Determining IQ for ALH after service or nozzle changes

[mk3]

I started doing some logging with VAG-USB interface and I think I may have found a better way to get my IQ adjusted for the PP520 nozzles. The standard way is to get the engine idling under nominal no-load and hammer mod or move the IQ adaptation value.
I have never changed the adaptation value and I was curious how the computer would respond. I decided to move adaptation down by 100 at the 1/2 way point on my commute.
What I found is that the G149 sensor for the quantity adjuster did not change at all before/after I mad a change of 100 to the IQ. This is not too surprising since I was driving the same car with the same load down the same freeway. The IQ increased by 2. This was true at idle as well as on the freeway.
I had made several logs during this week and it was very clear to me that this new log showed an offset in the values.
you can see it here

Furthermore, the IQ is reported as mg/str. I decided to try converting this to mpg.

I had to make one leap. It seems like the mg/str is actually mg/R. R being one revolution of the engine.
I would be awesome if someone can confirm or refute this assumption.

[EDIT - nope, it really is mg/str (mg fuel per stroke of the pump, 4 strokes per rev of the pump)]

I found a value for density of diesel fuel, and long story short, it showed 55mpg. That is probably not correct but it is way better than the 63mpg the car would have 'thought' it was doing before I changed the adaptation.
Here is a link to my calculations. I still need to fine-tune the rpm to speed but I know it is really close right now.
https://docs.google.com/spreadsheet/ccc?key=0ArHfnlbB1xu6dFhLeVhJaU9FelBHN2c0LVJrY3pEeWc
The 8mg/str that is reported at idle is very likely NOT the correct fuel consumption. Ideally I would have a way to map the IQ / Sensor reading over the entire range. I think it would help the drivability.
Next, I am going to do a similar test and monitor boost and the MAF sensor. I imaging that the engine computer is going to request different boost when I change the IQ.
I think this will be a better way to get the correct IQ reading - by logging values during typical driving conditions- calculating mpg from the IQ and RPM readings and checking them against actual mpg.
Any thoughts?
Does anyone have additional data that could feed into this? I'd love to have some data from a bone stock, well-running vehicle. I wish I had collected that before I did the nozzle change and hammer mod.

 

[mk3]

Air Mass Flow Request changes with IQ adaptation

I am continuing my tests to find the correct IQ setting by doing logs with the VAG interface.

On my last drive, I added mass air flow to the log. The results appear to show that Lowering IQ with adaptation will cause the engine computer to request - and get less air. This would explain the smoke that people sometimes get.

The voltage of the G149 Sensor would stay the same according to my theory because the fueling is the same - assuming you are travelling under a constant load.




I looked at the data a few different ways and this graph shows it the most clearly.

Next, I am going to do some logs from driveway to driveway and total up the mg of fuel consumed. I will check this against my odometer.

I think I will have to do the hammer mod again to get the values to line up.

 

[kd7iwp]

Thanks for putting this data together, this is much more empirical than what we're normally told for setting the value.

 

[mk3]

I am still working on this... just takes lots of time to go through the data.

One thing I figured out is mg/str is indeed the unit (not mg/R) for injected quantity. I got messed up in the unit conversions in the google doc but I have that fixed now.

mg/stroke is milligrams of fuel per stroke of the pump. There are two strokes of the pump for every revolution of the engine.

The pump/computer does not know the actual mg of fuel. This is determined by characterizations of the flow speed of the fuel and would depend on fuel temperature among other factors.

That is why we have trouble with smoke and engine tuning when nozzles are changed. The controls are almost completely unaware of the difference in flow.

 

[Powder Hound]

I changed my IQ for the first time last Saturday (5 May) due to an annoying slow down shudder. I fired up my VCDS after getting the car warmed up. I used a 2x4 lightly tapping the QA housing and set the IQ to 2.8. I have since noted a complete disappearance of the shudder. It had been at 1.2.

It will be 3 or 4 weeks before I have any information on fuel consumption rates.

