[OpenFlash]

Hi guys,
I've gotten a few emails from 6AT v4 customers telling me that their peak hold boot gauge reading is ~2psi higher than expected. For example, those running Stg1 routinely see 13-14psi of boost (depending on barometric pressure) on their boost gauge, hit the peak hold recall feature and see 15-16psi. This is normal. This is why:

Unlike previous version of the PROcede, v4 handles the 6AT shifting situation differently. Instead of making the 6AT behave like a 6MT and close the throttle between gears, we are keeping the throttle open. How much open depends on your applied throttle (right foot).

Closing the throttle between 6AT upshifts isn't ideal for a number of reasons:

1) It causes a 20+psi pressure spike in the intercooler tube that, coupled with manifold vacuum, discharges the bypass valves. So you lose all or most of that boost pressure you had. This means the turbos have to spool up again. It also mean that you subject your turbos to a 20psi pressure spike which thrust bearing can do without if given the choice.

2) It creates a sudden load swing (full load/low load/full load) situation that opens the engine up to transient mis-calibration which can induce knock, boost oscillation, and general drivability imperfections.

3) It's just plain slower.

So instead, of doing it the old way, our mapping keeps the throttle open during the shifts. This creates a ~2psi pressure spike during the shift process for a fraction of a second. Often, you wont even perceive this on a digital boost gauge. But your boost gauge will record it and show it to you when you ask for the peak hold value.

So why does it boost spike? Simple.. When a turbo is providing Xpsi of boost at say 5000rpm and the revs suddenly drop to 4000rpm after an upshift, the turbo is still spinning at the roughly the same speed it was at 5000rpm. Because it has inertia, it takes a split second for for the turbo wheel to slow down and provide the desired boost pressure. During this brief period of time, there is a ~2psi overboost. So if your maps routinely runs 13psi at full throttle, you will see a ~15psi peak value. Similarly, if your map runs 15psi at full throttle, you will see a ~17psi peak value.

Is this more stressful on the turbos? Absolutely not. The turbo doesn't care because it was already spinning at the same speed a moment before when it was in a lower gear (at a higher engine RPM). In fact, the turbo would have been a lot less happy if the throttle had closed, been hit by a pressure surge and then had to spool up again between shifts. So no, the turbo is perfectly fine with this.

Is this more stressful to the engine? In this case, no it's not. Because in this situation, this brief period of overboost, total ignition advance drops from several degrees of 0 degrees. Actually, it goes negative advance but the PROcede logger isn't configured to display negative advance . While only 2-3 degrees of transient ignition retard would have been sufficient to ward off knock during this boost spike, the extra timing retard has another function: to drastically reduce engine torque in order to make life easier on the torque converter. The advantage using timing reduction instead of boost reduction to reduce torque is because it can be applied instantly. There is no "tapering" off of engine torque as there would be if boost was cut. Instead, the ignition retard cuts power instantly. And just as importantly, it adds power back instantly. Something that boost adjustments cannot do.

All these systems work together to make the shifting performance on a PROcede v4 powered 6AT car unbelievably positive and consistent while providing minimal stress to the transmission.

Here's a datalog (at the standard 30-35hz) of a manually induced short-shift at WOT illustrating all these systems in action:


Enjoy!

Cheers,
shiv

[cn555ic]

Thanks for clarifying that Shiv...great read!

[Ilma]

Interesting sequence of events.....

Makes intuitive sense that one can change timing a lot faster than one can change spinning turbines.

And yes....eliminating throttle closure between shifts should reduce the backpressure heading back towards the turbos....which can only be a good thing for them.

[mmmmQuattro]

Can't wait to test the V4 on my DCT...

[GreenPlease]

Wow! Cutting torque during shifts alays one of my principle fears: that my AT will get trashed.

[OpenFlash]

Originally Posted by jp330Cic.au

Can't wait to test the V4 on my DCT...

v4 should work perfectly on a DCT car. I'd love to see some datalogs.

Shiv

[AltecBX]

Originally Posted by shiv@vishnu

Closing the throttle between 6AT upshifts isn't ideal for a number of reasons:

1) It causes a 20+psi pressure spike in the intercooler tube that, coupled with manifold vacuum, discharges the bypass valves. So you lose all or most of that boost pressure you had. This means the turbos have to spool up again. It also mean that you subject your turbos to a 20psi pressure spike which thrust bearing can do without if given the choice.

2) It creates a sudden load swing (full load/low load/full load) situation that opens the engine up to transient mis-calibration which can induce knock, boost oscillation, and general drivability imperfections.

