Heat Soak - Some DashHawk Log Data

[phantom6294]

Folks -- Still relatively new to the forums, the MS3, and the Mazda community as a whole (I've had my MS3 since July 1st). I got a DashHawk yesterday as my birthday present from my wife. I've read several threads debating the effect of heatsoak and how quickly the engine bay and the intercooler would become heat soaked and how quickly they would shed that heat once the car is moving again. So, since my wife is gone for the weekend, figured I would do some driving (that can't ever be a bad thing in a MS3!) and some data logging. This is just my attempt to contribute to the community. If I made some glaring errors, by all means, please speak up -- I certainly want to present accurate information so we can have a useful discussion and come to meaningful conclusions.

So, my tools were:
- 2008.5 MS3 GT Stock
- DashHawk v2 (v2.5 Final software/firmware)
- One lead foot
- Some premium gas
- Lots of patience to sit still in a MS3 for 12+ minutes

What I logged:
- Act AFR (not displayed on graph)
- IAT --> Pre Turbo Air Temp (right?)
- Boost Air Temp --> Post Turbo/Post Intercooler Air Temp (right?)
- Vehicle Speed
- Boost / Vacuum
*Note: It appears that the 'Ambient Air Temp' sensor in the DashHawk is the same as IAT and as such, was not used/logged -- Ambient Air Temp was being reported as 80F during idle on the dash and dropped to 79F shortly after starting to move

My method:
- Drove around on the interstate with some (safe) boosted runs to get the engine/engine bay/turbo heated up (About 16 Miles / 20 Minutes total before coming to idle of which 14 miles were interstate)
- Started logging about 1 minute before coming to a stop
- Parked the car, turned off the A/C, and let it idle
- My plan was to idle until IAT and Boosted Air Temps leveled off *OR* the DashHawk reached 65% of its memory capacity for the log ***I ended up reaching 65% before it seemed like the temps leveled off
- Quickly (but safely) returned to highway speeds
- Monitor how long it took for IAT and Boosted Air Temp to return to pre-idle temps

So, here is a break down of the data, followed by three screen shots in the data logger on my PC; 1) leading up to idle, 2) idle period, and 3) post-idle period. Times are given referenced to the start time of data logging.

- Ambient Temp 80F/79F
- Pre-Idle IAT: 86F
- Pre-Idle Boost Air Temp: 115F
- Start time of Idle: ~115 Seconds (1 Minute 55 Seconds)
- End time of Idle: ~870 Seconds (14 Minutes 30 Seconds)
- Total time of Idle: 12 Minutes 25 Seconds

- IAT / Boost Air Temp 1 Minute after complete stop: 93F / 131F
- IAT / Boost Air Temp 2 Minutes after complete stop: 98F / 137F
- IAT / Boost Air Temp 3 Minutes after complete stop: 102F / 144F
- IAT / Boost Air Temp 5 Minutes after complete stop: 109F / 150F

- Maximum recorded IAT: 143F
- Maximum recorded Boost Air Temp: 187F

- IAT / Boost Air Temp once vehicle at 40MPH (Time: 890 Seconds, ~2 Minutes after moving): 123F / 173F
- IAT / Boost Air Temp once vehicle at 70MPH (Time: 927 Seconds, ~3 Minutes after moving): 109F / 154F

- IAT / Boost Air Temp 1 minute after continuous movement: 107F / 152F
- IAT / Boost Air Temp 2 Minutes after continuous movement: 96F / 138F
- IAT / Boost Air Temp 3 Minutes after continuous movement: 89F / 129F

- Time when pre-idle IAT (86F) was reached: ~1115 Seconds (~4 Minutes after moving again)
- Time when pre-idle Boost Air Temp (115F) was reached: Did not reach pre-idle temps --> lowest Boost Air Temp post-idle was 125F

Graphs:

Note: The colors of the graph lines DO NOT COMPLETELY MATCH the axis values. Since IAT (yellow graph line) and Boost Air Temperature (blue graph line) use the same temp scale, they are both using the yellow axis scale. Vehicle Speed (magenta graph line) is using the blueaxis scale, and Boost (cyan graph line) is using the magenta axis scale. Yes, I know it is very confusing. Sorry, I was focused on the post, not making the graph pretty.

