Many still think the Fiero Engine Bay is always hot and needs extra cooling every time the car is running... Others think gets hot but Vents cool the car when moving.
Winner is Vents cools when moving. A lot of cooling too. But when parked after running the Temperature climbs fast even with rainy weather today.
IOW If you think you need fan(s) under the vents etc when running... Most fans are blocking air flow when off and parked car engine bay bakes everything at higher temps and longer time.Click to show
I did some testing for this 15+ years ago but limited probes and no cheap way to record thermocouples etc. Then someone bought me an "off brand" Arduino starting kit a couple months ago and while good, no much to do with most modules for me. (Is funny that Arduino forums label most others as counterfeit or worse but claim the product is "open source...") But Did come w/ some things like Real Time Clock then add more temperature and other options.
So made a basic data logger and tested temp in the cabin and near the DIS Duke air cleaner. Figure that is above ~1/2 of the exhaust and only area wires reach in a hurry. The thermistor size is less than a grain of most types of rice and hard to see in second image. Picture looking down and Thermistor is in front of the neck.
Short results of a quick test? Weather at start and next couple of hours: ~71°F Car moving, bay temp stays ~ 75°F. Slow down to a crawl to find parking? ~ 88°F When park at school... fast rise started at 96° and went up to 199° in ~ 17 minutes then slowly cooled off. When left and car is moving again Temp drops to 105-115° because engine is still warm an hour later. Got home and parked the peak was 192°F then cool down fully for 3+ hours.
I'll add other temp readings when I get time. Maybe I'll add air flow at one of the vents but cost money and don't see another use. (Yes can try using a fan as a input but then no-one believe them without reliable calibration.) Temp sensors are cheap and even when not, can use in a lot of other places. Want to add speed so I don't have to remember when temp rises/falls in Excel. I could tap 5v speed in the ECM and I can program other things but don't know C well and ArduinoIDE is a joke editor but others have their own issues so takes time to learn them. Search Google etc can help but many answers no longer exist or are complete junk making more problems like many YT "experts."
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Awesome project! Might have just found a use for my arduino and thermocouples I have laying around from college. Come to think of it I think I have a thermostat code saved somewhere...
The RTC was reset to compile time and I did't fix the time stamp. Fix the clock and capture data again today since I had another meeting at same place...
I still stand by the winner because Exhaust parts run 400-600°F and the thermistor was right above exhaust manifold with nothing to protect it.
So Driving the car had/have the peak temps but stayed under 200°F
Today... Starting today at ~85°F and mostly cloudy. Engine warm fast as usual but bay temps stayed in the rage of 150° to 195°F if the car is moving between 30 to 70MPH. Slower speed seems to like better cooling or power train just runs a bit hotter at 65-70MPG. Likely the later because TCC valve is bad and unplugged. When shutdown at school, the temp kept dropping to ~107° Drive home average peak was ~190°
Quick Excel Chart... 3 dropouts in T1 cabin is DHT22 not ready and I didn't remove those rows. T2 EB is Engine Bay temps but Signals from a thermistor w/o shielded leads get a lot of noise is why you see a line like above.
I'm using 100kΩ Thermistor rated to 300°F (the one on the breadboard is only 10kΩ.) I have several K type Thermocouples and MAX31856 Thermocouple Interface. The better chip has cold side compensation and Linearization built in to stay accurate w/o math processing by whatever. (Other older chips likely max31855 only have cold side.) For my quick data log test I didn't bother to install max module yet. Don't want to many things that could move around taking the kit in/out of car. worse this and SD are SPI and daisy chain modules are a big target of problems w/o having everything screwed down.
Side Note: If anyone is writing data logs for anything. Can ignore many twits how to format the data... I been using and programing data log programs/devices for decades and Most YT and other "experts" have no clue on how to use comma and other delimiters, format headers, etc. then confuse everyone else. Even the file name matters because many back end programs auto format the output file or not depending on 3 char extension.
Originally posted by sourmash: The air through the vents when moving, does it go upwards out the top of the deck?
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Originally posted by Patrick: Heat rises... no point trying to fight it.
Only 100% True when the car is parked. Air flow around/under the Fiero when car moving can do very odd things like ~1/2 of air can roll backward on the rear deck. If you parked under a tree, leaves and more can get trap behind rear window and in the vents. That is a pain in the a--- for many.
