under bonnet temperatures

[jesfirth]

I am interested in reducing under bonnet temperatures and also improving downforce on the front of the car. The usual exhaust wrap or cermaic coating or exhaust etc will be done anyway so I am interested in more innovative solutions

the later cars especially tuscans effectively have the air through the rad venting over the bonnet rather than under it. has anyone done a similar thing on a griff and did it work form a temperature perspective and does it increase front downforce or did it just screw up the air circulation in the engine bay.

Jes

[5.0ltr]

Dunno about ceramics and air flow but some have gone down the vented bonnet (suppplied by Fibreon) route, including a Griff owner in Australia.

[Slade Alive]

Been an advocate of exhaust wrap for years, since the bike pipe is covered from end to end in the stuff. Works on the bike in terms of keeping heat in and not burning my leg, and no issues with stainless steel cracking, as has been suggested many a time on bike related forums.

Oh not so on the beast though. Recently took the wrap off the manifolds to sort a long term blow. Was I surprised to see the extent of the cracking. Right around a couple of tubes on both banks, and worse still, hairline cracking along the lengths of some header tubes. A right bloody mess frankly. I can only conclude mild steel reacts differently to constant heat cycling than S/S as I can't see any other reason why the manifolds have snapped and cracked in such a devastating manner. I won't be wrapping them again. Your experience may be different.

[TVR Beaver]

Slade Alive said:

Been an advocate of exhaust wrap for years, since the bike pipe is covered from end to end in the stuff. Works on the bike in terms of keeping heat in and not burning my leg, and no issues with stainless steel cracking, as has been suggested many a time on bike related forums.

Oh not so on the beast though. Recently took the wrap off the manifolds to sort a long term blow. Was I surprised to see the extent of the cracking. Right around a couple of tubes on both banks, and worse still, hairline cracking along the lengths of some header tubes. A right bloody mess frankly. I can only conclude mild steel reacts differently to constant heat cycling than S/S as I can't see any other reason why the manifolds have snapped and cracked in such a devastating manner. I won't be wrapping them again. Your experience may be different.

Wow... Was thinking of putting some wrap on the pre-cat section as removing the pre-cats has given the Ting-Ting sort of sound... But reading this sounds like it's a non-starter... Has it cracked the pre-cat sections or just the header pipes?... Any pic's?? :eek

[jesfirth]

no i havent got a splitter but could easily fit one- may well do so in fact. I am interested to hear about the pipes splitting beneath the exhaust wrap. I wrapped the manifolds on my 400se and cerb previously and never had any problems with them. does anyone know if this is a common problem with wrap?

[Gnasher]

Hi Jes,

I'm just attending to the engine cooling on my pre cat, which came to a head when 1 of the fans failed on the way to Classic Le Mans last year.

I have had the rad remade with an extra row of cores to improve cooling. When they took the old one to bits it was amazing how much crap there was in there, some of the cores were blocked. My car is 19 years old & the rad was original. When I took it off the car I gave it a good flushing & was fooled by the fact that the water came out clean, so be warned.

I've got a spoiler to fit & have also got a 'big bore' 82 degree thermostat from Clever Trevor, the hole when the thermostat opens is about 35mm diameter, the original was about 27mm.

All that, plus sealing the gap between the rad & the body with foam to make sure that the air goes through the rad & not round it should help.

Fingers crossed.

Regards
SteveD

PS Will you be out in the Griff this year?

[Bluebottle]

Slade Alive said:

Been an advocate of exhaust wrap for years, since the bike pipe is covered from end to end in the stuff. Works on the bike in terms of keeping heat in and not burning my leg, and no issues with stainless steel cracking, as has been suggested many a time on bike related forums.

Oh not so on the beast though. Recently took the wrap off the manifolds to sort a long term blow. Was I surprised to see the extent of the cracking. Right around a couple of tubes on both banks, and worse still, hairline cracking along the lengths of some header tubes. A right bloody mess frankly. I can only conclude mild steel reacts differently to constant heat cycling than S/S as I can't see any other reason why the manifolds have snapped and cracked in such a devastating manner. I won't be wrapping them again. Your experience may be different.

