external wastegate questions

[markey b]

in theory, an external wastegate should help control my VNT better, stopping spike? correct.

have been googling but there is so much is hard for my little brain to take it in and digest to find out whats best for my little car

i'm pretty sure that i've read that for big boost, a smaller W/G is advised, but for lower boost a bigger one is needed... that doesn't make sense, so can someone correct me if i'm wrong.

also, would i be able to run the W/G seperately from the bleed, so that at low boost the W/G stayed shut, and was controlled by the VNT itself, eg. 14psi, but then when the incar boost is turned up the W/G will control it at full boost (27psi) or am i dreaming up something so complicated that it'll cost £££ in electronics and boost controllers etc, i just fancy a screamer pipe but would like it to keep quiet on day to day low boost and only wake up on big boost.

lastly, i've been looking for an adaptor to fit the W/G in between manifold and turbo, all i can find are T25 to T3 adaptors, i'm assuming that its something i'd need to get made up by an engineer or someone equally clever? i dont want a k-tec manifold as i could get a take off on the collector, but its not a route i wanna take.

does anyone have any suggestions etc? any would be appreciated :)

[Scoff]

well, the sizing thing makes sence really, you need to think about it like this:

if you run a lot of boost then the wastegate stays shut more than it does when your running less boost, because more is being forced through the turbine to create boost. So, if the wastegate isn't opening as much then it doesn't need to be as large because you don't have as much gas going through it.

If you had a small capacity 400hp or less engine running high boost you could probably use a 38mm gate. if you had a big capacity engine that made the same 400hp with only a little bit of boost then 38mm would be too small since it's being asked to remove a lot more exhaust gas, get it ? you would be fine with a 38mm gate.

I havn't tried any of this before but I guess you would want to set the gate up so that it started to open at 27psi, such that if you had a normal turbo it would hold 27psi of boost. you could leave your vnt set where it is (27psi constant). The external wastegate should catch any spikes over 27psi. the gate should stay shut 99% of the time, only opening to vent the spikes, which leaves the vnt to control boost at anything upto 27psi.

as for the manifold, I've seen a 30mm pipe welded into a cast manifold before now, just before the collector, it had a screamer pipe from the other side of the gate, that should be pretty simple for you to do :)

[markey b]

cheers scoff! that does make sense now about the size, as its due to the 'waste' gas and yeah there is less at big boost.

silly question, but are cast manifolds easily weldable??

last silly question, yeah you get my jist about it catchin spikes over 27, but if i piped that into the std vac circuit, and left the VNT on the bleed would i still be able to run normal VNT actuator boost (14psi) with the bleed shut off?

i just dont wanna run 27psi all day long for obvious reasons

[TNT ANDY]

New poster! (less than 10 posts)

'i just dont wanna run 27psi all day long for obvious reasons'

Your getting old Mr 'B'

[markey b]

New poster! (less than 10 posts)

'i just dont wanna run 27psi all day long for obvious reasons'

Your getting old Mr 'B'

lol.... i'll never catch ya up tho ;)

hows the norfolk division gettin on?? ross had many more turbo's since nat day?

[Os8472]

New poster! (less than 10 posts)

'i just dont wanna run 27psi all day long for obvious reasons'

Your getting old Mr 'B'

He's gettin very old, I remember a time when he drive his R5 right the way through winter (unless it was bust) but now he gets around in a reliable R19cab with a heater, how times have changed:laugh: