Pulsing acceleration

Hello, I've been getting this pulsing feeling while accelerating lately. It usually happens when I'm above 4000 rpm and between 70 mph upwards. The motor is a built rb26dett with 1300cc ID injectors, R35 coils. I run iridium ix spark plugs heat range 8 with Garrett GTX2867R twins. What I've seen from the datalog is that during the acceleration the boost goes up to 21psi then down to 15psi then up again. It keeps cycling like this until I back off the gas. I've changed the plugs and I'll be checking the fuel filter tomorrow. Does anyone know what could cause this? I've enclosed the latest log.

Surging is usually caused by a non-linear torque progression over the conditions that cause the surge. So it's likely your ECU tuning. You don't mention what ECU or tuning platform you are using, so it's unlikely someone can provide an exact solution.

It could be a boost leak that opens up at higher pressure, but after the pressure drop takes a bit to recover.

What does your ignition timing map look like over the conditions of the surging.

What does your boost target do in those conditions -- is it varying?

Perhaps it's a boost control issue, with too much proportional gain on the PID, causing a boost overshoot.

Sorry about that, I'm using the Haltech Platinum Pro plug-in. My target boost is 22psi

Hi I did take a look in your log. The boost solenoid ossiliting a lot between 100-35% that cause de surge. Something in your boost table setup is not right.

I would agree there's a boost control tuning issue. If you share the calibration we can take a look. I could throw out ideas, but some would be irrelevant pending your settings.

I haven't looked at the car in a couple days, I'll screenshot the maps.

don't waste your time. Screenshots are practically useless. We need the config and the data log to dig into things.

The data log was what I posted right? How do I access the config log? I'm more than happy to do it because it would help in solving this mystery. The car ran without issues before, and nothing was altered.

The configuration is the file you are editing with the Haltech software. That is what you were promising to send screen shots of. By posting the configuration, we can correlate what is in there to what we see in the data log, without asking 40 questions.

So my suggestion to anyone looking for tuning help: Describe the problem you are experiencing, provide a log and identify in the log where you think the issue is, and provide the ECU Configuration / Calibration / Map to that it can be examined for what might be the cause, or what could be adjusted.

Looking at your log. The problem you describe occurs around 120 seconds. You can see the Boost Control Output is 100% until your Boost Control Actual equals your Boost Target, then the Boost Control Output switches to 35%, and the Boost Control Actual starts to drop, until is reaches Boost Control Output Start Point, when it switches back to 100%.

It doesn't look like the PID is working at all. I would check the settings in your haltech configuration for Boost Control. Is there an Open Loop Boost Duty cycle table? If so 35% is certainly not the right value for that boost target.

I don't have my laptop with me now so when I get home I'll send the config. This car was tuned two years ago and I do remember the tuner setting up open loop control before we did closed loop. Thanks.

There's a quick spool option and perhaps the offset to target where it drops out of that is set to a small value. It could be a massive amount of integral windup. Could be a bunch of stuff without seeing files.

Sorry about this, but can someone give me a little walk through a to how to access and upload the configuration files? I'm stumped, much appreciated.

While you're connected to the ECU, please go in the file menu and click save as, save the tune somewhere you can easily find it, then attach it to a post here like you did with the log file.

I'll get to it this evening, thanks for your patience never done this before.

No worries. We are here to help!

Hey guys I've followed the instructions but each time I try to upload the file I get an error message. I'm not sure if this is because my platform is the Haltech Platinum Plugin Pro. I was looking online for solutions and its shows how it's done for the elite series which is the same instructions that Mike gave in chat. I'm enclosing the error message. I think I'm stumped.

Sorry for the trouble, that's odd. Are you able to host the file and give us a link to it?

When I get home I'm going to try to resend using my laptop, the other times I tried my phone and my tablet. If that doesn't work I'll try your suggestion.

OK, if you get stuck please let me know and we'll work something out.

Hey guys, so I did a couple runs and adjusted my PID values accordingly. i still need to fine tune and smooth the boost curve out some more tho. Thanks to everyone for helping me! Mike special thanks for your patience. I've been told that the ecu platform that I run is different than the Haltech esp which is Haltech Elite, that's why it would not load here. Anyways thanks again.

Data log here

Hopeton,

I'll work with support to contact you directly for the calibration file.

For now I looked at this log file. It doesn't contain the behavior you mentioned in the first post where boost goes up to 21 psi down to 15 psi, then back up.

When you apply stable throttle, you have pretty stable boost, though boost does vary as you move throttle around.

At lower throttle angles sometimes you are running into a situation where 100% duty is commanded as a spool aid, then boost control transitions to "normal" operation once sufficient boost is achieved. If that isn't desired you can turn that system off or reduce the max boost level for the spool aid so it shuts off sooner and won't be as noticeable.

In terms of pulsating above 4000 RPM, your boost control output is pretty stable during the one 70ish percent TPS pull, despite boost not achieving target. The engine speed trace looks dirty during the pull, so if the car isn't fighting for grip, then perhaps it's misfiring. It's hard to guess what you're hearing.

What boost solenoid, wastegates and solenoid frequency are you using?

Unrelated, oil pressure drops a lot why you apply throttle, then pops back up when you lift throttle. This is not normal. Have you investigated that?

This is the oil pressure oddity I noticed, the drop when you apply throttle.

Hey Mike, I'm running the Haltech 3 port boost solenoid at 25 hz with internal wastegates. The car's acceleration is mostly smooth, I had E85 in the tank for over a month without the car being driven, I've since filled up with 93 octane. I didn't notice the drop in oil pressure before you pointed it out. I've also noticed that the oil pressure goes back up when I ease off the gas, not sure what that about I'll check past logs and see what those say.