. I just filed off the edges so that the fitting was square. Now it will fit in both types of sensors. So far I have not revised my IMAT table. I was going to relocate the MAT into the intake before doing that.
Last edited by 69 Ghost; Oct 17, 2005 at 01:01 PM.
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After reading how the code actually handles the air temp calculation I think it's more luck that this improved my BLM stability. Glenn91L98GTA's table does need some adjustment. Each intake design is going to require it's own IMAT table. I think I will start over with this one and go back to the stock MAT, get a steady 128 across the board and then try changing back to this real IAT / MAT and see if I can adjust the IMAT table to maintain a steady BLM.
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Originally posted by JPrevost
I could see the need for a faster reacting sensor if you've got a cowl with hot-air intake. At idle the engine bay gets HOT, even with the fan on. Start moving and the intake air temps drop almost instantly. That's just something I noticed with my TBI which has a full composite/plastic open cage IAT/MAT.
I could see the need for a faster reacting sensor if you've got a cowl with hot-air intake. At idle the engine bay gets HOT, even with the fan on. Start moving and the intake air temps drop almost instantly. That's just something I noticed with my TBI which has a full composite/plastic open cage IAT/MAT.
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Originally posted by V8Astro Captain
Yeah my air filter is right behind my radiator. I've noticed a 40°-50°F difference in temp while driving mixed city and hiway.
Yeah my air filter is right behind my radiator. I've noticed a 40°-50°F difference in temp while driving mixed city and hiway.
Some investigation about the Accel Gen VII will reveal why they use a manifold temp. correction.
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Has anybody looked at the LT1 codes? I would think the da2-3 on the 92-3 LT1's that are bank fired would be a good place to start. You could see how the IAT is used for the calculations as opposed to the MAT. Wonder if it is easy enough to change the code with a patch to match those calcs. May be a something to look at for guys running relocated MATs -I guess you could say change the code from a MAT type to a IAT type.
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Originally posted by 69 Ghost
Has anybody looked at the LT1 codes?
Has anybody looked at the LT1 codes?
All the *answers* are in the 58 code. Being a turbo application, the MAT gets to be an extremely critical issue.
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OK after reading about MATs for about the 10th time. I have come to this conclusion. It is generally thought that relocating the MAT is good. The MATs/IAT's that have a plastic housing is quicker and preferred. The tables can be a pain but it appears that there is no better option.
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Originally posted by 89 Iroc Z
After reading how the code actually handles the air temp calculation I think it's more luck that this improved my BLM stability. Glenn91L98GTA's table does need some adjustment. Each intake design is going to require it's own IMAT table. .
After reading how the code actually handles the air temp calculation I think it's more luck that this improved my BLM stability. Glenn91L98GTA's table does need some adjustment. Each intake design is going to require it's own IMAT table. .
I do agree that the table is ONLY a starting point and a person MUST tweak the table because unless you run the identical setup (intake manifold, thermostat, air filter/cold air, IAT/MAT sensor and possibly the location in the intake tract), it will NOT be correct. But it is still WAY better than the stock table IF you run a re-located MAT infront of the TB.
I'm glad to see people are really diving into this. I would also be curious on people's variations and what worked best for them.
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Originally posted by 69 Ghost
The tables can be a pain but it appears that there is no better option.
The tables can be a pain but it appears that there is no better option.
Last edited by Grumpy; Oct 19, 2005 at 05:39 PM.
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Glenn91L98GTA,
What intake setup where you running on your car when you made that table? If i remember right I think you said you were running a mini-ram. If that the case the table need more work, do to TPI's long runners which will cause more heat transfer to the intake air charge.
What intake setup where you running on your car when you made that table? If i remember right I think you said you were running a mini-ram. If that the case the table need more work, do to TPI's long runners which will cause more heat transfer to the intake air charge.
Last edited by 89 Iroc Z; Oct 19, 2005 at 10:12 PM.
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Originally posted by Glenn91L98GTA
(intake manifold, thermostat, air filter/cold air, IAT/MAT sensor and possibly the location in the intake tract),
(intake manifold, thermostat, air filter/cold air, IAT/MAT sensor and possibly the location in the intake tract),
The vapor level temps are part of what you're looking at. You can see it change ever so slightly in some areas when they go from summer to winter gas.