Also, I realize they are large (dimension-wise) but I hope to make them easily readable so people don't have to take my word on the values.

Conclusions:

I guess I should say first that this is just one set of data and is by no means conclusive. I think though it is a good start and some basic conclusions can be drawn from the data I have so far. Also, 12 minutes is a long time to be idle in every day driving. I did this mostly to get idea if/when the temps would reach a maximum point; they did not. As such, one might argue that the engine bay and/or the intercooler were not yet 'heat soaked' as they were still heating up. I'm not a physics expert though...

I decided to let others make their own conclusions or let the conclusions be reached during discussions. So, talk amongst yourselves!!!

Random Observations:

I found that when you get into a boosted situation, the Boost Air Temp takes a sudden dive in temps (should be visible in graph screen shots). I hit about 5PSI and the temps dropped from 130F to 110F but then the Boost Air Temp returned to just shy of 130F once off boost. This seems counter-intuitive to me -- boosted air should be hotter than non-boosted air. My only guess would be that where ever the Boost Air Temp is being read is being affected by a heat soak condition and the air is actually cooler than is being recorded. Once the boost and higher air flow comes on, the higher flow rate over the sensor cools it off??? I dunno...

Future Test(s)?:

Obviously a 12+ minute idle time is a LONG time to sit idle for every day driving -- a 12+ minute stop light would be killer! It would be interesting to see if the temps come back to normal proportionally quicker if the engine bay and intercooler aren't as 'heat soaked.' For example, 1 minute of idle takes 15 seconds to cool, 2 minutes takes 45 seconds to cool, 3 minutes takes 1.5 minutes, etc. I would also like to do some much longer interstate runs (30+ minutes minimum, preferably 1+ hour) to see how the temps do at highway cruise speeds.) On the flip side, I'd like to see how the temps drop with lower cruising speeds -- such as <50 M.P.H., in both continuous driving and after a 'heat soak' condition. Another interesting test might be to get the car hot (give it a quick turbo cool down) then shut it off and let it sit for varying amounts of time and see what the temps look like when the car is started back up.

I have no plans to get a FMIC, but it would be interesting to compare too similar cars (sans the intercoolers) and see the differences between TMIC and FMIC in heat soak conditions, cruising speeds, etc.

 

[freebird_78]

Nice testing methodology. I'd like to see if/when you get a CAI and/or TMIC or FMIC.

The drop in temp with rise in boost is easy to explain. It's all about convective cooling. When at idle, or under no boost, there is very little airflow inside the intercooler. The airflow through the exterior of the intercooler is the only convection occuring, but radiant heating heats both inside and out of the intercooler. Therefore, even though you have some airflow through the exterior of the intercooler, you're really only cooling 1/2 of the thermal mass. Once you start building boost, the quantity of air flowing through the inside of the intercooler greatly increases and that air carries a lot of the heat in the intercooler.

You say it is counter intuitive, and if you think in terms of a lot of boost over a long period of time, it is. We all know the ideal gas law (P=v*t) that says compressing air increases temperature, but with lower boost for shorter periods of time, I don't think the realively low compression will heat the air as much as the effect of radiant heat from underhood temps on the intercooler itself.

Now once you have high boost for a decent period of time, that compressed air becomes hotter than the combined radiant heating plus convective cooling on the exterior of the intercooler, therefore cooling the air charge.

 

[phantom6294]

Nice testing methodology. I'd like to see if/when you get a CAI and/or TMIC or FMIC.

Thanks! No plans to get a FMIC though -- more mod than I want to undertake. I am considering either the Cobb SRI or the MS CAI if they re-release it. I was thinking after I posted it would be interesting to compare temp data across stock airbox, SRI and CAI. It will all depend on how mod friendly my dealer ends up being -- I've got to get a long life out of this car and since I spent extra on an extended warranty, I will need to be careful not to jeporadize it.

 

[AutoXRacer]

I'm currently working on a project to completely heat wrap my engine...
See my thread at Mazda...speed...forums...org... turbo section.

The highest boosted temps I've seen/recorded were 189* at idle.

I'm hoping all this effort lowers my heat soak substancially... Great data though!!

