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Old 03-23-2011, 09:06 AM   #41
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I had offered to build a DSP based knock system, but no one sounded interested, so I abandoned the idea. Once complete, it would probably cost $150-200 and be at least close to 100% accurate. It would be possible for it to drive all sorts of features, too, since they have plenty of I/O and calculating knock would be barely anything for the processor. It could also work on any car with no tuning necessary.
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Old 03-23-2011, 09:42 AM   #42
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I'd have been interested, assuming it worked
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Old 03-23-2011, 12:05 PM   #43
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Originally Posted by Savington View Post
I'm not sure what you're trying to get at here - you've mentioned the MAP vs. wtq/MAP chart before, but you just said that trying to hold a stable manifold pressure while the motor runs through the RPM range is nigh impossible.
Forget tq/MAP for the moment.

You pick an RPM column, and tune the various MAP points therein.
You set the dyno to hold RPM. The dyno datalogs MAP and Torque.
You sweep through your MAP breakpoints by slowly rolling into the throttle. MAP and torque both increase. Dyno plots em both. You end your pull at WOT or 100 kPa. You adjust timing, repeat. Plot the last 2 runs, and compare. See which MAP points benefited from the timing adjustment.
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Old 03-23-2011, 04:29 PM   #44
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Quote:
Originally Posted by TrickerZ View Post
I had offered to build a DSP based knock system, but no one sounded interested, so I abandoned the idea. Once complete, it would probably cost $150-200 and be at least close to 100% accurate. It would be possible for it to drive all sorts of features, too, since they have plenty of I/O and calculating knock would be barely anything for the processor. It could also work on any car with no tuning necessary.
Interesting!

1) What kind of output will it have? Something to go into the knock sensor input of an ECU?

2) What inputs will it use? CKP and CMP?

3) How will you design it so that "no tuning is necessary"?
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Old 03-23-2011, 06:22 PM   #45
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You really wouldn't need any input other than a knock sensor. From the audio, you can even figure out the ignition cycle. All you'd really have to do for setup is tell it how many cylinders and possibly what orientation the motor is in (V, inline, flat). Basically it would look at your normal operation and create a filter based on that and look for abnormal peaks. Since it can calculate RPM based on the recorded ignitions, it can probably identify an ignition problem, too.

This is all based off of what some DSP and FPGA guys know that I work with, so it's not really coming from me. It may actually be harder than I make it sound.
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Old 03-23-2011, 07:23 PM   #46
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To do time windowing you need to know the crank angle. Which means you need the crank position sensor signal.

And it should know the proper frequency range for the motor particulars.
For example, for the miata the descending note may start at 13.6 kHz and end at 11.4 kHz.
The speed at which the note descends depends on RPM, as AFAIK the resonant frequency is a function of piston position.
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Old 03-23-2011, 08:14 PM   #47
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Quote:
Originally Posted by JasonC SBB View Post
Forget tq/MAP for the moment.

You pick an RPM column, and tune the various MAP points therein.
You set the dyno to hold RPM. The dyno datalogs MAP and Torque.
You sweep through your MAP breakpoints by slowly rolling into the throttle. MAP and torque both increase. Dyno plots em both. You end your pull at WOT or 100 kPa. You adjust timing, repeat. Plot the last 2 runs, and compare. See which MAP points benefited from the timing adjustment.
Sounds good to me. Take 2-3 sweeps of each to eliminate some of the decay, and make sure your sweeps are slow and smooth.
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Old 03-23-2011, 09:20 PM   #48
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in for tons of learning
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Old 03-23-2011, 09:57 PM   #49
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I'm kind of not looking forward to dyno tuning...
Subscribed to pick the brains of you track guys.
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Old 03-23-2011, 10:34 PM   #50
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Quote:
Originally Posted by JasonC SBB View Post
Forget tq/MAP for the moment.

You pick an RPM column, and tune the various MAP points therein.
You set the dyno to hold RPM. The dyno datalogs MAP and Torque.
You sweep through your MAP breakpoints by slowly rolling into the throttle. MAP and torque both increase. Dyno plots em both. You end your pull at WOT or 100 kPa. You adjust timing, repeat. Plot the last 2 runs, and compare. See which MAP points benefited from the timing adjustment.
I forgot to mention, you make the dyno plot MAP on the X-axis, TQ on the Y-axis. You overlay succeeding runs to see where torque has improved from your timing changes.
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Old 03-23-2011, 10:59 PM   #51
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Just looked at the Dynapack viewer on my PC - the software won't set up MAP on the X-axis. It will show you the raw data in chart form, and you can use that to compare MAP and torque more accurately (albeit slower) than you could with a chart.
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Old 03-24-2011, 12:16 PM   #52
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Save into a text file.
Import into Excel.
Plot using scatter plot.
Or use AEMLog, and use XY plot.

Better yet, in Excel, create a 3rd column, torque divided by MAP.
Plot that vs. MAP.

