Home | Mailing List | Specifications | Care and Feeding | Modifications | Vendors | Literature

 

Second Time Piston 5 Toasted 

02/25/2007; updated 02/26/2007


I confirmed my suspicions today when I finally got around to pulling the heads. Not as pronounced as the previous one as the cylinder wall looks unmarred. I have a couple of other pics but this shows the piston the best.

Carter Fuji 

   

Oh, and the rest of the cylinders look great. Note the hone marks still inside this one that I have put at least 26,000 miles on boosted.

Carter Fuji 
___________________________________________________________________________
You also notice the burned area is on the same area as the previous. Kind of strange the is not only #5 but also the center side engine again. Does that seem odd?

Weird that it's the same one. Do you think it's from a lean condition?
Louis Grande
___________________________________________________________________________
Not much else could cause a burned piston like that.

Carter Fuji 
___________________________________________________________________________
FWIW, Possible injector restriction or partially opened exhaust valve. Just a thought....


John H Fiegel
___________________________________________________________________________
Do 4 and 8 look anything rich?
How's #1 look.
This is the second time. Something is going on here like too much air
pressure on the passenger's side of your intake under full boost. # 5
injector is right near the FPR so that is not likely the cause of
lean.
I need to know this too as I am about to commission another
supercharged SHO and would hate to bake a cylinder unnecessarily.
Granted, mine won't have a surge tank or traditional runners. Mine
will have a box manifold and Mustang injectors. Positive Displacement.

Eric Lehmann
97 Ebony 42k Welded - With the Angels Now so that I don't have to be.
Long Live the Garage Queen !
96 Medium Willow Green Metallic 103k Resurrected, Welded
96 Rosemist 72k 2006 Best Of SHO, Popular Vote, Welded
96 Medium Graphite 120k - Resurrected, Welded
97 Pacific Green - Parting this one Out
___________________________________________________________________________
Then I wonder if maybe switching to individual fuel lines for each injector vs using the stock fuel rail might help. This is assuming that the injector is currently able to supply enough fuel now. 
Louis Grande
___________________________________________________________________________
I don't know how that would be possible. I tried using one off of a Mustang but because of the location of the injectors under the intake for the front bank didn't allow me to route them where they wouldn't leak. I also had issues with the centers being further apart and my mountings weren't spaced correctly so they were twisted up pretty bad

Carter Fuji 
___________________________________________________________________________
Picture with the hone marks is number 4. 1 and 8 look just as clean and pistons are fine. So are the valves.

Carter Fuji
___________________________________________________________________________

Looks to be a little lean??? Lucky thereís no hole in it!
Joe
___________________________________________________________________________
Just one cylinder and it is the same one as last time but with new much larger injectors and some programming to match them. My mixture gauges never hang in the lean area and are usually in the rich side. The top of that piston is pitted too, not sure if you can see that unless you download it and view it at full size.

Carter Fuji 
___________________________________________________________________________
Just what are you calling lean and rich? What kind of a/f's are you running while under boost? If it's not the valves, or the fuel injectors, or the flow to them, then what could it be...the way the air is forced into the intake and how it handles that air, maybe turbulence inside the intake forcing one cylinder lean under certain circumstances? I know it would be expensive, but could you mount two a/f's, one for both banks, that would at least show if one bank was lean, the other rich. Maybe they are balancing out when they meet, the af gauge is after they meet, and that's why the af meter shows your good? Just thinking out loud.... 

k mier
__________________________________________________________________________
I actually have each of the stock O2 sensors wired to a set of LED A/F gauges so I can see the bank specific levels. The narrow band measurements bounce around a lot but they stay out of the limits. I saw it more often into the RICH side then the LEAN side measured as 0.1% off of perfect.

Carter Fuji 
__________________________________________________________________________
Itís an obvious heat issue. I would only suspect a lean condition. Did you shave the heads at all, effect the compression?
Joe
___________________________________________________________________________
Nope (shave the heads). Not a good idea on boosted motors unless you have a large supply of them.

Carter Fuji
___________________________________________________________________________

Pull your # 5 fuel injector from the fuel rail and look down inside
the little basket strainer for foreign objects.

Eric Lehmann
97 Ebony 42k Welded - With the Angels Now so that I don't have to be.
Long Live the Garage Queen !
96 Medium Willow Green Metallic 103k Resurrected, Welded
96 Rosemist 72k 2006 Best Of SHO, Popular Vote, Welded
96 Medium Graphite 120k - Resurrected, Welded
97 Pacific Green - Parting this one Out
___________________________________________________________________________
If you don't have a wide band O2 you are just guessing on the A/F mix. The stock narrow band O2s just tell you what's going on when in closed loop.

I bet you are running lean when there are large throttle changes.

Paul
___________________________________________________________________________

Still makes me wonder; Why only #5??? What is so significantly different in that cylinder/intake port/injector rail?

Carter Fuji
___________________________________________________________________________
Coincidence it happened on number 5 again? I didn't see anything in the injector this time.
Carter Fuji 
___________________________________________________________________________
Could be a cooling issue. The V8 heads will pass quite a bit of coolant back to the degasser tank instead of down past the cylinder liner on #1 and #5. I restrict the flow of coolant to a trickle on the 3/8" hose coming out from under the intake.

