4.2 V8 Coupe Quattro

[Henkjan]

Could (also) be airflow, look also to possible restrictions in the flow of warm air

[sjw185]

Wow what a coupe
Are you running aftermarket fan on original fan wiring with staged thermostat?
Just a thought you are maybe losing CFM with series resistor in place?
Might help running fan controller or testing with direct switch to see how it performs.


Cheers
Steve

[Lago Blue]

Can this fellow forum member provide a V6 rad?

https://www.s2forum.com/forum/member...s2-200?t=70316

[ajax1976]

Size & volume isn't really important - efficiency is.
If I was you I would try and fit an OEM part, these will be high quality and have efficient cores - I'd be surprised if the OE V6 unit wouldn't do a better job than that China-Yank special you got there.

If an OEM unit isn't an option due to plumbing issues, get a proper fabricator to make you something to suit using a high quality, high efficiency UK made core. This won't be the cheapest option but it will work. Buy cheap, buy twice. Just my 2c

Plenty of folk have proved the V6 one is not up to the job so not even attempting that one, Any suggestions of UK custom fabricators?

Could (also) be airflow, look also to possible restrictions in the flow of warm air

I suspect this could be the case, been reading about adding functional bonnet vents to help get rid of some of the hot air from out from under the bonnet, if done right they can look nice too

Wow what a coupe
Are you running aftermarket fan on original fan wiring with staged thermostat?
Just a thought you are maybe losing CFM with series resistor in place?
Might help running fan controller or testing with direct switch to see how it performs.


Cheers
Steve

Thanks

Yes, Aftermarket fan with original two speed wiring set up, both speeds function as they should. I do have the option of running the fan through the Emerald ecu but chose the oem way as it was easier for me to hook up. After a drive, at idle the fan manages to hold it at 96 degrees but certainly doesn't bring it down, more just stops it going up anymore, driving on a nice crisp autumn day doesn't even bring it down once the temps up.
I think I'm going down the custom radiator route, this should allow me to run a larger fan or two fans and possibly even a shroud if I can squeeze it in and I'll be able to get more air to it instead of hiding half of it behind the solid part of the bumper.

Can this fellow forum member provide a V6 rad?

https://www.s2forum.com/forum/member...s2-200?t=70316

Thanks but not going down the V6 one route, I played about with the cars original one, tricky to plumb and haven't read of anyone saying it's up to the job.

[Error404]

We use BMR at work.
i have recently seen some excellent work done by JC Weldfab in Northampton. Then there is the usual suspects, Proalloy, Alirad etc etc etc

[twoqu]

Unless the donor vehicle was renowned for overheating it would seem prudent to follow its setup.
I appreciate that space is an issue but perhaps if you get an idea of the dimensions of the V8 models, say the A8 and perhaps the older C4 S6 V8 Plus that might form the basis of a bespoke radiator. Essentially you need headlight to headlight core! I was shocked by the depth of this rad which I assume is down to it being two pass. Not sure what the theoretical advantage of that is compared to the OE design (single pass?). So if the bespoke was of thinner and wider dimensions that might assist the packaging. If you remove the snub mount you should also be able to get deeper. Certaintly OE rads are not very thick.
Then its all a matter of best practice. Ensuring as much air goes through the core rather than around it. Certaintly shrouds improve effeciently, drawing air from all the core. Perhaps two fans and flaps. Basically as OE as possible.
Cant see the make and model of fan but certain fans are not reversible and are either pusher or puller. There is even debate over whether straight blades are superior to S blades in performance terms rather than being quieter.

[Error404]

[twoqu]

Looks like the S6 Plus had a core of 632X412X34mm vs the V6 at 598X408X34mm so thats not a mammoth difference! The S6 Plus was rated at 326PS and would have had a aircon condenser fitted in front of the rad . They did have more grills at the front mind. They probably also used the large viscous fan with a smaller electric fan.
So on paper at least it would seen that a core size close to that would be adequate.
I wonder if this is more an issue of circulation where this dual pass is causing a restriction in comparsion to the single pass rad.

[twoqu]

It does seem that the dual pass causes a restriction in coolant flow and some people suggest water pump upgrades or switching to electric pumps. I guess if you have the opportunity to evaluate the cooling system as a whole it might have some benefits although a lot of it seems to come down to packaging.
I guess you are aware that some models came with a nice twin 280mm fan/shroud package (diesels and aircon). The one pictured seems to show relatively low profile motors unlike the older ones. It would be difficult to improve on that set up if it could physically fit. It might be possible to upgrade the fans.
Surface area and airflow seem to be the most relevant factors so a V6 dimensioned rad with a superior core with end tanks to suit your plumbing incorporating all the factory ducting/seals and possibily the fan/shroud assemby pictured might be adequate. I appreciate its something you only want to do once but perhaps this is one area where bigger/thicker is not necessarily better.

[twoqu]

Actually that pic might not be the correct one for the depth of the rad !
The correct shroud would be 8A0121207A. If you look at some of the images you will see that the fans are suitated toward the top of the radiator. Whether that helps you or not I can't answer. I think that pic might be a shroud that begins 893. Obviously you would need the correct shroud for the radiator depth.

[twoqu]

Strangely the S6 Plus rad looks like its a single pass, whilst the A8 rads must be dual pass if the inlet and outlet are on the same side, sort of overlooked that! If it was possible to merge the pipes to the other side that would free up some space behind the rad. The S6 rad has the top hose on the N/S and the bottom hose on the O/S.

[ajax1976]

Thanks for all the input guys, really appreciate your time and help!!

I took the bumper off today to get some rough measurements and to try and get some ideas on how to plumb it in. If I go maximum width I'll have to go single pass, relatively easy to do by turning bottom hose off engine 180 degrees. I can possibly gain some more depth if I modify the cross member to let it sit close to the same level as the oil cooler.



At the above dimensions I can use the same width core as the Afco radiator, 5.5cm core(7.5 tanks) although there'll be no chance of fitting a shroud, even dropping to a smaller core width I think a shroud will be out of the question but it will help with fitting a second fan.

[ajax1976]

You'll need to excuse my ignorance on other models but could I replace my cross member,



With one of these?

[twoqu]

Surely the limiting factor is going to be the lock carrier brace.
Whats the dimension of the fan from the radiator? Just trying to get an idea of the amount of space available.

[ajax1976]

Surely the limiting factor is going to be the lock carrier brace.
Whats the dimension of the fan from the radiator? Just trying to get an idea of the amount of space available.

Lock carrier brace? The vertical bar with the safety catch for the bonnet? I've already spaced that out at the bottom mount to move it as far forward as possible so I could get the radiator forward at the bottom.

The fan sits directly on the radiator at the moment with the centre of the fan(widest part) sitting in a void of the aux belt route. Most of the cars I've seen converted to V8 run push fans on the front, I'll probably keep my existing pulling fan in a similar location on the RHS of the rad but might have to run a push fan on the front LHS due to the belt route.

Hopefully these pics will give you an idea of space available,