VS-VY Stock L67 PSI

[scvs6]

Hey guys,

Just wondering if anyone knows how much PSI a stock L67 Supercharged V6 runs? I just installed a boost gauge in my VS (with the reconditioned VY L67), I have only road tested it once since I have installed the gauge, and it was running around 4-5 PSI, does that sound about right?

After a while I am thinking of buying the Yella Terra Stealth intercooler kit for the L67 and running between 12-14 PSI, but even the 10 PSI kit would probably be enough.

Thanks.

[pjdm1980]

They were 6PSI from the factory.

[Haydz]

hey man i can recommend a2a instead of w2a check out l67torque.com for more info on the performance side of this engine. but yes that sounds about right for boost pressure. under wot in the right conditions should see 5-6 psi on the gauge

[SweetWagon]

Do you have the standard exhaust still on it, or any other modifications?

if its all still factory then as stated, you will see ~6psi in the right conditions.

commonly though, improvements to head flow, cam and exhaust etc will see a reduction in manifold pressure.

[scvs6]

Ok, when I take it out on the weekend again, ill see what it reads, I only drove up the road and back which is about 2 kms total.

hey man i can recommend a2a instead of w2a check out l67torque.com for more info on the performance side of this engine. but yes that sounds about right for boost pressure. under wot in the right conditions should see 5-6 psi on the gauge

Thanks mate, ill check that out. I'm not too sure on what intercooler set up to use so its good to find out what the best one would be. I'll go take a look at l67torque.com and see what info I can get from there.

[scvs6]

Do you have the standard exhaust still on it, or any other modifications?

if its all still factory then as stated, you will see ~6psi in the right conditions.

commonly though, improvements to head flow, cam and exhaust etc will see a reduction in manifold pressure.

I still have the same exhaust system as I have on the N/A V6, Pacemaker extractors, standard car, 2.5 inch redback exhaust and a redback sports muffler in the middle. Should I change the cat (or any other part of the exhaust) now because its supercharged? It also has the factory L67 cold air intake, K&N pannel filter, etc.

I actually have a question about the diff though, if I was to get an LSD or get mine rebuilt as an LSD, what ratio/gears should I get? 3:08.1, or because it's LSD is it different to the standard diff?

[SweetWagon]

I still have the same exhaust system as I have on the N/A V6, Pacemaker extractors, standard car, 2.5 inch redback exhaust and a redback sports muffler in the middle. Should I change the cat (or any other part of the exhaust) now because its supercharged? It also has the factory L67 cold air intake, K&N pannel filter, etc.

I actually have a question about the diff though, if I was to get an LSD or get mine rebuilt as an LSD, what ratio/gears should I get? 3:08.1, or because it's LSD is it different to the standard diff?

The extractors and 2.5" system could easily account for the lower manifold pres. as gases are being expelled easier. with upgrading it, depends how wild you plan on going with the motor - if your cranking up the boost, intercooling, cam etc, then you will want it to breath much better.

Most ditch the single cat and go twin cats. From there you could keep it twin 2 1/4" the whole way or merge into single 3"

3.08 really isnt a bad ratio, with the extra torque they pull really well with the stock ratio and sit nice on the motorway, but if you are set on replacing the diff gears and have an auto, i would skip 3.45 and go to 3.7

[pjdm1980]

I had 3.9's in my Statesman and it launched Like a rocket but sat at 2200RPM@100Kph.

[wamboin23]

I've just gone twin 2.5" exhaust, merged to single 3" before the diff. Nice and quiet at cruise (even at 2600rpm with the 3.9's), but sounds good under throttle.

Just for comparison, mine with 87mm pulley ("10psi") sits at about 8, but i haven't had a boost gauge on for ages, so would be lower now I'd assume.

[GenFree]

Delete the boost solenoid,the mod is written up on l67 torque

This will stop any electronical interearance with boost if its not operationg correctly.

[scvs6]

I do a lot of highway driving, at the moment, driving from Ballarat to Melbourne, sits on 2000RPM at 110km/h. So I guess I should stick with a 3:08.1 LSD. There is one on eBay at the moment for $655 fully reconditioned, but I'll see how much it would cost to get mine rebuilt.

[GenFree]

A lsd out of a manual(3.46)is a good compramise

[SweetWagon]

I've just gone twin 2.5" exhaust, merged to single 3" before the diff. Nice and quiet at cruise (even at 2600rpm with the 3.9's), but sounds good under throttle.

