injector upgrade / IQ question

In theory, one should be able to upgrade injectors and not do a thing to the IQ. Is this the "ideal" way? I keep reading about how everyone is changing the IQ when they do their injectors, whether to adjust smoke, starting issues, or whatever. I personally don't care about smoke so that wouldn't be an issue for me. Is the reason for adjusting the IQ just a happy medium between smoke and power?

It's the chip and injector combo that makes too much smoke most of the time. I haven't heard of too much smoke using only one mod. But, adjusting the IQ to reduce the smoking is at the cost of some power. My Jetta with chip and inj and IQ of 4.5 or so was a bat out of hell fast (for a diesel), but too much smoke for me. I'm now sitting at 8.5. There is some power loss, but the smoke is really reduced. If you're comfortable with lots of smoke, then leave the IQ alone. I would suspect it would smoke more than you imagine and you will want to adjust your IQ. Smoke didn't bother me since I drive a power stroke truck, but found the smoke from both mods, inj and chip, made it worse than my hopped up F350 truck. Its up to you what you think is too much smoke or not. If it's too much get a VAGCOM or find a friend and raise the IQ (lower the fueling) and you're on you way, simple as that. If you like the smoke, leave it as is. I fiddled around with my IQ till I was satisfied with the balance of power and smoke. With your "show" mods, I would guess you hang with the import crowd. Just a guess, but you might be embarrassed by the high levels of soot, especially when you cruse at nighttime when the following car's headlights REALLY make the smoke visible. I'd like to see a pic of your car if you can post, sound sweet.

I found no difference in 1/4 mile times and MPH over several runs between "rich" and "lean" settings both in Vag-Com and hammer mod, but a big diff in smoke.

hammer mod helps a LOT with the smoke, no change in power according to the 1/4 mile dyno.

I could be placebo effect on my part for hp. Less smoke, now that is a fact. I need to run some HP and 1/4 mile times.

Thanks. That is what I figured. I will just have to see how much smoke I will have when I install the PP.205s. Any word Kerma on the new shipment?

I found no difference in 1/4 mile times and MPH over several runs between "rich" and "lean" settings both in Vag-Com and hammer mod, but a big diff in smoke.

hammer mod helps a LOT with the smoke, no change in power according to the 1/4 mile dyno.

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My setup is almost identical to yours (Auto -11mm, Upsolute, PP520s... Have dawes, haven't installed it yet)...
Just curious, what is your current IQ setting. Just curious as to what range I should target. I'm still quite sooty at 6.5.
Thanks

What intervals do you use when adjusting IQ?

For instance, if you are at 6.5 and see too much smoke, do you try adjusting up to 7.5 or go up a little, such as 6.7?

Thanks.

Kerma,

Are you saying that in your dyno runs you found no
difference in power between high and low IQ settings?!?!

If true, that's very surprising!

Maybe Kerma was smoking already at higher IQ setting and lowering the number did nothing but add smoke. Raising the boost would probably have boosted the power with lower IQ number. That's just what I have found dealing with the 11mm pump, bigger injectors and evry mod.

It might then seem that what I've been hearing about changing the IQ has nothing to do with power or fuel economy, as it only changes the fueling at idle speed?

Will someone that jknows jump in here and 'plain please.

Changing the reported injection quantity adds or subtracts a constant over the entire fuel map. If you change reported fuel delivery at idle by 1 mg/stroke it changes fuel delivery over the whole map by 1 mg/stroke. Remember, it takes the same amount of actual fuel to make the engine idle no matter what the number says, so an increased reported number at idle reduces the actual fuel delivery throughout the whole range.

The thing is this: +/- 1 mg/stroke at idle is a significant change (actual fuel requirement is around 4 or 5 mg/stroke) but +/- 1 mg/stroke at full load is insignificant compared to around 40 mg/stroke fuel delivery.

Beyond a certain fuel quantity, anything additional just makes smoke rather than power, so changing it by 1 mg/stroke at full load could very well make a big difference in smoke without changing power much at all.

