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Car Forum / Mazda / Mazda Miata / June 2005Turbo miata showing hot temperatures
My miata has started to run hot according to the temp gauge, which is not too surprising considering that we are already hitting close to 100 degrees. The car has a turbo running 9 pounds of boost, a large intercooler, and has no accessories like A/C or power steering. The temp gauge has been linearized (if someone could give a quick explanation of what exactly this means I would appreciate it). Anyway, the gauge goes up, but not past the water mark on the high end, and will actually get cooler sometimes when I apply boost. I used a friends red dot thermometer while the car's gauge was showing hot, and everything was running pretty cool from the engine to the headers to the intercooler, turbo, radiator, etc. The car also seems to be running identically to the way it was before the gauge started reading high, and the TEC-3 computer is showing no codes to indicate anything is wrong. My first guess is a faulty gauge, but the fact that it is running hotter just as the temperatures are soaring seems to be too much of a coincidence. The car also has an exhaust temp. gauge that is showing normal readings. I need to do some research on the power list, but I was hoping someone could offer some quick suggestions as to where to start. I was thinking about checking the gauge first, replacing the thermostat and/or trying to increase airflow into the engine compartment. If anyone has a link to an aftermarket temp gauge that shows numbers that will replace the stock gauge in the same location, that would be great as well. Thanks! Pat Here are some of the engine details if it matters: '94 1.8L bottom end (8.8:1 compression) '99 head & intake manifold ARP head studs ACT Extreme clutch Flyin' Miata/Fidanza lighthweight flywheel '99 Torsen differential (4.3:1), '00 axles & driveshaft Flyin' Miata aluminum radiator Coolant reroute to exit at rear of head Mazdaspeed motor mounts Linearized temp gauge, tach modified for quicker response No AC, no PS Tec3 ECU with latest software running full sequential Momo steering wheel 5 point harnesses in addition to factory belts CD player & headrest speakers Boost (in eyeball vent) & EGT (below stereo) gauges Garrett ball bearing GT2871R turbo w/ ATP turbo T3 .86 A/R exhaust housing Tial 40mm external wastegate w/ .4 bar spring ETD Racing "shorty" turbo header Custom downpipe by Corky Bell w/ flex sections & wastegate joined in at Cat Racing Mazda 3" high flow cat, bolt-in Enthuza Racing 3" single outlet turbo exhaust 18"x8"x3" bar & plate intercooler from Bell Intercoolers Silicone hose couplings, T-bolt clamps Vishnu dual feed fuel rail RC 550cc/min injectors Quick check: is your front license plate mounted right in front of the air-intake? That was my problem. When the ambient air temperature got above about 30 Celsius the engine started running hot. I tried everything - changing the thermostat and even the rad etc etc. It turned out to be the restricted air-intake because of the position of the license plate (why on earth did they put it right in front of the air-intake?!) Moving the plate onto the nose using http://www.mx5parts.co.uk/product_info.php/products_id/222 finally solved the problem. Eric > Quick check: is your front license plate mounted right in front of the > air-intake? That was my problem. When the ambient air temperature got above [quoted text clipped - 8 lines] > > Eric Hi Eric, there is no front license plate on this car most of the time. We are supposed to have one installed in Texas, but I have been driving here in Austin, TX for 20 years and have never been pulled over for no front license plate by local police. The highway patrol has enforced it on me, though with a warning each time, so I usually put it back on when taking trips out of town, especially to South Texas. pat >My miata has started to run hot according to the temp gauge, which is >not too surprising considering that we are already hitting close to 100 >degrees. Maybe crap build up in de cooling circuit? Mine was running hot, but after de coolant burst through the heater hose, it is actually running cool. I guess the burst blew some of the crap out. :) > The car has a turbo running 9 pounds of boost, a large >intercooler, and has no accessories like A/C or power steering. The temp >gauge has been linearized (if someone could give a quick explanation of >what exactly this means I would appreciate it). I can offer a pretty good guess. As discussed before, the Miata temp gauge is sitting in the center position from when the coolant is luke warm until just before the steam pressure blows up the engine. That is called a nonlinear response. I would assume a linearized gauge is one that shows the *true* temperature. >Anyway, the gauge goes up, but not past the water mark on the high end, >and will actually get cooler sometimes when I apply boost. I used a [quoted text clipped - 3 lines] >identically to the way it was before the gauge started reading high, and >the TEC-3 computer is showing no codes to indicate anything is wrong. I would think that the Tec is right. You are just seeing the *true* temperatures for the first time. Then again, I could be wrong and you buy a new engine. ;) > My first guess is a faulty gauge, but the fact that it is running >hotter just as the temperatures are soaring seems to be too much of a >coincidence. The car also has an exhaust temp. gauge that is showing >normal readings. Not related. >I need to do some research on the power list, but I was hoping someone >could offer some quick suggestions as to where to start. I was thinking [quoted text clipped - 3 lines] >that will replace the stock gauge in the same location, that would be >great as well. That is of course the