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Originally posted by 89 Iroc Z
Glenn91L98GTA,
What intake setup where you running on your car when you made that table?
Glenn91L98GTA,
What intake setup where you running on your car when you made that table?
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Originally posted by 89 Iroc Z
After reading how the code actually handles the air temp calculation I think it's more luck that this improved my BLM stability.
After reading how the code actually handles the air temp calculation I think it's more luck that this improved my BLM stability.
Anyone else seen it? Make sure to include inlet info.
People sucking air off the radiator might find more HP spending their time there first.
Originally posted by 69 Ghost I have come to this conclusion. It is generally thought that relocating the MAT is good.
I can be said that at higher airflow that an IAT might be a better representation of air temp going to the cylinder.
But at low airflows I'm no so sure an IAT is better in a n/a app. Assuming TPI style intake, not TBI/single plane stuff.
Anybody got LT1 IAT table info or how it's used in the calcs?
I still need to review my $58/60 stuff.
And you guys seeing this are running heated o2's?
So your not chasing the wrong sensor problem.
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I have the definitions for both the da2-3 and the EE bins. There are no IAT tables that I know of at least TC has not defined them. I asked a friend that had a 94Z28 to look them up for me -no such luck. Again that was part of the reason that I was looking for a da2-3 hac. There was some info on somebody doing one about 5 years ago but I never was able to dig it up. The schematics are virtually identical to the $8d with the only exception of the Opti as opposed to the hei.
For me this table is probably a wasted effort as I am in So. Cal. I run at very consistent temps. The temp here is only about 60-85 degrees most of the time and sometimes I may see extremes of 40 and 100. It would seem that this sensor is just like people were stating. It acts more like a coolant sensor, is slow acting, and it is measuring the actual temp of the intake. Maybe GM just assumed that the temp at the valve -like Grumpy said would be the intake temp because the air would eventually heat up to a steady-state condition of the intake. The Cold Air Box would still work as they should help cool down the running temp. This would also work for the turbo $58 guys pretty well regardless if they are running a intercooler or not. With that being said comparisons to a bin with a IAT should be made to see the differences in the code.
For me this table is probably a wasted effort as I am in So. Cal. I run at very consistent temps. The temp here is only about 60-85 degrees most of the time and sometimes I may see extremes of 40 and 100. It would seem that this sensor is just like people were stating. It acts more like a coolant sensor, is slow acting, and it is measuring the actual temp of the intake. Maybe GM just assumed that the temp at the valve -like Grumpy said would be the intake temp because the air would eventually heat up to a steady-state condition of the intake. The Cold Air Box would still work as they should help cool down the running temp. This would also work for the turbo $58 guys pretty well regardless if they are running a intercooler or not. With that being said comparisons to a bin with a IAT should be made to see the differences in the code.
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Originally posted by 69 Ghost
. . .With that being said comparisons to a bin with a IAT should be made to see the differences in the code.
. . .With that being said comparisons to a bin with a IAT should be made to see the differences in the code.
RBob.
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Originally posted by Z69
But why is it better for a n/a engine?
I can be said that at higher airflow that an IAT might be a better representation of air temp going to the cylinder.
But at low airflows I'm no so sure an IAT is better in a n/a app. Assuming TPI style intake, not TBI/single plane stuff.
And you guys seeing this are running heated o2's?
So your not chasing the wrong sensor problem.
But why is it better for a n/a engine?
I can be said that at higher airflow that an IAT might be a better representation of air temp going to the cylinder.
But at low airflows I'm no so sure an IAT is better in a n/a app. Assuming TPI style intake, not TBI/single plane stuff.
And you guys seeing this are running heated o2's?
So your not chasing the wrong sensor problem.
Might read back about some of my past comments on this.
I haven't run closed loop, in my toy for 5+ years now, so I'd say the heated O2 sensor issue really doesn't apply..
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Originally posted by Z69
Where is the MAT/IAT mounted on a Syclone?
Where is the MAT/IAT mounted on a Syclone?
All the *answers* are in the 58 code. Being a turbo application, the MAT gets to be an extremely critical issue.
MAT, Manifold Air Temperature, it's in the plenum.....
