Incessant ping-like sound

[X64v]

I've been having a problem with my fresh turbo motor. From 4000-5500rpm, I get a very audible sound that I thought was pinging. However, it will not go away, now matter how much timing I pull or fuel I add. Motor specs:

 

Fresh L28et stock bottom end

'73 E88 head (N33, 47.8cc chambers, sharp edges rounded)

Stock nissan head gasket, making for 7.9:1 SCR

V3.0 MS I, MSnS-E code

Stock T3 turbo, stock manifold.

Stock wastegate at 7psi.

Walbro 255lph external fuel pump

338cc injectors

1g dsm bov, no intercooler

BPR6ES-11 plugs

 

The thing is, this noise acts completely like ping. Only comes on under boost after 3800 or 4000rpm, disappears by 5500 or 5700 rpm (basically just during peak torque ranges), isn't as bad in 1st because of the lighter load, etc.

 

My normal tune is about 11.7:1 afr, 30 degrees of timing at 130kpa and 29 degrees of timing at 140kpa (at this altitude '7psi' bounces between 130-140kpa). At these settings the sound is pretty bad, happening probably 40-50 times on a second gear pull. BUT, I can pull my timing to 20 degrees under boost and richen my fuel to 10.8:1, and it still happens 10-20 times on a second gear pull (even though it feels like I've lost 40ft. lbs. of torque). It also seems to start at 110kpa, which is practically no boost, just about 2psi (ambient here is about 90kpa)

 

Could this still be detonation? If not, what is it? I'm running 91 octane gas. This exact same cylinder head/turbo/megasquirt combo ran fine on my L24 bottom end at 8.9:1 SCR. Also, I blew a head gasket because of some major knock/detonation caused by fuel starvation on a hard left-hand turn, but this 'ping sound' itself will not blow my head gasket, no matter how long I let it happen. I can rev the motor free or under light load slowly or quickly from idle to 7000rpm with no problems, no ping sound. My next diagnostic step will be to run my gas tank low and then put 4 or 5 gallons of 100 or 105 octane in to see how that affects things.

 

Any ideas or suggestions as to what's going on?

[chrism]

I had this happen on two cars of mine. A Jeep and a Toyota pickup.

It was because one of the pistons had less compression that the others and caused pinging under load. You might check to see that the compression is the same between all the pistons. Only takes one piston to be off by a little to cause pinging. My Jeep was off by 30 psi and the truck was off by 50%. Mostly because of a bent valve.

[zguy36]

A difference in compression between cylinders will NOT cause this. You most likely have something loose under the hood, that is causing a ping like rattle at those engine speeds. What ever it is that is loose reaches a resonance at that RPM and is rattling away, sounding like detonation.

[proxlamus©]

What wideband sensor are you running?!

 

I forgot to recalibrate my innovate lc-1 and ran funky AFR's with pinging..

 

after a recalibration I was 2 AFR points LEAN! im surprised I didnt blow the motor!

 

 

Also... have you checked and properly gapped the plugs!? obviously this is just a mis fire.. but it wouldnt hurt

[X64v]

I'm running an LC-1. I've recalibrated it within the month, and always kept it calibrated (not usually more than three months or so in between). Keeping a three-month schedule, it doesn't seem to change before/after a re-cal.

 

I gapped the plugs when I put them in, but I'm going to check them tonight for evidence of detonation. Also, I just put in seven gallons of 100 octane (making for about 96-97 octane in the tank), and the noise is still there in 3rd/4th gear. I'm not sure about 2nd gear, I need to take it out tonight when there's no traffic and do some more test runs.

[Clifton]

I would pull a few more degress of timing even if it isn't found to be knock. Especially without the intercooler.

 

As far as afr and knock. Gas doesn't cool to well. Unless you are on the ragged edge, which you shouldn't be, the difference between 10.8:1 and 13.8:1 isn't much as far as knock resistance goes.

 

This is just a wild guess, but could it be rod knock or piston slap?

[bjhines]

This can also be caused by the front pulley. I had the same issue that seemed to be related to both throttle and RPM but I could not get it to go away. I finally figured out that it was comming from the crankshaft pulley.

[X64v]

This is just a wild guess, but could it be rod knock or piston slap?

 

Not rod knock, but I guess it's possible it's piston slap. I don't have a clue what piston slap sounds like. If it helps, the engine doesn't make this sound any other time, when it's warming up or when I'm driving around it's totally smooth and silent.

