The V8 Owners Forum -

With the cooling, you might find that you have insufficient exits for the air from under the bonnet, so bigger rad / better fan won't actually help.

Chris.

Tom

Silly question
Is your fan blowing the correct way?
I have heard of a case where on idle - fine
At speed fine - at 20 mph overheated

Fan was blowing forward and nutralising the natural airflow

Easy to test - stand in from of the hot car with the fan running and if it blisters your legs fan is running the wrong way!

And a guide to radiators is 1/3 rad size on inlet size and at least 2/3 of rad clear at rear - around engine/ header tanks etc

Ian

I agree with Mike. You should be seeing at least 20mpg I reckon.
I got that with the 4.6 auto on the road as an average ?

Quick replies!

Ian & Chris, the fan is correct- I even turned the blades round and reversed polarity to get the best push effect I could and it works ok, though I'm never sure that rad fans work as well pushing than pulling. Once I get the ducting/shielding done (just ordered a sheet of 1mm ally) it should cool better on the road, though might not make any difference whilst stationary. The mx5 "mouth" is approx 1/3 the size of the fan as already looked at that and will hopefully work ok!

Mike & Pel, it's not definite yet as my speedo isn't calibrated and I guessed the distance I drove as best could, along with the fuel I used, may be better but shouldn't imagine it's a long way out. I'd have thought 30mpg would be well optimistic- I was reconing 20mpg would be possible with fairly careful driving?
The thing is- the fuel system doesn't leak- and the AFR gauge I have has been telling me its pretty much spot on all the time- I changed the rods again and am pretty much always in the 13/14's, if it were drinking way too much fuel surely it would be running really rich and showing much higher readings? The driving was all on very bendy roads so a lot of slowing and pulling away again- but not to a racey extent!

TC my rovers water temp is about 85, i thought this a standard temp for the rover lump ??. And what great weather to drive the car around in. As for fuel used, i think my 3.9 uses less than the 3.5 that was in it, so i wouldnt of thought yours would be a thirsty lump?? rich

Rich- I want to keep the temp as low as possible as I have the 4.0 block, which as you know is more prone to liner slip than the others. If I can keep the temperature down it should prevent the ally block expanding too much and releasing some grip on the liners.

IIRC a lot of the liner problems began when Land Rover had to use hotter 'stats to keep emissions down in the P38 RR's, hence more expansion etc. As my car is too old for emission testing I'm not fussed about a few more CO2's if I can prevent any liner trouble!

i use the pink stuff from halfords its suppose to be good for alloy blocks, ive also read somewhere about something called thermocool. Will have a search and put it up rich

AH! Yes- I thought about using wetterwater or whatever it's called but completely forgot! Anyone know how much difference it makes and if it is likely to start leaking everywhere when I put it in? Doesn't it basically get rid of the surface tension of water so it conducts heat better? If so- then the watter in effect becomes thinner and will find anywhere to leak from too

The stuff i read about is called Zirgo ultracool, suppose to lower temp by 30%, rich

Hi Tom
Just a thought, have you done a plug chop? I know with current high ethanol fuels you can't tell as much as with older fuels, but it will show if you are rich or lean. It is a good double check that you are not being mislead by your AFR gauge?
The reason I ask is in one of your other posts you said it was running a very hot exhaust and had melted one of your exhaust mounts, add to that its is using quite alot of fuel and you have issues with fuel pressure and did have an apparent problem with flooding then. . .
It could be you are running very rich but have an airleak in the exhaust, result high CO and HC out the cylinders but mixing with air in the exhaust and continues burning, result AFR meter thinks mixture is ok but your exhaust is hot and it drinks like a Belgian monk.
Best regards
Mike

bones wrote:The stuff i read about is called Zirgo ultracool, suppose to lower temp by 30%, rich

In my opinion, those water-wetter things are snake oil. Complete waste of money.

Chris.

Plug chop? If there was a hole in the exhaust wouldn't it blow rather than suck?

Also with the exhaust I was kinda expecting problems with that mount as it was too close to the pipe and the bracket was short so conducts the heat easily. It seems to run nicely but not sure how I would really tell!

The only way I suppose is to get some more miles on the clock then take it to the rollers??

Hi Tom
Plug chop:- accelerate up a hill in so you use 3rd gear from about 2.5k to about 5.5k wide open throttle over a period of atlease 15 seconds. As you hit 5.5k kill the ignition and put your foot on the clutch and coast to a halt. Pull out a couple of plugs and have a look at what colour they are, referre to you trusty haynes manual for the supercharger 4 litre rover engined MX5 for a handy photochart of what your plugs tell you! Actually any havnes manual (apart from the babies one) will tell you as they all have the same chart.
A hole in the exhaust will both suck and blow as the thing has high and low pressure pulses moving up and down inside it.
Best regards
Mike

what plugs are you using Tom?

I reckon NGK B8ecs might be ok for your engine.

They are either B8 or B7ECS, cant remember!

Mike- I think I'd need a pretty long hill to use WOT for 15 seconds in 3rd gear but will hunt around

This is why my exhaust mount melted- I know I know, stupid place to put it so close and I knew it would break so not sure why I put it there! Making a bar to move a pair of bobbins away from the pipes now either side of the original.



...and the brackets I just made to remedy the existing stupid exhaust mount