First post here. I have a twin turbo tundra, built 5.7L Toyota V8 with twin 6262s 0.82 A/R with "E" cover (non anti surge).

I've been having this issue occasionally (2-3 times a day) since the last time I've been to the track last April where if I let it idle or cruise at low RPM and then try to accelerate it would stutter and not accelerate between 0-4 psi. Sometimes if I kept at it, it would eventually accelerate but won't make target boost (10 psi instead of 14 psi) and feels weak. If I stepped on it again it would go back to normal until the next time after driving slow/idling for awhile.

For example, there is a 30 mile long stretch of highway with a speeding camera every 3 miles. I would slow down at each one of them along the way and accelerate again and the issue doesn't show up. As soon as the road ends and I'm cruising at 70 mph for a few minutes, it would stutter again under load.

Luckily I'm using a Haltech Elite standalone and looking at the logs showed clearly that whenever it would stutter, bank 1 would go lean and bank 2 stays on target. Sometimes its slightly lean (12.5-13:1) and sometimes all the way lean at 17-18:1. and those are the worst and would trigger limp mode on.

I also noticed that bank 2 was adding 10% more fuel using STFT than bank 1 which is 0-5% off of the base fuel map. That means if anything the issue should be on bank 2 not bank 1 incase the extra fuel was fouling the plugs. I tried setting both banks to correct STFT using the o2 from bank 1 and then from bank 2. In both cases the issue still remained.

I didn't know about turbo surge initially so I went the ignition/fueling route. Changed all spark plugs, ignition coils, cleaned and swapped injectors left/right, checked the exhausts for any leaks, swapped wastegates left/right, even new o2 sensors and bigger air filters. The issue is still there and the STFT stayed the same. Nothing changed.

After reading about compressor surges I started to notice that whenever I'm cruising or idling a popping sound would show up like an exhaust leak (note that my turbos are mounted at the end of the transmission below the cabin). Whenever I try to accelerate with that popping sound there it would stutter. I realized my driver side (bank 1) might be surging which would explain the lean readings and stuttering. It even sounds like air is rushing out underneath me and it's not spooling sound.

Now if this is turbo surge, I would like to know why this is happening to only the one on bank 1 and never on bank 2. The piping is practically identical both exhaust and hot side all the way to the intercooler. Note that I also noticed oil in the intercooler.

I don't think twin 6262s with a .82 A/R is too small and are spooling too fast for a 5.7L V8. Could it be that the bank 1 turbo is damaged/leaking oil causing it to be spinning less at low load and overcome by the second turbo? and when I accelerate it would clear the oil and for a short while be fine?

I forgot to mention that the BOV would stay open at idle and thought it might have been leaking boost. So I installed a stiffer spring to close it and only open when the throttle body is shut. But now after reading about surging I ordered the lightest spring I could find to relieve the pressure a bit even while cruising and will check for any changes when it gets delivered.

If anyone has any other theories or can confirm mine please let me know. And if I might be right, should I just get a rebuild kit and call it a day or leave it as is and get a bigger set of twins to prevent any surging in the future?

 

Any chance there is a header leak causing some air to fool the O2 sensor? Just a thought.

 

Thread that was showing on similar topics:
https://www.theturboforums.com/thre...rt-throttle-but-only-one-turbo-surges.334947/

 

Found that awhile ago last thing that was posted said he was gonna swap the gates. That's when I swapped mine. Nothing changed.

At idle bank 1 is fine and if anything the leak would have been on bank 2 since it's reading lean at idle.

Regardless, I checked the gaskets and they look relatively brand new. No burns or anything.

Just found a company that sells compressor housings for precision turbos. If the looser BOV spring doesn't work I'll get two along with a rebuild kit.

 

How do your fuel pressures look when this is happening?

 

Stable however my fuel pressure sensor is on bank 2's fuel rail which I don't think matters since the fuel lines are bridged before and after the rails. I've actually read on another forum someone who had the same issue bridged their fuel lines and it solved their problem.

In my case, I have a fuelab regulator with dual inlets and a single outlet (return line). I had both return lines go into separate inlets on the regulator. Thinking it might be the issues I inspected it and then did the following. I got a Y fitting and merged both lines coming from the rail into one single line and then to one port on the regulator. This way the fuel lines were bridged before and after the rails and insures equal pressure. This jumped the pressure from 40 to 43-45.

I then increased the pressure to 50 just in case. BTW I'm running ID1300x injectors and dual walbro pumps.

