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Old 09-11-2015, 11:53 AM   #21
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Quote:
Originally Posted by dcamp2 View Post
From the Miata Cooling System thread in the Race Prep area:
--------------------------------------------------------------------------------------------
Head gasket
Mazda recognized the cooling issues and altered the head gasket in the 01-05 "NB2" VVT (BP6D) engines. This change restricted the coolant flow to 1-2 cylinders thereby increasing flow to 3-4. Bandaid fix that doesn't really solve the problem of the backwards coolant flow. It's OK to use a reroute in an NB2 engine. If you have the engine apart already, further improvements in flow can be made by swapping in the 94-00 # BP26-10-471 head gasket. We run this HG on all of our VVT engines.
--------------------------------
As Vlad pointed out, this is a matter of opinion. To date, no one has instrumented a VVT head to measure the temperature gradiant across it while running a rear-therm setup with the stock head gasket. So we can only speculate thusly:
  1. The rear-therm reroute is designed to solve the problem of a majority of coolant flowing straight up from the water pump and right out the front of the head again, without circulating through the rear of the engine. It does this by re-establishing the coolant path which the B6/BP engine was originally designed with in the FWD applications for which it was developed.

  2. The change to the HG design in the '01-'05 Miata engines effectively eliminates this problem by forcing the coolant to take the long way through the engine, back into the #2/3 area in order to flow up and out of the front of the head. Thus, performing a rear-therm reroute solves a problem which does not exist in these engines.

  3. At best, there will be no significant improvement in cooling performance by doing a rear-therm reroute on an engine with a stock '01-'05 head gasket. At worst, the resultant stagnation of coolant all around the #1 chamber and towards the front of the #2 chamber will cause the front of the head to run significantly hotter than the rear, effectively creating a mirror-image of the problem encountered on the '90-'00 engines in stock form.


We have empirical evidence from a few people who have done rear-therm reroutes on VVT engines with stock head gaskets which shows that this doesn't result in immediate, catastrophic failure. I posit, however, that this modification does not significantly improve the cooling performance of these engines, and may in fact seriously degrade it, causing the front of the head to run significantly hotter than the measured coolant temperature, and decreasing the margin of safety for overheating.
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Old 09-11-2015, 02:09 PM   #22
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I've run lots of race hours on unopened BP6D motors with reroutes. It's fine.
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Old 09-11-2015, 05:09 PM   #23
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I've run lots of race hours on unopened BP6D motors with reroutes. It's fine.


:like cat:
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Old 09-11-2015, 09:27 PM   #24
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Quote:
Originally Posted by Zaphod View Post
- OEM undertray with intake for engine oil-cooler on steering rack
I think the effect of this is to add pressure behind the radiator and impede cooling.

From a theory standpoint, I've never liked that FM steering rack-mounted oil cooler design. Local friend of mine who installed one for track duty had poor results.
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Old 09-12-2015, 02:29 AM   #25
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Quote:
Originally Posted by Savington View Post
I've run lots of race hours on unopened BP6D motors with reroutes. It's fine.
Then with your experience, would you say it helps over the stock setup?
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Old 09-12-2015, 04:13 PM   #26
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Quote:
Originally Posted by hornetball View Post
I think the effect of this is to add pressure behind the radiator and impede cooling.

From a theory standpoint, I've never liked that FM steering rack-mounted oil cooler design. Local friend of mine who installed one for track duty had poor results.
Poor in what way? Not enough cooling?

The two issues with the FM mount are protecting it from rocks (under tray is pretty good at this) and there's only enough room for a fairly small cooler.

--Ian
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Old 09-12-2015, 07:40 PM   #27
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Small cooler.

-8 lines.

Either in an extemely low-airflow area or, if you pipe air to it, you compromise delta-P across the radiator.

Street bling for the m.net crowd IMHO. YMMV.
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Old 09-13-2015, 02:25 PM   #28
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Quote:
Originally Posted by hornetball View Post
Small cooler.

-8 lines.

Either in an extemely low-airflow area or, if you pipe air to it, you compromise delta-P across the radiator.

Street bling for the m.net crowd IMHO. YMMV.
Seems to work OK on my car on the track, although I only used the bracket (I'm using -10 lines and cooler). I don't have definitive before/after oil temp numbers, though.

--Ian
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Old 09-16-2015, 11:04 PM   #29
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Dcamp2, let me know how the re-route works with the BP6D head gasket.
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Old 09-16-2015, 11:10 PM   #30
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Tracked down some factory fans. Going to see what they do first. Then will buy an OEM undertray and see what that does. If those don't fix it, then I'm going for the re-route. Will probably use the one from 949 so that I can continue to use the EGR tube.
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Old 09-27-2015, 04:38 PM   #31
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Quote:
Originally Posted by dcamp2 View Post
From the Miata Cooling System thread in the Race Prep area:
--------------------------------------------------------------------------------------------
Head gasket
Mazda recognized the cooling issues and altered the head gasket in the 01-05 "NB2" VVT (BP6D) engines. This change restricted the coolant flow to 1-2 cylinders thereby increasing flow to 3-4. Bandaid fix that doesn't really solve the problem of the backwards coolant flow. It's OK to use a reroute in an NB2 engine. If you have the engine apart already, further improvements in flow can be made by swapping in the 94-00 # BP26-10-471 head gasket. We run this HG on all of our VVT engines.
--------------------------------------------------------------------------------------------

I looked because I just swapped in a NB2 with reroute and didn't want to crack it open to swap headgaskets.




