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253 - an efficiency oddessy

I've just finished the last of the tweaks to my 253. In a pretty short period of time I've exchanged the WW stromberg for a near new quadrajet, built a cold air intake, removed the clutch fan and replaced with twin 12" thermos, added electronic ignition and an electric water pump.

Power output is now a tad over 120kW at the rear wheels but the really satisfying part is how the motor wants to rev and the power delivery. You can really notice that there are less things to "accelerate" - I suppose its like the effect of lightening the flywheel. Not having the clutch fan and the water pump combined with how well the 4-barrel manifold and quaddie flows on a 253 really turns a torquy motor into a little screamer.

I'd love to know what the fuel economy is like if driven sensibly but everytime I take it for a spin I can't help putting the foot to the floor! As the revs build it just pulls harder and harder. It just doesn't let up until its time to change gear (about 4800 is where peak HP's at). Even if you hold a gear a bit longer and use some of the over-rev you don't feel much of a loss of acceleration.

Basically I'm pretty bloody happy and would recommend these mods to anyone whose 253 feels a little "choked". Actually, I'd probably not recommend the twin 12" thermos. They seem to be having some difficulty keeping things cool. I'm running them without a shroud using a custom fabricated aluminium brackets. I think that a shroud is probably essential to get them working at their best.

Does anyone know of a thermo fan/shroud set-up that will fit the HZ radiator? I was going to use a set-up off a Gen III but it was too big to fit. I've heard rumours that a f@#d AU electric fan/shroud is the go? Anyone got any ideas?

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AU F..d thermo's are bloody good, I have a set on my yellow HJ, and had a set on my vn headed 308 in the ute, Never had a problem with them yet, When I bought the tunna for my vn headed motor and lent the ute shell to a mate we left the fans in for him to use for his new motor, He is running a tough 308 and even when he was running the motor in it never went over 170F, I would definatly recommend them to anyone but be sure to hook them up right, Had a mate hook mine up and he had the wires round the wrong way so they were pushing forward instead of pulling the air through, All I had to do was trim the edge down a couple of mm to sit them closer to the radiator and close the gap and cut a round hole for the top hose into the shroud, Have also seen them mounted upside down and don't think they had to cut anything, Will take a couple of pics tomorrow and put them up.
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Why is common sense...Not?

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Cheers,
Chris.
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R.I.P Peter Brock, 26/02/45 - 08/09/06
R.I.P Steve Irwin, 22/02/62 - 04/09/06
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Why is common sense...Not

Thanks for sharing the info Krangle.

Do you mind if I add it to the efficiency page in Holdenpaedia?

It would be great if more folks made the changes. Less fuel, more go.

T

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Add it in if it helps.

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Many thanks Krangle.

Give me a day or so to have it done.

I'll credit your login against it too.

T

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T

My Shed

Holdenpaedia, they're the brakes Mate.

...and keep up the good work on the holdenpedia - its coming along like a treat.

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I must admit I've heard good things about the F$%d twin thermo fans but have not personally tried it. I had Davies Craig fans in the past and always ended up changing back to the Clutch fan. One reason is a car with air con needs to have a constant airflow throught the condensor which is usually mounted forward of the radiator. So if your motor is happy and the fan is not running then your poor old aircon is not getting the airflow it needs. While most setups have an existing booster fan, this fan is generally not large and only covers 1/3 of the total area of the condenser. I notice on my VT commie that as soon as I turn on the aircon the twin fans run constantly. It's true that your motor will rev freer without the clutch fan on the front of your water pump, but remember when the electric fan is running it's actually less efficient than a clutch fan. How so? Rotary energy from your engine is converted into electrical energy by the alternator, then that electrical energy is converted back into rotary energy by your thermal fan. You are converting energy twice to run your electric fan. As anybody knows everytime you convert energy you loose a percentage due to losses as nothing is 100% effficent. The advantage with an electric fan is control, you have better control over it because you turn it on and off when you like. At the end of the day I live with the little power loss a clutch fan brings because gee they keep your motor cool like nothing else, and are better than a straight bolt on job with no clutch.
Cheers
LMH

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It's times like that that T's Brake Fan setup would be ideal, cars stopped fans are on and condensor gets airflow, cars moving and the condensor gets airflow.

