Fault codes in relation to WMI

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S.Pellegrino

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Good Afternoon chaps,

My car is your standard A3 1.8T Stage 2. Running FBO (exhaust, intake, intercooler) with minor deletes (PCV, N249 etc.) running AEM WMI. Car peaks at 21 psi (1.5 bar) and holds 17 psi (1.2 bar) to redline. Running AEM V2 nozzle. Start spray at 5 psi and full spray 20psi.

I've been having trouble with a Pre-cat o2 sensor code. 17511 (see pic below)
8kRQIYY.png

I am running 50/50 water meth mix. (bought a barrel of 25L 99.8 pure methanol and dilute it using a weight scale with distilled water)

The code starting popped up first a couple weeks ago. Cleared it and kept coming back. I replaced the o2 sensor for peace of mind however code keeps on coming back. So I did some trouble shooting.
I did a 100 mile (160km) drive over 2 days with the WMI off. The 100 mile drive did not triggle the 17511 fault code. I do a 30 mile (50km) drive with the WMI on and the fault code appears. The 30 mile drive would be doing a pull of 4.5krpm when joining the motorway and letting the WMI system go on full spray.

So with WMI the code appears but when driving without WMI the code disappears. Also, I never had this code pop-up BEFORE I installed my WMI system. Code does not trigger a CEL and there are no other accompanying codes.

I think it's safe to say that the WMI is triggering this code. What can I do? I replaced the o2 sensor with a genuine Bosch wideband one. Should I worry about this code?

Any input is greatly appreciated,
Cheers,
S.Pellegrino
 
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Cars been mapped to run WMI?

Also measure by volume and not weight


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Might be a factor for the fault code, if the car is getting more “fuel” than what it’s expecting. Just a thought

Without the car being mapped for it you won’t see any of the benefits really.


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I am more for the cooling aspect. Car runs really hot without the water/meth. I also didn't tune it for WMI as the stock A3 injectors (non S3 so they're not the 386cc) are nearly maxxed out and I wouldn't be able to pass MOT without WMI installed.

I may try and narrow it down and run purely distilled water. See what happens. I'll also talk to my tuner.

More input is appreciated!
 
Genuine 02 sensor used or aftermarket?


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Oh yeah, missed that bit. Obvious question again, you’ve checked the cables, etc.

Granted the water/meth would lower EGT’s but it “shouldn’t” really effect the actual heater element in the sensor which is why that fault has popped up.

That said, little research online suggests a couple people are noticing the same faults due to using water/meth without mapping it in. Perhaps coincidence.....


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I'd say if it's not mapped in for meth then that will be ur problem but I'd speak to your mapper and see what he says. Also as @S3AMJ said measure ur meth by volume not weight.
 
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The ECU doesn't 'need' to be mapped for WMI.... WMI will lower IAT's and subsequently EGT's... it also acts as an octane booster to a degree but obviously largely dependant on how much mix you are squirting in.... on an OE ECU wideband will deal with this mixture change fairly well... on a standalone like IECU using speed density then you would need to use the relevant additional maps that will cater for WMI increasing the the overall volume of combustable material (that would lead to a richer mixture and subsequently fuel trims working a bit harder to keep it under control)

Starting at 5psi seems a little low to me tbh as there probably isn't much load required to generate that level of boost and AFR may well be quite lean compared to what it would be under a heavy/full load condition...

I would be tempted to raise this to about 1bar minimum and see if the issue persists but generally speaking WMI would not cause the fault you are seeing unless due to it being set so low (5psi) its preventing the Lambda heater from reaching the expected temp in the expected time due to the WMI 'cooling' the combustion process too much too soon

I would start your controller to kick in from 12-14pi rather than 5psi....