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Originally posted by 69 Ghost
For me this table is probably a wasted effort as I am in So. Cal.
For me this table is probably a wasted effort as I am in So. Cal.
I guess the folks at Accel are just nuts for wanting to include Manifold Temps (NOTE: NOT MAT), in their software. Must be some crazy engineers with nothing else to do. Then again, maybe, just maybe, they put the time into things, to get a better picture of how to use that info., to better model the calibration to match the engine's needs.
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Grumpy I just love your thought provoking comments! Here is my take on it. I will have to take an existing table then tune based on that table. You have to start somewhere right? Like I said I am not in an area where I will be seeing huge temp differences. If I relocate my MAT to make it a IAT I can take the relocated MAT table but I will still have to tune the VE. I now cannot use any automatic VE tuning tools like VEMaster or VEPhd without first at least checking for logged BLM differences in the MAT temps based on the table. In fact I cannot take the table on faith. I have to decide what temp I am going to use as a baseline. I cannot say tune my VE tables all summer because my MAT/IAT temps are within this range then wait until it gets real cold. In the mean time I will want to tune the table in between to get good numbers for those temps. I will not see the temp extremes that others will. My best scenario is to try to compare what I do see then take the rest of the table on faith. I am going to assume that the hottest days give me my most consistent results and I will tune 'down' from there. If I never see some temps I will have to use what is out there. I also just relocated my air filter from the TB to 'cold air' area. I am showing about a 3% increase in VE from this. I am going to go back and check the temp difs and use this as my first baseline.
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Yea, provoking....
It appears I have to search for the same thing more than once as well as read things more than once.
Still haven't found the log that shows the 2 different sensors.
Here a little info
https://www.thirdgen.org/techbb2/sho...hreadid=136007
It appears I have to search for the same thing more than once as well as read things more than once.
Still haven't found the log that shows the 2 different sensors.
Here a little info
https://www.thirdgen.org/techbb2/sho...hreadid=136007
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Originally posted by 69 Ghost
Grumpy I just love your thought provoking comments!
I will have to take an existing table then tune based on that table. You have to start somewhere right? Like I said I am not in an area where I will be seeing huge temp differences.
If I relocate my MAT to make it a IAT I can take the relocated MAT table but I will still have to tune the VE.
I now cannot use any automatic VE tuning tools like VEMaster or VEPhd without first at least checking for logged BLM differences in the MAT temps based on the table.
In fact I cannot take the table on faith. I have to decide what temp I am going to use as a baseline.
Grumpy I just love your thought provoking comments!
I will have to take an existing table then tune based on that table. You have to start somewhere right? Like I said I am not in an area where I will be seeing huge temp differences.
If I relocate my MAT to make it a IAT I can take the relocated MAT table but I will still have to tune the VE.
I now cannot use any automatic VE tuning tools like VEMaster or VEPhd without first at least checking for logged BLM differences in the MAT temps based on the table.
In fact I cannot take the table on faith. I have to decide what temp I am going to use as a baseline.
First off you want to want to *see* the air temp., as it goes past the intake valve, so that in that reguard, you want a MAT. Seeing an artifically low temp., doesn't do you any good.
Set the Inverse table at whatever temp., you're working at that day. If the MAT is 30dC, then just use that value for all the other temps.. Then tune as you normally do. Then during cold starts, see how far off your correction is from what is commanded. Then correct that entry in table. Slowly but surely, you'll get to where you can fill in the table. It's not like a VE table where you can hammer on it all day long, just one or two entries every coule of days. As you get familiar with it, then you can start looking at your notes, and see what the trends are.
It all takes time. As you gain experience, and familiarity, it gets much (much) faster.
FWIW, I use my *VEmaster* Last!. IMO, something like that is for doing the final little tweaks.
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Grumpy now that we are into the meat of things. A few questions on direction. First of all I am using a 180 degree thermostat. Should I assume that this is where my table flat lines? I was looking at both the IMAT tables and I one is related to temp but it flatlines at 190-195 degree region. I am assuming that my steady state can be as low as about 176 for my thermostat. Next question there was some mention as to tune both tables. I can tune for the temp but how do I tune for the other table and how do I know? Last question I currently have my setup as a MAT. What I did was take a plastic LT1 IAT and 'thread' to put into a 3/8" NPT hole. I did this because I did not have my cold air box setup. I think you would recommend that it remain as is but what if I do relocate it? I am a bit concerned about breaking the plastic housing on it in the future.
