2L-T Turbo dump pipe

[Syzygy]

I'm looking at putting a 2.5" exhaust on my bundera and have read about people replacing their dump pipes with 2.5 or 3" to improve performace.

the cast iron pipe on the back of my turbo looks to be bigger than the exhaust by quite a bit already. exhaust is 1.75" i think. Anyone know what the internal size of the cast section is? and is it worth replacing with something bigger?

was a bit tricky to get the camera in a decent spot...

 

[Entaran]

Being a turbo nut I suggest the following before making any decisions:

1) Remove the dump pipe (be careful of the bolts they will be rusted/otherwise stuck)

2) Measure the size of the turbine outlet on the actual TURBO itself

3) Match the ID of the new dump flange to this diametre

4) Make dump pipe to suit.

Only by following this process will you get maximum flow. The turbo will only flow as much as the turbine housing itself will allow through, there's no point putting a 2.5 inch pipe on a turbine housing that has a 3 inch outlet (such as all garret gt25+ series turbo's... 25/28/30/35/40 etc). There's also little point (but it can work) to put a 3 inch pipe on a 2 inch housing although this can help in exhaust gas flow.

The idea is to keep the pipe at the correct size and then to keep it hot enough to flow gas as fast as possible. This will extract every ounce of power available.

 

[denis]

I can get you some measurements if you want, I have all parts on the shelf
Tomorrow or monday.

 

[crushers]

Being a turbo nut I suggest the following before making any decisions:

1) Remove the dump pipe (be careful of the bolts they will be rusted/otherwise stuck)

2) Measure the size of the turbine outlet on the actual TURBO itself

3) Match the ID of the new dump flange to this diametre

4) Make dump pipe to suit.

Only by following this process will you get maximum flow. The turbo will only flow as much as the turbine housing itself will allow through, there's no point putting a 2.5 inch pipe on a turbine housing that has a 3 inch outlet (such as all garret gt25+ series turbo's... 25/28/30/35/40 etc). There's also little point (but it can work) to put a 3 inch pipe on a 2 inch housing although this can help in exhaust gas flow.

The idea is to keep the pipe at the correct size and then to keep it hot enough to flow gas as fast as possible. This will extract every ounce of power available.

i have to disagree with your statements, in theory you are correct but in practice having a larger exhaust, even if the dump itself is small, allows the exhaust gasses to be expelled quicker thus reducing the EGTs and allowing for much reduced back pressure.
i highly doubted the claims that a 3" dump would drop the EGTs till i gave it a try. i am not a big fan of the extra noise that came with this design but the EGTs did dropped further than with the 2 1/2" (deleated meaningless statement here)
it deffinately does make a difference. unless you really bag on your engine (like i have been known to do) then 2 1/2" works fine with a minimum of work to install, the 3" was a real pain to get installed.
there are pics of my exaust system on this forum somewhere...

 

[Entaran]

Indeed I said that you can increase your exhaust to 3 inch leaving a smaller dump but the gain is minimal as the restriction is there. As my main car is a 4g63t I have extensive experience in turbo vehicle modifications and when it comes to exhausts they all follow the same principles.

In relation to your EGT statements, the hotter the gases are the faster they flow. Increase the size of the exhaust and you make it easier for them to flow so assuming you have the same amount of gas it will flow slower. This is why people heat-wrap manifolds etc to keep the heat IN and therefore speed up the gas. This is extreme however. I heatshield manifolds to stop the heat from getting to the rest of the bay.

2 1/2 inch pipe will be sufficient for most, but the most gain will be had from a full 3 inch system which if you goto the correct place really isn't either hard or involved to install. I suggest you goto a "street car" performance shop and ask around about where to get a custom 3 inch system made.

Given the way the 4x4's are used, I suggest you get mild steel as it's half the price and your exhaust probably won't last 10 years anyway after bashing it to bits on rocks/etc. Stainless won't rust but it's twice the price and it'll probably get destroyed from track obstacles/etc.

 

[crushers]

interesting, correct me if i am wrong but are you saying my pyro readings at the elbow are incorrect?
the shop i use are very adapt at running custom larger exhaust on street racers to 4X4s, the problem is (and i am sure you have had a 3" on a 2LTE installed so you are speaking from experience here, right?) is the short distance down and out over the frame and down again and trying to get the radius to fit these curves but at the same time allowing for the tires to be able to turn full turn without rubbing.
my favorite is 2 1/2" aluminized exhaust with both a free flowing muffler and resonator. if the shop knows how to fab a proper system you do not have to worry about " bashing it to bits on rocks/etc" since the system will be tucked up out of the way (unless of course you don't know how to wheel in which case you can bash anything).
cheers

 

[denis]

i highly doubted the claims that a 3" dump would drop the EGTs till i gave it a try. i am not a big fan of the extra noise that came with this design but the EGTs did dropped further than with the 2 1/2" and the seat of the pants feel for quicker power response was there.

Wayne,

Where was the EGT probe installed, and where did the new exhaust start from ? How much did the EGTs drop ? (OK I'm going to search the archives and will probably get my answers there huh )

The seat of the pants performance evaluation is meaningless IMO, especially when the noise is much different.

Once a friend and I timed his LJ on a grade for testing the low-revs boost response, there was absolutely no difference that we could tell in terms of time and boost levels between a stock full exhaust, half exhaust and no pipe. The test was starting at 2000rpm 4th gear.

 

[denis]

nevermind I found it https://forum.ih8mud.com/showthread.php?t=71679

 

[crushers]

Wayne,
The seat of the pants performance evaluation is meaningless IMO, especially when the noise is much different.

Once a friend and I timed his LJ on a grade for testing the low-revs boost response, there was absolutely no difference that we could tell in terms of time and boost levels between a stock full exhaust, half exhaust and no pipe. The test was starting at 2000rpm 4th gear.

agreed, the seat of the pants is meaningless.
the turbo shop also backs your statement of performance with the different exhaust sizes. this mod is for the EGT reduction.

 

[crushers]

nevermind I found it https://forum.ih8mud.com/showthread.php?t=71679

thanks
;^)

 

[denis]

agreed, the seat of the pants is meaningless.
the turbo shop also backs your statement of performance with the different exhaust sizes. this mod is for the EGT reduction.

I think some sort of gain is certainly achieved at medium/high revs and high boost = high flow conditions.

What you read on the pyro is lower, but does this come from measuring a "lighter density" or whatever exhaust downstream gas flow, or is the combustion itself, and the flow upstream of the turbine actually colder ?

 

[crushers]

the pyro is installed about 2" away fro the exhaust turbines so the drop in temp would be expansions of gasses from the turbo. the back pressure on this side of the turbo has been reduced hence the gasses are free to flow thus reducing the heat trapped at the turbines.
i should install a pyro at the exhaust manifold on a stock system and on the enlarged system on this unit and compare the two. theroecticly if the exhaust gasses are not trapped on this side of the turbines then it should reduce the heat trapped on the manifold side as well...
hummm...
interesting, i think i see where you are going with this...
cheers

 

[Syzygy]

jeez you guys know how to post...

thanks for the info. I think ill keep the standard elbow and run a 2.5" mandrel system off that.

not expecting huge results, but i'll let you know how it goes after its done