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Pete Pete Remner Ultra Moderator Location: Cleveland, Ohio Join Date: 01/11/2006 Age: Midlife Crisis Posts: 2,022 |
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MarkHille Mark Hille Super Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
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I know right?!?! The other cylinders showed holes in all of the pistons on one motor, and holes in 2 pistons on another. There are just a few signs of detonation... Edited 1 time(s). Last edit at 11/30/2016 11:08AM by Robert Culbertson. |
Gravity Fed Alex Staidle Ultra Moderator Location: Δx = ħ/2Δp Join Date: 08/21/2009 Age: Settling Down Posts: 1,719 Rally Car: Various Heaps |
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Finally uploaded some pictures.
Here's the pistons from motor #1 (low miles, overheated a bunch of times, made it an entire season and then some). They all basically look like this. The head for engine #1 has ZERO signs of detonation. Engine #2 (30k mile junkyard motor, made it through Idaho, DooWops, and recce of Rocky) |
Could be. They are apparently forged, but I haven't pulled them out of the block to check the undersides. The fact that the pistons "eroded" instead of shattered leads me to believe they are forged. Probably a higher silica content forging, making them less tough. We know that the charge temps were high, and it was going into limp mode. Apparently resetting the ECU lets you drive through that.... and straight into destroyed pistons. Ford also offers a calibration for the ECU that dumps a ton more fuel. We only found out about this after talking with a powertrain engineer at Ford Performance a few weeks ago. They use the tune for desert trucks/buggies that are using the engine. Glad it's a free re-flash, I just wish we would have known about it sooner. |
MarkHille Mark Hille Super Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
I don't think detonation is sustainable no matter how much money you spend on pistons. Better pistons will be more forgiving and give you a little more buffer but it doesn't sound like that is the solution to the problem. Those marks on the piston/head.....there are some pistons with marks (dings not detonation) that look like they weren't self induced. Like there aren't any bits big enough broken off to cause the damage. Were piston bits from the one cylinder traveling to the other cylinders or was there foreign contamination? How is your turbo looking? I would check to see what octane fuel the desert trucks/buggies are running. I would be very, very, very surprised if adding fuel and not taking some timing out (or lowering boost) was the end all be all solution to your problems. I don't think your current tune (or your current octane, whichever way you want to look at it) is close enough for just that. |
The marks, we'll call them dents, definitely look like foreign matter. The heads and pistons with the dents came from the high mileage junkyard motor. So the dents are found on the quench pads of every combustion chamber, even the ones with pistons with just a little bit of detonation erosion. The turbo looks fine, and there was no foreign material in the intake manifold or any of the plumbing. Maybe they were already there when we picked up the motor...?!
I need to talk with the guy at Ford about the differences in the tunes and what fuel the trucks are running. I fully agree that pulling timing is going to be much better at keeping the motors happy. |
Ascona73 Bob Legere Senior Moderator Location: Spofford, NH Join Date: 03/07/2007 Age: Possibly Wise Posts: 308 Rally Car: 1971 Opel Ascona |
Looks like a LOT of heat got into those pistons...note the baked on carbon at the broken edges. Probably more a fuel shortage issue, though if the ECU pulls too much timing with plenty of fuel in the mix, it basically makes a blowtorch.
Chances are the dents in the chambers are from the melted piston bits. There's enough plenum sharing it's not uncommon for one cylinder to feed all the others with those little bits of metal. I'd see what the reflash does for the engine, but I'd also seriously consider an air/fuel gauge and an EGT gauge to monitor what's going on there under rally conditions. Opel is a 4-letter word... http://www.flickr.com/photos/10498579@N07/sets/ |
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Pete Pete Remner Ultra Moderator Location: Cleveland, Ohio Join Date: 01/11/2006 Age: Midlife Crisis Posts: 2,022 |
This is why I keep going on about the air temp sensors. The fact that they went out of bounds according to the PCM is a clue. If the sensors are getting artificially heated up by hot tubing instead of reading the true air temperature, the computer will be sending fuel for a much less dense charge, or in other words, insufficient fuel. Or it could just be that the rings had not enough gap, and when they got hot under SUSTAINED loads much higher than the engines were built for, they butted and popped the OE style low-crevice-volume pistons' heads apart. The OE tune is conservative for Joe Average who will bolt the throttle to the floor climbing a mountain etc etc. The Motorsport tune gets all that fat midrange by taking away some of that idiot-proofing, with the side result that the nut holding the wheel is more responsible for engine health. Since it is probably impossible to find pistons with the correct bowl/dish shapes and a lower ringpack, it may be wise to just open the ring gap a skosh on the next junkyard mill and try again. Winter's coming, lots of people are going to be totaling their Escapes... Unbolt the rods and carefully pop the pistons out so you can spiral the rings out and take a real close look at the ends. That is where you'll see if the rings were butting or not, if the ends are shiny or peened-looking then there's one thing you can fix. Pete Remner Cleveland, Ohio 1984 RX-7 (rallycross thing) 1978 Silence is golden, but duct tape is silver. Edited 2 time(s). Last edit at 11/30/2016 11:13PM by Pete. |
john vanlandingham John Vanlandingham Infallible Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Greed? Poor advice? Inexperience? American fixation with MOAR POWERZ...? Because we can? John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
MarkHille Mark Hille Super Moderator Location: The hills of CT Join Date: 10/04/2011 Age: Midlife Crisis Posts: 135 Rally Car: I have two crap boxes |
I'm bored so here goes....