Iv'e now cracked two sets of headers wrapping them, and my last set did the same as yours...I wont be doing ever again! The current set will be ceramic coated when i can afford it

ETA to the op's question, i have raised the bonnet catch to give 1/2 to 1 inch air gap and also chain drilled the rear lip of the bonnet...this really works well when moving, even at slow speeds. It has also helps stabalise the car at high speeds by reducing the air pressure under the bonnet.

But, i havent found a cure for the ambient temps rising when stationary other than popping the bonnet up.

Edited by Bluebottle on Friday 20th May 10:31

[budd]

jesfirth said:

I am interested in reducing under bonnet temperatures and also improving downforce on the front of the car. The usual exhaust wrap or cermaic coating or exhaust etc will be done anyway so I am interested in more innovative solutions

the later cars especially tuscans effectively have the air through the rad venting over the bonnet rather than under it. has anyone done a similar thing on a griff and did it work form a temperature perspective and does it increase front downforce or did it just screw up the air circulation in the engine bay.

Jes

Why are you looking at cooling / underbonnet temps? do you have a specific problem or is it just a general interst ?
I know from experiance that cooling and underbonnet temps are a problem on Griffs and indeed all TVRs, I guess the GRP acts like an insulator.
However I only found it a serious issue in heavy traffic or very slow stop start driving, on the move it wasn't a problem.
T combat the problem I overalled the whole cooling system, firstly I had the rad recored with a thicker core (the original core was pretty clogged at the bottom so I'd recommend a rad change or at least a serous flush as first on the list the aid cooling, then I wrapped the manifolds/downpie etc, (I too suffered some cracking issues so ceramic coating may be the better option if you don't have SS welding gear), I then fitted a manual overide to the fans so at the first wiff of slowing traffic or congestion I could get the fans on good and early rather than waiting for the water temp to rise and trigger them.
Despite been only minor mods the above seemed to manage the heat much more effectively than the std set up, although replacing the clogged rad was probably the main factor here, but I feel the uprated core I fitted was worthwhile for the extra capacity it proved, the std cooling system is marginal at best so any improvement as got to be a good thing.
Another thing I had planned ( but never got round to fitting) was an oil cooler which should also help the engine temps.
With regards to airflow I think the Griff already does try to pull some rad flow over the bonnet it's not as develoed as the Tuscan and therefore not as effective, I've seen V shaped IC / rad assemblies on turbo race cars that are very effctive but it does mean chopping the bonnet and nose about which isn't a problem on your average Jap car but maybe isn't such a good idea on a Griff.
Also remember if considering any non std front spoiler/splitter to look at the aero as a whole rather than focusing solely on the front, any increase in front downforce could have an adverse effect on the balance of the car, so the aero really needs to be considered as a 'package'.
Although I sure a well designed aero package would be very effective, I'm not sure how long the front would acually last on the cart tracks we have for roads judging by the scrapes and gouges on the underside of my nose cone !!!l
Plus i think the Griff is such a pretty car it would be very difficult to add aero without compromising these good looks, OK for a out and out race/track car but for a road car the I'd leave well alone.

[LordGrover]

Bluebottle said:

... chain drilled the rear lip of the bonnet...this really works well when moving, even at slow speeds. It has also helps stabalise the car at high speeds by reducing the air pressure under the bonnet.

It's a lot of holes! Did you fit anything to increase rigidity?

[steve-V8s]

Hi Jes

I started to take an interest in under bonnet temperatures when I realised there was a strong correlation between inlet air temperature, engine temperture and getting Hill climb trophies. The thin paint on and bake in the oven manifold coating and removing the pre cats helps a bit but a proper ceramic coating is really the way to go. I started by reasoning that keeping the engine itself solidly at an optimum 82c was a good starting point so I fitted an Ally Rad which allows the cooling system to get rid of heat much more quickly. That and a proper splitter means the fans rarely come on the move, however on the move is not really the problem.

