First run while data logging in my 86 IROC yesterday:
305 TPI, 700r4, 3.42 rear, stock exhaust engine through cat, edelbrock from cat to rear, winaldl and laptop.

Car has always run great but I'm trying to get into reading/understanding/programming so I can play with my other IROC if I ever get it back on the road.

My question has to do with the blm readings which seem to be very high vs. the numbers I see quoted. The int numbers seemed spot on. The knock numbers also confuse me. They seem extremely high. Since the rebuilt 700r4 (with shift kit) went in my mileage has dropped from 20 to 16 due to being in 3rd gear with no TCC lockup while cruising around at 45 mph (used to be OD with TCC locked up so 700 to 800 rpm less all the time). Now for the numbers. This covers several hundred samples over a 20 minute drive in light traffic.

blm first

Wide Avg
RPM \ MAF 24 48 72 96
400 128 0 0 0
800 150.4 0 0 0
1200 151.2 0 0 0
1600 144.9 142.6 146 0
2000 144.8 143.7 144 0
2400 144.9 143.4 144 0
2800 0 0 145 0
3200 0 0 0 0

int next

Wide Avg
RPM \ MAF 24 48 72 96
400 128 0 0 0
800 130.1 0 0 0
1200 131.5 0 0 0
1600 127.5 126.7 128 0
2000 127.9 130.6 130 0
2400 128.9 126.1 124 0
2800 0 0 114 0
3200 0 0 0 0

Knock last

RPM \ MAF 32 48 64 80 96
400 649 0 0 0 0
600 0 0 0 0 0
800 0 0 0 0 0
1000 11 0 0 0 0
1200 16 0 0 0 0
1400 3 4 0 0 0
1600 18 5 0 0 0
1800 277 4 0 3 0
2000 2 8 4 0 0
2200 1 13 3 7 0
2400 2 5 3 1 0
2800 0 0 2 0 0

I may be misunderstanding the winaldl readme file but I thought it said it added a one to each cell where a knock signal was read while recording data. If I understood it right isn't this a lot of knocking? The only hesitation I ever feel while accelerating is just above 4500 rpm when it starts running out of breath on its way to the 5500 rpm (foot on the floor) shift point.

Sorry for the long post but I'm more excited about learning this stuff than I have been about anything else in a long time. I have lots of questions as I continue to try to understand things. No plans for immediate changes (chip burning) even though I have the stuff to do it. I want to understand it first. Thanks for any input.

 

it would seem like you're running lean.

knock counts are cumulative, so if you drove around for an hour to acquire the log you have, then that's a different situation than if you just ran it down the 1/4 mile.

how's your fuel pressure? any oxygen leaks into the exhaust? is anything modified from stock?

finally, if indeed you are way on the lean side, this could be contributing to your knock counts.

 

Thanks for the reply. It was about a 15 minute ride to the parts store. My first trip while logging. No real mods to car. Exhaust is fairly new Edelbrock cat back. I've had the car 5 years and other than an occasional EGR code I don't usually see the check engine light. Did another identical trip the next day and the knock counts were almost to zero but the blms were still high. Same gas in the car, same roads, same distance, etc. As one of the old guys at Spruance used to say - data, data, data. gather it, look at it, figure out what it's telling you and then gather more data, data, data and see if it's still saying the same thing.

Right now I really don't know what I'm looking at so I'm going to spend a good deal of time logging and looking at the numbers for awhile. I'm not looking to make a rocket out of it (even after the previous two cars - 81 Z28 with a 350 and muncie 4 spd and a 73 Laguna with a 350 4 brl. and 350 automatic) that 305 TPI along with the braking and handling are still thrilling me after 5 years. I just want to understand what is going on. The real deal is my other 86 IROC (if I ever get it on the road), that one will be the modified toy.

Thanks again. I'll be reading everything I can in this forum and the others that deal with the engine and tuning.

 

You mentioned the EGR code, issues with the EGR will cause what you are seeing. When the ECM commands EGR active it also increases timing and reduces fuel. If the EGR isn't opening far enough then the extra timing causes pinging and the BLM increases to bring the fueling back in line.

RBob.

 

Thanks. That might be it. The EGR thing has been going on since I got the car. It never lights the SES light unless I meet the conditions - op. temp., steady speed for longer than 5 or 6 minutes, etc. - only happens on the interstate at cruise speed. I've always ignored it since I was getting 23 mpg with the car loaded for a trip and doing 15 to 20 mph over the speed limit most of the time (and because I was ignorant of the numbers I'm seeing now). I think I can see now that the conditions exists all the time even though I only occassionally meet the right conditions to set the light off.

 

EGR on a MAF car should only give more spark, and not do anything with fuel, since EGR is inert, and the only air with O2 that gets in should be through the MAF. Maybe you have a vacuum leak as well, but it kind of looks like the learn is the same at low and medium loads which might mean low fuel pressure.

Also, are you using an ALDL cable with the 10kOhm resistor? That'll cause the computer to add 8 or 10 degrees of timing, which can cause your knock, unless you disabled it in the calibration.

 

yes, I think the cable/adaptor has the 10 ohm resistor in it. At least the switch has 2 positions, Check Engine and 10k ohm.