Aftermarket radiator fans.
08-20-2015, 12:15 PM
#61
Rainman
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I wonder if one fan would do the job 
http://www.classicshop.porsche.com/p...410614102.html
Also, a replacement shroud is way cheaper than I thought it'd be.
http://www.classicshop.porsche.com/p...410614302.html
http://www.classicshop.porsche.com/p...410614102.html
Also, a replacement shroud is way cheaper than I thought it'd be.
http://www.classicshop.porsche.com/p...410614302.html
08-21-2015, 09:19 AM
#62
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Some really good info in this thread.
So, if I read this correctly, looks like the fan shroud is probably biggest and easiest to fix culprit that can have a significant impact on coolant temps.
So, if I read this correctly, looks like the fan shroud is probably biggest and easiest to fix culprit that can have a significant impact on coolant temps.
08-21-2015, 12:39 PM
#63
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In my experience, absent an obviously malfunctioning part, the single biggest thing to keep the temps down is...everything. Every little inefficiency adds up: thermostat flow and set point, internal bypass seal, internal and external radiator blockages, coolant mixture, engine tune, fans speed and set points, air/leaks in system, front mounted coolers, ducting and probably other stuff not coming to mind. George's car is all fresh so he probably needs to look further down the list to notice improvements...
08-21-2015, 03:36 PM
#64
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Maybe, but how hard is it to quantify a lack of cooling to a small gap or misalignment of the fan shroud? Especially if a mere 1/8" gap can have such a pronounced effect?
08-21-2015, 09:47 PM
#65
Drifting
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Hey Jay,
I'm no expert, but the folks at Ron Davis towards radiators within the motorsports racing community, and any gaps will cause the proverbial: Path of least resistance. When my fans were on high, I lit a cigar and saw the smoke get SUCKED into the gaps vs sucking through the radiator. So, the smoke test says, gaps need to be closed.
I'm no expert, but the folks at Ron Davis towards radiators within the motorsports racing community, and any gaps will cause the proverbial: Path of least resistance. When my fans were on high, I lit a cigar and saw the smoke get SUCKED into the gaps vs sucking through the radiator. So, the smoke test says, gaps need to be closed.
10-02-2015, 05:38 PM
#66
Rainman
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On a separate note, here is a worthwhile coolant system upgrade I've recently done. This mod removes the T-stat from the water pump all together and has it relocated to the outlet of the radiator via a remote housing. Along with this, a new water pump gasket is used to promote the return flow from the radiator to pass through the head instead of taking the path of least resistance and allowing much of the incoming cooler fluid to bypass to the front side of the impeller.
The remote T-stat housing has a bleeder hole drilled in its flange to promote flow past it for the warm-up cycle. I've added a one-way check valve to the front side of housing to allow for any build up of fluid in the reservoir to make its way back into the coolant circuit.
In the hot AZ summer, my coolant temp stays rock solid and barely goes over the first temp line on the gauge. With A/C running and the cooling fans on high speed mode, the temps are always in check.
This mod was passed over to me by a long time 951 racer who has retrofitted this mod to several race cars. One of the advantages of doing this is that the coolant flow in the cylinder head is purposely increased due to the restriction placed in the water pump gasket. The flow of coolant is forced through the head now promoting a greater safety margin from heat build up at the #4 cylinder where a lot of head gasket failures occur.
On top of that, with the T-stat removed from the front of the impeller, the pump can perform better and has less chances of cavitating due to having the restriction directly in front of it. They have recorded an increase in system pressure due to greater impeller efficiency - up to 17 psi from 12 psi.
The feedback I have been given over the past couple of years of this mod being in use is that common head gasket failures seen in the past have disappeared with a group of 5 race cars that have moved to this.
Thought I'd share. Sorry that this isn't about different cooling fan options, but it's somewhat related :-)
The remote T-stat housing has a bleeder hole drilled in its flange to promote flow past it for the warm-up cycle. I've added a one-way check valve to the front side of housing to allow for any build up of fluid in the reservoir to make its way back into the coolant circuit.
In the hot AZ summer, my coolant temp stays rock solid and barely goes over the first temp line on the gauge. With A/C running and the cooling fans on high speed mode, the temps are always in check.
This mod was passed over to me by a long time 951 racer who has retrofitted this mod to several race cars. One of the advantages of doing this is that the coolant flow in the cylinder head is purposely increased due to the restriction placed in the water pump gasket. The flow of coolant is forced through the head now promoting a greater safety margin from heat build up at the #4 cylinder where a lot of head gasket failures occur.
On top of that, with the T-stat removed from the front of the impeller, the pump can perform better and has less chances of cavitating due to having the restriction directly in front of it. They have recorded an increase in system pressure due to greater impeller efficiency - up to 17 psi from 12 psi.
