OFT Data Logging and Exhaust Leak

[alexand3r]

Hey all,

If anyone is curious as to what happens to your car when you get an exhaust leak, take a look at my logs.

The first one here shows a 3rd gear pull WITH the exhaust leak at the Header/Head junction (Replace your gaskets, even if they look great). If you select Throttle, AFR and LTFT in the view options and turn everything else off, you can see that the car is dumping in a bunch of extra fuel from the extra air it's receiving from the leak or perhaps the exhaust fumes escaping out of the leak (probably the latter based on looking at the Header flange):

E85 - Leak

Actually, after this log and before I fixed the problem, the LTFT got as high as +8%... I could really smell that sweet, sweet corn juice.


After the leak is fixed, by selecting the same parameters, you can see that the car is much more stable through 2nd, 3rd and 4th gears:

E85 - Leak FIXED

Those blips you see in LTFT and AFR is the car changing gears (it's an automatic, but probably looks similar to a manual being flatfoot shifted), but you can definitely see how much of a difference a leak can make. Hopefully this helps someone out there.

A quick shout out to Shiv and Robert. Their customer service skills are top notch and the tunes are excellent.

Now for some header pr0n. You can see where the leak was on the driver's side flange:

[Shiv@Openflash]

Glad you got that sorted. With the next map release we are going to re-enable the diagnostic fault codes for o2 sensor rich/lean. Because those codes occur when you have an exhaust leak. We learned this ourselves after replacing gaskets. Once replaced, those codes never came back on our car. So all this time, we were simply masking an issue. For those OFT who want to see if this applies to them, simply re-enable those o2 sensor diagnostics and see if you trigger those code(s). If you do, definitely replace your header gaskets (there are 3 of them).

Cheers,
shiv

[jamesm]

that's also an excellent example of what ltft's in the 40g/s bucket do to open loop afr's. it's weird how it's not across the board. i wouldn't expect the ltft to rise and fall once it's in open loop.

[alexand3r]

Yes, I would assume it's due to the fact that I reflashed after the repair (However, it did have ~30 miles and a few restarts on it before logged). I expect that the LTFT value will rise a bit once the car has some more miles on it though.

That being said, when I first flashed E85 with the leak, the logs looked very similar to the one posted (~11.5 AFR and positive LTFT).

Originally Posted by jamesm

that's also an excellent example of what ltft's in the 40g/s bucket do to open loop afr's. it's weird how it's not across the board. i wouldn't expect the ltft to rise and fall once it's in open loop.

[alexand3r]

Update:

Here in Phoenix, AZ the morning temperatures have been in the upper 40s when I start my car in the morning. I had very rough, sputtering starts before I fixed this exhaust leak. Since fixing the leak, my car starts up like normal - no sputtering at all!

Also I've put about 110 miles on the car and numerous restarts since fixing the leak. Data logging shows my AFR@~12.5 and my LTFT are rock solid @ 0.00 when pulling at WOT.

@shiv@vishnu - Are you sure you didn't steal my car and dyno tune it while I was sleeping one night?

[Hu_Go]

Hi everybody,

Sorry to aks in an old post, but I'm curious.

I just log some pulls to try to see if I have a leak and I got a negative LFT.

On the data of alexandre3, LFT was Positiv with the leak and at 0 without leak.

https://datazap.me/u/hugo/log-156478...=0&data=2-9-11
Is someone can tell me if it's normal?

https://datazap.me/u/hugo/log-156478...&data=1-2-9-11

Thanks Guys.

[tomm.brz]

shouldn t be a leak, but you definitely want to pull some timing in your base timing B map since you have important corrections after 6k rpm