OP- to keep my Rotrex car cool on track I've done the following:

-Coolant reroute
-Big radiator (trackspeed)
-Big oil cooler (trackspeed)-Seal all gaps around radiator
-NO fan shrouds- just one stock fan

This keeps my car cool on hot days (90 f) at 5000 feet elevation where the air is thin and dry (bad for cooling)
-Remove A/C condenser

This is what I did also. I had a lot of issues prior to this. When you remove the AC condenser that allows you to push the Rotrex oil cooler back, which allows you to push the FMIC back which allows more air to get to the radiator
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Old 10-08-2015, 05:29 PM   #32
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Wasn't really looking to pull out the AC but it's certainly sounding like that may be one of the options I have to pursue.
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Old 10-11-2015, 06:11 AM   #33
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Airflow through the radiator requires pressure differentials. At the moment there are several things working against you to minimize your pressure differential:

a) the replacement undertray does nothing but act as a fancy skidplate. It has no sides at all. The wheel wells are high pressure areas, so that pressure is also behind your radiator. The OEM undertray encloses the entirety of the bottom of the engine bay, and has a couple of nifty diffuser exits at the very back to extract air.

b) fan shrouds are a mistake for hard-driven miatas. At speed, they restrict airflow.

c) you need a real fan. "A", one, uno, real fan. This single spal cooled my car at idle just fine with no shroud (stack was IC/rotrex cooler/AC condenser/radiator; radiator was FM crossflow): Spal 3010.2029 Spal 3010.2029.

There is a huge difference between a random 12" radiator fan and a real fan designed to move air through a restrictive stack of heat exchangers under load.

d) your FM oil cooler is causing two problems. 1- the 8an lines are causing you restriction and pressure drop unsuitable for a car driven hard. 2- the placement and the "air scoop" are again increasing pressure BEHIND your heat exchangers, which is the opposite of what you want.

Mobius' solution to your cooling needs:

Buy the spal 3010.2029. Remove the FM oil cooler, sell it on m.net for profit. Use the stock undertray. At this point your radiator should be ok; if not TSE radiator and you're done. Or supermiata crossflow, or FM crossflow.

It's all about pressure differential, and at the moment you have very little.

Caveat - my car had AC but I rarely had to use it for prolonged temperatures in hot, traffic-jam type conditions. If you experience those conditions, you might want to add the spal 3010.1522 Spal 30101522 at Jegs
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Old 10-11-2015, 12:44 PM   #34
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Mobius - thanks for the info. I've already removed the shrouding and installed the OEM fan. This alone made a huge improvement. I've gone ahead an ordered the M-tuned reroute also and will be picking up the OEM under tray from the dealer next week. With regards to the Rotrex oil cooler - you mention removing it and selling it, what would it be replaced with and where would that be mounted?
Appreciate the insight - thanks
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Old 10-11-2015, 01:04 PM   #35
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He said FM oil cooler
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Old 10-11-2015, 07:03 PM   #36
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Oh, he must of have misread then, because I don't have an FM oil cooler, just the Rotrex oil cooler. Thanks
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Old 10-11-2015, 07:17 PM   #37
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Oh yeah sorry Zaphod has the FM cooler (Zaphod get rid of it )

The other thing I didn't mention is ducting. Seal your exchanger stack together. Give the air only one path - through the exchangers. You can get the bottom and partway up the sides pretty easily with vinyl tub & shower liner from Home Depot Racing, and some aluminum HVAC tape:



Some foam window insulation on the sides of the radiator. A cover to seal over the gaps at the top between the radiator and the bumper. Things like that will go a long way and are quite inexpensive.
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Old 10-11-2015, 11:09 PM   #38
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Along those lines, the replacement air guide I built is working well.

https://www.miataturbo.net/build-thr...8/#post1244564
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Old 10-12-2015, 12:04 AM   #39
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@gsyk59 my car runs cool on track.

20 minutes of driving as hard as I can (personal best 5 seconds under SM record) temp gauge doesn't budge. Temp was about 75 at 5000ft elevation.
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Old 10-12-2015, 03:58 AM   #40
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Quote:
Originally Posted by Mobius View Post
Oh yeah sorry Zaphod has the FM cooler (Zaphod get rid of it )
Will do over the winter - but I'd like to keep the oil cooler - so where to put it instead? Behind the water cooler? In front of the passenger side wheel with an air duct coming from the radiator opening?
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