Resolved Does this exhaust pipe affect the turbo engine's performance? FWD 1G

[DrGaribay]

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[curt-s]

This is my take on it:

Basically the question is, does exhaust back pressure affect turbo performance (not engine, as scavenging is not taken into consideration here)? The short answer is yes. The more resistant the gas is to flowing, the less the turbo has the ability to spin faster (ie. Spool). The turbine wheel works on exhaust gas being able to flow across it from high to low pressure areas as freely as possible.

In that example the Y pipe has more total cross-sectional area after it divides than the cross sectional area before the division. It would be equivalent to a feed pipe much larger. This is assuming a perfect 50/50 gas division, which is unlikely, but statistically close enough. any resistance to flow in either side will effectively divert gas to the other side as it is the path of least resistance.
However the two 180 and one 90 bends are being introduced in a cold section of the pipe which will slow and cool the gas much more than a straight section. That slowly of the gas creates a restriction that works against the benefits of a greater cross sectional area.

For something this complicated, you could potentially do the dynamics math involved. You could also just try it on a dyno and see.

 

[DrGaribay]

This is my take on it:

Basically the question is, does exhaust back pressure affect turbo performance (not engine, as scavenging is not taken into consideration here)? The short answer is yes. The more resistant the gas is to flowing, the less the turbo has the ability to spin faster (ie. Spool). The turbine wheel works on exhaust gas being able to flow across it from high to low pressure areas as freely as possible.

In that example the Y pipe has more total cross-sectional area after it divides than the cross sectional area before the division. It would be equivalent to a feed pipe much larger. This is assuming a perfect 50/50 gas division, which is unlikely, but statistically close enough. any resistance to flow in either side will effectively divert gas to the other side as it is the path of least resistance.
However the two 180 and one 90 bends are being introduced in a cold section of the pipe which will slow and cool the gas much more than a straight section. That slowly of the gas creates a restriction that works against the benefits of a greater cross sectional area.

For something this complicated, you could potentially do the dynamics math involved. You could also just try it on a dyno and see.

Hey,

Just wanted to update you on the exhaust situation. I ended up removing the Y-pipe setup because it actually caused some issues. The increased back pressure from the bends and restrictions ended up damaging my turbo. As a result, I also ended up breaking an original piston.

Now, I'm in the process of forging and rebuilding the engine. This time, I'm going with a straight exhaust line to ensure better flow and avoid the same problems. Lesson learned the hard way, but at least it's getting sorted out now.

Thanks for the insights!

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[pauleyman]

Hey,

Just wanted to update you on the exhaust situation. I ended up removing the Y-pipe setup because it actually caused some issues. The increased back pressure from the bends and restrictions ended up damaging my turbo. As a result, I also ended up breaking an original piston.

Now, I'm in the process of forging and rebuilding the engine. This time, I'm going with a straight exhaust line to ensure better flow and avoid the same problems. Lesson learned the hard way, but at least it's getting sorted out now.

Thanks for the insights!

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You blew up and did all this since Saturday? I kinda doubt that exhaust caused your engine failure. I see a 16g in your profile on an (formerly) automatic car. Fuel mods? None are listed. 1g autos have even smaller injectors than a manual. If the the turbo is all you have and especially if you turned boost up, that would be your cause of failure. Please elaborate on mods.

 

[Mr PopUps]

Hey,

Just wanted to update you on the exhaust situation. I ended up removing the Y-pipe setup because it actually caused some issues. The increased back pressure from the bends and restrictions ended up damaging my turbo. As a result, I also ended up breaking an original piston.

Now, I'm in the process of forging and rebuilding the engine. This time, I'm going with a straight exhaust line to ensure better flow and avoid the same problems. Lesson learned the hard way, but at least it's getting sorted out now.

Thanks for the insights!

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That exhaust is less restrictive than stock.... no way it did anything to your turbo.

 

[DrGaribay]

You blew up and did all this since Saturday? I kinda doubt that exhaust caused your engine failure. I see a 16g in your profile on an (formerly) automatic car. Fuel mods? None are listed. 1g autos have even smaller injectors than a manual. If the the turbo is all you have and especially if you turned boost up, that would be your cause of failure. Please elaborate on mods.

I rebuilt the engine after buying the car, which had already been converted to a manual transmission but had issues with the third cylinder. When I opened the engine, I found the head had already been milled twice. Since I couldn’t find a replacement locally, I had a machinist adapt it. After assembling, I broke in the car for 500 kilometers and installed the exhaust you see in the photo. Later, I noticed wear on the lifters in the head, and one day it started smoking and leaking oil from the valve cover and the turbo. When I opened the engine again, I found a cracked piston. I debated scrapping the car but decided to forge it and give it another shot. I sourced a head with standard measurements, standard forged pistons, forged rods, and rod bearings. My question is whether the exhaust caused the failure or if it was the adapted head. In any case, I’ve already removed the exhaust and am now waiting for the engine to be rebuilt with 650cc FIC injectors, a new 16g turbo, ARP studs, a full set of Cometic gaskets, and a fuel pressure regulator, aiming for a 250hp street build.

 

[pauleyman]

I rebuilt the engine after buying the car, which had already been converted to a manual transmission but had issues with the third cylinder. When I opened the engine, I found the head had already been milled twice. Since I couldn’t find a replacement locally, I had a machinist adapt it. After assembling, I broke in the car for 500 kilometers and installed the exhaust you see in the photo. Later, I noticed wear on the lifters in the head, and one day it started smoking and leaking oil from the valve cover and the turbo. When I opened the engine again, I found a cracked piston. I debated scrapping the car but decided to forge it and give it another shot. I sourced a head with standard measurements, standard forged pistons, forged rods, and rod bearings. My question is whether the exhaust caused the failure or if it was the adapted head. In any case, I’ve already removed the exhaust and am now waiting for the engine to be rebuilt with 650cc FIC injectors, a new 16g turbo, ARP studs, a full set of Cometic gaskets, and a fuel pressure regulator, aiming for a 250hp street build.

You cannot just add injectors. What are you using for control? What injectors are in there now?

 

[Mr PopUps]

I rebuilt the engine after buying the car, which had already been converted to a manual transmission but had issues with the third cylinder. When I opened the engine, I found the head had already been milled twice. Since I couldn’t find a replacement locally, I had a machinist adapt it. After assembling, I broke in the car for 500 kilometers and installed the exhaust you see in the photo. Later, I noticed wear on the lifters in the head, and one day it started smoking and leaking oil from the valve cover and the turbo. When I opened the engine again, I found a cracked piston. I debated scrapping the car but decided to forge it and give it another shot. I sourced a head with standard measurements, standard forged pistons, forged rods, and rod bearings. My question is whether the exhaust caused the failure or if it was the adapted head. In any case, I’ve already removed the exhaust and am now waiting for the engine to be rebuilt with 650cc FIC injectors, a new 16g turbo, ARP studs, a full set of Cometic gaskets, and a fuel pressure regulator, aiming for a 250hp street build.

650cc's? Why? You can do 350hp on 450s easily...