FYI: Coyote 5.0 Plasma Transfer Wire Arc cylinder liners

[88lx50]

Right from day one with this engine Ford have tweaked the spark map for piston rattle. The oem data correction is labled "Rattle". It looks like they will tweak it some more. This is real engineering at the coal face of the profit-performance mine.

How do you know that? Not doubting you, just wondering where you got that info.

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[engineermike]

That is interesting.

I noticed what sounded like piston rattle on my 2018 5.0 since new. It's always at light load between 2 and 3000 rpm. I ran it hard and it never got worse, so I added a Whipple several thousand miles ago. I've heard that noise before on race SBCs and it never lead to a failure so I didn't worry too much.

Conversely, I've wondered how Ford was making cast aluminum pistons that hold up to 800, 900, even 1100 rwhp without breaking the first time you you hit it. Cast pistons used to break at 400 rwhp. I figured it must be the geometry. Rest assured, if you had a custom engine built 10 years ago to handle 800++ hp, it was going to make all kinds of unsettling noises. Now, Ford is supplying an engine that will handle multiples more power than most stock engines ever built. Complain too much and they might put nice quiet pistons in there that break at 600 rwhp like Dodge and Chevy.

 

[88lx50]

This is the oem data from a DI Coyote about a year ago.
I hope it shows.

That's interesting. Notice there is no retard below 2000 rpm where we are hearing it.

 

[CrashOverride]

Reread my post, that's exactly what I'm saying! Facts wont stop the inevitable.

BTW, I also had a BMW N54. Never had any issues, that 335i still remains 1 of my favorite cars I've owned. Lightly prepped it was an M3 killer.

I guess I wrote it wrong or maybe you misunderstood my reply - I'm sorry. I agree with you, many times on many boards, scientific, reliable & repeatable tests are few and far-between. If the placebo effect weren't as powerful as it is, then double-blind testing wouldn't be the gold standard in the medical testing arena.

I liked my 135i don't get me wrong, drove great, very quick, made a nice daily driver. I got rid of it because I really missed my clutch pedal. I didn't keep it long enough to experience some of the problems that 1addicts members talked about, but I did have a recall performed for something (I sold it in 2012 so I can't remember what it was for). I seriously considered getting another 1'er, but 6M decent examples were few and far between and the owners really didn't want to sell them (They were priced too high). The n54 was/is a great engine, but like everything else it does have some known problems (Some of which are inherent to BMW's like requiring a dealer to "code" a new battery).

 

[CrashOverride]

That's interesting. Notice there is no retard below 2000 rpm where we are hearing it.

That is interesting and unsettling at the same time. Retarding for reasons other than knock seem like a band-aid to a problem, not to mention the naming of the table. Nevertheless, if the retard was just for aesthetic reasons, then these 3rd gen motors should be able to have even better TQ curves if the correction was reversed. I also wonder if the very reason people are hearing the noise is because they aren't retarding at those engine speeds?

 

[engineermike]

That is interesting and unsettling at the same time. Retarding for reasons other than knock seem like a band-aid to a problem,

I wouldn't be alarmed by it. As with everything in the drivetrain, piston design is a large quantity of compromises to optimize durability, sealing, noise, dynamic conditions, cost, and probably dozens more. For instance, the piston diameter at the top is significantly smaller than the bottom. This is due to thermal expansion. How much smaller depends on how hot they expect the top to get. So smaller handles high temps better, but loses ring sealing and has worse noise characteristics. If they want the piston to hold up to 15 psi boost, then you will sacrifice sealing and noise. The piston isn't round either, and the wrist pin isn't directly in the middle. Offsetting the wrist pin has advantages and disadvantages, including noise and efficiency. My guess is that a team of engineers knowingly used a noisier piston design for any number of reasons, and implemented an ignition timing scheme to control noise. Another guess, and I'm reaching here, is that they didn't retard timing below 2000 rpm to avoid adversely affecting fuel economy (yet another compromise).

