Hey, let's put the radiator in the rear!

Design of the coolant pump is more than adequate for the cooling requirements in the exxe. What often happens today, the gap between pump impeller and housing is excessive resulting in poor coolant flow at low engine RPMs. This is the reality of replacement parts today. Many of them are not OEM Fiat quality or any where near the OEM spec. There is a drawing in the Fiat Service manual that illustrated this gap and it's specified limits. Sort of remember the gap being 1mm, BUT this must be confirmed. The surface finish of the pump impeller also has an effect on coolant pump performance. It should be noted the OEM Fiat coolant pumps have a precision machined surface near the coolant pump housing area. The impeller surface while cast is smooth enough to meet the needs of what this pump does.

On the endurance race Lampredi SOHC, the coolant pump housing and pump front was checked for clearance and housing surface where the housing meets the pump front surfaced on a milling machine to achieve the Fiat spec for gap between the impeller and housing. It has been so long since that was done, no longer remember how much material was removed to achieve the specified gap.

The other significant modification was the under drive crank pulley. This modification is a non-option for a endurance race engine due to the near constant operation above 5,000 RPM hour after hour. Running the coolant pump at these RPM's can easily result in pump cavitation which significantly reduces coolant flow. The alternator also suffers as they are simply not designed to run at sustained high RPMs.

When the LeMons exxe was converted to a Mazda 12A PP race rotary, the stock coolant pump was used as is with under drive pulley. The radiator and associated cooling system remained in the front stock position. Coolant temperatures were quite acceptable. Oil temperatures were a completely different kettle of oil.

As for the box behind the radiator at the front of the exxe, it's shape and configuration has been specifically designed to produce air flow and plenum effect to aid cooling at speed (this design is the result of a LOT of wind tunnel testing and engineering work). Removal of this box has consequences for the stock cooling configuration. Cooling at idle depends on a OEM spec correct coolant pump (impeller to housing gap and proper impeller design and construction) the thermostatic switch and cooling fans.

Over the decades of exxe ownership since the late 70's, cooling or over heating was never a problem. They have been run over the hill into SoCal on over 100 degree F days at near full throttle with zero cooling problems. Stuck traffic in over 100 degrees F days with no cooling problems, endurance raced in over 100 degrees F summer Buttonwillow race track heat with a modified performance engine and zero cooling problems.

What is important, the cooling system in the exxe must be of OEM configuration and specification for the cooling system to function properly. Anything less is not gonna work.

Problem areas today due to sub standard parts and degradation of the cooling system are likely going to be, non-spec coolant pump, leaks in the cooing system due to pin holes in the main coolant pipes and other areas, steam erosion of the cylinder head resulting in pin holes between the combustion chamber to coolant passages, air in the cooling system, clogged radiator, questionable thermostat, non functional cooling fans and switch, slipping drive belt... any single one of these items can easily result in cooling system problems.


Bernice

I still say the biggest problem that Xs have with cooling is the fact that the water pump, which is really designed for the 128 has to struggle to push coolant the whole length of the car and back and further the metal pipes in the box under the car are enclosed and instead of acting like radiators, they just trap the heat in the coolant. Much like a 124 spider, if everything is functioning perfectly (rare in these old cars) then overheating should be rare.....there is just no margin for error.
 
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Design of the coolant pump is more than adequate for the cooling requirements in the exxe. What often happens today, the gap between pump impeller and housing is excessive resulting in poor coolant flow at low engine RPMs.
...
There is a drawing in the Fiat Service manual that illustrated this gap and it's specified limits. Sort of remember the gap being 1mm, BUT this must be confirmed.

According to the repair manual, the gap should be 0.031 to 0.051 in. (0.8 to 1.3mm).

What are your thoughts on what could occur if the gap was set too tightly versus being excessive? When I installed my new water pump I couldn't get the gap any wider than about 0.015in. The replacement part I used did not appear to be adjustable (impeller was pressed on instead of threaded). Don't have any cooling issues for what it's worth.
 
I agree with everyone concerning the time and money Fiat/Bertone put into optimizing the cooling system: It works for their specific parameters. Vehicle owners who want to modify their cars open up a lot of other parameters and individual owners could have different priorities. The front design is heavily influenced by the study employees in the 1960s. An individual owner might want a design slightly different than the OEM. This new design or modification might impede on the original cooling system air flow. Another parameter, vehicle owners now days do not have to worry about are manufacturing limitations due to operating in their own garage vs the Bertone assembly line. Perhaps today's owner cannot fabricate or weld the tunnel per OEM design. Or perhaps with new improvements on fans, radiant heat energy absorption prevention, radiator material or design can all make the OEM parameters not optimal anymore. Or more importantly, the $12 higher costs for one design over another isn't as important when n=1 compared to n=55,000 like I am having to take to higher management on an issue I'm dealing with today.

What I am saying the OEM system was painstakingly optimized for the design parameters given at the time. Today's owners might have different parameters.
 
