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Dyno result for the risky business Porsche

General engine tech -- Drag Racing to Circle Track

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n2xlr8n
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Re: Dyno result for the risky business Porsche

Post by n2xlr8n » Sat Aug 03, 2019 6:01 am

Wow. Fantastic boost response.

I bet driving it will be an exercise in throttle discipline.
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Re: Dyno result for the risky business Porsche

Post by ptuomov » Sat Aug 03, 2019 8:41 am

n2xlr8n wrote:
Sat Aug 03, 2019 6:01 am
Wow. Fantastic boost response.

I bet driving it will be an exercise in throttle discipline.
Thanks.

This is a bit of an R&D setup in that the turbos are a little bigger than what one would ideally have for a pure street car running on pump gas and about 8.5:1 compression. The reason for running these larger turbos was so we can have some fun on race gas, too. And learn what happens at higher cylinder pressures and rpms.

With a little bit smaller turbos and the plenum resonance spaced to a little lower rpms, you could get that about 700-750 rwhp out of it on pump gas with the turbos coming on line maybe 500 rpm earlier?

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Re: Dyno result for the risky business Porsche

Post by ptuomov » Wed Aug 07, 2019 5:10 am

About tuning a pump gas turbo engine

I’m on a train in Europe with a high quality Wi-Fi and have some time to write about tuning under boost. There is a single graphical figure that I think explains the whole turbo tuning issue, at least on pump gas. Let me know if you think I’m missing something.

With turbos, one has in most cases an unlimited amount of high rpm air mass flow available. The only case in which one is air-flow limited is the compressor flow being chocked as the compressor wheel tips travel at sonic speed. At compressor choke, further shaft speed increases no longer increase mass flow thru the compressor. We are currently only at about 70% of the max mass flow (if my memory servers me right) so none of the tuning issues are really about more air flow. More air flow can be had simply by a turn of a screw.

There are limits, however. The two limiting factors are:

(1) the knock limit, where knock means a combustion that starts normally but then temperature and pressure lead to abnormal combustion in the form of knock or detonation. This can be detected by the ancient Porsche 928 S4 EZ-K ignition computer in its stock form.

(2) the pre-ignition limit, where pre-ignition means the charge igniting before the spark. This is not detectable by EZ-K, unless it also leads to detonation and even then it may be attributed to the wrong cylinder. The main proxy variable that is easily measurable indicator of high steady-state likelihood of pre-ignition is the exhaust gas temperature. Conditions that lead to pre-ignition are associated with high exhaust gas (and cylinder head) temperatures. When pre-ignition starts, the EGT may suddenly drop, complicating the issue. The conditions associated with pre-ignition are also associated with burned exhaust valves and turbine blades.

Given the fuel, rpm, and air-fuel mixture conditions, the tuning window amounts to something like this Mahle graph:

63A4A178-9EA9-4E69-B963-72442D733172.jpeg

The black BMEP curves denote constant torque, so more torque means moving to upper right to another, higher BMEP curve. The x-axis is the spark advance and the y-axis is the boost pressure. 100 kPa is about one atmosphere. As one would expect, more spark advance and more manifold pressure lead to higher torque. In this Mahle test engine run on pump gas and within its tuning window, four degrees of additional spark advance amount to as much torque as 1.5 psi of additional boost does.

The tuning window lives between a rock and the hard place. The rock on the upper right is the detonation limit. Additional boost and/or additional spark timing will move the engine to the knock area in the graph, leading to detonation. The hard place on the upper left is the pre-ignition limit. Too much ignition retard will lead to higher EGT which will cause (or at least be associated with) pre-ignition and burned exhaust valves.

As the boost is increased, the rock and the hard place will converge, leaving no safe way to run the engine at that or higher boost.

If one is using a knock management system that only adjusts the spark timing, one can safely run less boost than if one runs a knock management system that adjusts both spark timing and boost. This is because a knock management system that only adjusts spark timing may inadvertently retard the spark timing to the pre-ignition region of the graph. Therefore, with this kind of knock management system, the maximum safe boost is on the horizontal line in the graph at the level where the distance between the pre-ignition limit and the knock limit is a greater number of spark advance degrees than the maximum retard of the knock management system.

Contrast that with the knock management system that adjusts both boost and spark advance. Now, the operating point moves diagonally to down-left on the graph, avoiding the pre-ignition limit. Consequently, a turbo engine with such a system can be run much closer to the “tip of the spear”, i.e., the area where the pre-ignition and knock constraints converge.

The EZ-K system in the 928 S4 has a former kind of spark-retard-only knock management system. For one to maximize a pump-gas 928 turbo engine, one would need to capture the knock indicator from the EZ-K in real time and feed that as a signal to the boost controller. Alternatively, one could adapt a boost control system such as SAAB’s APC with its independent simple knock detection system that would independently detect knock and reduce boost.

