Engine dies after high rev in neutral

[spyro512]

Yep,

So this is the thing. It's a Suzuki GSXR600 2k5 engine with a M84.

If I open the throttle to make it rev to 11-12000rpms, when I let the throttle go back to idle, it will just die. It becomes a problem when I shift down near to a massive curve, the engine dies and thanks to the inertia I just release the clutch and the engine will start again, but I lose time with this (it's a racecar).

No ref/sync problems, seems like just a tuning issue.

What compensation should I use? I thought of Deccel clamp but I actually don't know if it dies because there's too much or too less gasoline.

Thanks!

[stevieturbo]

It'll be down to idle control and your idle tuning for the most part

Are you using some form of idle control ?

Have you an overrun fuel cut of any sort enabled ?

[spyro512]

None of them...

[stevieturbo]

Maybe you should then.

And datalog to see exactly what is happening

[AlanB]

Data logging would be very helpful, or a copy of your map.

You shouldn't need idle control on a racing motorcycle, just set the throttle stop to give a fast idle speed (1500-2000rpm) using the mechanical adjuster screw. I can't remember if that model had 2 x stepper motors on the throttle body, if it did then one is for idle control (the one that isn't attached to the secondary butterflies), you ought to make sure this is closed so that all air is controlled via the throttle stop. You can do this by removing the stepper plunger and manually winding it out until the air holes are covered.

[spyro512]

Maybe you should then.

And datalog to see exactly what is happening

Fuel overrun cut for a racecar? Is it really a good idea? We don't care about consumption that much.

And idle control implies a servo controlling the throttle, right?

[spyro512]

Data logging would be very helpful, or a copy of your map.

You shouldn't need idle control on a racing motorcycle, just set the throttle stop to give a fast idle speed (1500-2000rpm) using the mechanical adjuster screw. I can't remember if that model had 2 x stepper motors on the throttle body, if it did then one is for idle control (the one that isn't attached to the secondary butterflies), you ought to make sure this is closed so that all air is controlled via the throttle stop. You can do this by removing the stepper plunger and manually winding it out until the air holes are covered.

Can't upload a copy of the map now, but in a few hours I will.

Idle is set around 3400rpm but intake is not stock. The intake trumpet is just 2cm wide (FSAE car) and we don't know how to achieve a lower idle. We didn't manage to get the engine at idle with a TPS below 15%. I think that a TPS below 15% is just too little air because it dies and even if I tried tuning it I didn't get to get it. Now it's set at 18.

[AlanB]

That idle speed and those throttle openings sound very wrong.

Are you using stock throttle bodies? If you are then you should expect a throttle position of approximately 2% to give an idle speed of 2000-2500rpm. The intake trumpet length will not affect idle speed.

Have you set the open and closed throttle positions in the ECU?
Have you checked the idle stepper motor position like I suggested?

[spyro512]

That idle speed and those throttle openings sound very wrong.

Are you using stock throttle bodies? If you are then you should expect a throttle position of approximately 2% to give an idle speed of 2000-2500rpm. The intake trumpet length will not affect idle speed.

Have you set the open and closed throttle positions in the ECU?
Have you checked the idle stepper motor position like I suggested?

It's not the length, it's 2cm wide. All the air flow goes through a pipe which is just 2cm wide. The amount of air is much much less than the stock intake.

We removed the idle stepper motor and yes, the TPS is correctly calibrated.

I can provide you the .e35 file and a video if needed.

[stevieturbo]

Maybe you should then.

And datalog to see exactly what is happening

Fuel overrun cut for a racecar? Is it really a good idea? We don't care about consumption that much.

And idle control implies a servo controlling the throttle, right?

Not saying you have to, but you could experiment. If for some reason the engine was getting overfuelled during the overrun, and you could not rectify this on the main table, then maybe it would be worth trying.

It's very unlikely that is the problem....or you'd assume it is unlikely as it's easily avoidable.