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Driveability issues

Road Tuning

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Discussion and questions related to the course Road Tuning

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I am tuning a 2006 supercharged c6. How to make the car more smooth while driving it. Am using Hp tuners.

Is there a specific RPM range where it is not smooth? Is it just above the idle (what's called "tip-in" -- when you add more throttle)?

Is it too responsive (jerky), or not responsive enough (hesitation)? What type of transmission are you using? Does it happen at specific speed or load?

Yes, it happens from 1k rpm to 2k. It's kind of jerky. It's a grandsport manual transmission.

When I start to move the car it happens. Thank you

I have struggled trying to tune an LS3 with a manual transmission, in exactly this area. What seems to happen is a surge in torque quickly increases the engine speed and lowers the manifold pressure. This leads to a loss of torque and it quickly cycles back. The manual transmission seems to make this much worse than an automatic. It happens at 1200 - 2000 RPM (about 15-25 km/h - 10-15 mph).

I got the best results by trying to reduce the overall torque by reducing the timing at lower RPM. I was using a stand-alone ECU and interaction with the idle control was also a factor as this is just above the range where the idle control want's to pull the car into idle as the accelerator pedal goes to 0%.

To me this behaves like most race cars with tall gears and manual transmissions -- when driving slow through the paddock you just need to slip the clutch sometimes, instead of expecting to drive just above idle with a powerful engine and no load.

Hopefully someone more successful tuning this issue will chime in with some solutions.

Reducing the timing in the spark advanced table? Thanks for helping

the way i do is i use the idle timing value let say 20 and extend it to 1000rpm at low load

if its a large cam i would make the whole column from 0-1000rpm 20 degree, and slowly ramp up the timing,

but still at 1200rpm high load i would lower the timing to 18 and 16 at 1600rpm to reduce knock maybe lower without getting any surging (but i wouldnt flooring under 2000 rpm anyway)

try smoothing nearby cells they should all have the same upward trend, in stock tune the timing goes up and down alot between every other cell, timing should only increase as rpm does, make a datalog and find out what is the cylinder air mass the issue is at, i think it would be mostly around .4-.68g the timing would drop from 26-6 degree in stock tune and this would cause the issue

Bit of a long shot, but any chance the fuel shut-off is being triggered? Had a different make vehicle where I ended up disabling it because it was just where I would have the engine rpm for town driving in top gear and it was a bit sensitive to the very light throttle opening sometimes being reduced to the 'idle' position.

Thanks guys!

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