Currently, I’m not aware of practical ways to detect pre-ignition in real time. (Measuring the size of the hole in the piston has a lag that is too long for real-time control logic.) If the conditions that are associated with the onset of pre-ignition, most importantly either abnormally high or abnormally low EGT, can be measured, one could rig a water injection system to selectively turn on in high risk situations. However, this is really not a great method, because the EGT sensors react slowly to changes in EGT. The pre-ignition detection and management is largely an unresolved problem in “downsizing” engines with high pressure turbocharging.

As far as I know, effective cooling of everything is the main preventive measure that can be taken to move out the pre-ignition limit out to the up and left. Oil control is another. Any other ways?
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Re: Dyno result for the risky business Porsche

Post by Kevin Johnson » Wed Aug 07, 2019 8:56 am

ptuomov wrote:
Wed Aug 07, 2019 5:10 am
...

Currently, I’m not aware of practical ways to detect pre-ignition in real time. ...
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Re: Dyno result for the risky business Porsche

Post by David Redszus » Thu Aug 08, 2019 1:12 am

As far as I know, effective cooling of everything is the main preventive measure that can be taken to move out the pre-ignition limit out to the up and left. Oil control is another. Any other ways?
Pre-ignition shows up as increased combustion pressure at an early crankangle.

It also reveals itself through elevated spark plug temperatures. A fast acting ring thermocouple, placed under the spark plug, serves as an early warning system for pre-ignition.

That requires eight sensors and an eight channel data recorder, just for spark plug seat temperatures.

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Re: Dyno result for the risky business Porsche

Post by ptuomov » Thu Aug 08, 2019 5:58 am

David Redszus wrote:
Thu Aug 08, 2019 1:12 am
As far as I know, effective cooling of everything is the main preventive measure that can be taken to move out the pre-ignition limit out to the up and left. Oil control is another. Any other ways?
Pre-ignition shows up as increased combustion pressure at an early crankangle.

It also reveals itself through elevated spark plug temperatures. A fast acting ring thermocouple, placed under the spark plug, serves as an early warning system for pre-ignition.

That requires eight sensors and an eight channel data recorder, just for spark plug seat temperatures.
Are there any aftermarket ECUs that can sense pre-ignition from the current draw (or resistance, or something else, I can’t hook up a toaster) of the spark plug during the ignition? That is, the spark plug behaving differently if the pressure is already high and rising during the spark plug firing?

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Re: Dyno result for the risky business Porsche

Post by David Redszus » Thu Aug 08, 2019 12:22 pm

ptuomov wrote:
Thu Aug 08, 2019 5:58 am
David Redszus wrote:
Thu Aug 08, 2019 1:12 am
As far as I know, effective cooling of everything is the main preventive measure that can be taken to move out the pre-ignition limit out to the up and left. Oil control is another. Any other ways?
Pre-ignition shows up as increased combustion pressure at an early crankangle.

It also reveals itself through elevated spark plug temperatures. A fast acting ring thermocouple, placed under the spark plug, serves as an early warning system for pre-ignition.

That requires eight sensors and an eight channel data recorder, just for spark plug seat temperatures.
Are there any aftermarket ECUs that can sense pre-ignition from the current draw (or resistance, or something else, I can’t hook up a toaster) of the spark plug during the ignition? That is, the spark plug behaving differently if the pressure is already high and rising during the spark plug firing?
Years ago, Bosch used ion sensing technology to determine correct spark plug heat range and ignition timing.
The ion sensing device was in a truck mounted chassis dyno and went to the race track to support race teams.
I don't know what became of it. Saab also had developed ion sensing ignitions.
I found the following abstract regarding ion sensing.
ABSTRACT
The cycle-to-cycle and cylinder-to-cylinder variations that occur in a spark ignited engine create the
opportunity for monitoring combustion in real time to provide useful benefits for engine control. Reduction of
variation and operation of the engine at closer-to-optimum conditions is possible if real time feedback of the
combustion process is available. An in-cylinder pressure sensor with pressure-based control algorithms is one
method of monitoring the combustion process. However, such a solution presents new challenges of an additional
cylinder penetration location, sensor packaging and added cost.

A substitute for the in-cylinder pressure sensor is a device which measures the flame conductivity,
commonly known as an ionization current sensor. It can be integrated with the spark plug in the case of SI
engines, or with the glow plug in the case of compression ignition engines. This paper presents a methodology
of data acquisition and processing which leads to the extraction, in real time, of the following parameters
critical for closed loop engine control: combustion phasing, knock detection and combustion stability.

The algorithms utilize a combination of various methods including crank-angle-aligned data extraction,
digital filtering of the ion sense signal, and neural-network-based ion signal interpretation.

A Delphi Ion Sense Development Controller (ISDC) is used for high-speed data acquisition and subsequent
real time combustion parameter computation. Our paper demonstrates key features and reports the performance
of ionization-current-based combustion sensing using engine data. Key combustion parameters,
generated by the ISDC on a combustion event basis, are sent to the engine controller via a Controller Area
Network (CAN) for closed loop individual-cylinder combustion control.