Obviously the data has to be captures with constant RPM, else the results will be rather useless for tuning cells.

However plotting torque/MAP for various pulls with RPM sweeps (e.g. datalogs of 10 psi, then 15 psi pulls), is useful as a figure of merit.

Torque per MAP is exactly proportional to BMEP * displacement, which is a very important figure of merit.
IOW torque divided by MAP divided by displacement, times a constant, equals BMEP.

BMEP is almost the same for F1 and NASCAR engines. It tells you how optimized your setup is.
Ditto for highly tuned race motors.
Highly tuned factory motors all have very close BMEP values.
So do well tuned miata turbo setups.

Last edited by JasonC SBB; 03-24-2011 at 02:55 PM.
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Old 05-25-2011, 05:10 PM   #53
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One thing i've been noticing as i review timing maps posted throughout the forum is why you guys don't advance timing after MBT (approx 5000-6000) to carry on torque through the powerband, because the engine needs more timing after MBT due to the high RPM's. Is there any reason in particular? I've been tuning for a decent bit now and have not had any negative results.
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Old 05-25-2011, 07:04 PM   #54
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My timing map is flat throught 4500-5500 and ramps above that. That's prob part of why I hold power to 8000rpm.

Btw in case anyone thinks otherwise, I doubt anyone will hit MBT at 20psi/250kpa on pump gas regardless of pistons.
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Old 07-06-2011, 06:02 PM   #55
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Quote:
Originally Posted by Faeflora View Post
My timing map is flat throught 4500-5500 and ramps above that. That's prob part of why I hold power to 8000rpm.
...or the direct relationship between spark angle and piston speed.

This thread is now stickied because it took me too long to look for it.
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Old 09-07-2011, 09:26 PM   #56
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Quote:
Originally Posted by mspdmx3 View Post
One thing i've been noticing as i review timing maps posted throughout the forum is why you guys don't advance timing after MBT (approx 5000-6000) to carry on torque through the powerband, because the engine needs more timing after MBT due to the high RPM's. Is there any reason in particular? I've been tuning for a decent bit now and have not had any negative results.
https://www.miataturbo.net/showpost....02&postcount=8
Quote:
To combat knock they make the mixture richer. All that happens really then is that the mixture burns slower and therefore hits the peak pressure closer to the right point. This of course reaffirms the belief that the richer mixture creates more power. In reality the flame front speed was adjusted to get the right peak pressure point.
Spark angle and piston speed are somewhat proportionate; LPP is independently variable based upon volumetric efficiency, compressor efficiency, cam angle, and exhaust backpressure. We essentially advance spark with RPM to keep up with piston speed.

The shorter answer: Spark angle is a tool to position peak pressure strategically and make the most torque. Above 5000rpm, we'd have to lean out the mixture to raise torque to the point of dangerous EGT. This is another reason why direct-injection is so awesome, it can atomize fuel good enough to get a turbulent, consistent flame front, while also cooling the charge with it's awesome spray pattern.
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Old 10-14-2011, 05:53 PM   #57
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Default Dyno Tuning: Cool Day vs. Hot Day

Does it make a difference?

Background:
Turbo'ed in April. Been driving the **** out of it with pretty much no issues. I'm at 6,000 miles. Dialed in fuel using LC-1 and Megalog. EBC is also dialed in. Car runs great at 10psi with water injection.

I'm still running the MSPNP base map for spark. I'm ready to hit the dyno for spark tuning. But, it is already MUCH cooler than it was in July and August. I want to tune for MBT but at the same time make sure I have plenty of protection from detonation.

If I tune my spark in cooler weather, will I compromise my hot weather detonation margin?

Thanks guys.
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Old 10-14-2011, 07:37 PM   #58
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Quote:
Originally Posted by hornetball View Post
Does it make a difference?

Background:
Turbo'ed in April. Been driving the **** out of it with pretty much no issues. I'm at 6,000 miles. Dialed in fuel using LC-1 and Megalog. EBC is also dialed in. Car runs great at 10psi with water injection.

I'm still running the MSPNP base map for spark. I'm ready to hit the dyno for spark tuning. But, it is already MUCH cooler than it was in July and August. I want to tune for MBT but at the same time make sure I have plenty of protection from detonation.

If I tune my spark in cooler weather, will I compromise my hot weather detonation margin?

Thanks guys.
Heat soak the intercooler and you'll be fine
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Old 10-14-2011, 08:05 PM   #59
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Originally Posted by hustler View Post
Heat soak the intercooler and you'll be fine
So, I don't really need to worry too much about outside temperature.

Note that I don't run an intercooler. I'm using WI with automatic safeties (the presence of WI pressure enables EBC). I plan to tune my wastegate only pressures with WI turned off, then enable the EBC and tune the higher pressures with WI turned on.

Thanks for the reply.
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Old 11-15-2011, 11:02 PM   #60
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Sticky this ****
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