<tuffty/>
 
<tuffty/> said:
The ECU doesn't 'need' to be mapped for WMI.... WMI will lower IAT's and subsequently EGT's... it also acts as an octane booster to a degree but obviously largely dependant on how much mix you are squirting in.... on an OE ECU wideband will deal with this mixture change fairly well... on a standalone like IECU using speed density then you would need to use the relevant additional maps that will cater for WMI increasing the the overall volume of combustable material (that would lead to a richer mixture and subsequently fuel trims working a bit harder to keep it under control)

Starting at 5psi seems a little low to me tbh as there probably isn't much load required to generate that level of boost and AFR may well be quite lean compared to what it would be under a heavy/full load condition...

I would be tempted to raise this to about 1bar minimum and see if the issue persists but generally speaking WMI would not cause the fault you are seeing unless due to it being set so low (5psi) its preventing the Lambda heater from reaching the expected temp in the expected time due to the WMI 'cooling' the combustion process too much too soon

I would start your controller to kick in from 12-14pi rather than 5psi....

<tuffty/>
Click to expand...

Reason for start spray at 5 psi is following the AEM manual. It's what AEM recommends. For start spray they recommend at 25 percent of max boost and full spray at max boost. So which would equal to 5 psi for start and 20 psi for full spray for a Stage 2 KO3s.

I will set the controller to start spray at 12psi rather than 5psi. See if that will make a difference. More troubleshooting and diagnosing will commence tomorrow!

hydro s3 said:
I'd say if it's not mapped in for meth then that will be ur problem but I'd speak to your mapper and see what he says. Also as @S3AMJ said measure ur meth by volume not weight.
Click to expand...

Definitely, The guys over at VWVortex also told me dilute and mix by volume rather than using a weight scale.

I read from a couple of forums that (as you mentioned) the methanol is lighter than water so to get an accurate reading you would measure using a weight scale. I suppose using a hydrometer to get really accurate readings would be the way.

I like to read from a variety of different forums for answers (Ford forums, RX7 forums, V8 forums, Corvette forums etc.)
 
Updates people! Updates Righty-ho!

Yesterday, 06/05. On the AEM controller, Start spray at 5 psi and Full spray 17.5 psi. Didn't expect much. After 50 mile drive over the course of 8 hours, 17511 code came back. Brilliant!

Today, 07/05. On the AEM controller, Start spray at 11 psi (the highest it would go lol) and Full spray 17.5 psi. After the 50 mile drive over the course of 8 hours again, the 17511 code did NOT come back.

So I think we can deduce that the higher set Start Spray does play a role in the 17511 code popping up. Now, what is recommended next? Lowering the start spray PSI slowly by 1 PSI each time to see if the 17511 code comes back?

I did not change the mixture of water/meth. The reservoir was still filled from the last time.

By the way, would driving with a 17511 code constantly popping up be damaging to the o2 sensor and engine?? I assume so no?
 
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So Tuffty was bang on! Very interesting.... as the pre-cat 02 sensor is there to aid with fuel trims, I personally wouldn’t want to keep running the car with it not working correctly.


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Well, F**k me. The code has come back! lmfao. I think that on Friday the 7th I did not inject enough water/meth into the car.

So yesterday, 08/05, I set the start spray to 10 PSI and full spray to 17.5 PSI. The code came back.

Today, 80 mile drive, I set the start spray to 11 PSI and full spray to 17.5 PSI. I also mixed a proper 50/50 Water meth mix by volume. Code came back.

I am starting to think that the amount of methanol has something to do with it. I will try running only distilled water in the system tomorrow. See if the code pops up.

Is it recommended to put the full spray to 20 psi? As to not hydrolock the engine? Or will the water just vaporize anyways?
 
Doubt that’s your problem chap.... I ran 80% methanol with no issues to my lambda.

You had an issue with your lambda before, you changed it for a new one and it’s the same, perhaps check your wiring, plugs, etc.

You’ve done what Tuffty suggested by increasing the PSi to start at 12. It stopped initially but it’s still happening......

Your using it purely to help with EGT’s then only using it when your EGT’s are going to be high, which is as Tuffty said from 12psi onwards.

