Hello dear Evo Owners,


Been searching around the forum to see if anyones experiencing the same issue
Bought the car new and is a '14 GSR w TC-SST. now with about 23k Miles. I have recently noticed that the car has a lean spike on the AFR during idle. It reads over 16 for a few seconds before going back to 14.7. This happened after I made changes to my muffler section of the exhaust. (WOT AFR reading is healthy at 11.1 - 11.4 and avg idle at 14.6-14.7)

The car initially was using the HKS Super Turbo Muffler, but now the muffler section has been removed and changed to a custom twin outlet with 2 resonators. The lean spike seldom occurs, so far it has only happened twice since the last 2 weeks the muffler has been removed. Is it possible the car lean spiked cuz of the increase flow due to the removal of the muffler?

My car was already tuned before with these mods:

HKS Super Turbo Muffler
HKS Racing Suction Kit Reloaded
HKS EVC IR 6 IR 2.4 EBC
HKS SSQV BOV
Tomei Test Pipe
PLX Wideband
Prosport Boost Gauge


Post Tune mods:

HKS Hipermax 4GT
Tomei Widemouth DP
Blitz SE FMIC
Muffler Delete (Twin resonated outlet)

I browsed the forum and the web and some have mentioned that altering catbacks will not interfere the existing tune. Based in south east asia, where we have summer season all year.

I hope I can get help with this.

Thanks!

 

A drastic change like that is definitely not the result of a muffler change. Hell, you could completely remove the catback and it won't make that kind of difference.

Are you able to data log? I'd log a few cruising runs and a few WOT runs just to make sure there isn't a spike that you aren't able to see on the gauge. Theres a few things it could be, Wideband issue, injectors, pump, clogged return line, and although your car has a newer fuel relay (I believe?) I would just go ahead and replace that just to be safe.

 

Take off that BOV put the stock one back on and see if you have any issues. You don't need the BOV unless you have a massive turbo, so remove that problem imo and see how it runs then.

 

If anything that BOV would only cause it to run slightly rich between shifts wouldn't it?

 

Anytime I see weird behavior and see aftermarket BOV when one isn't required, it's the first thing I recommend taking off and putting back to stock lol. They can be mis-adjusted or mis-installed so many different ways imo.

 

If you're seeing a lean spike at idle it is more than likely a slight misfire - 02 sensors are not designed to read raw fuel. Cam timing at idle can also affect this - possible that the DP and larger intercooler are kind of playing with the settings a little bit.

I wouldn't put too much worry into it as long as the AFRs are still stable when it really counts.


-ash

 

Hey thanks jakgal04.

Yeah thought it was unusual for the back part of the exhaust to cause any interference w the wideband readings. I am not able to data log the car at the moment, prolly get it logged this weekend the soonest. will update if theres any loggings i can share. At WOT the car is healthy. Ive seen other owners having idle afrs exceeding spiked 16 and not having any issues.

 

Thanks for the heads up man.

I'll get a check on my BOV, though its very unlikely for it to be the main culprit cuz the car was tuned with it and have been running golden for a year now. the spike started to happen after the muffler delete mod.

 

Thats what I thought too. The combo of the DP and intercooler might cause the spike since ive installed it post tune. Not to mention the current hot climate were experiencing now.

And yes considering the AFR readings usually stabilize itself I shouldnt be too worried. Ive seen others having a more leaner spike reading and their car runs great. Luckily my tuner will be around this month, might be the best time to have the car checked. For the time being, i'll monitor the car some more and see if there are any changes. Thanks Ash.