Topic: Compressor Surge

[Arabas]

since i am dealing with this issue right now, i thought I’d start a topic for reference in case someone needs some info on the future and to help educate each other.

i was wondering why i was hearing that sound and Dirty Mike informed me about it when i first asked about it.

what is surge?
compressor surge occurs when the compressor sends more air to the engine than what the later can take advantage of.
so, then, the air flow is reversed and bypass valve opens to release the excessive air. if we keep our foot on the gas (WOT), amount of air goes back to the compressor (reversed flow) and it can cause turbo to fail or even damage the engine. so when we hear it, it is the time to take our foot off the gas pedal. googling compressor surge can give more accurate description of the problem, this is just my own simple explanation. also in youtube, someone can find a lot of good vids of how surge sounds

upgrading the compressor wheel and running a tune for stock turbo, it caused bypass valve flutter which was easily heard even if you don’t know what you should be listening at. it sounds like the bov that repeatedly opens and closes.
if you have an analogue boost gauge you can see the needle trembling on WOT (moving between a range of psi at very high speed).

after 3 updated  tunes, i am at the stage where if i drag race, I only get surge on 5th gear.
But If I WOT with 3rd (or 4th or 5th) gear from 2000-2500rpm, when the boost builds up at around 3000rpm, I get intense surge.
I suppose this happens because when drag racing and shifting to 3 or 4 gear, you get into high rpms and the turbo doesn’t need to build boost from low rpms, that is to spin so much to send excessive amount of air.
But when you are cruising with 3rd gear low rpms and you press the pedal for maximum power, the turbo needs to build up boost fast, which causes it to push excessive air towards the TB.

I am not sure how a tuner eliminates compressor surge and this would be interesting to know.
One more thing that makes me wonder is that since the compressor sends more air, wouldn’t it be reasonable to adjust the ecm so that the engine can suck all this air (of course adjust the fuel that gets sprayed as well) thus turning into power this bigger amount of air?
One more question is if surge also occurs with bigger than stock turbos as well (not just a compressor upgrade)

When I went on with my mod, I had no clue about compressor surge. If I had, I would think it over.. it’s not pleasant to hear this “phew-phew-phew-phew” thing, it makes you worried..

Pls correct me if I have said something wrong. Any input on surge would be highly appreciated

surge video

[Kelu]

Correction:

after 3 updated  tunes, i am at the stage where if i drag race, I only get surge on 5th gear.
But If I WOT with 3rd (or 4th or 5th) gear from 2000-2500rpm, when the boost builds up at around 3000rpm, I get intense surge.
I suppose this happens because when drag racing and shifting to 3 or 4 gear, you get into high rpms and the turbo doesn’t need to build boost from low rpms, that is to spin so much to send excessive amount of air.
But when you are cruising with 3rd gear low rpms and you press the pedal for maximum power, the turbo needs to build up boost fast, which causes it to push excessive air towards the TB.

The surge is not present in higher rpms because the engine is more capable of inhaling the amount of airflow produced by the turbo and also because the boost drops in higher rpms.

Also the big turbos doesn't seem to suffer because of the surge because they produce boost a lot later (in rpm range) than our stock turbo where the engine is capable to inhale a lot more air.

ECU tuning consists mainly from reducing the commanded load (boost) in low rpms. I'm not 100% about this but this is the only logically idea which comes into my mind now.

[Arabas]

what you are saying about engine being capable of inhaling much more air at high rpms is very reasonable and this looks like a good explanation.
nevertheless i haven t noticed any significant boost drop on high rpms (talking with stock turbo and tune). i d say that the surge starts to occur at overboost and of course i haven t stayed on the gas to see if it gets away whenthe rpms get high

[Kelu]

nevertheless i haven t noticed any significant boost drop on high rpms (talking with stock turbo and tune).

