From knowing nothing to having a Thunderbird supercharger on an m20b27i

[Q5Quint]

Check the plugs. I had a o2 sensor go bad on me and it was tricking me pretty good.

"More fuel!" it says. "But we are flooding!" the plugs say.

TB shouldnt change afr since it is measured off the manifold pressure. You could use your hand for the TB and it should still work the same. TPS is only used for acceleration enrichment. IAT should retard timing if intake temp gets too high or add fuel if it thinks its cold outside for warmup enrichment.

You may have been running in warmup enrichment all the time and not known it, and now that it is summer all your values are off.

[Ether-D]

So, what had happened was, i re-calibrated the IAT when I did the TB upgrade, aaaaaaaaaand I may have (read: did) entered my Fahrenheit temps in as Celsius. So when I clicked the little f button instead of the c button everything got just dandy again.

So all is well and I'm taking the supercharger off to remove the intercooler from the intake mani (because of the hole), and I get it off and there's this huge hole in the heat exchanger centered over cyl no 1's intake runner. It's the same shape as the runner, and it has been just melted like a mug. That was the cylinder that had the broken exhaust rocker. So what I figure is, when the rocker broke, it stopped letting exhaust out the exhaust valve, so it blew back into the intake manifold as super hot exhaust backwards. Melted the intercooler. Blasted a hole in the fins. Crazy right?

[Ether-D]

And I'm pretty sure my engine ate some copper. Is that baaaaad?

[The Dark Side of Will]

Potentially Bad? Yeah... But if it still runs and has good compression, then nothing happened.

You got pretty lucky, as something like that could have ended much worse.

Be careful about units... Feet vs. meters wrecked a multi-billion dollar mars probe a few years back.

[Ether-D]

So, it seems to be running just great as of late. Going to the Brodeo tomorrow morning to thrash it up and down the Tail of the Dragon and a few other choice twisties. I put 3 coats of wax on it today. So fuckin' pretty.

[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).

[The Dark Side of Will]

Sweeet. Deal's Gap is awesome.

[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.

[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...

[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]

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.

[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.

[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]

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.

[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?