 

[phantom6294]

This is a dup from another forum -- a member there inquired about IAT / BAT during 'everyday' driving so I ran some errands and logged the data.

Like I said... ask and ye shall receive...

Made a quick trip to Home Depot, about 3.5 miles from my house, speeds under 55 M.P.H. the whole way -- nothing aggressive at all. Ambient temp was reading as 82F; by the time I got home ambient temp was 86F -- so a bit warmer than my log from last night, but not drastically different. I was in Home Depot for maybe 45 minutes (I am a slow Home Depot shopper) and started logging once I got back in the car. I drove around and then headed to a Chik-fil-A to get lunch; I went through the drive through then ate in my car. I then reversed my route, heading home. I stretched the log viewer window out pretty big to make it more readable. As such, I will post the images as links so people don't get hammered with large images.

First image (first_log.png) is from Home Depot to Chik-fil-A in the drive-thru. I ran out of memory on the first log, so I started logging again -- maybe a 5 second max break between images. Second image (second_log.png) is idling while I eat, then the return trip home. I ran out of data space on the second log not far from home, so I didn't bother starting another new log. Also, it occured to me that AFR doesn't really seem to add much to the log, so I switched the second log to log RPM instead of AFR. However, neither AFR/RPM are displayed (doesn't seem to add much). There's really nothing 'scientific' about these logs -- these are just logs of 'every day driving.' Also, the time scale on these are MUCH longer than my first -- please take that into account when viewing.

first_log.png
second_log.png
zoom_log_1.png

Observations:
- Even with just a quick trip to Home Depot, it seems the engine generates plenty of heat and the engine bay retains tons of said heat; no surprise to most of us. IAT and BAT (Boost Air Temp, tired of typing it out every time) are both pretty darn high when I get back to my car. This begs for a test to compare leaving the hood closed versus open to see how it affects things while the car is off.
- IIRC, several people had the opinion that as soon as you got moving again, temps would drop down again. Well, the third image (zoom_log_1.png) shows the roughly 1 minute of data after I started moving after finishing my lunch. Well, in roughly the first ten seconds after moving, IAT drops about 6F and BAT drops only 1F. Surprisingly, both peak AFTER I begin to move. I am going to guess that the radiator is pretty hot and initially as air flows over the radiator it brings in some extra heat into the engine bay -- but I'm just guessing. Obviously, as the log shows, my speeds don't get very high, and IAT / BAT do eventually shed 27F and 17F respectively within the first minute.

 

[Speed3Rookie]

Good stuff....thanks for sharing.

 

[Trader]

Phantom,

Great thread and good write up. I love to see people with real hard data as opposed to just opinions. Hopefully I can put some theory behind the numbers that you are seeing.

And as far as heat soak. I can talk from some personal experience. I drive a DSM. (Mitsubishi eclipse turbo)

I used to have a K&N cone air filter in the engine bay. With this configuration I would heat soak pretty bad. But once I moved the intake into the fender cavity the heat soak issues went away except on really hot days.

This ties well into the CAI vs SRI debate.

Anyways here is the theory behind this:

According to the Adiabatic Processes equations for a turbo charger and intercooler theory, the intake temperature will not only affect (and amplify) the temperature after the turbo it will affect the temperature after the intercooler, putting hotter air into your engine.

The intake temperature has a big affect on performance. If you are sucking air inside the engine bay you will work your intercooler alot harder resulting in heat soak.

Take a look at the link below:

http://www.stealth316.com/2-turbotemp.htm

Now lets enter some numbers- I used the following:

CAI numbers (assuming the following number from intake air NOT from engine bay)

Intake Temp = 70 degrees
Inlet pressure = 14 psi absolute (assume -.7 loss due to intake/pipe (14.7-0.7))
Outlet pressure = 16 psi (gauge)
Compressor efficiency = 65

So with this scenario you get a temperature after the turbo of 266 degrees F.

Intake located in Engine bay (Cobb configuration) SRI

Now lets assume you are getting air from the engine bay that is 100 degrees.

Intake Temp = 100 degrees
Inlet pressure = 14 psi absolute (assume -.7 loss due to intake/pipe (14.7-0.7))
Outlet pressure = 16 psi (gauge)
Compressor efficiency = 65

Now you get at temperature after the turbo of 307 degrees.