3) It's just plain slower.

Sounds like what BMW is doing with the new N55 engine on the 335is. Looks like Shiv got a sneak peak at the N55 new temporary overboost, or collaborated in how to make more torque for overtaking and other high-load/high-speed maneuvers.

[deletedelete]

The shift logic stuff is part of v4? And what exactly does it do, tune the trans for faster shifts?

[OpenFlash]

Originally Posted by AltecBX

Sounds like what BMW is doing with the new N55 engine on the 335is. Looks like Shiv got a sneak peak at the N55 new temporary overboost, or collaborated in how to make more torque for overtaking and other high-load/high-speed maneuvers.

It's funny that no one ever put 2 and 2 together about to all my recent trips to NJ

Shiv

[Dackz]

Originally Posted by shiv@vishnu

It's funny that no one ever put 2 and 2 together about to all my recent trips to NJ

Shiv

We all just thought you were hanging with Snooki, The Situation and Paully D

[OpenFlash]

Originally Posted by Dackz

We all just thought you were hanging with Snooki, The Situation and Paully D

lol... i wish!

[mmmmQuattro]

Originally Posted by shiv@vishnu

v4 should work perfectly on a DCT car. I'd love to see some datalogs.

Shiv

I am about to put v4 on, but there isn't anywhere that I can safely drive to 110 around here.
It will take me weeks to organise a track day. I might look into a dyno run.

[AltecBX]

Originally Posted by shiv@vishnu

It's funny that no one ever put 2 and 2 together about to all my recent trips to NJ

Shiv

I'm just like Sarah Palin, I can see NJ from here just like she can see Russia from Alaska and see what's going on.

[scalbert]

What are the effect on a 6MT running these maps?

[Ilma]

Originally Posted by scalbert

What are the effect on a 6MT running these maps?

From Shiv's download site....

4) Map1 and Map2 are no longer identical. Map1 is a standard 6AT map (also compatible with 6MTs)

[OpenFlash]

Originally Posted by scalbert

What are the effect on a 6MT running these maps?

With the exception of the boost spike, you'll see the same events since much of it is DME induced (mid-shift ignition retard for instance). With the 6mt, as you've seen, a quick shift will keep boot at 10psi between shifts without any "lagfix" or "bogfix" bandaids. The reason the throttle doesn't hang up between shifts is because actual and target boost stay hand-in-hand regardless of the situation.

Shiv

[stressdoc]

As I understood it, these are some of the issues that were involved with different OEM programming for the manual transmission from the start, and then the BMW perf version. At least with the Steptronic you have a more predictable and hence controllable situation. With the manual the vagaries of different shifting parameters required more conservative OEM boost control.

V4 appears to provide a much more 'direct' power flow. Consideration of issues involved during shifts is important, and yet another significant advance in tuning.

[LostMarine]

Shiv, are you telling me that you designed V4 automatics to hold full boost through the shift, reducing torque quickly via timing reduction?
Is this for reducing wear or for more/smoother acceleration? That seems like a pretty big accomplishment to me, if so, nice job

[OpenFlash]

Originally Posted by LostMarine

Shiv, are you telling me that you designed V4 automatics to hold full boost through the shift, reducing torque quickly via timing reduction?
Is this for reducing wear or for more/smoother acceleration? That seems like a pretty big accomplishment to me, if so, nice job

Re-read the first sentence in my first post. I was explaining to customers why their 6ATs are seeing peak hold boost readings 2psi higher than expected. And then explained why it is caused and why it is okay. And why this is different from what we did before (overshoot boost target and force a throttle closure).

Make sense?
Shiv

[LostMarine]

Originally Posted by shiv@vishnu

Re-read the first sentence in my first post. I was explaining to customers why their 6ATs are seeing peak hold boost readings 2psi higher than expected. And then explained why it is caused and why it is okay. And why this is different from what we did before (overshoot boost target and force a throttle closure).

Make sense?
Shiv

yes it does, thank you. another Q, would a stock n54 see a similar/smaller boost spike between shifts?

[scalbert]

Originally Posted by shiv@vishnu

With the 6mt, as you've seen, a quick shift will keep boot at 10psi between shifts without any "lagfix" or "bogfix" bandaids.

Yes, have seen this, but the confirmation is nice.

[e.n335]

Originally Posted by LostMarine

yes it does, thank you. another Q, would a stock n54 see a similar/smaller boost spike between shifts?

I see a max. 1 PSI spike with my ECU flash, mostly 0.3 - 0.7 PSI.