From knowing nothing to having a Thunderbird supercharger on an m20b27i

[Ether-D]

Just pulled 7 degrees of timing across the board and it's the same. It mustn't be pinging right? I'm must be mistaking another sound for ping. Gonna go check the valve clearances now.

[Ether-D]

I tried to make the video work, just click the link. It's only barely audible.

[Ether-D]

I have no knock sensor.

https://www.youtube.com/watch?v=Atd2yOrOW10

[The Dark Side of Will]

Audible pinging should be setting off your knock sensor.

[Ether-D]

Rod knock will always be worse at higher RPM than lower. If it stops at 4000 RPM, it's not rod knock.

I thought that maybe the other engine noises were masking it at higher rpm.

The thing is, nothing changed between no ping and ping. Not bad gas, two new tanks at known good gas station. Not tune (I would think), nothing has changed in the tune.

I'll look at TunerStudio and see if I can see anything...

[The Dark Side of Will]

Yeaaaah, soooo, I may have a small problem. I thought I got a tank of 89 octane that was labeled as 93 cause I started noticing pinging (or what I thought was pinging) starting at 2750 and continuing on to about 4000 rpm only at super light throttle. When I nail it, it acts just fine and the sound stops or I just can't hear it. It also seems like it's not there when the car is not fully warm. The more experienced of you already know what I likely have happening. Rod knock.

As you've figured out... it's not rod knock.

Rod knock will always be worse at higher RPM than lower. If it stops at 4000 RPM, it's not rod knock.
Rod knock is not affected by throttle. If the noise goes away with throttle application, it's not rod knock.

As far as pinging goes:
What are your ignition timing adjustments for coolant temp? If it's pinging and it doesn't do it when cold, that's probably why.
Plot out your timing curve for constant RPM (in the middle of the RPM range where you're hearing this noice) across your load axis... Does it have a "hill" in the load ranges where you're hearing this noise?

Batch of bad gas?

[Ether-D]

It never happens when under boost. AFRs are usually in the low 14s. Under boost it is usually in the high 12s to very low 13s. I'll try 5 degrees tomorrow. Thanks for the help man.

[LJ851]

2 degrees is a pretty small amount, i would try 5 or so to be sure. What are the AFRs during this situation?

[Ether-D]

Also, my last motor wasted a rod bearing and I feel like it was a much deeper "clocky" sort of rattle, not the "clacky" sound that i'm getting. I don't think a vid would pick up the sound.

[Ether-D]

It doesn't go away with heat. It's quiet when cold, and much more present when warmed up. My first feeling was ping, but I took away 2 degrees of ignition and no change.

[LJ851]

Hmmmm, a rod knock and a ping are pretty different sounding. If you have rod clearance large enough to knock, you should have brass in the oil. It doesn't sound like a knock for sure to me, a video might help.

[Ether-D]

Went out there and drained the oil, fully expecting to see copper in it. But, nothing, just black oil. WTF? Is it pinging? And why? I'm gonna look up the cps numbers and test it with a meter...

[Ether-D]

Yeaaaah, soooo, I may have a small problem. I thought I got a tank of 89 octane that was labeled as 93 cause I started noticing pinging (or what I thought was pinging) starting at 2750 and continuing on to about 4000 rpm only at super light throttle. When I nail it, it acts just fine and the sound stops or I just can't hear it. It also seems like it's not there when the car is not fully warm. The more experienced of you already know what I likely have happening. Rod knock. It was a junkyard bottom end with unknown milage. It lasted a solid year or so. I'm not too hurt about it.

So, if the worst is true, it's stroker time. If I recall correctly, the lower end rebuild stuff runs in the $800ish range, and the m50b28 crank and spacer can be had for a couple hundy. m20b27 rods are $50ish from my local e30 dude Donnie. So, time to start saving again. I have another bottom end in my parts car. Maybe swap it in. The current motor still runs pretty much fine, but cept for the ping/knock. I guess I should replace the cps and see if that's it. But something tells me it's rod knock.

I'm also gonna start building another intake manifold to sell, try to help fund the stroker portion of the saga. PM me if you want one.

[The Dark Side of Will]

Sweeet. Deal's Gap is awesome.

[Ether-D]

Well, it survived a trip up and down The Dragon and a bunch of other floggings. This thing is delightful. I got 26.5mpg on the way there on the interstate (17 whilst beating on it at The Brodeo).