Isn't it bad to mount it on a single runner?

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Yes, but a lot of people do it anyway. If you can't afford any other option then go for it

Is O2 housing a better place because all the gasses from all the runners go there?

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Yes it's better.

Wont it sound weird if mounted on #1 runner because gasses come out in pulses? (external dump)

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No idea on that one, I wouldn't really worry much about how it sounds though, it's going to be loud either way.

Haw hard is it to weld stainless to cast? Will it crack?

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If it's welded correctly it won't crack, but finding somebody who can do it right is going to be difficult and probably expensive. Preheat the manifold, use nickel rod, and don't let the manifold cool quickly. Those are the 3 most important things to remember when welding cast iron.

Idontknow said:

Wont it sound weird if mounted on #1 runner because gasses come out in pulses? (external dump)

Thanks.

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The answers Luke supplied I will concurr with.
In regards to this question, I will add that, I've heard external dumps off of #1 and they sound a little like cards in the spokes of a bicycle going downhill. That's the closest description I can think of.

GVR4592 said:

Idontknow said:

Is O2 housing a better place because all the gasses from all the runners go there?

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Yes it's better.

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I must disagree. I would argue that the O2 housing is not the ideal location for an external 'gate because it is located too close to the turbine housing, and because there is virtually no symmetry regarding the exhaust gases (the exhaust gases must basically take a 90 degree turn to enter through the extension pipe leading to the WG).

I didn't say it was the best place, I said it was better than the #1 runner. Almost every external wastegate option for our cars requires the exhaust gasses to make a 90 degree turn through an extension pipe before entering the wastegate, so that's not really relevant.

GVR4592 said:

I didn't say it was the best place, I said it was better than the #1 runner. Almost every external wastegate option for our cars requires the exhaust gasses to make a 90 degree turn through an extension pipe before entering the wastegate, so that's not really relevant.

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Assuming OEM-style EMs are being used (1G/2G/Evo III/FP), all the runners will be taking a 90 degree turn. So it's irrelevant to even mention a 90 degree turn because in all practical senarios the gases have to meet back up with either the O2 housing or the DP regardless. I'm just rying to offer good, practical alternatives for the excess gases getting to and leaving the external WG.

I have offered one of the better secenarios I can come up with here. Yes, in my altered photo there is a 90 degree turn in my proposition, but at least the extension pipe is in a great position to easily collect the gases from the collector (instead of having the extension pipe connecting to the collector at a 90 degree angle).

if you're gonna weld it, preheat it on the car, turn off the car incase you burn through, weld, and turn the car back on to not let it cool so quickly, then drill it through afterwards (off the car)

DSMunknown said:

Assuming OEM-style EMs are being used (1G/2G/Evo III/FP), all the runners will be taking a 90 degree turn. So it's irrelevant to even mention a 90 degree turn because in all practical senarios the gases have to meet back up with either the O2 housing or the DP regardless. I'm just rying to offer good, practical alternatives for the excess gases getting to and leaving the external WG.

I have offered one of the better secenarios I can come up with here. Yes, in my altered photo there is a 90 degree turn in my proposition, but at least the extension pipe is in a great position to easily collect the gases from the collector (instead of having the extension pipe connecting to the collector at a 90 degree angle).

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You were the one that brought up the 90 degree turn being a bad thing in the first place, are you arguing with yourself now?

GVR4592 said:

You were the one that brought up the 90 degree turn being a bad thing in the first place, are you arguing with yourself now?

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Certainly not. I'm arguing against the severity of certain 90 degree turns to the symmetry of other possible 90 degree turns. As I'm sure you are well aware of, abrupt 90 degree turns are less than ideal. A smooth transition into and out of a 90 degree angle is ideal.

Having an external 'gate plopped on top of the collector is not at the ideal angle the exhaust gases should be heading towards the WG (not to mention probable hood clearance issues). While the collector may be (and IHMO is in fact) the best place to extract excess gases, the angle of the extraction is important. As you can see in the link I provided, the altered photo shows the exhaust gases taking a 90 degree turn anyways. And as I said before, some things are unavoidable in most scenarios.

I'm just stressing the importance of the transitional phase between getting the exhaust gases out of the collector and back into the DP.

Ya Id have to disagree that o2 mounted wastegates are a better option. Think about it the stock wastegate hole size is 31mm. So if you have a 38mm wastegate, it has to go through a 31mm hole first it makes no sense. Its like having a 3 inch exhaust, but having it bottle down to 2 inches in the middle. But it does infact work for most people who use it and Im sure there's a way out of it by porting.

ILLiCliPSE said:

Ya Id have to disagree that o2 mounted wastegates are a better option. Think about it the stock wastegate hole size is 31mm. So if you have a 38mm wastegate, it has to go through a 31mm hole first it makes no sense. Its like having a 3 inch exhaust, but having it bottle down to 2 inches in the middle. But it does infact work for most people who use it and Im sure there's a way out of it by porting.

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But you're entirely forgetting how exhaust gasses act. Take a fluid dynamics class and then tell me how an extremely hot gas (~1500*) that is constantly expanding acts through a complicated shape such as a manifold and turbine housing. I'd assume that it is turbulant flow but solving for a reynolds number is all you.

In reality, you're not going to notice much difference either way. I really think the #1 runner mounted options aren't all that bad, as you really aren't trying to largely "vent" a large volume of gas so much as reduce the pressure built up in the manifold. If the pressure differential across the turbine is reduced, than you have effectively done your job. In reality, I doubt you're venting all that much gas. (last statement is complete speculation, however it is an educated speculation)

drivemusicnow said:

In reality, you're not going to notice much difference either way. I really think the #1 runner mounted options aren't all that bad, as you really aren't trying to largely "vent" a large volume of gas so much as reduce the pressure built up in the manifold. If the pressure differential across the turbine is reduced, than you have effectively done your job. In reality, I doubt you're venting all that much gas. (last statement is complete speculation, however it is an educated speculation)

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Amen! I see you did your Thermo homework back in college .

Pressure relief is pressure relief. Yes the flow is not as well when using a single runner external wastegate design. BUT! who cares? We're trying to lower pressure. If the pressure in runner 1 suddenly decreases, what happes to the gasses in the rest of the model? It rushes to the number one runner. At the very least the molecules ruhing to the turbine blades slow down. Who cares if all the molecules are from the otehr 3 runners. There's likely ZERO coming from the number 1 runner! Less work is done on the turbine wheel. Period.

Tapping at the number one runner of a currently owned exhaust manifold is comparativey cheap. It's using the laws of thermodynamics to save you money. No gas will fail to depressurise into intake runner 1, if there's a large unrestricted oriface present there. So what if runner 4 molecules don't evacuate at all. At the worst number 4 molecules would fill all the runners up. If number on molecules completely evacuate then there is 25% less pressure on the turbine blades P =nRT/V. "n" is the number of molecules. Which ever coefficient affects "n", the identical coefficient affects P.

P.S. Lowering the pressure in exhaust runner 1 causes the total gas volume to expand lowering exhaust gas temperature. This also lowers the work done on the turbine wheel by th total pressure of the model. P=nRT/V

Worked for me