When stationary with the engine running (queuing for the start or driving in traffic for example) the fans cut in and out and maintain the coolant temperature but due to heat soak the general under bonnet temperature climbs and once it has got hot it takes a fair time to cool down again. I tried a vented bonnet which seems to help prevent the temperature continuing to rise after you have stopped and I guess that is because heat off the manifolds can vent but it didn’t really help apart from that. The best solution I have found is to gently run one or both of the fans all the time while stationary after the engine is around the correct temperature, it seems to keep the air under the bonnet moving and keeps things at more acceptable level. If the fans operate normally the heat soak builds up during the off cycle but doesn’t seem to drop a lot when they come on.

[dnb]

I have been taking an interest in this issue too.

My conclusions are much the same as Steve's - on the move with an 82 degree stat and an alloy rad, the cooling works well. When stood in the queue for an autotest, things can get hot quickly.

I wondered if a pair of carefully shaped heat shields sat above each exhaust manifold could shield the inlet from radiated heat while at the same time they could be shaped to act as ducting to force air from the fans over the manifolds.

[Bluebottle]

LordGrover said:

It's a lot of holes! Did you fit anything to increase rigidity?

Bonnet is no weaker than before

[Guillotine]

SC power splitter will...

reduce temps
improve braking
improve mid corner wash out

see here Jes http://www.tvrmonster.com/aerosplitters.html

probably the best mod I ever did to mine (other than safety)
Andy

All IMHO

[jesfirth]

gents - thanks for all the input-much appreciated. I should have been more specific. The car doesnt overheat it runs rock steady at 90 -or did before the engine was rebuilt - i just got it back last night so just have to drop it back in now. I am seeking to keep the engine bay cool on the move but also especially in the queue at sprints as Steve v8s mentioned.

Steve D hi - i plan to be at my first sprint this year at abingdon in a couple of weeks time - be interesting to see how it goes with its new carbon trumpets- will you be there?.

Andy thanks i like the look of the aero and when funds permit i will give you a call. does the extra front downforce need to be counteracted by more at the rear to keep it balanced - bear in mind i am not allowed a rear wing or anything dramatic like your monster

thanks

Jes

[spend]

Revving the bks rather than idling when standing pumps lots of cooler water round + cooling air through the induction. What you are asking for is far different to the normal "cooling" gripes.

[steve-V8s]

I am not at Abbingdon, if that was directed at me.
Splitters are also available from DIY/Builders merchants, mine came from Wicks for about a tenner. I fitted it initially as an attempt at reducing drag (by reducing the amount of air that has to find its way round all the lumpy bits under the car. It did however make the front more stable at speed particularly if you need to change direction at 100mph, the finish line at Gurston for example. I did however need to balance things up with a spoiler on the boot lip. You are allowed an opaque spoiler provided it has no holes, is less than half the height of the rear window and sits within the confines of the bodywork. I got a spare boot lid and grafted on the spoiler from a popular German car which does the job nicely. It is however far too heavy and I made but have yet to fit a GRP copy.

This pic is a bit old now but the splitter is the same bar being 20mm lower.

[Gnasher]

Hi Jes,

No I'm not at Abingdon, so will probably see you at Hethel? Hope your rebuilt engine's oil pressure survives this year.

My next outing is at Prescott on Saturday, you could tell just by reading the weather forecast, dry for weeks & now they're talking about showers.

Regards
SteveD

[jesfirth]

confusion reigns - 2 steves.

steve v8s thanks. the front splitter looks good - will look at that - my problem is that the tvrcc regs dont allow rear spoilers if they werent originally fitted and as the griffs never had them im not allowed one - but thats life.

Steve D - hope it stays dry for you - hope to be at hethel and perhaps one or 2 others but i will have to see how it all goes

cheers

jes

[steve-V8s]

Ah, I see I was thinking of the ModProd regs.
There is an easy mod you can do to help the rear areo. Bring the exhaust pipes straight back from the rear box. TVR made the underside of the boot nicely diffuser shaped and then plonked a couple of bent pipes in the way. Saves a bit of weight as well because you need less pipe.

[DarkMatter]

steve-V8s said:

Bring the exhaust pipes straight back from the rear box.

If you don't want to make your own you can buy them from SC-Power, see picture at the bottom of this page... http://www.sc-power.co.uk/pages/SC-Power-engine-mo....