1145 replies to this topic

[Graeme Lambert]

Can't remember the thread but sure winstar said spacing the diffuser is actually counter productive to cooling. I'll try and find it.

 

Damn. lol

[Winstar]

Can't remember the thread but sure winstar said spacing the diffuser is actually counter productive to cooling. I'll try and find it.

For a standard car yes but you have to reverse the cooling flow to make the coupe back work. Yes you could space the diffuser if you're not trying to maximise the downforce from it, which you won't if all you're using it a tat

[Dave E]

Wrong again carry on.....

[Graeme Lambert]

Can't remember the thread but sure winstar said spacing the diffuser is actually counter productive to cooling. I'll try and find it.

For a standard car yes but you have to reverse the cooling flow to make the coupe back work. Yes you could space the diffuser if you're not trying to maximise the downforce from it, which you won't if all you're using it a tat

So spacing diffuser is a good idea in my case then? (As I don't want to cut the rear of the clam). Should I be adding another naca duct or not then as I'm planning on using roof scoop? Also any thoughts on coupe back but no big gay wing? Will it be ok without or is there issues with lift this way?

[fezzasus]

I would suggest taking a simple approach of adding up all the area of the inlets and outlets before you go ahead an add extra items. For example, I would say you are strongly biased towards lots of air going in rather than exiting, so adding more inlets in the form of NACA ducts might not help. Also remember the air exiting will be hotter and therefore less dense, so you should bias towards more exit holes. 

 

I actually don't think you've lost much total vent area by moving to a coupe rear, however you will have lost an area of low pressure which helps pull hot air out. The logical addition would be an exit at the rear as it's another area of low pressure, hence the spaced diffuser. Adding more NACA ducts may effectively saturate the venting capacity of the spaced diffuser, preventing the air from the side intakes from being pulled over the engine.

 

Given that this is mainly a road based car with some track time planned, I would instrument the engine and pay attention to temperatures, it may be the case that you have to run shorter track sessions during peak summer temperatures.

[Winstar]

I would suggest taking a simple approach of adding up all the area of the inlets and outlets before you go ahead an add extra items. For example, I would say you are strongly biased towards lots of air going in rather than exiting, so adding more inlets in the form of NACA ducts might not help. Also remember the air exiting will be hotter and therefore less dense, so you should bias towards more exit holes.    I actually don't think you've lost much total vent area by moving to a coupe rear, however you will have lost an area of low pressure which helps pull hot air out. The logical addition would be an exit at the rear as it's another area of low pressure, hence the spaced diffuser. Adding more NACA ducts may effectively saturate the venting capacity of the spaced diffuser, preventing the air from the side intakes from being pulled over the engine.   Given that this is mainly a road based car with some track time planned, I would instrument the engine and pay attention to temperatures, it may be the case that you have to run shorter track sessions during peak summer temperatures.

The measuring area approach won't really work with aero as it's the flows will be dependent in the pressures at the openings which is very unpredictable without modelling/measurement, but no I wouldn't add another NACA duct with the coupe back as the front scoop should be sufficient. Although in a lot of respects, as covered in the oil cooler thread, cooling around an engine is pissing into the wind really. If you want to improve the cooling of vehicle you need to concentrate on effectively cooling the fluids with appropriate radiators that get sufficient cold air flow.

[fezzasus]

I was suggesting measuring area as a simplistic approach, because if you take extremes (say 3 NACA ducts, two turbo intakes but only the exhaust vent under the number plate) you're in trouble.

 

Do you really see the radiator as the limiting factor in respect to engine cooling? Perhaps there's an advantage to running the Joe/FLD style three section bonnet.

[techieboy]

Do you really see the radiator as the limiting factor in respect to engine cooling? Perhaps there's an advantage to running the JoeTechie/FLD style three section bonnet.

EFA.

[Nev]

I for one have tried to allow my engine as much fresh air as possible and have absolutely no cooling/overheating issues of the engine coolant or the IATs/IAT coolant (providing I'm not sat in traffic). I do have the advantage of the Pro-Alloy rad and pre-rad for the CC system BTW.

All I did was:

1. remove the wheel arches
2. remove the floorpans
3. vent the rear of the engine bay into the boot and thence to the rear clam cutouts.

I know these 3 steps are impractical in an everyday car (with the exception of step 2), but it does work.

When I see talk of things like adding a single naca/venturi slit to "fix" overheating problems I think people really need to understand just how much heat their engine makes, cos it's a LOT and if you genuinely want to improve things you really need to take some bigger steps IMHO.

Edited by Nev, 02 February 2014 - 05:10 PM.

[GeorgeBC]

No offence Nev but i don't think anyone has heat issues from road driving. If your VX saw a 20min track session im sure something in your engine bay would be effected as its a complete rebuild from standard and has only been pushed for short dyno runs.

[Nev]

No offence Nev but i don't think anyone has heat issues from road driving. If your VX saw a 20min track session im sure something in your engine bay would be effected as its a complete rebuild from standard and has only been pushed for short dyno runs.