You need one that sees speed and flow direction. Most only sees speed... You can get very small MAF type units for arduino etc but can't tell direction. other mechanical units I've seen are made for Weather stations and are too big and wrong type for this use.
Some amp "chips"/modules have ±X amps 0-5V output w/ 0amps = 2.5v. Would need same setup or second output, in output data or pin output, to show direction.
The notch area behind the rear window creates a low pressure area which pulls the air up through the vents at speed. The underside and wheel wells of our cars are not quite like race cars which are designed to evacuate air and "suck" the car to the road. So, if you modify the body or underside to create more downforce by evacuating the air, creating low pressure, you can actually equalize the pressure above the vents and trap more heat in the engine bay. I think a few carefully placed barometers would give a much better picture of what is happening rather than monitoring temps which are influenced by way too many variables.
I grew up around aircraft....So I know something about aerodynamics (At least enough to be dangerous!)......What Ogre said about air doing odd things is true...The decklid air rolls backwards at certain speeds....And the spoiler helps lower the drag coefficient by keeping the air running straight off the deck.
My 73 mach 1 would float at 65-75....even though I had lowered the front by an inch.....ALL the air gets rammed under the hood- and then has nowhere to go...Hood area is 3000 square inches so 1/10 of PSI creates 300 lbs of lift! So I made an airdam that is open in front of radiator BELOW the bumper, with the sides angled back a bit, and a reverse angle lip at the bottom....and then I BLOCKED off the upper grill completely...The only air into the engine compartment was through the air dam under the bumper in the center.
Had that car up to 90+ passing 3 semis on H97 above Weed, CA....Solid as a rock! And no cooling problems (Vacuum behind radiator works better than high pressure in front (And behind) radiator!
As far as under-lid heat....The dang exhaust just kills the compartment.......Make sure your heat shields are good, and I actually removed the grates from under my vents to get better air flow.....But I never park under a tree- Ever!
Originally posted by ZCR1: The notch area behind the rear window creates a low pressure area which pulls the air up through the vents at speed. The underside and wheel wells of our cars are not quite like race cars which are designed to evacuate air and "suck" the car to the road. So, if you modify the body or underside to create more downforce by evacuating the air, creating low pressure, you can actually equalize the pressure above the vents and trap more heat in the engine bay. I think a few carefully placed barometers would give a much better picture of what is happening rather than monitoring temps which are influenced by way too many variables.
Funny that you mention this... Because found my spare MAP and plug and wired to the kit yesterday. Tested some and AD input for arduino makes it quite sensitive. I'm not calibrating this very much but can tell if there is a vacuum. I check w/ a better version of real Mighty Vac hand pump w/ a gauge and even a small faction of pulling handle you see the number change. I have to make longer wires etc to put all in the car again.
They make other "chips" for this but cost money to buy and spend too much already. Most are doing same job w/ same 1 bar limit as MAP but have I2C etc built into them like modules w/ MPL3115A2.
Even if there's little vacuum... Constant wind there will move air thru the vents. Air flow under the car can push up or suck down air in the bay too. These can't tell you what direction unless maybe you have several running at same time.
Every engine bay is hot when driven then open the hood so most just think they are hot all time time and guess hotter then real as well. Simple measurements tell this is not the case but most can't understand. I have more temperature probes but not in hurry to use them. I didn't cover that even on very cloudy the cabin temp is ~100°F parked at school. Less later because lower sun and building at home. I got DHT22 because has a higher working limits to test cabin temp on a clear day and next summer. Earlier quick tests w/ meat thermometers I saw 166°F on a clear day even tho weather was ~60-70°.
The notch area behind the rear window creates a low pressure area which pulls the air up through the vents at speed. The underside and wheel wells of our cars are not quite like race cars which are designed to evacuate air and "suck" the car to the road. So, if you modify the body or underside to create more downforce by evacuating the air, creating low pressure, you can actually equalize the pressure above the vents and trap more heat in the engine bay. I think a few carefully placed barometers would give a much better picture of what is happening rather than monitoring temps which are influenced by way too many variables.
