vtisturbo

Weird one here. Turbo B18C4 on hondata S300 running 13psi.
Been running fine recently until about a week ago when WOT and it reaches 5k rpm it hits a wall like fuel/boost cut. Just stops you dead. Builds boost properly, AFR's are fine.. does it in all gears at WOT.
However....you can drive around it if you half throttle through the rev range and then boot it at 6500rpm or whatever and then it works ok. You can then even drive perfectly normally at WOT through the revs for a few mins, and then it'll go back to fuel cut issue again! REALLY strange. Possible earth issue perhaps?

Any help welcome.
Thanks.

Chance EG

Wow very odd. Maybe TPS related? It doesn't sound like a misfire?

Datalog a few pulls if you can, make sure the MAP sensor is staying consistent in the higher RPM's with what pressure it's seeing.

What ignition system/spark plugs/distributor are you using?

vtisturbo

Yeah its definitely not a misfire. Running a new hondata 3bar map sensor too..
NGK Iridiums, NGK blue leads (brand new) OEM dizzy cap and rotor (All new) MAP sensor looked good too as i had the laptop out with the live feed whilst doing it and it was seeing the same as the boost gauge. So strange...

2kdrift

Data log it, anything less is just a guessing game sounds like a cut which the ECU may be doing on purpose boost cut etc

boosted94gsr

What is your launch control rpm set to? Make sure your speed sensor is working correctly and reading the same on your gauge and laptop. Most of the time launch control is set up to activate based on mph, so if your speedo isn’t working properly it can cause it to activate when you don’t want it to. Also take a look and see if full throttle shifting is activated, as that can cause issues like this based on how the parameters are setup as well.

Balor_Gr

ICM maybe?

vtisturbo

Full throttle shift is turned off, launch is set at around 4200 iirc..
The speedo reads and acts correctly at all times..


I did wonder that but normally you have starting issues etc? I do have a spare non oem one though so can try i guess.

2x0

+1

Sounds like a fluke in your calibration or it's getting a weird signal. A quick datalog will show you what it is.

vtisturbo

But thats not possible if the calibration hasn't been touched surely?

2x0

Calibrations can be corrupted, but more likely it's getting a bad signal from a sensor such as VSS telling it to enable launch control, etc.


Stop arguing and get the damn datalog, you could have had this fixed by now.

vtisturbo

ha ok will do.

Dark_Teg

My car would do this when it got colder outside. It was something with the temp tables.

vtisturbo

it has coincided with it getting colder. Can you remember exactly what it was?!

Dark_Teg

I am no tuner but the local guy that figured it out said that it had to do with the colder weather. Something about the colder temps were making it hit boost cut ?

vtisturbo

oh. lol, yeah that makes sense but its definitely not that unfortunately!

Dark_Teg

Try running just off the gate and see if it still does it.

2x0

If your ECT aren't getting up to where you have the cold boost cut, could be that.

There are also fuel vs ECT and IAT compensation tables that could be off, making it run too rich or lean and causing a misfire. I had this happen before where it would dump so much fuel if I opened the throttle much when it was cold out, it would misfire almost like hitting a limiter.

TheShodan

iTrader: (14)

*sigh*. This is why I don't try to go into every single "log" & "table" on the software. Because if you don't know what you're looking at, how do you know that what you're looking at needs to be changed?

It's rather simple. Colder, denser air can be converted to pressurized air much quicker than higher temperature air. This means that it will create positive boost pressure much earlier and faster than normal. Which means that whatever your boost pressure cut is from the system, it's reaching it faster when you go into a higher acceleration situation than if you gradually built pressure in partial throttle. This is also why independent electronic boost control is much more usable on turbocharged vehicles than all the laptop-based stuff. If you need to make a small adjustment due to colder weather, drop the duty (or target boost) down a notch or two, and keep going!

In this case, I'd for the OP, it's best to either check the wastegate to make sure everything is hooked up properly, (no tears or collapsing lines) or reduce the duty on your boost control a bit (be it from the laptop or manual controller). Then try it again. But if you truly are in a colder climate, stop going to WOT so much. You're not making it easier on the car, and you are leaning out a touch. If your tuner is good, he/she will have accounted for it, so there's no need to touch any of the fuel trims or ignition timing at all.

What you're experiencing is a phenomenon that many factory turbo applications deal with on a regular basis.

LightningTeg

Or get the closed loop working correctly and never touch boost control again

vtisturbo

Well thank god you were here to come and state the obvious. I’ve had many many turbo vehicles so know the basics thankyou. As I said in the OP, AFRs are fine because I have a wideband gauge staring me in the face. Boost cut has been raised and furthermore it is not boosting any higher than normal, as shown on my boostgauge and on the map sensor. And as for climate, I’m in the UK and by cold I mean like 3degrees celcius at the lowest. Hardly arctic.

Balor_Gr

Mine did it only after the engine was fully warm and was doing it only on full throttle.No starting problems no bounching tachometer no nothing.
Just like a strange rev limit and some bangs.

vtisturbo

Awesome info, thanks. I’ll give that a try for sure.

vtisturbo

Moderator/almighty shodan please kindly change my thread title back to what it was.

TheShodan

iTrader: (14)

I'll gladly edit the thread title, but your original was very confusing for searching for others to give feedback or understand your situation, nor could really anyone tell it was yours. It looked like 50 others that are in over 18 years of archives. .. PM me some other ideas, (they don't have to be special, but definitely different than what you had) but what you had was completely vague and incomprehensible.

Also, Raising the boost cut limit on the boost controller is a very standard way of avoiding your boost cut issue, regardless of your thoughts. That is because the parameters of the range that the controller believes that boost will spike is shorter verses actually raising the limit itself to allow your target boost to be acquired more quickly. So, as much as your sarcasm was understood (you gotta work on it a bit better if you want to give the desired effect. , my suggestion has sound logic.

vtisturbo

Ive always been very proud of my sarcasm thankyou. The boost is ECU controlled. The cut is set to 15psi and the cold cut to 7psi. Its an external wastegate and boost is rock solid, never spikes or tails. My boost guage ha a peak hold and doesnt register past 13psi nor do i see it past 13.2psi on the datalog. Unless im missing the point and you actually mean something else, could you please elaborate?