2.8L Astron. TURBO or NA?

[Superscan811]

Just got my crank back for my 2.8L Astron and I'm trying to decide whether to go turbo or not.

It currently weighs 17.6kg

I'll be using the Arrow 6.4" rods which weigh 529g, the standard 6.535" rods are 830g.
As you can see from the crank, the big-ends are 6mm smaller than standard, so I now have a 104mm throw instead of the normal 98mm.
This will allow me to use standard 2.6L US Starion Turbo pistons (approx 8.3:1 CR) if I go turbo, or Normally Aspirated using standard flat tops (about 10:1 CR).

With the turbo option, I can either use the Garrett VNT turbo with the standard compressor housing (rated to 250HP) or the upgraded compressor housing I bought which is rated to 450hp.


The reason I am at a stand still with this project is the crank.

If I go Turbo, I can't lighten the crank too much because it will compromise the crank's strength,
BUT,
if I go Normally Aspirated, I can remove A LOT of weight out of the crank because it won't be putting out as much power (expecting 140kw at the wheels).

Ideas and suggestions welcome.

Cheers.

[psshhhht]

why is this thread even in existance? TURBO ALL THE WAY! ;) lol

[Billsy]

turbo FTW!

[81GL]

I want that crank! ( :wank: )
What are you doing about big end bearings? or is that cared for with the aftermarket rods?

What are you going to be using it for? track or street.

Personally NA... Just the thought of some side drafts matched with that...
Then again.... If your chasing power, then i guess its another turbo set up.

Nick

[shuggy]

yeh i rekon n/a.
2.8 is pretty huge for turbo, unless you want super crazy boost power N/A would still be amazing in a 2.8.
if it was me i would go n/a as i love the sound of twin side draughts and if your just using it for casual driving to turn heads it would be great.
but im a non turbo fan so its up to you weather you think its worth spending the extra money for the power you cant use (or not supposed to) on the street. you wont blow anythin up that way either

[Superscan811]

I want that crank!

It only cost $300 to get the crank ground.

2.8 is pretty huge for turbo, unless you want super crazy boost power N/A would still be amazing in a 2.8.if it was me i would go n/a as i love the sound of twin side draughts and if your just using it for casual driving to turn heads it would be great.

If I was going N/A, I would be using my Quad throttle bodies and EFI with the EMS 8860 currently sitting in my garage.




The cost of the set of 8 new forged Arrow rods, 8 pairs of the Clevite high performance rod bearings and a new set of 8 ultra light CASIDIAM coated titanium wrist pins only came to $700.
(ie:$350 per engine).

God I love EBAY...

For the turbo option, the new Garrett VNT turbo cost $550 and the new compressor housing cost about $150 delivered.

The parts really aren't expensive, it' just deciding exactly what you want to do with them that takes time.

Hence my dilemma.

Cheater is currently building my 2.4L short stroke Normally Aspirated Astron but I bought the turbo exhaust manifold off Carl and I was thinking that the 2.8L might be a better use for this manifold.

I have the EMS 8860 ECU which has been sitting in my garage for the last 12 months doing nothing, so at this point in time, either option, Turbo or Normally Aspirated should be very "INTERESTING".

I like the idea of a normally aspirated 2.8L just for the torque possibilities, but, a turbo 2.8L would be "VERY EXCITING".

Cheers.

[shuggy]

that quad body will still sound pretty mean.
good luck man im not and electronic anything man so im out hahah

[Superscan811]

that quad body will still sound pretty mean.good luck man im not and electronic anything man so im out hahah

In all honesty, I like old school, I even have a set of quad 40mm Kei-Khin motorbike carbies (similar to the SU carbies)
which I'm going to adapt to the Astron engine.
I had (20yrs ago) a set of 4 * 36mm carbies off a GSX1100 motorbike running my mildly worked 2.6L, which worked exceptionally well.

