Chevrolet Cruze Forums banner

1 - 20 of 26 Posts

·
Registered
Joined
·
103 Posts
Discussion Starter #1 (Edited)
So I went to the local tuning shop that has a great reputation of fabricating and tuning 500-4000hp cars to get some dyno results after BNR tuning. YIKES! It was a pretty bad experience. First off, a "Service Stabili-Trac" alarm popped up before we got the Cruze up to rpms. We restarted the car and made two 4th gear pulls. The first pull, the car threw a P0300 code and had horrible results. After clearing the code, resetting the tune and putting several driving miles on the tune we strapped it back down and again, horrible numbers and a slight hesitation at 5600-5700rpms.

I checked the plugs, which have only 4000 miles on them, 4000 miles on the entire car in fact... The plugs looked great. No signs of lean or rich conditions and all 4 measured at 0.028". All the coil plug springs were good. Adequate amount of dielectric grease. So, I went ahead and checked the downpipe, as well as charge pipes and fittings. All looked good. So, I did a global reset and went for a 40 mile drive. Afterwards, I made few WOT pulls and sure enough, the hesitation is still there. The car pulls very smoothly and shifts great too...but if I try to take it above 5500rpms; a slight blip in power will always occur.

I've never noticed this before, because the few WOT pulls I've made, I would shift at 5200-5300rpms. BNR has such a great reputation of creating great tunes for this platform that I'm conflicted as to what the root cause may be. But 145whp/180wtq is way too low for BNR tune with a catless downpipe, at low altitude, with ambient temps in the low 70s. Plus, this dyno is not known for yielding inflated numbers, nor false numbers.

Hope someone can chime in with a possible direction to go that I have not already taken. I've emailed BNR datalogs with a log that had the hesitation, my situation, and low numbers, but until then I'm just going to continue to baby it around as usual.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #3
I've relogged and have had a more aggressive tune sent and loaded.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #4
here are the dyno runs. The red line is the first run
 

Attachments

·
Registered
Joined
·
103 Posts
Discussion Starter #6 (Edited)
first run: 500miles on the tune
second run: about 25miles

The log I sent BNR was after a troubleshooting attempt, resetting the tune, and putting about 40 miles on the car. It seems too consistent for me to consider blow out. Especially when the dip in power only occurs for a brief moment, consistently at the same rpms as the second dyno pull. I am picking up a set of colder plugs today BKR8EIXs. I will install them, put some miles on the tune, and see if it continues it. Normally, BNR won't respond to my emails until Sunday night, so I have another day to troubleshoot before I hear what their professional opinion is.
 
  • Like
Reactions: Blasirl

·
Registered
Joined
·
103 Posts
Discussion Starter #8
It happens right at the spot you'd normally see power drop because of the intake manifold tumblers. Interesting.
The plot thickens lol.
 
  • Like
Reactions: Blasirl

·
Registered
Joined
·
74 Posts
BNR is moving to a new shop this week and weekend- So may take a bit longer for a response. I had the same dip at the same rpm. It went away after I played with different plug gaps... i'm now at .022 with ac Delco, my car didn't like the same gap on NGK's 7's. But then I'm GTXed and running the coil pack upgrade. What boost psi are you running?

first run: 500miles on the tune
second run: about 25miles

The log I sent BNR was after a troubleshooting attempt, resetting the tune, and putting about 40 miles on the car. It seems too consistent for me to consider blow out. Especially when the dip in power only occurs for a brief moment, consistently at the same rpms as the second dyno pull. I am picking up a set of colder plugs today BKR8EIXs. I will install them, put some miles on the tune, and see if it continues it. Normally, BNR won't respond to my emails until Sunday night, so I have another day to troubleshoot before I hear what their professional opinion is.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #11
BNR But then I'm GTXed and running the coil pack upgrade. What boost psi are you running?
Im on the stocker and I get an initial spike of 240-245kpa. Then the boost tapers and holds around 227-235kpa until I shift at 5300rpms.


I had the same dip at the same rpm. It went away after I played with different plug gaps.
What plug are you using (part number)? I will play with the gap a tad when I put in the BKR8s today. Thanks!
 

·
Administrator, Resident Tater Salad
Joined
·
16,992 Posts
I would suspect the tune's slightly too aggressive for the .028" gap @ high RPM. Try .025" on the stockers, or see what the BKR8 can do.

The stock turbo (combined w/ intake manifold runners) runs out of breath @ 5500 RPM anyway. From there on up, you'll typically see a sharp taper of power to redline.
 

·
Registered
Joined
·
74 Posts
I'm running the Stock AC Delco's right now. Everyone has different experiences with different plugs and gaps. It's a matter of just testing what works best for you. I have a set of BKR8s in shipping right now.. So I'll see how my car like them.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #14
Well the log revealed that my boost pressure is at 17psi when it should be at 21psi. BNR says it could be a weak wastegate spring or a possible boost leak. I installed a Forge bpv last week so perhaps I'll start there. I haven't messed with anything else, boost wise, but it wouldn't hurt to search for anything out of the ordinary.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #15
Perhaps I need to be running the yellow spring on the tune I'm running as well?
 

·
Registered
Joined
·
74 Posts
Perhaps I need to be running the yellow spring on the tune I'm running as well?
I would leave the spring alone- Cody is running 29-30psi on that green spring that I comes with I believe. Just start checking all connections and look for rips and stuff like that. I heard you can make a boost leak tester pretty easy for like 15 bucks.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #17
I went out and watched the MAP reading on the hand held BNR device and it would read between 235-245kpa during the two WOT pulls I did. That should be 20-21psi, right? All the way up to 5200-5300rpm. I'll make a boost tester at work to check for leaks and gap the factory plugs to 0.025" tomorrow and install them in place of the BKR7s. Then I'll do a global reset and drive around for a 100 or so miles before seeing if the fluctuation goes away.
 

·
Registered
Joined
·
103 Posts
Discussion Starter #18
So the boost leak test resulted in showing that everything is holding pressure good except for the PCV valve in the intake manifold. REALLY?!? With only 4k miles on the car? I can hear it pushing a small amount of pressure through it. Maybe it's from crank case pressure building during the leak test but it looks like I'll be installing Titan's PCV fix tomorrow now. lol!
 

·
Registered
Joined
·
29 Posts
i will chip in my two cents, but i experienced this yesterday.
Was driving around and i usually never do WOT pulls, but decided to do one.
Keep in mind i am not tuned.
Running BKR7E gapped at .028
Carpulls good all the way,but as soon as it hit 5,5k rpms, the car just drops power instantly, like blowout, and you can hear the exhaust rumble, like misfire.

Tried it multiple times and my wife noticed it also. As soon as it hit 5,5k rpms, BOOM!
Car looses power, you hear misfire in the exhaust and car boogs down instantly.
 
1 - 20 of 26 Posts
Top