way to go. But if I knew one, it would probably already be on my car. (Assuming it looks the same as OEM.) Leon  SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) REMOVE THE "z"s -> dommelenz@zmiata.net www.dommelen.net "EXIT THE INTERSTATES" (Jamie Jensen) > I would think that the Tec is right. You are just seeing the *true* > temperatures for the first time. > > Then again, I could be wrong and you buy a new engine. ;) Come on Leon, when have you, (or a computer), ever been wrong? ;-) > That is of course the way to go. But if I knew one, it would probably > already be on my car. (Assuming it looks the same as OEM.) > > Leon It seems like VDO, Autometer, or one of the other gauge companies would see a big enough market for an OEM-look replacement temp gauge with numbers for the miata since there are so many enthusiasts out there. However, like you, I have never seen one. I would definitely pay $50.00 to $100.00 for one if it becomes available. Thanks Leon, I'll check the cooling circuit and thermostat first. Pat >>I need to do some research on the power list, but I was hoping someone >>could offer some quick suggestions as to where to start. I was thinking [quoted text clipped - 3 lines] >>that will replace the stock gauge in the same location, that would be >>great as well. Not a gauge, but Davis Instrument manufactures a gizmo (Carchip E/X) that plugs into the car's ODB II port and records trip data and up to four engine parameters (if the vehicle is ODB II compliant, like a stock Miata is) You can download trip data for analysis on any PC. It is a trip and driver monitor, so use with caution unless you want to find out if your significant other is driving around with the rev limiter pegged. Only complaint I have about it is that I can't put back the dash cove unless you cut finger recess molding on it, that that hole is mostly invisible anyway. You can pick one up at Autozone or Sears, and of course, Ebay. > Not a gauge, but Davis Instrument manufactures a gizmo (Carchip E/X) > that plugs into the car's ODB II port and records trip data and up to [quoted text clipped - 10 lines] > > You can pick one up at Autozone or Sears, and of course, Ebay. This is a heavily modified miata with a Tec-3 engine management system. I haven't looked at all of the features it has yet, but it probably monitors top speeds and that sort of thing, it seems to do everything else from adjusting the turbo boost levels, the timing, the air/fuel mixture, fuel flow per injector, etc, etc., all from a laptop showing the engine working in real time using a dashboard gauge layout, it is really very cool. You can have the passenger make adjustments to the timing as you drive to see the immediate effects, something that is obviously impossible with the stock setup. There is no more factory rev limiter, you use the computer to set it anywhere from way below the miata's stock max rpm all the way up to 20,000 rpm, though I believe that I would have a smoking ruin of an engine long before then. ;-) I have it set at 7500 rpm max right now. No significant other to worry about right now, my miata's babe magnet seems to be malfunctioning. I'll have it checked out next week. :-) Pat I've glanced at the specs of that unit not too long ago (user's manual mostly) I do remenber this: That unit allows you to map and modify the engine behavior (or screw it up royally) using a laptop on the fly. Back to the original topic about running hot: I do remeber the trigger points of the cooling fan are settable (to do this it has to monitor the coolant temperature, that is a standard ODB II parameter). and the user's manual has a table of the datastream (i.e. the byte order for a scan cycle and what they are, so you can monitor anything that is hooked up to the control unit) with a reference to outputinig the data to other applications, such as a spreadsheed. it may require some figuring out, but you should be able to get listing of whatever your engine is doing (it many help if you know any control systems engineers) I did not see any refences to connecting a windows CE or Palm Pilot device as a handheld monitoring and logging device though I thing that would be very usefull for monitoring operating conditions. Good luck >This is a heavily modified miata with a Tec-3 engine management system. >I haven't looked at all of the features it has yet, but it probably [quoted text clipped - 15 lines] > >Pat >> Not a gauge, but Davis Instrument manufactures a gizmo (Carchip E/X) >> that plugs into the car's ODB II port and records trip data and up to [quoted text clipped - 18 lines] >the engine working in real time using a dashboard gauge layout, it is >really very cool. If it like my Link ECU, it also outputs coolant temperature. Leon >You can have the passenger make adjustments to the timing as you drive >to see the immediate effects, something that is obviously impossible [quoted text clipped - 8 lines] > >Pat SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) > If it like my Link ECU, it also outputs coolant temperature. > > Leon I haven't had as much time to check it out as I would like, but I should have time to look at it soon and learn some more about it. As a test, I took out the driver's side turn signal and noticed immediate cooling improvement (according to the gauge) once I reached speed. It is still creeping up at stop lights, but not dangerously so, and I have a feeling that, as you said, I am simply seeing a true reading of the temp since the gauge is now "linearized" (without numbers, grrrr....), and it makes sense for it to go up some during a stop in this extremely hot weather even with the fans working properly. Just as a side note on the temp gauge, my friend's GMC pickup has a gauge that shows actual numbers and registers hotter or cooler according to temperature, so I am assuming it is linearized instead of an idiot gauge. I guess neither Mazda nor the aftermarket auto gauge companies can manage to accomplish such a feat for us. Pat > Just as a side note on the temp gauge, my friend's GMC pickup has a > gauge that shows actual numbers and registers hotter or cooler according > to temperature, so I am assuming it is linearized instead of an idiot > gauge. The Miata temp gauge isn't really an idiot gauge (like the post-'94 oil pressure gauge). Even unlinearized--is that a word?