 

[LNXGUY]

I changed my IQ for the first time last Saturday (5 May) due to an annoying slow down shudder. I fired up my VCDS after getting the car warmed up. I used a 2x4 lightly tapping the QA housing and set the IQ to 2.8. I have since noted a complete disappearance of the shudder. It had been at 1.2.

It will be 3 or 4 weeks before I have any information on fuel consumption rates.

You shouldn't have had to do anything beyond changing the value in VCDS for a increment that small...

 

[Powder Hound]

Meh - It was interesting and I wanted to do it for the experience. I did the 2-dr also - it started at 2.2. Much lighter tapping.

 

[mk3]

PowderHound, now that you have hammer-modded to an apparently better value there can be further refinement via adaptation.

I am not sure you will need refinement but you can also double-check your results by adapting backward to your old setting... at least I assume it will work that way.

I wouldn't expect your fuel economy to change in any measurable way.

Are you noticing any difference in the smoke under some conditions?

Also, I am not totally sure what slowdown shudder is. is that something people experience at parking lot speeds? or just before stopping? The main running problem I have right now is a hesitation during certain light load conditions on the freeway. Under power it runs fine as far as I can tell.

I am continuing to log engine parameters during my commutes but have not had time to go back and look at the data. Also, sometimes my laptop shuts down mid-commute - that is really annoying!

 

[ausiaslp]

i'm happy someone else is wondering the same questions than me. I'm going to link this posts in the thread:
http://forums.tdiclub.com/showthread.php?t=358468

Thank you.

 

[KLXD]

I've been wondering about the effect of IQ on mileage since I changed the seals in my pump. I got a 2-3 mpg increase that seems to have started around then. No other changes were made. Unfortunately I didn't get before and after numbers.

You want to go a certain speed and set it with your foot. There are a variety of "mixture ratios" that will provide the required power. You could overfuel and smoke or run more boost to burn less fuel more completely to achieve the same power. No?

If so then calibrating the pump by hammering or adaptation so the ECU requests more air would, it seems to me, give better mileage.

Make any sense?

 

[mk3]

...You want to go a certain speed and set it with your foot. There are a variety of "mixture ratios" that will provide the required power. You could overfuel and smoke or run more boost to burn less fuel more completely to achieve the same power. No?

If so then calibrating the pump by hammering or adaptation so the ECU requests more air would, it seems to me, give better mileage.

Make any sense?

Some sense, yes. Unfortunately without before and after numbers you'll find it hard to convince me there is a 2mpg or 3mpg overall difference but i suppose crazier things have happened. From my experience I changed nozzles and then hammer mod and never saw average mpg move by any measurable amount.

For sure running with smoke represents a low mpg situation. I think it is very likely too much boost is some kind of a waste as well. EGR flow is also an influence.

Raising the IQ reading by hammer mod or adaptation does raise the average amount of air pushed into the engine. I don't know how to find the optimal.

I have been away from logging for a while because my laptop battery kept crapping out during the trips. I have a new battery now so I could resume except...too busy and my wife is driving that car now.

 

[LNXGUY]

I wouldn't adjust a thing after a nozzle install.. Drive the car, if there's too much smoke, increase the IQ until you're happy with it. Most people see a 5% gain in mileage with just a nozzle upgrade a lone. No reason why you shouldn't either.

 

[storm.rift]

How is this coming along as i am very interested in the results and findings on this. ? thanks for the effort so far

 

[vwdieseling]

I have noticed that setting IQ using VCDS it seems to drift. I originally set mine at 2.8 and was getting shutter with stock nozzles every so often. I just recently reset to 3.2 with improvement. On my ALH if I set it any lower than 3, I get shutter. This is with stock nozzles which are .157 mg/st. I have noticed some drift over the years using VCDS versus hammer mod. I know when I was running bigger nozzles, I retarded my pump timing and lowered my IQ to see if I could get better mpg results. It seemed to work. I also advanced my pump timing and lowered my IQ, and got good results. So the data I got was not inconclusive. I was running .184 mg/st when I did this. Your graph looks interesting. From what information I have gathered for stock nozzles 3 mg/st is fine. I have been told that retarding the pump timing and increasing the IQ is whats required. I have not experimented with the pp520's. I am interested in what you find. What I have noticed is that setting IQ with VCDS it seems to drift. It seemed like any data I got had different IQ values. Also led me to believe that though the ECM doesn't recognize the change for some reason the QA will readjust. That this be coming from the MAP and engine speed sensor inputs as well as temp sensor to ECM. I would like to know what you find out.

 

[mk3]

sorry I haven't done more on this. I will try to do a follow-up soon because I am curious also how the results change with time and with climate.

I think the IQ reading we see and adjust at idle can vary. This is because it is dependent on the load being seen. If the oil is different, or ambient air temperature or humidity is different then theoretically this value of IQ seen at idle would change. Maybe it is a small change, maybe not.

I believe the instructions for hammer mod or IQ checking specify to turn off all accessories and certainly for the engine to be warmed up.

i am still very skeptical of changes in the mechanical timing. There is closed-loop feedback in this system. I think slightly advancing or retarding the pulley relative to the pump simply forces the control system to make an equal and opposite change internal to the pump. Maybe that is a bit off-topic.

 

[\/\/0J0]

Mechanically advancing the timing on the pump allows the pump to be fully advanced via software, when it needs to be. When at idle, software will retard it to be within spec.

IQ at idle should be thought of as fuel _returned_ from injectors, hence the lower number (less fuel being returned) causing the car to shudder and possibly run away, if too low. When you raise the IQ it leans out the fuel delivery. There is another Injection Quantity measuring block, further up in the number scale in VCDS, that should show actual injected quantity.

 

[storm.rift]

Possibly some interesting food for thought here.. I am trying to find best mpg.. before I had to remove the IQ pump housing to remove the fuel cut off as it was rounded and seized. I got roughly 67mpg (205 miles on £20.00 @ £1.44 per/ltr) UK gallons.. Since then I had to do hammer mod to get full adjustment back but ever since I seem to get anything from 40mpg - 47mpg which is a dramatic drop.
Im curious if the physical location of the IQ pump affects this even though the general rule is said the adaption once hammer mod still gives the same end result?? I am thinking if I hammer mod back to raise or lower iq physically and electronically adjust it makes a difference as wouldn’t this affect voltage for any given mg/s ?

Now I know its widely said that the number MG/s doesn't actually affect mpg say more than 1-2mpg, but I think I have tested enough to conclude that this adjustment is affecting my mpg widely (going from the computer and maths from fuel put in to gained miles) on a highway run, IQ set to 5 cruising at 70mph computer says 48mpg but then setting Iq to 3 computer shows 59mpg at 70mph I know this as I pulled over and changed while on a 120mile journey.

What I found so far is higher cruising speeds means lower mpg the higher the IQ so means its leaning out top end thus more engine load as insufficient fuel right so far?
and vice versa.

I am hoping this is going to be a good discussion again and see what results have been achieved with a given mg/s per mpgs. Ok each car is different but this is on a stock car with only a decat. Hoping to find an average good figure

 

[vwdieseling]

Mechanically advancing the timing on the pump allows the pump to be fully advanced via software, when it needs to be. When at idle, software will retard it to be within spec.

IQ at idle should be thought of as fuel _returned_ from injectors, hence the lower number (less fuel being returned) causing the car to shudder and possibly run away, if too low. When you raise the IQ it leans out the fuel delivery. There is another Injection Quantity measuring block, further up in the number scale in VCDS, that should show actual injected quantity.

Could you get that block number for me. I had a post with a question pertaining to this with somebody I can't remember who it was he didn't answer back. He stated what you have regarding adopted IQ and that lowering it only increased the actual IQ. I would really like to know my actual fuel injected quantity.

 

[vwdieseling]

Possibly some interesting food for thought here.. I am trying to find best mpg.. before I had to remove the IQ pump housing to remove the fuel cut off as it was rounded and seized. I got roughly 67mpg (205 miles on £20.00 @ £1.44 per/ltr) UK gallons.. Since then I had to do hammer mod to get full adjustment back but ever since I seem to get anything from 40mpg - 47mpg which is a dramatic drop.
Im curious if the physical location of the IQ pump affects this even though the general rule is said the adaption once hammer mod still gives the same end result?? I am thinking if I hammer mod back to raise or lower iq physically and electronically adjust it makes a difference as wouldn’t this affect voltage for any given mg/s ?