I understand your point, using high revs and not moving too fast on a track will magnify any problem a huge amount for sure. However, believe me when I say I've done some constant/sustained (perhaps 1.5 to 2 mins (which is way more than most tracks (except the Mulsane straight )) at very high heat/power output levels and thankfully not had any problems. Ram effect (from my testing experience) of high speed helps force the rads to work well, and I am sure on track where you are revving engines hard and not necessarily moving fast, this ram effect will be lower. Hence why I think venting air around and through your engine bay is an easy and cheap way to significantly help. BTW, I have an accurate IAT temp guage on my dash, and obviously also have the OEM engine temps to monitor the engine coolant temps. It's unusual for me to see > 15 degrees ambient IATs (and very rare to see > 25 above ambient IAT), all providing the car is moving at a sensible speed for the revs. I am only trying to offer a possible solution for someone like Graham who sounds like he might be tracking the car more than road driving, so could possibly start stripping away stuff to help ventilation.

Edited by Nev, 02 February 2014 - 06:41 PM.

[Darcini]

Do the vanes on the tubby ears have any positive effect on the airflow going in, or are they more for cosmetics?

[GeorgeBC]

Its not just the length of any straight that effects the temps Nev as it constant high revs. The few seconds when braking aren't enough for temps to recover so by the time you get back onto a straight your temps go higher again. This is why your car will get a lot hotter lapping hard than on a 1.5 min drag run.

 

What coolant temps do you see? 

[Nev]

Its not just the length of any straight that effects the temps Nev as it constant high revs. The few seconds when braking aren't enough for temps to recover so by the time you get back onto a straight your temps go higher again.

Umm, that's what I said in paragraph 2, sentence 1. I agree with you.  

What coolant temps do you see?

When moving, I never see over 84 degrees C. When driving hard and then coming to a standstill or when just trickling along in traffic for circa 10 mins or more I will see 105 degrees or whatever it is until the fans kick in. Overall, I am convinced that opening up as much as you can around the engine bay helps with cooling. I don't reckon the ears do a great deal, even though they do look like they should (the N/S ear on my car does help in my case, but only as my airbox is no longer there in the OEM place and there is a void there currently). I used a camera and various wool strands around my engine bay to observe airflow BTW.

Edited by Nev, 02 February 2014 - 08:31 PM.

[Graeme Lambert]

 

Do you really see the radiator as the limiting factor in respect to engine cooling? Perhaps there's an advantage to running the JoeTechie/FLD style three section bonnet.

EFA.

 

 

Does that mean you're actually going to fit it Matt?

 

Do the vanes on the tubby ears have any positive effect on the airflow going in, or are they more for cosmetics?

 

Interesting question? Am I right in thinking the Loti just use a simple mesh? I know if you buy some ears from Jonnyboy they have a meash rather than plastic vanes.

[Graeme Lambert]

Had something of a Pro Alloy weekend.

 

Thanks to Joe for dropping this lot off on Saturday

 

Gearbox breather kit

 

Chargecooler rad

 

 

Not PA, but part of the 'Batman chargecooler kit'

 

Header tank

 

 

And picked this little thing up from DuncanVXR (who was holding it for me as I bought it from Noplex)

 

 

60L Pro Alloy fuel tank

 

 

 

And big thanks to both IanRM (for transporting it to Dunstable for me to pick up) and JG for sorting the group buy, now got another TAT short round diffuser.

 

 

 

 

The garage is now properly full. Not quite sure what I'd have done with all this kit had I still had a car in there, as there just wouldn't have been any room for anything.

 

Think that means it's about time I cracked on with actually doing something that involves fitting or removing parts rather than just gathering them...  

 

G

 

 

[Dave E]

As your concerned about cooling I would have a word with Matt about only fitting one of the fans. Never had a problem with coolant temps until I had the CC fitted with twin fans, although it isn't a major problem they are noticeably heighter, high enough in fact for me to go through all the hassle of removing the front clam to get shot of one. I was warned at the time this might happen but unfortunately decided to go with the twin setup. True, cooling in traffic will suffer, although mine survived fine with only one before, but on track it's a big obstacle for airflow.

[Graeme Lambert]

As your concerned about cooling I would have a word with Matt about only fitting one of the fans. Never had a problem with coolant temps until I had the CC fitted with twin fans, although it isn't a major problem they are noticeably heighter, high enough in fact for me to go through all the hassle of removing the front clam to get shot of one. I was warned at the time this might happen but unfortunately decided to go with the twin setup. True, cooling in traffic will suffer, although mine survived fine with only one before, but on track it's a big obstacle for airflow.

Interesting point Dave, will have a think about that. To be fair I'm not overly concerned about cooling, I'm just trying to second guess a few things and desperately trying to avoid cutting my clam at the rear.

[Graeme Lambert]

So this conundrum has got me ogling every rear end (of the cars) I pass on my way to and from work looking for a solution. Think I'm getting obsessed

[fezzasus]

Well, look at the Exige for ideas. The impact of the coupe section is duplicated there:

 

Differences are more cooling over the engine and a greater angle, meaning the base will probably still be an area of low pressure. And more vents around the diffuser section

 

 

Typical modification for hotter climates is removing the grille/number plate support completely for extra cooling.

 

 

So my vote is still for a spaced diffuser. You could get clever and put some rivnuts into an aluminium support, put springs on the bolts between the diffuser and support so you have a height adjustable diffuser which you can lower for the track.

Edited by fezzasus, 04 February 2014 - 08:11 AM.