What does the wastegate do and what are the differences between an internal and external wastegate? Any advantages?

 

The waste gate controls your boost preasure! Along with a vacume controler! The external waste gate gives a more presise boost preasure and are more expensive than turbos with internal waste gates! The internal gate is less effective but works really well for what it is! I like the internals they work great and don't really have that many prob with them! plus the cost has to be factored into it! externals are very expensive!

 

The turbo exhaust manifold passes the exhaust gases to the turbine section of the turbo. This causes the turbine.. and the compressor to start spinning and making boost. As the volume and strength of the exhaust pulses increases... the turbine/compressor is spun faster.

What the wastegate does is *shunt* exhaust gases away from the turbine section... either out to the atmosphere or into the exhaust after the turbine... decreasing the strength and volume of the exhaust gases spinning the turbine.

An internal wastegate is built into the turbine housing itself... An external wastegate is attached to the turbo manifold (therefore *external* to the turbine housing).

What the wastegate is trying to do is *waste* enough exhaust gases to keep the turbine spinning at a certain maximum level.... your highest set boost pressure.

This ability to *waste* exhaust gases is dependant on several things... size of the wastegate diaphram, flow characteristics into the wastegate, and then wastegate response. We will ignore wastegate response because that is dependant on the actuator / spring... things that are not really relevent to internal vs external.

Internal wastegates are limited on their size due to their placement and fitment into the turbine housing... but they usually have very good flow design into the wastegate.

External wastegates can be made as large as you want them to be.. the mounting for the wastegate is VERY critical. It should be in a direct path of the exhaust gases to be maximally effective. A huge external wastegate mounted at a poor angle from the exhaust gases can perform worse than a small internal wastegate with a good turbine housing design.

Also the price, many of the smaller / mid size turbos have a built in internal wastegate... no additional charge.. An external wastegate will run from $200 to $600... depending on quality and size.

Of course, if you run a huge turbo and the engine can handle the boost... you may never need to *waste* any exhaust gases. Nearly all the Pro turbo Tiburons in Korea run NO WASTEGATE.

 

Damn, crystal clear now. Thanks!!!! wink

 

Cheuk/Random/Red, what would be the disadvantages of having the wastegate installed on the downpipe, I've yet to see a setup like this, and have been looking thru the web for it, but can't seem to find info on it...

 

what do you mean by *on the downpipe*? The downpipe is after the turbo, so venting gases after that would do nothing.

If you mean: route the watstegate exit to the downpipe, as opposed to a separate exhaust path; then I'd say the difference is legality and complexity. It's better to have the wastegate have its own exit path: less restriction, less complex under the hood, but you have to basically have a second exhaust under the car. Routing the wastegate exit to meet up with the turbine exhaust on the downpipe is more complicated in the engine bay, but after the initial contortions, they share the common exhaust, which is easier.

But the main point is that the wastegate has to be between the turbine and the engine or it will not work.

I hope I understood your question right (and explained it well).

ac

 

See here's my problem they can make a flange on my manifold, but that would take from the pretty look of it... hehehe, so it was suggested to have it on the downpipe, but like you said, i didn't understand why, if that would be almost worthless since to my understanding too, it has to be between the manifold and the turbine... I will ask exactly what they meant, the problem is that until they get the car up on the lift, and start messing with space and all that, they are just speculating so much stuff... so I rather just wait until they have everything...

 

I think this is what they want to do, using the pipe on the o2 housing ment for the internal wastegate exhaust, and slapping on the eternal wastegate control their. also making the old internal wastegate whole large.

****ty construction, it will slow down spool time.