Hello all, I am thinking of trying to modfiy the down pipe to allow a little movement in the system so as to relive the stress on the manifolds. Are there any engineers or people that have tried this, or would there be no advantage in doing this at all.
I am at the stage of trying anything to prolong the renewal intervals of manifolds so I was thinking either down pipe to allow movment or even between the cyl head and manifold an as yet unmade non existent flange that allows some sort of destressing to take place.
SS will change the optic to much "don´t want that"....
Roy

 

Quite a question.

Have you considered playing with the mounts?

We have an Aussie member who hand built his exhaust system with some beautiful pipework.

Check out this thread.

 

Hi Richard, I do belive I followed this thread on the no longer exsisting xjr6 forum, might be the same guy, if it is that would be a SS system and it is beautiful work, but I don´t want to go that way for reasons of losing the Jag sound which is close to silence. I havn´t had a SS system yet that doesn´t change the sound of the car inside and out although two of my cars are still running now for over 30yrs on there SS systems which is great for long-life.
Roy

 

Rather than changing the flange, you could use flex pipe just beyond the flange.

 

you can modify the system and allow more flow, i made mine a true duel exhaust system . this allowed more flow and its easier on the manifolds but the downside is you create less boost and you will lose torque down low. Im considering going back to the original system just to get that boost and torque back........ What would you do?

 

Hi all these manifolds will always be a problem until you remove the air injection pump
See how many headers have cracked when you go to the scrap yard and you will notice the ones with air injection are the most cracked something about injecting cold air into a fire which causes the cast iron to expand and contract oddly


Its a known fact here in Australia lots of 70,and 80,s cars had cast manifolds and they nearly always needed replacing at some time due to cracking or warping whereas the same manifolds that where made in the 60,s had no emissions crap fitted to them are going strong today

All the cars I have owned over the years that had some sort of air injection and or emissions system have always had problems the ones that didn't have those features are going strong today

Not to say we would be better of without emission controls its just that they always seem to be designed as an afterthought at the least cost spent on them

If you wanted to get more flow from the standard headers a dedicated twin system is not the way to go just look at the XJ40 cars they had a dedicated twin system of 1inch and 3/4 diameter
The AJ16 goes into a single 2 inch pipe get rid of the air injection make an equal length pipe out of the headers into a 2 1/2 inch pipe get rid of those rubbish flowing underfloor cats and middle section and you might make a difference
Roger bywater from AJ6 engineering made pipes for the XJ40 that removed the underfloor boxes/mufflers they supposedly made 10HP when I tried them on my previous XJ40 my Butt dyno said he must have been close sound was not that bad either but that's up to the individual taste

With all that we know today engines should not need devices fitted after them or before them to make them clean but Government regulations force this in an outdated way on car manufacturers that's why we get the things we do if the government said hey we don't care how you do it but the car must use this amount of fuel and produce this amount of emissions we would see some truly amazing engines but don't hold your breath

I make and sell the S/S headers and they can be made of mild steel as well as the whole exhaust system
Reason I went stainless was never looking at them again

I repaired my cracked headers 3 times in 50,000k,s and that 50,000 was over 3 years the second time they had done less than 10,000 k,s
If you like the sound of leaking manifolds that's fine I would rather a nice exhaust note than the sound of leaking manifolds

 

Plums that is my first though of intention the down pipe flange, but my hunch is the stress would still be considerable and I would be changing the flex pipe after 5-6k instead, still a lot cheaper than a manifold mind you and work time wise not much difference either.
To prolong the life of the flex pipe another flange one that doesn´t exsist, something to cause a cushion effect between the manifolds and cyl head that can take heat and wouldn´t blow, 2 or 3 of the gaskets put in there might even be enough to relieve stress, but I suppose the manifold would warp to the soft gaskets.
I don´t suppose we have any aerospace enginees that would know of a material we could use?


Jeremiahjaguar just out of interest have you been running this modification long enough to be certain that the manifolds are being spared the stress of the standard system. How many mls/klm have you driven with it?
Roy

 

Graham Norri & Jim thanks for the warm welcome and you guys for your replies, but the manifold issue has been put to the back of the que for now. Even though jeremiah I would hang on to the duel system and just add the cream to the cake, swop the M90 SC for a M112.
That should bring you back to asking the tower for landing permission.

Who knows their X300s?

Does anyone know the sequence of the two in tank fuel pumps? For instance when the ignition is switched on do both pumps deliver simultaneously or one after the other, or just one and in which order do they work?? Any information would be welcome.
Roy

 

The second pump wad only fitted to the XJR and XJ12 and kicks in at 3000 rpm. You can probably find a diagram of which is which at JaguarClassicParts.com. I have a 3.2 so I only have a single in-tank pump. That's still enough to get the instant mpg down to 0 on occasion!

 

Thanks theJPster I have found Info now on this, I wish it was my problem. Although the pumps are a little weak and need changing its the top chain tensioner that I have lost and I just hope it hasn't destroyed to much in there. More I can say once I've removed the head and chain cover from the front of engine :-(

 

Wow. I think that's the first time I've read someone say the tensioner actually let go. Hope it's not too bad in there.

JP

 

Has anyone tried wrapping the downpipes on the xjr6? Intake temps are historically 35-40 degrees hotter than outside temp and I would like to get iat down so I could try out my oversized sc pulley. my only concern is the cats on the downpipes, will they ok with the increased temps?

Jeremiahjaguar just out of interest have you been running this modification long enough to be certain that the manifolds are being spared the stress of the standard system. How many mls/klm have you driven with it?
Roy

My statement that less stress is placed on the manifold is based on the fact that less boost is made because I just cut back pressure in half by a true duel exhaust system. My car runs great and it is fast, but losing that back pressure took away from boost, torque and made it shine up top.

 

That's what left me scratching my head...I removed the top tensioner it was complete and looked not new but intact, I pulled the piston out and the spring is not broken but the metal base inserted in the tensioner spring has broken in half and looks crunched, the other half seems to have departed from the inside of the tensioner (How!) causing the chain to slip the cam sprockets and damaging the inlet valves, to what extent I'll know when I've removed the head.