Yep, yet more queries from me here!

 

In the very near future, I'll be upgrading my entire exhaust system - it's currently stock to the rear axle, with Powerflow backboxes. As I'll be upgrading the turbos a little in the future, it makes sense to have a suitable system behind them in readiness.

 

So I'm currently debating 3" downpipes, 3" to 2.5" testpipes and the rest of the system at 2.5" - is the 3" bore likely to be overkill on what will ultimately be a fairly mildly-tuned car?

 

I've done A LOT of reading up this morning on the available 3" downpipes and the choice seems to be limited to a pair from Speciality Z or a pair from AMS. I've come across a lot of contention regarding the fitment and quality of the AMS stuff too... indeed, Jimmer advised me against using their downpipes and testpipes last night.

 

My original plan was to have the AMS downpipes and then have the rest of the system made bespoke, including the tapered testpipes. Is the AMS quality that bad that I should avoid that idea? Or would it just make more sense to use SZ pipes instead of the AMS ones?

 

And if the 3" half of the system is indeed overkill, should I be looking at perhaps the Z1 2.5" downpipes and testpipes matched to a bespoke system?

 

As I said in my turbos thread, I'm an absolute n00b when it comes to turbocharged cars so I'm needing solid advice. Hence all the questions!

 

:thumbup1:

Here you go:

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2374912/SZ-3-expansion-vs-AMSAlloy-Toyz-3-Split-Down-Pipe.html

Here you go:

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2374912/SZ-3-expansion-vs-AMSAlloy-Toyz-3-Split-Down-Pipe.html

 

Yep, I've read that. Thanks for posting it though :thumbup1:

 

Ok, new question (sort of): is any difference between 3" downpipes and 2.5" downpipes going to be negligible, or would it actually be quite noticable?

 

Speciality Z 3" pipes are going to cost $786.40 plus import duty. Which is a lot of money! Z1's 2.5" downpipes are considerably less expensive, so might they be the sensible route to take instead? Bear in mind that the turbos will end up being upgraded, albeit slightly, in the future as well...

 

:)

Ok, new question (sort of): is any difference between 3" downpipes and 2.5" downpipes going to be negligible, or would it actually be quite noticeable?

About 1/2 an inch??

My wife would notice the difference...... so she just told me...... lol

I think you need to decide what level of power increase you are aiming for. What have you in mind?

 

The Z1 2.5" design is 1st gen and was superseded by the SZ/Labree 2.5" design (see CZP). But again

depending on you goals could still work for you.

I think you need to decide what level of power increase you are aiming for. What have you in mind?

 

The Z1 2.5" design is 1st gen and was superseded by the SZ/Labree 2.5" design (see CZP). But again

depending on you goals could still work for you.

 

I'd be happy with mid to high 400s in the end, Andrew. I know that, from a reliability standpoint, I'll be needing new injectors to compliment things like the Selin kit, the bigger SMICs, the new exhaust, etc but this will have to be a long build (as it were).

 

I don't need to go crazy with the power levels because I still want the car to be pleasurable to drive and, in all honesty, she's pretty rapid at the moment anyway. But the snails and the exhaust (at least the front half) are all 20-odd years old now so are due for replacement.

 

I'm just trying to find the best set-up that going to yield the best results and also allow me to use the relevant components well.

I use this site for a lot of information, I think I've read in here somewhere that 3" is only really necessary for larger performance gains. http://s95014253.onlinehome.us/63104/111250.html

See, that page is advocating using 3" pipework for the first half of the system at least. This is where it becomes confusing...! :lol:

As you asked about SZ 3" downpipes this is Greg@SZ detailed post on them.

 

http://www.twinturbo.net/net/viewmsg.aspx?forum=general&msg_id=2033426

 

They do make a difference even with 2.5" for the rest of the system. You can also see follow

up posts from folks using some/all of the 3" parts in their cars.

Im sure I read somewhere recently that 3" is only really necessary for larger numbers and that the cost of going to 3" is very expensive for the actual gains you get. I thought it was on the link I posted, but obviously I was wrong :(

Im sure I read somewhere recently that 3" is only really necessary for larger numbers and that the cost of going to 3" is very expensive for the actual gains you get. I thought it was on the link I posted, but obviously I was wrong :(

 

As I read it, he seemed to be saying the gains for a 3" catback system were minimal.

I don't know what I'm talking about ;)

I think it will positively change the rev band that power is available to you. The 3" DP and test pipes, paired up with a 2.5" intake kit (and the Selin which you already have or intend to buy?) the mid range power is significantly improved. Not necessarily big hp gains at the top end but very positive drivability gains. In my experience, the vg tends to lack mid range torque whilst being easier to open top end hp.

 

I regret not investing in the 3" DP and test pipes and it's on my list to upgrade, I wish I did it properly the first time so that I don't have to do it again! That said, to fully unlock the benefits, ideally as I said above you'll need the 2.5" intake kit (which could be added at a later date), but really you need to swap out those restrictive stock manifolds with some MSPs so your price just doubled again!

Joe is right on the money.

 

Turbos love to breath, the better they breath the more power they will make and the less lag you will have.

Weather you upgrade you turbos or stick with the stock ones, having a bigger exhaust and a better intake will net you gains across the board. The VG, sadly, is not the the best engine at moving air quickly, therefore the easier you make it for the whole system to breath and exhale the more power it will make and the smoother it will be.

What I am saying is, Yes the extra expense of the 3" down pipes is well worth it in the long run, you can stick with a 2.5" cat back exhaust, not optimal, but it is a heck of a lot better flowing that the factory exhaust system (you can always upgrade to a 3" if funds are tight at the moment). It is easier to change/upgrade the exhaust than it is to change the downpipes.

paired up with a 2.5" intake kit (and the Selin which you already have or intend to buy?)

 

Plus the 2.5" SMICs...

Plus the 2.5" SMICs...

 

This ☝️ and if you already have uprated coolers, it may be cheaper to have the outlets removed and 2.5" outlets welded in place.

About 1/2 an inch??

My wife would notice the difference...... so she just told me...... lol

But when you only have half inch in the first place, of course she would notice :lol:

So the general concensus seems to be that any improvements I can make to the engine's breathing - either inhaling or exhaling - can only be a good thing. :)

 

Time to assess the pennies, I think....