How do you monitor the boost through RPM? (I hope not the factory DIC boost gauge)

[Arabas]

i have an analogue boost gauge hooked up Kelu

[DirtyMike]

I don't get surge in any gear or rpm since the updates. BTF has posted how to remove it on the HPtuners forum along w/ some stuff you need to download.  But your using trifecta so....?

[Arabas]

Dirty Mike, first of all, thx for letting me know what the problem was in the first place.
yes, i wouldn't tune myself, i don't qualify being a tuner, so i don't mess with what i don t know (and cost too much if i fail).
i trust Trifecta for tuning my GT. so far we have made progress, but we still have some way to go to resolve surge once and for all. waiting for his new updated tune.
i think that it is fair for people thinking of doing a wheel upgrade to know beforehand that they will have to resolve this issue to take advantage of their mod, that' s why i started this topic

[Gentleman Jack]

Arabas,

What topic did you post the video of the surge?  I'd like to give it a listen, and might be good to link the video to your first post here.

Thanks,

GJ

[Arabas]

i haven t filmed mine GJ. but on the first post i added a video that shows how surge sounds like, per your request

[DirtyMike]

I didn't nor want to tune myself, just upload and log.

Just keep logging and tuning eventually you'll find an update that works for you.
Defininty not a plug and play mod. Those considering know that tunning is required on all larger compressor wheels. And if your scared to void warranty then dont.

[LatinVenom]

THe DDM boys know how to take care of the Surge.
I am surprise Vince has not figured it out as of yet.
The other thing to consider would be the size of your upgraded wheel.
I believe yours is a bit larger than the one from BTF, Werks or DDM.
I know is a bit much to ask, but maybe Dave or Randy may want to add some input (friendly forum advice) for this thread.

[Arabas]

It seems that "deleting" compresor surge is a trial and error procedure.  Vince talked to BTF and the solution is to "work around it by advancing the intake which causes a loss of torque" for whatever that means...
other solution is to install a new BOV and block off the stock bypass valve.
for the moment i prefer on working with Vince to get rid off the surge without any mechanic mods, unless he tells me it s absolutely necessary to place a new BOV.

[Kelu]

advance the intake??
What does that mean?

[Arabas]

i believe it means advance the intake camshaft (still dont know what this means   )

[Kelu]

oh, so cam tuning

[gmtech16450yz]

Compressor surge can very easily and effectively be created or eliminated by tweaking DAL's, MALT's, TM/Gear and cam timing. Nothing mechanical HAS to be done, but can also help.

[Arabas]

Thx for the input gmtech.
unfortunately those terms are a bit difficult for me to understand in english...

i suppose you are saying something like the below, which is something anyone having a big wheel mod should bare in mind when it comes to tuning the big wheel turbo.

"The fix is to advance the intake cam timing, which increases overlap and improves exhaust flow to the turbine to overcome the stall.  also retarde the exhaust valve timing."

[gmtech16450yz]

Thx for the input gmtech.
unfortunately those terms are a bit difficult for me to understand in english...

i suppose you are saying something like the below, which is something anyone having a big wheel mod should bare in mind when it comes to tuning the bg whelle turbo.

"The fix is to advance the intake cam timing, which increases overlap and improves exhaust flow to the turbine to overcome the stall.  also retarde the exhaust valve timing."

Yeah kinda, except increasing overlap sometimes just blows all that extra boost pressure out the exhaust which actually cools the charge which is a very bad thing to do with a turbo.

Very simple explanations...
DAL's... Desired Air Load. This table tells the computer how much airload or torque the particular pedal position and rpms you're at are requesting the motor to deliver. This has effect on pedal to throttle plate mapping and boost pressure. (although not as direct a control as we'd like to have.)

MALT's... Maximum Air Load Torque. This table controls the maximum airload in relation to the DAL table. (You can give it a ton of DAL airload, but have the MALT's take it away, they must be balanced properly.)

TM/Gear... This table controls the maximum amount of torque delivered in relation to what gear you're in. Very useful in controlling boost spikes, which often happen at high load/low rpm's, like in upper gears. (hint... at the same time you'll often get compressor surge.)