--it's only a bit sticky in the middle, refusing to move when the coolant is within its ideal temperature range. It still registers overheating long before it gets hot enough to become an emergency. I like it this way. I don't need to know every time the fans come on or the thermostat opens. At a glance, I can tell if everything's OK, without having to analyze the reading. When I was having cooling problems a couple of years ago (intermittant dead fan) it helped me manage the situation until I could figure out what was wrong. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html > The Miata temp gauge isn't really an idiot gauge (like the post-'94 oil > pressure gauge). Even unlinearized--is that a word?--it's only a bit [quoted text clipped - 12 lines] > '94C, St. Louis > http://www.hummingbirds.net/alignment.html Makes sense to me, but I would still like to see the actual numbers, I guess it is just a personal thing. Leon wants numbers too, so that should tell you something. ;-) One question, at what point on the gauge do you think that the temperature has moved out of the optimum operating range and is starting to run too hot? Mine is reaching the end of the squiggly lines, but does not go further. Once I get moving it goes back to the middle, and we are reaching just under 100 degree days right now where I am. Finally, it looks like the car is running considerably cooler at 35+ mph from the air entering the turn signal hole, so I guess I will buy a flow-through turn signal even though I don't like how they look. I was also thinking about something along the lines of your Randall intake, though it obviously would not hook to the air intake, but rather just blow air from the cowl area through the firewall and over that hot turbo/exhaust area. Has anyone heard of a homemade kit that does this or if anyone has modified the Randall intake to bring air in at this point? Thanks! Pat > Leon wants numbers too, so that > should tell you something. ;-) It tells me he's an engineer. Leon was disappointed with Alphabits breakfast cereal when he discovered it was all letters, no numbers. He actually signs his checks in hexadecimal. > One question, at what point on the gauge do you think that the > temperature has moved out of the optimum operating range and is starting > to run too hot? On US-spec Miatas, the "normal" position (the hysteresis zone) is about one needle width left of center (it's one width to the right on Canadian cars). Anything higher than that means the cooling system isn't coping. I wouldn't panic (turn off the A/C, e.g.) until it reached about 3/4 of the way toward the right end. I would keep an eye on the coolant level, though. > I was also thinking about something along the lines of your Randall > intake, though it obviously would not hook to the air intake, but > rather just blow air from the cowl area through the firewall and over > that hot turbo/exhaust area. I'm pretty sure it won't work that way. Assuming the local pressure at the mouth is greater than at the base of the windshield, your cowl vent would be an outlet, not an inlet. The Randall works because it's sealed from the hot, pressurized engine bay, and deals only with the pressure differential between the cowl and the airbox. Running with the headlights up will cool it off significantly underway. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html > It tells me he's an engineer. Leon was disappointed with Alphabits > breakfast cereal when he discovered it was all letters, no numbers. He > actually signs his checks in hexadecimal. Heh-Heh! > On US-spec Miatas, the "normal" position (the hysteresis zone) is about > one needle width left of center (it's one width to the right on Canadian > cars). Anything higher than that means the cooling system isn't coping. > I wouldn't panic (turn off the A/C, e.g.) until it reached about 3/4 of > the way toward the right end. I would keep an eye on the coolant level, > though. If only I had A/C, what a concept. Buying a car in Texas as my only daily driver without the godlike wonders of A/C might not turn out to be my wisest decision, we'll see if I live to regret it or perish before buying an OTM. If you see a human on fire in a red miata in Austin, that is probably me. :-) Still, with nightime lows of 72 degrees, driving after dark is wonderful. The coolant level has been fine, and it hasn't reached 3/4 yet. That, along with my friend's expensive red-dot thermometer showing normal operating temps on the various engine and exhaust parts, I guess I shouldn't worry too much. I'll still play around with the Tec-3 computer whenever I get a chance. Since the engine light will blink for something as simple as not letting the fuel rail charge for a few seconds before starting, I would hope that it monitors coolant temps and would send a blink code, but I need to study it some more to be certain. > I'm pretty sure it won't work that way. Assuming the local pressure at > the mouth is greater than at the base of the windshield, your cowl vent [quoted text clipped - 3 lines] > > Running with the headlights up will cool it off significantly underway. Thanks, it looks like the turn signal intake may be the best way to go, I have popped up the headlights and noticed an improvement, but not as much as