Derrel, I _think_ I know this so I'll try and explain:

The IQ number is the calibration number between the collar position of the quantity adjuster and the information that the ECU uses when adjusting the collar (=the IQ number seen on VAG-COM).
Let's say that the actual injected quantity in to the cumbustion chamber at idle is 4 mg/R (we really don't know that, there is no measurement). If you have the IQ number say 2.4 at idle, you have the calibration under-biased for 1.6 mg/R (excuse me for the poor terms). Then when you floor it and the IQ number is something like 35.2 mg/R at full load, the ACTUAL injected quantity is something like 36.8 mg/R (constant 'bias').
If you over-bias the IQ by putting the IQ number to like 7.0 mg/R at idle, you will have only 32.2 mg/R actually injected into the combustion chamber when the IQ number is showing 35.2 at full load.
All of this is based on the assumption that the error between actual IQ and reported number is constant over the whole load range. It may or may not be that but the idea is the same whatever the case.
So, changing the IQ number via VAG-COM indeed affects the maximum power output. And, like almost all power enhancing mods in the TDI, it doesn't affect fuel consumption when driving habits remain the same.

Basically, it is like instead of reducing the I.Q. via vag-com, you put a piece of something below your accelerator. The thiker the piece - the lower the I.Q....... And then if you want to increase the actual injection quantity, just make a hole under the accelerator, so you can press the pedal furthur. LOL

Thanks. That is what I figured. I will just have to see how much smoke I will have when I install the PP.205s. Any word Kerma on the new shipment?

Click to expand...

Check your mailbox Tuesday.

Kerma,

Are you saying that in your dyno runs you found no
difference in power between high and low IQ settings?!?!

If true, that's very surprising!

Click to expand...

No, what I said was that there is no discernable difference in the 1/4 mile times or MPH between full rich and full lean. If anything it is faster at full lean. Go figure. I dunno why.

Right now with the hammer mod my IQ is at 11 or so. Much less smoke, but in the hot weather its still there pretty big. I am thinking that the PP520 were great in my auto in the winter, but are a little much in the heat of the summer. Anyway, I have some PP357 AND some stock auto injectors coming fresh from the "Lubespecialist Labs" so we will see how they all stack up. Quarter mile dyno first at the Wed night test'n tune then hopefully back to back dynos.

Wish I had a stock ECU now, though.

I don't think the idle setting should affect full throttle. Here's my own crackpot theory why: The ECU limits the IQ by limiting the max DURATION of injection according to the smoke map. IOW it uses the actual collar position to determine this. The ECU is programmed for the stock injector configuration, so that is the basis for the smoke map.

ANyone ever do Vag-com logging at cruising speed, WOT, idle, etc. comparing the actual/requested IQ at different operating states? I have. WOT IQ doesnt change. Steady state cruising IQ doesn't change. Still the same requested and actual IQ except at idle, or just off idle.

Flame shield- ENGAGE!

ANyone ever do Vag-com logging at cruising speed, WOT, idle, etc. comparing the actual/requested IQ at different operating states? I have. WOT IQ doesnt change. Steady state cruising IQ doesn't change. Still the same requested and actual IQ except at idle, or just off idle.

Flame shield- ENGAGE!

Click to expand...

Charlie, I have done plenty of VAG-COM logging of the various IQs blocks/fields over the operating regime, and I share your observation.

As a matter of fact, this was going to be my next TDI 101 mythology lesson!!!

The adapt IQ (AIQ) is only in play at and just off idle, that's it. It is the indicated fueling value used by the ECU as the actual fueling value when the driver requested fueling value is below the AIQ value.

For example, AIQ set @ 5, at idle, foot off pedal, Actual IQ (ActIQ) reads 5, driver requested IQ (DRIQ) is zero. Step on the pedal a bit, ActIQ reads 5, DRIQ reads 1. Step on the pedal a little more, ActIQ reads 5, DRIQ reads 3, step on the pedal a little more, ActIQ reads 5, DRIQ reads 5, step a little more, DRIQ reads 7, ActIQ reads 7.

If the AIQ is 5, the indicated ActIQ will be 5 for DRIQ values <5. Once the DRIQ exceeds the AIQ, the ActIQ will then track the DRIQ.

That's all the Adaptation IQ value does.

Therefore, how folks report changes in power & smoke is interesting, since actual fueling is unchanged by the IQ adjustment.

Crackpot theory part 2:

THis setting just changes some constant in the feedback loop... So, the largest effect is under transient conditions. Steady state is not affected. This could help explain the smoke difference under acceleration.

The discussion of what the IQ adjustment does/doesn't do has been moved to this thread: IQ Adaptation Doesn't Do It Either

Carry on.