Surprisingly the issue went away for a week but then it came back. Jumped the pressure to 55 and then 60. At this point I was running rich at WOT (open loop) and it was still doing the same thing, stuttering and hesitation under load with it lean on bank 1. I went back to 40 psi as it gave the best AFR at WOT.

I've tried almost everything, only thing left are the turbos.

 

Do both turbo's pull from the same filter or are they separate?

 

Separate. I initially cleaned the filters. Then got new ones and finally a bigger one with a front inlet just in case the previous ones were too small. Still the same.

 

Remember what an O2 sensor does. It senses oxygen. That's it. It doesn't care about fuel. It cares only about oxygen. We look at the measurement as lean vs rich, when it's actually oxygen content. We're depending on complete combustion to give us an accurate reading at the O2 sensor.

So what happens when you have a misfire? Does it read rich because of the excess fuel? Nope. It actually reads lean at the sensor due to the incomplete combustion allowing unbound oxygen into the exhaust.

Many PCM's also act fast on a misfire. They will cut fuel and sometimes spark immediately on the cylinder that is misbehaving to protect the catalytic converter, which can make for interesting troubleshooting if you're not aware of what is happening, because it won't tell you.

Also piggyback boxes can retard ignition timing under boost by delaying the crank signal input, and this can affect the cam and crank sync on some engines, causing issues.

HPTuners's scanner is a very nice unit that works on pretty much any OBD II vehicle and I rely on it to gather data on problem cars because you can record pretty much everything and then review it later. I place a "marker" by stomping the gas pedal three times when I want to bookmark a point to go back and look. Makes it easy to find the pedal stomps in a datalog.

 

I get where you're coming from and believe me that's the first thing me and my tuner thought as well. The standalone I'm using can log everything I need and it simply doesn't show any issues being cams or crankshaft out of sync. It just throws a code if that bank (bank 1) goes lean under boost. If any of the ignition or injector signals are getting shorted it would throw a code for that as well. Anything and everything that would cause a misfire I have checked/replaced to make sure it's functioning well. Which then made me think it's simply turbo surge that builds up over time if the throttle body stays relatively closed for a short while.

I went to the track last week again and both turbos seem to do fine holding 30 psi with no oil leaks or play afterwards. I will be installing the 7 psi BOV spring to see if it can help relieve pressure at idle and cruising. If I see a difference I might just get an anti-surge housing just to move the surge line enough so it doesn't happen anymore.

 

What do your IAT look like when cruising and at full boost? I kind of wonder if you might benefit from a little larger compressor, if your already looking at upgrading housings maybe it would be a good time to step up.

 

Are you using MAF or is it SD?

 

IAT's are a bit high. Idle it's at 50-60c and goes up the longer it's kept idling no matter the ambient temp. Cruising, they're roughly 10 degrees above ambient. If it's 30c degrees outside, IAT going 70mph would be about 40c. At night it gets better but differential temp is never less than 5c.

Keep in mind I have a 3" 1300hp treadstone intercooler and a Water to Air intercooler that is chilled via the A/C in series (air to air before the water to air). Water temps are about 50f (10c) all the time. Introducing the water/air intercooler helped a lot when I first installed it.

At WOT It gets up to 60c, previously +90c without the water/air intercooler.

SD, intake air temp sensor before the TB and MAP sensor at the intake manifold.

 

I really think it's gotta be in the ECU. Do you have CL enabled? Tried turning that off?

 

CL turns off in that period where it stutters as throttle transition is too high when I floor it and by the time throttle is settled its above 60% and boosting which o2 control is setup to turn off then.

Also, if it was the ECU wouldn't it go lean on both banks?

A little update on this situation, since I was at the track last Thursday it hasn't shown any symptoms of this issue. I know as soon as I post this it's gonna come back lol.

 

Sounds like too much throttle for the gear/load. Needs to downshift.

 

So 3 weeks later and the issue seems to have been resolved after going to the track. Not sure if it was something in the fuel tank when I dropped it to drain it and put E85 or running 25-30 psi through the turbos and pipes. I did also install the 7lbs spring in my blow valve but the stuttering wasn't happening even before that for a week. Now it stays open while cruising and idle to prevent any pressure build up between the turbos.

My best guess is since the last time at the track something was "stuck" somewhere and when I ran +25 psi again it cleared it somehow. Crossing fingers it doesn't come back.

 

Sounds like you "blew the cobbs out of it" as they used to say.