Hi Guys,

As per subject?

Why do exhaust modifications require an ECU remap?

Cheers
Dave

 

air fuel ratio need to be remapped.. but for more info SEARCH

 

the reason lies in the amount of air traveling through your engine. once you free up the exhaust path the stock ecu thinks there is a problem because it is not used to seeing that much air traveling that route and throws a CEL. you would also obtain more horsepower from the tune as well ,in addition to controlling boost creep and other troblesome problems.imho i would recommend a tune with any bolt on

 

ok that makes sense, but if you didn't want to get a tune after getting an exhaust you dont need to... i mean you wouldn't get knock or lean AFR or anything would you?

 

doubt you would throw a cel unless you remove your Cat...

 

I was wondering the same thing since I'm going to be installing a downpipe and high flow cat to complete my TBE.

 

u dont have too...

but with more air flowing youll be more knock tolerant and will be able to produce a lot more power.

example, but not exact..... 30whp untuned, 40whp tuned....

 

ok what about the other way?

ie if i want to copy fq360 afr's onto my standard ix - ie no cat upgrade...

 

CEL codes with exhaust modifications usually get thrown in the case where you put in a test pipe without having some way of tricking the ECU that the cat is still there.

What you are talking about sounds more like when you put on an aftermarket intake which can confuse the ECU.

If its just a flat TBE you don't have to have your ECU tuned at all...you just won't make as much power tuned vs untuned so that comparison is however correct .

Tephra, define what you mean by "Exhuast modificaiton" do you just mean TBE (downpipe, high flow cat/test pipe + exhaust) or are you considering O2 housing and header as part of the setup as well?

 

You hit higher load cells that arent tuned properly (timing map especially) and it can actually lose power.... (happened to me).

Without a tune i lost 20whp, with a tune i gained my 20whp back, and 30hp over that.

Before my exhaust, the highest load i hit was 264, with the exhaust, my load went to 297. The timing in this area of the map was retarded (negative) compared to my advanced timing near the 260 load points.