Don't like the adverts?  Click here to remove them

Aftermarket exhaust sizing



Now call me an old fart if you like (my girls have for 35 years now)
but I cannot understand why an aftermarket manufacturer charging a
not unreasonable price for the job would want to fly in the face of
the wisdom of the OEM manufacturer.
In my days training as a diesel engineer, I was taught that all
components were made to a specification that was nearly always a
trade-off between ultimate performance/quality and budget
requirements. But the final arbiter was providing good life and
performance for an appropriate price which represented value.
So if Toy say it should be 60mm OD why would this manufacturer be
happy at making it at 51mm OD (rounded-up) ? Or even more pertinent,
why would anyone want to buy a replacement system which was at least
20% smaller?
To confuse me even more, my basic HZ non-turbo has a system that has
an OD variable between 59-62mm - according to my vernier tonight. Yet
this current debate refers to higher powered (higher exhaust volume
throughput?) engines with either an additional turbo, or a turbo plus
another 12 valves. Maybe an example of where the diameter should be
larger still; but there again, it might be a good example of the
balance between performance versus budget requirements in the OEM's
mind. Though still puzzles me why a smaller replacement system should
even be considered.
When I first got my 80 and needed a new system I went along to an
alleged 'specialist' who showed me in great detail exactly what he
would do to make me a new system. But when I asked why he was showing
me 50mm tube, and he replied it was the largest he could work with, I
politely thanked him and walked away, later buying OEM of the correct bore.
Am I missing something here ?
Sorry to interrupt.
Tring, Herts
'92 HZJ80 ex UN Bosnia surplus - with OEM exhaust but soon needing a downpipe.


Hey Jon
I dont know about others, but I was looking at the same sixe exhaust or
definitly not smaller.
So the choice for me anyway was to go for Toy at the same size and made of
the same stuff that lasted for years on the cruiser.
Or to go for the same size or bigger in SS which will last longer than the
But then how long does anyone of us need an exhaust to last, cause I think
mine is 15 years old and granted it has been patched, pasted, wired,
strapped and welded from time to time.
But it has lasted that amount of time and been able to be repaired aswell.
I dont know if you can repair or need to repair a SS exhaust at all, and if
it did need repairing would it be one of these special places where they can
charge you what they want.
How long will I keep the cruiser is the big exhaust question..
But it would seem logical to me to way all the options up and decide which
is the best product for the best price with the best hope it will be better
for the cruiser.
So its the price of the Toy exhaust and fitting versus the SS option in the
21/2 or 3 inch with fitting and possibly a larger dump pipe aswell if that
fits into the budget.
This is what I seem to have learned in all the debate anyway.
I have only been able to sourse the SS in the Uk so far but hopfully now the
other Irish members will be able to put me straight on that and save me
having to fit in a ferry crossiing etc.
Althought it would be an excuse to meet some of you again which would be
great, but I can hear you all thinking up excuses already.
O god how can I get out of meeting him again, once or twice was really
John 92 HDJ 80 1HDT