9 replies to this topic

[blackoctagon]

As this is essentially a die-cast aluminium pressure vessel there is not much that can be done to this part.

Considering pressure vessel design methods for a tapered shell (the rail is not a parrallel-wall cylinder) and reducing the material properties for the aluminium by a big chunk to take account for it not being 'good' aluminium meant that I did not want to dig into pressure retaining wall thickness.

All things considered I don't think I could do a better job of making a totally fresh part in terms of weight or function unless I want to change the Fuel Pressure Regulator arrangement. Even then a FPR blanking plate would still be a better solution if an external FPR was going to be used, so the GM part is living on.

But there is still redundant metal in there that is not taking any load.

0.623kg starting weight:


Casting runner pad marked for removal:


Casting flash for cleaning up:






The fixing brackets have one hole each to attach them to the top of the cylinder head and the bolts act in a combined tension and shear to the reaction and vibration of the injector pulses. The tight fit of the injector alone in ther bosses would probably do this job, but no-one in their right mind would take such a stupid chance.




The fixing brackets were then trimmed of the excess bolting pad material. I elected not to trim all the excess bracket web off - spreading the load over a bit more vessel wall is prudent.



The design of the part makes me think a version of this casting is used on other engines in the GM range.

From measurements on the inside of the rail the rib on the top around the threaded fitting is more of a casting convenience than a structural design feature so I scalloped it. If I can get to a mill before I fit it i'll shave it down more and just leave some thickness around the fitting.


Fina weight 0.607kg. 0.016kg saved.


Totally worth it.

[paul_mck]

can you buy an aftermarket fuel rail?

[FLD]

https://www.overthet...Rail_p_100.html

[OneYet]

Maybe not a lot of weight saved but a brilliant post. 

[FLD]

Every little bit matters...…..(said the batman to every girl he's met)

[FLD]

These weight analysis threads are interesting.  I'd be curious to know how the bigger oily bits fare.  For example, most favour a saab head (because it's better innit).  The saab head has benefits in that it is stronger and not subject to bowing with large cylinder pressures up to something obscene like 1200bhp whereas the Z22 head needs staking.  It also can take a larger porting due to extra metal in the casting but the z22 head seems to be used in the build book way above what we put out so must flow OKish.  Is the extra saab head weight performance outweighed by its lardiness?  Same can be applied to gen3 blocks, is a deckplated gen2 block lighter.  The 2.2 crank is fully counterweighted but the 2.0 and 2.4 cranks are half counterweighted; is there a saving here? 

 

I guess where my ramblings are heading is the question of where is the weight penalty worth paying for either reliability or performance?

 

Now I'm off to gun drill all my bolts (ETA stating with the sump bolt )

Edited by FLD, 03 December 2020 - 01:07 PM.

[hairy]

Now I'm off to gun drill all my bolts (ETA stating with the sump bolt )

 

Is that a euphanism?

[FLD]

 

Now I'm off to gun drill all my bolts (ETA stating with the sump bolt )

 

Is that a euphanism?

 

 

Not intentionally!
 

[Gadget2]

When I was sprinting my Westfield, the Wife and I went to a car show at Donnington.  On one of the stands was a pair of alloy front uprights for sale.  "I would like to buy those," I said. "Why?" said the Boss. 

 

"They would give me a faster turn in, not handed so I only need one spare and also would save 2Kg in weight"

 

She patted my belly and said "What about that weight then!"

 

Never did buy them..........

[blackoctagon]

FLD,
I'm looking at that billet fuel rail and thinking billet for billet's sake.
I'd take a free one, of course, as it looks fantastic, but functionally you're using a square section part to do a job where the stresses are better handled by a circular one - no corners. I'm sure that thing can take many, many Bar, but to what end? There are not many people in indirect injection applications needing to contain more than around 5 Bar (73Psi).

If you follow the American engine scene - all of it, not just Ecotecs - you can find a lot of examples of billet parts where cast would be significantly lighter to do the same job.

There are pefectly reasonable times to use billet material -
The cost to cast is too high vs. buying a slab and using a machine/machining centre you already have,
The loading on the component is such that you want the metal's grain flow to be in certain directions to improve resistance to loading/give fatigue life and with a known/certified piece of material you can get that,
The cost to forge and trim is higher than just machining.

For rotating applications the material should be quite homgenous in it's density and so need less balancing after being manufactured to shape, but for things like wheels i'd probably still choose forged (where the grain flow is more shaped to the part itself) as most i've seen are tougher than ones from a billet with a (mostly) unidirectional grain.

All of that said, billet parts always look so special and I do wish I had the equipment to build some.

OneYet,
Thanks. I try as hard as I can manage.

FLD (again),
The B207 (and it's family) should be heavier as they are sand cast rather than foam cast - the metal should be denser. At least that would explain why it cuts smoother and is not a total bitch to polish up the combstion chambers.
I have a ported head (z22se) which is down to the casting and valve guides in a box right now, and the head from the engine i'm working on (the one that has this fuel rail, also z22se) is awaiting strip down so I can get a pair of measurements for pre and post, but I don't have a sand cast head so I can't show evidence on it's weight.

I can't speak to the block question as I dont have any, but one thing i'd be sure of is that while they will be stiffer and stronger - I know they used a lot of the motorsport program data - some of the modifications will also be on noise radiation, so there may be metal in there that is useless for our idea of a good time, but better for refined passenger cars.
I've had a few ex-colleagues who have worked on redesigned blocks at VWAG, Volo, MG Rover and some others and, in their opinion, a disproportionate amount of work was done on vibration modes of the engine block to alter noise characteristics vs. time spent on performance improvement, cooling and stiffness.

Looking at the GM motorsport work the Gen1 is probably stronger than most VX owners would ever need, so the extra weight is probably not desirable, but the beneficial elements like deck layout and larger water galleries (and water mass) make it harder to consider.

Cranks; A bit like the block answer it may be that the 2.2 is meant to be the smoothest variant for the mass market and the shorter throw 2.0 and the longer throw and bigger pistoned 2.4 have some vibration characteristics that make them different. Certainly the balancer shaft delete dosn't seem to trouble most people who take them off a 2.2, so that would tally with a heavy crank.
Without seeing the different ones i'm not going to guess further, and I have my own crank to post about later, so i'll defer for now.

Gadget2,
I'm okay in the tummy respect, but it's a good point. I magine many Lotii-based cars run slower after christmas than in early December.......