2.8L Astron. TURBO or NA?

[webby]

I'm an NA junkie so you can guess what my answers gonna be

[Rallyant]

I'm an NA junkie so you can guess what my answers gonna be

Turbo?

[webby]

Yup:D

[shuggy]

yeh NA all the way

[Billsy]

simple opininions aside, i would go turbo because you will get MUCH more power and torque, and wont have to try and make it rev.
a good sized turbo will be on boost around 2500rpm and could make an easy 300whp without having to rev high. by the stroke of it its not sounding like a hi rpm engine.
so to me the boosted option sounds the go, even a supercharger would be a good choice on it.

[karl_2ltgc]

Turbo.

Extra capacity will let you run a bigger turbo with less boost less lag and more power

[Superscan811]

After a long hard think, I've decided to go turbo. Can't think if a better way to "Stress test" my engine design.
I'm planning to lighten the crank a little bit. Something along the lines of this.







After removing the metal from the Big-end, I'll reduce the OD on the counterweights, reduce the throw angle a little, knife edge the OD and trailing edge and round the leading edge



I was also thinking of "Gun Barreling" the Big-Ends, but for a Turbo engine, I don't believe it would last.




Thanks everyone for your input.

Cheers.

[Billsy]

i wouldnt remove any metal from where you have marked on the big end, youll likely weaken it dramatically.
nor would i chop that much from the counterweights.
also theres oil galleries in the crank, the "gunbarrelling" as you put it would just bore through them making them useless

with the capacity you have youll want to retain some weight in the engine rotating assembly, it will make it MUCH smoother/easier to drive (especially at low rpm) and realistically will make fugg all difference to the output if you leave it there.

[Superscan811]

i wouldnt remove any metal from where you have marked on the big end, youll likely weaken it dramatically.

I'm going to consult with a few engine builders BEFORE I start doing any major lightning of the crank, although the metal removal on the 2nd picture,

is quite safe, as it serves no real purpose with the reduction in bearing width.

also theres oil galleries in the crank, the "gunbarrelling" as you put it would just bore through them making them useless

It was suggested to tap the oil holes before grinding and gun-barreling the big ends. This would allow you to put in a hollow thread bar for the oil passage after.
There is a lot more to it than that but you get the idea.

Cheers.

[Billsy]

its nothing i would consider for what your building, considering what little benefit you will gain from it vs the time and effort in doing so.
but none the less, ill be interested to see how it goes once you do it.

[Rallyant]

All looks like a good idea to me.

did you have the crank linished? doesn't look super smooth in the pics.

[Superscan811]

did you have the crank linished? doesn't look super smooth in the pics.

Not yet. I'm going to get that done then cryo'd but only after I finish lightening it, just in case I put any marks on it.
I wasn't sure if the 6mm narrower big-end diameter, 5mm narrower big-end width and the 3mm offset would interfere with the oil holes,
and if it will hold together after all this work, so this is more or less just a "TEST" crank, just to see if it can be done.
Ideally, a billet crank with twin counter-weights per big-end would be the go, but I can't see that happening in the near future.

BTW: Does anyone know where, in Sydney, I can get a crank tested for flex? The flex values would be good to know for a standard crank and a modified one.


Cheers.

[cheaterparts]

BTW: Does anyone know where, in Sydney, I can get a crank tested for flex? The flex values would be good to know for a standard crank and a modified one.


Cheers.

Scott just rev it till it breaks and back it off a couple of hundred revs from there -lol

[81GL]

Scott just rev it till it breaks and back it off a couple of hundred revs from there -lol

LMFAO

[Superscan811]

Well the 2.8L is officially "ON HOLD".

The 2.8L crank doesn't inspire much confidence in me so I will make a billet crank later (one of the joys of owning your own CNC mill ).

I have a spare engine, turbo, pistons, turbo exhaust manifold, W58 gearbox and bellhousing and an ECU, so I may as well build a mild turbo 2.6L engine.

I've already started on the head, "blending" the ports and chamber so as to remove restrictions in the ports and remove possible hot spots and shrouding in the combustion chamber.

I'm not trying to enlarge the ports, just smooth them out and reduce the amount of material around the valve guides. Not always a good idea with a turbo engine because the "excess material" also helps to remove heat from the valves.

This is one of the reasons I will be using Bronze valve guides rather than the standard ones.
I'll also be getting the guides Nickel coated on the inside to help reduce wear.

I'll be running 1mm larger Stainless valves (hence the new valve seats) for my turbo engine, along with bronze valve guides from a Sierra Cosworth.

The standard M7 combustion chamber has a lot of sharp edges that can cause "hot spots" which in turn will cause detonation, ie: DEATH for the pistons.

When I finish "playing", the head will be decked 1mm, to compensate for the material I removed from the combustion chamber blending.

The pictures aren't good but you get the idea.













Cheers.