3.2 Pinging!

[IROC]

OK, so I'm out bedding in some Pagid orange pads today and I'm making some runs up to 60mph then braking and the back up to 60mph, etc., ad nauseum and so I leave it in second to do this. To my dismay I hear some light pinging as the tach swings past 6k rpm (full throttle in 2nd). Very light, but it's there.

This the first time I've ever heard this (and I've done lots of full throttle runs since installing this engine almost 2 years ago). Could it be a bad tank of gas (93 octane Chevron)? Dare I dream that this is "normal" in that I seem to be right on the edge of detonation during full-throttle, full load situations?

The engine is a 3.2 with 10.3:1 Mahles and a SteveW chip.

Any commiserating or comments welcome.

Mike

[jpachard]

Your compression ratio is right on the border for running street gas, IMO. Is this a twin plug motor? You might want to ask Steve to retard your ignition a bit. Gas has been getting progressively worse recently as well(additives, ethanol etc.)

Sorry for the stream of conciousness but maybe this will help shed some light on this.

Cheers, James

[jmz]

is it DME or carbs?

[IROC]

DME, single plug. I know I'm right on the ragged edge, but this is the first time I've ever heard the pinging...

[der Mond]

I agree with the previous post - you are such on the edge with CR that any variation on gas (and God knows standards aren't what they used to be) could put you in the cursed land. I'd also ask Steve to tweak your chip. As you probably are aware, his customer service is among the best.

[Steve@Rennsport]

Originally posted by IROC
DME, single plug. I know I'm right on the ragged edge, but this is the first time I've ever heard the pinging...

Hi Mike:

Well sir, you are well over the "ragged edge" with single ignition, 10.3:1 and pump gas.

My best advice to anyone is never to rely on the human ear as one's "knock sensors". You buy a lot of piston & cylinders with that method. Learning the technique of making accurate plug cuts and how to read spark plugs is the answer.

My immediate suggestion is to add 50/50 unleaded race gas until you either have Steve make you a different chip or install twin-ignition. I'd strongly recommend having Steve make you a custom chip on a load-type dyno so its optimized for your engine.

[ricochet]

You are offered better advice so far, I am not offering advice. I have been reading a LOT on gasoline, FI cleaners and octane boosting, but am no expert. Follow the others advice and read a little on Toluene as an octane booster. It is evil, but not the monster many believe it is (as is benzene, it's close cousin). Is easy to try 1 gallon to a tank and raise the octane, maybe make the engine happy. I had used many gallons years ago, with nothing more than slight dain bramage. Just kidding, I did not breath it, nor allow it on my skin. I did not know the proper mixes till lately, it is a science (not rocket science, but should be used following some rules).
There are mistakes in fuel blending, and sadly, maybe at the fuel supply place. If a few thousand gallons of regular were mistakenly dumped in the premium storage tanks, you'd be burning lower octane than you thought you'd purchased.
If you are in tune with your car, you will notice a slight difference pretty easily, but fail to the side of safe. Bad fuel is a reality, just not common. Good luck...

[IROC]

Thanks for the responses. This engine (in this configuration) has about 32k miles on it and has been fine (?) so far. I will get Steve to modify my chip, most likely. Twin plugging would be great, but then I'd have to jump down that slippery slope and do a bunch of other things, etc. :>)

Thanks,

Mike

[beepbeep]

do a WBO2 run, just to check if AFR is in acceptable range. If it is, it's time to wind back ignition somewhat.

I'm still puzzled how you "heard" pinging past 6000RPM. Most acoustick knock-detection systems are deafened past 4000RPM, even on (quieter) watercooled engines.

There is a slight possibility that nothing is wrong with your car and that you've been hearing something else.

[IROC]

I'd love to check the AFR and other parameters, but facilities are somewhat scarce for that sort of thing where I live.

I was as surprised to hear this pinging myself as I have never heard it from this engine before.

I'm really hoping it is a tank of bad gas, but I am going to take precautions anyway.

Mike

[Wil Ferch]

Steve Weiner is "spot" 0n !!!

There is sub-audible pinging that occurs before you get to the point of hearing pinging......get it looked after per one of the recommendations.

Wil

[jpahemi]

IROC:
What's your timing @ 5800-6200 rpms? Ask SW what the figure is, I'd like to compare.
Regards,
J.P.

[der Mond]

Steve, any recommendations for one to go about learning how to make accurate plug cuts and read plugs?

[Elombard]

What about throw in a bottle of octane boost and do some more runs see if it helps?

I thought those 10.3 to 1 Mahles were notoriously overated on their CR, hopefully making you safe on pump gas.

Steve W would know. Can ou get race gas around Lil Talladega :-))

[IROC]

I must admit that I don't know much about this chip and how it is programmed. It was pretty much a "plug and play" thing as far as I was concerned. The previous chip was a Cyntex that exhibited very poor throttle response and a horrible idle.

Steve's chip has been excellent and I really think this recent pinging has been an anomaly as I know I have never heard it before yesterday. Going slightly more conservative on the timing might not be a bad idea, though. Maybe that and a hardcore Techron treatment... :>)

Thanks again for all the responses...

Mike

[KobaltBlau]

Hi Mike,

are the 10.3:1 mahles "Mahle Sport" pistons, or (my guess) euro 3.2 pistons? Did you (or someone else) actually measure compression during the build?

[jpahemi]

Mike:
I've got a '84 3.2 (9.5:1) with a chip and it occasionally does the same thing; I get what seems to be pinging (or some kind of rattling) when the clock goes past 6K rpms. The odd thing is it only happens occaisionally and in the higher gears (3 & 4th). I've tried to lug it in 3rd with WOT, but I can't hear the rattle.
Regards,
J.P.
Ps. I still need to check the dizzy and cap with rotor.

[Steve W]

Most likely a bad batch of gas. I generally set ignition timing and AFR on the conservative side for the engine's config and fuel octane used. My suggestion if a more conservative chip is needed, or substandard fuel is suspected, is to set the DME fuel quality switch to position 4, also known as factory option M240 (version for countries with inferior fuel) which will retard your overall ignition timing by 3 degrees. http://www.911chips.com/fuelsys.html

It can be left in this position until you verify the what you had was a poor batch of fuel, or swap out for a more conservative chip. In JP's case, you can use it to diagnose if your noise is ping, or some other type of mechanical fault.

[Steve@Rennsport]

Originally posted by der Mond
Steve, any recommendations for one to go about learning how to make accurate plug cuts and read plugs?

Hi:

E-mail me directly and I'll send you the procedures to do that.

Bear in mind that reading spark plugs is both an art & a science that VERY few people know how to do. It takes a lot of experience to know what one is looking at/for,.....

[IROC]

Thanks for all the replies. After thinking about this (constantly) for the last day or so, I am leaning towards the "bad batch of gas" scenario as it makes the most sense. I have put about 10k miles on this engine and have never heard this before Saturday. Even though I bought this gas at a Chevron station, I also got a tank of 87 octane gas there last year in my Toyota DoubleCab that caused it to ping. Maybe I should stay away from that station...

SteveW - thanks for the tip on the DME fuel quality switch. That was going to be one of my courses of action - worst case. Also - your chip has been great - I in no way attribute this to the chip - I love it.

Andy - I bought this engine off of a local guy after he had rebuilt it and I'd have to say these are the Euro 3.2 pistons and not the Mahle sports. I'd have to verify that, though. To my knowledge, the CR wasn't measured during the rebuild. I've always heard that Mahles are notorious for resulting in a lower measured compression ratio than advertised.

Thanks again!!

Mike