UK and US spec difference
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Besides compression ratio my understanding is that the ignition advance/timing curve cost a few horsepower. Of course there's the cat converters as well....a few horpower there, too. Emission controls, as mentioned.
But horsepower ratings have as much to do with the advertising and marketing dept as they do with the engineering department.
The lower compression was standardized for all markets when Marelli ignition was introduced....and I don't recall that Jaguar lowered the advertised horsepower on the non-USA cars :-)
Cheers
DD
But horsepower ratings have as much to do with the advertising and marketing dept as they do with the engineering department.
The lower compression was standardized for all markets when Marelli ignition was introduced....and I don't recall that Jaguar lowered the advertised horsepower on the non-USA cars :-)
Cheers
DD
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US versions had much stricter pollution controls, which rob a lot of the power.
aside from that there is of course the steering wheel on the opposite side, which was to accommodate the fact that their tea cups have a handle on the left side as opposed to US who have right handed cups.
aside from that there is of course the steering wheel on the opposite side, which was to accommodate the fact that their tea cups have a handle on the left side as opposed to US who have right handed cups.
So with nothing else does that mean there is 30 some odd hp trapped in the cats?
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Correct on the air injection costing very little horsepower.
I think the compression ratio is probably most significant followed by timing and cat converters
UNCLOGGED cats don't really soak up all that much, IMHO. 5-10 hp maybe? I gutted the cats on mine and hardly felt any difference at all...a bit more at high rpm is all
Cheers
DD
I think the compression ratio is probably most significant followed by timing and cat converters
UNCLOGGED cats don't really soak up all that much, IMHO. 5-10 hp maybe? I gutted the cats on mine and hardly felt any difference at all...a bit more at high rpm is all
Cheers
DD
#6
My Aussie spec Marelli 89 runs 12.5cr according to the book.
Well flowing Cats will rob no power from the engine. I have just had mine replaced with 2.5" highflow units. I was talking to the exhaust guy who did the job and one of the restrictions in the OEM cats is their shape. If you look at all performance cats they are shaped with angled ends (unlike many OEM cats that have flat ends), he was saying this greatly increases the flow capability of the cat.
Us Aussies need a handle on each side of the cup...
Well flowing Cats will rob no power from the engine. I have just had mine replaced with 2.5" highflow units. I was talking to the exhaust guy who did the job and one of the restrictions in the OEM cats is their shape. If you look at all performance cats they are shaped with angled ends (unlike many OEM cats that have flat ends), he was saying this greatly increases the flow capability of the cat.
Us Aussies need a handle on each side of the cup...
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Not that easy, and I seriously doubt it'll be 20 or 30 horsepower.
I removed the front mufflers, replaced the rear muffler with straight-thru, and, as mentioned, gutted the cats.
I'll grant you that gutted cats still may not have the best flow but doing so was the last of my exhaust mods and it certainly did make matters worse...or at least not enough to feel in the seat of my pants.
I'd say I picked up *maybe* ten horsepower all told. Just enough to feel. A 25-30 horsepower increase would be unmistakable.
Other mods in the "not much difference at all" category were opening up the air intakes and K&N filters. I felt an improvement over 5500 rpm....seemed to climb to 6500 more easily...but that's about it.
I experimented with a couple different iterations of the vacuum advance scheme with no noticable difference. AJ6 Engineering claims the timing curve and vac advance differences are significant. I must not have used the right one....there are several...or perhaps the difference isn't apparent on the low comp engine.
What DID make a difference was using AJ6 Engineering's Superenhanced ECU. Quite an improvement in mid-range performance. Worth the money, IMHO.
Another big improvement came from a higher stall converter, shift kit, and modified kickdown circuit. This took much of the laziness out of the 400 trans.
Cheers
DD
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