entropy
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posted December 09, 2006 12:52 AM
Tuning Tip: Detonation "Fingerprints"
from Innovation website
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Tuning Tip: Detonation "Fingerprints"
[The following is extracted from a forum thread. Klaus will be discussing this further at his PRI seminars. You can download and view the log from the thread.]
Here's a log from one of our ST-12 customers. I had never seen this before in this context. The interresting part is that on this engine the knocking cylinders cause a specific AFR signature. I suspect the abnormal combustion during knock causes part of the mixture to not burn at all, causing excess O2 in the exhaust.
This is off a 632 ci Ford drag racing engine with one 1150 CFM Holley 4 barrel. The engine came from the builder with 36 deg. of ignition timing. The engine was designed to run with a 400 HP shot of NOS. Engine was dynoed on a DTS Dyno equipped with an Innovate ST-12. Ignition timing was adjusted anywhere from 28 to 36 degrees. Engine made 850 HP at 36 degrees Ignition timing on VP C16 fuel no NOS.
The engine did not knock audibly, but was not making the expected power. The first session in the log (named "Detonation 36 deg Advance") is with C16 fuel and 36 deg. advance. Notice cylinder number 1 and 2 (purple and black) showing lean spikes, but not the characteristic sharp spikes of ign. misses, but a lean area with overlaying wild excursions. These cylinders are knocking, badly, as was determined later.
The last session (named "Session Normal 28 deg") was on C16 with ign. advance at 28 degrees. NO changes in fueling at all. In that run the engine made 970 hp (no NOS), a 120 hp gain compared to 36 advance. Because the engine owner insisted that he needs more timing to make more power, different things were tried. The second session is with 32 deg timing and cam retarded 4 deg on Sunoco 118. The lean excursions on Cyl1 and 2 look almost the same as in the first session if you overlay the two. The third session was with 32 deg. and Sunoco 118 and cam reset to spec. It looks normal but had less power.
In the end the engine was dialed in with 28 deg. advance. With NOS it made 1450 hp.
Again, the fascinating part is that knock can have such a large effect on AFR data when seen on a cylinder by cylinder basis. When using the WB in the collector the effects will be of course diminished as the lean gas will be diluted by other cylinders normal gas. This dilution would make it harder to see. But when you see sudden lean areas that are not typical spikes from ignition misses and can't be explained by carb/injection events, high speed knock is something to consider. This is especially true for engines with factory knock sensors, as most factory ECUs don't listen to knock sensors above ~4k RPM anyway because engine noise masks the signal too much.
As an additional note, the owner had already blown up two engines at the track. He didn't believe that datalogging and testing on the track is neccessary because the engine was dialed in on the dyno already. After this dyno-tuning session, he proceeded to blow up another one. He now understands that there are vehicle issues (intake dynamics, fuel delivery, etc.) that need to be tuned at the track. So they are setting up a DL-32 system."
Until next time... Keep On Tuning!
-Innovate Motorsports
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Y2KZX12R
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posted December 09, 2006 06:31 AM
Interesting. Thanks Karl.
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TRNorBRN6001
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posted December 09, 2006 08:13 AM
Very nice info! When are ya getting 4 knew bungs and a USB to tune each cylinder?
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entropy
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posted December 09, 2006 08:20 AM
quote:
Very nice info! When are ya getting 4 knew bungs and a USB to tune each cylinder?
That's what Chris in kansas is doing 
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01zx12r
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posted December 09, 2006 04:55 PM
Thanks
Thanks for the Props Karl, That article was written by my Employer Tracy Pedigo of Pedigo Performance. Its very interesting what you can see using multiple wideband sensors. That is the system (DL-32) we are using on my bike. On the Ford note....Ive never seen a Big Block Ford make so much power...It was an awsome piece...Chris
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entropy
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posted December 09, 2006 10:34 PM
Chris,
too cool that you work for the guy who wrote the article; no wonder you are soooooo far into the DL-32/4 cyl logging!
Do you use a PC3 USB to trim AF on indiv cylinders???
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01zx12r
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posted December 10, 2006 12:29 AM
I wish.....
Due to my mapping in the PC3R with ignition timing I cant justify buying a PC3usb and Timing module? Its been awhile since ive looked into their products (awsome products by the way) but the only way I change a/f is by changing nitrous or fuel jets in each nozzle. So far I havent had to change much on the set up other than fuel pressure and bottle pressure. The tuning process is still in the works.
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Johnnycheese
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posted December 18, 2006 04:09 AM
12's need mapping or each cyl one and 4 run lean than 2 and 3
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Y2KZX12R
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posted December 18, 2006 06:10 PM
I really want to add somthing to this thread... but I'm shot tonight. But a few things about detonation and its various stages and pre-ignition need to be pointed out. Theres alot of misconceptions about these two very different problems in engines.
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VincentHill
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posted December 19, 2006 12:35 PM
quote:
12's need mapping or each cyl one and 4 run lean than 2 and 3
Give this man the Cigar! 1 & 4 do run leaner and my EGT is in #4 and my A/F is in #3 & 4. The only cylinder I really hurt slightly was #4 with an 1800 degree EGT and 18 to 1 A/F at the Track. My problem was I forgot to arm the NOS on the 2 data runs and had no information to tune with and "Went for Broke and was TOTALLY Successful! 
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Y2KZX12R
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posted December 26, 2006 01:42 PM
This ia an informative article about detonation and pre-ignition. Its not as informative as some of the SAE stuff thats been written in the last several years but its very informative.
You may want to print it out to read it better.
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Y2KZX12R
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posted December 26, 2006 01:44 PM
And a little plug in there for Dougs employer. 
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Y2KZX12R
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posted December 26, 2006 01:54 PM
So now you can understand what putting 87 octane in your 12.x to 1 bike engine is doing to your safety margin. Also you dont get the bennifits of the additives to clean and keep clean the injectors.
You could be riding in mild detonation or meduim detonation and you would never hear it over your aftermarket exhaust and wind noise.
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zrxdean
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posted December 27, 2006 08:42 AM
Thanks Jim, good article.
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