Here's how temperatures affect timing advance
12-23-2014, 08:32 AM
#1
Melting Slicks
Thread Starter
Here's how temperatures affect timing advance
I have a 2015 Z06 tune file. Here are two snippings of what happens to timing advance with temperature. There are multiplier tables that add or subtract from these values but this is the two main tables.
I think there is some timing reduction that owners are experiencing. As an example with IAT (Intake air temperature) my 2013 CTS-V will get up to 145* plus on a 45-50* night just idling in the staging lanes. And even higher with boost. Engine coolant temperature when allowed to idle it gets up to 229* with stock fan settings. Moving at freeway speeds I only see about 192-194 on a cool night. I run my fans manually via my HPT controls in the staging lanes and temps become much lower.
I think there is some timing reduction that owners are experiencing. As an example with IAT (Intake air temperature) my 2013 CTS-V will get up to 145* plus on a 45-50* night just idling in the staging lanes. And even higher with boost. Engine coolant temperature when allowed to idle it gets up to 229* with stock fan settings. Moving at freeway speeds I only see about 192-194 on a cool night. I run my fans manually via my HPT controls in the staging lanes and temps become much lower.
12-23-2014, 08:36 AM
#2
Team Owner
Do you know what the thermostat is set for on the C7 Z06? I've seen several people post for a Stingray that they normally run 210-220 degrees.
On my C6 Z06 I can run across Kansas at 90 MPH on a 105 degree day and run 192 degrees coolant.
On my C6 Z06 I can run across Kansas at 90 MPH on a 105 degree day and run 192 degrees coolant.
12-23-2014, 08:48 AM
#3
Melting Slicks
Thread Starter
I don't know Joe what temperature the Z06 thermostat maintains. I would assume it has an 86 C just like my CTS-V but don't know for sure. I haven't had this Caddy long enough to give it a test in heat on the highway. It may run the same as your C6 Z06 but don't know yet.
12-23-2014, 08:58 AM
#4
Safety Car
FINALLY. Someone started a technical thread so that we could discuss this, instead of labeling it an excuse. Thanks for posting the tables.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
12-23-2014, 09:38 AM
#5
Burning Brakes
FINALLY. Someone started a technical thread so that we could discuss this, instead of labeling it an excuse. Thanks for posting the tables.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
Finally we have something to look at.
timing pull at 212' seems very reasonable. The question is, with the Supercharger, are AIT's really hitting 250?!?! We need datalogger numbers too.
12-23-2014, 10:23 AM
#7
Former Vendor
The IAT's are actually very good. They take a while to come back down if the car has been sitting but once in motion IAT's will actually -decrease- a few degrees at wide open throttle.
The problem in my opinion is the knock sensors are hyper sensitive (I was logging 8-10deg of knock almost any time you breath on the gas pedal and also at WOT) and after the first few times you go WOT, commanded air fuel goes ultra rich.
At least that's what I found with our car hot lapping it around the shop. It was only around 40deg that day so temperatures may be more of an issue when ambient temps are higher but for now it seems to be just an ultra conservative tune.
The problem in my opinion is the knock sensors are hyper sensitive (I was logging 8-10deg of knock almost any time you breath on the gas pedal and also at WOT) and after the first few times you go WOT, commanded air fuel goes ultra rich.
At least that's what I found with our car hot lapping it around the shop. It was only around 40deg that day so temperatures may be more of an issue when ambient temps are higher but for now it seems to be just an ultra conservative tune.
12-23-2014, 10:27 AM
#8
It seems like 5 to 7 degrees pulled out at operating temps. Assuming timing is set mid 20s at WOT, you are looking at mid to low 10s for timing which could explain the drop in performance when things get heated.
It would be interesting to hear from a tuning expert.
It would be interesting to hear from a tuning expert.
12-23-2014, 10:38 AM
#9
Former Vendor
What would you like to know?
When cool you are seeing mid 20's for commanded timing (minus 8-10 deg of knock which seems to be consistent).
A few less when the temps start to climb.
Our car once tuned felt much more consistent on back to back runs as fueling was consistent and knock sensors were less aggressive but I have not done any back to back timed acceleration of stock vs tuned as it's too cold to get traction in the lower gears.
When cool you are seeing mid 20's for commanded timing (minus 8-10 deg of knock which seems to be consistent).
A few less when the temps start to climb.
Our car once tuned felt much more consistent on back to back runs as fueling was consistent and knock sensors were less aggressive but I have not done any back to back timed acceleration of stock vs tuned as it's too cold to get traction in the lower gears.