I just won another Redline Twin Weber Manifold which I will use for the quad 40mm Kei-Khin carbie conversion. Should be quite interesting.
I love it when people can't list items properly on EBAY.

EFI is definitely the way to go by the way, but I still like carbies for their reliability under harsh conditions.

I'd love a Turbo/EFI 2.8L just for the uniqueness of it, but still, it would be nice to blow away a few "Forced Induction" posers with a N/A 4cyl, just for fun of course...

Cheers.

[shuggy]

nice find mate!

very nice indeed

good luck with it, i had a set of quads of an ex police motorbike but i gave em to my neighbor for his bike coz he helped me out so much with my last project - i had no use for them as i did want to pass the pits haah

[75wagon]

If you can get those quads to work, go for it. It'll be original.... Sound sic too....

[81GL]

$350 per engine & $300 for the crank... ?
Alot cheaper than i had thought. I'm guessing your going to hang on to the other set of rods & bits for a 'rainy day' ?

I just won another Redline Twin Weber Manifold which I will use for the quad 40mm Kei-Khin carbie conversion.

...That makes me cry.

Nick.

[Rallyant]

Go NA, Then Turbo latter
I dont think it will be a problem if you lighten the crank for turbo also.
If you go with the turbos your looking at anyway. Thats not a HUGE HP turbo setup.
Id probably be more worried about those rods in a turbo setup? Be ok with the HI RPM, but im not sure what the compressive loads would be like with some boost?

I think im going to copy your setup! Still have that second set of rods?

What bore size did you go with? and what pistons?

[Superscan811]

I'm guessing your going to hang on to the other set of rods & bits for a 'rainy day' ?

Still have that second set of rods?

I actually bought 2 sets of rods and bearings (enough to build 4 engines). I want to make sure the first engine will hold together before I start building a 2nd one, or selling off the "spares"

Id probably be more worried about those rods in a turbo setup?

The Arrow rods definately aren't the weak point and depending on who you buy them from, a set of 8 rods sell for around US$1700 to US$2300.
They are supposed to handle in excess of 850hp in a V8.

What bore size did you go with? and what pistons?

The bore is 92.5mm.
For the turbo setup I have a set of Wiseco forged pistons.
For the N/A, a set of flat top ACL Duralites.

Cheers.

[Rallyant]

Id probably be more worried about those rods in a turbo setup?

The Arrow rods definately aren't the weak point They are supposed to handle in excess of 850hp in a V8.

aprox 425hp in a 4cyl then?, Not enough for my turbo motor, but if your going to limit your turbo build to that im sure you can lighten that crank as much as you would for NA ?
( going to have to keep my eye out for some of those rods!) still tossing up on the custom rod idea atm tho.

What bore size did you go with? and what pistons?

The bore is 92.5mm.
For the turbo setup I have a set of Wiseco forged pistons.
For the N/A, a set of flat top ACL Duralites.[/quote]
any idea on the weight of the Duralites? Have you looked at the Mahle forged pistons? I think there lighter and around the same price, $250 - $300(VW air cooled pistons)

[stealth]

go na
as when your rod bearing fails and it will it will
be cheaper to bin the lot
mate a massive concern is no support for the side clearance
and will lose oil pressure bad, just a thought im not picking
shit
cheers stealth

[astronturbo77]

mate my old man is a automotive machinist and has had a astron out to nearly 3L. all i can say is dont expectit to rev cos all you have done is made the stroke longer. probably better for turbo i reckon as long as the bore is standard and ur not using a magna block.

[DanTurboLancer]

Why not use the short stroke 2.4 for your Turbo build, and the 2.8 use the Quads?

I like the idea of the N/A and those mint Throttle bodies!
Keepin it old school

But you would be dissapointed if you jumped in someone elses Turbo....

