Question As to what mod i buy first

[vxcp]

Mods done so far: Pacemaker Extractors, Xforce Twin 2.5inch exhaust and Twin High Flow Cats.

My question/s is which part would best suit my car to give it more kick, im on a little bit of a budget ($100-$900) and this is what i came up with:
i can get either of the following.

1. Cold Air Induction
2. Plenum and spacers (12mm or 25mm) whats the difference is it worth the extra 100 or what ever it is
or
3. Roller Rockers

Regarding the Roller Rockers if you think thats the best start for me to get more power my next question is, since the rockers will cost almost the same as the plenum and spacer kit with the CIA what is ur opinion on that also


And With the Plenum and spacer would it give the same power as if i just cleaned out my stock one of have in my VX commodore now.?

Any and all help would be appreciated tomorrow is pay day and im ready to order soon as it comes in also maybe dynos or comments from people that have had these mods and had gains from them could point me into the right direction.

Cheers
Andrew

[DevilDRake]

Roller rockers are the best bang buck, then a Diff upgrade.

But Roller rockers with exhaust/extractors + a CAI would be a great improvement. Leave the spacers til last if at all.

[vsv6dude]

Roller rockers are the best bang buck, then a Diff upgrade.

Leave the spacers til last if at all.

Why leave manifold spacers to last?
If at all ?

One of the cheapest mods with no affect or risk to the operation of vehicle, unlike rockers that can cause valve float, ticking noises, or spring fatigue unless its setup properly.

I have installed the 12mm manifold spacer on VS. I know it gives a slightly better kick off the line measured by the dynobutt.

From what I have read I think the spacer just shifts the torque curve earlier in the rev range. I am not sure it there is an overall increase in the total torque that can be measured on the dyno.

My mechanic is too cautious and advised me not to try the 25mm, although Mace recommends the 25mm manifold spacer as optimum one for fuel economy and torque gain across the rev range.

I have no experience with the plenum spacer.

[vxcp]

so vs dude u think i should go the manifold setup and is 12mm all good??

[Not_An_Abba_Fan]

Get rid of the twin 2 1/2", biggest mistake on a V6. Even twin 2 1/4" is too big unless you merge into a single 2 1/2" on the ecotec.

[immortality]

The general recommendation is as follows (if your chasing power, if economy is more important them start with the spacers/CAI),

High ratio rockers
25mm manifold spacer
12mm plenum spacer
Cold air intake
69mm Throttle body/tune
82 degree thermostat

NAAF is right about the exhaust. Twin anything is really to big for a simple bolt on modifications only setup.

Diff ratio upgrade will improve take off, shift kit will tighten up the auto trans although a lot of this can also be done through the tune.

For those a little more game, fit a decent converter

The plenum spacer primarily improves the air distribution inside the plenum.

Cheers

[vsv6dude]

so vs dude u think i should go the manifold setup and is 12mm all good??

I went for the 12mm manifold spacer.

My mechanic was concerned that the 25mm spacer would interfere with the bonnet. And as I used the metal gasket on the underside of spacer to form a seal my mechanic was concerned that he would not be able to crack the gasket to from a seal with 25mm spacer. With the longer bolts required for the 25mm spacer he thought that he would snap a bolt from over torquing and the metal gasket would not bite into the spacer to form the seal.

Installing the spacer this way reduces the amount of gasket goo required and looks more professional. To much messing around with extending the vacuum line etc. with 25mm. Also he convinced me that the 12mm is easier to hide under the engine cover.

I am glad I went for the 12mm as it was easier to fit and less messing with and looks stock under the engine cover.
Performance wise the 12mm offers 10% improvement compared to 13% for the 25mm spacer according Mace.

I installed the manifold spacer when I did my injectors to reduce installation costs. I am happy with the slight improvement.
I understand from reading the low end gains maybe even better with the VX as it has better computer tables to make adjustments than the VS model etc.

I am not sure if there is an overall increase in the total torque but it did feel slightly better off the mark.

Steve from Mace usually promotes the 25mm as the better investment.

I trust this helps.

[vxcp]

yeah mate thanks alot im going with the 25mm manifold spacer and the 12mm plenum spacer first off, then getting a cold air kit. =)

[vxcp]

And as for twin exhaust wouldnt it benifit because im getting the spacers which bring in more air therefore the twins will push it out faster resulting in more power and im getting a cold air kit real soon which will benifit further from the twins. Am i right?

[355SENATOR]

Nope! I tried it on my Vs Calais SS induction, Paceys etc... It was useless and made the car sound like a fart. Its to big and you lose nearly all back pressure, Its just to big for a small engine and with minor mods like that i wouldnt even bother. I now have a simple Lukey 2 1/2" catback system, custom Y piece off Pacemaker extractors. i had the extractors when the twin system was on running dual cats but seriously the car drives alot better now. Dont waste your time or money!

[immortality]

Nope! I tried it on my Vs Calais SS induction, Paceys etc... It was useless and made the car sound like a fart. Its to big and you lose nearly all back pressure, Its just to big for a small engine and with minor mods like that i wouldnt even bother. I now have a simple Lukey 2 1/2" catback system, custom Y piece off Pacemaker extractors. i had the extractors when the twin system was on running dual cats but seriously the car drives alot better now. Dont waste your time or money!

