Stock Fuel Rails, why they don’t keep up

[2fast4u]

I agree with jack, I always opened 2nd ring .010 to .020 further than top ring for that very reason when building for forced induction...gives a little more room for expansion.

 

[Speedy!]

Very interesting, and that table doesn't designate between standard Hellcat and Demon/Redeye 6.2L. I'm very surprised to see the Hellcat 6.2L ring gap tighter than the NA 5.7 Eagle engine, but maybe it's more emissions related and barring that the engineers would spec a wider ring end gap.

@16GoManGoHC2 can you measure your rings to see if they match that book?

Years ago there was a rumor of a stock 5.7 Eagle that was taking like 11psi of boost. Unheard of at the time as 7-8psi was the max recommended. Then a guy who knew a guy who's aunt knew the uncle's dog said the engine had actually been disassembled and the rings opened up and that's why it was surviving that boost.

Yes, it was cylinder 7 in my original engine that bit the dust. Some folks commented on the YT video that they bet the ring(s) got hot, expanded, and seized the piston in the bore.

 

[16GoManGoHC2]

The problem isn’t the top ring, it’s the 2nd ring. It’s been suggested that the 2nd ring gap is too tight, and the pressures exerted on it are forced up to the bottom of the top ring which is the wrong direction, because there is next to no material above the top ring.
When you build the race motor I think you open the 2nd ring even more than the first to help prevent that.

Agree, my second ring gaps where .024-.029, plenty larger then the top to not trap pressure and induce top ring flutter which pressure between them can create. The top ring gets all the heat, especially how close they are to the top of the piston. Add to this stock piston to wall clearance was only .001” but pistons looked like the day they came out of the box, literally. The skirt coatings looked absolutely brand new snd untouched. Pin bores tight as hell, in fact until the piston gets to about 200F the pin doesn’t float in the piston. I’ve never seen such a tight engine build. Main bearing clearance was .0008-.0009” and rods .0010 to .0012”!! I measured this engine over and over and over with 3 different ever increasing accurate measuring devices and all it told me was it was even a hair tighter then previous measurements. New engineering engine clearance philosophy is tighter with a good thin oil created a better and larger around the circumference hydrodynamic oil layer then looser and thicker oils of old school thought. And this engine autopsy proves it works!! The bearings all looked an measured new. Except for top ring gap needing to be opened up about .005-.008” this engine probably would have taken 1000-1050 wheel all day long and stayed together for a long time. If me new rods and high dollar DLC coated pins where not of .927” size I would contemplate reusing stock pistons and bearings in the rebuild!!!

 

[16GoManGoHC2]

Very interesting, and that table doesn't designate between standard Hellcat and Demon/Redeye 6.2L. I'm very surprised to see the Hellcat 6.2L ring gap tighter than the NA 5.7 Eagle engine, but maybe it's more emissions related and barring that the engineers would spec a wider ring end gap.

@16GoManGoHC2 can you measure your rings to see if they match that book?

Years ago there was a rumor of a stock 5.7 Eagle that was taking like 11psi of boost. Unheard of at the time as 7-8psi was the max recommended. Then a guy who knew a guy who's aunt knew the uncle's dog said the engine had actually been disassembled and the rings opened up and that's why it was surviving that boost.

Yes, it was cylinder 7 in my original engine that bit the dust. Some folks commented on the YT video that they bet the ring(s) got hot, expanded, and seized the piston in the bore.

I removed and measured every one LOL. Tops where .018 to .020 except for 2 and 8 which where bigger at .022 and .024 and 7 huge at .032”. I think they got this way from butting and wearing hard on their OD’s pushing hard against the bores while in a butted state, 7 because it had so much ring directly exposed to the combustion chamber with the brow piece gone. Amazing the cylinder bores showed no signs of wear both visually and with a .0001 graduated bore gauge.
Interesting to note as it drove me bonkers with main bearing clearance as I was getting main bearing clearance at .0002-.0003” was until I but those tiny 8mm side bolts in and torqued them to the rated just 25 ft lbs doing such openness the mains up by .0006” and put clearance on all 5 at .0009”. New C bearing replacements where exactly the same as removed bearing thickness’s to within .000025”!!! Yes, that’s 4 zeros and a 2!!
Here’s the bare block with torqued caps waiting to go to the machine shop for cylinder bore honing.

 

[Speedy!]

So top rings were right in spec, what about the second ring? .0197 - .0299?

It's good to finally get someone that knows what they're doing to look at this stuff and share it

 

[16GoManGoHC2]

So top rings were right in spec, what about the second ring? .0197 - .0299?

It's good to finally get someone that knows what they're doing to look at this stuff and share it

That info on second ring gap dimensions posted about 3-4 posts above this, second rings where .024” to .029” so they where all right in the window except for #7, it was worn out to .035”. Here’s the actual stock ring gap numbers top down 1 to 8.

 

[Speedy!]

