Stumbled across this little nugget in the X350 Technical Guide



Wonder if these would be of any benefit to the S/C cars?

A pair of manifolds from a wrecker would certainly be cheaper than custom headers that have been mentioned from time-to-time.

Bear in mind that this technical guide was from the launch in 2003.

Looking in the parts catalog, there was a change in design from the 2006MY, with the 3.5L and 4.2L N/A getting unique part numbers for the manifolds. The 2006MY also got a change in P/N for the 4.2L S/C exhaust manifolds.

Earlier models had one part number for both the 3.5L & 4.2L N/A manifolds (which would be the tuned versions refered to in the tech guide) and one for the S/C which would be the "log" design.

Not sure if the 2006MY onwards still had the tuned manifolds...

But this might be something worth looking into?

Left manifold:



Right manifold:

 

That certainly is interesting... I bet the
reasoning for not including it was eco-
related, not performance related.

Headers for $3500 sounds like a typical
power-per dollar increase for the XJR.

A 25hp tune for $1600, is a bit better,
a cat-back is 20hp (supposedly) and $1200,
and pulleys are a few hundred (plus the big
installation.)

At least we don't drive an M5, where anything
more than a 25hp increase can only be achieved
with $7000+

 

Going to fit these to the next 4.0s/c unit I do...

 

Begs the question why Jaguar hasn't used these on the R models, although the range rovers SC models do have these type of headers on the 4.2 engines.

Considering the very low results of the bip headers (would have expected more actually), it may be that there just isn't enough gains to be found.

But have no experience myself with headers, so can’t explain the why unfortunately. Biggest gains are at least seen in the swap from stock to sports cats.

 

I put these in the same bracket as the VVT, left off the S/C cars to save money. Just chuck a blower on & it did 400HP, done, no need for the add ons. And by using cheaper exhaust manifolds & leaving out the VVT, the extra costs of the supercharger and intercooler system could be offset.

I already blew it on this subject, so i don't want to be too vocal now.
Yes it's a bit disappointing, and i still have my doubts about the testing process.
We don't know the condition of the cats on the "before" run.
It would have been better if they had done four separate tests;

1. Stock exhaust manifolds & stock cats
2. Stock exhaust manifolds & no cats
3. BIP heaters & no cats
4. BIP heaters with cats

It's been shot down, but I can't ignore what our mate in South Africa saw when he removed the cats on his XJR. Comparing the BIP headers without cats to the stock headers without cats would have been the best indication of the available gains. IMHO...

100% agree, especially if the original cats have a lot of miles on them and were blocked up.

I think for the cost, it's just something to do, very unlikely that someone will do a back-to-back test. So long as they pass a visual test (same/bigger port sizes compared to the "log" ones) then they can't hurt.

They are on my shopping list.

 

You do know that Jaguar fitted VVT to the later 4.2 SC engines…

There must be some increase in performance for the “branched” headers; otherwise I can’t see why they used this concept on RR the SC engines as well, but probably not big.

You couldn’t see exactly the run numbers on the dyno slips, but from the baseline to the latest with headers & cats it looks about 10. So they probably picked the favorable ones for the headers and headers with cats.

Now when you add about 15 rwhp on the base line (which is about right for the richer mixture on that run), and then add for instance sports cats (so another 10 rwhp), his base line would be about 331rwhp.

Considering they showed only the best runs with their headers, would mean only 8 rwhp extra for Bips headers + cats and 15 rwhp for the cat less one.

They definitely would need some new tests, but considering now that with the “branged” headers gains are low, am not so hopefull anymore.

But even if it would be 10rwhp, for the secondhand headers and some welding to fit sports cats, the costs are low enough to go for it I guess now. I may even think about this myself ;-)

 

Yes I know that the later 4.2 got VVT. Probably better to leave the VVT discussion in the other thread https://www.jaguarforums.com/forum/s...s-quest-33023/

What do you mean by "branged" ?

I really don't know what to expect from the N/A exhaust manifolds. But there would have to be some improvement. The Jag tech guide said "increases torque at low engine speed" this is not something that can be easily measured on a chassis-dyno with the automatic boxes in our cars.

But if you could pick up a pair cheap enough, then there is no reason why not to try em. Would you do a dyno run before & after?

 

"Branched"...

Not sure if I will do sometyhing like this, it will be a lot of custom work, maybe when my current sport cats need to be renewed it would be something to consider.

 

Well I just picked up a pair of 4.2 N/A exhaust manifolds off an S-Type.



Cost me just £45 in the UK, but unfortunately another £60 in shipping...

I'll get them fitted along with 200 cell cats & a custom exhaust in Sydney, probably Q3 of 2013...

Long time to wait, but that's how it is at the moment...

 

Great job Cambo, but do you know if these will fit
the stock 4.0 catalysts?

 

From the looks of things, no. You'd have to go with custom cats.

 

That's a disappointment, what an easy mod it could
have been. But there is hope yet. The 4.2 XJ8 manifold
is dfferent than your S-Type ones.

2004 2005 2006 2007 Jaguar XJ8 XJ8L Vanden Plas Engine Exhaust Manifold | eBay

 

Saw those ones too, they are the same as the S-Type ones, didn't get them because shipping from the UK is a bit more reliable.

Photo is taken from a different angle. You can see the split in the outlet flange which is the separation of the pairs of cylinders.

 

I am new to Jaguar; and am surprised that there is so little interest/mention of exhaust manifolds and headers among tuners. Most tuners seem to dwell soley on cat back exhausts and cat deletes.

My most recent personal experience with headers is an '05 Cadillac CTS-V. I was an early adopter of long-tube headers from TPiS, Inc.. TPIS dynoed a large hp gain in header development, like 25+ hp, compared to 10-12 hp with just a cat-back exhaust. TPIS recently tested long tube headers on a late model supercharged CTS-V with similar gains compared with NA.

