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 Post subject: Re: Megasquirt Tuning
PostPosted: December 27, 2019, 11:21 am 
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Joined: February 8, 2014, 10:47 pm
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Location: Cornelius OR
I have found Knock sensing to be entirely experimental.
It might work on motors it was designed for, but installing one on a motor that is was not designed for is problematic.
Every motor design has it's own unique knock sound frequency, also locating the sensor where it will best pick up the sound is not easy.

Many motors are so noisy it is difficult to separate the knock sound from normal sound.
Many motors get noisier when they are flogged and will overwhelm a system that works under "normal" driving.

The safest bet is to be conservative with the spark table and use good gas.
Also it is mostly old style motors that have poor combustion chamber designs that are more prone to knock.
It is difficult to find the threshold for knock on the street and a dyno is best for that.

I have not had knock issues and use conservative spark timing. The only time I would get aggressive with spark timing is in a restricted racing class where you have to wring every iota of power out of a motor.
Thankfully for the street the power loss of conservative spark timing is not large enough to make the risk worthwhile. And it is important to leave some headroom for stale fuel or lack of premium fuel.

You can make what's called "Det Cans" < Google search terms) which are like a doctors stethoscope to listen for knock, but the best way is on the dyno so you can watch the other signs.

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 Post subject: Re: Megasquirt Tuning
PostPosted: December 28, 2019, 12:51 am 
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Joined: August 8, 2014, 6:08 pm
Posts: 1238
Location: Green Bay, WI
Bent Wrench wrote:
I have found Knock sensing to be entirely experimental.
It might work on motors it was designed for, but installing one on a motor that is was not designed for is problematic.
Every motor design has it's own unique knock sound frequency, also locating the sensor where it will best pick up the sound is not easy.

Many motors are so noisy it is difficult to separate the knock sound from normal sound.
Many motors get noisier when they are flogged and will overwhelm a system that works under "normal" driving.

The safest bet is to be conservative with the spark table and use good gas.
Also it is mostly old style motors that have poor combustion chamber designs that are more prone to knock.
It is difficult to find the threshold for knock on the street and a dyno is best for that.
Interesting info. I don’t doubt you on second. The difference in street and race is spot on. I think as long as I can have this at 95% the dyno will be a lot cheaper run.

I have not had knock issues and use conservative spark timing. The only time I would get aggressive with spark timing is in a restricted racing class where you have to wring every iota of power out of a motor.
Thankfully for the street the power loss of conservative spark timing is not large enough to make the risk worthwhile. And it is important to leave some headroom for stale fuel or lack of premium fuel.

You can make what's called "Det Cans" < Google search terms) which are like a doctors stethoscope to listen for knock, but the best way is on the dyno so you can watch the other signs.


Thanks for the sage advice. Makes sense.

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My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


Last edited by Tundra 7 on December 29, 2019, 5:54 pm, edited 1 time in total.

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 Post subject: Re: Megasquirt Tuning
PostPosted: December 28, 2019, 5:15 am 
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BW, there seems to be plenty of data on miata engine knock testing but it sounds like it would be much more practical to go with det cans, especially with an na engine.

Tundra, more info on broadband knock sensors. Miataturbo.net is a also a great resource.

https://aviondemand.com/insider/engine- ... rs-part-1/
https://aviondemand.com/insider/engine- ... rs-part-2/
https://www.miataturbo.net/megasquirt-1 ... ead-67946/
https://www.miataturbo.net/adaptronic-6 ... ing-34218/
https://www.enginebasics.com/EFI%20Tuni ... 0Cans.html

Tundra, in your replies to BW, all I see are quotes.

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360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
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Champion/Book:114x42x11
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VoDou:113x44x14
McSorley 442:122x46x14
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 Post subject: Re: Megasquirt Tuning
PostPosted: December 28, 2019, 10:14 am 
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Joined: August 8, 2014, 6:08 pm
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Location: Green Bay, WI
Miatav8,MstrASE,A&P,F wrote:
BW, there seems to be plenty of data on miata engine knock testing but it sounds like it would be much more practical to go with det cans, especially with an na engine.

Tundra, more info on broadband knock sensors. Miataturbo.net is a also a great resource.

https://aviondemand.com/insider/engine- ... rs-part-1/
https://aviondemand.com/insider/engine- ... rs-part-2/
https://www.miataturbo.net/megasquirt-1 ... ead-67946/
https://www.miataturbo.net/adaptronic-6 ... ing-34218/
https://www.enginebasics.com/EFI%20Tuni ... 0Cans.html

Tundra, in your replies to BW, all I see are quotes.

That is bizarre. I’ve never had a reply totally disappear like that. Anyway this is a pile of info. Thanks. Since it looks like we’re going to get back into winter now I’ll have time to get into this stuff.

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My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


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 Post subject: Re: Megasquirt Tuning
PostPosted: December 28, 2019, 1:13 pm 
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You know I was looking at my last timing map and it’s really not that different than the new one. From what I see it varies from 0-4 degrees depending on rpm, overall it doesn’t seem that far off. Unless I am missing something.

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My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


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 Post subject: Re: Megasquirt Tuning
PostPosted: December 29, 2019, 5:33 pm 
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I based it off your max timing at minimum kpa but the rest is a blend. Pretty different below 3k near wot (like 10 degrees in some place through that may not be best). It's just a baseline. The timing may be a little too aggressive as a baseline in some cases. What ever works for you. :cheers:

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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 Post subject: Re: Megasquirt Tuning
PostPosted: December 29, 2019, 5:58 pm 
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Joined: August 8, 2014, 6:08 pm
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Location: Green Bay, WI
Miatav8,MstrASE,A&P,F wrote:
I based it off your max timing at minimum kpa but the rest is a blend. Pretty different below 3k near wot (like 10 degrees in some place through that may not be best). It's just a baseline. The timing may be a little too aggressive as a baseline in some cases. What ever works for you. :cheers:


Sounds good, That map was the Canadian tuners safe timing he called it. I am sure yours isn't that radical.

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My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


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