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#1
Icedawg

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Hi all,

 

I am new to this forum, having just started racing a 99 SM this season, running a stock radiator.  Prior to that I raced a first generation RX7.

I have a question about engine temps.  After recently installing an Autometer temp gauge, I found the typical  temp is 190 F in free air, but when behind another car it usually rises to 210, and then stays there for the rest of a race, even when back in clear air.  From posts here I see that this temp is a bit higher than desirable.

 

But I also saw one poster stating that a "poor sensor installation" can cause misleading temp readings.  I am not sure what constitutes a poor installation though, and am wondering if the location I used could be a problem in any way.

 

I placed the sensor at the back of the engine, at the thermostat fitting, which is where the stock T send is also located.  There was a blind plug there that I removed, to insert a "metric to sensor thread" adaptor.  I could not use the supplied sensor, as it did not fit inside the adaptor, so I bought an Autometer "short sensor"  that fits into the neck of the adaptor and sits flush with where the threads start.  As a result flow over the sensor will be a bit hindered.  It obviously wets, or the reading would be far more eratic.

 

Any thoughts on this location?  Do the readings make sense, or could the location be giving inflated readings?  Do I simply need a better radiator?



#2
FTodaro

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That location at the back of the head Is a good accurate spot as that is the head temp as the water exits the motor going into the heater core. Are you running at Thermostat? Some don't. Some run a stat with a hole in in it.

 

If you don't like those temps you need to run a cross flow radiator. I run the Springfield dyno and I always have to run tape to get the temp i need in the VVT. 


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#3
Brandon

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Stock radiator is the issue with your elevated temps not coming down.

Thermostat is a way to keep the elevation from occurring.

Aftermarket radiator is your best attempt at recovering from an elevated temp.

 

Lots of options for a radiator, but your location isn't shown so it's difficult to provide guidance on whether the SD is the one for you (racing below the Mason-Dixon line) or something else and a little less expensive.


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#4
Icedawg

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Thanks for the feedback.

I did not change the thermostat, so it should be stock.  It is a junkyard engine swap, after I spun a bearing in the good engine.

I assume that is why it starts out at 190 and stays there if not stressed with hot engine fumes from the car ahead. I see some suggest a lower temp thermostat, 175 or 180.  Seems like a good idea.

I race in the great white north, Edmonton, Alberta.  Our hot weather is 85 to 90 F.

I will probably get a cross flow rad at some point in the future.



#5
Danny Steyn

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Even with the best SM radiators on the market, if you race at Daytona, but drafting from T6 to the bus stop, and from the bust stop to T1, the pushing car will see temps in the range of 235-240F in summer. After doing the switcheroo going into T1, by the time the now leading car gets to T6, temps are back down to around 190F.

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#6
Tom Hampton

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As noted, yes, you need a better radiator.  Any of the large cross-flow designs will be light years ahead of stock.  Advanced Autosports, ESR, Springfield Dyno, etc. 

 

Don't bother with something like a Koyo, which is large, but still vertical flow.  They are better than stock, but not by much.   Even without a Tstat I was constantly fighting temp to keep the ECU from pulling timing (200F was normal, and 210-220 was common late race). 

 

NOTE: I run a 1990, not a 1999.  I do NOT run a T-stat, unless its below 60F or so (or wet).  I did not run a T-stat in NOLA last weekend after the sun came out and temperatures came up into the 80s (versus raining and cold on Friday morning).  Engine temp was 185F at the end of the 25 min races. 

 

I ran a T-stat in the first afternoon session on Friday after the sun came out.  Engine temp got up over 210.  I removed the T-stat, engine temps dropped back into the 170s.  I was mostly running in clean air, as the SM group was pretty small. 

 

All open air data:

 

<60F wet, no Tstat = 110-120F engine temp

<60F dry, no Tstat =  140-150F engine temp

>80F dry, with stock Tstat  = 210-220+ engine temp (timing is being pulled)

>80F dry, no Tstat = 160-200 engine temp (changes with air temp)

 

Obviously the draft makes all of these hotter, but not much bump drafting in the wet!

 

I live and race in texas, so I spend most of the year in >80F conditions.  Really, only January is much at risk of being in the <60F range.  Consequently, I leave the Tstat out, and carry it with me in the spares box (for exceptions). 


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#7
Alberto

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If you're going to run a thermostat, run a 180* or 160*.  I run a Koyo and a 180* tstat in my 1.6 in Northern CA and measure temps at the back of the head.  In 80* weather, the engine will run around 190-195 during a race.  In 90* weather, it will run around 200*.  In low 100 ambient temps, it can get to 210 or so and I've been tempted to remove the tstat in that weather but it's rare that I race in those temps anymore.

 

When I tested the 160* and running w/o a tstat, the engine would not exceed 180* in cooler weather which you might have in Canada.  

 

Here are some of my experiences with thermostats fwiw: http://blog.miatarac...spec-miata.html


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