Hi all,

I have just changed the exhaust on my WRX from an RS Racing to a HKS Hyper Muffler. I am impressed with the sound and looks but am not impressed with low to mid range power/torque. I thought the Hiper Muffler was one of the freeist flowing exhausts out there and it certainly seems to take the straightest route possible from the downpipe back and so was expecting it to perform better than the RS one. My car does seem run a little more boost now at the top of the rev range but even so it feels a bit slower overall.

It seems that most of the high power cars on dynonet are running with hiper mufflers, this must be for a reason.

I have an APexi Power FC, could I need a remap to take full advantage of the mods (I have also had a downipe fitted since it was last setup ?)

Can anyone provide a bit of insight into how exhausts can affect power delivery as I presumed the more you flow the better it is.

THanks

 

If you have replaced the entire exhaust from the turbo back the car will very likely need a bit more fuel in places. IIRC, the apexi thing is a piggy back interceptor unit that runs over the jecs, so the car should be adjusting a bit via MAF, but you really ought to get the apexi "map" checked out.

I know that just changing my centre section from a PE T75 cat pipe to a magnex 2.5" centre section made a significant enough difference to require a bit more fuel through the midrange. The extra fuel made quite a difference , once I finally managed to persuade the mapping outfit that it was worth looking at the fuelling.

 

Moray,

that 'mapping' outfit sounds like one I used to use

No remap required after fitting a decat downpipe and porting the headers...

 

Thanks for that MorayMackenzie

The Apexi unit I have is a complete replacement ECU and uses all the standard sensors on the car.

The other thing I have noticed is that the car is detting with less boost than it used to, in the Apexi power fc manual it says that it won't retard the ignition when detting occurs but it flashes the engine check light whereas the standard ECU would make some alterations, ie drop boost and retard ignition. Maybe the ecu is holding on to settings that aren't as suitable for the car now that it has had the exhaust mods because with it being a prgrammable ecu it is expecting the person who does the mapping to get it right and adjust when other mods have been made.

I am thinking along the right lines anyone ?

I have other mods planned before I go for a remap anyway.

In general, am I right in thinking that if the Hiper Muffler is more freer flowing that it should make the car perform better.

Cheers

 

hi ya mate still doesnt sound as nice as mine

 

Hi Guys,

Whilst we're on this subject I posed the question to SS that if I was to fit a Decat DP would it run leaner at any point in the rev range. SS said that the MAF would do all the work in terms of adding extra fuel. So, now I'm confused, cos it seems that you guys say a remap is needed...?

What do you think is it completey necessary for a remap or will it just make the most of the new system. I mean if it doesn't run any more lean than it did and gives better torque power than it did I'd be happy, even if the remap scenario does make the absolute most (more than just the MAF can do) put of the new system and give that bit more across the rev range..

Alex