12-23-2014, 10:54 AM
#10
Melting Slicks
Thread Starter
The IAT's are actually very good. They take a while to come back down if the car has been sitting but once in motion IAT's will actually -decrease- a few degrees at wide open throttle.
The problem in my opinion is the knock sensors are hyper sensitive (I was logging 8-10deg of knock almost any time you breath on the gas pedal and also at WOT) and after the first few times you go WOT, commanded air fuel goes ultra rich.
At least that's what I found with our car hot lapping it around the shop. It was only around 40deg that day so temperatures may be more of an issue when ambient temps are higher but for now it seems to be just an ultra conservative tune.
The problem in my opinion is the knock sensors are hyper sensitive (I was logging 8-10deg of knock almost any time you breath on the gas pedal and also at WOT) and after the first few times you go WOT, commanded air fuel goes ultra rich.
At least that's what I found with our car hot lapping it around the shop. It was only around 40deg that day so temperatures may be more of an issue when ambient temps are higher but for now it seems to be just an ultra conservative tune.
IAT2 will increase rapidly at WOT. When air is compressed it goes up in temperature. Once back to steady driving with no boost the temperature will drop. And too this is related to how well the heat exchanger and intercooler function and are matched to the supercharger.
IAT2 is air temperature coming directly from the supercharger and going into the heads. IAT1 is the air temperature the Mass air meter is reading.
12-23-2014, 11:08 AM
#12
Request to posters
There are a lot of folks who are going to want to follow this discussion, most of whom are not tuners, or versed in the thermodynamics of internal combustion engines. That can't happen if the tuners talk to each other without explaining their comments to the rest of us. So please:
Define terms that tuners understand but the rest of us don't (i.e., "spark airmass");
Be clear about what you are discussing (i.e., "Our car once tuned felt much more consistent on back to back runs ..." -- What kind of car? Tuners now have the C7Z and its timing tables, and the weather is currently cold for most of us, but one poster was describing his CTSV, then another poster replied referencing "our car." So is "our car" a C7Z that's been doing back to back runs somewhere? In the cold?)
Sorry, I will plead ADHD, or just plain density, but like Tony said, this is going to be an important thread.
Thanks.
Define terms that tuners understand but the rest of us don't (i.e., "spark airmass");
Be clear about what you are discussing (i.e., "Our car once tuned felt much more consistent on back to back runs ..." -- What kind of car? Tuners now have the C7Z and its timing tables, and the weather is currently cold for most of us, but one poster was describing his CTSV, then another poster replied referencing "our car." So is "our car" a C7Z that's been doing back to back runs somewhere? In the cold?)
Sorry, I will plead ADHD, or just plain density, but like Tony said, this is going to be an important thread.
Thanks.
12-23-2014, 11:16 AM
#13
Former Vendor
Thanks for the lesson, I'm well aware of the difference between IAT1 and IAT2.
IAT2 on a C7Z decrease by a few degrees at wide open throttle.
This is the case on the dyno and the few runs I did on the street though I'm sure at some point (in warmer weather) temps would increase.
Here is the 5th back to back wot pull on this log. What do you see IAT2 doing?
Even if for some reason IAT1 and IAT2 pids are reversed (which I haven't tested), there certainly isn't a problem with intake air temp at this point.
IAT2 on a C7Z decrease by a few degrees at wide open throttle.
This is the case on the dyno and the few runs I did on the street though I'm sure at some point (in warmer weather) temps would increase.
Here is the 5th back to back wot pull on this log. What do you see IAT2 doing?
Even if for some reason IAT1 and IAT2 pids are reversed (which I haven't tested), there certainly isn't a problem with intake air temp at this point.
Last edited by INTMD8; 12-23-2014 at 11:19 AM.
12-23-2014, 11:20 AM
#14
Tech Contributor
Member Since: Oct 1999
Location: Charlotte, NC (formerly Endicott, NY)
Posts: 40,087
Received 8,927 Likes
on
5,332 Posts
FINALLY. Someone started a technical thread so that we could discuss this, instead of labeling it an excuse. Thanks for posting the tables.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
The IAT timing pull doesn't look bad at all, which echoes what the tuner shops have stated regarding the IAT readings being good on their pulls. Doesn't appear that IAT is driving the issue here.
Coolant temps could benefit a lot from adding a 180F thermostat. Most factory cars run at around 200F, to get better emissions levels. But, at the detriment to performance. But, even at 212F, only losing 3 degrees timing isn't horrible. That might be 15-20 hp, which is backed up by the dyno tests that have been done. Even at that power drop, the LT4 is still making the rated 650 crank hp.
Good info, but really no new news here. Thermostat and turning the fans on earlier will keep these cars running much cooler, until it gets hot outside.