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Agreed LMH, aircon condensors need constant airflow or the aircon will not stay cold. All Holdens since the VN (and maybe earlier) have the computer set up to turn the fan(s) on when the aircon is turned on for this very reason.

The easiest way around this is to set up a second feed to the fans that is triggered by the aircon switch. Turn the aircon on and the fans come on too.

You are correct about loosing energy when converting it and doubly so when converting it twice, but overall, thermo type fans are more efficient as they only run when necessary and consume no power at all when they are not needed whereas clutch fans will consume some energy even when they are not needed.

That's my 2c worth anyway...

Cheers...Dave
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Cheers...Dave

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There is a critical rate of airflow through any radiator.
When less than the critical airflow is present, the car is under cooled.
When more than the critical airflow is present, the fan is wasting energy and the heat transfer is reduced.

Thermo fans have been working successfully on V6 Commodores for years.

Electric fans can be set to move the critical airflow through the radiator at all times optimising the amount of energy required to cool it.

There is also a critical rate for coolant flow. Too slow and cooling is ineffective. Too fast, power is lost as well as reduced heat transfer. That's why people use EWP. You have absolute control over the coolant flow rate at all times.

The standard problem with mechanical fans is that they undercool at idle, overcool under power and draw engine energy, as Dave indicated, when you absolutely don't want them there at all.

The closer a mechanical fan comes to moving the critical amount of air at idle, the more horsepower it will guzzle when the car is moving at speed.

The front of the engine is not the ideal place to mount a fan. An electric fan can be located anywhere.

Certainly the efficiency of energy transfer is a relevent factor, that's why I invoked [http://www.oldholden...|Fan Braking] . Any electrical inefficiency then works to advantage by slowing the car and reducing brake wear.

Also the energy transfer loss is minor by comparison to having a big 7 blader burning up the fan belt and bringing the engine to its knees as Krangle found out.

My suspicion is that there is something else wrong with Krangle's configuration. Fitting electric fans drops the engine's running temperature at speed because it loses the persistent heavy load created by the fan even though it has a fluid clutch.

T

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Now you're ready for the diff change that will give you a further economy benefit.

T

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Holdenpaedia, they're the brakes Mate.

The diff change is the next thing on the list.

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With thermo fans, the main thing is to make sure their external lip is pushed hard and flat against the radiator surface, if that isn't the case then a lot of the air will escape from the sides. I found throwing the twin 12" fans to the inside was more efficient and with a 16" on the outside I then had to build a mesh on the front to catch all the pedestrians I pull in off the footpath.

I was pleased when I made the conversion to thermos and the electric water pump too with how the car ran, it'd definitely be far more noticeable on a V8, good on you for having a go!

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I was looking under the bonnet of a late 90's V6 Camry yesterday and the fan on it was not electric but had some sort of pneumatic or hydraulic / hydrostatic motor! There was a pipe coming from somewhere and feeding it either with engine oil or aircon gas. At idle the fan was only ticking over and making a little breeze. Maybe if it's driven by aircon gas, the hotter the gas gets the faster the fan goes or something?

Krangle, did you take off the clutch fan because you removed the water pump entirely and now there is nowhere to attach the fan to, or just felt like having electric fans? :-P

Centrifugal pumps and fans are a cube-law device so if you double their speed they double double the torque needed to rotate them which means they need double double double(!) the power to drive them. They would really start to dig in at high revs for sure.
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Circlotron, I left the water pump in place with the impeller, but removed the fan belt and replaced with a shorter belt that just does crank pulley to alternator. I've got the fan belt in the boot just in case the EWP plays up.

I've wanted to go the thermo fan route for a while, but it took a while to find the time to fabricate an aluminium bracket to hold then fans that I was happy with. I always disliked the idea of mounting the fans by pushing those plastic pins through the radiator core's fins.

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