Exhaust System Upgrades
Exhaust system modifications are a common way to obtain a modest power increase on all engines. Several aftermarket exhaust options exist for Range Rovers. Borla makes exhausts for both the Classic and the P38, while Flowmaster exhausts can be adapted to any vehicle. Be aware that any resulting improvements in peak power are not "free"; you may want to look at some dyno testing results in order to figure out what is being sacrificed (usually low speed torque) in order to get the better high speed performance. Also, the high performance exhausts are usually a good deal louder than the stock exhaust, so you may want to adjust your selectio to your (and your spouse's) comfort level. With these caveats, the information below is provided to relate other owners' experiences with exhaust system modifications.
Flowmaster Exhaust Installation
When Perrone T Ford wanted to replace his exhaust system, including the catalytic converters, he looked into the Borla option and the standard replacement exhaust system but decided they were too expensive. Instead, he decided to try new hi-flow cats and a high-flow muffler from the Summit Racing catalog.
For comparison, Atlantic British listed the exhaust parts he needed
NTC6127 (Catalytic Converters @ Y-Pipe) 699.95; ESR1053 (mild steel Exhaust System) 269.95.
The Summit Racing parts were:
CTO6905 (Catco Universal Cat. Converters) $59.95 each x2; FLO42452 (Flowmaster 3 Chamber Muffler) $71.95.
Once getting the parts, he had them installed at Tuffy Auto Center at a cost of $160.00. He gave them instructions to re-use as much of the stock exhaust as possible, having removed the rear muffler the previous week and installed a chrome tip. He also asked them to tuck the pipes and muffler as far up into the frame as practical. The entire muffler and pipe from the muffler to the back of the car now rides tucked up into the frame. The cats do sit below the frame but not as low as the transmission hand brake assembly. The shop was able to re-use all his pipes, but if some of yours are corroded you cna probably still have the entire system installed for under $500.
Perrone warns those choosing this route to be alert for the following:
1. You WILL have to re-torque the bolts after a week or two because the metal flexes with heat and leaks show up.
2. The Flowmaster series mufflers have good heavy construction, but
be sure to get a model to suit your particular taste. They have
from racing mufflers (read: LOUD) to mufflers designed for RVs
but more restrictive).
Perrone is very pleased with the result, reporting that the car now sounds like a REAL V8. The vehicle is much more willing to rev once you hit the 2000 RPM range. He estimates that the car has picked up a few horsepower now that he has opened up the exhaust. Flowmaster claims 10-20 HP. It does feel and sound more powerful in the upper ranges.
Hedman Headers and Flowmaster Exhaust Installation
When Dave Brown swapped a 4.6 engine into his Classic, he took the opportunity to add Hedman headers and a Flowmaster muffler. Photos of the result can be seen on the 3.5 to 4.6 liter engine upgrade page. The performance improvements from Dave's exhaust upgrade could not be separated from those of the engine swap itself, but the overall result was a large boost in performance.