4.2 etype extractor exhaust query

[Bristoletype]

Hi,
I'm new to this forum but am currently renovating a running 68 FHC e type series 1.5. The engine I wish to keep in basic state of tune to preserve fuel economy and low down torque. I would however like to make the exhaust sound a little more representative of a classic sports car without being too loud. It currently has a standard stainless exhaust. I was looking at the AJ6 TT extractor exhaust. Has anyone fitted this to their car? I would really appreciate some feedback on this. Reading this forum it seams like a good thing to stick with the standard cast manifolds to preserve torque. Jag must have done some considerable amounts of work on these originally.

Thanks for advice.
Graham

[Heuer]

Graham

Welcome to the Forum.

There has been a fair amount of discussion, research and money spent on various exhaust systems - try searching on Classic Fabs - but the short(ish) answer is as follows:

1. The cast manifolds work by accelerating (extracting) the exhaust gases at low revs as they are narrow bore/sharply curved. This benefits low down torque but can compromise maximum horsepower at high revs, not something Jaguar were interested in.

2. After-market manifolds are normally of larger bore/gently curved which produces a torque dip between 2,250 and 2,750 rpm unless action is taken to overcome it. This involves inserting a venturi in the silencer to speed up (extract) the gases at low revs. These manifolds do produce a flat torque curve and higher bhp at maximum revs but need to be bought as a complete system.

3. Beyond the end of factory manifolds the type or bore of exhaust system only really affects the sound produced although you may see an improvement in horsepower at higher revs.

4. An 'extractor' system may just be a big bore manifold/silencer suitable for high performance road/competition use as it removes the exhaust gases without introducing any back-pressure; large bore throughout its length. Or it could be a system with venturi's - you need to check with the manufacturer.

5. If you have a goosed engine and want the best performance fit a matching manifold/silencer system which includes the vital venturi's. If you have a standard car and want a bit more noise fit big bore silencers (no venturi's).

6. Best all round combination is cast manifolds/big bore silencers because most E-Type driving is done between 2,000 and 4,000 rpm. Manufacturer of your choice.

Jaguar did a very good job designing the cast manifolds to match the XK engine, which is hardly surprising. On the other side of the engine the same applies - fitting Weber 45DCOE's is 'challenging' because of the substantial airflow through the large throttle plate area at low revs. Weber 40DCOE's would be a better match but they no longer seem to be available.

NB: when I say "silencers" I refer to everything from the end of the manifolds backwards including flexi-pipes, silencers, resonators and tail pipes.

[Bristoletype]

Thank you David for your comprehensive reply and sorry for my late reply!. My wedding and other matters got in the way....
I think I'll got with the big bore system and standard manifolds as you suggest. I just wish I could hear these systems before buying!
I've also aquired a series 3 big valve head so I may fit this in future.

Regards
Graham

[Heuer]

The big bore exhaust system is pretty loud compared to standard - people will hear you coming! At times I wonder whether the original Jaguar purr would be better but the hooligan in me likes to awaken the Kracken and let rip. The tubular manifolds also produce more noise than the cast versions as they ring like a bell as the exhaust vales open.