OliverSedlacek Posted May 25, 2012 Share Posted May 25, 2012 Ever since converting from 4 speed to 5 speed (type 9) gearbox, I've been suffering from a lot more heat in the cockpit coming through the tunnel. It dawned on me last night that 5th gear is indirect, so it probably generates more heat than the straight through top gear of the old 4 speed box. So, does the type 9 5th gear really produce a lot more heat? (It's a BGH box with 0.89 : 1 ratio)? Can I fit a gearbox oil cooler to get the heat out of the tunnel, and if so, where should I mount the radiator? How expensive would a Caterham 6 speed box conversion be together with a longer diff ratio (Ital axle), and would that actually help? Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted May 25, 2012 Share Posted May 25, 2012 You're probably better off sticking tin foil to the inside of the tunnel... I've never noticed it getting unbearably hot though, is there enough oil in it? Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 25, 2012 Author Share Posted May 25, 2012 I've tried insulating material with no sucess ☹️ Link to comment Share on other sites More sharing options...
myothercarsa2cv Posted May 25, 2012 Share Posted May 25, 2012 Is the tunnel closed off on the underside on a live axle? Link to comment Share on other sites More sharing options...
Eugene Posted May 25, 2012 Share Posted May 25, 2012 I made the change to a 5 speed some time back - no noticable difference in heat... Are you sure something else isn't to blame? Link to comment Share on other sites More sharing options...
michaelw Posted May 25, 2012 Share Posted May 25, 2012 Some years ago there was a discussion on BC about putting a vent in the rear panel to let air out, no idea whether anyone has tried this but would presumably be another option. Air around the gearbox must stall as it has nowhere to go? Michael. Link to comment Share on other sites More sharing options...
stevemersey Posted May 25, 2012 Share Posted May 25, 2012 My tunnel gets pretty warm too. The gearbox has just been rebuilt by people who know what they are doing, works perfectly, and it correctly filled with oil. You are not alone! Link to comment Share on other sites More sharing options...
john milner Posted May 25, 2012 Share Posted May 25, 2012 My 5 speed has no heat problem. When I first bought it I did think the footwell/tunnel was hot until I realised the heater valve was incorrectly set so it was permanently open by a tiny amount. Link to comment Share on other sites More sharing options...
millsn Posted May 25, 2012 Share Posted May 25, 2012 I reckon it's heart from the exhaust manifold personally, I suspect it just makes it's way out down the tunnel. For as long as it travels the car will heat up esp at speed Link to comment Share on other sites More sharing options...
Racing Snake Posted May 25, 2012 Share Posted May 25, 2012 A gearbox oil cooler will not help Its the combined heat from the engine bay and the chassis acting like a heat sink Link to comment Share on other sites More sharing options...
Jason Plato Posted May 26, 2012 Share Posted May 26, 2012 my gearbox also runs hotter this month 😬 Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 26, 2012 Author Share Posted May 26, 2012 With 23 years of ownership, I can confidently say that it isn't exhaust heat. Heat from the tunnel has only been a problem since I changed to the 5 speed box. Link to comment Share on other sites More sharing options...
Racing Snake Posted May 27, 2012 Share Posted May 27, 2012 Oliver Try one of those sticky temp stripes on the box and gearbox tunnel in the cockpit and take some readings My gearbox runs at 70 degrees average and i would think it might produce more heat being a sequential box Edited by - Mad Hatter on 27 May 2012 19:56:24 Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 27, 2012 Author Share Posted May 27, 2012 Well the inside of the tunnel by the gearbox gets to about 20C above ambient, but it's the outside of the tunnel that makes me hot. Link to comment Share on other sites More sharing options...
Terry Field Posted May 29, 2012 Share Posted May 29, 2012 Oliver I have the same set up and when I first had the car, the heat from the tunnel was almost unbearably hot. All I did was to seal the edges of the tunnel cover with reasonably thick foam strip so that it fits snugly against the tunnel itself, and that cured the majority of the problem. The tunnel cover has a leather type cover (not plain ally) which is slightly padded and that stops virtually all the heat within reason. I would look strongly at the insulation route Terry Link to comment Share on other sites More sharing options...
Rampmonkey Posted May 29, 2012 Share Posted May 29, 2012 Just to throw into the mix... I've always (I say 'always'; BOTH Sevens I've ever owned!) had significant heat from these types of gearboxes. It was a welcome source of warmth in my previous car, now it's just an accepted thing. I did a bit of digging through some mechanic mates and apparently the Type 9 simply 'gets a bit warm sometimes'! How technical! Not much help, unless you're looking for someone to say 'no worries'! I've had no issues at all.... Here's to some Bank Holiday petrochemical consumption!!!! Jase Link to comment Share on other sites More sharing options...
zetec Posted May 29, 2012 Share Posted May 29, 2012 1: make sure your heater isnt stuck open. 2: you dont need one now so bin it. 3: see if a bit of ali angled plate forcing air upwards or outwards might help Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 29, 2012 Author Share Posted May 29, 2012 A plate where? Link to comment Share on other sites More sharing options...
zetec Posted May 29, 2012 Share Posted May 29, 2012 Just thinking if you could angle a plate below tunnel to try & extract airflow from tunnel. Almost like a brake duct or similar to channel out airflow & drag hot air from engine & gearbox area. Just an idea- i wait to be shot in public shortly Link to comment Share on other sites More sharing options...
Racing Snake Posted May 29, 2012 Share Posted May 29, 2012 Polishing uo the Beretta now 😬 I certain Mr Fletcher Senior has a CSR with an air duct under the nosecone that is ducted back to the gearbox tunnel area, could be worth a try Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted May 29, 2012 Leadership Team Share Posted May 29, 2012 There was a lot of discussion about this some years ago. IIRC a problem that was highlighted was the inability for warm air to escape at the rear of the tunnel, leading to a raised temperature along the length of the tunnel. High power engines can cause a similar problem. If you are able to create a way of letting the air out at the rear you should reduce the temperature. I think Richard Lee many years ago did a modified tunnel cover with mesh at the rear section rather than fully closed, thereby allowing the heat to escape upwards. Stu. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 30, 2012 Author Share Posted May 30, 2012 What I really need is some trustworthy aero data so that I can find the nearest low pressure area to suck the hot air out. Maybe it's time for some aero testing. Link to comment Share on other sites More sharing options...
Eugene Posted May 30, 2012 Share Posted May 30, 2012 I've just realised, I have a live axle, and I bet that makes a big difference... Never looked at the rear of a de-dion, but does it have a closed tunnel? With my live axle I have a decent size opening at the rear... Link to comment Share on other sites More sharing options...
OliverSedlacek Posted May 30, 2012 Author Share Posted May 30, 2012 Mine's a live axle but it's mostly paneled under the axle so the openning isn't that big. Link to comment Share on other sites More sharing options...
MartinWoodham Posted May 30, 2012 Share Posted May 30, 2012 de dion has an open tunnel unless someone's gone mad with adding weight. btw the ali plate at the end of the passenger footwell on my car gets too hot to have your feet against it when being driven on track - and that's through socks & shoes. The heat from the zaust primaries has to go somewhere, I'd guess most goes down the tunnel. Is the 5-speed box wider than the 4? if so there'll be more constriction meaning that the heat will build up/ transfer more? is there a difference heat-wise between passenger and driver sides? if so this would support the zaust heat theory - if it's all from he box surely it would be the same both sides? Link to comment Share on other sites More sharing options...
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