GaryRudolph

I am feeling real good about this table, but confirming with a 3rd party sensor like in vapors2k's car would be the clincher.

On the colder thermostat. The thermostat will still be closed at cold start. And the engine should warm up similarly to a stock car up to the point that the Mugen starts opening. I'm assuming it's similar to the fan switch and will be 7C lower. But, at the point the Mugen starts opening until the operating temperature it will take longer to warmup. The fully warmed temperature should be lower, but I would not expect a full 7C.

The engine won't run colder than the thermostat once it's warmed up, and I don't see it opening quick enough that you'd ever get a fast drop that would cause it to go below the temperature of the thermostat.

cbender

Hi Gary,

That's my thought, but therein lies the quandry.

1. If I apply the EMS v1.04 calibrations to my past datalogs, my operating temperature ranges have been:

Street (Cold Day): 175-191 degrees F
Track (Cool Day): 175-212 degrees F

While the 212 value is higher than I'd like -- and higher than I'd have expected given the capacity of my new radiator -- the car is clearly running within the Helms manual's recommended range of 176-212 degrees. Conclusion: perhaps a tad hotter than I'd like under track conditions for a cool day, but not unreasonable.

2. If I apply your calibrations to my past datalogs, my operating temperatures have been:

Street (Cold Day): 160-172 degrees F
Track (Cool Day): 160-193 degrees F

Now, I seem to be running a LOT colder than the Helm's recommended range. Note that these lower temps readings were measured when the car was already warmed up and idling, so these are not INITIAL temps on startup but the sorts of temperatures I could conceivably see if, for example, I sat at a stoplight for a couple of minutes.

They seem suspect to me given that I wouldn't have expected the Mugen thermostat to keep the car THAT much colder. King Motorsports says that the Mugen thermostat begins opening at 154 degrees F. and is wide open at 181 degrees F. Thus, I guess it's conceivable that if the engine is just idling, with no load on it, it could run as cool as 160 degrees, but King said that it's more likely that it'll run at about 170 degrees under those conditions.

So, do you see the issue? If I use the EMS-calibrations, my temps seem within a reasonable range, but perhaps hotter than I'd like. If I use your calibrations, my temps seem to run too cold and colder than one would expect with the Mugen thermostat which doesn't rely on ANY calibrations because it's mechanical.

All the above said, pls. don't take me to be saying that I'm anything but grateful to you for the experiment you've done. I would just like to get to the bottom of this, regardless of the answer, as it's been bugging me for months! If you can shed light on it all, that'd be really helpful.

Best,
CB

hans

As a sanity check, when both calibrations are correct, the air temp (AIT) and the coolant temp (ECT) on a cold car, say in the garage first thing in the morning, should be the same. Mine have only been the same since using both of the modified calibrations given in Gary's post at the start of this thread.

Using both AEM calibrations, my readings were WAY off. Using the modified AIT calibration, my readings were close. Using modified AIT and ECT calibrations, my readings are spot on. Not proof, but certainly evidence.

As an aside, I never get my oil hot around town -- and that has nothing to do with the AEM ECU, as my oil sender is in a tapped hole in my oil drain plug and feeds an AutoMeter gauge directly. On the track I get oil temps up to 220F -- around town, as long as the car is moving my oil temps never get over 140-150F.
I have two water temp sensors -- the Honda sensor feeding the ECU, and an AutoMeter sensor, located after the radiator, feeding a gauge. The Honda sensor gets to 180-190 fairly easily, but the post-radiator sensor struggles to get over 140F around town. On the track it gets to 200F. Total speculation, but I'd guess that Honda routes water just returned from the radiator to the water/oil heat exchanger in order to provide the coolest water to extract maximum heat from the oil.

