evo4 2.5" or 3" exhaust?

[meka]

I just picked up a Monster Sport front pipe for my evo 4. I plan on building aluminum straight pipe all the way back from that.
The downpipe measures 2.5" ID
There will be no cat and there is no plan for a muffler unless the sound is irritating.
What differences will I see between using 2.5" or 3" pipe?

Other mods are evo8 HKS RS intake, Greddy LS Intercooler, cop ignition, BlitzID EBC at 16psi.
I'm still on stock E4 turbo, ecu and injectors. I'm hoping I'll still be ok on stock maps with the full exhaust.
thanks

 

[D1andonlyantman]

With that list of mods id say you definitely want a remap. Maybe the air/fuel ratios will still be safe without a remap (I'm really not sure),but there will be plenty of power to be gained just by getting the car running as it should. Because you've got an intake and decat the engine will breath a lot better and you would want to get the fuelling corrected even if you told the tuner not to push the car too hard

In relation to the exhaust question, 3" is what most people go for. The idea with an exhaust is to have it large enough so that the gasses can flow properly without being restricted, but not so large the gasses lose all their speed. It's all to do with something called the scavenger affect and how the gasses flow. I'm not sure at what power level your exhaust would become a restriction, all I know is most people opt for 3"

I hope that's some help mate, and if I'm wrong on any of that I hope anyone feels free to correct me

 

[meka]

Yes remap is in the plan. I have E8 injectors waiting but haven't got a 5 or 8 ecu yet. I'm hoping to get an E5 ecu with the "Ralliart" map on it already. We don't have many tuners here that have experience with Evo's 1-9.

thanks for the tips, I believe if I just go with 3" I'll have no reason in future to have done 2.5"

 

[D1andonlyantman]

Check out these guys if there aren't any decent tuners near you. Mapping will make or break the car and you want it done properly, specific to your setup, and I've heard nothing but good things about these guys and they do it all remotely

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