IC piping = 2'' hot side with 3'' cold side, good or bad?

[pikul21gsx]

Hey guys, i have a 1990 GSX with a FMIC and 3'' piping with short route on the hot side, mi question its this, i went with the 3'' because i was planning on running a holset and since price range from 2.5 to 3'' kits its the same i said why not.

Now heres were i need your input, ive just bought a Nissan 350Z and im not gonna be able to upgrade the turbo in my dsm probably in a year or maybe more, i currently have a 14B and lag its horrible, i was thinking of changing my hotside to 2'' piping, and leave the cold with 3''.

You think this is ok? would affect my performance if i later install lets say a 16G?

 

[Bud92gsx]

If you have a 14b and the lag is bad, somethings wrong.My 14b starts spooling at around 1800 rpms,and at 2300 im at 14 psi.Check for pre turbine exhaust leaks,manifold, turbine housing.


A 16g is just gonna dd a few hundred more rpms of lag.

 

[pikul21gsx]

ive fixed a leak i had at the throttle body but it didnt really help, i think its because of the piping, going from 2 to 3'' seems to be to much :/ i do have a 2'' to 3'' coupler to make the transition better.

 

[delta448]

The piping isn't going to affect spool that much, maybe a couple hundred rpm at most. Boost and exhaust leaks are much more likely, but the turbine housing is probably cracked internally. Almost all of the stock 6cm housings have some cracks, the severity of depends on the usage the turbo has seen. At what rpm are you seeing 10+ psi?

 

[pikul21gsx]

Really? I thought it would be more because its 1 inch bigger then the jpipe, i hit 12 psi by 3500 rpm, i have a almost new 7cm exhaust housing on, i cant seen to find any leaks

 

[Bud92gsx]

Really? I thought it would be more because its 1 inch bigger then the jpipe, i hit 12 psi by 3500 rpm, i have a almost new 7cm exhaust housing on, i cant seen to find any leaks

Something is wrong, im on the same turbine housing and I told you in my first post what boost im seeing with the same turbo,turbine housing combo.My manifold and turbine housing are both ported as well.

But you have a pre turbo leak if your seeing 12 psi above 35k rpms.

 

[pikul21gsx]

I dont have leaks on my exhaust manifold or intake, it didnt felt like this with the stock side mount, im gonna take to a shop so they can do a compresion test, i have a bad feeling about this jajaja

 

[99ECLIPSEGSXDSM]

Have you checked for shaft play or looked at the compressor wheel to see if the blades are messed up? A friend had a 14b that sucked something up and he couldn't spool fast because the blades were shot

 

[pikul21gsx]

Turbo seems ok, blades are fine and not hitting with the housing, no apparent oil leeks, theres little to none smoke in the exhaust when i rev the engine, i have a bad feeling bro.

 

[pikul21gsx]

Ok so took it to a shop so they can do a compression test, bad results 105 115 115 115, that and the size of the piping its causing what doesnt really is lag, with the side mount and small paping wasnt really notorious and since i didnt took it to the race track i couldnt notice if it was fast or not jajaja i didnt use it that mucho since ive been trying to restore it.

Anyways you think smaller piping could help? As i said im not planing on spending a lot of money anytime soon

 

[tkelly27]

Area of a circle = 3.14 * (diameter/2)^2

2in circle
3.14 * (2in/2)^2 = 3.14in^2

3in
3.14 * (3in/2)^2 = 7.06in^2


Assume a pipe 24" (two feet) long from your intercooler to your throttle body.

Volume of a cylinder = base area * length

2in pipe
24in * 3.14in^2 = 75in^3

3in pipe
24in * 7.06in^2 = 170in^3


Convert cubic inches to cubic feet

75in^3 * (1ft^3 / (12in * 12in * 12in) = .043ft^3

170in^3 * (1ft^3 / (12in * 12in * 12in) = .098ft^3

Assume turbo moving ~ 200cf/min it should take

.055cf * 1min/200cf = 2.76 * 10^-4 min or .016 seconds to fill up.

It is more complicated than that, but it really doesn't make that big of a difference to have a 3" pipe. It certainly doesn't explain it spooling up nearly 1000rpm slower.