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Re: Dyno result for the risky business Porsche

Post by Kevin Johnson » Thu Aug 08, 2019 12:55 pm

David,
You and others can request the full text of that paper here:

https://www.researchgate.net/publicatio ... ne_Control

A subsequent paper on the topic cites it and is available directly in full text here:

https://www.researchgate.net/profile/Vi ... ngines.pdf

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Re: Dyno result for the risky business Porsche

Post by Leftcoaster » Thu Aug 08, 2019 3:51 pm

Optrand Products www.optrand.com/products.htm modify customer supplied spark plugs to incorporate a pressure sensor, data from which may permit a sophisticated ecu - - such as the AME chosen by mk e for his FrankenFerrari project? - - to modify fuel and spark maps to avoid engine damage

Optrand's recently released CA3004A Combustion Analyzer appears to use the same pressure sensors, and President & CEO Dr Marek T. Wlodarczyk claims

"Cylinder pressure measurements using the CA3004A provide analysis results for display and logging while the engine is operating. Instantaneous availability of combustion results facilitates the implementation of automated calibration and optimization" quote

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Re: Dyno result for the risky business Porsche

Post by Jokeri » Sun Aug 11, 2019 4:57 am

ptuomov wrote:
Thu Aug 08, 2019 5:58 am
David Redszus wrote:
Thu Aug 08, 2019 1:12 am
As far as I know, effective cooling of everything is the main preventive measure that can be taken to move out the pre-ignition limit out to the up and left. Oil control is another. Any other ways?
Pre-ignition shows up as increased combustion pressure at an early crankangle.

It also reveals itself through elevated spark plug temperatures. A fast acting ring thermocouple, placed under the spark plug, serves as an early warning system for pre-ignition.

That requires eight sensors and an eight channel data recorder, just for spark plug seat temperatures.
Are there any aftermarket ECUs that can sense pre-ignition from the current draw (or resistance, or something else, I can’t hook up a toaster) of the spark plug during the ignition? That is, the spark plug behaving differently if the pressure is already high and rising during the spark plug firing?
Well, there is Rusefi and apparently it can do ion sensing using Saab hardware.
https://rusefi.com/

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Re: Dyno result for the risky business Porsche

Post by ptuomov » Sun Aug 11, 2019 4:40 pm

Jokeri wrote:
Sun Aug 11, 2019 4:57 am
ptuomov wrote:
Thu Aug 08, 2019 5:58 am
David Redszus wrote:
Thu Aug 08, 2019 1:12 am

Pre-ignition shows up as increased combustion pressure at an early crankangle.

It also reveals itself through elevated spark plug temperatures. A fast acting ring thermocouple, placed under the spark plug, serves as an early warning system for pre-ignition.

That requires eight sensors and an eight channel data recorder, just for spark plug seat temperatures.
Are there any aftermarket ECUs that can sense pre-ignition from the current draw (or resistance, or something else, I can’t hook up a toaster) of the spark plug during the ignition? That is, the spark plug behaving differently if the pressure is already high and rising during the spark plug firing?
Well, there is Rusefi and apparently it can do ion sensing using Saab hardware.
https://rusefi.com/

That’s knock only, right, not pre-ignition? Can ion sensing be used to identify pre-ignition?

The aircraft fuel test uses a microphone-like sensor to listen for knock and a fast temperature sensor to detect preignition on defined test engine.

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Re: Dyno result for the risky business Porsche

Post by Jokeri » Wed Aug 14, 2019 12:49 pm

ptuomov wrote:
Sun Aug 11, 2019 4:40 pm
Jokeri wrote:
Sun Aug 11, 2019 4:57 am
ptuomov wrote:
Thu Aug 08, 2019 5:58 am


Are there any aftermarket ECUs that can sense pre-ignition from the current draw (or resistance, or something else, I can’t hook up a toaster) of the spark plug during the ignition? That is, the spark plug behaving differently if the pressure is already high and rising during the spark plug firing?
Well, there is Rusefi and apparently it can do ion sensing using Saab hardware.
https://rusefi.com/

That’s knock only, right, not pre-ignition? Can ion sensing be used to identify pre-ignition?

The aircraft fuel test uses a microphone-like sensor to listen for knock and a fast temperature sensor to detect preignition on defined test engine.
I don't know but if you can detect knock at early stage then you should be safe from pre-ignition too?

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Re: Dyno result for the risky business Porsche

Post by ptuomov » Wed Aug 14, 2019 4:00 pm

Jokeri wrote:
Wed Aug 14, 2019 12:49 pm
I don't know but if you can detect knock at early stage then you should be safe from pre-ignition too?
I don't think so. The reason why I don't think so is that with a very high octane race gas, one could in principle have no knock but nevertheless a pre-ignition destroying the engine.

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Now this is important

Post by ptuomov » Sun Sep 15, 2019 5:09 pm

Which decal arrangement looks better to you?
7BB9BF84-87EC-4BF2-A432-292950BF2CC3.jpeg
1A4E0333-1278-48CC-A48A-2F0FF8B6FEB7.jpeg
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Re: Dyno result for the risky business Porsche

Post by mk e » Sun Sep 15, 2019 5:45 pm

The Porsche emblem in the center seems to fit better
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