Severe lungeing at carpark

[ChrisW434]

Hey all,

The 34 GTT lunges violently if you touch the throttle at very low speeds (carpark), until you back off or throttle harder after the chassis has settled. I suspect the tune needs a little more work, but want to try some little haltech setting changes if possible to soften the hit when touching the throttle at walking pace. I suspect the remote mounted IAC (plaz top-half w/cable TB) may be partly ,or fully, to blame as the airspeed at that low rom and load could possibly be disturbed with a laggy remote IAC. 
The driveline has 1pce driveshaft and twin-plate clutch that "may" exaggerate the issue....
 

Does anyone have any thoughts, or have experienced this? 

What settings in the Haltech could soften the jerkiness? Say initial 0-2% throttle opening at less than 1200rpm..?

Thanks in advance!

[Kinkstaah]

I mean what you should do in this case is datalog and find out what is actually occurring in this state.

Is the car lunging because it's lean (Probably), or timing is doing weird things? Worth seeing what the ECU is actually attempting to do and then sorting it out from there.

These things aren't cammed V8's (ask me how I know) so it should be very smooth cruising around at 600rpm in gear. Once you're in gear, the clutch you have is taken out of the equation, as is your drive shaft, and diff. You're all dependent on the smoothness of the 6cyl up front, which should be very smooth.

This is going to require datalogging to determine what the ECU thinks is happening and better correlating it to what is actually occurring. It could be any of the very many systems throwing too much/not enough fuel and too much/not enough timing.

[ChrisW434]

40 minutes ago, Kinkstaah said:

I mean what you should do in this case is datalog and find out what is actually occurring in this state.

Is the car lunging because it's lean (Probably), or timing is doing weird things? Worth seeing what the ECU is actually attempting to do and then sorting it out from there.

These things aren't cammed V8's (ask me how I know) so it should be very smooth cruising around at 600rpm in gear. Once you're in gear, the clutch you have is taken out of the equation, as is your drive shaft, and diff. You're all dependent on the smoothness of the 6cyl up front, which should be very smooth.

This is going to require datalogging to determine what the ECU thinks is happening and better correlating it to what is actually occurring. It could be any of the very many systems throwing too much/not enough fuel and too much/not enough timing.

Yep, i agree thats the direction i should go in.
 

i forgot to mention something relevent; i asked the tuner to give it a chunky idle and to achieve that, the timing is different at zero-throttle. I reckon that may have something to do with it. As you say, datalogging would be the best way to check whats happening..

Cheers for the detailed response!

Edited August 17 by ChrisW434
More info added

[GTSBoy]

How big is the TB?

[ChrisW434]

10 minutes ago, GTSBoy said:

How big is the TB?

Hey there,

TB is 66mm, so nothing too large.
That initial very light tap (1%) on the throttle pedal sets off the crazy lungeing. It goes away if you let it settle or just throttle it more. Super annoying... its like the throttle is super touchy and the chassis starts reacting, possibly due to the tune in that map area..

Edited August 17 by ChrisW434

[Kinkstaah]

When you say you wanted the idle to be 'chunky'... I assume you meant you want it to be choppy and cammy like a V8. (or similar).

The thing about that is, well, the engine is running chunky because effectively it is running like shit. It doesn't really matter when the car isn't moving, because the transmission and wheels aren't connected to the 'chunky' or 'lumpy' engine.

But when you connect that 'chunky' or 'lumpy' idle to the wheels via a clutch, the motor is still running like chunky lumpy mess, and bucking and surging is what happens all the way through the drivetrain, because... the engine is still running like shit.

The root cause for this is big cammed V8's sacrifice running at low RPM so they run better under load. They aren't choppy and angry sounding at high RPM.. and they aren't sounding 'bad' up there either.

Haltechs are pretty good units. It's entirely possible to have parameters set for idle based on road speed. So you can have your lumpy choppyness at 0kmh, and a regular idle at 1kmh if that is what you want. This is a poster child for having access to your own ECU to see what your car is doing, but you can then obviously make a whole bunch of problems worse if you're not too familiar with what you're changing.

Also, our friend antilag/pops and bangs is achieved by having fuel set to YES and timing set to "Something different" at zero throttle. Usually way, way different, i.e -15deg of timing. If the car is in a map it shouldn't be in because a parameter is slightly off, or a sensor isn't quite calibrated perfectly, well, um, you could have unexpected consequences like this.

Imagine how the car would attempt to accelerate if if the engine is mid-mid pops and bangs and misfires.

[ChrisW434]

Yes, without looking at it, it appears the 0kph timing condition is something i should look at. 
The "lungeyness" was there before the last tune when the 'ghost-cam' got installed, but it's much worse now. I reckon that sounds like a big part of the issue, if not 100%. 
i'll bust out the laptop and spend some time looking through the settings, and make small changes via trial/error. 
 

thanks again for the detailed post 👍🏻

[MBS206]

Are you in 1st gear with this "lungeyness" occuring? Just idling around the car park and then tap the throttle?