Just a thought

[Superscan811]

mate a massive concern is no support for the side clearance

I was thinking of putting bronze washers on the wrist pins to help keep the rods centrally located but there is a 6mm section at the back of the big-end journal tapering down to zero on the opposite side which will help locate the rods correctly.
I was more worried about the rods "binding" if they slid sideways or skewed a bit.

and will lose oil pressure bad

The 3L oil accumulator was always going in there and I've been debating whether to use the higher flow forklift oil pump. Guess that's a yes..

just a thought im not picking shit
cheers stealth

As I said, ALL ideas and suggestions are welcome.
There are a lot of people out there with more experience in this type of engine build.
It's better to get this info and work out a solution now, rather than after the engine has destroyed itself.

all i can say is dont expectit to rev

Again another reason I was thinking of going turbo.

as long as the bore is standard

92.5 is a factory standard oversize for the 4g54.

and ur not using a magna block

2.6L wide block so I can use the Starion 5-speed gearbox.

Cheers.

[stealth]

if you can manage to fully support the rod "side on"
it will be ok but as lond as you dont have support the oil will blow
staight out (just like to much side clearance) so doesnt matter
how much you pump there's a great hole
and also make sure you deburr and radius those oil holes you
dont want to make that simple mistake
also theres no reason it wont rev more that like with those rods
and pistons it will get there quicker than most!
what are your rods made out of ? h beam or i beam ?
just my two cents
cheers stealth

[Superscan811]

what are your rods made out of ? h beam or i beam ?

I-Beam, Forged Billet Steel.


Cheers.

[81GL]

I'm guessing your going to hang on to the other set of rods & bits for a 'rainy day' ?

Still have that second set of rods?

I actually bought 2 sets of rods and bearings (enough to build 4 engines). I want to make sure the first engine will hold together before I start building a 2nd one, or selling off the "spares"

Will be watching eagerly then
(Keen if all goes well.)

Not sure how this will sound to those with more experience? Bit of an idea for the oil issue.
-Before getting the crank off set ground, have extra material welded onto the outside of the bearing area/surface. Then when the crank is re ground that will provided material for the side clearance to be properly adjusted???
If you follow that?

Nick.

[stealth]

yeah nick your think is correct but problem is that welded cranks
FAIL in a big way so yeah
you would get away with it in a low hp situ but whats the point
if he can make a broze slipper to go in there that might work
but its a guess
do you's want to buy billet 6340 cranks any stroke you want (within reason)
cheers stealth

[EVL076]

do you's want to buy billet 6340 cranks any stroke you want (within reason)
cheers stealth

MATE... just stop now will ya... you are gonna own me before long
will be going to work just to pay you

[leoca]

My votes for NA EFI followed by a turbo conversion...Like me!.
Hey Superscan what sort of a car have you got any way???, can,t find any info...

[Superscan811]

Hey Superscan what sort of a car have you got any way???, can,t find any info...

Currently, 3 GH Scorps, 3 GJ Scorps, 1 GN Sigma Wagon and a HH GSR Glalant (excluding the wife's Tarago of course).

The engines I'm building (and Cheater) are for the Scorpions. I much prefer the shape of the GE/GH Scorps over the later models but I have 2 GJ bodies in VGC.

A LC Hatchback with either a 4-point diff (or preferably an IRS) conversion, would be my ideal beast to drop one of the NA 2.6L engines into.

That will have to wait. But not for too long...

The contracts will be signed tomorrow so my shed can finally get under way (pending council approval of course).

Weird story but in the end, in about 10 Weeks, I should have my dream backyard workshop(105 sq meters), complete with a CNC Mill (already have the mill, just needed a shed to put it in).
The CNC mill is about 25yrs old but it has a 700mm*600mm*500mm machining area and a 24 tool auto changer. The Controller is capable of 6 axises (1 is used for the tool changer), so while it doesn't have a rotary table at this point in time, my brother has promised to give me one of his "castoffs" (along with a 40CFM compressor he has lying around his workshop gathering dust).