Why are you so keen on requesting it to come in sooner?


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S3AMJ said:
Doubt that’s your problem chap.... I ran 80% methanol with no issues to my lambda.
Click to expand...

Exactly my thought, How come you're able to run 80/20 mix yet I get a code. Major difference is you're (I'm assuming) tuned for WMI

S3AMJ said:
Why are you so keen on requesting it to come in sooner?
Click to expand...

Reason for setting the start spray to 10 psi yesterday was to see if the delay in injecting the mix into the car was the cause of the 17511 code not appearing.
 
S.Pellegrino said:
Exactly my thought, How come you're able to run 80/20 mix yet I get a code. Major difference is you're (I'm assuming) tuned for WMI



Reason for setting the start spray to 10 psi yesterday was to see if the delay in injecting the mix into the car was the cause of the 17511 code not appearing.
Click to expand...

Yeah my Ignitron Ecu will make adaptions to the fuel trim when it recognises the additional fuel, but that said my lambda is no different to yours, the heater element in mine does what it should. The water/meth will of course be coming in when it should as well.

If the car is happy with it coming in at 12psi then it’s probably best leaving it there isn’t it? Code only came back when you changed it to sooner yeah?


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"tuning" for WMI is simply a case of adding timing advance and or increasing boost to take advantage of the inherent knock prevention that WMI affords...

I would say your problem is still Lambda related and it may just be a lazy heater that under "normal' circumstances heats up more slowly than normal but still is within the allowed timescale of the fault maps...

Having dealt with more cars than I can shake a stick at of varying levels of tune that have WMI fitted this would be the first time I have seen this particular fault appear under the circumstances you state...

Lambda blocks are listed in the link above... I would be logging relevant ones in those to see what the affect WMI is having on the lambda and AFR

<tuffty/>
 
S3AMJ said:
If the car is happy with it coming in at 12psi then it’s probably best leaving it there isn’t it? Code only came back when you changed it to sooner yeah?
Click to expand...

No, 11 psi. 11 psi is the max the AEM controller goes to. Friday, 07/05, I had it set at 11 psi (as stated above). I think the code didn't pop up as I wasn't ragging the car enough. Didn't use a lot of the methanol mix in the reservoir that day.

Yesterday I set start to 10 psi and code came back. Today I set start to 11 psi and code came back.

<tuffty/> said:
I would say your problem is still Lambda related and it may just be a lazy heater that under "normal' circumstances heats up more slowly than normal but still is within the allowed timescale of the fault maps...
Click to expand...
Lol, garbage genuine Bosch sensors. I am kind of stumped at this point to be honest. @Tuffty what would be effects of driving with the 17511 code? Disastrous in the long run? Could I potentially damage something?

@S3AMJ mentioned the fuel trims the pre-cat o2 sensor is responsible for. Quite vital
 
The heaters main job is to get the sensor up to temp quickly as it needs to be hot to actually work as a sensor... the fault code is a result of it not reaching temp as quickly as expected... generally speaking this is typically down to a faulty lambda but... it could also be down to bad wiring so increased resistance from corrosion or something...

As long as the lambda is actually up to temp then the ongoing effect should be minimal but if its not hitting temps then it could effect fuel economy etc...

Not really sure what else to suggest other than check the wiring... I still think that the WMI is a red herring... the fault IMO is with the lambda and the WMI is just highlighting it... a richer mixture will 'cool' the exhaust gasses which is why when tuning for turbo's you run richer to keep EGT's in check but not too rich as it will actually kill turbine speed and as a result boost

<tuffty/>
 
audi upgrades
Updates! More updates! We all love updates, who doesn't?

So, Monday the 10th. Was pouring the whole day so decided to to use the day off (I don't work when it rains) to check the wiring as @<tuffty/> mentioned. Removed the corrugated hose running from underneath the car through the rear of the engine bay to the scuttle panel where the ECU is sitting. The corrugated hose just crumbled apart in my hands. No chaffing, All wiring in good condition considering its age. So I wrapped it in new corrugated hose and cleaned the plugs with CRC dedicated contact cleaner.

