Been looking for the answers to this and I have yet to find some answers.

All my mods are in my sig btw.


So i was at some very low rpm's in prep for a 3rd gear run and i was logging at the time. When i punched it i was probably at about 2k rpm and the turbo of course starts to spin up before it would reach boost the car bucked hard so i let off the gas slowly got it past 3k rpm and floored it again at which point it ran fine up to 6.5k where i had to let off.

So I'm trying to understand what could cause my car to buck at this low rpm?

My wideband is on the fritz right now so i can't monitor fuel.

 

You were most likely experiencing compressor surge.

Surge line
"The slightly kinked diagonal line on the main (i.e. lower) part of the map is known as the surge (or stall) line. Above this line is a region of unstable flow, which is an area best avoided.

A compressor surge, typically, causes an abrupt reversal of the airflow through the unit, as the pumping action of the aerofoils stalls (akin to an aircraft wing stalling)."
http://209.85.165.104/search?q=cache...lnk&cd=1&gl=us

 

It sounds like compressor surge, but it 's amazing that you would be able to get surge on the stock turbo. How quickly do you spool?

 

Apparently quickly enough to cause it..

I do have buschur's intake and stuff though is there anything i can do to minimize it?

 

Small bump and information.

I attempted replicating this in 4th at 2k rpm my boost gauge showed it crawling up to 5 psi then bucking around 2100rpm.

 

Can you post up one of your your logs so we can troubleshoot it ?Sounds like tip in throttle enrichment.

 

Sorry about the wait its been a crazy two days of working at my job with no free time to get on this place.

So here's a run with the log you can see the AFR map dip radically downward during the bucking then up then down before i let off the gas then tried again.

 

Maybe an issue with the IX diverter valve? When I adjust my Turbo XS H34 valve too tight it tends to surge and buck exactly like you mentioned, although it's kind of strange to get surge at a low rpm when you're full on the throttle.

 

is your diverter valve in backwards?

cb

i see lots of them backwards

 

Definitely not on backwards it blows off all the time the intake lets me hear it clearly.

It doesn't do the Dr. Zoidberd whoopwhoopwhoopple effect of flutter.

 

With out looking at your afr's i say it's either tip in enrichment is too lean or you have a vacuum leak.

 

Sorry for the noob response but what tables would i be modifying to compensate?

Once i get my wideband operational, just need the time currently, what afr's do you think I should shoot for? I've been told 12.5 AFR during spool up is ideal.

 

Fuel tables first.
For tuning afr's just keep your eye on knock and go with what the car can take safely, start by 11.8 on spool and 11.0 on the top and see how the car likes it then make changes untill you happy.Don't forget the ignition tables.

 

Have you disabled the lean spool?
I remember when I disabled it, I experienced the same thing before.
In my case, Injector pulse width was halved around 2500 rpm and returned normal after 3000 rpm.

 

Funny you mention that becuase i put lean spool back on and this started.

So basically I know lean spool is going to richen my map up a ton so i'm putting my old map back in and adding alot of fuel to it to see what happened.