Electric fans and the Mechanical fan clutch (Aisin wins!!)

[Farmer42]

I think he means put a spacer on the front of the pulley to space the fan out.

No, I did mean between the water pump flange and the pulley wheel but didn't think about the alignment. Thinking about it, a longer clutch shaft would only move the fan out not the pulley wheel so wouldn't help you. Back to the drawing board.

 

[Farmer42]

The alternator and water pump are driven by the same belt. The only way I can see that you could overcome pulley alignment issues without messing with the alternator mounting is to use separate drive belts. That would, however need a second groove on your crank pulley. You could then space the water pump pulley out to align it with the 2nd crank groove. I suspect however that your crank pulley only has the single groove and is probably balanced so you wouldn't be able to add one. I presume that the smaller crank pulley is to accommodate a crank sensor for your ignition system so changing back to the oem is out of the question.

Too much faffing around whatever so it looks like you need both viscous and electric fans. The viscous will do the bulk of the work and the electric will cut in when the water temp gets too hot. Doesn't get over your slower water circulation though and that may result in higher block temperatures because the heat is not moved away quick enough. Not sure if that has any impact on oil degradation and quicker rubber seal wear due to the added heat.

 

[AliK]

I think he means put a spacer on the front of the pulley to space the fan out.

Ah yes, thanks John! I totally misinterpreted that. I’m planning on doing that

At the moment, the fan itself has some spacers between it and the fan clutch.

 

[AliK]

No, I did mean between the water pump flange and the pulley wheel but didn't think about the alignment. Thinking about it, a longer clutch shaft would only move the fan out not the pulley wheel so wouldn't help you. Back to the drawing board.

Sorry Paul - missed this! The longer shaft would have indeed helped!! Shame I didn’t spot that before I ordered the new Aisin one! Which, to my wife’s disgust of ANOTHER car part coming through the door, arrived today!!!

Currently being tested (shhhh, she’s busy having a shower)!!!

 

[Farmer42]

Mmmm that looks tasty Don't forget to baste it every 15 mins!!!

On a serious note, if you think a longer fan clutch shaft of the 280ZX clutch will help, I can send you a spare to try. You will probably need to source a fan to go with it as I don't think the S30 fan will fit the ZX clutch. The bigger ZX fan may help a little with the overheating as it does cool better but it won't overcome the possible issues from a slower circulation from your water pump.

When you have let the clutch in the oven cool a little, I would be interested on how freely it spins when colder. All the new ones i have ordered & tried have all ben really stiff and this makes the fan noisy.

 

[AliK]

Thanks Paul, really appreciate the offer and I may well take you up on that if my current plan doesn’t pan out!

Today I received a parcel (old water pumps) from the very kind Mr Kest and Mr Gaskins two 10” fans (pleased my wife no end)!

So the plan is to take the flange off a water pump and use it as a spacer to see if that gives me enough clearance. Then put the new fan clutch on and see if it works any better than my other one. The good thing about the water pump flange is that it has a centring lip for the fan.

Finally, the electric fans will go on. They are dated 2002 and the quality is far superior to my recent eBay rubbish purchase! They are also beautifully balanced with a clip to add ballast on one of the blades!

I just hope they see eye to eye with my PWM controller! I did build a dual MOSFET purely analogue driver circuit but they do get awfully hot, so PWM circuit connected to a temp sensor is the order of the day for a constantly speed variable electric fan!


ps. At 90c I was playing hot potato even with a dishcloth! The experiment ended there - I think I need to put it in situ before I can verify how well it works!!

 

[Rob Gaskin]

I've had clutch fans and they don't appear to be any different hot or cold. As soon as I start the car from cold they spin at full speed. Yes they may be faulty but I don't have any confidence in their design.

 

[AliK]

I've had clutch fans and they don't appear to be any different hot or cold. As soon as I start the car from cold they spin at full speed. Yes they may be faulty but I don't have any confidence in their design.

interesting Rob! I’ve had the opposite problem where they won’t engage but spin at their lowest rates! And I completely agree with your sentiment on not trusting them! That’s why I want a pusher solution to assist it when required!

I rally don’t like seeing the gauge going over half way (1/2 on mine is 88-92c depending on where you point the laser temp sensor).

 

[240L31]

Ali how about test the Aisin clutch first in your car As I said, I've been running it for years now with zero issues. Spins easily when cold but gradually stiffens up when it gets hot.

 

[AliK]

Ali how about test the Aisin clutch first in your car As I said, I've been running it for years now with zero issues. Spins easily when cold but gradually stiffens up when it gets hot.

Will do sir - good advice - just need to get to the garage these days

 

[Ian]

Just thought I'd add that puller fans work better than pusher, and the only reason to get a pusher over a puller is if you need the extra clearance or if you have a specific look for your engine bay I guess. Also if you want max efficiency with an electric puller fan it should be fitted to a proper shroud.

 

[peter_s]

Just thought I'd add that puller fans work better than pusher, and the only reason to get a pusher over a puller is if you need the extra clearance or if you have a specific look for your engine bay I guess. Also if you want max efficiency with an electric puller fan it should be fitted to a proper shroud.

