[Clap135]

http://www.e90post.com/forums/showth...19#post8709619
link to log, needs alot of work imo

[longuyen88]

in for updates!

[Alan l.]

Originally Posted by Clap135

http://www.e90post.com/forums/showth...19#post8709619
link to log, needs alot of work imo

Thanks for posting it up for my Clap. Hopefully Cobb can use the input from users to fine tune their maps.

Alan

[335isGuy]

Alan is ur car a auto?

[Alan l.]

^^ Its a 6MT

[itsbrokeagain]

Originally Posted by Alan l.

^^ Its a 6MT

lol thats odd....Procede had issues with AT cars but 6MTs were fine..now its been reversed.

Id like to see how they go about resolving this.

[themyst]

Originally Posted by Matt@Camber-Toe

lol thats odd....Procede had issues with AT cars but 6MTs were fine..now its been reversed.

Id like to see how they go about resolving this.

I don't think it has anything to do with the transmission choice, it's what Shiv said earlier, wastegate tolerances. If you see Clap's log, you see there is no boost overshoot and he is FBO, whereas Alan's car is overshooting with less mods.

The good news is, I can't get my 6AT to misfire anymore

[Alan l.]

^^ Yeah it not a 6MT or AT thing.

I spoke to Rob at Cobb yesterday about why there are throttle closures on mine and not Claps. He said its most likely due to turbo variances because his own 335 logs are very similar to mine. My car has just about 9K miles on it and its never been boosted past 13.5-14psi before where as Claps car is full stage 2 plus meth thats been through high boost. Kinda like comparing a virgin to a hooker?

The closures isn't a problem for me since Cobb already said its part of the way they tune the N54 and trust me you don't feel it. I went WOT several times that day all the way to redline and not once did me or my buddy (also has a 335xi with a Jb3) feel the car stutter during the pull. He was actually very impressed with the AP.

Question -
Now can someone explain why throttle closure is looked upon as being "bad" or worse than lets say the wastgates opening up to limit boost pressure? Logically if a car is building boost 12-13-14psi and then hits its limit of 15psi ------> car then closes the throttle slightly to keep the boost from overshooting >15psi, then opens the throttle again wouldn't the manifold still be pressurized close to if not at 15psi? Wouldn't that be better than lets say the same scenario but instead of throttle closure the car opens the wastegate to bleed boost where you are almost certainly going to lose more pressure in the system which the car will have to ramp back up?

Forgive me if i'm totally off base here. I'm still new to the world of force induction and none of that could have made any sense

Alan

[Pseudo Nim]

Alan - I am curious on your opinion on v4 vs AP. I am in exactly the same boat as you, so I am curious to compare notes. I suppose we should talk over PM to avoid causing unnecessary tuner wars.

[**335i**]

Originally Posted by Pseudo Nim

Alan - I am curious on your opinion on v4 vs AP. I am in exactly the same boat as you, so I am curious to compare notes. I suppose we should talk over PM to avoid causing unnecessary tuner wars.

did u tryed new maps that shiv offers maybe u will chamge your mind. no tune wars just oppinions

[Alan l.]

Shiv sent me a new map to try out so I will have a direct comparison between the AP and the latest offerings from the V5. I just need to find time where its not snowing or raining here in NY to swap tunes again and be able to do some logging without ending up in the guard rail.

They both feel good but different. I use to think the JB3 was more raw compared to the Procede and now i think the Procede is more raw compared to the Cobb because its so smooth. In terms of power compared to the older V4 maps the Cobb feels stronger mainly because i was only boosting 12-13psi tops with it where as with the AP i'm seeing 14-15psi.

[Pseudo Nim]

Originally Posted by **335i**

did u tryed new maps that shiv offers maybe u will chamge your mind. no tune wars just oppinions

To be fair, I stopped at the last v4 map - I didn't want to VIN-lock the Procede. So I am basing myself on the last non-VIN-locked maps. There is probably quite a bit of difference with the v5 - so I'll let others comment on that.

[**335i**]

Originally Posted by Alan l.

Shiv sent me a new map to try out so I will have a direct comparison between the AP and the latest offerings from the V5. I just need to find time where its not snowing or raining here in NY to swap tunes again and be able to do some logging without ending up in the guard rail.

They both feel good but different. I use to think the JB3 was more raw compared to the Procede and now i think the Procede is more raw compared to the Cobb because its so smooth. In terms of power compared to the older V4 maps the Cobb feels stronger mainly because i was only boosting 12-13psi tops with it where as with the AP i'm seeing 14-15psi.

try it and tell us also try run some badass cars (closed street) maybe u cant cos of weather.....

Originally Posted by Pseudo Nim

To be fair, I stopped at the last v4 map - I didn't want to VIN-lock the Procede. So I am basing myself on the last non-VIN-locked maps. There is probably quite a bit of difference with the v5 - so I'll let others comment on that.

not a problem for me vin lock, also wonder when there will be some runs in youtube with cobb no videos found yet

[dzenno]

All of a sudden this got huge potential to go sideways

[atlharry]

Originally Posted by dzenno

All of a sudden this got huge potential to go sideways

How so? Granted, everyone's got their panties in a bunch regarding throttle closures, but I don't think that's taken anything away from the potential of the tune.