 

This can also be caused by the front pulley. I had the same issue that seemed to be related to both throttle and RPM but I could not get it to go away. I finally figured out that it was comming from the crankshaft pulley.

 

What exactly was the problem with your pulley? Mine's bolted down tight, doesn't wobble, and the rubber was in good shape when I installed it. I did change it when I changed engines though.

[bjhines]

The bolts holding the pulley to the damper were tight. Possibly too tight. There was some clearance between the damper and parts of the pulley that caused a pinging/ringing under certain conditions.

[X64v]

Well, I think I've confirmed that it really is ping. On 97 octane, the ping sound was totally gone in 1st and 2nd gear, and was greatly reduced in 3rd and 4th.

 

Now, I have two more questions. First, why would this engine setup be pinging now, and so badly? Everything's identical to my previous engine set up with the exception of the bore/stroke size and the compression ratio. And second, why isn't this ping blowing my head gasket? I blew a head gasket a few weeks ago from fuel starvation on a hard left-hander (the light ping turned to heavy knock), but otherwise I can hammer on the motor all day with this light ping and it doesn't seem to do anything.

 

Edit: Here's the spark map I've been running the past week or two.

[X64v]

A little update: I filled back up on 91 octane and switched to BPR7ES plugs gapped at .028", and that actually worked even better than the race gas. Ping is gone in first and second, just barely there in 3rd, and not nearly as bad in 4th and 5th. I think if I pull 2-3 degrees of timing I can eliminate it completely. My only question now is why am I having to run a 7 heat range plug to get rid of ping? I'm only at 7psi and 7.9:1 cr, and my manifold air temps never really rise above 170 (I do most of my driving at night).

[nick.mitchell69]

Ok,the pulley noise would be the key-way breaking up but this would probably cause overheating because the pulley runs the water pump etc etc.Have you considered that your intake might be sucking air causing the pinging by running too lean...?Somewhere between the intake and head?

[X64v]

Have you considered that your intake might be sucking air causing the pinging by running too lean...?Somewhere between the intake and head?

 

I'm running megasquirt, vacuum leaks don't cause the engine to run lean. Also, I said above that my wideband reads 11.5:1 to 11.7:1 under boost.

[nick.mitchell69]

By sucking air i mean literally between the intake manifold and head(not the vacuum).Same theory as blown head gaskets with uneven surfaces...

[BRAAP]

In reading over this, a couple things come to mind. Possibly your damper inertia ring has spun, (elastomer let go), and the timing mark on the damper is not showing actual piston TDC when verifying with a Timing light? Maybe try pulling out a lot of ignition timing, I mean an exaggerated amount of timing, say on order of 15-20 degrees across the board. If the car still runs and runs good, then chances are when you set your base ignition timing, your damper mark had spun, OR, possibly the pointer is on the wrong side of the front cover for that damper?

 

Another possible issue might be the coolant flow through the head and around the chambers themselves, as has been discussed before, (link to an INCREDIBLE discussion below).

 

With your Turbo engine, I would definitely recommend sticking with at least the NGK heat range 7 plugs. You might even try the 8’s though you may find that at partial cruise, the 8’s might carbon out, not getting hot enough, though under boost may be just right. A slightly leaner cruise mixture will help keep that from happening, but wont cure that 100%. Plug heat range is very dependent on each engine. For example, my N/A 8:1 L-28 loved the NGK BPR7ET’s. 6 were to hot, and 8’s were perfect while at the track, but too cold for the street.

 

Outside of that, I’m at a loss as well.

 

1) Verify without doubt that your damper pointer IS point to TDC when the number one pistons is actually at TDC!

 

2) Try next colder heat range spark bolt, 8’s in this case, you may have to lean out cruise mixtures if you try this.

 

3) Install a colder Thermostat such as the 160 degree which should help cool combustion temps a little more. Also along those lines, I have read reports from others whom I trust in this arena, that coolant additives such as Red Lines Water Wetter and NPG-R coolant helped noticeably reduce the common L-series ping. Theory is it softens the coolants surface tension allowing the heat from the chambers to transfer that heat to the coolant more efficiently therefore keeping combustion temps cooler which WILL reduce ping.