[ChrisW434]

10 minutes ago, MBS206 said:

Are you in 1st gear with this "lungeyness" occuring? Just idling around the car park and then tap the throttle?

Yeah mate, less than 1% throttle. I drove it again today, and i'm pretty convinced its the 'ghost cam' idle timing being present as i drive...

[Dose Pipe Sutututu]

Sounds like you need an e-throttle, better control than the cable stuff.

Brap cam, A/C, big turbo, etc. will have superior idle control, low rpm/speed maneuvering.

I have brappy cams (I know I know) and I have none of the problems you've described.

Sounds more tuna related than anything else.

[ChrisW434]

2 hours ago, Dose Pipe Sutututu said:

Sounds like you need an e-throttle, better control than the cable stuff.

Brap cam, A/C, big turbo, etc. will have superior idle control, low rpm/speed maneuvering.

I have brappy cams (I know I know) and I have none of the problems you've described.

Sounds more tuna related than anything else.

I agree with DBW benefits, i tried to "keep it simple" with cable when i bought the parts a few years ago, but it has made tuning for results more complex!
Should have gone DBW lol...

[Dose Pipe Sutututu]

Record a video and pop it on YouTube and drop the link back here.

[MBS206]

21 hours ago, ChrisW434 said:

Yeah mate, less than 1% throttle. I drove it again today, and i'm pretty convinced its the 'ghost cam' idle timing being present as i drive...

Put the car in second gear instead of 1st and try again.

Lots of cars, especially cable drive when in first are very touchy/jerky when you first touch the throttle. The jerkyness can also cause your foot to move ever so slightly, and on a cable setup, can be varying the throttle very minutely, but that's a large change in air flow for low speed.

2nd gear takes a lot of the 'jerk' away.

 

If second gear doesn't make it drive able, you need to sort of the "ghost cam" tune around idle. First test would be removed it entirely and see if that eliminates the issue.

[TurboTapin]

If you send me your tune, I'll take a look and let you know if anything funky stands out. 

Edited August 19 by TurboTapin

[ChrisW434]

15 hours ago, MBS206 said:

Put the car in second gear instead of 1st and try again.

Lots of cars, especially cable drive when in first are very touchy/jerky when you first touch the throttle. The jerkyness can also cause your foot to move ever so slightly, and on a cable setup, can be varying the throttle very minutely, but that's a large change in air flow for low speed.

2nd gear takes a lot of the 'jerk' away.

 

If second gear doesn't make it drive able, you need to sort of the "ghost cam" tune around idle. First test would be removed it entirely and see if that eliminates the issue.

Yeah i do that sometimes, less gear leverage helps. I played with the tune (made it richer at low rpm/light throttle) and that helped.

[ChrisW434]

2 hours ago, TurboTapin said:

If you send me your tune, I'll take a look and let you know if anything funky stands out. 

Thanks for the offer, i may just do that 👍🏻 i made good progress by adding 5% fuel to the low rpm/light throttle part of the fuel map and that made a good difference.

i turned off coasting fuel cut and helped drivability when rolling also. I may play around with that a bit too.

 

i'm at work for a week but if i don't have any luck when i'm on break, i'll hit you up for a look at the tune.

 

cheers! And thanks

[joshuaho96]

Just now, ChrisW434 said:

Thanks for the offer, i may just do that 👍🏻 i made good progress by adding 5% fuel to the low rpm/light throttle part of the fuel map and that made a good difference.

i turned off coasting fuel cut and helped drivability when rolling also. I may play around with that a bit too.

 

i'm at work for a week but if i don't have any luck when i'm on break, i'll hit you up for a look at the tune.

 

cheers! And thanks

At very low RPM you should not be enabling DFCO, the risk the engine stalls is high and it will cause very jerky behavior like this.

[TurboTapin]

7 minutes ago, ChrisW434 said:

Thanks for the offer, i may just do that 👍🏻 i made good progress by adding 5% fuel to the low rpm/light throttle part of the fuel map and that made a good difference.

i turned off coasting fuel cut and helped drivability when rolling also. I may play around with that a bit too.

 

i'm at work for a week but if i don't have any luck when i'm on break, i'll hit you up for a look at the tune.

 

cheers! And thanks

6 minutes ago, joshuaho96 said:

At very low RPM you should not be enabling DFCO, the risk the engine stalls is high and it will cause very jerky behavior like this.

Set your decel fuel cut to disable 1000rpm before your idle and you'll be fine with it on. 

[ChrisW434]

2 minutes ago, TurboTapin said:

Set your decel fuel cut to disable 1000rpm before your idle and you'll be fine with it on. 

Sounds good, i'll try that

[ChrisW434]

10 minutes ago, joshuaho96 said:

At very low RPM you should not be enabling DFCO, the risk the engine stalls is high and it will cause very jerky behavior like this.

Yep no worries, cheers for the tip