[Pseudo Nim]

Originally Posted by **335i**

try it and tell us also try run some badass cars (closed street) maybe u cant cos of weather.....



not a problem for me vin lock, also wonder when there will be some runs in youtube with cobb no videos found yet

You and your video requests.

Someone take a vid with the Procede and the AP...... and use www.youtubedoubler.com.

[OpenFlash]

Originally Posted by Alan l.

Question -
Now can someone explain why throttle closure is looked upon as being "bad" or worse than lets say the wastgates opening up to limit boost pressure? Logically if a car is building boost 12-13-14psi and then hits its limit of 15psi ------> car then closes the throttle slightly to keep the boost from overshooting >15psi, then opens the throttle again wouldn't the manifold still be pressurized close to if not at 15psi? Wouldn't that be better than lets say the same scenario but instead of throttle closure the car opens the wastegate to bleed boost where you are almost certainly going to lose more pressure in the system which the car will have to ramp back up?

Forgive me if i'm totally off base here. I'm still new to the world of force induction and none of that could have made any sense

Alan

Closing the throttle to reduce boost pressure has one big side effect: it reduces pumping efficiency of the engine.

Think of sucking through a straw at a given flow rate. if you want to reduce the flow rate, you have two options:

-suck less hard (no giggles please)
or
-put your thumb over part of the straw's open end.

The first approach doesn't make your lungs work any harder for the air that is ingesting. Your lungs are operating at peak volumetric efficiency.

The second approach causes your lungs, to work harder than what is ideally required to support that airflow rate.

Now, if you airflow rate is low (ie, gently inhaling), you don't really notice much. As the relative effects of your thumb's obstruction is minor. But now if you're sucking REALLY hard, suddenly putting your thumb on the straw's opening makes you want to gag (no jokes please). In this case, your lungs lose Volumetric efficiency.

Now your engine is nothing more than an air pump. And pumps like to operate with no internal restrictions. Which is why we make intercoolers that flow well, throttle bodies that are big and non-restrictive, intercooler pipes that don't have big sharp bends and intake filters that are nice and open. All of this pays off when you are move a lot of air. Because with every little bit of restriction, you are forcing your turbos to work just a little bit harder than they need to. And the harder the work (faster they spin for the desired air flow), the hotter the outlet temps are and the higher the exhaust backpressure is. Both of which reduce engine power. Again, this isn't a big deal at lower boost pressures (5-6psi) where you have tons of reserve turbo capacity, mild/moderate nominal airflow and relatively small turbulence effects.

But at higher flow rates were the turbos are being run well towards (and beyond) their efficiency range, the effects of these closures are felt and seen.

Of course, the solution isn't to completely eliminate the system that closes throttle as a result of overboost. But rather to prevent the overboost from occurring in the first place. And maybe to rescale the reaction of the throttle to be more suitable for higher boost applications when an inevitable overboost does occur. As we've seen, this requires a boost control system that is a bit more adaptable than what BMW gave us. Especially given big car-to-car hardware variance in the turbocharger hardware. Until boost control logic is suitable, it is unlikely that it can work acceptably on a wide range of cars, in a wide range of conditions, with a wide range of associated modifications.

shiv

[Pseudo Nim]

That's a REALLY good read. Thanks shiv.

[Alex@Helix]

^ +1

[AWD Addict]

Originally Posted by Pseudo Nim

That's a REALLY good read. Thanks shiv.

+1

The comic relief was appreciated too.

It'll be interesting to see how Cobb uses the throttle plate modulation to control boost when they get to the bigger tune applications. It seems like based on Shiv's explanation that the more dramatic overboost conditions that will occur in those applications will be less smoothly handled by the throttle plate closing method.

Perhaps some combination of a better boost control solution and the throttle plate modulation.

Seems like for Stage I tunes though, the power and smooth power band are all there with great results.

[Doug007]

Good explanation for sure.

Of course the ideal boost control method would spool up to the boost target and open the wastegate at exactly the right time to hit the boost target without overshooting and the throttle would not be needed to trim the airflow. i.e., suck hard to get the air moving then suck less hard once its going

I think the big issue is the tuning of the throttle intervention. Due to the limitations on the in-manifold pressure measurement, it seems like BMW tuned to trim air flow with throttle based on some function of the amount of overboost.

So they would tune the system to say close the throttle 20% on a 0.5 psi overboost to yield the boost target in the intake manifold. However, when you increase the air flow and boost, that mapping needs to be retuned. A 20% throttle may reduce boost by 0.5 psi at 8 psi of boost (and associated air flow), but it will reduce pressure much more when running air flow associated with 15 psi of boost or 17 psi...

It looks like COBB did a pretty good job with this on the stage 1 throttle tuning from what we've seen so far. The load value is relatively constant and users aren't feeling the throttle intervention affect performance.

Time will tell how things go when they move up in boost with stage 2 maps!

[Clap135]

Am I the only on that disagrees with Shivs explanation? On a turbo car, the engine doesnt suck, it gets air forced down its throat. The only thing you are doing by closing throttle, is making turbos work for no reason to maintain a constant target air to be forced down the throat.