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Walker’s World August 04

Last month I talked about the big yellow XJS racer and how it was suffering from reliability. I am happy to report that it is now fully sorted and the new engine is making very good power. It took a while but the car is now running twin coils and a split level distributor plus it’s firing the injectors in four banks of three. The gearbox is also now fully sorted and it no longer jumps out of 4th gear. Now the bad news (there’s always some bad news with this car) the car had a spin in the race and another XJS drove into the front of it at high speed. It’s back to the bodyshop before the next outing.

Red Rose

The TVR Red Rose Cerbera that’s featured on the site has now been back with a new exhaust system. The photographs do not do the system justice – it’s a work of art. The pipes are now equal length primary and cross over at the front of the engine – it was the only way that BTB Exhausts could get them in.
The exhausts in themselves made more power but the plan was always to combine the new exhaust system with a change of inlet tract length. The owner, Julian Rowntree, had calculated the lengths that would give him the best torque are various RPM points and had put together a little kit consisting of some rubber hose and a set of intake trumpets.

We tried various lengths by the simple expedient of cutting the rubber to length – obviously starting long and shortening since it’s a lot harder to put back than to cut off! The end result was well worth the effort. The car is now making 411bhp that we could record on the rolling road. Actually the power had “clocked” the rollers exceeding the power that we can read at the wheels so it may be a few brake more but who’s arguing?

Now Julian has to make up an induction system of the given length but shaped so that he can close the bonnet! There is also a small cooling problem to be addressed as the new exhaust slightly reduces the flow through the radiator. Any development operation takes time but the car is getting there.

Cosworth 4 x 4

This is not your ordinary Cosworth engine; it features a Turbo Technics supercharger as well as a big turbo. The supercharger is belt driven from the crankshaft via a magnetic clutch and the pressure then feeds the turbo. At 4600rpm (peak supercharger speed) the charger cuts out and the turbo takes over – in theory.
This is one of the few cars that we have run that does not have our ECU. We did the car for a friend of a friend and after it had been detonated on the first mapping session. The turbo does nothing until you get to about 5000rpm and then all hell breaks lose. The idea is that the supercharger in effect spins up the turbo and then leaves off for the turbo to take over.

Needless to say it was a bit of a bitch to map because we didn’t have the mapping wheels that normally come with the system. The software had to be operated with the mouse – while you bounced up and down in the seat.
There was also a problem with the boost control, either the valve or the way we operated the software. The supercharger made tremendous power up to 4600rpm but when it cut out the turbo wasn’t up to speed. Having to set the wastegate to limit the turbo boost meant the supercharger was opening the wastegate so the turbine wasn’t spinning up – we think.
The key to the conversion will be to get the waste gate control working from the ECU. For the time being the owner, Kevin Salisbury, will have to make do with 330bhp on his next outing up the hills.

X-Flow

You don’t have to spend fortunes to get full management on your engine. This Westfield has a set of home-made throttle bodies from a set of carbs. The big advantage is that you get a known system – throttle linkage, balancing system, air filters, etc.
You can trigger from a distributor to keep things simple although I am told that things like rotor arms and distributor caps, of a decent quality, are getting harder to find.
This particular car has a very good torque spread and makes over 140bhp - which isn’t a lot by today’s standards but the car does beat a lot of more powerful K-Series cars up the hills.