Paul
___________________________________________________________________________
There may be an undocumented fuel pressure issue at cylinder 5 due to the rail design that may be causing this. IIWM, Iíd want to wideband each exhaust port on the head to see what each individual injector is doing. It may be a matter of fattening up specific injectors to get the correct mixture for each cylinder. Of course I canít think of an easy way to do that unless you had headers with a bung on each tube or had the engine running in a test cell or something that made it easier to probe each cylinderís exhaust port.

Chris Archer
___________________________________________________________________________
And besides the inexpensive headers, WB O2 are how much each?

Carter Fuji
___________________________________________________________________________
$200. How much does it cost to rebuild your #5 cylinder?

Paul
___________________________________________________________________________
Yeah, was just a tad more to repair the engine then a pair of WBO2 but then I am getting tired of dropping the motor every year to replace the broken pistons, probably worth the investment. Would it do any good or even possible to wire these into the ECU so that it could correct the fuel issues?

Carter Fuji
___________________________________________________________________________
;) The PLX kit I have from Josh was $199. You technically wouldnít need 8 WBís, just one to move from cyl to cyl to do the sampling. If I have the chance, Iíll look at a pair of exhaust manifolds this week to see if it would be feasible to make a test set with bungs for each cyl. This spring Iíll probably configure dual WBís on my car, one for each bank.

Chris Archer
___________________________________________________________________________
This may only be a band aid, but may prove helpful. If you could skew that injector a couple percentage points, that may keep from burning the piston.
Nick C
___________________________________________________________________________
I am now thinking maybe I have an issue in the ECU itself that is causing the number 5 Fuel Injector to not stay open long enough. Possibly caused by a bad diac/triac or whatever type of switch they are triggering them with. I have thoroughly examined the intake but have not found an area/crack/gasket that would draw additional air to only that port. The only other thing that could be an issue but would be easy enough to test would be the harness to the ECU plug/socket. Think I will be trying that tonight.

Carter Fuji
___________________________________________________________________________
I'm looking for the photo that was posted a long time ago on the forum of a setup with individual fuel hoses for each injector to eliminate the rail. If the stock fuel rail is not able to supply the injectors then you might look at boring one out a little or maybe finding somewhere that can fab something aftermarket to work. I know AEM has rails that go 1/2" bore or something close.

Also, what pump and fpr are you running? The v6 FI guys were having problems with overrunning the stock FPR and went to Josh's adjustable setup. Here's parts of 2 posts from Ted B re:aftermarket fuel pumps and SHO fuel system--

The high pressure (HP) version of the pump is intended for turbo cars, and isn't of any use to a normally aspirated SHO. Additionally, I recall there being some issues with 255lph pumps and SHOs. If my memory serves to be correct, this was due to a condition whereby the pump is able to momentarily overrun the fuel return line at WOT. This actually caused a closed loop issue as a result of the abnormally high rail pressure, which in turn caused the ECU to gradually lean the fuel mixture (observed during several dyno runs).

Just FYI from the depths of my memory . . .

Actually, the overrun occurred not during WOT, but during the transition from open to closed loop immediately following a WOT event. When this happened, the ECU logged an abnormally rich mixture upon returning into closed loop, and began leaning the fuel trims.

Thinking maybe, like Paul said, between loops the car leans out too far from rich WOT. Looks like the v6 guys have had alot of success with Josh T's setup. Might be a similar problem?

Someone has already mentioned that a specific FPR cures the issue, so let this be known.

Louis Grande
___________________________________________________________________________
Do you have a scope handy? You can measure the duration with it.

Joe R
___________________________________________________________________________
This brings to mind a specific issue the suby's have with manual boost controllers which allow full boost to come on with out the ecu being in closed loop. This results in a temporary lean condition with full boost and timing that leads to wasted pistons. That's why it's good to go with a very experienced tuner when going with the MBC and to know how to drive to avoid the situation which is more pronounced on the later ecu's that have a longer delay time from open to closed loop. Not saying this is what's going on, just thinking. In fact, why would that only seem to affect #5? Never mind. 

Could the injector be going bad? Latency lagging behind the others? They could be sent off for testing. 

Carter, I think the stock o2's will be more or less a narrow band sensor. You really do need a good wide band, IIRC, the LM-1 comes with software, all you have to do is plug it into your waptop and log away. Even if it costs a lot, think of all the power you will be able to gain by getting the correct af's dialed in and better reliability. Maybe Chris could hook you up with that manifold so each cylinder could be tested. That would be the cat's meow.

And, what kind of af's are you seeing? 

k mier 
___________________________________________________________________________
Same cylinder as last time with new BIGGER injectors leads me to think the probability of the injector being clogged would be unlikely. Not sure about the O2 numbers as my meter is moving to quick to get accurate logs.

