Lean spool for turbo freaks

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ptuomov
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Re: Lean spool for turbo freaks

Post by ptuomov » Wed May 16, 2018 9:15 pm

3pedals wrote:
Wed May 16, 2018 6:40 pm
My car was a turbo stick combo before I decided to put the converter in it.
That setup had boost threshold of ~3100rpm.
No amount of timing/fuel tuning could lower that, without employing a rolling anti-lag. I simply didn't stand on it unless I was above that rpm
This is where we were with the previous iteration with the same turbos and a little more restructure exhaust:

viewtopic.php?t=35531&start=30#p506574
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by ptuomov » Thu May 17, 2018 12:21 pm

By the way, there's been a question about whether the intake resonance tuning matters for turbo cars. I can confirm that, with my car at least, the intake resonance tuning is critical for the spool up rpm. The car has an active resonance intake, which can alternate it between single plane and dual plane intakes. The dual plane mode is tuned to produce peak torque at 3100 rpm and the single plane is tuned to produce peak torque at 4200 rpm, this is stock normally aspirated configuration. With the intake set up in a constant mode as a single plane intake, the spool up is at about 400-500 rpm later, compared to the dual mode. What this means in practice is that retaining the active resonance logic allows me to make boost 400-500 rpm earlier or, alternatively, go up one A/R turbine ratio and spool at the same rpms but with lower exhaust back pressure at 6000 rpm. The single plane mode flows slightly better at 6000 rpm and allows the turbo to work little less hard, so running in just the dual-plane configuration isn't ideal either.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by Big Al » Thu May 17, 2018 2:52 pm

Look at this dyno.
Green is before "Turbostart" with ordinary ignition.
Blue is with "Turbostart" with lowered ignition at 5000rpm. (Ignore the +7000rpm valve float.)
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Re: Lean spool for turbo freaks

Post by ptuomov » Thu May 17, 2018 2:55 pm

Big Al wrote:
Thu May 17, 2018 2:52 pm
Look at this dyno.
Green is before "Turbostart" with ordinary ignition.
Blue is with "Turbostart" with lowered ignition at 5000rpm. (Ignore the +7000rpm valve float.)
Thank you.

What was the acceleration rate on the dyno? Is my guess correct that the dyno was accelerating pretty fast and that allows you to trade off torque below 5000 rpm to faster spool and more torque above 5000 rpm?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by Big Al » Thu May 17, 2018 3:08 pm

I have actually no idea. It was a roller "without" (it have but did not use) brake on this one ... but even on a eddycurrent dyno with fixed acceleration rate the result is the same.
Turbo makes more boost at spoolup = more hp
If used right the top end power is higher too because of less heat loss in the exhaust (manifold) with more heat added earlier (5000rpm).

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Re: Lean spool for turbo freaks

Post by ptuomov » Thu May 17, 2018 10:08 pm

Big Al wrote:
Thu May 17, 2018 3:08 pm
I have actually no idea. It was a roller "without" (it have but did not use) brake on this one ... but even on a eddycurrent dyno with fixed acceleration rate the result is the same.
Turbo makes more boost at spoolup = more hp
If used right the top end power is higher too because of less heat loss in the exhaust (manifold) with more heat added earlier (5000rpm).
Let me rephrase. Suppose that you would hold 5300 rpm for five minutes with either of the calibrations. (Probably not a good idea, but please just humor me with this thought experiment.). Would the “turbostart” calibration still make more power at the end of that five minute dyno load than the “non-turbostart” calibration?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by 3pedals » Thu May 17, 2018 10:37 pm

Lol

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Re: Lean spool for turbo freaks

Post by gruntguru » Fri May 18, 2018 12:47 am

On the thermodynamics of adding excess fuel. No it won't make more energy available to the turbine. The fuel vapor adds volume flow to the exhaust but reduces exhaust temperature and therefore internal energy. 20% extra fuel is only increasing exhaust massflow by less than 2%

Big Al.
1. Does "turbostart" improve acceleration times from speed 1 to speed 2?
2. Does "turbostart" improve acceleration times from point to point (starting at speed 1)?
Last edited by gruntguru on Fri May 18, 2018 12:52 am, edited 1 time in total.

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Re: Lean spool for turbo freaks

Post by gruntguru » Fri May 18, 2018 12:51 am

ptuomov wrote:
Mon May 14, 2018 4:42 pm
This is the closest they've gotten so far with the AFRs in gasoline turbo engines:

Image
Image: Ecoboost 3-cylinder direct injection gasoline engine (lambda map)
Credit: Ford

For example, the Ford Ecoboost 3-cylinder engine runs with stoichiometric air-fuel ratio for idle to medium engine speed and complete load range, and with rich air-fuel mixture at high speed and load. The reason for which it runs with rich mixture at high engine speed and load is engine cooling. The additional fuel (which will remain unburnt) is injected to absorb heat (through evaporation), reducing this way the temperature in the combustion chamber.
Great graph!

