Thread: 2.5 or 3 inch Exhaust for TD5.

Taipan exhaust is on the gold coast, in burleigh heads, i asked for a quote for my defender 300tdi and it was approx $1800, it is a good system they suggested i replace the intercooler and get a dyno before fitting as that will effect the performance after. Dyno to compare before and after. all stainless steel so not prone to rust.

Getting my 02 Disco done tomorrow at Fat Pipes Kallangur,

my td5 130 is chipped and has 3 inch mandrel exhaust.had no muffler when i bought it but put straight thru in middle.still sounds mean but not as loud.running 18 psi boost,heaps of go,26 would be unreal.dont know for how long though.

Boost don't kill them egt's will

Exhaust tracts are carefully designed (within all the given constraints) to give the best compromise in terms of backpressure, volume, heat dissipation, etc.

Whatever modifications are made the equivalent size x length should remain approximately constant.

Smaller pipe means higher exhaust gas velocity (less heat absortion) but greater back pressure (increased turbo lag).

Larger pipe will cause increased turbo and exhaust manifold heat retention (in other words higher EGTs) and can potentially cause turbo over speed in detriment of its life span.

Originally Posted by mturri

Exhaust tracts are carefully designed (within all the given constraints) to give the best compromise in terms of backpressure, volume, heat dissipation, etc.

Whatever modifications are made the equivalent size x length should remain approximately constant.

Smaller pipe means higher exhaust gas velocity (less heat absortion) but greater back pressure (increased turbo lag).

Larger pipe will cause increased turbo and exhaust manifold heat retention (in other words higher EGTs) and can potentially cause turbo over speed in detriment of its life span.

I was going to post some thing along those lines but mturri beat me to it, I agree totally.

Originally Posted by mturri

Exhaust tracts are carefully designed (within all the given constraints) to give the best compromise in terms of backpressure, volume, heat dissipation, etc.

Whatever modifications are made the equivalent size x length should remain approximately constant.

Smaller pipe means higher exhaust gas velocity (less heat absortion) but greater back pressure (increased turbo lag).

Larger pipe will cause increased turbo and exhaust manifold heat retention (in other words higher EGTs) and can potentially cause turbo over speed in detriment of its life span.

I don't understand why you would end up with greater heat retention with the use of a bigger pipe.

Is it a case of greater surface area to transfer heat to? I don't see how a reduced gas speed necessarily equates to a hotter pipe or turbo. The rate at which you are able to dump heat out to the atmosphere via the gas leaving the end of the pipe I would think is determined by the pressure differential from the source out to the atmosphere and the resistance to flow by the pipe. Are we going to get more gas leaving the system by restricting the flow and therefore increasing the pressure differential??

I need a bit of help with understanding this. I can understand electrons but gas/fluid flow is not one of my strong points.

Both the larger surface contact area and the increased residence time account for greater heat exchange (loss) across the pipe. The rate at which you are able to dump heat out depends on how fast you can get it out. Its like being thrown a hot potato in your hands, the sooner you get rid of it the lesser you burn. A more proper example to cite would be an engine intercooler, as you pump more air it decreases its ability to cool because of the shortened residence time.

The amount of gas leaving the system is always the same (for a given engine running condition that is), but a smaller pipe will cause the gas to flow at a higher velocity resulting in a higher pressure differential because of the increased friction losses. Atmospheric pressure is constant, what goes up is pressure downstream of the turbine which affects turbo response (smaller pressure difference across the turbine). On the other hand if the turbo sees a higher differential across the turbine it will have less of a "hold" and tend to over spin.

Hope to have made it clearer now....