Hans/Westy

GaryRudolph

How does the Helms have you read the temp (don't have it with me travelling)? OBD2?
With the massive cooling you have and the thermostat being full open at 181F I would really doubt the temps would reach 191F on the street (using the AEM cal table). Although, 171F on the street using these cal values seems low.
One thought... The Mugen thermostat was meant to drop the temp point for the stock radiator. I wonder with your big @ss radiator if that thermostat is causing too much cold coolant into the engine causing the colder temps. In fact, with that radiator the stock thermostat may be better??? But, you can't make that decision until you have an ECT value you're confident with. I wouldn't make any changes until you are.

[QUOTE]
All the above said, pls. don't take me to be saying that I'm anything but grateful to you for the experiment you've done. I would just like to get to the bottom of this, regardless of the answer, as it's been bugging me for months! If you can shed light on it all, that'd be really helpful.

GaryRudolph

Hmm, I forgot to check that and that's a good observation. I'll have to remember to compare at a complete cold start to see where I sit. But, I'm still hoping to get verification using another sensor in the block.

cbender

Thanks, Hans and Gary,

This stuff makes my head spin. I appreciate the discussion hugely, as otherwise I don't seem to make much sense of it all.

My "take" on the thermostat is that it shouldn't matter what's in the pipe behind it -- very cold coolant or lukewarm coolant. It simply opens when the coolant circulating around the block gets hot enough to trigger the spring. When the coolant in the block isn't hot enough to trigger the spring, it stays closed and recirculates the coolant until it gets hotter.

If that's true, then on a cold day, it seems to me that it ought to stay open only long enough to admit a small trickle of coolant because that should be enough to maintain the coolant in the engine at a reasonable temperature under light loads. On a hot day, it ought to stay open longer and more fully to accomplish the same purpose.

If the radiator is bigger or more effective, it's simply the equivalent to operating under lower ambient temperatures by some amount. Thus, the radiator itself shouldn't make a difference PROVIDED that there's an adequate supply of cooled coolant available. Put another way, the stock radiator and my new radiator ought to generate identical operating temperatures, when those temperatures are measued within the block, provided that the engine's not generating TOO much heat for the radiator to dissipate.

Or at least that's how it ought to work, if I'm understanding the theory behind it correctly.

Answers: the Helm's manual doesn't say how temperature should be read, but I'm assuming it's read via the OBD-II port, so I'd imagine it's reading the ECU's sensor input, either in raw volts or, more likely, in volts converted to degrees, don't you think?

160 degrees F. seems "almost reasonable" for a low-end operating temperature on a cool day -- given that the Mugen starts opening at 154 degrees F -- while the car's at idle, but it seems to me that under modestly hard street driving on the same day that my temps ought to get over 170 degrees!

Which leads me, precisely, nowhere... ;(

But at least this discussion is helping clarify some of the issues. Thanks, guys.

Christopher

hans

Christopher --

Your very large radiator is likely to be having some effect. You say the Mugen thermostat starts opening at 154F and is full open at 181F. Consider two cases -- a very marginal radiator, and a VERY LARGE radiator.

With the marginal radiator, as 154F coolant begins to circulate, the radiator doesn't exchange much heat with the ambient, so the engine doesn't cool much. Coolant temps in the engine rise and the thermostat opens further. Still not enough heat is being rejected, so the thermostat opens fully at 181F. If the weak radiator is adequate at this point, given the ambient temperature, coolant temps will stabilize at 181F. If not, coolant temps will rise higher, until heat put into the coolant from the engine equals heat sent out of the coolant and into the ambient. If this happens before the vapor pressure of the coolant equals the popoff pressure of the radiator cap, all is (for the moment) well. Else . . .

With the LARGE radiator, when the coolant flows at 154F, heat rejection to the ambient begins. If the ambient temperature is low and the radiator is efficient enough, return coolant to the engine could be cool enough to hold the engine temperature at that point. So a large radiator will help keep the thermostat mostly closed and operating in the lower part of its range.

The thermostat is not an on/off switch. In a well balanced system it will operate at a stable point (determined by the outside temperature), somewhere between fully open and fully closed.

Sorry for droning on.

cbender

Sounds more like useful thinking to me. Droning has more of a monotonous hum to it, I think...

