M400 Expert required - Noise when starting from cold
Discussion
Fixanything said:
Is it normal for M400's to be a little noisy when started from cold ?, the noise I have is like tappets or a faint dieseling sound eg sounds even/consistent across the engine. The sound is slightly louder when under load however, completely goes once Water and Oil are at running temp ie both ~90C, engine pulls like a train (love it, fastest car by far I've ever owned), smooth, shows no sign of any other undesirable noises and does not smoke at all.
As I am new to Nobles it would be good to have a chat with somebody who really knows M400s in order to understand what to expect from the car.
Cheers
Fixanything
No, maybe cracked manifoldsAs I am new to Nobles it would be good to have a chat with somebody who really knows M400s in order to understand what to expect from the car.
Cheers
Fixanything
k all about M400'sFixanything said:
The car has the uprated (double plated/welded) manifolds and has done less than 15K miles, could it still be manifolds ?
Cheers
fixanything
Mark,Cheers
fixanything
Exhaust manifold could well be your problem, I remember now, mine had an annoying ticking sound (not the usual "puff") when first started, disappeared when I had a Roush exhaust fitted and manifolds welded.
F.C.
Fixanything said:
Just started from cold and went for drive, a 350Z wanted to play for little while 
. Listened again I'm sure its not anything to do with the manifold or exhaust, its just a faint general mechanical noise when cold, a little more apparent under load and gradually reduces as the engine warms up. May be it is normal and I'm just used to my old Rover V8 with hydrolic tappets. However, I would like for somebody local (Stansted Airport ish) that knows these engines to have a listen to put my mind to rest.
Cheers
fixanything
is it a grey one, was in Bishops Stortford on Friday?. Listened again I'm sure its not anything to do with the manifold or exhaust, its just a faint general mechanical noise when cold, a little more apparent under load and gradually reduces as the engine warms up. May be it is normal and I'm just used to my old Rover V8 with hydrolic tappets. However, I would like for somebody local (Stansted Airport ish) that knows these engines to have a listen to put my mind to rest.Cheers
fixanything
Really, from the description of the symptoms I can't see how it could be the tappets, thetappets pump up as soon as you have oil pressure, the symptoms you describe, as have been alluded to by several other people are still more likely to be piston related.
In fact your original description of the noise, its duration and the point at which the noise clears, are absolute textbook forged Piston behaviour? How many miles has the car done?
Still, regardless, if it is piston noise, its normal. (If it is tappets, which I can't imagine it will be myself) you may need to try and clear it by running some engine flush through it?
Mike.
In fact your original description of the noise, its duration and the point at which the noise clears, are absolute textbook forged Piston behaviour? How many miles has the car done?
Still, regardless, if it is piston noise, its normal. (If it is tappets, which I can't imagine it will be myself) you may need to try and clear it by running some engine flush through it?
Mike.
Mike Tuckwood said:
I'm with Tuxman on this one, forged pistons have a larger piston to bore clearance to allow for the expansion rate of the piston, if it's not especially noisy and settles down once up to temp, I'd suggest theirs nothing to worry about there.
Mike.
The thermal expansion coefficient of a material is strictly a material property and has nothing to do with how that material is processed (and the same applies to different alloys of the same base material). So forged and cast aluminum pistons will undergo exactly the same expansion for a given temperature increase. Increased cylinder/piston clearance is used in high-performance motors to reduce friction losses, and, of course, that increased clearance will often lead to piston "slap" as the motor ages, which necessitates re-building those motors at relatively low mileage.Mike.
Edited by JLSELAN on Monday 20th September 01:36
JLSELAN said:
Mike Tuckwood said:
I'm with Tuxman on this one, forged pistons have a larger piston to bore clearance to allow for the expansion rate of the piston, if it's not especially noisy and settles down once up to temp, I'd suggest theirs nothing to worry about there.
Mike.
The thermal expansion coefficient of a material is strictly a material property and has nothing to do with how that material is processed (and the same applies to different alloys of the same base material). So forged and cast aluminum pistons will undergo exactly the same expansion for a given temperature increase. Increased cylinder/piston clearance is used in high-performance motors to reduce friction losses, and, of course, that increased clearance will often lead to piston "slap" as the motor ages, which necessitates re-building those motors at relatively low mileage.Mike.
