Replacing exhaust like for like but different brand - remap needed?
 

I am replacing the 3” decat Milltek on my ’05 JDM with a 3” decat RCM system.

I wouldn’t mind getting a map tweak, but my mapper isn’t returning calls. Rather than pay for a full remap from scratch, could I get away without a remap or is this asking for trouble?

if its mapped for a decat already i dont see there being a problem .

Get it on a dyno to check afr's straight away as a double check in case flow is different, but shouldn't need a map change. Better to check and it be fine than not check and it det a piston out

I personally wouldn't waste my time and money if it's already been mapped for de-cat,

I doubt that even with

3" decat with resonator and backbox

vs

3" decat with nothing no res or back box (RCM team ice style)

That the flow change wouldnt be enough to "det a piston out" unless map was pretty pee poor to begin with....

If your that fussy about AFR's then id recommend you invest in a wideband instead of paying for a dyno run every time you make the slightest change.

If you start getting boost spikes etc. then obviously something needs addressed tho...

Thanks all for the replies so far...sounding very encouraging

if you want to risk it then its your choice, i wouldn't.

I'll definitely get it checked. My specialist does mapping as well as mechanical work and I'll get him to fit the exhaust and check the readings. However he wasn't the original mapper so would need to start all over again if it needs tweaking.

If you really worry that it's a "risk" then buy a wideband and put your mind at ease, this is far more likely to save your engine (if you know what it should/ shouldn't read) than paying for a one off dyno run to check your AFR after an exhaust switch.

Even better idea would be to fit one, collect real data and report back to show others that there is / or isn't anything to worry about, :thumb:

I've got syvecs so it will pull timing anyway.

But it's a risk, if it does change the flow then it can affect it, even you'll admit that.

No its not a risk at all.

and i wouldnt think that the flow could ever change enough from what is essentially just a cat back exhaust switch from one 3 inch setup to another.

Certainly not enough to det to death.

Unless as i says the map was poor to begin with.

well you carry on with what you think then.

I do think ur syvecs is a great piece of kit tho. :)

its a subaru not a f1 car, people have asked the same question after a plug change :rolleyes:

I remember when I went from the cobra 3" track day friendly system to the jetex/ revolution system and you could feel it flowed/ drove slightly different even though it was 3". Had to get it tweaked. I'd rather know it was right

The fact there isn't a consensus on this thread, and nor is there is a definitive answer to be found elsewhere versus numerous threads suggesting that a remap is advisable following an exhaust change, amply demonstrates that it's a valid question.

i was only joking, lol to be fair i will confess to noticing a very slight difference when changing the centre pipe to a non res, afr's never changed though and i did have them checked

No need for a full remap unless you're feeling flush but an AFR check is defo the way to go for peace of mind. I've done an exhaust swap without a remap and no afr check car was fine but that was at my risk.

The slight issue I have is that (I believe) that even a small tweak requires me to return to my original mapper who's too busy to take my calls. Unless my (non Ecutek licenced) mapper is able to adjust someone else's Ecutek base map...

If u buy ecu edit admin edition you can bypass the ecutek lock on the older 16bit ecu.

This will allow you to edit the map thats on the car no matter who did it.

Good call - much appreciated.

Just make sure it works with your JDM ecu before forking out for it,

I know i cannot hack through the racerom ecutek thats on the later hawks with DBW

Spoke with my guy and he should be able to do it. JDM does not have DBW and cannot run Racerom

ECUedit Admin is not free tho and will cost around £250-300

It does have a good log viewer and SSM functionality.