Yeah, that seems to be a good answer.

I have about one inch clearance between my fan and the triggerwheel on the crank. Works fine, but I have the harder Kameari engine mounts.

I really like electric fans, the stock one makes so much noise! Running a SPAL, it's almost silent. My stock mechanical fan clutch was shot so it sounded like a like a Volvo 240 was starting up every time I started my car.

 

[Farmer42]

Ali. I would be interested in how your new Aisin clutch does when you try it. Does it spin fairly freely when cold and does it stiffen as it warms up? The reason for asking is that I have just bought a GMB one that says it is supposed to do just that but it doesn't in reality. In fact it is stiffer when cold than the one I have on the car so it makes even more of a whooshing noise. Probably just wasted 5o odd quid as it's not worth sending it back to RockAuto.

This is the 2nd new clutch I have bought with the same results. I'm just wondering if the viscose inside is affected by them sitting on a shelf for a while. I wouldn't have thought that they sell many so any stock may be there for some time in varying temperatures and conditions.

 

[Rob Gaskin]

I've had clutch fans and they don't appear to be any different hot or cold. As soon as I start the car from cold they spin at full speed. Yes they may be faulty but I don't have any confidence in their design.

Bump

 

[AliK]

Thanks for the bump Rob! I've been distracted with the club airbox this week. Not being one to do anything the easy way, I've been making my own backplate for it and it's starting to really shape up.

I also had read about pushers being less efficient, but I really do want to keep the mechanical fan as I like the "classic" look + they never completely fail. What I'm looking for is a little bit more cooling to supplement it (especially as the existing clutch rarely engages) and an insurance policy for that very hot day idling in traffic, fretting over the temps and popping the bonnet onto the latch while stuck on the motorway!! I'm sure most of you know exactly what I'm talking about

Paul, I will certainly let you know about the new clutch - probably something I will get round to this evening or tomorrow.

Rob G's two fans he kindly sold me are FANTASTIC compared to the pile of junk Aeroline 16" fan I bought off / returned to eBay. They are properly balanced and at full pelt, one of those pushes out more air than the 16" Aeroline, which incidentally was so out of balance that it bounced about the place. I will likely install both of the Rob fans. Definitely a write up coming up on that one especially as I plan to do a constantly variable PWM drive triggered by a second sensor in the thermostat housing, such that it gently starts spinning around 75c and builds to full power at 95c.

Will let you know how the Aisin goes at the weekend.

 

[Rob Gaskin]

When I did trackdays I ended up just having an electric fan and it was a pusher. I was never really bothered about overheating except for the brakes.

 

[Joey Bratten]

Just to Chuck my two cents in here, when we are hot lapping cars drifting, the stock viscous fans always win hands down, albeit the Datsun stuff might not be as good as the “newer” Nissan Silvia stuff. When we do use electric fans, I never bother with anything such a mishi or spal etc and just get hold of oem diesel fans, jaguar, Ford and some nissans are really good. Cheap on eBay and way way better than the aforementioned off the shelf stuff.

Has anyone ever tried using a Nissan Silvia fan clutch? I have one here to measure up if that would help, you can then get a fan blade from gktech which increases their pull by 60%!

 

[AliK]

Thanks Joey, that is very interesting indeed! I “think” I recall seeing that the same fan clutch goes into many different Nissan models and the Silvia was one of them, I could be wrong - but a bit of Rockauto-ing would soon prove it.

So, my 30 mins job of swapping fan clutches turned into 1.5 hours - must be getting slow in my old age! I had forgotten how tight the access to the bolts was but also the flange on the Aisin is 2mm less deep than the old one, which made the fan blades juuust touch the bolts on the ATi damper - so I had to re-install the fan again with more spacer washers added. In effect I did the job twice !

In short, the Aisin is in and appears to centre the fan FAR better than my last one, showing zero discernible off centre wobble. Being kind to my neighbours at 22:00, I didn’t warm the car up but at a fast idle, it’s way more engaged than the one I took off. I can’t stop it with my fingers - the other one took no effort at all to stop, so that bodes well.

When the engine bay started to smell of toffee, I realised that I had spilled on the exhaust manifold my “poorly balanced on the cam cover sugary cup of tea” !

I’ll warm the car up properly tomorrow morning and report back.

 

[Rob Gaskin]

So Ali when it was cold it spun and didn't slip? When is it supposed to slip then?

 

[AliK]

So Ali when it was cold it spun and didn't slip? When is it supposed to slip then?

yes exactly! But I look at it in one of two ways:

1. if it doesn’t slip as much as it should when cold, I’m still getting better cooling especially with half sized crank pulley so it’s probably the same as if it did slip on a full sized crank pulley - in terms of cooling - did that make any sense? Also the thermostat can then take care of the cooling rather than constantly being maxed out.

2. I don’t know how must resistance it “should” give when slipping as both my other ones only slip and I can’t be sure they didn’t over-slip. So I need to get it to temp to see what the difference is.