The feedback I have been given over the past couple of years of this mod being in use is that common head gasket failures seen in the past have disappeared with a group of 5 race cars that have moved to this.
Thought I'd share. Sorry that this isn't about different cooling fan options, but it's somewhat related :-)
can you please explain the function of the original coolant channel that is now blocked off with your mod?
my understanding was it is a recirculation path for the coolant, to run through the block and head and then through that hole, back to the "inlet" of the pump to run through again and help warm-up...with that channel blocked can any recirculation happen?
10-02-2015, 07:19 PM
#67
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The original coolant passage isn't blocked off completely - it is now restricted. This passage is meant for recirculating the coolant in the block when the t-stat is closed / engine in warm up cycle.
The purpose of the mod is two fold - repositioning the t-stat from being directly in front of the water pump increases efficiency in flow and the revised MLS gasket promotes better coolant flow in the head.
Think about how often head gasket failures occur at the #4 cylinder. This is because of the buildup of heat in the coolant (among other variables). Coolant gets very heated by the time it reaches the back of the head and flow, or lack thereof, create a situation for trouble.
The revised gasket redirects incoming flow from the radiator from bypassing to the front water pump. This prevents a large amount of coolant from bypassing flow through the head altogether. The recirculating passage when unrestricted allows the coolant the option of passing thru the water pump housing directly when incoming from radiator. Now, the restriction in the gasket forces the majority of flow coming from the radiator to pass through the head, improving cooling overall.
To address the warm up cycle, the bypass hole in the gasket and additional bypass hole drilled in the flange of the T-stat allow flow to circulate both trough the block and through the radiator. I added a hose feed from the steam vent mod to feed coolant directly in front of the t-stat. This supplements flow to the remote housing to assist with the warm up cycle.
Hope this helps. It's been a great mod for my car.
The purpose of the mod is two fold - repositioning the t-stat from being directly in front of the water pump increases efficiency in flow and the revised MLS gasket promotes better coolant flow in the head.
Think about how often head gasket failures occur at the #4 cylinder. This is because of the buildup of heat in the coolant (among other variables). Coolant gets very heated by the time it reaches the back of the head and flow, or lack thereof, create a situation for trouble.
The revised gasket redirects incoming flow from the radiator from bypassing to the front water pump. This prevents a large amount of coolant from bypassing flow through the head altogether. The recirculating passage when unrestricted allows the coolant the option of passing thru the water pump housing directly when incoming from radiator. Now, the restriction in the gasket forces the majority of flow coming from the radiator to pass through the head, improving cooling overall.
To address the warm up cycle, the bypass hole in the gasket and additional bypass hole drilled in the flange of the T-stat allow flow to circulate both trough the block and through the radiator. I added a hose feed from the steam vent mod to feed coolant directly in front of the t-stat. This supplements flow to the remote housing to assist with the warm up cycle.
Hope this helps. It's been a great mod for my car.
10-02-2015, 07:47 PM
#68
Rainman
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If that passage were blocked off completely, wouldn't the water still be able to recirculate via the relocated-thermostat bypass?
Lower rad->water pump inlet->cylinders->back up through the head->coolant gooseneck->thermostat->upper rad
bypass on either side of thermostat...the hole in the revised gasket is pretty small, so i'd imagine a small ID hose would do the same function with fittings either side of the T-stat.
Lower rad->water pump inlet->cylinders->back up through the head->coolant gooseneck->thermostat->upper rad
bypass on either side of thermostat...the hole in the revised gasket is pretty small, so i'd imagine a small ID hose would do the same function with fittings either side of the T-stat.
10-02-2015, 08:12 PM
#69
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Take a closer look at the coolant path and maybe things might make sense.
I think you are looking at the flow backwards. Flow goes out of the pump housing to the lower radiator connection then out to the top of the head. This is where the coolant has the option of taking the path of least resistance - out the recirculating port to the front of the impeller and some passing through the head.
Flow goes on the top of the head to the back @ #4 where it makes the turn down into the block. Coolant flows back to the water pump where it gets pushed out to radiator.
I think you are looking at the flow backwards. Flow goes out of the pump housing to the lower radiator connection then out to the top of the head. This is where the coolant has the option of taking the path of least resistance - out the recirculating port to the front of the impeller and some passing through the head.
Flow goes on the top of the head to the back @ #4 where it makes the turn down into the block. Coolant flows back to the water pump where it gets pushed out to radiator.
10-02-2015, 09:07 PM
#70
Rainman
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Maybe I'm reading this wrong but it sounds like you're describing a reverse-flow cooling system like the Chevy LT-1 engine of the early 1990s...where coolant runs through the head before going down to the cylinders.
The 944 system pulls water from the lower radiator hose, past the thermostat, then pumps the water around the cylinders, then up the head gasket channels (at cyl#4) into the head, and out the upper radiator hose back to the radiator. The volute shape of the block side of the water pump area supports this flow direction.
