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Single Turbo Wastegate Recirculation? [Archive]

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: Single Turbo Wastegate Recirculation?


Chris Peterson

07-12-2007, 12:57 PM

I have a Boost Logic T67DBB kit on which the exhaust manifold has a flange for an HKS wastegate. I am looking at cutting that off, replacing it with a TiAL WG (V-band!), and recirculating it back into the BL 3" downpipe instead of the current open dump tube setup. Can anyone explain the benefits/drawbacks to each scenario (performance-wise, driveability, etc)? From previous threads I have gathered that you hear the turbo more with a recirculated setup, but the re-entrance into the DP has to be done correctly or it could negatively affect the exhaust gas exit flow. Also, I recall seeing some great pics of a 2JZ on an engine stand with a recirculated kit (looked to be an SP unit, however the picture links in their turbo kits section do not work for me (?action=product&vehicle_id=1&category_id=13)), does anyone have any similar pictures that show this? Any information would be appreciated, thanks in advance.
Chris

I know I saw a discussion at least tangential to this recently, but no search, so sorry if this has been beaten to death somewhere else.

OneJoeZee

07-12-2007, 01:05 PM

I don't have any pros or cons performance wise... but on my setup I have twin Blitz wastegates that are rerouted back into their respective downpipes before they come together at a "Y" before the cat. I prefer it much better this way. I imagine if they were both vented to atmosphere, the sound would be more than I could stand. I've ridden in a few cars with open wastegates and the noise got really annoying to me after about 10 minutes. So that's my review from a subjective view.

I'd be interested in hearing about any performance difference as well although I doubt there is a significant difference. If there is, I'd love to know about it but I don't know that I would change my setup still. The excessive noise would make me not want to drive the car at all. It doesn't bother some people but it does bother me quite a bit...

HIGHPSI

07-12-2007, 04:40 PM

i dont think it really makes or brakes a car performance wise to have the dump tube recirculated back into the exhaust.. I think its more for sound that its re-ruited rather then atmospheric dumped. I personally like its dump atmospheric rather re-ruited. but to change flanges on the mani and to have the Tial wg re-ruited is not the biggest task for someone with good welding skills...

goodluck tho

Geno~

Wreckless

07-12-2007, 04:51 PM

So long as you've got a big enough exhaust, you can go either way - but if you're on a 3in exhaust having an open dump will pick up a bit of power especially on a larger single.

OneJoeZee

07-12-2007, 05:03 PM

So long as you've got a big enough exhaust, you can go either way - but if you're on a 3in exhaust having an open dump will pick up a bit of power especially on a larger single.

How about in lower levels? Say 400-500?

My downpipes before they merge together to 3" are 2.75" each. You think there would be any noticeable gain having my wastegates opened to the atmosphere instead of back into the 2.75" downpipes? I don't plan on doing it but I'm just curious.

supra_natural

07-12-2007, 05:09 PM

its mostly for noise... sp is a company that sells their kits to re-route to the exhaust. and their kits make good power. it could make the turbo sound louder as its not drowned out by the semi-obnoxious sound of an open wastegate. however some do like the extra sound.

jdc0589

07-12-2007, 05:22 PM

How about in lower levels? Say 400-500?

My downpipes before they merge together to 3" are 2.75" each. You think there would be any noticeable gain having my wastegates opened to the atmosphere instead of back into the 2.75" downpipes? I don't plan on doing it but I'm just curious.

I dont think the inverse yields the same gain, if there really is any to begin with. The only way you might see slightly enhanced exhaust flow from converting from a recirculated system to an open system is if your recirc tubes were originally welded to the main piping at a really extreme angle, which would cause turbulence and hinder flow.

If the recirc piping is mated to the main pipe correctly, I can see how it might create a low pressure zone relative to the rest of the main exhaust pipe, which could scavenge a little extra exhaust gas/increase exhaust flow and turbine speed slightly. However, the effect would probably be less effective or totally non-existant if the recirc piping met back up with the main exhaust piping too far from the turbo. the smaller wastegate outlet piping obviously channels a much smaller amount of gas than the main pipe; meaning that its temperature/density, and therefore its velocity, will be effected much more by the outside piping ambient temps than the main piping. the longer the pipe, the greater the temperature loss in the gas is, and because of the smaller volume of gas being channeled by the wastegate piping, its temp/density/speed would decrease at a greater rate that that of gas in the main piping, and the last thing you want is a slow wastegate flow intersecting a faster main piping flow.

You would really have to do some serious lab testing to know for sure, but the gas velocity in the wastegate outlet piping would have to be a little greater (at the very least) than the gas velocity in the main piping at the point where the two pipes met for there to be any effect, assuming the joint angle was correct.

This is all just thinking out loud, but from a theoretical stand point, it seems like main exhaust pipe should increase in diameter proportionally to the increase in gas volume (from the recirculated wastegate) just after the recirc pipe meets back up with the main pipe.

On top of all that, because the volume of gas in the wastegate piping is so much less than the main pipe gas volume, there would have to be a very large velocity difference between the wastegate and main piping for the faster wastegate flow (assuming it could be faster) to positively effect the rate of flow in the main pipe and yield anything close to a noticeable gain.

If any of this is valid, I think it might might simply increase boost consistency more so than any tangible performance gain.

Hands On

07-12-2007, 07:04 PM

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