I'm using direct boost with a GM 3-port to set boost to around 25 psi. If I disable "Target Boost Error Correction" by entering all zeros in the "%WGDC Change" setting, my boost curve is good. As soon as I enable target boost error correction, I get a spike when the turbo first spools, and then I lose a few pounds of boost while the error correction is fixing the spike. I've attached my boost settings, and datalogs and charts of the boost curve with and without error correction. I want to be able to enable error correction without it mangling my boost. Any ideas what I've got configured wrong?

disregard the AFR in the thumbnails btw, it looks like I lost my connection to the AEM UEGO during one of the logs.

 

I actually think you're really close. You're probably just pipping the "boost target" thing a little. Try...

(1) Checking your Baro sensor. If you're at sea level, you could find your atmospheric pressure is at 14.7 or 14.9... but you've got a constant "Atmospheric Boost" value of 14.3... so you could be a wee bit behind the curve to begin with.

(2) Tweaking the 3000rpm boost target. It looks like you're really hugging that boost target curve super-close from 3000rpm (18psi) to 3500rpm (25psi). At 3400rpm, your target will be 23.6psi. Factor in (1) above, and in adjusted terms that could easily be 23.0psi. Touch 25psi at 3400rpm, and it could twitch the wrong way, and reduce WGDC... at the same instant the wastegate opens.


I don't see you "spiking" over where you want to be. And I don't see any big difference in spool-up area from one to the other. You've got zero allowed upward error correction at WOT, so that will keep some complexity out of the equation.


Just a few ideas there, anyway...

Rich


edit: Just checked the logs (better late than never, lol). Whatever the reason for you touching 27.3psi "with EC enabled" and 25.6psi "with EC disabled", it doesn't actually seem to be related to EC at all. Your Actve WGDC is pretty much identical between the two logs. I'd put it down to either normal variation or voodoo. One of the two.

 

Thanks for the response. I had to turn off upward WGDC correction because it was making my spikes even worse. When I'd go WOT at low RPMs, it would increase the WGDC trying to get me to my target boost, and then I would spike over the target boost.

I changed the settings to 14.7 for atmospheric pressure, and increased the target boost to 23 psi at 3,000 RPMs. I attached a log from that run, and I'm still getting overshoot followed by undershoot.

 

I've not tuned a 3-port, sorry. Perhaps someone who has can chime in. I'd just summarise that latest log...

• WOT @ 3000rpm.
• BWGDC around 70%.
• Boost touching 28.5psi by 3800rpm.

Again, sorry, but I know when I don't have the level of experience to provide constructive input. Plenty on here who do and can, though...



Rich

 

Post up your new boost curve, the stock one isn't very good for this turbo. Honestly this turbo makes 20psi at ~2500rpm. If you REALLY want to wait until 4000rpm to hit full boost (you don't have a red/black right?), you need to make your WGDC be equally laggy. WGDC and Boost need to match up, either both fast or both laggy. If you look at the "shape" of your curve, you are treating it like its a 35R, your boost curve should be "/" not ")". And w/ a 3-port, having a really "tight" EC will give you constant corrections UNTIL you nail it down perfectly. If you want a bit of room to figure it out, turn the boost down a hair and increase the EC Interval to like 3ms.
Look at my boost curve as an idea of how this turbo spools (Fast); ignore the MIVEC part, only pic I could find in photobucket atm:


Also, remember w/Direct Boost there is no such thing as "0". A fully open WG will still give you ~11.5-12psi. 0 only works for Load Based Boost (because the Base Load table is still applicable).

 

You must be doing something right that I'm not if you're able to get 20psi by 2,500 rpms.

I've attached my current WGDC and boost targets. I really need to work on my part throttle WGDC and target boost as well, but that can wait until I nail down WOT.

 

I can see in your Boost tables what the problem is, your 2500-2750 boost target are WAY too low for your WGDC table. Look at them, they don't match. Either A) remove the WGDC 2250-2750, or B) increase your boost from 2250-2750 (my recommendation is B).
The 3-port is WAY more responsive than the stock solenoid system, so you should only have WGDC WHEN you want boost.

 

Thanks for the help. I can definitely give that a shot, but if you look at the first data log without error correction, I'm nowhere near those levels of boost in lower RPM ranges. I went WOT at 2,300rpms, and the boost looked like this:

2,500rpms = 5psi
2,750rpms = 10psi
3,000rpms = 16psi

When I had upward WGDC correction on and used targets higher than those, I'd get a bigger spike when the turbo spooled as the correction was adding 3-4% WGDC to my baseline trying to reach the lower RPM targets.

Only mods are K&N drop-in, HFC, and CBE, so I may not be able to spool as quickly as other cars.

So you think I should be less aggressive with the WGDC the sub-3,000rpm range?

 

The turbo is naturally overshooting your boost target. Like Richard mentioned, change your target boost down low. Once you have the target boost set properly, you can decide to soften the WGDC Change.

 

OK I just looked at your logs (maybe I should have done that to start with), your timing is way too low at peak boost. Timing keeps boost from spiking

 

That follows your boost curve as requested, except at 3000 cause it can't add 13psi in 250rpm
Up your boost pressure from 2500-3000, you'll like it I promise

 

Notice the changed scale on the Target Boost Error Correction.

This setup works like a boost clamp or MBC. But it allows for different boost at different throttle positions. It will prevent overboost. You may get a tiny spike, but the ECU will actively cut WGDC until boost is back in range.

 

I should have posted both high and low WGDC. On a GSR, I set the crossover point to 75 and run these so that people don't vent their blocks by flooring it at low RPM in 4th or 5th gear.

 

i'm kinda confused on the 75. is that 75mph, so anything over 75 mph uses high gear wgdc?

or is that a ratio of rpm/mph?

 

It's a ratio...

Rich