detonation

philip j · 04-23-2011, 08:35 AM

I guess I've had my first run-in with the rattle of death. Though only for a couple seconds, probably less, but seems like a nightmare. I'm quite concerned weather damage has been done. My most recent mod, GHL headers, may have brought me into the threshold where it time to spend some money on a tuner. I have no problems doing wrenching, where time permits, but where tuning experience comes in, I'm lacking. Having my car now for 2 years, which had been totally stock. I have added the following. Garretson long neck I/C, K27 7200, 1 bar, BB dual out, GHL 1.75 headers, MDS ignition, Wevo shifter, Iroc fg rear bumper, NHS boost guage. BL wur, and LC-1 waiting to be installed. I'm thinking that having a experienced tuner give it the once over, I will know whether a mod fuel head will be needed. I had followed Cole's thread on the meth inj. and I am thinking of ordering a kit from Snow as I write. It seems that I can't get my mods done fast enough, and should have had my priorities in a different order, thinking safety first, now realizing how fast you can lose your build to the dreaded D word. Would like to hear from you guys who have experienced this and hopefully I have not suffered any damage. cheers Philip

jbrown · 04-23-2011, 09:43 AM

I would not get on it untill you get the LC-1 installed. You are definitly running lean if you did no tuning and dropped the new stuff in.. I have the meth kit on mine. It made a huge difference in A/F. I think it is a great safey device for detonation even if you are getting enoeph fuel. It changed the octane to about 110 and also steam cleans the motor.

Jim2 · Jim2's Garage

Put the stock spring back in the wastegate and check your timing. Follow through with LC-1 as jbrown says and your wur.

Once your AFRs are in check and you know your timing is spot on, then consider the spring. Do you happen to have season old gas in your tank? Perhaps octane is not what it was.

cole930 · 10:30 AM

Phil,

I know a lot of people think I'm full of $hit with the WMI but it works.

In the interim I would suggest you dial back the boost to .8 and take a look at your timing, I would start by setting timing at 24 degrees and keep the best fuel you can find in it.

I'm at a bit of a disadvantage here because I've owned the Old Sled for 22 years and it's old compared to what's on your 86. I would think your fueling would be ok if you have one of Brian's WUR's as he usually maps them to your requested specs. I would also think that with the mods you've done you should be able to run 1 bar without issues as long as you have decent fuel available. That's why I think you have too much advance.

Maybe some of the guy's with the later 930's will tune in.

Cole

cole930 · 04-23-2011, 10:29 AM

JIM2:

Sorry I stepped of you post but I was typing as you were posting.

Phil:

I will get out of this and leave you in Jim2's very capable hands, he's probably forgot more about these car's than I'll ever know.

Cole

philip j · 04-23-2011, 11:36 AM

Yup! I was just finishing off the full tank of gas I had put the car away with. Plus some octane boost I had put in for good measures. So, i'm worried, will this brief encounter with detonation break rings,etc. Any stories? Of course, the weather is not agreeing with driving this time of year here in Canada. Anything I should check, whilst the rain pours outside? Philip

JFairman · 04-23-2011, 03:05 PM

What did "the rattle of death" sound like?

I've always heard the B&B dual out muffler you have is kinda loud and you have big GHL primary tube headers too so I'm surprised you could hear detonation knock or high pitched pinking over the noise.

I think it's sustained heavy detonation like holding it at full boost while it's detonating from low octane gas or too much timing or boost for a half mile or longer that breaks rings and sometimes melts the edge of pistons over by the exhaust valve.
..just my opinion though.

philip j · 04-23-2011, 05:08 PM

like someone was pulling a 10' length of heavy chain out through the exhaust, real quick. Actually, even though the exhaust system is loud, you can hear every beat of the engine, all of the time. Philip

krasuskyp · 04-23-2011, 05:12 PM

oh man - that sounds more like tensioners, no?

Detonation would have to be engine smashingly overt to be that audible over the motor's inherent sound.

States Captain Obvious----------> I'd stop driving it until you figure it out.

Good luck, hope it's simple for you.

philip j · 04-24-2011, 04:04 AM

I put a large screwdriver to the chain covers/ to my ear, everything sounded normal. Maybe it's not the sound of detonation which I have experienced. Could the chain have slapped the case? I was in 2nd gear at about 5800 rpm when this occurred. Any suggestions would be appreciated. Philip

krasuskyp · 04-26-2011, 05:23 AM

knock's only gonna occur under load, so you're not going to hear it w/ yer head in the engine bay 8-)

Try it again w/ yer hand on the throttle (reach down, you can maniuplate it w/ a secret handshake), rev it up as far as yer ears / neighbors can tolerate - won't get it to detonate (unless it's really REALLY running f'd up) but you'll hopefully be able to better isolate your noise.

Good luck.