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I'm going to get a new high performance exhaust system for my 1999 Viggen.It seems like most aftermaket exhaust systems are 3" systems.Maptun,JT,Hirsch,Nordic,BSR and Speedparts are all 3" systems.I plan on buying a Abbott exhaust system.Why does Abbott only makes a 2 1/2" system and every one else makes a 3" system.
 

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a 3 inch exhast will allow for less backpressure. if you have a turbo this is good. if you have a non turbo model you will want 2.5 inch. wheres lawrenceburg? im around kokomo, in.
 

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The answer is not so simple...

I believe the reason Abbott systems are 2.5" is to help retain compatibility with OEM. You can replace any element of your OEM system directly with the equivalent piece from Abbott. The same can not be said for the other systems.

The Abbott system is stainless steel, not aluminised. There are other suppliers of stainless steel systems (eg Powerflow in the UK) who manufacture replacement exhausts but they tend to be complete systems only.

For a given diameter, a stainless steel system will perform better than either mild steel or aluminised steel. This is due to the fact that it's hihgh corrosion resistance means there is less build up of uneven deposits/corrosion on the inside of the exhaust. Basically the SS systems reatin a smoother bore, especially after time. The smoother bore assists gas flow by reducing impedance and turbulence.

On NA systems, and to a lesser extent on turbo systems, introducing an overly large diameter exhaust may improve top end power delivery, but can reduce bottom end torque.

Perhaps Abbott also found that 2.5" was an optimum compromise between cost, weght and performance as well as compatibility.
 

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Quote 'This is due to the fact that it's high corrosion resistance means there is less build up of uneven deposits/corrosion on the inside of the exhaust. Basically the SS systems retaining a smoother bore, especially after time. The smoother bore assists gas flow by reducing impedance and turbulence.'

I personally think you are splitting hairs with that statement and don't think anyone would be able to tell the difference in exhaust gas flow in regard to more or less performance due to 'deposits' or corrosion. Every mild steel exhaust I've changed has failed from outside corrosion, the inside of the pipes are as smooth as the day they were made, admittedly, boxes can corrode from the inside if used on short journeys all the time but the corrosion inside the boxes will not impede the gas flow unless baffle plates come adrift.
IMOA the 3" system is the way to go for performance and whether you agree with the statement above or not, you would need major blockages to form for a 3" system to lose its gas flowing ability to drop below the 21/2" system.
I took my original Saab exhaust off about 4 months ago to fit a 3" JT system, after 10 years on the car and 156000 miles, the inside of the exhaust was spotless, but the outside welds etc on the boxes were rusted....but cannot really complain about that as I have it as a spare now if I ever need it.
If you plan to keep the car for the rest of your life then S/S would be the way top go as you can use that reason to justify the expensive prices charged, however, from a performance and cost point of view you cannot beat the JT system.
Just my 2 cents worth...
 

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If I can just throw a cat amongst the pigeons, here, and say that my stainless steel Hirsch exhaust system is neither 2.5" nor 3", but 2.75"
 

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Originally posted by Mark in Ireland:
[qb] 
If you plan to keep the car for the rest of your life then S/S would be the way top go as you can use that reason to justify the expensive prices charged [/qb][/b]
Or, as I have done, transfer the system from one car to another

I would also add that the SS systems I have seen also seem to have smoother bends and surfaces from new
 

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I've had a JT 3" downpipe on my 9000 for 2 1/2 years. It's aluminized steel and I'd be really surprised if it didn't last, at least, another 3 years. There are good and bad aspects to any engineering material. Stainless is known to crack easily, especially on parts that undergo many heat cycles. However, from a flow point of view, a 3" downpipe has 44% more flow area than a 2.5" pipe. The exhaust gases spiral in a helix, out of the turbine, in a direction that depends on the exhaust gas speed - sometimes they go faster than the turbine, sometimes slower. In either case, the path for the gases is lengthened and it is beneficial to create turbulent flow. On the JT, the exhaust pipe diameter, where it attaches to the turbine, is the same as stock, until it gets past the first 180º bend, where it widens to 3". The next few feet are critical to turbulent flow and reducing back pressure. Once you're past the cat', the back pressure the turbine 'sees' won't change much. In fact, one could probably reduce the exhaust diameter back to 2 1/4" after the cat' and notice very little difference (in power, not sound!). The other aspect to consider, especially with modified software, is heat. There is a correlation between EGT's and the size of the downpipe - I haven't seen charts on this, and I may be wrong, but I'm assuming that in this case, bigger is better. Finally, there's price! I paid a little over $200 for my downpipe. I don't think there's a better or cheaper modification one can do to their turbo than this.
 

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Sorry for not responding sooner - a friend from Sweden was kind enough to buy and send it to men. At that time there were no distributors for JT, here in the 'states. Now, there are two that I know of: Engstrom and Talieferro Saab.
 
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