boost problem, could external wastegate be too big?

K

keirz

Member +
right im having a very annoying problem that im trying to solve.

it all started when i fitted my new set up. externally gated manifold, 38mm external wastegate with 1 bar spring and my own experimental hybrid.

since fitting i have never had correct boost, it has a 1 bar spring in the wastegate but if running straight from it you only get 6psi of boost.

when you turn the boost up with boost controller to 1bar it will just not hold, it literaly sees 1 bar on gauge, wastegate opens, boost drops instantly down to around 8psi. the drop is more visable in lower gears. so in 4th it drops at a slower rate.

i thought it may be the turbo, as it was shall we say a massive compressor wheel and a complete experiment, so i have changed the turbo to a stock ct9 and having the exact same thing so thats rulled that out

Any ideas? could the external wastegate be too big?

sorry for the essay
 
L

Llawgoch

Member +
what make is the wastegate, if its a cheap ebay one, throw it away and get a tial or a turbosmart wastegate!!
 
K

keirz

Member +
it is a cheap one but i know a few people running exactly the same wastegate with no problems. it may be worth a try changing it though i guess as its never been right. the 0.5 bar i got with it only made 2psi
 
MarckGlanza

MarckGlanza

Member +
maybe it doesnt have the 1 bar spring in it and only has a 6psi 1 as it will have more difficulty holding the 1 bar of boost with the small spring

marck
 
K

keirz

Member +
i brought and fitted a one bar spring mate. and i know many people who run around 1.3 bar off a 0.5 spring
 
L

Llawgoch

Member +
a lot of the cheap ones are renowned for sticking, that could be your problem, see if you can borrow a known good one off someone
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
MarckGlanza said:
maybe it doesnt have the 1 bar spring in it and only has a 6psi 1 as it will have more difficulty holding the 1 bar of boost with the small spring

marck
Click to expand...

my thoughts exactly... a 38mm wg is the ideal size for the 4e.. u should also want to check out ur boost controller, if it was set for an actuator setup before the solenoid (if its an ebc) needs to be recalibrated.

kon
 
K

keirz

Member +
im using a manual boost controller (bleed valve) i have it from turbo to the the controler, then controler to bottom port.

ive had it off and tested it and its moving freely. its as if it opens but then pisses all the boost away.
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
then theres ur problem.. there is something wrong with the mbc mate.. see if u can borrow one from a mate to see if the problem persists.. but if u ask me thats where ur problem is ;)

kon
 
G

GaryGT

Member +
dude throw up a pic of how you have it plumbed in
not a Fan of the MBC with EWG setups
but put pics up and maybe we can help you more


regards

G
 
K

keirz

Member +
ok still not resolved theis.

if i run straight off the wastegate i get 11psi.

if i use the boost controller to turn up to 14psi it gets there and then drops down to the 11psi and holds.

ive changed the boost controller to a new one so thats ruled out now. any ideas? must be wastegate but why?
 
TurboDave

TurboDave

Member +
keirz said:
yes mate, i think i would get the sack if i was that daft when it comes to turbos!
Click to expand...

I know just making double sure! Sure is a strange problem, I'dd bin the bleed valve though and at least get a dawes device ball and spring type.
 
K

keirz

Member +
i binned my old one and brought a turbosmart jobbie but thats just the same. i dont understand as no one else seams to have issues using them on external wastegates.

might just buy a new external gate and give it a go.

i would have though that a small exaust leak, eg the wastegate leaking from seat. would it really cause this problem?

ive tried petty much everything other than changing the wastegate, but i want some logic behind why that is the issue before i spend 250 odd quid
 
W

weakboy2

Member +
is it really laggy? have you fitted the insert into the valve area of the external wastegate? could be your exhaust blow, sounds like there is always exhaust coming out of the screamer.
 
K

keirz

Member +
it seems to hold at 11psi if i block off the top port on the external wastegate. which is strange as that should make no difference. its very irratic, sometimes it doesnt drop below 11psi some times it drops down to around 8. i cant make any sense of it. sometimes it will hold at 14psi for a few seconds, others its an instant drop off,

is not laggy at all, and until you get full boost you hear no exhaust blow noise.

it is as if all is fine until the wastegate actually opens.
 
Last edited:
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
if uv connected a vacum line to the top of the wastegate that isnt from the plenum & u dont have the mbc fully open then that may be causing the fluctuation... well you may be unlucky enough to have a torn diaphram, but id leave that for now..

kon
 
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