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Discussion Starter · #1 ·
What do you all prefer when dealing with boost spikes between shifts?

Do you ignore it?

Do you prefer to have very low upward boost error correction values then tune for a slightly lower psi with WGDC's and have the error correction bring you up to the target PSI?

How do you deal with boost when a person goes WOT at like 4500RPMs?

Thanks for the input!
 

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On my RA, I've had great results tuning BWGDC to be correct for the initial peak when going WOT at any RPM point... and then allowing some upward EC for the ongoing target tracking. So yeah, you're on the same track.

I also went patching the ROM, to sort out some of the rough edges. See here for the extra patches I put together - these are now available for most X ROMs. :)

That stuff includes a patch to better manage boost for SST WOT upshifts. It needs some of the aforementioned "allowed upward" EC factor, and the boost control must be tuned so it requires upward EC to hold targets. The patch just zeroes this EC factor at upshift, pre-emptively dropping BWGDC by a bit. It may do the trick, but YMMV depending on bcs, t/c, etc.


My patches also have IAT Adjusted BWGDC, and I'm part-way through releasing Baro Sensor adjusted psi-based boost targets, for altitude correction. So it's quite useful, I reckon.


As you've spotted, by allowing some upward EC into the mix, you can separate "post-spool-up peak" boost levels from ongoing target-based levels. Plus, you can pull that trick of discarding the upward EC on WOT upshift. So it kills two birds with one stone.

Maybe this will give you some ideas! :thumbup:

Rich
 

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Discussion Starter · #3 ·
What about for GSR's though, I still see boost spikes on upshift with the GSR, your patch seems geared toward SST's no?
 

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If your BOV spring is too tight it does not open all the way and not enough air is vented at the shifts.
 

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What about for GSR's though, I still see boost spikes on upshift with the GSR, your patch seems geared toward SST's no?
Are you talking NLTS? Or actually getting off the throttle between gears?

Rich
 

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Discussion Starter · #6 ·
Nono, I'm not referring to the BOV not opening or NLTS, what I'm referring to is when you're running through the gears and you lift off, shift from say 2nd to third from like 7300rpms. This lands you somewhere above 5k in third. Then you got WOT again, the turbo spools instantly b/c you're already at such high RPMs and the waste gate can't react quickly enough which causes the boost to hit a higher boost target than what I intended. If I go WOT in 3rd from say 2500 RPMS, I don't get this spike and my boost peaks nicely at say ~27psi. If I shift hard from 2nd to third and mash it right when I hit third, it spools so fast it over spools and I usually hit 28 and sometimes 29 psi for a very brief period before the boost comes back down to the targeted area through EC or whatever else.
 

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Tapering MIVEC sometimes works on correcting this...
 

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Discussion Starter · #8 · (Edited)
From my understanding, based upon what I had read Tephra say at one point, I thought this was fairly common. If it is, is it something I should be concerned about? After looking back at my old logs, my previous tunes from various shops (not my own as in this case) also had this same phenomenon. Am I incorrect in this assumption?

Tephra's quote in regards to this topic (from a different thread):

to me its akin to going WOT at like 4500rpm in the GSR... its going to spike because the Wastegate cant react fast enough.
 

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From my understanding, based upon what I had read Tephra say at one point, I thought this was fairly common. If it is, is it something I should be concerned about? After looking back at my old logs, my previous tunes from various shops (not my own as in this case) also had this same phenomenon. Am I incorrect in this assumption?

Tephra's quote in regards to this topic (from a different thread):
It is true, but you can try to Minimize it if it produces a lot of knock with MIVEC.
 

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Discussion Starter · #10 ·
Mine doesn't cause any knock at all, but I do on occasion hit 29 psi. Should I be concerned about this at all?
 

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bump i get the same issues.

IMO if it isn't causing knock then no prob.
 

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Discussion Starter · #15 ·
2, it corrects quite often. I thought of putting it down to 1 to see if it has an improving effect.
 

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i had this issue with my pos synapse dv car boosts properly on the dyno ect ect. but when i shift before 6500 i spike to 29 then i went back to stock fixed it right up jon from cobb socal mentioned synapse and random boost spikes and sure enough he was right go figure .
 

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Discussion Starter · #17 ·
i had this issue with my pos synapse dv car boosts properly on the dyno ect ect. but when i shift before 6500 i spike to 29 then i went back to stock fixed it right up jon from cobb socal mentioned synapse and random boost spikes and sure enough he was right go figure .
Hmm, I'm not sure how any BOV would affect what I'm seeing as the point at which I would see 29 psi is when the BOV should be closed. My only assumption would be that the stocker leaks when it hits that high of psi and this leak helps reduce the drasticness of the spike. The spike occurs when you got WOT at an already high RPM b/c the waste gate can't react fast enough. At this point in time the BOV should be fully closed so I'm not so sure it's the Synapse DV.
 

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oh just lower your wastegate duty cycle then lol and make sure you have boost correction on
 

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Not sure if this thread is still active at all, but i experience the same thing, especially from 1st->2nd at WOT and 2nd->3rd. AMS tuned my car and i have been incredibly happy with it!!!! when i do spike that 28/29psi i do not see any knock either. i was a little worried when i saw this at first but with no knock and the fact that it only spikes it for a fraction of a second i really can't see how this could be damaging. if it holds 28+ for more than a blink on pump gas then id be worried. curious to hear what others think. i run 93 pump gas
 

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not sure this still alive, but getting same issue, if wot even 2000 rpm in 5th, boost holds 23/25 and drops as expected, but if im just driving 5th 3000rpm and drop to 4th and wot = creates spike to 30psi, if take it all the way and shift to 5th and wot= spike again...annoying...
 
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