Other engines/vehicles have this table as well as the mustang.

not to mention the naming of the table.

I'm not so sure that table name came from Ford. The screenshot I think is from HPTuners, which is not the software Ford uses to calibrate these engines.

Nevertheless, if the retard was just for aesthetic reasons, then these 3rd gen motors should be able to have even better TQ curves if the correction was reversed.

If you'll notice, the retard is phased out and completely gone by 0.5 load. It isn't affecting WOT torque production.

I also wonder if the very reason people are hearing the noise is because they aren't retarding at those engine speeds?

Possible, but as stated above, you might be getting into fuel economy affects there so they intentionally left it at 0 deg there.

 

[engineermike]

Apparently, the piston rattle spark retard table was in the Gen1 and Gen2 coyote as well.

 

[CrashOverride]

I wouldn't be alarmed by it. As with everything in the drivetrain, piston design is a large quantity of compromises to optimize durability, sealing, noise, dynamic conditions, cost, and probably dozens more. For instance, the piston diameter at the top is significantly smaller than the bottom. This is due to thermal expansion. How much smaller depends on how hot they expect the top to get. So smaller handles high temps better, but loses ring sealing and has worse noise characteristics. If they want the piston to hold up to 15 psi boost, then you will sacrifice sealing and noise.

I knew about the sacrifices, but I didn't know about the taper on the piston. It makes sense though as it gets cooked while the bottom gets cooled by windage (I can't remember if the coyote has the oil squirters that others have). It does seem to me that now and in the past, FoMoCo has built in a lot of aftermarket-friendly (Almost to the point of encouraging it) compared to others that do pop at much lower boost/timing.

The piston isn't round either, and the wrist pin isn't directly in the middle. Offsetting the wrist pin has advantages and disadvantages, including noise and efficiency. My guess is that a team of engineers knowingly used a noisier piston design for any number of reasons, and implemented an ignition timing scheme to control noise.

I also didn't know it was not round, although I do remember hearing about Honda using oval pistons in F1 a number of years ago. I did know about the offset wrist pin. I've always bee intrigued by engine geometry and the Rod/Stroke ration comes up every now and then. Comparitively speaking, Ford gouges the cylinders more, they are limited by bore spacing, so they have to get their displacement by stroke. But they also have a shorter stroke than a LS or Mopar engine, so the Rod/Stroke ratio is unfavorable. On a side note, I'm also surprised it is an undersquare engine, bucking the trend of oversquare engines (Well, at least for Domestic V-8's). I suppose Ford can get away with it because of the outstanding flow of 4 valves, instead of trying to cram in two large valves.

Another guess, and I'm reaching here, is that they didn't retard timing below 2000 rpm to avoid adversely affecting fuel economy (yet another compromise).

Other engines/vehicles have this table as well as the mustang.

I'm not so sure that table name came from Ford. The screenshot I think is from HPTuners, which is not the software Ford uses to calibrate these engines.

If you'll notice, the retard is phased out and completely gone by 0.5 load. It isn't affecting WOT torque production.

Possible, but as stated above, you might be getting into fuel economy affects there so they intentionally left it at 0 deg there.

I think you are probably correct there with the retard/emissions/economy thing. Whether it is right or not, manufacturers are doing their best to keep the engines from spinning more than 2k for EPA testing. I got a dodge that will happily upshift into 6th, going uphill, with the not-so-torquey 3.6L Pentastar, and it will lug it at 1100 RPM and requires more than 50% throttle before it reluctantly downshifts.

I haven't played around with monitoring loads but if "1.2" is max load, then 0.5 seems like quite a bit of a load to retard for not-the-greatest drivability, but yeah at WOT everything is on the table The onus was on me, my bad - I didn't look at the screenshot long enough to see it was HPT, so who knows what Ford actually calls the table. I have a feeling it isn't "piston rattle" though and instead "Acoustic management" or something of that sort.

Thanks for all the extra info!

