ElDude at Allison Automotive
Active member
:grin:
Thought i'd post a big old moan about the state of the exhaust systems on FRP's these days... :x
Anyway, before I pass any big opinions I have, I thought i'd present a few hard FACTS!
Firstly, as we all know the original Janspeed system was a Steel system with flange fit joints
The only 'flexi' part of the system was actually at the sealing ring at the bottom of the manifold, this was neatly designed into the system by using a MACHINED OUT spacer in between the flanges, that when tightened up lipped over the shoulder of the bolt and prevented any further tightening and so the springs were only partially compressed (you see where this is going :idea: )... also the nature of the mild steel design also allowed for a certain amount of flex in the material itself.
The system fitted well and sounded superb!
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Here's a picture of the shouldered bolt and machined out spacer
I doubt there's many owners out there now that even know this existed..
OK, so you can see the state of the other bolt.. this is because the spacers are now all a thing of the past, they are all discarded (often because they rusted onto the bolt and were not easy to separate)
So basically what i'm saying is, if you're not using the original design, don't bother fitting the springs!...they're completely pointless and just get crushed down anyway...
there's an inherent problem in the whole design in that the only point of flexibility is where you're trying to get a good seal on the Crush ring. Which also leads me on another thing. The original sealing ring was literally a 'crush' ring that allowed you to crush it down and achieve a decent seal. The ones you get now are as hard as a brick and very tightly woven. There's no way you're getting a seal up to that unless you can clamp it with reasonable torque.
Over the years, the flange fit design has become more inaccurate making the systems hard to match up. When you then take into account the material used now, Stainless Steel which is very brittle and rigid, some of the systems now fitted are so ridiculously rigid that it is making the exhaust and the whole engine rigid too.
I fitted a stainless manifold last year that was so long, when I connected it up to the rest of the exhaust I found I couldn't get the bolt in the lower torque mount anymore as it had tilted the whole engine so much... I had to 'make it fit' as you do with many copied parts...
Check out this picture...this is a great example...
The exhaust is so rigid from poor fit that the mount can't absorb anything or even fit correctly as it just stretched to death... The springs are crushed down and loads of exhaust seal has been applied in a desperate attempt to make a seal. The cat shroud isn't there either...
Also, with regards to stainless/steel etc...the stainless systems I have seen are all welded up with mild steel fittings and flanges which present the same rust issues years down the line anyway... I just can't see any benefits to the stainless systems at all. They don't even sound very nice :lol: They're not a patch on the original system...
I've been in one or two frp's that were so loud you literally just wanted to get out after a few minutes of driving..
I think it's a shame that the current systems sound so poor compared to the original and no-one has put any real thought or care into actually improving it..
Anyway... i'm going to be a rebel... I'm going to develop a whole new mild steel system...more on that soon...
Chris
Thought i'd post a big old moan about the state of the exhaust systems on FRP's these days... :x
Anyway, before I pass any big opinions I have, I thought i'd present a few hard FACTS!
Firstly, as we all know the original Janspeed system was a Steel system with flange fit joints
The only 'flexi' part of the system was actually at the sealing ring at the bottom of the manifold, this was neatly designed into the system by using a MACHINED OUT spacer in between the flanges, that when tightened up lipped over the shoulder of the bolt and prevented any further tightening and so the springs were only partially compressed (you see where this is going :idea: )... also the nature of the mild steel design also allowed for a certain amount of flex in the material itself.
The system fitted well and sounded superb!
-------------------------------------------------------------------------------
Here's a picture of the shouldered bolt and machined out spacer
I doubt there's many owners out there now that even know this existed..
OK, so you can see the state of the other bolt.. this is because the spacers are now all a thing of the past, they are all discarded (often because they rusted onto the bolt and were not easy to separate)
So basically what i'm saying is, if you're not using the original design, don't bother fitting the springs!...they're completely pointless and just get crushed down anyway...
there's an inherent problem in the whole design in that the only point of flexibility is where you're trying to get a good seal on the Crush ring. Which also leads me on another thing. The original sealing ring was literally a 'crush' ring that allowed you to crush it down and achieve a decent seal. The ones you get now are as hard as a brick and very tightly woven. There's no way you're getting a seal up to that unless you can clamp it with reasonable torque.
Over the years, the flange fit design has become more inaccurate making the systems hard to match up. When you then take into account the material used now, Stainless Steel which is very brittle and rigid, some of the systems now fitted are so ridiculously rigid that it is making the exhaust and the whole engine rigid too.
I fitted a stainless manifold last year that was so long, when I connected it up to the rest of the exhaust I found I couldn't get the bolt in the lower torque mount anymore as it had tilted the whole engine so much... I had to 'make it fit' as you do with many copied parts...
Check out this picture...this is a great example...
The exhaust is so rigid from poor fit that the mount can't absorb anything or even fit correctly as it just stretched to death... The springs are crushed down and loads of exhaust seal has been applied in a desperate attempt to make a seal. The cat shroud isn't there either...
Also, with regards to stainless/steel etc...the stainless systems I have seen are all welded up with mild steel fittings and flanges which present the same rust issues years down the line anyway... I just can't see any benefits to the stainless systems at all. They don't even sound very nice :lol: They're not a patch on the original system...
I've been in one or two frp's that were so loud you literally just wanted to get out after a few minutes of driving..
I think it's a shame that the current systems sound so poor compared to the original and no-one has put any real thought or care into actually improving it..
Anyway... i'm going to be a rebel... I'm going to develop a whole new mild steel system...more on that soon...
Chris
