Hi,

Been self tuning for a while now, slowly changing and learning all the while. Bit the bullet a while ago and upgraded to a 3 port which is running good as. However, I almost constantly have an issue with a boost drop between 3,500 and 4,000 rpm.

Have attached a log from this morning which is typical of a 3rd gear pull. Tried playing around with WGDC and also with boost (psi) targets to get error correct to do the right thing with no avail. Hit my target at 3,500 (23psi - driving an RA), but then it dips down to 21'ish before recovering to 23 around 4000 - 4200rpm.

Am I missing something obvious?

Another question as well - at what point does WGDCC begin? Is it time based or load/psi based? Can I adjust it myself to, say, kick in at 2,750rpm?

Thanks in advance

 

Boost tuning can be a real exercise in tail-chasing.

If this drop happens right after boost peaks, it's pretty much par for the course with the stock RA turbo. I don't know anyone who really eliminated it altogether.

There are steps you can take to minimise the duration of dip. Chances are, though, you'll still get that 1-2 psi temporary dip as the wastegate opens the first time.

Take a look at the "GST Base Map" boost control style. There are a number of factory at work, and the boostpill versions pull all the threads together pretty well.

It's a big, complex area. I'm hesitant to list every aspect, as I'd be here all day. Perhaps I can find my past posts on it, and refer you to them... Will look.

Rich

 

Lol - getting that impression re chasing my tail. I understand the opening wastegate boost drop thing but thought a 3 port over a pill would sort most of that out.
Running off an altered gst map but will load one up tomorrow night and compare the 'flow' of the target and wgdc maps with mine. Also have a fair few of your threads bookmarked so will reread them and others and go back to basics and review what I'm doing from the ground up.
Thanks for the pointer re the gst maps, hadn't occurred to me to go back them for a guideline.

Thanks for that Rich

marc

 

I remember a couple of people who voiced an opinion about the TD04's wastegate size... that it was a bit big for the turbo itself. They reckoned the t/c lost more spin than it ought to as soon as the wg cracked open.

Me, I wouldn't be at all surprised with a 2psi drop on initial WG crack-open. Normal. A little bit surprised it's just as bad with a 3-port, but hey.

Small turbo that loses rotation very quickly? Slight over-sized WG? Perhaps. It would explain a lot.

GST Base Map allows some "positive" error correction, fast EC interval (2), a quick upward EC adjustment from being "too low", and makes sure the very first cell or two of the upward EC adjustment table has zero values (so the dumb ECU doesn't max out its upward WGDCC during initial spool-up).

The idea is to get the EC reacting quickly AFTER peak, as soon as the post-peak dropoff occurs. The bonus "positive" allowed EC is there to help pull the boost curve out of its little dive as fast as possible. The value of max positive EC should be JUST the amount needed to restore and maintain ongoing boost levels after the dropoff. On 2-port, that's 8-9%.

Rich