 

[CB18]

now that you mention the oval pistons for formula one, If memory serves, they scrapped that because they never could get the piston rings right.

 

[engineermike]

I think we’re talking about 2 different things. Oval pistons have been in production engines for decades. I worked for a small engine manufacturer over 20 years ago and their standard was oval pistons. They chucked the pistons in the lathe “cocked” (piston centerline not parallel with lathe centerline) to machine the OD. This process was automated and yielded a slight oval shape. It seemed like a novel idea at the time but in hindsight it seems rather crude compared to modern machining capabilities. Anyway, the idea was that the piston thermally expanded more on one axis than on the other due to the wrist pin boss material, so machining out of round resulted in round once hot. And again, the amount depended on how hot you expected the piston to get.

 

[VooDooDaddy]

A lot of good info here.

Can anyone explain to a dummy what is the point of the retardation starting at 2,000 rpm? What would happen if it wasn't there?

Like many, my car when at certain load it rattles like a baby's toy. But as soon as you give it throttle it goes away.

When it comes to ignition timing, you need to remember that when the fuel/air mixture is ignited, the flame front will move through the cylinder volume at a constant rate. There is no way to speed up or slow down the burn rate. It is what it is. However, as we all know, the piston speed will change with RPM. The reason ignition timing is increased with engine speed/rpm, is that you don't want the piston outrunning the flame front as the piston is moving downward in the piston bore. On a single-cylinder, 4-stroke engine with little or no flywheel mass, this would be theoretically impossible as the flame front propagating through the cylinder volume would be the only thing pushing the piston downward in the bore upon the power stroke. Igniting the fuel/air mixture before the piston reaches the very top of it's travel in the bore (before top-dead center) allows the fuel/air mixture to be burned without the piston outrunning the flame front on its downward travel during the power stroke at high rpm/high piston speed.

On a multi-cylinder engine with a lot of reciprocating inertia, you are going to have other cylinders rotating the entire assembly upon their power-strokes as well. The key is to find the sweet spot in the ignition curve that allows the fuel/air mixture to ignite at the optimum point to allow the most amount of force to be exerted on the dome of the piston, thus pushing it downward in the bore with the maximum amount of force, but without initiating the "explosion" too early to the point the flame front spikes in one focused part of the dome of the piston to cause any damage.

Retarding the ignition timing reduces the probability of any pressure spikes in the cylinder which might cause damage to the piston. These pressure spikes are often called 'pre-ignition' and may be causing some of the "rattle"? But at this point, who the hell knows?

 

[ihc95]

Well this thread has certainly turned around for the better. As an engineer myself (not an ICE engineer by any means tho) there are certainly some interesting points being made about engine design and compromises. Also, I was not aware of the retardation on the Coyote engines. This is reassuring to me since it seems like Ford is acknowledging that piston slap is an inherent characteristic of the engine and not an unfortunate anomaly for some owners. However, I am still curious as to why some cars sound so much worse than others.

I appreciate the great insight and discussion going on here

 

[GT Pony]

I think we’re talking about 2 different things. Oval pistons have been in production engines for decades.

Yep, and the reason is because only the skirts takes the thrust loads of the piston as it moves up and down in the cylinder. Only the skirts are coated on pistons with an anti-friction coating. No reason to make the sides perpendicular to the thrust direction the same diameter below the ring land area.

 

[GT Pony]

I knew about the sacrifices, but I didn't know about the taper on the piston. It makes sense though as it gets cooked while the bottom gets cooled by windage (I can't remember if the coyote has the oil squirters that others have).

I know the Gen2 Coyote has piston squirters since they are shown in the service manual. I'd say the Gen3 Coyote probably has them too for piston cooling purposes.

 

[GT Pony]

However, I am still curious as to why some cars sound so much worse than others.

Most likely inconsistent manufacturing tolerances and QA. If it was a big design snafu, then all engines would have the horrendous noises. - but that's not the case.

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