PDA

View Full Version : Cyl #4 failure (not mine thankfully)


Streetfighter
26-04-2011, 12:29
The age old pattern of piston number 4 failures is coming in on stage 2 mapped meganes (not to scare any of you running it, still on single figure failures)
Do any of you knowledgeable people know the type/specification of the fuel pump fitted on the Megane 225/230s please?
I'm wondering what its limitations are as there seems to be little mention or concern of it's capability to supply fuel for 350hp which I'm not entirely believing, but I'm running out of alternative reasons for failure.
Any ideas, even If I've heard them before will be much appreciated, I know there's some great knowledge and experience on here :D
Matt Cole
26-04-2011, 13:11
As far as i know, the filter and pump unit are all one and located in the tank. I think to change the filter you have to replace the full lot. Flow rate is 1.3 - 2 litres/minute at 3 bar.

Which cylinder are you classing as no.4?
Streetfighter
26-04-2011, 14:17
As far as i know, the filter and pump unit are all one and located in the tank. I think to change the filter you have to replace the full lot. Flow rate is 1.3 - 2 litres/minute at 3 bar.

Which cylinder are you classing as no.4?

What regulates the pressure?

The cylinder furthest away from the flywheel.
Matt Cole
26-04-2011, 14:39
What regulates the pressure?

The cylinder furthest away from the flywheel.

There is a pressure regulator fitted next to the pump assembly. Unfortunately no reference is taken to the regulator so the pressure does not vary with engine load.

I would be looking at getting rid of the intank thing, fitting a remote adjustable regulator in the bay with a reference and have an inline pump fitted, rated for better flow. Up the fuel pressure to suit the map. FYI the standard injectors are 390cc.

Not sure how on the standard setup 350bhp is being achieved??:scared:
Streetfighter
26-04-2011, 15:17
There is a pressure regulator fitted next to the pump assembly. Unfortunately no reference is taken to the regulator so the pressure does not vary with engine load.

I would be looking at getting rid of the intank thing, fitting a remote adjustable regulator in the bay with a reference and have an inline pump fitted, rated for better flow. Up the fuel pressure to suit the map. FYI the standard injectors are 390cc.

Not sure how on the standard setup 350bhp is being achieved??:scared:

Standard set up :laugh: Forged :D with 630cc injectors, decat, 3" exhaust + the usual trimmings.
The original engine was running 275 bhp & 326lbft and is dead. Long arm in deep pocket and forged engine appears. Question remains on failure mode of original piston #4 :coffee:
Matt Cole
26-04-2011, 15:33
Standard set up :laugh: Forged :D with 630cc injectors, decat, 3" exhaust + the usual trimmings.
The original engine was running 275 bhp & 326lbft and is dead. Long arm in deep pocket and forged engine appears. Question remains on failure mode of original piston #4 :coffee:
Have you a picture of a dead piston we can take a look at? 'Failure' is a very general word. ;) Looking at the piston can say athousand words and we may make a good stabb at the issue.:agree:
Streetfighter
26-04-2011, 16:04
Have you a picture of a dead piston we can take a look at? 'Failure' is a very general word. ;) Looking at the piston can say athousand words and we may make a good stabb at the issue.:agree:

Haven't got any here, will get some. Just had a peek with the borescope as the engine is still in the car. Thanks :)
Streetfighter
20-07-2011, 10:12
http://i1217.photobucket.com/albums/dd398/steven878/engine/SDC10089.jpg
http://i1217.photobucket.com/albums/dd398/steven878/engine/SDC10091.jpg

I believe it's simply the fact the pistons are cast from bottom to top, not top to bottom and the cold front on the molten alloy is flawed as the two halves meet. Stress it and it cracks, simple
Alastair
20-07-2011, 14:03
I would say that it is more likely to be an inclusion of foreign/slag material in the casting material than that... forming a stress raiser etc...
Streetfighter
20-07-2011, 20:37
Similar result either way?
Bit of an egg/chicken question.
Other possibility is rod bolt failure.
Definitely no det anyway
Matt Cole
20-07-2011, 21:28
Difficult to see in the pics, but have a look for any chrystalising of the fracture faces. Even if it is material fatigue, it doesnt really explain why all the failures are on cylinder no. four? Are there any signs of the piston 'picking' up in the bore? Any blueing or heat spots on the pin?

Have a look and see if the oil jet for that cylinder is clear/working.:agree:
Streetfighter
21-07-2011, 14:17
^^ Thanks, will look a bit deeper and come back. Just some early phone pics as the engine was being swapped over.
Matt Cole
22-07-2011, 09:05
^^ Thanks, will look a bit deeper and come back. Just some early phone pics as the engine was being swapped over.

No problem matey. It's an interesting one and could do with sorting if it's a common issue.:agree:
Turbofreak
07-02-2012, 21:37
New poster! (less than 10 posts)

We had a few here in SA with piston one going with the ring landing and was said to be injector fault related basically not being able to supply enough fuel as the injector stop flowing as it should , and obviously our quality of fuel isn't as good as there in europe