I'm thinking that even just lowering a car can have an effect. I just ran the Georgia Fiero Club's RFTH event this weekend. A couple of guys had some temperature problems. Not bad problems. Not overheating, but still, they were running a little hot. Some were running with the dryer connector disconnected so they could run the cooling fan without running the compressor. My bone stock Formula, with stock wheels and stock sized tires, was rock solid, temperature-wise. I'm not sure that the others were lowered, but that might explain why they were running hotter than I was. Do 88's have better airflow? I had the only 88 V6 on the run.
[This message has been edited by Formula Owner (edited 09-17-2018).]
Can be a lot of things.... "Big" radiator (3 or more "cores" but rad close to same size), Fan(s) on all the time, and more are often band-aid fixes and hide the real problem.
While 88 have suspension changes, the ride height etc should by identical to all other years. So Having heat problems for OE and many engine swaps is often problems w/ coolant system and owners can't/won't fix them.
A "minor" bending of main coolant pipe(s) you may see can be a major problem to the cooling system and engine runs hot or over heats. People often have to remove both brackets under the rocker panels to look for damage but few actually does this. Battery up front changes tire wall to fit it... Changing the wall etc to do this may change air flow enough to cool the rad. Lower cars can screw up air flow too making any radiator to fail doing it's job. Missing/damage panel(s) in front of radiator can do same thing for cars w/ normal ride height. Just having crap blocking the AC condenser and/or Rad can cause big problems. Even owner believing the myth engine runs hot for whatever reason. Can be 2 or more of these examples and more at same time.
I have a question. Say, after a hard drive on some nice, curvy roads... you pull over for a rest stop. Is it a good idea to pop the deck lid to let the heat out?
I have two temperature sensors in my engine bay. I can pretty much validate what the Theorge has posted regarding engine bay temperatures.
I have a Digital A.C. system in my 86 GT. The A.C. head unit reads outside temperature. While I was making the installation I added sensors in the passenger compartment and engine area that are switchable.
[This message has been edited by Cajun (edited 09-18-2018).]
Is close to summer and I'll likely try same test on a hot day so I'm "bumping" this. Likely will try more temp sensors. A have different types already that can read engine and even the cat directly. (Typically Engine and Cat will spike then drop after shutdown. Engine has no coolant flow and cat has little/no air flow to cool the outside case after shutdown. Cat case temp can climb in slow/stop traffic too for same reason.) Will try to connect old MAP to read "vacuum" likely near the vents to see if has air suck or pushed thru vents. Air flow is more complicated because air is moving behind window but air is move under the bay and some is pushed up too so MAP reading may never mean much. I've seen other tools like could work but way too expensive to buy even used for 1 time use.
ETA--> Note above data is w/ "new style" vents w/ stamped louver metal sheet under them. Old style vents w/ hex screen allow more air flow but also allow more UV for Sun light to attack everything under them.
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Originally posted by Formula Owner: I have a question. Say, after a hard drive on some nice, curvy roads... you pull over for a rest stop. Is it a good idea to pop the deck lid to let the heat out?
Sorry I missed your post... Is often not needed but won't hurt either for most cars. Fiero is an "odd ball" with vents for engine bay and moves a lot of air even w/ the car stopped. IOW does same but less air flow as opening the "hood" as shown above... Near 200°F running drops fast to 150° and keep dropping when parked. Most other vehicles have little to no convection when their stopped because of the hood designs not allowing air to move.
[This message has been edited by theogre (edited 05-20-2019).]
For what its worth, on my SD4 engine I have engine air intake connected to a K&N Cone style air filter located inside the engine bay near the area of the stock air intake/scoop. The scoop is not connected to anything but dumps its air very near the filter. However filter is also near the exhaust piping. In other words there is potential for both cool or hot air to be sucked into the intake. I have a intake air temp sensor feeding the updated ECU. The air temp typically starts out around 10 degrees warmer than than ambient air and increases to around 30-35 degrees above air temp as the engine gets up to full temperature. So just sharing another data point that it does not get overly hot in the engine bay.
I have a question. Say, after a hard drive on some nice, curvy roads... you pull over for a rest stop. Is it a good idea to pop the deck lid to let the heat out?