Is that 41 extra degrees going to heat soak your intercooler faster?? ...

YOU BET!!!!

But it gets worse because even before your intercooler heat soaks you are still getting hotter air at the intake manifold.

If you continue the calculation with the intercooler calcs assuming the following:

Intercooler efficiency = 75
IC pressure loss = 1 psi
Ambient Temp = 70 degrees

With a starting intake temperature of 70 degrees you get a intercooler outlet temp of 119 degrees. With sucking hot engine bay air of 100 degrees you end up with intercooler outlet temperature of 129 degrees.

So right off the bat you gain 10 degrees going into your engine, and this occurs even before your intercooler heat soaks. So this will get worse faster due to quicker heat soak with an intake that is sucking hot engine bay air.

Some other reading if you are interested:

http://www.gnttype.org/techarea/turbo/turboflow.html

http://www.stealth316.com/2-adiabat1.htm

 

[Betelgeuse]

First and foremost this is great info!! But the real question is how does this translate in terms of lost power to the wheels of an ms3? Only testing each scenario (Cai one day and then SRI the other) on the same dyno in the same conditions would garner any data that really matters imo. Also there is another aspect to SRIs to consider. Because they use a much shorter tube, they're less of a restriction than a CAI. That alone can negate any possible advantage a CAI might have in our case.

Having ran both back to back, I still prefer the SRI and felt absolutely no power loss when I switched. In fact the car felt better in the lower rpms.
So I'm still very skeptical about the effects of iat /boost temps with one as opposed to the other. If I can't feel it, then imo, it must not be that great. I think only some hard dyno data would end the debate for me.


Also I know the OP mentioned his speed wasn't high when he logged the iat/boost temps after driving, but that is a significant factor. In a situation where any of this would matter (like when taking off quickly from a stop), speed and airflow would be higher and temps would more than likely drop quicker.

 

[dkswim]

sub for future reading

 

[phantom6294]

First and foremost this a great info!! But the real question is how does this translate in terms of lost power to the wheels of an ms3? Only testing each scenario (Cai one day and then SRI the other) on the same dyno in the same conditions would garner any data that really matters imo. Also there is another aspect to SRIs to consider. Because they use a much shorter tube, they're less of a restriction than a CAI. That alone can negate any possible advantage a CAI might have in our case.

I couldn't agree more -- all the DashHawk data and graphs ultimately don't mean squat. The important part is power at the wheels. However, I would be surprised if a dyno is going to be fully capable of showing the difference, caused by heat soak / temperatures, between the CAI and SRI. It would take a very controlled environment to accurately replicate the airflow over a car as if it were being driven on the street.

Also I know the OP mentioned his speed wasn't high when he logged the iat/boost temps after driving, but that is a significant factor. In a situation where any of this would matter (like when taking off quickly from a stop), speed and airflow would be higher and temps would more than likely drop quicker.

Well, the first set of logs, I quickly got up to interstate speeds -- about 70 M.P.H. It took about 2 minutes 30 seconds after reaching 70 M.P.H. to reach the pre-idle IAT (albeit after a very long idle period).

The second set of logs was a bit more real life driving -- running errands around town. In that case, during one acceleration to about 60 M.P.H., there was a quick ~10F drop in IAT during that acceleration. However, rarely, does the IAT drop back to ambient temps.

So, I tried not to make too many hard and fast conclusions because "hot air" is a relative term -- when people say the SRI is 'sucking in hot air' it really depends on how they define 'hot air.' If 'hot air' is above ambient, then yes... it would seem an SRI is going to pull in 'hot air.' On the flip side, 'cold air' is also a relative term... because if it's 90F outside, the CAI won't be sucking in 'cold air.'

As I said, I don't have any aftermarket intakes with which to compare to the stock setup. It would seem the SRI is deeper in the engine bay than the stock intake so one could make the argument it will see higher temps than the stock -- I just can't do any comparisons at this point. I would certainly love to spend a weekend comparing IATs and BATs between the Stock / SRI / CAI and Stock TMIC / upgraded TMIC / and FMIC. I just don't have the money to buy all of these for the sake of science.

In the end, my goal is to provide some baseline data and hopefully spark some good discussion about heat soak, SRI vs CAI, etc, etc.