Hope that helps, I've never been to Greece, what's it like living there?

[Arabas]

gmtech do our cars have TM/gear?


all members, sorry for the offtopic..
how is it in Greece? i suppose no one could say bad things about the place he is born and raised...
well, Greece is a small country with all the pros and cons that this has...
imho it's a beautiful country, nice weather, blessed with some natural advantages like thousands of islands, oil trees and some thousands years of rich history (first manuscript-book- was written in Greece by Homer around 1100 BC, democracy as a political system was invented in Greece in it's purest form etc).
major cities are alive all through day and night.
but, Greece has suffered many wars (including many civil wars) and was been left to pick up her pieces in modern times, while most modern countries have been evolving.
this, along with some real bad politicians, have deprived Greece of great prosperity in the recent yrs...

well, i may as well shut up and invite you to visit Greece. i'd be glad to show you around gmtech!!

[gmtech16450yz]

Wow Arabas, that was awesome! In those few sentences you taught me more about Greece than I learned (or can remember) in school. Thanks! I've traveled tons in the US, Mexico and Canada, been to Hawaii a few dozen times, but I've never been overseas. My wife has traveled Europe and we plan on the two of us going one of these days, maybe we'll look you up!

Back on topic...
Yes, our cars do have TM/Gear, it's a hugely useful table that I think most guys don't know enough about. It's in "Torque Management", "General", "Max Torque", "Max Engine Torque vs. RPM vs. Gear".

Here's how I figured out what it did... First of all, the column headers are wrong, it shows "first, second, fourth, fifth, sixth". I figured out that fourth is actually third, fifth is fourth and of course sixth is actually fifth. I made a tune that had 75% in the 3000rpm row of second gear, and 50% in the 3000 row of third gear. Put it in the car and drove it. The 75% in second came right at 3000, and was noticeable but not huge. The 50% in third also came in right at 3000 and was like I chopped the throttle, then floored it again at 4000rpm! You could see the huge dip in the throttle and boost in the log, so I knew this was a table that could be VERY useful. From there, over many tunes and logs, I gained MUCH better control over throttle mapping and boost.

Thanks again for the Geography, History and Demographics lesson! BTW, what are the women like? (Ha Ha) The women in the US are very independent, very smart, obsessed with how they look, and love to gossip about other women! All of those things can be good and bad obviously, a lot of women here are a little TOO obsessed with looks and clothes, which means they're usually hot looking, but are also shallow and boring. Once in awhile you find one that's hella smart, cute, looks good but not obsessed with it, is an amazing mother, horny girlfriend and someone that supports you in every way, and you marry her! I got lucky and have been married to my best friend for 26 years. Hell, she even rides dirtbikes and likes cars!

Now I really got us off topic! (There is some good info about Kappa's in there, people will just have to find it!)

[Arabas]

gmtech16450yz, letting us know of this Max Engine Torque vs. RPM vs. Gear table, is IMHO a VERY useful tip. GT owners in Greece, we were wondering if such a thing exists or not. Thx for the tip!! 
i suppose that through tuning this chart, you can actually custom tune a kappa for many many different uses (auto-x, drag, drift, cruising etc etc).
and by taking advantage the fact that through the cruise button you can select different tune on the fly, this gives us endless possibilities! 

i received last night an updated tune from my tuner and i saw real progress in diminishing compressor surge. it is Vince's principal to work step by step, tune, log, re-tune and all over again, until desired outcome is accomplished.
Now, i mainly get surge on 5th gear below 4000rpm, so i suppose if cam tuning can't help for 5th gear, i can take advantage of the Max Engine Torque vs. RPM vs. Gear table!!

[Kagem]

Nice tips here, thanks tech! George there is a whispering outside my window that says your surge issue is about to be extinct, it sounds like a beautiful lady singing ''No more surge to keep you back, one more flash and start the attack''! Good news my friend!