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Originally posted by 69 Ghost
Grumpy now that we are into the meat of things. A few questions on direction. First of all I am using a 180 degree thermostat. Should I assume that this is where my table flat lines? I was looking at both the IMAT tables and I one is related to temp but it flatlines at 190-195 degree region. I am assuming that my steady state can be as low as about 176 for my thermostat. Next question there was some mention as to tune both tables. I can tune for the temp but how do I tune for the other table and how do I know? Last question I currently have my setup as a MAT. What I did was take a plastic LT1 IAT and 'thread' to put into a 3/8" NPT hole. I did this because I did not have my cold air box setup. I think you would recommend that it remain as is but what if I do relocate it? I am a bit concerned about breaking the plastic housing on it in the future.
Grumpy now that we are into the meat of things. A few questions on direction. First of all I am using a 180 degree thermostat. Should I assume that this is where my table flat lines? I was looking at both the IMAT tables and I one is related to temp but it flatlines at 190-195 degree region. I am assuming that my steady state can be as low as about 176 for my thermostat. Next question there was some mention as to tune both tables. I can tune for the temp but how do I tune for the other table and how do I know? Last question I currently have my setup as a MAT. What I did was take a plastic LT1 IAT and 'thread' to put into a 3/8" NPT hole. I did this because I did not have my cold air box setup. I think you would recommend that it remain as is but what if I do relocate it? I am a bit concerned about breaking the plastic housing on it in the future.
Since you asked.....
Suppose your starting with a table like this:
LInvCoolBpw:
;-----------------------------
; ; val ; oC
;-----------------------------
FCB 216 ; -40
FCB 204 ; -28
FCB 195 ; -16
FCB 186 ; -4
FCB 178 ; 8
FCB 171 ; 20
FCB 164 ; 32
FCB 158 ; 44
FCB 152 ; 56
FCB 148 ; 68
FCB 145 ; 80
FCB 141 ; 92
FCB 138 ; 104
FCB 134 ; 116
FCB 131 ; 128
FCB 129 ; 140
FCB 127 ; 152
Now say you're going to start tuning on an 75dF day (~25dC), you then rewrite it to look like this.
LInvCoolBpw:
;-----------------------------
; ; val ; oC
;-----------------------------
FCB 216 ; -40
FCB 204 ; -28
FCB 170 ; -16
FCB 170 ; -4
FCB 170 ; 8
FCB 170 ; 20
FCB 170 ; 32
FCB 170 ; 44
FCB 170 ; 56
FCB 170 ; 68
FCB 170 ; 80
FCB 170 ; 92
FCB 170 ; 104
FCB 170 ; 116
FCB 170 ; 128
FCB 129 ; 140
FCB 127 ; 152
That way you can with a moderately warm engine do a nice long data log, and try to avoid heatsoaking the engine, and maintaining a MAT of 75dF. If your MAT is typically say 80dF the use the entry that best reflects that temp. zone.
Now once you fix your VE tables, go ahead, and reenter the original values, and see how things look.
If you see a GENERAL TREND, that at a given MAT, it's rich or lean, then correct the Inverse table. If you see a huge *error* then, closely inspect all of your tune to see what you've missed.
In going from the 91 58 code to the 05 gas, and all new code, the variances I found tended to be rather small, except at the extreme high temps., but the original code wasn't intended to be run at those high of temps.. You might also even see where the aromatic temp differences from summer to winter gas move, once you get good at this.
Again, it takes time and practice to get something like this right. If you *miss* it, or aren't sure of yourself, there's no penalty in just starting over.
Pipe threads are self tightening, ALMOST everyone overtightens them. A good clean pipe thread, hardly needs to be more then finger tight. I use a wrench, and just go snug, and at over 24 PSI have had 0 *fuel stains* from a pipe thread leaking, and I don't recall ever having a vac leak at a pipe thread. Again, things need to be clean, and have good threads. Less then that, and **A** layer of teflon tape should do the trick.
Last edited by Grumpy; Oct 24, 2005 at 06:40 PM.
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