The heat will get out the two big vents fast enough IMO. One thing I did on one Fiero was remove the lower grill that is in the vent, air flows faster now. But yeah don't park under trees/etc then (which I don't) because more debris can fall in, the good thing is you can get it out, because it isn't stuck between the outer and inner vent grills.
I have thought about modifying my vents but I have not run into any heat problems with my car as of yet. I do have a bigger 3 row aluminum radiator, the fan never comes on unless I am using the AC
Not Fiero but Arduino reply. The Micro Center Inland brand stuff (Mega) is $10.00. made well and has run enough sketches without error for me to get bored with it. A few weeks I might try my hand at some stm32 series stuff. Cheap blue pill(stm32f103c) and stm32f407vet. They both have native ADCs like Arduino but the libraries are not as broad as Arduino. For the price, memory and speed, I have to at least try. The last time I had ventured into this stuff was Basic on a Commodore Vic 20. 40 years ago, yeah forgot that stuff. The younger ones have no idea how fortunate they are.
Hot and bored so I'm running my data logger again today to see how hot the cabin will get parked in the sun. Right now the Black Fiero have windshield Mylar shield and "tin foil" under sunroof to reflect heat out but was still pushing 110°F just to put the thing in the car at ~ 10:00 am. The logger is on the driver side floor in shade w/ DHT22 and thermistor hook to RV Mirror to try to see low and high temps. Outside temp is 90° w/ HI 103° right now via local real weather station on a net maintain by local university under state gov.
(I use 2 cheap tin Oven floor shields under the sunroof. Easy to fit and don't care when wreck for whatever reason.) Why? Many MSM and local new outlets scream cabin temp kills kids etc very easy and while is sadly very true many publish "low" temps like "only" 120-130°F. Years ago Pediatrics publish a paper basically saying 130°F was easy to hit in just minutes and so I did quick test w/ cheap non recording thermometer and saw 160°F in the car on 60° day. IOW (I posted such back them but not search PFF archives.) So today I'll see how hot the car gets in a day because many "forget" their kids for Hours in cars. Then maybe try next day w/o the mylar etc to reflect sun light. That's if the logger or battery doesn't die w/ high heat. Most normal electrics don't like operating > 150°F air temp.
ETA-->@ 2:00pm now air temp 93° HI 105°
[This message has been edited by theogre (edited 07-17-2019).]
T1 was temp on the Floor. Max was 115°F T2 was temp at RV mirror. Max was ~ 143°F max ~ 3pm and that's with windshield and sunroof shields. Max ambient reported: 95°F at 5pm
Later clouds cut higher temp but even when sun went down and got rain after ~ 7pm did not cooled quickly. Was a bit surprise the Relative Humidity dropped so much as temp climbed. Couple data dropout because DHT22 wasn't ready and didn't bother to remove those rows.
Again T2 is just simple Thermistor. setup is very dumb but reads fast and unshielded so gets E noise and while not in direct sun every even small clouds can effect cabin temp some in seconds. So T2 looks like that.
supposed to rain tomorrow. Maybe I'll add a another sensor to chart local ambient outside of car.
Added T3 thermistor to read outside and clean rows w/ invalid data. at 3 to 4pm High sensor ~ 157°F Low sensor ~ 123°F outside: 100°F
Reported High from local weather stations: 95-100°F
Outside thru bottom of door on shady side on concrete. a few clouds between 1 to 2 high sensor to see some cooler air but note how fast it recovered and got hotter.
While most "Bad News" happens in summer... You can't let kids etc in a parked car even on cool days. Even 90 to 100°F cabin temp can kill kids pets etc. I measured 120+ on cool days years ago. Maybe I'll use same as above again on cool and even cold days. I think still have "it" in a box somewhere.
Again in short... These "Bad News" events happen way more then most think because if ever makes "news" that day often only Local News and near a "sound bite" length story even then. So Most people never hear/see news covering this. Some local news Weather people will mention this but only when you have a "Heat Wave."
Hey Ogre, could you possibly do a couple of special tests? A) Could you do a test of how a window shade affects the cabin temps.....And separately, b) Could you try parking the car at two angles, 1) front windshield towards sun, and 2) Rear window towards sun.
I use a a sun shade most of the time when parked outside, and also I have noticed (But I am not "Cal-E-Brated") that parking rear-window towards the sun keeps the car cooler.