Tuesday 11/05. Sunny, ready for the daily commute of 50 miles. Set start spray to 11 psi and full spray to 20 psi. In the reservoir I filled it up halfway with distilled water. There was still a tad bit left of 50/50 WMI mix so I'd say there were some traces of WMI left. Around a 90/10 mix or something. Maybe even 95/5. Boosted the car, allowing the system to spray for some time revving her up all the way to 5k.
LOW AND BEHOLD, the code doesn't come back!

Today, Wednesday 12/05. Same as yesterday, tuesday. Set spray to 11 psi and full spray to 17.5 psi. Code does not come back.

Still running AEM's 500cc nozzle as their nozzle sizing chart recommends.

I think we can deduce that the methanol is the one causing the 17511 code to pop-up. Richer fuel mix thanks to the WMI causing it?
 
Your running a 500cc nozzle with a 90/10 water to methanol mix?!??

I had a 250cc nozzle post Intercooler and 4 x 75cc nozzles with my system running 80% methanol. Which is 550cc in total.

I understand it you should use smaller for a more water % mix and larger for a more methanol % mix.


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Interesting, that’s the first I’ve seen of this.

Suggests where I’m going to be going power wise with my build I’ll need 1432cc in total!

This WHP or crank? ****** yanks

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S3AMJ said:
Suggests where I’m going to be going power wise with my build I’ll need 1432cc in total!
Click to expand...

Like you said in the other thread ''IM NEEDING ALL THE METH'' lol

This chart is also in my AEM manual for the WMI kit. Did Badger5 install those nozzles for you? I haven't followed your build thread the whole way, info is probably buried somewhere in there @S3AMJ
 
S.Pellegrino said:
Like you said in the other thread ''IM NEEDING ALL THE METH'' lol

This chart is also in my AEM manual for the WMI kit. Did Badger5 install those nozzles for you? I haven't followed your build thread the whole way, info is probably buried somewhere in there @S3AMJ
Click to expand...

Badger5 installed the original AEM kit way back when, but my car has gone on from there over time and more nozzles have been added since.

The recommendations I received were from Bruce who is the owner of “Coolingmist” a company over here in the UK. That said we saw no gains at all from the direct port injection nozzles I had fitted, makes me wonder if the “spec’d” 75cc nozzles were actually big enough.......

Based of AEM’s recommendations I should be looking at having 270cc nozzles in my inlet manifold and a 440cc post Intercooler. Totals out at 1520cc which will rinse my 3 gallon tank for sure that’s based on a car running 25+ PSi boost and around 650-700bhp.

Something i’m prepared to consider changing on this basis!


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I'm not sure what size of nozzle Bill used from the aem meth kit but the other one I got from Bruce at coolingmistuk is a cm1 85cc @200psi nozzle.
For using one nozzle 500cc seems large (not that I'm a expert) especially if ur at 240whp.
Maybe try emailing Bruce at coolingmistuk and see what help he can give you as he was very helpful when I was talking to him.
 
Update, tried a blend of 30 percent meth and 70 percent water. start spray 8 psi and full spray 17.5 psi

Code did not come back.

Went for a mountain drive this morning, pushing the car to 6k rpm. Used around the whole reservoir of methanol in 50kms lol.
 
hydro s3 said:
I'm not sure what size of nozzle Bill used from the aem meth kit but the other one I got from Bruce at coolingmistuk is a cm1 85cc @200psi nozzle.
For using one nozzle 500cc seems large (not that I'm a expert) especially if ur at 240whp.
Maybe try emailing Bruce at coolingmistuk and see what help he can give you as he was very helpful when I was talking to him.
Click to expand...
AEM Smallest one. Start spray 10-12psi on mapped car else rinse the meth for no actual benefit
 
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