First, a little history...

I had my CNC heads repaired twice, once due to hydralock and the second time due to a broken rocker arm. I was told originally that my compression ratio should be ~10.8:1. After the repairs, Pete Incaudo took a wild a$$ guess and said it may be as low as 10.3:1 now. If there's a cheap way to accurately determine what it is, I'm all ears. I've had a mail-order tune from Ed Wright for a couple of years now.

So, I was at Ed Wrights shop awhile back. I tell him the same story as above, and he uses the spark tables for the lower compression. Audibly pings like a MF'er. Sounds like I have popcorn in the engine above 4K. So he gradually bumps the spark tables all the way up to 11:1, still knocking. We figure it's bad gas at this point, but he also checked the fuel pressure. It started at 59 and dropped to 56 before getting out of the thorttle due to knock. Nothing I could do about the gas. Tank was half full and even if we added octane boost we wouldn't know the octane level and might have needed to pull timing later on normal 92-octane gas.

So, he makes a couple of tweaks to my setup, but I'm not sure which spark table I ended up with. So I buy an autotap when I get home, and this is what I'm seeing. It was 1600mi to get home, so it should have been pretty accurate at that time. Here's data from spirited street/interstate driving:

WOT B1S1: .900-.915, drops to .0xx during 2-3 shift
WOT B2S1: .93-.95, drops to .5xx during 2-3 shift
WOT Timing:
1st gear: 25-30
2nd gear: 23-34
3rd gear: 21-26
4th gear: 20-24
KR: 2.5-4* of KR above 5K in 2nd/3rd/4th, but not 1st gear

LTRIM B2 varies between 7 & 13 during cruising below 2000 RPM's. LTRIM B1 varies between 8 & 18 during same conditions.

Took it to the dragstrip a few days later, and was given this data:

[code]
Engine Speed,MAF Air Flow Rate,Throttle Pos Ang,O2 Sensor - B1S1,O2 Sensor - B2S1,Ignition Timing Adv,Knock Retard,Intake Air Temp,Barometric Pressure
942,8.85, 0.4,0.065,0.140,19.0,0.0, 79,30.1
921,8.94, 0.4,0.065,0.140,20.0,0.0, 79,30.1
922,8.80, 0.4,0.080,0.150,29.0,0.0, 79,30.1
1076,12.21, 4.3,0.235,0.145,33.5,0.0, 79,30.1
1875,17.00, 7.5,0.125,0.200,38.0,0.0, 79,30.1
2267,17.05, 7.8,0.870,0.675,37.5,0.0, 79,30.1
2448,24.57,12.6,0.820,0.180,36.0,0.0, 79,30.1
1461,54.03,37.7,0.085,0.170,18.5,3.9, 79,30.2
2336,105.25,100.0,0.920,0.945,22.5,3.9, 79,30.2
4059,195.82,100.0,0.905,0.955,21.0,2.9, 77,30.3
6030,290.08,100.0,0.925,0.965,25.0,3.8, 73,30.3
5938,266.69,100.0,0.920,0.975,26.0,0.0, 73,30.3
5643,277.54,100.0,0.925,0.955,28.0,0.0, 72,30.3
6461,298.50,100.0,0.930,0.970,25.0,3.4, 70,30.3
6481,24.39, 0.0,0.870,0.735,22.0,3.3, 68,30.3
5350,270.33,100.0,0.920,0.955,24.0,2.2, 66,30.3
5787,286.14,100.0,0.925,0.970,26.5,1.4, 66,30.3
6225,273.73,100.0,0.925,0.970,28.0,0.9, 64,30.3
6592,284.42,100.0,0.925,0.975,25.5,3.0, 64,30.3
6560,25.26, 0.0,0.820,0.745,24.5,0.0, 64,30.3
5370,259.77,100.0,0.910,0.950,26.0,0.0, 64,30.3
5448,24.32, 0.4,0.860,0.900,34.0,0.0, 64,30.3
5218,10.65, 0.4,0.045,0.635,34.0,0.0, 64,30.3