It's not that you loose back pressure (back pressure is a bad thing and you don't want it). When the exhaust system is to big what happens is the exhaust gasses cool (to much) and loose velocity (which if you think about it actually creates back pressure because the exhaust gasses have almost stalled so the next exhaust pulse needs to push it out), in really bad instances you can actually get reverse flow back into the cylinders commonly called reversion.

When it comes to exhaust systems for street use, always err on the small size as it will suit you better. With a smaller exhaust system it will suit low to medium revs better, so improved torque in the mid range at the expense of some peak power. for a racer where low rpm performance isn't a issue go for the bigger system, you will loose low rpm performance but gain more top end. With a properly spec'd exhaust system your trying to maintain good exhaust gas velocity. This is why header wrap and ceramic coating work as they maintain the heat in the gasses rather then radiating it out through the walls of the exhaust system.

Something else to consider is actually stepping the exhaust pipe down one step after the last muffler, if you think about this for a moment, as the exhaust gasses cool they take up less space, now because the cross section of the exhaust system hasn't changed that means that the gasses loose velocity........ so if you were to reduce the cross section of the exhaust system as the gasses cool you would maintain exhaust gas velocity and improve torque (some performance cars from yesteryear had this type of setup from the factory.........)

Cheers

[vxcp]

wholey shit that took effort to read all that lol so should i get a 2.5inch single with a high flow cat or 2. OR should i get a 2.25 inch exhaust with a cat or 2?? And it sucks cause ive had this xforce exhaust for about 4 months now sif.

[vxcp]

is there a big differnece in tourque against the two 12mm spacers and a 25mm spacer and 12 mm one if it worth the extra 100 dollars + or will it be barely noticeable performance wise what u guys think?

[immortality]

The factory system is 2.25 but has the standard (read nasty reverse flow) restrictive mufflers. Generally for a simple bolt on only modified car a simple single 2.5" system will suffice nicely. You can get a high flow cat if you wish although I don't know if it is cost effective when you consider $$$ spent for power gained.

Personally (being in NZ) I don't run a CAT at all, never had one to begin with.......

[Not_An_Abba_Fan]

It's not that you loose back pressure (back pressure is a bad thing and you don't want it). When the exhaust system is to big what happens is the exhaust gasses cool (to much) and loose velocity (which if you think about it actually creates back pressure because the exhaust gasses have almost stalled so the next exhaust pulse needs to push it out), in really bad instances you can actually get reverse flow back into the cylinders commonly called reversion.

When it comes to exhaust systems for street use, always err on the small size as it will suit you better. With a smaller exhaust system it will suit low to medium revs better, so improved torque in the mid range at the expense of some peak power. for a racer where low rpm performance isn't a issue go for the bigger system, you will loose low rpm performance but gain more top end. With a properly spec'd exhaust system your trying to maintain good exhaust gas velocity. This is why header wrap and ceramic coating work as they maintain the heat in the gasses rather then radiating it out through the walls of the exhaust system.

Something else to consider is actually stepping the exhaust pipe down one step after the last muffler, if you think about this for a moment, as the exhaust gasses cool they take up less space, now because the cross section of the exhaust system hasn't changed that means that the gasses loose velocity........ so if you were to reduce the cross section of the exhaust system as the gasses cool you would maintain exhaust gas velocity and improve torque (some performance cars from yesteryear had this type of setup from the factory.........)

Cheers

This sounds familiar.....

[vxcp]

well the thing is on my twin system i have 2 high flow cats on it so i dont have to spend xtra
and seeming i have a twin i should be able to just take one off and leave the other correct just need to wield the pipe from the extractors to the cat and im good to go?? what use think

[immortality]

This sounds familiar.....

LOL, i hate some of the myths that seem to spread around forums like wild fire and the back pressure myth is one of them

[immortality]

well the thing is on my twin system i have 2 high flow cats on it so i dont have to spend xtra
and seeming i have a twin i should be able to just take one off and leave the other correct just need to wield the pipe from the extractors to the cat and im good to go?? what use think

Well then I guess you just need to sort out a Y pipe and then use 1/2 of the twin system

[vxcp]

ok lol FOR SALE 2.5inch XFORCE EXHAUST 250$ haha

[Not_An_Abba_Fan]

Put a decimal point in after the 5 and you would be more realistic.....

[vxcp]

ummm whatt??

[Not_An_Abba_Fan]

ok lol FOR SALE 2.5inch XFORCE EXHAUST $25.0 haha

That......

[vxcp]

hahah up ya ok ill do ya a deal $25 dollars plus $225 freight lets go

[DevilDRake]

Why leave manifold spacers to last?
If at all ?

One of the cheapest mods with no affect or risk to the operation of vehicle, unlike rockers that can cause valve float, ticking noises, or spring fatigue unless its setup properly.

I have installed the 12mm manifold spacer on VS. I know it gives a slightly better kick off the line measured by the dynobutt.

From what I have read I think the spacer just shifts the torque curve earlier in the rev range. I am not sure it there is an overall increase in the total torque that can be measured on the dyno.

My mechanic is too cautious and advised me not to try the 25mm, although Mace recommends the 25mm manifold spacer as optimum one for fuel economy and torque gain across the rev range.

I have no experience with the plenum spacer.

The spacers are good but show their true results last after everything else. I got mine first and didn't tell too much difference, but it's proven they increase 10% torque as due to the extra plenum volume/space.

[vxcp]

yeah im going to get them and a CAI =p