TVR Cerbera - Joospeed Technical Area

I will shortly create a form that you can ask our resident expert your very own technical questions. A round of applause for Mr. joospeed is in order methinks......

Hydratrack

Airconditioning	The main reason for the air con not working is loss of refrigerant due to the early alloy compressor pipes fracturing...almost all cars have now been changed onto the later steel type which has cured this completely. The air temp we set is around 7 Deg C which seems to have given no reported problems of icing or condensation dripping down. You'll notice that cars without air con have just one cooling fan located centrally on the radiator, whilst air con cars have the bulky Cerbera type fan supplemented by a Chim (non-500) type fan. The airflow through the air con radiator IS by fan in traffic. Incidentally, both the fan control for the air con and the normal engine cooling are both controlled by the engine run ECU.

Hot stalling	As you rightly point out this can be due to the fuel vapourising in the lines, the wrapping of the fuel lines in heat-reflective material was a factory mod for the earliest cars only.. all cars now have fuel lines which run inside the cabin under the centre console (they're metal, so no chance of bursting unless someone drills through for a mobile phone or similar). Also air con cars have the added advantage of a fuel-cooler which is the metal canister in front of the engine just visible under the lower fibreglass cover. Excessive heat transfer through the boot floor from the exhaust back box to the fuel tank was cured by fitting a plate barrier between the rear box and the boot floor on early cars. As a result, hot stalling because of vapourisation was all-but eliminated, and any stalling problems occurring are either as a result of a fault, or more commonly because the butterflies on the O/S bank are becoming blocked with oil from the breather trap in that side airbox. On cold start, the ignition timing is advanced which takes care of the cold-start fast idle, and the timing is gradually trimmed as the coolant temperature increases. It's important that the butterfly area is cleaned every service to maintain the idle speed...it shouldn't be raised just by opening the idle speed stop screw since this ruins the relationship between the rate of opening of the butterfly and the expected change in airflow possibly resulting in uneven slow speed running (for each incremental increase in butterfly angle, the rate of change of airflow decreases).
joospeed says :	Inside the diff casing is the Hydratrak unit, it is self-contained and as such does not run in the diff oil, it contains it's own lubricant which forms part of the working mechanism. Consider the scenario of setting off under hard acceleration causing wheelspin or accelerating out of a tight bend. Under this condition a large speed difference occurs across the rear wheels and consequently a corresponding difference at the diff output shafts ( from the Hydratrak coupling). Inside the coupling itself, fluid is forced through small orifices thus effecting a resistance to the differential output shaft speed causing it. Because this action varies as the speed difference across the output shafts, the diff is "user friendly", the wheels cannot become "locked" as in a power-locking type diff for example and so limits effects such as both rear wheels slipping under clumsy downshifts, and the back end of the car is less likely to step out when exiting slow corners for example. The downside of course is that they make the cars very boring to drive (!) - I mean, what's the point of a fast rear wheel drive car that's difficult to get the back end out on? My driving impressions of Hydratrak-equipped cars is similar to cars having no type of LSD at all- i.e. they seem to sit there going nowhere spinning the inside wheel uselessly if exiting that slow corner for example. My advice to anyone who enjoys what rear drive cars are all about is to stick with the ordinary diff... much more fun, much more 'TVR'.
Door seals
I'm currently arguing with someone about the door seals on my 4.2 could someone please help. Can you fit the 4.5 "double-bubble" door seals onto the 4.2 without further modification to the door i.e, just rip the old ones off and put the new one's on. I want to try and cure this occasional problem I get with wind noise and the odd leak (not often but enough to want to get it sorted)	joospeed says : I've just done this very job on an early 4.5 Cerbera but I have to warn you that it isn't straightforward ( is anything on a TVR?). Firstly the door aperture seal comes off, followed by the lipped seal along the roof top. A new lipped seal with a bigger lip on it has to be fitted with a plastic strip with rivets on it and this is then fitted onto the car. Next the double door aperture seal is fitted. All this is pretty much as you would expect, however because of the extra width of the seal, the door hinges must be spaced out from the car body or the door doesn't shut and this bit is a real pain in the ****!! Then you'll need a different chip in the window ECU in the boot to give more power to the window lift motor or it won't go up to the top. If it gets done inside 8 hours and doesn't leak or have wind noise then consider yourself very lucky.

My Cerbera went in to The TVR Centre on Tuesday for it's 6000 mile service. I have now had the car just over 4 months the TVR centre had it for one of those repairing an endless list of bits including a new drive shaft, 2 wiper motors the list goes on, new rear shock. I have just received a call from the service department with a the following items and a bill of Ł2327.75 I think they are taking the pi** Leak from front Oil Seal 2nd time Clutch Master Cylinder Leaking Plug Leads duff Brake fluid needs replacing (having boiled) Clutch Fluid needs replacing (having boiled) Steering boot split Front suspension springs need replacing as they have dropped. front wish bone split front & rear pads 90 worn leak from rear shock both replaced when I purchased the car all 3 diff mountings split needs new front wishbone & bushes realignment of geometry I can't believe that all these things could go wrong in the 4,000 miles I have done in the car 90% done on M25. Does any one have a box of matches..	joospeed says : this list does seem a bit long, and expensive!!! front crank oil seals do leak and there's not a lot you can do about it. There is now a different seal fitted to the latest engines but I don't actually know if it's retro-fit. If you can live with the oil leak as it is then don't do anything about it- it may leak just as much with a new seal in anyway. Clutch master cylinders are a weak part of all TVRs-it's the same unit used on all current models and it's best to change it-it's a fiddly job but not horrendously expensive. I've never come across a duff Cerbera plug lead yet-they're expensive silicone jobs. The only real problems you get with them is they could have rubbed through on the throttle linkage or ,because they are very difficult to get off the plugs, they could have pulled apart if the mechanic used too much force on the cable part of the lead. The brake fluid may need replacing every 2 years is the recommendation or if it has boiled as they say...but how do you boil clutch fluid? I must say I've never heard of that one. Have the springs really sagged after such a short time? It would seem unlikely-Cerberas do sit unnaturally high at the rear making the front seem low, but I've never had to replace any Cerbera springs ...yet. The pads seem to last ages as long as they are kept free in the calipers-they usually need replacing because the friction material has separated from the backing due to the flexing of the pad when pressure is applied to a seized pad. The worst case of worn pads were on an ex-Kerridges Cerbie that came into HHC for some work, but that really was the exception. Finally, after any suspension work the alignment of the wheels should be checked, preferably on an 4-wheel optical alignment gauge. Does this help you answer any of the questions raised as a result of the list you were handed?