A lower thermostat only reduces coolant temps on cars that have sufficient cooling capacity for the energy being dissipated. If you only run the car for in quarter mile runs or several dyno runs with some idling or off periods between the runs a lower thermostat along with a reduced fan turn on temp may reduce coolant temps.
However, 10 minutes of wide open throttle under max load will vastly increase the heat to be dissipated and the only limiter of coolant temp is radiator capacity. If you are on track with a coolant temp of 230 degrees and oil temps pushing 300 degrees while running at 160 mph it doesn't really matter whether or not you have a 160 degree thermostat or a 186 degree one.
Before I added a Ron Davis Racing radiator to my 03Z06 I saw 230 degree coolant temps with 319 degree oil temps after running for 30 minutes on a hot track day. That was with a stock 86 deg C (186 deg F) thermostat. Just changing the radiator reduced the coolant temps to 200 and oil temps to 220.
Bill
12-23-2014, 11:22 AM
#15
Subscribed. So what's the current hypothesis on why the car is slowing down so substantially? It's normal for all cars to pull timing when they heat up, but I keep coming back to the Road Atlanta peak speeds of only 153. Very slow for 650 horse.
12-23-2014, 11:24 AM
#16
A lower thermostat only reduces coolant temps on cars that have sufficient cooling capacity for the energy being dissipated. If you only run the car for in quarter mile runs or several dyno runs with some idling or off periods between the runs a lower thermostat along with a reduced fan turn on temp may reduce coolant temps.
However, 10 minutes of wide open throttle under max load will vastly increase the heat to be dissipated and the only limiter of coolant temp is radiator capacity. If you are on track with a coolant temp of 230 degrees and oil temps pushing 300 degrees while running at 160 mph it doesn't really matter whether or not you have a 160 degree thermostat or a 186 degree one.
Before I added a Ron Davis Racing radiator to my 03Z06 I saw 230 degree coolant temps with 319 degree oil temps after running for 30 minutes on a hot track day. That was with a stock 86 deg C (186 deg F) thermostat. Just changing the radiator reduced the coolant temps to 200 and oil temps to 220.
Bill
However, 10 minutes of wide open throttle under max load will vastly increase the heat to be dissipated and the only limiter of coolant temp is radiator capacity. If you are on track with a coolant temp of 230 degrees and oil temps pushing 300 degrees while running at 160 mph it doesn't really matter whether or not you have a 160 degree thermostat or a 186 degree one.
Before I added a Ron Davis Racing radiator to my 03Z06 I saw 230 degree coolant temps with 319 degree oil temps after running for 30 minutes on a hot track day. That was with a stock 86 deg C (186 deg F) thermostat. Just changing the radiator reduced the coolant temps to 200 and oil temps to 220.
Bill
I wonder if stuffing a bigger radiator and exchanger for the supercharger would do enough to keep the car out of the "pull power" zone with the stock tune.
12-23-2014, 11:27 AM
#17
Former Vendor
12-23-2014, 11:30 AM
#18
Melting Slicks
Thread Starter
Thanks for the lesson, I'm well aware of the difference between IAT1 and IAT2.
IAT2 on a C7Z decrease by a few degrees at wide open throttle.
This is the case on the dyno and the few runs I did on the street though I'm sure at some point (in warmer weather) temps would increase.
Here is the 5th back to back wot pull on this log. What do you see IAT2 doing?
Even if for some reason IAT1 and IAT2 pids are reversed (which I haven't tested), there certainly isn't a problem with intake air temp at this point.
IAT2 on a C7Z decrease by a few degrees at wide open throttle.
This is the case on the dyno and the few runs I did on the street though I'm sure at some point (in warmer weather) temps would increase.
Here is the 5th back to back wot pull on this log. What do you see IAT2 doing?
Even if for some reason IAT1 and IAT2 pids are reversed (which I haven't tested), there certainly isn't a problem with intake air temp at this point.
I see what your log shows. Sure different than what my CTS-V log indicates.
12-23-2014, 11:31 AM
#19
Safety Car
Those logs look good above. IAT2 or IAT1 do not seem to be an issue with this car. I'd take INTMD8's response, about Knock Retard, causing the main timing pull. But, you also have to be very careful when you alter those tables, and trust your fuel source. Also, I'd hope the driver has a good ear at detecting ping/knock when driving at WOT. Those alterations would certainly void your powertrain warranty. The good tuner shops deal with this daily, so pick your tuner wisely. Speed Inc is a good one!
12-23-2014, 11:32 AM
#20
Tech Contributor
Member Since: Mar 1999
Location: Northern VA
Posts: 10,063
Received 3,803 Likes
on
1,143 Posts
"Ask Tadge" Producer
