2G Upgrading the exhaust (Pros/Cons) Custom

[DSM_15_2G]

Hey everyone,


I'm starting the new thread because I didn't find anything similar to my state. Basically I own a 99' Mitsubishi Eclipse GS (European 4g63 7 bolt).
I plan on turboing the car this month or the next (depending when I gather all the parts needed).
I've planned on going all stock : T25, 450cc injectors, 95GSX Eprom ECU (no ecmlink), smic, r34 skyline bov and all that good stock stuff. Of course all the gaskets are new, exhaust mani is the stock 4 ply copper one.


Now, when I bought the car it was all stock except it had a 3inch cat back exhaust with the catalytic converter on it. The car had great mpg, no smoking, no smells, it was kinda on the drony side on highways .. After a few months I wanted to remove the catalytic converter to see if theres any improvements. On my surprise, the car lost 10% of the gas pedal response, it started smoking, smelling of gas and having a shitty mpg, more like 5-8 mpg smh

I went and put the catalytic converter back and everything went back to normal.

At this point I've sent my car to the shop to have all the maintenance done. Valve seals, any oil leaks, new clutch, new oem coilpack, wires, plugs, cas, crank sensor, revised lifters, new o2 sensors, suspension all around etc.... And I've sent them a stock exhaust from my 2.4 97 Spyder dsm.

They've installed the stock exhaust and removed the catalytic converter.. As I drove the car home, 150 miles, I could notice a bit lower mpg than normal but I thought it was fine...

Two months later my country stated some new law about catalytic converters so I went to the exhaust shop to weld It back on... No smoke any more but the car had shitty mpg again and it would sound weird on idle


I went back and took it off again

And now ever since I've been driving it now, the mpg is less than normal should be, it smokes when cold (like above) and smells of unburnt fuel like a mf, even my oil smells of gas

Now the main question is...

When I turbo the car, I am basically changing everything, ecu, injectors and everything.. I have an option of getting a 2.7 from turbo to the back custom made exhaust from my friend which has a catalytic converter on but its empty (just for the looks/inspection/police). Or should I buy a stock downpipe and bolt my old 3 inch catback and use my catalytic converter...

Now just a note.. On Euro DSMS, front O2 sensor is right before the converter on the exhaust (2-3 inches away), the rear O2 is also on the other side of the converer (2-3 inches away)

It all goes around that exhaust and the catalytic converter...


I'm sorry for the long message, just wanting someone who tries to help understand my issue

 

[1DSM2019]

First I want to say sorry, if my english is not so good, I'm from Germany.

As I understood, you drive an European dsm. So, I don't know if it rules for the 2g / d30 too, but my euro 1g /d22a has higher compression than us models. It's 2.0 l 4g63 no turbo with 10.4:1 and 150 hp. The US model was 9.1:1 and 136hp.

So if it's the same at the 2g, and you also got on your euro model a compression of 10.4:1, then you shouldn't get a turbo. The compression is too much for turbo. I can't really explain it, but I read it a few times.
I think if you do it, you should go lower with the psi from the turbo (don't know the English word for "ladedruck") or it may damage your engine.

And about your question: the o2 sensors compare the results and if there's no cat, they might try to adjust the fuel amount, the engine gets. Had such a problem with my vw polo last year, when there was a hole in the exhaust between engine and cat.

I think you should get a 100/200 cells metal cat (not ceramic). They might be much more expensive, but metal cats have a much higher flow. So you won't have the cat as a obstacle + you get better results at the o2 sensors. Then it probably work.

No guarantee, if anyone thinks I'm false, please correct it.
If something isn't understandable, just ask, I'm going to try to describe it better.