from opening up the turn signal hole today. I haven't tried both at once yet. If anyone has a red driver's side Turn Signal Intake for sale, please let me know. Pat >> It tells me he's an engineer. Leon was disappointed with Alphabits >> breakfast cereal when he discovered it was all letters, no numbers. He [quoted text clipped - 40 lines] >If anyone has a red driver's side Turn Signal Intake for sale, please >let me know. I would stay away from the funnel-shaped ones. A screen type might be the best, I would think. Leon SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) > I would stay away from the funnel-shaped ones. A screen type might be the > best, I would think. > > Leon Would this be to keep debris out or is there a design problem that you know of with the funnel-style intakes? Pat >> I would stay away from the funnel-shaped ones. A screen type might be the >> best, I would think. [quoted text clipped - 3 lines] >Would this be to keep debris out or is there a design problem that you >know of with the funnel-style intakes? There is a designer problem. When the area of a duct decreases, the velocity goes up. So the designer obviously reasoned that by contracting the duct [s]he would get a powerful blast of air into the engine bay. Unfortunately, it does not work. You cannot get a blast of air if no air enters the duct at the other side in the first place. The best would be to have a diffuser, not a funnel. Leon SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) <snip> > Running with the headlights up will cool it off significantly > underway. Would I be correct in assuming that that's because of the air that leaks in around the lights? -Scott > <snip> > [quoted text clipped - 5 lines] > > -Scott That is correct. It is not unusual to see M1 racers on the track with the headlights popped up to grab that bit of extra cooling. Pat > > Running with the headlights up will cool it off significantly > > underway. > > Would I be correct in assuming that that's because of the air that leaks in > around the lights? More than leaks--they act like scoops. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html >>>Running with the headlights up will cool it off significantly >>>underway. [quoted text clipped - 8 lines] > '94C, St. Louis > http://www.hummingbirds.net/alignment.html Well, if you gotta get technical. :-) Would it make sense to you that I would seem to be getting better/quicker cooling from a completely open turn signal hole than from the headlights being up? I also seem to remember that you had a method for diagnosing the intermittent fan problem. If you have those instructions that would be great because I would still like to check that out to be certain it isn't the problem. Thanks, Pat > Would it make sense to you that I would seem to be getting > better/quicker cooling from a completely open turn signal hole than from > the headlights being up? Sure. But bear in mind that a TSI's opening is much smaller than the hole left by removing the light assembly entirely. Leon can tell you how boundary layers restrict flow even further through a small opening. I also wonder if auxilliary air inlets don't reduce the efficiency of the radiator, by "competing" for the ability to raise the pressure of the engine bay. I have no data that this actually occurs, it's just a thought experiment, but if airflow is limited by the exit capacity, you might be robbing Peter to pay Paul. What's more important: reducing the temperature at some arbitrary sensor location in the engine bay, or helping the cooling system operate according to its design? > I also seem to remember that you had a method for diagnosing the > intermittent fan problem. If you have those instructions that would be > great because I would still like to check that out to be certain it > isn't the problem. I removed the suspect fan (shroud/motor/blade assembly) and connected it to a spare battery. I marked one blade so I could keep track of its position. Repeated connections revealed that if the blade stopped in a certain position, it would not restart without a push. My conclusion was that the motor had developed a dead spot on its commutator; sometimes it would stop and not restart, until--presumably--a bump in the road jarred it off the dead spot. Or something. Replacing the motor with a used part solved my problem. --- Lanny Chambers '94C, St. Louis http://www.hummingbirds.net/alignment.html >I also wonder if auxilliary air inlets don't reduce the efficiency of >the radiator, by "competing" for the ability to raise the pressure of >the engine bay. I have no data that this actually occurs, it's just a >thought experiment, but if airflow is limited by the exit capacity, you >might be robbing Peter to pay Paul. There is no given exit capacity. When you raise the pressure in the engine bay, more will go out. But it has been claimed that air may go out of the ThIs instead of in. And the critical question is not really how much air goes out, but the amount of heat the air takes out, and from where the air takes that heat. That depends on the pattern of flow, not the amount. I would think the real questions are 1) is the coolant temperature within safe limits. 2) is the intake air temperature as low as possible. The Link ECU shows both of those temperatures, and the Tec might too. The Link has logging capability, so if I worried about mine, I would have my Palm or portable hooked up during driving to see. (Actually, I already know both are problematic. Air temperature I cannot do much about, not liking TSIs, but hopefully the coolant might be better now.) Leon SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) >ThIs Isn't spell checking wonderful? Leon. ;) SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) |
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