:) Regarding a rear mounted radiator in the X. Now that we all agree this is the only way to cure all of the well established flaws with the stock cooling system, and that it is not only easy to do but absolutely necessary. Another benefit it offers is the resolve of another universally agreed upon flaw with the X's chassis design. With the radiator in the rear, and no silly coolant tubes running under the car, we can finally remove and eliminate that useless "box" structure under the car that adds absolutely nothing to the chassis stiffness. Nice when things like these are not only unanimously agreed upon but so simple to carry out.
Now if only we could all agree on which oil is the best to use. ;)
 
I have been designing coolers for construction equipment for the last 9 years and the typical bottleneck of almost all cooling systems is air flow.
That is what I have found limits performance every time we have designed something new.
Having the radiator up front will give you an abundance of air flow due to the ram air effect, it is probably possible to create the same air flow in an other position but it will be much more tricky to get the same air flow at the same speed.
 
:) Regarding a rear mounted radiator in the X. Now that we all agree this is the only way to cure all of the well established flaws with the stock cooling system, and that it is not only easy to do but absolutely necessary. Another benefit it offers is the resolve of another universally agreed upon flaw with the X's chassis design. With the radiator in the rear, and no silly coolant tubes running under the car, we can finally remove and eliminate that useless "box" structure under the car that adds absolutely nothing to the chassis stiffness. Nice when things like these are not only unanimously agreed upon but so simple to carry out.
Now if only we could all agree on which oil is the best to use. ;)

Bazinga!

The other solution, of course, is to move the engine to the front of the car to shorten the coolant path. I imagine the engine would have to be laid over at a severe angle to get it under the hood. The car would then be front wheel drive which we all know have better handling dynamics than a mid engine car.
 
Finally, Special K has come to the realization that extreme customization is the only answer. Indeed putting the engine in the front is the way to go. Everyone knows that's how a drift car is done. But you will need to mount it longitudinal and convert it to rear wheel drive. With the rad in the trunk naturally, where it gets more air flow.
 
It's enough to make you want to make a Meyers Manx. Simple, fun, cool looking and air cooled. When did they go from relatively cheap to staggering in price to build?
 
just my 2 cents on the point of engineers doing all of the testing and put it in the front. Automobile engineers are also limited by factors other than efficiency of the vehicle running at its optimum. for an example, when is the last time you worked on a car and found to change a simple part you have to practically take the entire engine out, where they could have engineered a hole, or a slight variance to make that part easily accessible? well it is possible that that slight variance would cost more than the return, as they look at after the sale work as not as important. they also factor in assembly. I cant remember which mustang you need to remove the engine to change the back 2 spark plugs, but betting it wasnt a major thought by the powers that be during the time it went down the assembly line. They also have to factor in the most important. Looks. How would it looks trumps performance at times. (had to put at times, as the original lamborghini lp400 didnt have the elephant ears in the back, was beautiful, but over heated).
So basically, I love this conversation and really wonder if putting a radiator in the rear would actually be better over all. This sparked my brain BTW because I saw a sand rail with a ford 2.3 in the rear on the raod. the sad par is the radiator was in the far back with the fan pulling air from the rear pushing it forward. would seem REALLY inefficient to me!

Odie
 
This sparked my brain BTW because I saw a sand rail with a ford 2.3 in the rear on the road. the sad part is the radiator was in the far back with the fan pulling air from the rear pushing it forward. would seem REALLY inefficient to me!
Odie

Caution: Old guy reminiscing story to follow -

I had built a single seat mid-rear-engine tube-framed autocross car. Absolutely flat bottom, sheet of aluminum, that terminated just behind the bottom of the drivers seat, in front of the unenclosed engine compartment. No bodywork, no nothing, except a frame and mid-engine VW air-cooled engine and transaxle, with the diff swapped to hang the engine out the front of the transaxle. After we blew up THAT engine (if you don't dry-sump an air cooled VW, when you pull a HIGH-G extended corner, all the oil moves to a cylinder cover, and starves the other side of the engine for oil... Once.), we pulled it out, had an adapter made, and installed a peripherally ported Mazda rotary. Where to put the radiator? Ended up that the best place to put the radiator was right behind the drivers seat, with the radiator fan pulling air INTO the passenger area, as the air from under the car, compressed, would curl up and forward after reaching the back of the flat floor into the relative uncompressed area on top of the floor. Air compressing and releasing is an entire study in and of itself.

We had a small firewall between the radiator and the engine area when we were done. Weird that no one required a firewall when we ran an 80hp air-cooled flat four, but DID when we had 200+ hp rotary. Go figger.
 