Engine Speed,MAF Air Flow Rate,Throttle Pos Ang,O2 Sensor - B1S1,O2 Sensor - B2S1,Ignition Timing Adv,Knock Retard
1990,12.41, 3.5,0.815,0.150,37.0,0.0
1857,13.07, 3.5,0.850,0.935,37.0,0.0
1855,13.99, 4.3,0.870,0.950,37.5,0.0
1880,75.31,36.9,0.020,0.110,15.5,5.4
813,44.78,100.0,0.900,0.930,19.0,2.5
1814,87.14,100.0,0.890,0.945,22.5,2.4
2638,109.81,100.0,0.905,0.930,24.5,2.0
3620,171.54,100.0,0.905,0.940,22.0,1.7
4787,236.21,100.0,0.905,0.955,24.5,1.2
5739,261.91,100.0,0.915,0.965,27.5,1.0
6726,58.90, 0.0,0.620,0.985,34.0,0.0
5374,267.64,100.0,0.915,0.985,26.0,0.8
5167,220.82,83.5,0.905,0.970,26.0,0.6
5746,272.49,100.0,0.920,0.970,27.5,0.4
6237,282.70,100.0,0.925,0.980,27.5,1.3
6664,24.83, 0.4,0.490,0.720,34.0,0.0
4958,243.23,100.0,0.905,0.970,22.5,1.3
5123,243.23,100.0,0.915,0.960,24.0,1.1
5405,251.14,100.0,0.915,0.970,25.5,0.8
5642,279.05,100.0,0.915,0.970,26.5,0.6
5897,276.17,100.0,0.875,0.985,27.5,0.4
6145,275.10,100.0,0.920,0.980,28.0,0.4
6348,298.50,100.0,0.925,0.975,28.5,0.2
6616,16.82, 0.0,0.515,0.705,34.0,4.0
5045,243.23,100.0,0.905,0.975,21.0,3.2
5178,239.39,100.0,0.910,0.970,22.5,2.5
5319,243.23,100.0,0.905,0.965,24.0,2.0
5470,256.67,100.0,0.915,0.965,24.5,1.6
5588,14.44, 0.4,0.460,0.750,34.0,0.0
5412,11.89, 0.0,0.045,0.685,34.0,0.0
5289,11.74, 0.0,0.040,0.690,34.0,0.0
</pre><hr></blockquote>

My relevant mods are Whisper MAF ends, LS6 intake, 2.02/1.57 heads, 218/226/112 cam, Grot headers/y-pipe, and tuning.

So, based upon this, a few questions:
1) Why is one O2 sensor leaner than the other?
2) Why don't I get KR in 1st gear, but do in the others?
3) Shouldn't my timing be higher? If my cam has 4* of advance ground in, how much should I be seeing in AutoTap?
4) What will the MAFT fix/not fix of the issues indicated by the logs?
5) Should I switch back to stock MAF ends?

Thanks!

 

ttt

 

my O2s are also differnet on each side, i dotn know why though

tendency to knock is increased with increased load. deeper gearing (such as in first gear) lessens the load on the engine, reducing tendency to knock

Cam timing and spark timing are two totaly and completely different things.

cant help with the other questions

[ January 21, 2002: Message edited by: Freak ]</p>

 

Reason I ask about the cam/ignition timing is that Ed said, "...and there will be no way to put 29 or 30 degrees advance in it and not
detonate it. With your cam advanced, I will be very surprised if it will like that much." Maybe I just phrased my question wrong above.

 

I see what you are saying now, i thought you were thinking they were the same thing.

cam timing probably affects where the motor likes the spark timing, but i couldnt tell you any more than that...

 

From looking at those logs, you are running way rich at WOT. If anything I would get the Maft just to do some of the initial adjustment yourself. I had Ed handle my computer, but it is totally impossible for him to nail everything perfectly. I still use the MAFT. As for one side constanly running leaner, try swapping your o2 sensors from the rear. If your sensors are fubar, that would explain the high o2 readings and the knock issues as you would adjusting for the wrong readings.

 

D4mn, I forgot to mention something. I'm not sure if they pull one or both O2 sensors for the wideband, but whatever they did pull was very sooty. This seemed to contradict the 14:1 lean condition causing the severe knock above 4K.

I don't have rear O2 sensors. Even if I did, seems to me I read they are a different part number and were not interchangeable with the fronts, thus would give different readings.

 

Mueller if you need a MAFT I'll sell you mine at a decent price. Let me know. I'll even help you tune it.

Tim

 

Tim,

You have private e-mail...