Originally posted by cvxjet: Hey Ogre, could you possibly do a couple of special tests? A) Could you do a test of how a window shade affects the cabin temps.....And separately, b) Could you try parking the car at two angles, 1) front windshield towards sun, and 2) Rear window towards sun.
I use a a sun shade most of the time when parked outside, and also I have noticed (But I am not "Cal-E-Brated") that parking rear-window towards the sun keeps the car cooler.
Above was tested w/ most light going thru back and side direct from sun and > 120°F just after test started. Is likely why only reach ~ 155°F... Sun directly hit windshield only in late afternoon and evening. Don't have space etc to test parking in other ways.
Windshield shades may help or not because there's hundreds to thousands of designs and millions of ways to use them. I use "bubble sheet" type w/ "chrome" Plus "tin foil" sheet for bottom of Sun Roof. Left the shade off but sheet up for above test.
Then add need several days w/ same weather to test all of that... rare to have 2 days in a row w/ same weather here.
At the time tested years ago, Fiero was park so rear was facing to the sun in last winter or early spring. Sun angle let more sun in thru the side and rear glass and even w/ ~ 60°F outside the thermometer in the cabin was still reading well over 120°F.
So While how you park can affect cabin temps for a given vehicle... Doesn't charge the fact that a car can kill Kids Pets and wreck a lot of other thing when parked outside. Over 90°F can be fatal. Over 120°F starts to cook.
Even Leaving side windows cracked and Fiero SR Open (not off) and WS Shade up, the cabin can get very hot. I have solar vent fans that help because will force air to move out but still gets hot. But can't do any of that in many places unless you want to get stolen, damage or even ticketed. In many places is actually illegal to park w/ windows open for anti-theft etc.
There is some good information on this thread but I believe that the powertrain used would have a huge impact on the engine compartment heat. Is it logical to assume that the engine compartment heat would be the same for the 2.8L/3.4L 3.4DOHC, 3800SC, N*, Ecotech, 4.9L Caddy, SBC, LS1, 2, 3 and 4? It would seem each case is individual.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Originally posted by Dennis LaGrua: There is some good information on this thread but I believe that the powertrain used would have a huge impact on the engine compartment heat. Is it logical to assume that the engine compartment heat would be the same for the 2.8L/3.4L 3.4DOHC, 3800SC, N*, Ecotech, 4.9L Caddy, SBC, LS1, 2, 3 and 4? It would seem each case is individual.
I didn't see this at the time...
Yes, Different powertrain can be way different or not when testing bay air temp... Some w/ Turbo likely could see higher peak air temp because of exhaust plumbing. Some w/ bigger engines could see ~ same peak air temp but cool off a bit or a lot slower after shutdown.
Likely Even matters some just where you read bay air temp in 4cyl. I pick the location because right over the exhaust and cat and close to head. Remember O2 sensor doesn't work until exhaust is above 600°F. Cats get to 900-1100°F in normal operation. But peak air temp is just pushing 200°F on a very warm day.
Fiero big vents move a lot of air even when parked because of "stack flow" thru the whole bay. IOW Heat rises and big Fiero vents allow this way easier then nearly all others to cool everything in the bay.
Main point is Most "Claim" Fiero Engine Bay Air is hotter then others because (Fill the blank w/ whatever reason) is 99+% BS. Most never had FWD etc hoods open when engine is hot or bothered to test engine bay heat. Just push same myth front engines are cooler then all mid or rear engines. And still ignore many front engine cars have tight fitting or sealed hoods and don't have big grills for 20-30 years to give Fractional MPG improvements to bump CAFE points from EPA and related programs in other countries.
For many years now anyone can go to HF Amazon and more to get 1 or 2 channel temp meter w/ Thermocouple for cheap. Many Multi-function meters also read K-type thermocouples too. Yet most won't even use them and still echo same crap that Fiero has engine heat problems.
I have several meters w/ this feature but hard to use when driving w/o someone else just watching let alone recording data. So now w/ Arduino and needed parts cheap and easy to get (at that time) made data logger and stored in format that Excel and more can use w/o headaches. Above uses thermistors but have several thermocouples to measure actual engine cat and more directly but doesn't really matter testing bay air heat during a run and after shutdown.
(I posted such back them but not search PFF archives.)
