Engine fan

[SADLOTUS]

What is the general concensus of opinion amongst you lot out there about using a multiblade fan on the twincam? I used to run one from a Mexico/Escort years ago and it seemed to do a good job. I now wonder whether it would contribute to an earlier death for the water pump - All that centrifugal force on the bearings and seals compared to no fan at all.

I know I'd be robbing horsepower, and that there are plenty of electric fans I could use out there and they allow you to control the cooling system easier, but an engine driven fan is far more powerful.

I already have a large electric on the rad now and the cooling is marginal, so just wondering whether to supplement it with another, or a multiblade fan.

There's a pic of one in the gallery - engine in chassis next to 26R lookylikey.

All opions entertained!

[steveww]

If the cooling is marginal with an engine driven fan and an electric fan then I would suggest you look else where in the cooling system for the problem. If you have one of the later cars with the narrow radiator then upgrading to a full width radiator should solve your cooling problems.

My S4 has a full width radiator with a 10" electric fan and it maxed out at 95C while sitting in traffic with 36C ambient temp

[twincamman]

I removed the fan from the pump and replaced it with an electric one powered off the dash and free standing in the nose area ---BTW the chassis by the---' lookaliky'---- IS my chassis in the 26r s2# 33- [raced here at mosport and other tracks in the 60s and early 70s ]-- before mating to the body-------I removed the fan and ducted the air to the rad in the nose cavity - ---ed

[type26owner]

I've done the engineering of air-cooled heat exchangers before and it's not obvious what to do all the time. Doesn't anyone else have any expertise to share here to help these folks?

[twincamman]

Kieth ----I found by adding a floor and sides in the inside nose area and directing air into one of the old fat radiator [in the vein area ] the efficiency improves to the point of a thermal exchange that saved my motor last summer on the way home from a car meeting -----the fan belt had fallen off and with the electric fan running and a stout oil cooler in the front I made it home just off the boil at 60 mph steady on the high way - ----ed

[alaric]

A fairly unobtrusive way to improve the performance of the existing radiator may be to pump the water round a bit more forcefully, especially when sat in traffic with the engine idling. There are a number of electric water pumps (EWP) around, that fit into one of the radiator feed pipes, and come with an electronic controller that'll change the pump rate with the coolant temperature.

The idea is that the higher pump rate leaves more of the radiator at a higher temperature i.e. the temperature gradient from top to bottom is more even. Since the heat loss is proportional to the temperature difference between the radiating surface and ambient, this should help. A quick calculation to estimate the heat loss as a function of pump rate would indicate the potential benefit of this approach. I haven't had time to think this through yet and come up with a performance plot.

With this approach instead of the fan replacing the air around the radiator with new cool air, the EWP replaces the water in the rad with fresh hot water, the idea being to maintain the temperature difference between ambient and the hot thing. This approach may actually be more effective than just blowing harder with a fan.

I was thinking that this could operate in addition to the existing water pump, and may only be required when the engine gets hot in traffic.

Hope this is of interest.

Sean.

[twincamman]

yes the option of an electric water pump occured to me but the mounting and plumbing involved sort of discouraged that idea -----but I just realized the pump can be anywhere in the car not just in the rad area -- -ed

[type26owner]

Sean is right in a water to air heat exchanger the problem is always with the getting the air to carry off enough heat. The heat carrying capacity difference between them is like 150 to 1. You can't move the water too fast either. Anyone that claims that has a glass belly button.

If I had one of the later smaller radiators and wanted to cure the overheating once and for all. I'd install a 'balanced' thermostat to increase the water flowrate. Change the rad cap to a 15psi one and increase the boilover point to 125C. Run the engine between 100-115C. Build a plywood ducted shroud to force at least 1000cfm of air through the radiators' entire matrix core. If you do these things I'd guess you'll increase the total amount of heatload that the EXISTING cooling system get handle is by a factor of four. Simple application of the laws of thermodynamics. Make them work for you instead of against.

The 78C thermostat callout in the Lotus Workshop Manual is a cruel joke.

I've heard rumors that the F1 engines are using 50+psi cooling systems these days. They should ditch that technology entirely and go right for a heatpipe one instead. 57 more days to go till Bahrain. I can make it...I can make it........I can make it I hope

[type26owner]

The Felpro headgasket can handle the extra expansion coefficient motion and not leak in my experience. Not sure if the Payen copper/aluminum one is up to it though.

The tendancy to detonate goes up with increasing operating temperature so having the AFR and the timing correct becomes more critical. Sorry, but that's a fact.

[worzel]

Not for the purists this one but- a Citroen BX19 fan fits quite nicely on both narrow and full width radiators. In terms of power put one down on the ground and connect to a battery then chase it around the floor- does a good hovercraft impression.

Cost- about ?15-20 from a breaker. You need to rig up some sort of fixing arrangement but this isn't too difficult.

Does it work- let the temp rise to about 95 and switch on- drops to 75 in less than a minute. Draws a huge current though so relay feed is vital.

John