Edited by JLSELAN on Monday 20th September 01:36
While a simple argument might appeal to some, that does not make it correct.
The miss-understanding probably arises from the common confusion people have in distinguishing between the physical and the mechanical properties of a material.
Physical material properties (like density, elastic modulus, sound speed, expansion coefficient, etc) are fundamentally tied to the atomic structure of the material--see info here:
http://environmentalchemistry.com/yogi/periodic/Al...
whereas mechanical properties (like strength and ductility) depend on the processing history that a material has gone through.
The atomic structure of aluminum and all of its alloys is face-centered-cubic.
That means that aluminum and all of its alloys (which are solid solutions) share very similar physical properties, see some info here:
http://www.substech.com/dokuwiki/doku.php?id=prope...
The exceptions to that statement are a few alloys with unusually high concentrations of relatively heavy metals--but even those still have physical properties that are within a few percent of the base metal.
Again, although you can change the mechanical properties of aluminum by processing it (e.g., forged aluminum generally has a higher strength than cast aluminum), you cannot change its physical properties (e.g., a forged aluminum alloy has exactly the same density as the same alloy when it is cast).
And, BTW, aluminum and silica cannot be combined in an alloy. It is only possible to produce a composite mixture of these two materials, and the properties of that composite are governed by the law of mixtures. See for example:
http://everything2.com/title/Law+of+Mixtures
Another point to keep in mind relative to the original question is that the aluminum Duratec block -- and it cylinders -- are expanding just as much as the pistons as the motor heats up, so the clearance between the piston and the cylinder isn't changing very much until the piston gets quite a bit hotter than the cylinder wall.
The miss-understanding probably arises from the common confusion people have in distinguishing between the physical and the mechanical properties of a material.
Physical material properties (like density, elastic modulus, sound speed, expansion coefficient, etc) are fundamentally tied to the atomic structure of the material--see info here:
http://environmentalchemistry.com/yogi/periodic/Al...
whereas mechanical properties (like strength and ductility) depend on the processing history that a material has gone through.
The atomic structure of aluminum and all of its alloys is face-centered-cubic.
That means that aluminum and all of its alloys (which are solid solutions) share very similar physical properties, see some info here:
http://www.substech.com/dokuwiki/doku.php?id=prope...
The exceptions to that statement are a few alloys with unusually high concentrations of relatively heavy metals--but even those still have physical properties that are within a few percent of the base metal.
Again, although you can change the mechanical properties of aluminum by processing it (e.g., forged aluminum generally has a higher strength than cast aluminum), you cannot change its physical properties (e.g., a forged aluminum alloy has exactly the same density as the same alloy when it is cast).
And, BTW, aluminum and silica cannot be combined in an alloy. It is only possible to produce a composite mixture of these two materials, and the properties of that composite are governed by the law of mixtures. See for example:
http://everything2.com/title/Law+of+Mixtures
Another point to keep in mind relative to the original question is that the aluminum Duratec block -- and it cylinders -- are expanding just as much as the pistons as the motor heats up, so the clearance between the piston and the cylinder isn't changing very much until the piston gets quite a bit hotter than the cylinder wall.
Edited by JLSELAN on Tuesday 21st September 04:18
Thats a very simplistic view of things Joel, though in essence correct. 
It's the propensity to abbreviate that allows the opprtunity for such pedantry though.
As you well know and without boring everyone here with manufacturing techniques, tolerances piston design and metallurgy, Forged pistons routinely have more mass but more importantly, are stronger, so are pushed into environments which see much higher temperatures than cast (or Hypereutectic) pistons and as a consequence need more consideration in the piston to bore clearance areas.
Even the piston manufacturers still stick to the (admittedly not entirely correct) routine of stating that forged pistons expand more, they just don't feel the need to include the masses of complex reasons why.
Mike.
It's the propensity to abbreviate that allows the opprtunity for such pedantry though.
As you well know and without boring everyone here with manufacturing techniques, tolerances piston design and metallurgy, Forged pistons routinely have more mass but more importantly, are stronger, so are pushed into environments which see much higher temperatures than cast (or Hypereutectic) pistons and as a consequence need more consideration in the piston to bore clearance areas.
Even the piston manufacturers still stick to the (admittedly not entirely correct) routine of stating that forged pistons expand more, they just don't feel the need to include the masses of complex reasons why.
Mike.
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