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05-26-2017, 08:05 AM | #23 | |
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DME does target 180f coolant at WOT though. That does not seem to ever be achieved with stock DME settings. However, tuning has completely changed my cooling. Some simple table changes now have my coolant sitting at 180f rising to no more than 200f after 3-4 consecutive 4th gear pulls (something you'll never do on track). Basically, tuning alone combined with straight water has me thinking there is 0 need to upgrade my radiator. Seems like other people that have upgraded their radiator are actually experiencing coolant never getting up tot temp in the winter. Seems unnecessary after making the aforementioned DME changes. Stock system seems capable enough you just need to drive that water pump for power instead of it constantly spinning at low speeds to keep things warmer for economy. |
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05-27-2017, 10:02 PM | #24 | |
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Green lap - max speed 210 km/h, Outside Air Temp 19C, Max Coolant Temp 111 C. Purple Lap - max speed 184.7 km/h (power is pulled right after the 3rd gear shift and I get off the throttle momentarily in response to that), OAT 29C, Max Coolant Temp 120C. The fact that 10 degrees more OAT means 10 degrees more coolant temperature indicates that the cooling system is operating at maximum capacity. I believe in both cases this was running (a very mild) Cobb Access Port "Drive" tune. Any tune hotter than this would be worse. This is a track with a long uphill straight and the coolant temperature rises steadily as soon as i get on that straight. This also confirms that the cooling system is operating at maximum capacity. If the thermostat was regulating, which is to say if the radiator had any excess capacity, the temperature would be steady. |
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05-28-2017, 12:13 AM | #25 | |
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The coolant pump only moves so much fluid. Heat can't be dissipated if it's not being pushed through your radiator. You may only see a steady incline in coolant temps in that log because the water pump simply isn't spinning fast enough to remove heat from the head. 66f is not hot enough to trigger faster water pump speeds. I can assure you there is excess capacity in the cooling system. As an exmaple, in 30f weather my coolant temps can be 236f during a 4th gear pull. When ambient hits 90f+ the ambient threshold is reached and coolant temps could actually drop to 180f during the same pull. Mhd race settings allow this to happen at 70f. It's been pretty shocking to see all this time there was so much extra cooling capacity not being utilized because the water pump just wasn't spinning in order to intentionally keeps things warmer for efficiency. Last edited by bNks334; 05-28-2017 at 12:28 AM.. |
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05-28-2017, 10:33 PM | #26 | ||
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05-29-2017, 10:01 AM | #27 | |||
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You're right in that the radiators capacity is still exceeded, but coolant table changes can have you sitting at 180-190f for 90% of your lap and only rising that 10-15f increase during your pulls on the straight away... You'll probably be able to stay under 210f in the same situation you're currently hitting 240+. Huge difference there...
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Even high mode requires ambient to be at 37c (99f) before it targets 95c coolant (203f). Therefore, you're water pump will be spinning at speeds designed around "normal" mode in just about all instances on a road course and only targeting 106c coolant (223f). With the "race" settings, high and high + HKF modes are activated at lower ambient thresholds and target EVEN LOWER coolant temps than stock. Real world results of the changes: E30 custom tune hitting 215+ load: 4th gear pull (65f) vs 4th gear pull (94f) - both logs are of how things look after 3-4 4th gear passes have already been made back-to-back: http://datazap.me/u/banks334/v6-65f-...=1&data=4-6-16 Just for reference, here is how my car did at two tracks even before any cooling changes (Old 93aki 200 load custom Cobb tune. Cooling tables could've been modified by COBB but I am not 100% on that): Palmer (65-75f ambient) : http://datazap.me/u/banks334/palmer-...data=1-5-14-18 Lime Rock (88-90f+ and very humid): http://datazap.me/u/banks334/track-d...on-4-lime-rock I imagine the above logs will look way cooler this season with the new MHD settings. Last edited by bNks334; 05-29-2017 at 10:14 AM.. |
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05-29-2017, 12:18 PM | #28 | |||
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It isn't clear just from the tables what the control logic is though. Although ambient and throttle position are table inputs, I have to believe the actual coolant temperature is a control parameter also, and that after something like 100 C, the coolant flow will be maximum regardless of ambient or throttle position. Quote:
I have a Mosport GP track day mid June. I will hope for hot weather so I can report back on how effective the radiatior change is. |
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05-29-2017, 12:43 PM | #29 | |||
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The cooling system can be completely overwhelmed in 60f weather yet in 90f it has no problem keeping coolant under 200f lol... Quote:
I was hoping to get back to LimeRock in June, but I have a wedding to go to that weekend. Soon enough I'll get logs on track with MHD race settings and see what's what... |
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05-31-2017, 12:31 AM | #30 |
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How the Cooling System and MAP Thermostat Work
I found the following enlightening, both how our electronically controlled thermostats work, and what the ECU is trying to achieve by targeting different coolant temperatures for different operating modes. The most important observation is that under track conditions we will be operating under "90°C High + map-thermostat mode", which is to say maximum cooling.
