New Tune issue or Driver Mod issue?

[BlindGUYnAR]

2008 GT Vert: UDP, DR NA-NSR Cams, Airaid CAI, CMDP, BBK shorties, HI-FLOW cats, axle backs, and Alum DS. Just normal run of the mill bolt-ons.

So i've been tuned by AM for a while, but since i bought and installed the Detroit Rocker Cams i thought i'd try Brenspeed for a new tune to compare companies since is hear mixed feelings on AM. Well decidedly to one side and not very mixed really!

Not Bashing AM just thought i'd try something new and since it's Brenspeed's cams they might know more about them as far as tuning goes.

The issue is now i'm getting a lot of bucking in 1st and some in 2nd. I mean violent bucking. Whiplash territory actually. i'm not even in the clutch when it starts. i'll have been out of the clutch for 7-900 rpm's before it starts always in the 3-4k range is where it starts.

Straight line drag race driving is fine and really light 'baby' driving is fine, but if during normal driving i don't shift at 2900+ RPM into 1st or 2nd i need to get a neck brace.

i asked them about it and was told to clean the TB. Admittedly i just installed the TB with this tune. The TB was spotless though so it isn't in need of a cleaning. They offered to pull out half the throttle response and said the amount they add "wasn't for everyone". i took that to kinda mean i'm a shitty driver and i need to learn how to drive my car.

Unfortunately I don't have an AM tune with the TB to compare with yet, but it is ordered and i never had the bucking with AM tunes. I'm not sure why i didn't order it before, but well i just didn't. Once i get it i can say if this is a TB issue or not.

TB is FRPP 62mm by the way and it seems to function fine. (I know i get no real benefit now from this, but it fits into future plans. Plans rhym with "flurbo")

So should i go back to manual driving school or is it a tune issue with way to much throttle response? My laptop died a few weeks ago so i can't datalog right now to see what they are commanding in the tune.

The Brenspeed tune is for sure the faster tune between the two without question, but i actually do believe the CAM's sound better with AM tune. More loppy idle.

i can't afford the chiropractor bills with the Brenspeed tune and i'm afraid if they pull out half the TR i'll be exactly where i started with an AM tune.

So is this a Driver Mod issue or a Tune needing Revision? Will 1/2 the TR being removed affect the faster tune in straight line acceleration? The TR just changes the points the throttle blades are open for a given pedal position. But Hammered is 100% either way so it should have the same response hammered with 1/2 the TR right?

 

[eighty6gt]

Tune is knackered.

 

[702GT]

Tune is knackered.

Agreed.

The occasional cam buck from attempting to clutch out with 3.55 gears at idle rpms is tolerable, anywhere else isn't neccessary. My tuner had to spend a little seat time to iron out my cam buck with the thumpr's when I ran the 127020's. After that I had to really try to get it to buck on me. The only issue I had at 3k/rpm was the hostile trumpet of the Pypes M80 MMS. It was like a banshee shriek amplified by lobe separation.

There's no need for cam buck, the tuner needs to work on your drivability.

Edit: As far as cam chop at idle, it's likely up to where your target idle rpm is set in the tune. I had a "parking" tune set up for when I went to car shows, the target idle was set to 600. People would just assume there was a big block under the hood, not a 281. 850 was my normal idle, not as agressive of a cam thump but I wasn't putting the motor mounts on spin-cycle either, better for the accessories.

 

[Dino Dino Bambino]

TB is FRPP 62mm by the way and it seems to function fine.

Did you tell Brenspeed you have a 62mm TB when you requested the tune?

 

[CJ-]

I'd check your intake tube and filter and MAF housing for leaks or separation. I had the same issue with bucking in the 3000 and lower RPM's, turned out my JLT S3 airfilter had gotten pulled off the intake tube by the heat shield and tilt of the engine under hard acceleration.

 

[BlindGUYnAR]

Did you tell Brenspeed you have a 62mm TB when you requested the tune?

Yes

 

[BlindGUYnAR]

I'd check your intake tube and filter and MAF housing for leaks or separation. I had the same issue with bucking in the 3000 and lower RPM's, turned out my JLT S3 airfilter had gotten pulled off the intake tube by the heat shield and tilt of the engine under hard acceleration.

I'll check that for sure. i'd think unmetered air like that would through a lean code and also occur when i tryed full on drag race 0-90 pull, but since the symptoms were similar to yours it's sure worth a try .

 

[CJ-]

I'll check that for sure. i'd think unmetered air like that would through a lean code and also occur when i tryed full on drag race 0-90 pull, but since the symptoms were similar to yours it's sure worth a try .

You'd think it would run leaner but my theory is the extra unfiltered air that is whizzing between the air filter and the intake tube is creating extra turbulence, which the MAF sensor is picking up and assumes that extra whizzing sound means way more air is entering than actually is. So in turn the ECU provides extra fuel to match that extra air and thus causing bucking or sudden and unexpected bogging down of the engine due to the mixture being overly rich.


Think of the MAF sensor as a Microphone, i know its not a mic, but it sorta acts like one when air filters aren't seated properly and air starts to whiz around the air filter, the MAF "hears" more sound although the nearly same amount of airflow is present.

I've had this happen to my s197 GT like I mentioned earlier, also on 2 other cars, a 97 Porsche Boxtser who's air filter track hadn't been pressed into the air box completely and on a 2001 Eclipse that had an air filter that wasn't seated in the air box correctly and air was being sucked in through the edges of where the 2 air box pieces snap into each other.

 

[BlindGUYnAR]

Looked everything over and can't find any leaks.

I got and installed the updated BAMA tune and it doesn't jerk at all. We'll see what Brenspeed sends tomorrow. The BS tune is so fast though I hope they can figure it out cause I like the power it made just without the neck injuries.

 

[CJ-]

I dont have either of those tuners so im not sure what parameters your able to customize but you should take a look at what the custom parameters are set to on both tunes... that might provide the answer or a better idea as to what could have caused the bucking.

 

[07 Boss]

The throttle response might help. I have had tunes with some really aggressive throttle settings. they do this to make their tunes seem faster by ramping up the throttle response. The problem with too sensitive a throttle is once it bucks it sets of a reaction that makes you actually oscillate the gas pedal and increases the bucking. Not saying this is the issue but you have to rule it out with the new tune. I have had many of my tuners tone down the throttle response.

 

[BlindGUYnAR]

Well Brenspeed sent me the revised tune and it no longer bucks, but it also lacks everything that was fast about the before version. Well that was $95 wasted. I'd run the stock tune over that revised one. Dropping the clutch at 4K barely even chips the tires. The engine stalls nearly right away. Weak. It's almost like they made it slow on purpose or something? Yes TC was off.

The AM tune is back in and running fine. I'd bet the AM tune is a second faster in 1/4 mile vs. the BS tune.

I'd call them and ask for another revision, but they were kind of clear they were a one a done type service for revisions. It's kind of funny that AM knows more about tuning their cams than they do and I just payed $95 for that lesson.

Anyhow I'll be buying all my FI stuff within the next month and had planned to travel there for Dyno tuning and maybe source some of the parts from them as well. Doubt those plans will stay intact with the results of this test.

This thread has fullfilled its purpose so feel free NOT to comment further. Thanks.

 

[ZmanM3]

Sounds like you had the cold start issue. Did the bucking get better when the engine got up to engine temp or was it always present?