Caution: Old guy reminiscing story to follow -

I had built a single seat mid-rear-engine tube-framed autocross car. Absolutely flat bottom, sheet of aluminum, that terminated just behind the bottom of the drivers seat, in front of the unenclosed engine compartment. No bodywork, no nothing, except a frame and mid-engine VW air-cooled engine and transaxle, with the diff swapped to hang the engine out the front of the transaxle. After we blew up THAT engine (if you don't dry-sump an air cooled VW, when you pull a HIGH-G extended corner, all the oil moves to a cylinder cover, and starves the other side of the engine for oil... Once.), we pulled it out, had an adapter made, and installed a peripherally ported Mazda rotary. Where to put the radiator? Ended up that the best place to put the radiator was right behind the drivers seat, with the radiator fan pulling air INTO the passenger area, as the air from under the car, compressed, would curl up and forward after reaching the back of the flat floor into the relative uncompressed area on top of the floor. Air compressing and releasing is an entire study in and of itself.

We had a small firewall between the radiator and the engine area when we were done. Weird that no one required a firewall when we ran an 80hp air-cooled flat four, but DID when we had 200+ hp rotary. Go figger.

interesting. this one was way in the very back of the car. they attached the 2.3 to the vw trans, the engine hung out the back with the stock fan setup from the donor. because it was so far back, and there wasnt any body involved, I would assume that the air would settle wrapping around the engine going towards the rear. with the fan pushing back against the current flow. Myself, I would have put the radiator above the transmission. to grab air above the firewall form the seats to the engine/trans area.

Odie
 
It's enough to make you want to make a Meyers Manx.
I built a couple of those way back when they were cheap to do. But compared to my other off-road toys they weren't that great really. Very cool to cruise around town in though.
 
On the subject of off road cars. It is absolutely mind blowing what the guys are building these days. Sure, we expect pro racing "trophy trucks" to be exotic. But how about sand rails that play in the Glamis dunes? Mid-engine LS motors with twin turbos and nitrous, in an extremely lightweight tube chassis, tons of suspension travel with coil-overs, and huge paddle tires. Everything is custom built on these to handle the punishment they get. And no, the radiators are not mounted in the front. ;)
 
Some guys just like to turn on the garage AC and MIG welders and see what they can do...with apparent toy budgets around $40,000.
 
with apparent toy budgets around $40,000.
Ha, I stopped going to the Glamis dunes almost 15 years ago. At that time the better sand rails were costing roughly $100,000. Plus about two times that again for the motorhomes, and another $20,000 for matching enclosed trailers to take the rails there for the weekend. I can't imagine what it all costs now.
 
A few years ago I went to the Carlisle Import and Kit Car show and looked at a vendor who was selling components to make a Manx type buggy and was shocked at the prices he wanted. Granted you won't find a cheap Bug in a junk yard anymore...
I just want a simple one along the original intent to buzz around suburbia. Maybe it's time to cut the windshield off the Bertone and remove the doors and cut away the outer fenders.
 
The Manx type buggy made a big come back around 10-15 years ago. They came out with lots of new variations of it, including longer versions that do not require the VW's chassis to be shorted 12" (as all of the original styled one did). They also made them a bit more "modern"; more comfort/convenience features, better looking with cleaner style features, etc.. And all of the related accessories needed to build one were produced again. This prompted companies to restore old VW chassis with the drivetrain and suspension as complete units to sell for the builders of the buggy kits. As popularity and ease of building them improved, also came the higher prices for all of it. The more "exotic" ones were putting Subaru engines in the place of the VW engine (with the turbo version they had a TON of power for the weight). Also the suspensions were upgraded with that of the off-road race vehicles. And full tube chassis to go with that long-travel suspension. They got pretty radical. But I think the wave of popularity for Manx buggies has been on the decline over the last couple of years. So you could likely find one already built for less than the cost of the components. But it is still way more than an old VW is worth.

These examples are actually very conservative compared to many others:

manx class 9.jpg
ebay1041521.jpg
 
According to the repair manual, the gap should be 0.031 to 0.051 in. (0.8 to 1.3mm).

What are your thoughts on what could occur if the gap was set too tightly versus being excessive? When I installed my new water pump I couldn't get the gap any wider than about 0.015in. The replacement part I used did not appear to be adjustable (impeller was pressed on instead of threaded). Don't have any cooling issues for what it's worth.

I've been able to increase the clearance just by using a thicker gasket (cutting my own in at least one case).
 
Ha, I stopped going to the Glamis dunes almost 15 years ago. At that time the better sand rails were costing roughly $100,000. Plus about two times that again for the motorhomes, and another $20,000 for matching enclosed trailers to take the rails there for the weekend. I can't imagine what it all costs now.
In the 70's I used to go to Glamis on Turkey day weekend and Pismo on the 4th.
The group I went with ran Renault's.
The engines were water cooled straight 4's with the rad in the rear.
There were a few motor homes and some pretty nice buggies but mostly home made with materials on hand.
There was one guy in the group that had a credit card and wasn't afraid to use it.
He had built a few Renault buggies before so finally built a nice rail with a mid engine Old's bolted to (I think) a Porsche trans with a set of big brother Beckett's.
The radiator was rear mount.
My 63 Renault Caravel had the radiator mounted in the rear.
 
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