Formula 1 has gone further with AFR - at least lambda 1.4 at peak power - maybe much leaner!

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Re: Lean spool for turbo freaks

Post by ptuomov » Fri May 18, 2018 7:42 am

gruntguru wrote:
Fri May 18, 2018 12:47 am
On the thermodynamics of adding excess fuel. No it won't make more energy available to the turbine. The fuel vapor adds volume flow to the exhaust but reduces exhaust temperature and therefore internal energy. 20% extra fuel is only increasing exhaust massflow by less than 2%.
The additional mass is one thing, but I am interested in impact of the phase change from liquid to gas. This will lower the temperature and increase the pressure, like in a steam turbine. My question is what's the net impact? I think this is analogous to water injection into the combustion chamber of a gas turbine.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by Big Al » Fri May 18, 2018 12:16 pm

ptuomov wrote:
Thu May 17, 2018 10:08 pm
Let me rephrase. Suppose that you would hold 5300 rpm for five minutes with either of the calibrations. (Probably not a good idea, but please just humor me with this thought experiment.). Would the “turbostart” calibration still make more power at the end of that five minute dyno load than the “non-turbostart” calibration?
Not a good idea, the "turbo start" is only designed to operate at a single rpm and load point. So you have to choose gear for it (on a manual).

What you are after is another thing that I actually have made on my car. And that's to lower the ignition at "cruise speed" some degrees so you have to have more trottle to keep the same speed. Then you have more temperature in the exhaust manifold and turbo housing and you also have higher rpm at the turbo because of more energy is transferred to the exhaust side instead of to the combustion.
So the next time you floor it you have less turbolag and make boost quicker.
gruntguru wrote:
Fri May 18, 2018 12:47 am
Big Al.
1. Does "turbostart" improve acceleration times from speed 1 to speed 2?
2. Does "turbostart" improve acceleration times from point to point (starting at speed 1)?
Depends on the speeds or the points, if your speed or your point is lower/before the "turbo start" then yes. But if you start at the "turbo start" then it could be a no because it is only designed to be a dynamic "passing trough" ignition. Starting at like zero ignition probably is no good idea for acceleration ;)

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Re: Lean spool for turbo freaks

Post by ptuomov » Fri May 18, 2018 12:51 pm

Big Al wrote:
Fri May 18, 2018 12:16 pm
What you are after is another thing that I actually have made on my car. And that's to lower the ignition at "cruise speed" some degrees so you have to have more trottle to keep the same speed. Then you have more temperature in the exhaust manifold and turbo housing and you also have higher rpm at the turbo because of more energy is transferred to the exhaust side instead of to the combustion. So the next time you floor it you have less turbolag and make boost quicker.
I think this makes sense and I think I've got a handle on that. More generally, I am reasonably comfortable with these tuning ideas for all starting points where there's an excess of air flow available. For example, when cruising (as in your example). Or another example is during the brief period when up-shifting from high load and high rpms.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Lean spool for turbo freaks

Post by gruntguru » Sat May 19, 2018 1:39 am

ptuomov wrote:
Fri May 18, 2018 7:42 am
gruntguru wrote:
Fri May 18, 2018 12:47 am
On the thermodynamics of adding excess fuel. No it won't make more energy available to the turbine. The fuel vapor adds volume flow to the exhaust but reduces exhaust temperature and therefore internal energy. 20% extra fuel is only increasing exhaust massflow by less than 2%.
The additional mass is one thing, but I am interested in impact of the phase change from liquid to gas. This will lower the temperature and increase the pressure, like in a steam turbine. My question is what's the net impact? I think this is analogous to water injection into the combustion chamber of a gas turbine.
No the phase change does not improve turbine spool. The cooling cancels the increased volume flow. Gas turbines use water injection to decrease turbine inlet temperature, allowing higher PR and or heat (fuel) addition. The water has the added benefit of reducing compressor work and/or increasing compressor massflow by intercooling.

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Re: Lean spool for turbo freaks

Post by joe 90 » Sat May 19, 2018 7:13 am

It must be called "lean spool "for a reason?

If you're adding excess fuel it's not lean so therefore lean spool doesn't use excess fuel.

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Re: Lean spool for turbo freaks

Post by ptuomov » Sun May 20, 2018 9:18 am

joe 90 wrote:
Sat May 19, 2018 7:13 am
It must be called "lean spool "for a reason?
If you're adding excess fuel it's not lean so therefore lean spool doesn't use excess fuel.
So what’s your answer, does lean or rich spool the best in terms of maximizing acceleration?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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