Most TVR owners will be familiar with Clive Ford’s stainless master pieces in the form of his popular manifold Y Piece. Last year Clive surpassed himself and created a tuned crossover manifold system, the same design as seen on the legendary Le Mans winning Ford GT40 that somehow fits under the bonnet of a Griff.
So what is the point of a crossover manifold? The issue with a conventional 4-1 exhaust header is the separation between exhaust impulses. With a 90° (cross plane) crankshaft 2 exhaust pulses exit through the collector at the same time. A crossover manifold pairs the correct cylinders that fire 180° degrees apart in their firing are paired together, maximizing scavenging. When one cylinder is on the compression stroke, the other is on the exhaust stroke resulting in a constant flow, thus creating equally spaced exhaust pulses.The result is similar to that of a 180° (flat plane) crankshaft with four evenly spaced exhaust pulses in each header.
I had managed to resist the temptation of Clive’s latest masterpiece until I bumped into fellow Griff owner Peter Billington at the Griff Growl last year. Peter has a immaculate, sensibly modified Griffith and had just completed fitting the crossover manifold system. Peter very kindly offered to take me out for a spin in his to demonstrate the new manifolds and I was sold. The sound was incredible, a cross between a RV8 and Cerebra with the howl of a GT40 higher up the rev range…. epic! A few weeks later Clive received an order.
I am still running the OEM Lucas 14CUX ECU on my Griffith. I asked Clive to build the manifolds with two narrowband lambda sensor bosses (one per bank) for the 14CUX and two wideband lambda sensor bosses for a future expansion (aftermarket ECU). I also asked for a wideband lambda sensor to fitted where both banks merge to allow me to run an AFR gauge at a later date.
Running the 14CUX with this system does pose an issue in that the lambda sensors in standard configuration read from cylinders 2,4,6 and 8, and 1,3,5 and 7. With the crossover manifolds fitted the sensors read cylinders 1, 4, 6 and 7, and 2,3,5 and 8. The 14CUX is bank fired so to correct this it is a simple case of extending the injector wiring so injector wires 3 and 5 are swapped for 4 and 6.
Changing manifolds on a TVR is always a time consuming job due to the lack of access to the bolts. 2 long evening later the manifolds were fitted. The water pipe to the radiator was rerouted underneath the chassis rail and I took the opportunity to fit a JE alternator bracket to replace the tensioner.
First impressions are very good. The car seems to rev much more freely and the sound is epic. Below is a quick test on a cold day in February with new tyres so not going too mad. I will record a better video soon…
The car went to Dom at TVR Power for a service in March, while the car was in I asked him to put the car on the dyno for a power run to check the AFRs and also see what difference the manifolds made.
2016 Dyno Result
275.17BHP & 295.93ftlb at the wheels.
TVR Power dyno reads in wheel figures so I have converted to flywheel figures using the below site
BHP – 324BHP
Torque – 348ftlb
2017 Dyno Result
274.52BHP & 301.77ftlb at the wheels.
BHP – 323BHP
Torque – 355ftlb
Peak torque is up a bit but I am mainly impressed by the healthy increase in bottom end torque. The result is certainly promising but the car is running rich now so not really a fair comparison without a remap. There will certainly be more come with an adjustment on the fuelling and the addition of mapped ignition.