pearlpower

Noticed the cylinder #8 issue has been brought up a few times. Curious what kind of damage has been reported, remedies, etc. Can this be adjusted in a tune? Higher flow injector for just this one cylinder?

chiromikey

it's my lowest compression cylinder...

Forrest Gump 9

What's happened Mikey??

chiromikey

nothing...number 8 is still within 10% of the other cylinders, but it's always had the lowest compression. just wanted to share my findings because i too think it's more than a coincidence.

MBH motorsports

I believe the #8 issue is because its the last cylinder to get fuel.

Benz-O-Rama

#8 is the the last in firing order on these cars?

g.smiley

My 8 blew. Required an 9 week rebuild. Sucked. Luckily under warranty.

Hotrod-Realtor

I bet the blower forces more air to the back cylinders causing more cylinder pressure and or a leaner cylinder. But hey, what do I know.

MBH motorsports

Yes

pearlpower

Can you provide details? Detonation? What kind of damage was there?

Seriously thinking a higher flow injector is in order for #8.

loungn14

Thats what we found as well, and also why when we released our injector set, we had one injector flow more then the rest for #8

AgSilver

The SLR rail uses a dual feed with two pressure regulators.

lightningfast7

Is it a cooling issue? I know some of the Ford V8's had a problem with no exit for the coolant in the back of the heads so they created a bypass to alleviate the problem. I believe it was the #8 cylinder as well..

nick 55

The SLR has a single feed, with 2 fuel pressure regulators. I know it isn't a fantastic pic, but here is one of the rail. The coolant exit to the heater core is on the left bank at the back of the head, right behind the #8 cylinder, so I doubt that is the issue.

Nick

blackbenzz

Isn't cylinder 8 furthest from the water pump/radiator though? So it would get the hottest in theory

Forrest Gump 9

So I guess I should keep my 160 degree thermostat in then.

OZZYAMG

Hi

I know this is an older thread but where exactly is cylinder number 8 located?

Is it closest to the headlights or closest to the cabin of the car?

Using the US left hand drive car as an example is cylinder number 8 on the drivers side or passenger side?

---

Does anybody know if we install a wideband o2 sensor can we install it about 2 inches after the exhaust outlet of the head so we can get readings just for that cylinder only and be able to install and remove the wideband o2 sensor without getting underneath the car?

Regards,

OZZYAMG

chiromikey

Standing in front of the car counting from front to back, 1-4 are on the passenger side and 5-8 are on the driver side.

The problem was determined to be the design of the fuel rail. Because the fuel inlet is closest to #8, the pressure is the lowest. When fuel requirements increase due to mods, a modified fuel rail is highly recommended.

Sir-Boost-a-Lot

iTrader: (1)

What you'd want instead of a single WB would be an EGT gauge .

OZZYAMG

Hi

Ok thanks for the replies so far.

I would have liked it if I could monitor the afr's with particular attention to cylinder number 8 and have it connected to an all in one device that could log afr's and rpm for like a 60 second period as well.

I suppose I better learn about EGT sensor's.

So just to confirm in the US W211 E55's cylinder number 8 is the closest cylinder to the driver of the car?

Regards,

OZZYAMG

chiromikey

Yes, #8 is closest to the driver.

AgSilver

Power peaks right at 125 F below peak EGT. Smokey Yunik, The Great God Of Combustion knew this. For years, competitors wondered why each header tube on his motors had an 1/8" hole with a plug. Yunick always ran 180F or higher thermostats as he knew heat (in the proper location) = energy.

chiromikey

Very good point. This is one of the reasons that as soon as i split my i/c cooling system from the engine cooling system I put my 180* thermostat back in!

Exotic-metal55

I have tore down and or inspected over 25 blown motors now and have seen #8 go a lot but lot of times, but usually several other pistons will be damaged as well, just may not be so obvious. Lot of times, other pistons still hold compression but will have cracked lands. I have seen #7 and also #2 and #6 go a lot.

I do not see #8 as being a weak link to fix, but maybe just the piston that tends to go first, when you already have other issues. As mentioned, #8 may detonate first but it is rarly the only hole that detonates when #8 melts. We study the micro metals that show up on the valves of blown engines, to show how many holes had aluminum particles starting to come off of each piston. So even if you take #8 out of the loop to blow, we see other pistons only being mili seconds from going next.

Weak links once you add 100 RWHP. (I use that number, as it takes a lot more tuning, stronger parts, cooling, fuel and other heat removal mods.

1) stock piston ring gap is way to tight and heat builds up between rings and detonation can happen fast.
2) larger injectors needed and more tuning with that change, plus stock fuel rail and lines become undersized.
3) 3 valve heads need exhaust help with lot of added power.
4) fuel rail inlet is 5-6mm id only and on 90 deg location to rail.
5) managing iats takes a lot more work and remember that tight ring gap.

Just a few things I have noticed over the years.

OZZYAMG

Hi


Thank you Exotic-metal55 for your very informative post.


Regards,


OZZYAMG