 

 

Here is that thread that goes into incredible detail regarding blowing the head gasket at cyl #5 and coolant flow, water wetter, etc. It is a deep subject, but VERY informative;

 

http://forums.hybridz.org/showthread.php?t=125186

[BRAAP]

By sucking air i mean literally between the intake manifold and head(not the vacuum).Same theory as blown head gaskets with uneven surfaces...

 

Your suggestion/advice is quite vague and I’m not even understanding what you are talking about. Could you please clarify more?

 

As I understand it, your description would be a vacuum leak at less than atmospheric MAP and would also be a boost leak at above Atmospheric MAP, or while under boost. Being MegaSquirt and a MAP based EFI system, if such a breach in induction sealing was at the TB, plenum, turbo, (other than the individual runners themselves), to a certain extent, that can be tuned around, unless it is a cylinder specific leak which as I understand your explanation, then would hold true for a particular cylinder.

 

If it were sucking more air, (MAP less than atmospheric) that would be a vacuum leak and if that leak were in the plenum, all cylinders would see that vacuum leak equally and being a MAP EFI system, he has already compensated for that as his AFR’s are safe and good. Now if this “leak” were at an individual runner, say at the manifold to head interface or a vacuum port in that individual runner,

then what you are saying would make more sense. A vacuum leak, (MAP at less than atmospheric) would be a leaner mixture for that particular cylinder as it is drawing min more air than the fuel that cylinder is receiving. MAP at atmospheric, AFR’s would be equal and fine, then at above atmospheric MAP, (under boost), that particular cylinder would be running richer as it is now getting more fuel and less air, as some of that air is now being expelled out of that leak area to the atmosphere and not being ingested into the engine.

[ktm]

BRAAP, for some reason my car did not like 7s. I kept missing like crazy at higher loads, even when gapped down to 0.025". I put 6s back in, gapped at 0.03", and the miss is gone. Still, each engine is unique. I may try 7s again, but I am now injecting meth so my cylinder temps should not be as high as without. As an aside, I was out testing the setup today using washer fluid. Apparently I was adding TOO much water, as my spool time INCREASED dramatically. My EGTs were a little TOO cool.

 

The thread you linked is a GREAT resource of information. I was looking at pulling timing and adding fuel to cylinders 5 and 6 (I am full sequential) to help cool those cylinders. I blew my HG twice at #5 and #6. I am now running 100% distilled with water wetter and a 160 degree thermostat. The car has never run this cool.

[X64v]

Thanks for the response Paul. The bit about your N/A engine wanting 7s clears it up: if this heat range is what the engine wants, I'll just run them. I know for a fact the timing mark is correct. I verified it when I built the engine a month ago, and immediately set my trigger angle in Megasquirt to match. As far as the thermostat goes, I was under the impression that 160 degree thermostats were run to keep the engine at about 170 degrees normally, correct? Well, with my 180 degree thermostat, Megatune reads 170 degrees around town. Also, I already run distilled water with Water Wetter and a JTR aluminum radiator.

 

I have read through that thread, and it wouldn't surprise me if my E88 head has different coolant flow patterns or casting flashing in different places that make it just a tad more susceptible to ping. But like I said, if the engine likes 7s on the street, 7s are what I'll run.

[X64v]

Alright, I've been running the BPR7ES plugs, and I pulled my timing to 25-26 degrees at 7psi, but I'm still getting moderate detonation with 85 degree ambient temps and 175 degree water temps. I'm going to try some BPR8ES plugs, but it's strange that I should have to go so cold. My L24 turbo motor was fine on 6's all the way through 10psi even with outside temps pushing 115, with the only difference being the bottom end (which had a much higher comp ratio, 8.9:1).

[X64v]

Another update: Taking a look at my old blown head gasket, it appears that I'm only pinging on cylinder #4. The gasket was blown out the side on that cylinder, but still almost perfectly round on every other cylinder, not egg shaped at all. Taking a look at my plugs (the 7 heat ranges), they were all pretty black except for #4, which is much lighter than the rest, telling me it was lean. I ran some commercial-strength fuel injector cleaner through but it didn't seem to help. I pulled and home flow tested the #4 and #3 injectors (#3 as a known good one), and #4 flowed less, but only 10% less. I reinstalled them and tried adding 12% fuel to compensate, but the pinging remained. I switched the #3 and #4 injector around, and will drive around for a few days to see which cylinder runs lean, but I really doubt the injector is the cause of my problems, I think it's always been like that. Its spray pattern was nice and conical, not lopsided or messed up in any way.

 

Any last ideas?