 

[15min5k]

First and foremost this is great info!! But the real question is how does this translate in terms of lost power to the wheels of an ms3? Only testing each scenario (Cai one day and then SRI the other) on the same dyno in the same conditions would garner any data that really matters imo. Also there is another aspect to SRIs to consider. Because they use a much shorter tube, they're less of a restriction than a CAI. That alone can negate any possible advantage a CAI might have in our case.

Having ran both back to back, I still prefer the SRI and felt absolutely no power loss when I switched. In fact the car felt better in the lower rpms.
So I'm still very skeptical about the effects of iat /boost temps with one as opposed to the other. If I can't feel it, then imo, it must not be that great. I think only some hard dyno data would end the debate for me.


Also I know the OP mentioned his speed wasn't high when he logged the iat/boost temps after driving, but that is a significant factor. In a situation where any of this would matter (like when taking off quickly from a stop), speed and airflow would be higher and temps would more than likely drop quicker.

Exactly all these BS talks about the Cobb SRI "sucking in hot engine bay air" is just stupid! The only time itll be "sucking in hot engine bay air" is at idle when if you give it some throttle. Once the car is in motion air is being directed in the engine bay cooling it down (Its not hot anymore) Also, with a SRI you get better throttle response along with the benefits of easy installation and ease of cleaning. With a CAI you get a long ******* metal tube that takes longer to install, harder to get to for cleaning the filter and hot temps from the metal tube its made out of (yes metal conducts heat) Theres already been plenty of people that have tried both (CAI & SRI) with the MS3 and pretty much everyone of them say they prefer the SRI and or didnt notice a damn difference. Why in the hell is this debate still going on??

 

[phantom6294]

Why in the hell is this debate still going on??

Like I already said, 'hot air' is a relative term. What do you mean when you say hot air? My second set of logs shows at one point that even during every day driving and accelerating to 60 M.P.H., the IAT was still above 105F when ambient was mid-80F; a delta of 20F. So, that seems to show that the hot air in the engine bay isn't immediately and completely flushed out just because you get back up to speed -- but it all depends on how 'hot air' is defined. Is 20F above ambient 'hot air?'

In the original post, after an extend idle, it took more than 4 minutes after moving again (albeit 3 minutes after continous moving, 2.5 minutes after reaching 70 M.P.H.) to reach pre-idle IAT. 70 M.P.H is a pretty good speed and should certainly be providing plenty of fresh air into the engine bay.

So, the "debate" continues because we're using ambiguous terms and we have no data -- just opinions. Although, this thread's focus was not about debating between Stock / SRI / CAI, or TMIC / FMIC.

EDIT: Just to ensure everyone is aware... I am running the stock intake. If someone in the greater Baltimore area wants to loan me an SRI, let me use my DashHawk in their SRI / CAI equipped car, or post some data from a SRI, please, by all means! More data means more educated disucssions and decisions.

 

[60181]

I prefer CAI. No worries about air temps while rolling for sure and who wants to suck in all that hot air at every stop light awaiting the engine bay to cool down.

Like I already said, 'hot air' is a relative term. What do you mean when you say hot air? My second set of logs shows at one point that even during every day driving and accelerating to 60 M.P.H., the IAT was still above 105F when ambient was mid-80F; a delta of 20F. So, that seems to show that the hot air in the engine bay isn't immediately and completely flushed out just because you get back up to speed -- but it all depends on how 'hot air' is defined. Is 20F above ambient 'hot air?'

In the original post, after an extend idle, it took more than 4 minutes after moving again (albeit 3 minutes after continous moving, 2.5 minutes after reaching 70 M.P.H.) to reach pre-idle IAT. 70 M.P.H is a pretty good speed and should certainly be providing plenty of fresh air into the engine bay.

So, the "debate" continues because we're using ambiguous terms and we have no data -- just opinions. Although, this thread's focus was not about debating between Stock / SRI / CAI, or TMIC / FMIC.

EDIT: Just to ensure everyone is aware... I am running the stock intake. If someone in the greater Baltimore area wants to loan me an SRI, let me use my DashHawk in their SRI / CAI equipped car, or post some data from a SRI, please, by all means! More data means more educated disucssions and decisions.