53 replies to this topic

[Kieran B]

LINK



i was reading the above link.. and it got me thinking..
If im running standard pistons with eagle rods and have a small pulley, do i have anything to worry about?
So the questions is.. is any one else running this set up, and do i need a slightly thicker head gasket to lower the compression

cheers!

[NickB787]

not certain I think most now use that setup. I some put the 8.9 pistons in will see what bhp I come out with but reading the link wonder if I can go up a bit?

Edited by NickB777, 07 March 2011 - 09:51 AM.

[techieboy]

When you say smaller pulley, what size do you mean? If you're upping the boost, then you want to be lowering the compression ratio for safety.

[Exmantaa]

Standard size LSJ pulley (Stage2) works fine with the standard SE 10:1 compression, but more boost with smaller pulleys (3.0" - 2.9",plus higher inlet temps!!) may induce knock. The 2.2SE has little spark advance, so retarding to counter knock results in loosing power through the exhaust. (Read that statement from Courtenay somewhere.)
Depends on how good you can control the ecu, but lowering compression a tad on higher boost builds will help fighting knock & ign. retard.

Copied from that thread (data from Atom X):

Z22yh gasket 0.37mm
Z22se gasket 0.49mm
Z20net gasket 0.98mm (=Saab B207)

1mm roughly equates to 1.00 CR on 86mm bore with 53cc of combustion chamber

Therefore If one were to replace standard SE gasket with NET/B207 gasket
then CR would drop ~0.5 CR

original (SE) CR = 10.00:1
replacement (NET) CR = 9.50:1 approx

Edited by Exmantaa, 07 March 2011 - 10:42 AM.

[siztenboots]

what you want is bigger pulley on SC nose, less rpms on the charger , flatter ramp rate vs rpms

[Bargi]

You should give me the smaller pulley cause I've got the low-compression pistons

[techieboy]

what you want is bigger pulley on SC nose, less rpms on the charger , flatter ramp rate vs rpms

That's called Stage1 and kind of isn't worth bothering with.

[siztenboots]

i would stick a vernier on the inlet cam and retard it to dial out some of the dynamic compression to suit your limits of conrod torque, fueling , but keep the rpm range just how bad a problem are the rods

[Winstar]

i would stick a vernier on the inlet cam and retard it to dial out some of the dynamic compression to suit your limits of conrod torque, fueling , but keep the rpm range

just how bad a problem are the rods

the inital destuctive testing found they break at 250 bhp achieved with NOS, although quoting power is bollox as it's torque that breaks rods.

The SC cars are putting about 260 bhp at the fly so with the parasitic loss they'll be seeing around 290 bhp.

But to an extent steve is right if you up the compression and reduce the boost and loss through the CC then you could ge more useful po wer high up the rev rangewithout the rods failing as you only be producing the same or less torque. on the other hand the eagal rods aren't that expensive.

[The Batman]

From experience 270 at the fly will destroy the rods

[Kieran B]

are the rods the only thing i should be worrying about then.. (i have these already so im safe in that department )

Edited by Kieran B, 07 March 2011 - 01:13 PM.

[The Batman]

Then it moves the weak point to the pistons

[Kieran B]

Then it moves the weak point to the pistons

so in your opinion its safer to just use the larger pulley? - pistons are too expensive for me at the moment

[Sutol]

Hi Keiran, I know you're keen to get on with your SC build project but if you do intend to get the rods/pistons done at a later stage i think i would save up and get it all done at the same time. I think it will be cheaper in the long run - I know it's not always possible though. Chris

[southpaw]

What size exhaust do you have?

[NickB787]

310 bhp is the piston limit

[siztenboots]

310 bhp is the piston limit

at what rpm though, 310bhp at 4000rpm is 407 ft-lbf

whereas , 310bhp at 7500rpm is just 217 ft-lbf

[Kieran B]

ive got the rods already. i was looking for 255/260ish BHP. obviously if CMS can map it higher then that it would be great. i have the 2.5 full tullett, so it wont go past 270 BHP anyway, i dont think i will get anywhere near that though... so im guessing i should be safe? but what i wasnt sure on is, do i have to do anything if i wanted to run the smaller pulley? (i think its a 2.9) or should i just swap it out for the standard one to be safe?

[techieboy]

but what i wasnt sure on is, do i have to do anything if i wanted to run the smaller pulley? (i think its a 2.9) or should i just swap it out for the standard one to be safe?

So the howl mine made on Saturday with the 2.9" pulley didn't put you off then?

[Kieran B]

but what i wasnt sure on is, do i have to do anything if i wanted to run the smaller pulley? (i think its a 2.9) or should i just swap it out for the standard one to be safe?

So the howl mine made on Saturday with the 2.9" pulley didn't put you off then?

It was sexual matt