Hi Guys,

Last weekend I finally put on my frontpipe (turbo dump to main cat) and WB02.

Now when I am doing pulls for tuning I get a faint burnt fuel smell - you know the kinda smell you get at a race track?

I wouldn't NOT expect to get this smell as the exhaust should be going out the back of the car, I don't remember it happening in my old car either!

Now I have double checked all the joints (turbo dump -> FP, FP -> Cat and WB02 bung) and there are NOT any signs of exhaust leaks.

Added to this my AFR's seem to be a bit over the place, I can't seem to get it to hold 11.5!

So my question is does anyone have any ideas?

Cheers
D.

 

Possible exhaust leak?

As for the AFR's going nutz i experienced this when i stupidly left my Maf pipe kit loosely connected and the resulting air leak made tuning a real *****!

 

On the leaking exhaust during WOT pulls topic, would air get sucked into the exhaust (causing artificial lean condition) OR would exhaust gas get pushed OUT of the exhaust due to the PSI?

I would have thought the latter, thus my WB readings shouldn't be off!

hrmmm

 

No no sorry for the confusion

The exhaust leak is a possibility for the smell it should only effect idle and should not effect WOT.

As for your AFR's i was saying that in my case the MAF was on loose making my AFR's erratic. I'd tune it for one time an it would change suddenly. This caused a slight rich condition at near idle and a lean condition when going WOT.

 

tephra,

A good test to see if you have an exhaust leak before your wideband is to see what your wideband is reading at idle. If the there is a leak, your wideband will be showing a lean idle, like 16:1, 17:1, etc, depending on how big the leak is.


Eric

 

yeah ok!

so when doing WOT pulls in YOUR car you don't get a faint fuel smell? (unless of course you are covering the same ground as before, or following a dirty car!! )

Eric - yeah I was thinking that!!! I will have a look at my log NOW! :P

 

So I just took a look at a log from this morning.

30 seconds of idling, no TPS, average AFR = 14.5, max AFR = 14.8.

so that would suggest either there is no exhaust leak OR the exhaust leak is close the the front O2 sensor - ie the front O2 sensor is seeing the leak and adjusting to maintain stoich???

 

Yes, I would agree with that. I would think that you don't have an exhaust leak then.

I think you said that you replaced your O2 housing and downpipe? If that is the case, then the only place that there could possibly be a leak is at the turbo to O2 housing connection. There definitely isn't a leak beyond that, since your WB is reading stoich. If there were a leak before your front O2 sensor and the ECU is correcting it to stoich, you would probably be able to smell the extra fuel at idle being dumped into the exhaust.

 

no stock dump pipe (o2 housing)

so:

stock turbo -> stock dump pipe -> new front pipe -> stock cat -> stock catback

wb is located at the rear of the new frontpipe.

So if there was a leak at the stock dump pipe -> new front pipe connection then i suppose its possible that the air would be sucked in and the front O2 sensor could see it (as the sensor is only about 3 cm's away from this connection.

So if that was the case then the front O2 sensor would see a artificial lean condition, so it would tell the ECU to richen up the mixture. THUS the WB would see a stoich condition.

 

In my experience it doesn't work that way. If you had a leak at that position, the front O2 won't see it. The wideband will and show a lean condition at idle and low airflow conditions and less of an error at WOT conditions.

I had this exact issue years back on my Eclipse. The downpipe (what you call front pipe) to O2 housing bolts backed out, causing a leak at that connection. My wideband would show about 17:1 at idle, but correct at WOT. Once I tightened the bolts back up, everything was fine again.


Eric

 

mmm yeah it sounds weird, but the front O2 sensor is very close to that connection.

I did double checked the bolts last night and they are tight - dont want to strip them thou!

I will take it apart tonight and clean it all up, maybe put some exhaust sealer on that ring thing so there is a good seal between the down/front pipe and it and the O2 housing.

EDIT: Forgot ONE important thing - I did think of this yesterday, and thus checked my fuel trims, cruise and idle where at 0%, so there goes my theory!

 

update:

A friend has suggested that I installed the exhaust incorrectly.

I bolted up the rear end of the frontpipe (to the cat) first, this probably didn't leave enough play on the front of it.

I will redo this tonight - hopefully I wont get any more rich fueling smell

 

Mine reeks of fuel every time I lay into the throttle.
I have a 44mm exhaust "leak" at full boost tho.

I installed my dp like you did previous to the turbo installation tho and didn't have a fuel smell problem.

 

after refitting it I am still getting the fuel smell on WOT driving...

I will load up the stock fuel maps, which will be extra rich, then ill take another look for soot marks...

 

Maybe its not due to the DP. I had a pretty massive leak between my stock DP and aftermarket cat, and I never smelled anything in the cabin, even with the car sitting still at idle. And the exhaust wrap I put on my aftermarket DP before installing it would stink up the cabin when the car was sitting still, but I never smelled anything when driving around. And if you had an exhaust leak, you'd definitely be able to hear it. I couldn't see my exhaust leak, but I could definitely hear it even at idle.