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Rotational Idle Settings

SLIXK

By SLIXK,
in R Series (R30, R31, R32, R33, R34)

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SLIXK

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On 1/18/2024 at 11:45 AM, Dose Pipe Sutututu said:

You're better off enabling VCT from idle, and putting a timing hole into your zero demand ignition table

That would give you the lumpy idle you want, if you want to exaggerate it even more, reduce the lobe separation angle.

Rotational Idle sounds aids.

The video the guy posted shows him using those settings aswell.

niZmO_Man Grand Master

niZmO_Man

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On 19/01/2024 at 9:15 AM, GTSBoy said:

If I had 292° cams in my car I'd still be trying to tune the idle to be as smooth as possible.

Choppy idle is not "cool". It is an indication that things are not working as well as they could. You can bet your bottom dollar that a race team engineer, running an engine with massive cams, is not trying to tune it to make the idle worse, even if it spends very little operational time at idle.

It's not 1970 any more. We can control this shit better.

 

yeah but he wants the brap brap brap brap brap

Murray_Calavera Mentor

Murray_Calavera

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On 1/18/2024 at 10:42 PM, Dose Pipe Sutututu said:

Wouldn't say it sounds good, however it sounds ok lol.

I think it sounds really good actually lol. 

I turned my VCT on at idle and dropped the timing to 0, my car didn't sound anything like that and I was very sad :(

joshuaho96 Veteran

joshuaho96

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21 hours ago, GTSBoy said:

If I had 292° cams in my car I'd still be trying to tune the idle to be as smooth as possible.

Choppy idle is not "cool". It is an indication that things are not working as well as they could. You can bet your bottom dollar that a race team engineer, running an engine with massive cams, is not trying to tune it to make the idle worse, even if it spends very little operational time at idle.

It's not 1970 any more. We can control this shit better.

 

This is the engineer's way of thinking about it. Unstable idle means low combustion stability, means misfires which means wasted fuel and an engine that will stall easily. But a lot of people hear it and think 1960s cammed muscle cars, so people want to replicate that sound in a modern car. ¯\_(ツ)_/¯

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

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7 hours ago, Murray_Calavera said:

I think it sounds really good actually lol. 

I turned my VCT on at idle and dropped the timing to 0, my car didn't sound anything like that and I was very sad :(

Time to reduce the lobe separation angle, install an adjustable exhaust cam gear lol

 

22 minutes ago, joshuaho96 said:

Unstable idle means low combustion stability,

Some merit to this, you'll have better cylinder scavenging down low, more low down torque just a terrible idle. Nissan did combat this by only advancing the intake only once you were outside of the idle conditions.

 

joshuaho96 Veteran

joshuaho96

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1 hour ago, Dose Pipe Sutututu said:

Time to reduce the lobe separation angle, install an adjustable exhaust cam gear lol

 

Some merit to this, you'll have better cylinder scavenging down low, more low down torque just a terrible idle. Nissan did combat this by only advancing the intake only once you were outside of the idle conditions.

 

Is that how that works? When I think about it the idle condition is where intake vacuum is high so you'll get a lot of internal EGR, which is what is causing idle lope. 

SLIXK Collaborator

SLIXK

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3 hours ago, joshuaho96 said:

This is the engineer's way of thinking about it. Unstable idle means low combustion stability, means misfires which means wasted fuel and an engine that will stall easily. But a lot of people hear it and think 1960s cammed muscle cars, so people want to replicate that sound in a modern car. ¯\_(ツ)_/¯

Technically it turns off a cylinder with rotational idle , which means technically  less fuel used at idle 

GTSBoy Grand Master

GTSBoy

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25 minutes ago, SLIXK said:

Technically it turns off a cylinder with rotational idle , which means technically  less fuel used at idle 

That might be your mental model, but an engine that has the rpm jumping up and down and all the control actions that the ECU thinks it has to perform in order to repair that shitty condition will very likely result in an increase in fuel consumption. Not to mention all the other negative consequences of unstable combustion, which includes incomplete combustion which can lead to both sooting (and hence carbon build up in places where you don't want it) and cylinder wall washing.

But then that's why engineers design engines, and not everyone else.

  • 1 month later...
Murray_Calavera Mentor

Murray_Calavera

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8 hours ago, SLIXK said:

So it’s all done now, and idk what you’re all crying about but it sounds sick irl, camera doesn’t really do it justice. But I’ll record it when I get a good camera lol

I'm keen to hear it :)

joshuaho96 Veteran

joshuaho96

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21 hours ago, SLIXK said:

So it’s all done now, and idk what you’re all crying about but it sounds sick irl, camera doesn’t really do it justice. But I’ll record it when I get a good camera lol

Pulling fuel from one cylinder isn't as bad as running cams that generate idle lope but it'll still kind of be all over the place. Transient fuel modeling is usually one of the hardest parts to get right. I don't think it'll hurt your engine but it will probably be less efficient than a smooth idle. Don't use ignition cut rotational idle, raw fuel in a cylinder really is not good for things.

Murray_Calavera Mentor

Murray_Calavera

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42 minutes ago, SLIXK said:

Camera doesn’t do it justice but it sounds mint and about 3x better in person, camera doesn’t catch the bass and it sounds tinny on camera.

IMG_7610.mov 94.1 MB · 0 downloads  


 

Sounds good to me! 

When you say it sounds tinny, I'm guessing that's when your playing it back on your phone? 

Sounds great on the gear I'm using to listen to it.

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SLIXK Collaborator

SLIXK

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8 hours ago, Murray_Calavera said:

Sounds good to me! 

When you say it sounds tinny, I'm guessing that's when your playing it back on your phone? 

Sounds great on the gear I'm using to listen to it.

Yeah, it’s only tinny when you play back on the phone, I’ve got a straight pipe 3”  so In person it sounds proper.

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