It is possible that the only reason engine damage occurred was because the intercooler setup was inadequate and this caused unsustainably high intake air temperatures. The ECU tried to prevent engine damage by going into limp mode (lower boost, pulled timing, and possibly more fuel, maybe even less spark events) but was then shut off causing it to reset in which case it returned to normal operation and continued to damage the engine by causing detonation. This is possible....but it seems a little unlikely. Why wouldn't it go into limp mode again immediately? There are 2 types of air sensors for the lima. A metal one and a plastic one. I have used both and have used them in both aluminum pipe and silicone pipe both pre and post intercooler. There was no difference in performance that I could tell and I was logging the temps to see. The sensors only got heat soaked when the car was off. When the motor was started there was only a couple of seconds that it read hot and then everything went to normal.....unless the position is total crap or the sensor is not working I don't think this is the only cause of the problem. It is only my personal opinion but I would be willing to bet that if you had been running 110 octane race fuel both motors would still be running. The tune isn't crap. The tune was developed by Ford who has a shit ton of resources. The Motorsports tune is probably partially based off of the production tune and both probably had hours and hours and $$$$$ and $$$$$ to develop them. But, like Pete said, you get more power by sacrificing the safety buffer inching closer and closer to detonation and engine failure. All of that testing is based specifically off fuel octane. If the tune is developed for a certain octane, and you run a lower octane, you are going to detonate the motor and it is going to blow up. PERIOD. A safe AFR for a turbo car is around 11:1 to 12.5:1? It isn't so hard to get in that range. Yes you can make more power with a little more or a little less depending on your setup but if you lean it out and it starts to detonate you aren't making shit for power. I personally would never run a turbo car without a wide band. I like to know things are where they are supposed to be and if I have a problem I like to be able to look over and see that AFR isn't the cause. I'm sure there are others like me who are running the Ford motorsports ECU and if it was super lean they would know about it and be shouting it from the hills...maybe not. I would bet more on low fuel pressure from a mechanical problem than on ford being too lean. Easy and fairly cheap way to find out. There is only so much power available in the AFR. Way more power exists in the boost and in the timing. I doubt Ford is trying to make it up in the AFR. The only real variables are the engine temp and the intake air temp. If they go too high the ECU would need to compensate by adding fuel and pulling timing. This is going off of memory but the rate timing gets pulled is only like 1 degree for every 50 degrees F above 200 or something like that. I don't think we are talking about pulling 10 degrees of timing when the intake air is too hot but maybe I'm wrong. The problem with a hot motor and hot intake air is PREIGNITION. The fuel starts to burn before the spark and basically leads to the same demise. Pre-ignition can be caused by a hot piston...a piston that has sharp edges on it that has formed a hot spot...a piston with dings in it like the ones pictured above. It is possible those sharp edges were causing pre-ignition but if they came after the piston broke and not before it broke it isn't the cause of the main problem, detonation is. What is the easiest way to prevent detonation (or pre-ignition) on an engine that is running proper timing? More octane. You might not make more power but your safety buffer just got a whole lot bigger. |
Pete Pete Remner Ultra Moderator Location: Cleveland, Ohio Join Date: 01/11/2006 Age: Midlife Crisis Posts: 2,022 |
The tunes in question come straight from Ford, I think. Pete Remner Cleveland, Ohio 1984 RX-7 (rallycross thing) 1978 Silence is golden, but duct tape is silver. |