At that time California Air Resources Board (CARB) rulings became very restrictive, effectively making long tube headers illegal. The basis for these rulings was that CARB wanted the cats to more quickly warm causing the ECU to go to closed loop all that sooner. CARB's has since further ruled that it is unlawful to change from OEM forward of the cats.

Under the first ruling, some aftermarket manufacturers developed "shorty headers" to keep the cats in the same OEM location (close to exhaust ports as possible). These shorty headers are now illegal in California. Shorty headers produced reduced gains compared to long-tube headers, say in the area of 10 hp. The shorties resemble the tuned OEM manifolds shown above.

I know that several tuners have tried to reason with CARB arguing that the efficiencies of long-tube headers cause lower overall emissions long-term than shorties. In my personal experience CARB is very rigid, non-technical and theological in its rulings.

I have been looking/researching for Jaguar headers. Came across one mfg in UK (forget the name) advertising in Jaguar World, but could not access their web site. They were asking silly money for headers, which looked like simple shorties.
In the '05 era (not that long ago) many headers were still steel with coatings like JetHot. These coatings are very durable, but the market has changed a bit and customers are demanding stainless steel headers. SS is much harder to work, and some vendors have farmed out their header mfg to SS specialists, like American Racing Headers (AFR).

American Racing Headers is well-established and has a good reputation for quality/performance. Some months ago I emailed AFR asking if they were interested in producing headers for Jaguar post '07 XK/XKR. They replied asking production numbers. I guessed at well over 75,000 world wide. To date no further comment/interest from AFR.

I wondered if anyone produced headers for the American Ford Thunderbird '02-'04, which used the Jaguar-designed motor. I found one source: 02-04 Ford Thunderbird Headers from Stainless Works at Andy's Auto Sport. I am uncertain whether or not Jaguar and Ford used the same basic cylinder heads. One would logically compare exhaust manifold gaskets to confirm this.

Not long ago Stainless Works was showing the T-Bird header on its site, but now they seem involved only with custom applications. Stainless Headers Mfg., Inc. fabricates custom headers in stainless and mild steel. I suspect the market for T-Bird headers was miniscule.

I have not contacted Stainless Works to date. They are located in Fargo, North Dakota, far from any major city. At this time I am personally a bit cool on the subject, realizing that improvements to a cat forward exhaust would be a major pioneer project for me. I'm still in a research mode.

 

You need to put some spaces in that big chunk of text, it's very hard to read. Paragraph...

Now...I remember seeing the "shorty" headers for Mustangs in the Ford Motorsport catalogs 15 years ago.



You can still get them for the Mustangs.

Back in Australia we didn't have them for our homegrown V8's (Ford & Holden/Chev), you had a choice of Tuned Length (Long Tube) 4-1's or Interference type 4-2-1. The 4-1's typically had a 2-1/2" or 3" collector, the interference maybe a 2-1/2" or usually just 2-1/4" outlet.

When I first started looking for headers to suit the Jags, the Shorty design came to mind, more because of the very tight space, rather than any emissions issues. And if someone had to make them from scratch, they would certainly be cheaper than a fabricated Tuned Length 4-1 that had to be dissassembled in order to install them in the car. (I haven't checked, but I reckon I could get a pair of Shorty's custom-made in Australia, out of mild steel, 2-1/2" outlet, for less than $1500)

There are lots of discussions on the Mustang forums about Shorty's vs. Long Tube, here for example Shorty Headers vs. Long Tube Headers - MustangForums.com the general consensus seems to be Shorty's give low-rev gains but not much in the top end. Long Tube give massive gains in the top end, with perhaps even a loss in the lower revs.

So, what about these cast factory tuned manifolds? The question yet to be answered, is what size is the outlet flange?

I've not had the possibility to measure them, will be nice if they have a 2-1/2" outlet, if so then the "tuned" factory manifolds will be as good as you can get without spending stupid money. But I suspect they will be a little smaller, probably 2" or if we are lucky 2-1/4".

Now, you have probably seen the BIP threads showing their hand-made 4-1 tuned length headers, for asking price and the apparent HP gains, I could never justify them. In all fairness to BIP, that's what they have to sell them for, they are a business after all, not a charity.

But these cast tuned manifolds on the other hand, will certainly be a step up from the logs on the stock S/C cars, maybe not as good as a Shorty with a 2-1/2" outlet, but that is yet to be seen, until i've actually got them here in front of me & measured the outlet, it's all theoretical.

 

Fixed, nice post, now it will get read by more members.
Vector

 

Oh dear, I just found a post from Count Iblis https://www.jaguarforums.com/forum/x...38/#post369566

This doesn't bode well for using the N/A manifolds on the S/C...

 

http://www.altairhyperworks.co.uk/ac...son_Jaguar.pdf

This was pretty interesting, it was however way over my head. This lab tested Jaguar V8 manifolds in all sorts of different manners.

 

Hello, haven't been on in a while. My Jaguar has been festering with broken diff in the garage next to the Challenger with its engine out.

If pursuing a branched exhaust manifold the GROUPING connection of the cylinders needs to be as the NA design is but with enough cross sectional area to allow at least 1300 kg/hr engine air flow (about 400 bhp) volume throughput (rather than the NA engines 700-800 odd kg/hr).

I hope this helps

 

Thanks for the info Count. Sorry to hear about your diff...

As it turns out the freight company lost my package with these N/A exhaust manifolds, so I haven't even had a chance to look at them & get any measurements.

But yes your proposal would be the idea, make the new manifolds as big as possible, using the grouping of the N/A manifolds. At least we know what has to be done now.