1992 v12 free up hp
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US cars from what I have seen have a catalytic element in the downpipes. Lost of people remove this from all 4 pipes.
If your Cats are working properly and not blocked removing them (Not the ones in the PIPES) will have very little difference on a stock engine.
To increase the power on the 5.3L there is a couple of things you can do.
Remove the Cat elements in the downpipes.
Increase the size of the trumpets on the air filter boxes
Fit a cold air intake, this can be over the radiator like the TWR cars.
Fit K&N filter elements.
Here is a pic of what TWR did for CIA on the XJS. You can just see it in the bottom right of the pic.
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If your Cats are working properly and not blocked removing them (Not the ones in the PIPES) will have very little difference on a stock engine.
To increase the power on the 5.3L there is a couple of things you can do.
Remove the Cat elements in the downpipes.
Increase the size of the trumpets on the air filter boxes
Fit a cold air intake, this can be over the radiator like the TWR cars.
Fit K&N filter elements.
Here is a pic of what TWR did for CIA on the XJS. You can just see it in the bottom right of the pic.
.
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Greg in France (10-26-2016)
#4
EU model had different valve clearance and compression ratio of 12.5:1, instead of 11:1 for US model. I removed all cats on my '82 HE and gained better power, but only because my lower cats were half melted. That power increase also came at a cost of awful fuel consumption, due to lack of back pressure. Right now I plan installing generic converters in place of the empty lower units. Also I will do what Warren suggested above, for noticeable power gain.
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Models with cats had around 268 hp (272 ps) here in Germany (mine is a UK import).
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warrjon (10-27-2016)
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Just removing the Cats will result in very small power gains. To take advantage of the free flowing exhaust you need to get more air (actually OXYGEN) into the engine.
EU and Aussie spec cars had higher CR due to the higher octane fuel available in those markets, this makes a HUGE difference as the additional Quench acts to cool the charge as it's Squished helping to reduce detonation.
As far as I can tell all Jaguar did to adjust the CR for markets was to change the head gasket thickness. The parts catalog lists a couple of different part numbers.
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Greg in France (10-27-2016),
Jonathan-W (10-27-2016)
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Greg
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ronbros (11-04-2016)
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Jonathan-W (10-27-2016)
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