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05-31-2017, 12:50 AM | #31 | |
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So the latest MHD patch obviously forces the car to avoid 'normal' and 'eco' modes when you put it in Sport cooling mode, and always stick to "90°C High + map-thermostat mode" when in track mode. EDIT: or reading the documentation provided above, it simply reduces the temperature targets for each of the different modes. This (MHD patch) obviously helps for enthusiastic street drivers, but if you're on the track you're going to be limited by the thermal transfer capacity of the radiator rather than the water pump or initial water temperature. |
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05-31-2017, 10:22 AM | #32 | |||
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Yes the car targets different coolant temps based on CERTAIN conditions. The N54/N55 engine PDFs stops short of telling you what those conditions are... As MHD has pointed out, and I have verified with the above logs, The conditions are AMBIENT RELATED and PEDAL POSITION related. The load based coolant targets are only used when the car is in "open map mode" or "KFT." Driving your car onto a track doesn't magically put the car into "track" mode (high + KFT). The DME logic is that is has to be 108f outside lol or you have to be at 100% WOT... MHD simple lowered the floor so that HIGH + KFT mode can be achieved in 70f ambient temps and not the ridiculous 108f... They also lowered the cooling target to drive the water pump a bit harder (85c down to 80c). It's that simple... The DME logic is not very robust. As I pointed out, 69f my coolant can be overheating and then as soon as ambient hits 70f (MHD's new threshold) coolant can drop to 180-190f... The dme doesn't avoid "normal" mode or the other settings... they've all been adjusted DOWN so you get into higher modes earlier. Quote:
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Now I am leaning towards this might be true for OIL temps, but not so true for coolant temps. Coolant can transfer heat easily, as pointed out by Fel1x. Seeing as how you spend most of your time on track only using small throttle inputs, coolant has plenty of time to recover (drop back down from ~200f it might hit on the straight to ~180f target) as soon as you finish blasting down the straight away... the rest of your lap might increase oil temps over time due to high rpms and poor heat transfer of oil, but coolant should be able to stay at a more steady state. At least this is what I've found so far... Only a few track days with data will tell... It's definitely worth running the DME adjustments though either way. Last edited by bNks334; 05-31-2017 at 10:50 AM.. |
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05-31-2017, 05:43 PM | #33 |
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Maybe "overheating" needs to be defined. To me it means "in excess of the threshold at which power is pulled (117°C / 243°F)". Anything else is just hot.
I believe the N54 and N55 have different heat issues. N55 may be more critical with respect to oil temperatures. Below are maximum and minimum coolant and oil temperatures for 9 full laps at Mosport GP with OE rad at 29°C OAT (84°F). Anything over T1 is overheated. The coolant is overheated on every lap from 3 on. No change in thermostat tuning will alter this because even from a low of 100°C the car will overheat in 2 laps. This engine is putting more heat into the coolant than can be dissipated by the cooling system at a coolant temperature of 117°C or less. Had the DME not pulled power back, the situation would have been even worse. Say what you like about the N55, but the N54 clearly needs a bigger radiator on this track, at this OAT, and with this very mild tune. Oil temperatures show plenty of margin. |
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05-31-2017, 06:07 PM | #34 |
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I see what you're saying but you're still completely ignoring the fact that youre not even maximizing current cooling systems capacity.
Is ambient over 108f? Are you at wot 100% of the time? Let me answer that for you... no and no. Therefore, there is an entire other side to the cooling equation your statements are ignoring... and that is flow. You can't dissipate heat if the water pump isnt pushing coolant through the system. The radiator radiating heat is only 1 half of the equation to computing your cooling capacity. I'll post results of the mhd changes when I can (June 23rd). I do agree that n55 has superior cooling features though. |
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05-31-2017, 08:09 PM | #35 |
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Sorry, slightly off topic - but really?!
( I appreciate there IS plenty of margin before power is pulled but...) I thought we should be keeping oil around 120 deg c (240f) - not 145 (290f)! Are you running a stock oil cooler, and is it really okay to be running the N54 oil/engine that hot? |
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05-31-2017, 08:52 PM | #36 |
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What is the significance of this temperature?
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05-31-2017, 09:05 PM | #37 |
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When the N54 (stock) cooling system detects an ambient temperature of 108f / 42 Celsius, it puts the water pump and thermostat on overdrive and targets a coolant temperature of 85c (108f) rather than 106c (222f) normally.
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05-31-2017, 09:35 PM | #38 | |
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I subscribe to the aviation way of looking at limits - the green arc is there to be used. In the case of oil temperature, the green arc ends at 151°C (304°F). It may be preferred to run cooler than that, but running that hot is acceptable. Some driver's pathological desire for needles to be in the middle of green arcs has prompted some manufacturers to come up with creative gauge calibrations that provide just that placebo over a range of allowable temperatures. |
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08-20-2017, 11:55 PM | #40 |
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So what was the verdict on this? Is it to get mhd so the waterpump can be driven at optimal levels so then the rad can do its' job and a new csf rad is not needed?
What about the N55 cooling system is so much better than N54? Is the N55 oem rad better than the N54s?
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08-21-2017, 12:21 AM | #41 | |
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It means there's a now reasonable buffer between 'normal operating temperature' (90C) and 'damn, that water's hot' (120C). But if you're driving full noise around a hot track in a car pushing 30psi, your initial water temperature matters a lot less and your ability to shed heat in real time matters a lot more. So, for a daily driver, it's probably no longer worth it. For a track monster, upgrade your radiator. |
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08-21-2017, 02:43 PM | #42 | |
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08-21-2017, 06:58 PM | #43 | |
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