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| External wastegate dump. any GAIN? http://www.4g61t.org/forum/viewtopic.php?f=6&t=5744 |
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| Author: | boostfreak [ Wed Oct 15, 2003 12:08 pm ] |
| Post subject: | External wastegate dump. any GAIN? |
Ive been hearing that people actually see gains from externally venting the wastegate exaust, even up to .3 in the 1/4. IS this true or is it just for the menacing sound? |
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| Author: | dsmracer [ Wed Oct 15, 2003 12:28 pm ] |
| Post subject: | |
It depends on how much boost you're running. Anything above 20 psi and it's a good idea. |
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| Author: | boostfreak [ Wed Oct 15, 2003 3:59 pm ] |
| Post subject: | |
Im gonns run 24psi with an internal gate, so I should go external dump? My friend can weld anything (even aluminum) and does not care about money. Hell hook it up if I want it. |
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| Author: | LILEVO [ Wed Oct 15, 2003 5:22 pm ] |
| Post subject: | |
You'll notice a top end gain right away along with maybe a little loss of low end power. |
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| Author: | dsmracer [ Wed Oct 15, 2003 6:06 pm ] |
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It's a good idea to upgrade the wastegate either way. I plan on running 25 psi with an upgraded 34mm internal gate. |
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| Author: | BlueBullet [ Wed Oct 15, 2003 8:47 pm ] |
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my friend used to have an external dump on his wastegate...he rerouted it back in and he said he felt a loss in top end.... |
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| Author: | PiercedJD [ Wed Oct 15, 2003 8:58 pm ] |
| Post subject: | |
the only reason for running an external dump on your wastegate is to control boost creep. if you are not able to maintain a set boost level under WOT because there is too much backpressure on the wastegate side and it is unable to adequately vent off enough gas to control turbine speed then you should switch to an external dump, or an external wastegate with a larger valve. alone it is not going to (or rather I should say "shouldn't" ) affect performance. during part throttle normal driving, the wastegate should be closed as it is not seeing boost at the diaphragm to push it open, so you shouldn't see any loss there. Up top/during wot driving it is just allowing more gas to bypass the turbine wheel and your exhaust system. the wastegate valve/flapper door is still regulating how much of this gas is escaping. it is not a performance booster, just a better way to control your boost *if* you are experiencing bost creep. |
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| Author: | LILEVO [ Wed Oct 15, 2003 9:01 pm ] |
| Post subject: | |
Yeah but when you circumvent all the excess air out a 2.5" external dump while still having a 2.5" exhaust path rather than trying to cram it through with the exhaust through the stock 1.75"(?) O2 housing that opens things up a little |
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| Author: | PiercedJD [ Wed Oct 15, 2003 9:16 pm ] |
| Post subject: | |
where the heck are you going to fit a 2.5 external dump? hell I haven't seen a external gate with a 2.5" valve. you aren't going to flow more than the size of the valve anyway, so what is the point in doing something like that? furthermore, being that we have already stated you are not going to flow more exhaust than the valve itself can redirect, if your stock exhaust is able to keep up with that demand why would you want to add something that just sounds like an obnoxious exhaust leak when you are not seeing a gain from it? the valve is only going to open and redirect ENOUGH EXHAUST GAS TO MAINTAIN THE BOOST LEVEL YOU ARE REFERENCING AT THE WASTEGATE DIAPHRAGM it isn't going to open more than that, or vent more exhaust because it is dumping externally. EXTERNAL DUMP ONLY HELPS WHEN YOUR WASTEGATE NEEDS TO REDIRECT MORE EXHAUST THAN IT CAN THROUGH THE STOCK DIRECT PATH OF FLOW. then you need to increase the size of the current dump with an O2 eliminator, or vent it externally. and even then it may not solve your problem. you may just have to small of a valve, or too small of a flapper door (internally gated) to vent adequate exhaust to control boost creep. that is all the discussion that is necessary about external dumps. period. |
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| Author: | LILEVO [ Wed Oct 15, 2003 9:20 pm ] |
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My O2 dump housing is 2.5", the external dump tube is 2". The wastegate flapper is in the exhaust housing. The stock O2 housing is maybe 1.75". The same amount of exhaust gas is going to flow through both units. With the 2.5" tubular housing more air is going to be able to efficiently flow through that unit than the restrictive stock unit. Why do people port their O2 housings or go with 2G/EVO housings? To get more flow to open up the exhaust = more top end. That was my point, might be totally off base, but that's what I was trying to get across. |
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| Author: | boostfreak [ Thu Oct 16, 2003 11:31 am ] |
| Post subject: | |
It makes sense to see a gain because all that extermely turbulent air is not going into the path of the turnie exaust, so it can flow smoothly and quickly out of the turbo. Or at least thats what David tells me, but what does he know anyways. side note: thats david Buschur I speak of 
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| Author: | Guest [ Thu Oct 16, 2003 11:48 am ] |
| Post subject: | |
I saw a gain when I put my dump tube on. I recently took it off. Once I get the car running again, I fully expect that I will have a loss in top-end power. There are a couple of reasons you would expect there to be a gain, one of them being that most dumps have larger piping then the stock pieces and when you vent that air that close to the engine, it's that much air that the engine doesn't have to push through the exhaust. And it is quite a bit of air that gets dumped out of it. |
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| Author: | dragstr4g61t [ Thu Oct 16, 2003 1:33 pm ] |
| Post subject: | |
It sounds like there is a gain to dump externally but when does it become an issue? I'm getting ready to put a 14B with 2G manny and O2 sensor housing on my 4g61 along with all the corresponding parts. Would I benefit from an external dump tube running 17-18psi with this set up? Or would it just be a wasted cost. If I could even gain just .2, I will do it. |
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| Author: | Guest [ Thu Oct 16, 2003 2:30 pm ] |
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I'd bet you would easily gain .2 in the 1/4. But to answer your question, it's most likely not going to be necessary. |
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| Author: | PiercedJD [ Thu Oct 16, 2003 3:44 pm ] |
| Post subject: | |
Ok, let me rephrase. the trade off on say a 14b running 17 psi is not worth having an annoying exhaust leak in your engine compartment that becomes obnoxious at wot. You are not going to see a major gain from it. It is not going to assist in controlling your already non existant boost creep. No doubt dave buschur told you it's good He sells them You will probably see a miniscule gain from it. Will it be repeatable from day to day? These cars have the consistancy of a butcher with down syndrome. One day she's giving you prime rib, the next it's rump roast. If you want to add an exhaust leak to your car feel free. Everything I had to contribute to this thread has already been stated above. I have seen several external dumps go back to an internal dump because they didn't see any signifigant gain from it, they weren't having problems with boost creep, and they were tired of the annoying sound of it during daily driving. |
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