Just for comparison, mine with 87mm pulley ("10psi") sits at about 8, but i haven't had a boost gauge on for ages, so would be lower now I'd assume.

Similar to me - I have twin 2 1/4", merged into single 3" before diff, but have to remember being auto his will drone more than the manuals

Out of curiosity how is 1st gear with the 3.9 gears?

Delete the boost solenoid,the mod is written up on l67 torque

This will stop any electronical interearance with boost if its not operationg correctly.

its nothing to do with electronic interference, the problem is the solenoid tends to leak, but if his getting that much pressure in the manifold it would be working correctly (if it hasn't been bypassed already)

[SweetWagon]

A lsd out of a manual(3.46)is a good compramise

a manual what? theyre all 3.08.

3.45 is a good compromise, but IMO if your replacing the gears they're not worthwhile especially in a auto you will barely notice improvement

3.45 is only a 12% gear reduction
3.7 is a 20% gear reduction
3.9 is a 26% gear reduction

but as the OP mentioned doing highway driving, you will be best leaving 3.08 and just getting the LSD centre, that way speedo and shiftpoints wont be affected either.

[wamboin23]

Similar to me - I have twin 2 1/4", merged into single 3" before diff, but have to remember being auto his will drone more than the manuals

Out of curiosity how is 1st gear with the 3.9 gears?

quick. it is usable, but you can start off in 2nd with no real problems.

[DevilDRake]

a manual what? theyre all 3.08.

3.45 is a good compromise, but IMO if your replacing the gears they're not worthwhile especially in a auto you will barely notice improvement

3.45 is only a 12% gear reduction
3.7 is a 20% gear reduction
3.9 is a 26% gear reduction

but as the OP mentioned doing highway driving, you will be best leaving 3.08 and just getting the LSD centre, that way speedo and shiftpoints wont be affected either.

VY manual utes most have 3.45's


I got a full reconditioned one, with lsd gears + 3.7's genuine gears for $800. Tight and works great.. Rev at like 2200RPM though, but if you got 3.45's you could get 1900rpm possibly.. which isn't too bad. I mean normally is like 1400 or something?

[pjdm1980]

Normal S/C six sit on about 1750RPM@100KPH

[scvs6]

Similar to me - I have twin 2 1/4", merged into single 3" before diff, but have to remember being auto his will drone more than the manuals

Out of curiosity how is 1st gear with the 3.9 gears?



its nothing to do with electronic interference, the problem is the solenoid tends to leak, but if his getting that much pressure in the manifold it would be working correctly (if it hasn't been bypassed already)

The boost solenoid is all connected up and seems to be working fine, there was a plug for it on the wiring loom so I thought that I may as well use it.

I am taking the VS to the exhaust shop to get 2 high flow cats and a new Y-piece made up, just that is going to cost $550. So would you recommend 3 inch exhaust before the diff, twin system, or keep the 2.5 inch single system with the one sports muffler?

[wamboin23]

i got mine done as twin 2.5", into 3" before the diff, because later down the track it's not a big job to flange it before the merge and have a full twin system.

but i'd say single 2.5" will be too small once the mods begin.

[wana s' charge stock vt]

twin sounds better than 3' imo....

twin 2.25' works well and is pretty popular for mild motors... twin 2.5inch gets pretty loud n drony..


and from my reading 3.46 diff gears seems to be the most practical and popular...


ya may aswell delete the bypass 'solenoid' too. its free and they're pretty common to play up n make ya loose boost and do random shiit.... .

[GenFree]

a manual what? theyre all 3.08.

3.45 is a good compromise, but IMO if your replacing the gears they're not worthwhile especially in a auto you will barely notice improvement

3.45 is only a 12% gear reduction
3.7 is a 20% gear reduction
3.9 is a 26% gear reduction

but as the OP mentioned doing highway driving, you will be best leaving 3.08 and just getting the LSD centre, that way speedo and shiftpoints wont be affected either.

I have these gears in mine and they are the best for a low powered L67n my experience,I have had 3.07 and 3.89 as well.The torque from the L67 does not require low gears as you know and coupled with the short 1st gear in the trans its still launches hard.Most people run mags and this alters ratios as well

3.46 lsd diffs are in most manual ls motors.This ratio will have similar revs as a 4 speed auto VL Commodore at any speed for comparrison.

OP,3.46 is the best compromise imo.No need to change gears in your housing just get a complete good 2nd hand centre assembled and bolt it in.3-4 hour job