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Are you sure both fans are working properly? If you're not overheating at speed when air is being forced through the heat exchanges, then I'm thinking air isn't being sucked through at idle/low speed. It wouldn't be the first time fans have died and cause overheating.
For the purposes of this conversation, the blocks are all identical from 94 to 2005. The issue comes in the cylinder head.
94-00 head with BP26 94-00 head gasket: OK
01-05 head with BP26 94-00 head gasket: OK
01-05 head with BP6D 01-05 head gasket: OK
94-00 head with BP6D 01-05 head gasket: Not OK
The MSM head is a freaky one - it can be accurately described as either "a '99-00 head with 01-05 coolant ports and a unique intake cam" or "a 01-05 head without VVT and a unique intake cam".
Originally Posted by Savington
I haven't heard of that testing done either. I will say that Thumper uses a BP6D gasket (01-05) and a reroute and it hasn't blown up in spectacular fashion yet.
One more note on the differences between VVT heads and '99 heads. When Mazda changed the head gasket design, they added several cooling ports to the surface of the 01+ head (including the MSM). As a (likely unintended) result of this, nearly every coolant port on a 99-00 head ends up blocked off if you use a 99-00 head with an 01+ gasket. Out of 17 total ports, eleven of them end up blocked, with cylinders #1 and #2 sharing a single coolant port between them. Not good at all.
The ports in red are blocked:
If you were thinking about using a BP6D gasket on your early engine to forego a reroute, don't.
Originally Posted by slmhofy
To reiterate Andrew's point, I modified these pictures to help explain it in a way I can visualize better. And the emphasis in these pictures being on the blue circles.
Basically you're looking at only 6 water ports being used if you use the later model BP6D head gasket with the true 99-00 head.
Compared to 11 water ports being used when you use the later model BP6D head gasket with either a MSM/VVT/or late model(99-00,MSM) replacement head.
The reason I have such an interest in this is because I am indeed running the bad combination. I wasn't completely aware of this issue early last year when I built my motor. My late model replacement head was getting worked on so I bought a 99-00 head to hold me over for a while. Not being fully aware of the water port configuration, I just slapped on a BP6D gasket on there.
I haven't had any overheating issues per se, but I can clearly see why this is such a bad setup. Cylinders 1/2 aren't getting any water! The new head is ready to go on so I'll be fixing the situation soon, running later model head with BP6D gasket.
Sorry for the rants in Emilio's thread. Just figured this could help someone in the future.
So after reading all of this I need to ask for a little clarification.
I'm working on a 99-00 BP-4W.
I bought a head gasket at a local miata shop that runs SM, and claims they use the BP6 01-05 head gasket in all of their builds. They sold me this to use in the car I am putting together tonight.
Can anyone (slmhofy included) who has run this setup verify that it worked well enough as a street setup?
I'd hate to put it all together tonight just to have to pull out the headgasket when it starts overheating cylinder 1.
I understand the shop's logic, that forcing the water to go out through the rear of the head forces more cooling of the number 4 cylinder the problem on the previous generation, due to proximity to the firewall and the coolant neck up front, but is it so bad to run this combo that I will encounter detonation/accelerated wear issue down the road as a result of inadequate cooling of cylinders 1&2?
I need to get this done tonight, so I may be the guinea pig for this venture.
Spec Miatas are not allowed reroutes so this shops experience is likely limited. BP6D gasket works fine with rear exit reroute. BP4W/BP05 gasket works better.
The shop has pushed in the past for me to run a VVT head, so I assume their limited experience revolves around the use of this particular setup, SM VVT head, 01-05 HG, No Reroute.
I'm not running a re-route on this head, do I need the BP26 HG?
The water moving through the back of the head has to go past cylinders 1&2 to get out of the thermostat neck (if it doesn't exit through the heater core), it'll just be a bit hotter due to coming into contact with the rearward cylinders first.
I'm thinking this could work fine. Unless there's evidence to say otherwise.
Originally Posted by emilio700
Spec Miatas are not allowed reroutes so this shops experience is likely limited. BP6D gasket works fine with rear exit reroute. BP4W/BP05 gasket works better.
If it works fine with the rear exit reroute then it should work at least as well, if not better, minus the reroute due to the fluid needing to flow past cylinders 1&2 in a system without a reroute, and not needing to do so if the thermostat had been moved to the back of the head.
After reading the first 25 pages or so I think I got most of the info I was looking for...
I am building a w2w track car from a 1990 that has a 2004 NA1.8vvt swap in it with a MS3.
It had a interesting cooling re-route done.. the front hose was tee'ed into the re-route hose.. bet you haven't seen that.
Had an aluminium rad with 2 fans and a shroud. The heater circuit was eliminated with the return line from the heater attached to the reroute fitting.
I wasn't happy with any of it so... before reading the post I was going to replace the head gasket with the older 1.8 gasket, and redo the reroute as the inline t-stat housing was welded together due to a leak.
I guess that's why the front housing was still in play as the t-stat was in there.
The aftermarket rad and fans set-up was in contact with the sway bar as well.
I relocated the rad mounts when I added upgraded sway bar mounts, deleted the shroud and one of the fans, I have replaced the coolant mixing fitting completely and added a single fitting for the lower rad hose,
The plan now is to complete the re-route with a rear t-stat housing and drill the t-stat out and leave the stock head gasket for now. I will cap the front of the block, add an oil filter relocate, an oil cooler. and hood vents. Do you guys see any glaring issues?
It's super easy to fix. That thermostat neck should be able to be removed from the head. The opening can then be plugged with a freeze plug available at any auto parts store. It's the same size diameter as the other freeze plugs in the head, and they make them out of zinc, a perfect match, just remove the neck and tap it a plug.
You may need to remove the plate behind the timing belt to get to the bolts holding the neck on, but it's worth it to fix the botch job.
Make sure you have a T-stat inline at the hose near the back of the head though.
If the conventional downflow really can work with a 300whp car in SoCal, it will certainly work for my really well ducted car with <300whp in Europe.
I've not run into any cooling issues with cheap components and basic recipe
- Large bonnet vents
- Reroute
- Thorough ducting sealed to bumper, even a twin scroll arrangement for IC
- Tubular bumper bar
- Basic 50mm IL Motorsports radiator
But I am thinking for the relatively low effort (no need to redo my over the rad intake pipework with a downflow), I am tempted by the CSF for a bit of extra headroom for Spa and Nurburgring next summer.
Tran, I can attest to the capability of the crossflow vs cheaper options. It offered a noticeable improvement in the efficiency and effectiveness of engine cooling for my car.
My setup has similar points to yours:
- 300whp
- bonnet vents
- reroute
- ducting
I'm located in the south eastern area of Australia, where ambient temps are typically somewhere between 15-35deg C.
Temps now with the Supermiata crossflow, are almost always a steady 85degC. (Target temps set by ECU controlled electric water pump / no traditional mechanical thermostat).
The cost was exorbitant to purchase and ship a fairly large part all the way from the USA, circa 4x the price of a generic aluminium ebay radiator that would work fine for most 'normal' cars.
But in the end, for me, it was worth it.
Is there any benefit to engine and/or underbonnet and/or cabin temps in adding an extra sideways bonnet vent behind the turbo and exhaust manifold?
I assume something like this is what you are asking about? I'm sure emilio would know more but I think it is a higher pressure zone near the rear of the hood on an NA so probably wouldn't be the best location for a vent.
10-09-2019, 08:05 PM
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