Mythbuster: continuing project thread of my 1303 '75

[Wally]

Originally Posted by Sandeep

Question for you ... can you switch between boost setting maps with the DTA, while you are driving ? Perhaps by a switch or button ? One setting for , say 10 psi (stun) and one setting for 20 psi (kill) ?

Thanks

Sandeep

Hi,
Yes, with the S60 model it works like you described.
I haven't gotton to that myself though.
The boost control map can almost do the same, but then rpm and trottle position dependent. So, half throttle you develop 10 psi and full throttle can gradually 'drive' through the map towards your setting of 20 psi or whatever. This is basically what a electronic boost control does is my understanding.
Again, an however...: the idea of the PWM boost % map is brilliant, but to get the right psi at a certain % is a lot of tuning. Without a dyno this is a PITA and bringing in different temperatures/tunes into the game, it becomes even more difficult to get a steady boost pressure.

There is a very tricked out PID control boost regulation in the ecu as an alternative to the PWM map method though, but no-one a spoke to seems to have it working...

Sooo, I probably still 'have' to invest in an aftermarket ebc...when does it ever stop...?

[70Turbobug]

I can imagine that tuning by that method is tedious,it might be easier to use a stand alone EBC even if you do decide to go with the PWM map method.The ECU I will be using also has an integrated boost controller that can be adjusted by the touchscreen pad display in the dash.These are all problems I still have to encounter,though.But i am looking forward to it!

[Sandeep]

Thanks for the information Wally. I have an AEM Tru-boost currently, but was trying to decide to sell it or not. I will keep it and see how the S60 tuning goes.

Once the new heads and cam arrive, I can start building the motor ... still need to decide on a straight cut cam gear though.

Unfortunately, it never ends ...

Sandeep

[paul_f]

I have a theory about how to setup these boost maps on the DTA that we are going to try on my friends beetle when he has it running again.

You really need a dyno to set it up, and a ignition cut set on the ECU at the highest boost you will ever want to run.

The tuning of the PID will only work if the target map is set to a real value that can actually be reached.

So the target map needs to be defined well. The way to do this is to disconnect completely the wastegate (which is why you need the boost ignition cut) and do a full load run logging the boost pressure against engine speed until you get to the max boost level.

From this log, you can then work out the actual maximum boost that the system can attain and this curve (or perhaps a little lower boost per engine speed) must be used on the DTA.

By doing this the actual PID will be able to work correctly as it is trying to control to a boost level that is actually attainable.

If you request a boost level that is not able to be obtained, the I term will wind up, causing massive instabilities in boost pressure when the engine speed reaches a level where the engine can meet the required boost.

[Wally]

Originally Posted by paul_f

I have a theory about how to setup these boost maps on the DTA that we are going to try on my friends beetle when he has it running again.

You really need a dyno to set it up, and a ignition cut set on the ECU at the highest boost you will ever want to run.

Paul,

Trust me, its no fun when you have set the overboost (your 'highest boost you will ever want to run') on 1,6 bar/24 psi and repeatingly the ecu cuts out your ignition violently at 1,6 bar (24 psi) whilst trying to run 18/20 psi.
Its either wastegate boost or overboost cut-out. The window is simply too small.

This turbo EASY goes to 2 bar/30 psi on my motor in just a few hundred rpm. It already overshoot to 1,8 bar/26 psi. Áll this is NOT funny I can assure you. How the engine has survived all the violent cut-outs still surprises me.
So, you see, getting an 'attainable boost' really is not my problem .

The tuning of the PID will only work if the target map is set to a real value that can actually be reached.

I advice you keep the tru-boost for now Sandeep
I really like DTA and it has one of the most advanced PID control algoritms on the market or so I understood, but personally I haven't seen anyone get i working properly, not even the professionals on the DTA-forum...

So, good luck Paul and let me know when you have succeeded, then I would really bow my head to you

[paul_f]

HI Wally,

I think you misunderstand me a little.

You only run this test once, and this is only to tell you how the boost rises against RPM.

At 4000rpm you can easily attain 1.6 bar, but at 1500rpm you will struggle to make 0.5bar, 2000 maybe 1 bar.

If you set the DTA demand curve at a higher boost pressure (ie 1,6 bar at 2000rpm) than the engine can attain then the controller will wind up, so then it is to slow to open the valve which causes the overboost.

With its single calibration for P I and D I doubt the DTA can be made to work to do everything. I personally would only initially use it to try to eliminate wastegate creep.

I don't know what makes it particularly advanced, but from the available calibrations it looks extremely simple to me.

For the PIDs I work with, we tend to have 10x10 maps with additional multiplication maps to make them work correctly.

If you have the means then a standalone boost controller would definately be an easier route with more likelyhood of success.

[Wally]

Originally Posted by paul_f

HI Wally,

I think you misunderstand me a little.

You only run this test once, and this is only to tell you how the boost rises against RPM.

At 4000rpm you can easily attain 1.6 bar, but at 1500rpm you will struggle to make 0.5bar, 2000 maybe 1 bar.

If you set the DTA demand curve at a higher boost pressure (ie 1,6 bar at 2000rpm) than the engine can attain then the controller will wind up, so then it is to slow to open the valve which causes the overboost.

.

Ah, yes, I misundestood
See your point now and I agree, after two years of trying, I think a aftermarket ebc would be best also.

[Wally]

So, in absense of an ebc, I just deleted all settings and ran on wastegate today at our first trackday of the year. Its was COLD!
Track was partly covered in ice we we arrived early in the morning...
First session was a wet track, the 2 session afterwards were dry. Yesss!
Had great fun doing easy laps driving/learning the lines. New rear brakes bedded in nicely, but fronts still block first. Maybe also semi's up front as a next tire choice.
Still with the old struts, and the thicker rear torsion bars get my thumbs up! All in all a good test day :-)

http://www.youtube.com/watch?v=Tq_m04LZreM

[fahrvergnugen]

You've bin very busy Wally, well done

Wish my car was ready for track day's. Hope to drink some Hertog jan with ONN again this year.

Paul.

[Wally]

Cheers Paul, me too!


Big tnx to Franc fo taking the pics in that cold winter day

[volkdent]

You've made me jealous! I've got to wait till the end of this month to attack Laguna Seca. The bug won't be ready by then, but at least I can get on the track!

Looks like you had a lot of fun, are you thinking about adding dual master cylinders and a balance adjust feature?

Jason

[Wally]

Originally Posted by volkdent

You've made me jealous! I've got to wait till the end of this month to attack Laguna Seca. The bug won't be ready by then, but at least I can get on the track!

Looks like you had a lot of fun, are you thinking about adding dual master cylinders and a balance adjust feature?

Jason

Driving on Leguna Seca would make me jealous Jason!

Yeah, your right: dual masters and balance bar would be the best solution for me at this point. The installation however would involve things I rather don't like to do, so I'll try to postpone this decision...

[Wally]

Hey Sandeep, Paul,

You guys won't believe this: I have the PID control working!

I do use a Volkswagen N75 boost control relais, so my settings will not automatically transport to other boost control relais, but if you also use the N75, lemme know, I'll mail you my settings in the S60

[paul_f]

Excellent news!

The settings would be very useful.

[Humble]

I'm an hour away from Laguna Seca, Jason you should stop by on your way down. It'll give you a chance to drive on my favorite roads