My understanding is that, the port on the block that gets mostly blocked off by the new gasket is a bypass route for water that would otherwise flow from the head to the upper radiator hose. This water instead gets routed through the front of the water pump housing into the impeller to be pumped through the cylinders/head again. This water cannot go out the upper radiator hose because the other end of the system is blocked (mostly) by the thermostat at the stock pump inlet.
My thought is that the mostly-blocked passageway means that water in the cylinder head must be sent out the upper hose to the radiator instead of being partially diverted back through the system...which would mean that the average coolant temperature inside the engine would be cooler than normal (since there is not any water already heated up by passing through the engine being recirculated a second time). That, combined with the relocated thermostat, means that the water pump is probably pushing a higher volume (due to lower "head losses" aka pump inlet restriction of the original thermostat) of cooler fluid through the block.
The 944 system pulls water from the lower radiator hose, past the thermostat, then pumps the water around the cylinders, then up the head gasket channels (at cyl#4) into the head, and out the upper radiator hose back to the radiator. The volute shape of the block side of the water pump area supports this flow direction.
My understanding is that, the port on the block that gets mostly blocked off by the new gasket is a bypass route for water that would otherwise flow from the head to the upper radiator hose. This water instead gets routed through the front of the water pump housing into the impeller to be pumped through the cylinders/head again. This water cannot go out the upper radiator hose because the other end of the system is blocked (mostly) by the thermostat at the stock pump inlet.
My thought is that the mostly-blocked passageway means that water in the cylinder head must be sent out the upper hose to the radiator instead of being partially diverted back through the system...which would mean that the average coolant temperature inside the engine would be cooler than normal (since there is not any water already heated up by passing through the engine being recirculated a second time). That, combined with the relocated thermostat, means that the water pump is probably pushing a higher volume (due to lower "head losses" aka pump inlet restriction of the original thermostat) of cooler fluid through the block.
10-02-2015, 09:32 PM
#72
Rainman
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More, cooler water is the key to engine life...whoda thunk it
But my last question, re: blocking that passageway entirely...I think it should be OK as long as there's a bypass somewhere else in the system, maybe tapping between the upper radiator hose and the "turbo water inlet plate" on the front of the water pump...
The real reason for this wondering of mine is...if that passageway can be (reliably) blocked off completely, and a bypass still maintained...it would no longer matter what cylinder head was on what engine block, regarding 2.5 vs 3.0 parts, as long as the head's passage could be blocked off.
But my last question, re: blocking that passageway entirely...I think it should be OK as long as there's a bypass somewhere else in the system, maybe tapping between the upper radiator hose and the "turbo water inlet plate" on the front of the water pump...
The real reason for this wondering of mine is...if that passageway can be (reliably) blocked off completely, and a bypass still maintained...it would no longer matter what cylinder head was on what engine block, regarding 2.5 vs 3.0 parts, as long as the head's passage could be blocked off.
10-02-2015, 10:26 PM
#73
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My apologies for misquoting the direction of flow, but the point of the mod still remains the same - to prevent flow of hot coolant at the front of the head from "recirculating" back in front of the impeller and back into block. Flow with new gasket forces coolant to make 90 degree turn upwards through to the radiator allowing better overall cooling of the fluid.
10-02-2015, 10:39 PM
#74
Rainman
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My apologies for misquoting the direction of flow, but the point of the mod still remains the same - to prevent flow of hot coolant at the front of the head from "recirculating" back in front of the impeller and back into block. Flow with new gasket forces coolant to make 90 degree turn upwards through to the radiator allowing better overall cooling of the fluid.
I think the initial confusion was from my "flow path" not being labeled appropriately.
Thank you for sharing this...it opens up a new world of potential
10-04-2015, 07:09 PM
#75
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We did something similar, but different. Our 2.5 motor was definitely seeing some boiling. We even 'boiled' the Evans coolant. When I say boiled, we saw temps over 200f where we want them to be around 175f. This could have been a symptom or cause of headlift and gasket leaking issues. Michael Mount kindly made some suggestions (as had Vic previously) and we revisited the water passages in the deckplate which were different (less) than on the previous motor which didn't suffer the same issues. So we opened these up but we also removed the stock T-stat and went with something from a Supercar V8 that Paul had in the shop. It sits directly on the radiator which runs with the top 4 rows running permanently. When the T-stat opens, the water now bypasses a baffle and the whole radiator opens up. We had it back on the dyno again yesterday (warm day) and the car just sat on 173f / 80c without budging. Big success for us and means we can crank the boost up over 18-20psi where it was leaking before. Simple but effective mod. We also blocked off the water jacket up at the top of the block with an alu plate and plastic steel epoxy.