I think we don't really have any points of disagreement. What I was saying was that provided you're not exceeding the thermal transfer capacities of the radiator (in layman's terms, which suits me better anyhow, the radiator is sufficient to exchange enough heat to stabilize the operating temperature without having to operate fully open all the time), it shouldn't matter whether the radiator is marginal (but adequate) or huge.

The point at which the operating temperature of the engine should stabilizes should be the same for both radiators, although the larger capacity radiator will be able to operate without ever having to open as far or as often as the smaller.

At least that's what I'd meant to say.

It still leaves open the question of whether or not an operating temperature of 160 degrees under very light loads on a cool day are (i) accurate (i.e., they represent the temperatures the engine is actually seeing) and, if true, (ii) problematic (i.e., should I be concerned that my engine's never sufficiently warming up?).

If Gary's calibrations are correct, well, I guess the good news is that my new radiator has resolved my cooling problems. I can live with 193 degrees F. under very hard track conditions with the turbo.

I swapped out Gary's ECT calibrations and, like you, my coolant temperature and air intake temperature now are pretty close -- 40 degrees air, 35 degrees coolant -- and consistent with an ambient air temperature of about 43 degrees. Too bad my oil temps were only reading 32 degrees F, after returning the EMS to AEM! When I get the car running again, I'll be able to see if the oil temps seem more reasonable under true operating conditions. I suspect that using the EGT inputs may be part of the problem, although AEM says it should work just fine.

Best,
CB

twohoos

[QUOTE]Originally posted by cbender
What I was saying was that provided you're not exceeding the thermal transfer capacities of the radiator (in layman's terms, which suits me better anyhow, the radiator is sufficient to exchange enough heat to stabilize the operating temperature without having to operate fully open all the time), it shouldn't matter whether the radiator is marginal (but adequate) or huge.

cbender

Hi John,

Thanks for chiming in. This is really not the central point of the discussion -- and I recognize I could simply be wrong (I often am) -- but if the springs of a thermostat respond to the temperature of the coolant circulating inside the block -- and that volume is fixed -- why would they not eventually settle on the same -- or at least very close -- equilibrium temperatures under light loads (where the heat generated by engine isn't varying much), regardless of the temperature or the volume of the coolant available to cool the engine coming out of the radiator?

It just seems to me that all a larger radiator does is provide cooling *capacity*. The thermostat does the work of deciding how to employ that capacity. Cooler coolant (i.e., larger radiator) simply means that the thermostat opens less wide than when the coolant is warmer. But it still seems as if, in the end, the thermostat would settle on relatively similar equilibrium tempertures. Or maybe I'm missing something. The volume of coolant inside the engine is the same and that's where heat is being exchanged with the engine, right?

But back to the central point (at least for me) of this discussion... If Gary's calibrations are correct, then I tend to run colder than the Helm's manual recommends, but under hard driving conditions, I'm in a very good, perhaps ideal, range (180-193 degrees F). My options, then, seem to be (i) to keep things as they are, (ii) to change the EMS fan engagement so that I'm not turning the fan on prematurely, or (iii) to switch back to the stock thermostat.

Your comment suggests, I think, that I shouldn't worry about it. Changing the EMS fan engagement thresholds (from, say, "on" at 190 and "off" at 180 to "on and off" at 190, perhaps?) is trivial. And, perhaps, simply switching to Gary's calibrations will help in this regard anyway because the EMS calibrations are turning the fans on some 19 degrees F *earlier* which (now that I think about it) could be part of the problem). Swapping out the thermostat is a bit of work, but it's not that bad. I've had to drain and purge the coolant once this year already. Thoughts?

CB

PS: how did you determine that the third-bar comes on at 120 degrees F? Have you any idea of when the fourth-bar comes on? That would be interesting to know because I never hit four bars before I installed the EMS, so it was something of a shock to me to see that my temps. were hitting 228 degrees F (admittedly with an unknown temp. calibration) when I switched to the EMS this past summer. But I never did locate anything that shed light on what the bars actually mean.