Carter Fuji
___________________________________________________________________________
Did they send you test data with the new injectors? Most shops will test the injectors and send you a data sheet showing things like spray pattern, flow, latency, etc, they should also send you a, "matched" set. It wouldn't take much for one to be off far enough to cause problems. Like you said though, same cylinder different injectors. What fuel pump? Flaking inside the fuel rail? Poor fuel rail flow at the required rates? You are flowing a LOT more fuel than they were designed for. There have been posts where the Walbro 255lph does start to run out of steam when pushing 720+cc injectors with big turbos on a four cylinder. 

k mier
Hoping for a high 7 pass this weekend. 
___________________________________________________________________________
HEY !
On American car lists we use POUNDS when talking about fuel injectors.
What the Hell is them 720's anyway?

;-)
j/k

Eric Lehmann
97 Ebony 42k Welded - With the Angels Now so that I don't have to be.
Long Live the Garage Queen !
96 Medium Willow Green Metallic 103k Resurrected, Welded
96 Rosemist 72k 2006 Best Of SHO, Popular Vote, Welded
96 Medium Graphite 120k - Resurrected, Welded
97 Pacific Green - Parting this one Out
___________________________________________________________________________
I do have a Walbro 255 but it is a HighPress/HighFlow version. I got the injectors from Five-O performance. They said they "flow bench all injector sets to assure matching flows", or at least that is what they advertise, and we all know advertisers don't print claims.

Carter Fuji 
___________________________________________________________________________
Mmmm.....thinking.......getting....something.......68.57142857142857 lbs/hr??? As All Bundy proved, the brain needs no blood, it only needs to be kept wet. 

k mier
___________________________________________________________________________
Is there a chance that there is some quirk in the intake design, maybe runners or surge tank, that causes more airflow into this cylinder than others?

BJ
___________________________________________________________________________
A/F meters hooked up to NBO2s are just a light show. What do you care what the car is running in closed loop? You will get a DTC if it is for any length of time anyway. The OEM NBO2s can't give any reading outside of a +-1 or so from the stoic 14 A/F ratio.

You cannot run an OBDII car to the limits without a WBO2 sensor.

Paul
___________________________________________________________________________
Can't be ruled out but I would think that would be more likely in the center or one of the ends which number 5 is neither. I would be more inclined to believe it is caused by lack of sufficient fuel delivery.

Carter Fuji 
___________________________________________________________________________
I still like your idea of the pulse duration. Itís an obvious lean condition but of course why.
Start easy work your way up.

Joe R
___________________________________________________________________________
Thinking out loud again.

The suby has one cylinder that tends to run hotter than the others, supposedly it's because of the design of the exhaust manifold. Could there be something in that? 

To tune/monitor that motor, In my opinion, you would at least need a wideband o2, EGT guage, knock lite, boost gauge, and some way to data log everything. Is there some kind of software out that would allow you to plug your laptop into the obd port to data log? Tuning is everything in a boosted car, you could be leaving 75hp on the table and still be in an unsafe state of tune. 

k mier 
___________________________________________________________________________
What I have seen is when you go WOT or there are very quick large throttle position changes the car will lean out like crazy. There is a work around for this with the SCT software but you have to have a WBO2 to dial in the correct numbers.

It is not unusual for me to see 17:1 A/F ratio when I do a quick 1st gear run from a stop. This is for the first 1/4 to 1/2 second.

Unless this has been addressed with your tune I can guarantee this is happening. Probably exuberated by the forced air.

Paul
___________________________________________________________________________
And we all know what happens when it gets "exuberated"!!

Ron Porter
___________________________________________________________________________
ex∑u∑ber∑ate
Ėverb (used without object), -at∑ed, -at∑ing.
to be exuberant; superabound; overflow.

Regards,
Jon Heese
*Thanks Jon! U.L.*
_________________________________________________________________________
updated 2/26/2007

carters-block1.jpg (74663 bytes)

This is what my left bank looks like after pulling the heads, right bank
looks similar. A few more weeks and I should have my new engine block in
place. Friend mechanic says it is due to low quality gas.

Carter
__________________________________________________________________________
Looks like the typical PCV contamination top me.
Low quality gas would cause pinging and other quite noticeable problems.
Paul
_________________________________________________________________________
Everything looks to be there, it's just buried under junk. Seen better, seen worse.
Bring the worst one up to TDC and give it a little scrub with a
scotchbrite pad and some Berryman's B - 12 cleaner. I bet it sparkles
when you're done. Carter's engine = stuff was missing from the piston face, again, no
cleaning is gonna fix that.

Eric Lehmann
97 Ebony 42k Welded - With the Angels Now so that I don't have to be.
Long Live the Garage Queen !
96 Medium Willow Green Metallic 103k Resurrected, Welded
96 Rosemist 72k 2006 Best Of SHO, Popular Vote, Welded
96 Medium Graphite 120k - Resurrected, Welded
97 Pacific Green - Parting this one Out
_________________________________________________________________________
I think I'll pop that piston out tonight and get a shot so you can see how much of it is actually missing. The photo of it in the cylinder just makes it look like a shadow when actually all that dark area is missing aluminum.

Carter Fuji 


Contact Information