I built ECUs from scratch in a prior lifetime, but am totally unfamiliar with the 996 ECU control strategy. Can someone tell me the limits of the factory computer with respect to boost control? Can boost be made to vary with RPM? If not, do any aftermarket tuners do it?

The reason I ask is that I've always felt that constant boost left some power curve on the table, and tuning for constant cylinder charge, subject to detonation limits, was the way to go. So, for example, if the volumetric efficiency without the turbo peaked at 4000 at 90%, and was 80% at 3000 rpm, why couldn't you run 90/80 = 1.125 times the boost at 3000 that you do at 4000 (subject to adjustments for added temperature rise, etc.). So, basically, the strategy is to run max constant cylinder charge unless you run against the detonation limit, or the turbo runs out of ability to reach that pressure.

Thoughts?

 

Great topic. If you have seen some dynos you would see how flat the torque is. To limit torque most tuners close the T/B some then open it up after the torque peak. Playing with turbo speed will induce lag IMHO.

 

I didn't even think about that. My days predate drive by wire. That's exactly my question. So, they limit manifold pressure using the throttle plate? Do they typically vary the intake manifold pressure

Torque is a pretty good proxy for cylinder charge, so maybe that is common practice. Make the torque curve as flat as you can, use the throttle plate to modulate it, only open the wastegate if the throttle plate strategy generates a certain pressure drop across the throttle plate, like .2 or .3 bar drop.

Is that what they do?

 

with this ebc it is possible programming boost depend from gear/rpm /throttelposition with data from obd port

 

So it is not possible to control this with the stock ECU?

 

No that is a standalone EBC. OP are you talking about part throttle or wot?

 

What is OP?

I'm talking wide open throttle. The stock ECU doesn't vary boost pressure with RPM, or is not capable of it? You need to use an external stand alone controller?

 

you can control boost via the n75 solenoid duty cycle map at WOT.... it also is dependent on the WGs and WG settings used.... that map is engine Temp. vs RPMS... if memory serves me correctly....

 

What are your thoughts about varying boost pressure to generate constant torque (within detonation limits and turbo compressor limits?). If the engines volumetric efficiency is 80% at one RPM and 90% at another, and you run 1.3 bar at 90%, why not run 90/80* 1.3 = 1.45ish bar at the 80% point? Same stress on the engine (more or less), no?

 

My thoughts are that stock k16s run 1.1 bar max if that... thus no go on 1.45 bar...
R& D can be quite expensive... I suggest you get a maestro 7 software and start paying around...
good luck
markski

 

How about with your k16 billets?

Sounds like you run constant boost on your tunes?

 

with upgraded WGs and k16s you can but not 1.45 sustained... too much heat not enough hotside.. etc... on race gas with intercoolers and injectors with catless exhaust you get decent results....
there are quite a few boost maps to start with... cams ON cams OFF maps , n75 map, absolute map, n75 look up table map, etc...
as weather changes so does the boost on cars... it sucks because on a cold day it will run 1.3 bar and on a hot day barely 1.2 bar... timing starts to pull and drama starts... and that is all just with constant boost or at least trying to maintain it,.., something it doesn't do all that well either.. guys throw on their own WGs set them wrong.. and expect you to tune it remotely... void...
I do not like to run lots of boost on pump... I found 1.2 bar with decent timing and some cooling is a good approach... for high boost on pump you are running 6 deg of timing in midrange... not for me...

 

So K16 Billets, intercoolers, injectors, and 1.2 bar or more?

 

Oh, and how fast would you spin a stock engine with the K16 Billets, Intercoolers, and Injectors? 7000? More?

 

If you want more power than K16s, get K24s...