Now I know its widely said that the number MG/s doesn't actually affect mpg say more than 1-2mpg, but I think I have tested enough to conclude that this adjustment is affecting my mpg widely (going from the computer and maths from fuel put in to gained miles) on a highway run, IQ set to 5 cruising at 70mph computer says 48mpg but then setting Iq to 3 computer shows 59mpg at 70mph I know this as I pulled over and changed while on a 120mile journey.

What I found so far is higher cruising speeds means lower mpg the higher the IQ so means its leaning out top end thus more engine load as insufficient fuel right so far?
and vice versa.

I am hoping this is going to be a good discussion again and see what results have been achieved with a given mg/s per mpgs. Ok each car is different but this is on a stock car with only a decat. Hoping to find an average good figure

It would make sense, as far as what the ECM was receiving as far as actual sensor inputs. Then making requests to the pump to increase fuel based on the engine's crank position sensor inputs and actual MAF inputs. Not to mention ambiant temp sensor. I would assume it is in the eeprom. Since we are messing stock ECMs that haven't been reflashed for engine performance changes. Just saying we are stuck within VW's fuel MAP that the ECM is programmed for. Please let me know what you have found out.

 

[vwdieseling]

sorry I haven't done more on this. I will try to do a follow-up soon because I am curious also how the results change with time and with climate.

I think the IQ reading we see and adjust at idle can vary. This is because it is dependent on the load being seen. If the oil is different, or ambient air temperature or humidity is different then theoretically this value of IQ seen at idle would change. Maybe it is a small change, maybe not.

I believe the instructions for hammer mod or IQ checking specify to turn off all accessories and certainly for the engine to be warmed up.

i am still very skeptical of changes in the mechanical timing. There is closed-loop feedback in this system. I think slightly advancing or retarding the pulley relative to the pump simply forces the control system to make an equal and opposite change internal to the pump. Maybe that is a bit off-topic.

It seems that we are still stuck in VW's fuel MAP that is programmed or flashed into the stock ECM. I have experimented as well that is why I'm all ears on this subject. And really like to know what you come up with and any theories.

 

[storm.rift]

This is what I thought, it does seem logical but being my first diesel I'm not 100% only been on the petrol (gassers) 1.8tQ and 2 x1.8t pre and post facelift.

The problem i have is i don't know what the settings were before the IQ pump hammer mod and taking out the cut off switch, so for me knowing what it was before is a guessing game. (I was waiting for VCDS to arrive.. I know impatient but that low power bugs you into being impatient ha.)

I have read some where on here that another members tdi, likes 1.0mg physical setting and assuming they mean standard 32768 in VCDS and electronically set to 3.0mg. See i think this is interesting ground because if this is the case and the long belief is once physically set to 32768 and hammer mod to 3.0mg/s your on good ground.
Going from this information I still know I'm not getting the economy i once was and nothing else is playing devils advocate as nothing has been changed, I know this cause I wont let anyone else (garages) touch it... being as though they forget to put gearbox oil in and leave engine mount bolts lose.. another story.

I am going to try this, now I know that it's said to have a light haze at WOT now i get nothing at all so do i lower IQ by hammer mod again to give more fuel and electronically adjust so that i do get a light haze? any suggestions i would be happy to go ahead and try.

 

[storm.rift]

Can also provide logs, from which ever blocks we feel may aid this further.

 

[vwdieseling]

Can also provide logs, from which ever blocks we feel may aid this further.