Cool. This info prompted me to fatten up my 93 tune wot fueling a bit above 6200.

 

[fubar569]

Cool. This info prompted me to fatten up my 93 tune wot fueling a bit above 6200.

Curt hasn't steered me wrong yet but I'll probably mention these findings to him as well.

Car has been pretty good to me so far. Looking forward to getting the jokerz blower here in 4 more weeks.

 

[Jack_Toepfer]

Is #7 the last to get fuel? Coolant? Oil? What makes it special, other than it’s a glutton for punishment?

 

[16GoManGoHC2]

Is #7 the last to get fuel? Coolant? Oil? What makes it special, other than it’s a glutton for punishment?

That’s a mystery we all want to know the answer for LOL. #7 is actually first to get fuel in its fuel rail. #2 is another problem child and was my only known engine issue from 2 years back that I have been monitoring and why I did a leak down test this winter to check it and found the problem with 7 in the process which triggered me doing my engine this winter not next as originally planned. I have to wonder if 2 and 7 are first in line for fueling changes triggered by the wide bands and they don’t get the extra fuel command as quick as the other cylinders see it if they are next in line to see the change request the others have more time to actually get the fuel then 2 and 7 do?? I think that is why @Speedy! said he was going to fatten up his 93 tune up top to make it safer.

 

[Jack_Toepfer]

If I recall correctly, Ford had custom fuel/spark maps for their “#7”, and I believe it was for emissions. I believe they were dumping fuel into it to get the cats up to temp sooner. Anyone seeing anything similar in the Hellcat? They don’t do it to all cylinders and if it’s in the cold start tune, I’m not sure anyone would be looking at it, as that is in the open loop tuning, I imagine.

 

[16GoManGoHC2]

If I recall correctly, Ford had custom fuel/spark maps for their “#7”, and I believe it was for emissions. I believe they were dumping fuel into it to get the cats up to temp sooner. Anyone seeing anything similar in the Hellcat? They don’t do it to all cylinders and if it’s in the cold start tune, I’m not sure anyone would be looking at it, as that is in the open loop tuning, I imagine.

Unfortunately I’m no where near knowledgeable in tuning to know, I’m a novice who can cut and paste stuff and review logs for some stuff but that’s about it unfortunately.

 

[Speedy!]

I believe on the Ford platform you can control fuel per cylinder. On the Dodge platform that's not possible, at least from what I know. I've heard of several Hellcats having a problem with cylinder 7 now. It's gonna either be fuel, which really means temperature, or something with how that cylinder is shaped maybe more friction or something, which also means more temperature in the end. Heat it up a bit too much rings touch and bad things happen.

For reference, my 93 octane tune was setup to run 11.49 AFR (about .83 lambda) on 93 octane. Now above 6200 I have it gradually increase fueling to 11.3 for a bit more cooling at those RPMs. This is a reason E85 is so good in these cars, you get 30% more fuel volume right off the bat PLUS the extra cooling effect of the ethanol.

Most tuners I know run them a bit richer so I imagine Curt's tunes are fine as is. A lot of tuners I've talked to shoot for 11.0 AFR (.80 lambda) to account for crazy stuff owners might do, like back to back to back WOT pulls or something. In a factory tune cat over temp would take care of that, but I don't know any tuner that leaves COT turned on, myself included. You don't want it too rich or it's hard on cats and other things.

 

[16GoManGoHC2]

Off to the Engine shop for honing we go!! Hurry home sweet heart

 

[Hpindy]

We seem to build doing parallel builds .

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[Hickster]

I have had mine replaced 3 times under warranty.

 

[16GoManGoHC2]

We seem to build doing parallel builds .

Sent from my BBF100-2 using Tapatalk

Unfortunately your going to beat me by miles as I decided to go a different route on pistons then the ones I had and the custom features I want built into them is going to put them out 6 or so weeks But it’ll all be worth the wait in the end. My Capri LOVES the cold weather of early spring and she’s my best track car consistency wise so I won’t be on the sidelines totally till the cats ready to claw again. Time to fill the NOS bottles for the older lady.

 

[Hickster]

Come to think of it,,,, the factorry rep from the fuel rails to the everything from the fuel rails to the converters. Gaskets thru the whole system. 3 times. I ain't bitchen about it. All I am bitchen about is the damn battery. Going to have to get it flat bedded to a high performance shop to change out a damn battery. Latch want un latch and with me having a broke neck, no climbing thru the back seat.

 

[Hpindy]

Unfortunately your going to beat me by miles as I decided to go a different route on pistons then the ones I had and the custom features I want built into them is going to put them out 6 or so weeks But it’ll all be worth the wait in the end. My Capri LOVES the cold weather of early spring and she’s my best track car consistency wise so I won’t be on the sidelines totally till the cats ready to claw again. Time to fill the NOS bottles for the older lady.

It's definitely worth the time and effort.

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[Hickster]

Battery 1st thing,,, what a disaster. This has turned into be.