as aboves?i gather is on the outside ?but whats the benefits in these?is it still control via a actuator?also whats a screamer pipe do?any benefits etc?

 

obviously the ex wastegate is the wastgate but is not built into the exaust housing but it is built into the manifold

the ex wastegate allows the use off a bigger turbo as you can get bigger exhaust wheel in without the wastegate getting in the way.
i also THINK that because the wastegate in not blocking the exhaust gas flow on a ex wastegated turbo it decreases backpressure ? not 100% sure in that

also you can have very precise boost control you would have to use 2sets of air injectors or play with the spring in the wastgate

a screamer pipe i dont think has any advantage when we do a external wastegate turbo'd enine the exhaust is made at hatward and scott and the screamer pipe is plumbed back iton the exhaust system

hope this helps i think it is all accurate

 

ah cool!so it just allows a bigger exhaust wheel to allow the turbo to become more volume efficent?

 

Heyward and scott

 

I thought it was to help minimise exhaust gas turbulence in high boost applications?

 

heres the thread of our escos build if you look through it at the pic from page 3 onwards you will see the external wastegate and how it is "plumbed" in

 

this is an external wastegate, comes off the manifold before the turbo



and this is the screamer pipe exit



my exhaust system was also done by hAyward and scott, but its got to go back at some point, as i cant get full lock to the left, as the fuckwits put the screamer int he way and wheel hits it....

youd have think they may have noticed this

 

fudgey it dosnt have to come off before the turbo ! ours come off in line with the turbo i dont think it makes much difference

 

ah!so the screamer pipe is just the take off for the waste gate?i.e the unwanted boost in effect?and u can dump this either internal or external?is there any gains it either of these ways?

 

disadvantage of screamer pipe is you wont get on track !

and i dont think there is any dissadvantages tbh

 

Other thing to consider is that if you want to tail the boost off at the top end on an internally gated turbo, you can reach the point where the port inside the exhaust housing just physically can't bypass enough exhaust gasses and the boost pressure will creep back up at high revs.

External wastegates when specced properly provide very accurate control!

 

so out of interest at what point regarding held boost do u need to have a external wastegate? or is it just as said a more precise way to control the boost at higher rpm?

 

i think its more to do with the spec of your engine weather you go external wastegate or not tbh as if you want over 550 bhp you will struggle to find a good turbo capable of over that

a t4 even struggles with boost creep

you wouldnt put a external gate on a 400bhp turbo even if they did suffer slightly with boost creap because the gain isnt worth it

 

It's not about what boost you run, more about a point in the airflow scheme, where, as Will said, an Internal Wastegate just can't be big enough to do the job.

That said, it's not a case of biggier is better with External Wastegates, most people go over the top. Gary's 700bhp Evo runs a Tial 38mm Wastegate, same as I run on mine. Mine is sprung at 1.5 bar and I make 1.4 bar absolutely flat with no boost control.

 

i have one because the turbo i have didnt have an internal one, only reason lol

jimbo, yes you are correct about where the come off, but 99% of them are before the turbo due to manifold design.

if it comes off after the turbo tho, it wont work lol

 

cool cheers just was not sure about what the point in both of them was!

 

Thought the Evo ran two wastegates? I'm sure I asked this on his thread?!

 

No, Gary's Evo runs just one Wastegate. It's AFTER the turbo too.

 

Oh, any pics?

 

Will update his thread soon. There's some developments and the pics I post will show the Turbo pipework.

 

Chop chop then

 

christian, how the fook does that work then, as the point of a wastegate is to bypass the turbine to stop it over boosting no...?

so if its after the turbine, it will be bypassing nothing?

 

just dont see how that can work if its after the turbo, surely it got to be before the turbo other wise its venting the exhaust gases after they've already passed thru the turbo

 

LOL. It's an AMS kit and I think they have at least half and idea what they are doing!!

The Turbine Housing has the normal discharge and Wastegate hole as though it was Internally 'gated, but with no flap. The hole is enlarged too. Then the Turbo Elbow is divided and the Wastegate section of the housing goes directly into a Tial 38mm Wastegate, which in turn discharges directly into the main exhaust.

I'll put a pic up of Gary's new Turbo elbow that Chris has just made next week. Will make sense then.

 

was gonna say, i need a pic lol

 

thinking about it, i can see how it would work lol

learn summut new every day lol

 

Not the same turbo as Gary's but the same kind of setup

 

But is there gains if you do run your screamer pipe to atmosphere, rather plumbed back in your exhaust, or mainifold ???

 

Plumbing the screamer pipe back into the manifold would be a stupid thing to do, the exhaust gasses wouldnt be bypassing the turbo at all then

If your exhaust is too small and cannot cope with the amount of air being forced through it then venting the screamer pipe to atmosphere would be an advantage, but other than that its just noisier. If your exhaust is too small, the best thing to do would be get a larger/free'r flowing exhaust on the car and plumb the screamer back into that.

 

Here are the pics of Gary's revised Turbo Elbow. Obviously it's not been TIG'd yet, just tacked, but you get the idea.

It's done 700bhp on roughly that setup, 38mm Wastegate, with a 3" downpipe.

 

How is that an advantage over an internal wastegate? You're using the same hole!

 

I like that

 

It's the size of the hole thats relevant.

Also, the External Wastegate gives much better control.

 

What size is that downpipe??

 

3"

 

The wastegate might be situated AFTER the turbo but it still takes the exhaust gases from before the turbo

 

But you need to look at how the flap is attached, a internal gate is hinged like a door and is only opened on one side so this limits the flow of the hole,
A external wastage has a flap that moves away the same all round so for the same peak lift it can flow more than a internal gate, unless you use a real big bypass hole you cant flow the same, space and packaging is one of the reasons why they can control the boost better but also the smaller hole helps as theres not a instant drop with a hole thats to big.

Mark

 

a external wastgate uses a valve not a flap does it not ??

jim

 

yes I just simplifide it.

Mark

 

ahh okii i wont start confusing then lol

jim