My IQ on my ALH currently is set at 3.2 mg/st. I have stock injectors which are .157 mg/st. I was running .184 mg/st injectors that required me to set my IQ at 2.8 mg/st if it wasn't my engine would idle erratically and bang as though the rods were coming out the oil pan. I assumped to much fuel. I had some turbo issues which I cleared up my milage with an O1M automatic is 42 MPG which is good with an automatic. My average is 40 MPG as to date. I am trying to understand if you removed your 109 solenoid, how are you cutting flow off from your injection pump? My Beetle is above its rated average of 36 MPG combined. When I had larger injectors it was 37 MPG. I don't have logs, but used my VCDS to set IQ with no hammer mod. When advancing the pump you only increase the time the injectors recieve fuel not increase it. Your basically advanceing the quantity cam. This provides fuel sooner to the bigger injector nozzles. Then you lower the IQ to prevent the engine from receiving to much at idle. I still don't understand what you did to your injection pump. On extended highway I get about 47 MPG.

 

[storm.rift]

Sorry to clarify, I didnt remove the 109 solenoid i just replaced it as it went bad, and found there was no plunger in there but since this ive lost a load of mpg

 

[vwdieseling]

Sorry to clarify, I didnt remove the 109 solenoid i just replaced it as it went bad, and found there was no plunger in there but since this ive lost a load of mpg

How did you shut the fuel off before you replaced it? Thats interesting. I really don't think there is a way to fool the stock fuel map for better fuel milage with stock injectors, tunning boxes, chips, or reflash of ECM is required. Most refash programs, chips and tunning boxes are designed for power enhancements. You could try opening it up for more air in that way you would get better combustion of the diesel being injected. Keep the inside of the manifold clean, a good air filter. Make sure your turbo is boosting properly. One trick is a 195 F thermostat keeps the engine hotter changes the thermodynamics of the combustion process. The minus to this is summer overheating. Good maintenace is the key. It usually power or economy, a lot of sellers of performance parts tell you different. But it's always either or; I don't think there is a best of both worlds. Just a happy medium somewhere.

 

[KLXD]

The ECU cuts off the engine by setting the IQ to zero. The fuel cutoff is left over from mechanical pumps.

 

[vwdieseling]

The ECU cuts off the engine by setting the IQ to zero. The fuel cutoff is left over from mechanical pumps.

I guess your right deenergizing the ECM and pump would deenergise the QA. That would shut the pump down. The function of the N 109 is to actually close the fuel circut. Must have stammered a little after the key was turned off. Seeings how there was probably fuel left in the injection lines. Rough shut down procedure. I guess I wasn't thinking outside the box. This is a 1.9 TDI not a pump duse but yes deenrgizing the QA would work to shut the engine down. The 109 cuts off fuel to the injector lines, reduces fuel pressure to the injectors. Probably had white smoke on start up. G 80 controls commencement of injection cycle thats number three injector. N 108 that is in the pump itself does this as well.

 

[KLXD]

You're thinking backwards. Setting the IQ to zero kills the pressure to the injectors NOW. It is the primary shutoff mode. The solenoid is secondary.

The solenoid doesn't cut fuel to the lines it blocks flow from the case to the high pressure plunger.

If you disconnect the solenoid and try to start it you may find it'll hit on a cylinder or two before it gives up.

 

[vwdieseling]

You're thinking backwards. Setting the IQ to zero kills the pressure to the injectors NOW. It is the primary shutoff mode. The solenoid is secondary.

The solenoid doesn't cut fuel to the lines it blocks flow from the case to the high pressure plunger.

If you disconnect the solenoid and try to start it you may find it'll hit on a cylinder or two before it gives up.

I said I agree with that. The N 109 is secondary it cuts the flow off to the injector lines at the pump head.

 

[vwdieseling]

I have the current pump operation diagram as well as sensor inputs that control the injection event in the 1.9 and 2.0. These diagrams are from Volkswagen of America. They are the basic technician guides. I also have the MAf smoke maps and ECM fuel MAPs. I was trying to explain that there is not much in the why of economy that can be done unless the engine operational perameters are changed. This can only be done through reflashing the ECM, chips or tunning boxes. There is no way you can mechanically alter the engine for better fuel economy. You can try removing your N 109 and fabricating a plug in the hole. I just don't think it would be good for the engine as far as start ups or shut downs. I have seen bad plungers in N 109s always results in smoke issues and horrible shut downs.