I noticed that a few people (in the "what is your profession" section) said that they are CNC operators, if you have had any experience with an ANCA-2000 controller, I'd be interested in picking your brains on what DNC program and post processors you know about.

Cheers.

[81GL]

Weird story but in the end, in about 10 Weeks, I should have my dream backyard workshop(105 sq meters), complete with a CNC Mill (already have the mill, just needed a shed to put it in).
The CNC mill is about 25yrs old but it has a 700mm*600mm*500mm machining area and a 24 tool auto changer. The Controller is capable of 6 axises (1 is used for the tool changer), so while it doesn't have a rotary table at this point in time, my brother has promised to give me one of his "castoffs" (along with a 40CFM compressor he has lying around his workshop gathering dust).

:wank: HELL YEAH
Lucky boy..........

Cheers,
Nick.

[amgis_obrut]

go na
as when your rod bearing fails and it will it will
be cheaper to bin the lot
mate a massive concern is no support for the side clearance
and will lose oil pressure bad, just a thought im not picking
shit
cheers stealth

the rods in my old turbo 250 were 3mm to narrow for the crank pin and low oil pressure was never an issue, oil pressure from the galleries to the outer bearing edge will still be enough to support the bearing regardless of side clearance, side clearance can be up to 60 times bigger than the bearing clearance on a factory engine

the size of the gallery on the above crank covers about a 3rd of the bearing width which is more than enough

i did have a problem with rod walk and scuffing the outer edges of the bearings but it was very minor and didnt lead to a bearing failure

Though i can see a problem with the crank pins that some what concerns me (may just be the pic) and thats the lack of radius in the cheek, that sharp step is a prime stress riser and could result in a cracked crank

[Superscan811]

Lucky boy..........

It's been a damn long time in getting it to this stage, but I still have to learn how to properly control the mill.

My brother has been working with CNC machines for over 20yrs now, and he seems to think that I'm in for a very rough time.

When the DNC side is setup (computer fed control of the CNC machine), it will take several months to perfect the post processor side (for want of a better phrase, language differences/interpretations) of the G and M codes (changing tools, start/stop coolant, spindal speeds, cutting threads, ID or OD cutting, tangent/radius calculations, setting tool and job offsets, etc...).

I kind of trust his guidance, especially when he has just spent twice as much on the cement foundations for his newest CNC Machining Center, as I spent on my CNC Mill.

At least I can call on him when I have issues.

It's going to be something different from my normal daily routine of PC/Server/Network support, but it will be fun..

Though i can see a problem with the crank pins that some what concerns me (may just be the pic) and thats the lack of radius on the outer edges, that sharp step is a prime stress riser and could result in a cracked crank

The inner edges have been radius'd (the major stress points) but the outer edge hasn't because it will help locate the rods better.
I may take the sharpness of the edge off but not by much.

the rods in my old turbo 250 were 3mm to narrow for the crank pin and low oil pressure was never an issue

Some nascar rods run 0.1" (2.5mm) side clearance but they center the rods on the Wrist pins. I have asked a few other engine builders about this and most (but not all) say it is fine.
The oil film (not the oil pressure) is what keeps the bearing and crank separate. The side clearance is typically twice that of the bearing clearance, so it's a bit like saying that when going from a 3" pipe into a 6" pipe, that the restriction of the 6" pipe is what matters...

The oil film is maintained more by the VOLUME OF OIL being pumped through the bearing, rather than than by the peak OIL PRESSURE.


Cheers.

[amgis_obrut]

i like to run .001 clearance for every inch of journal dia, typical rod side clearance can range from .015-.080 on a factory engine my old 250 was .112

I hear you with the pipe analogy

Oh and n/a all the way

[Rally_2.6LC]

A LC Hatchback with either a 4-point diff (or preferably an IRS) conversion, would be my ideal beast to drop one of the NA 2.6L engines into.

Is this an offer to build me an engine