View Full Version : 4g63 overboost problem (20+ psi!!!)
streatracer
02-12-2009, 11:02 PM
I'v got an 89 Mitsi VR4, with 3"exh, chip, tdo5, and gay divorced dump.
The car is supposed to run .7bar, but when you rev it out it gets chronic boost creep and climbs massively (1.5bar+)
The car has no boost controller and all vacuum lines appear fine.
Any ideas?
waste gate opening too small, that's the issue i had with my fc. not sure if it applies. fixes are porting out the wastegate or changing to a less free flowing exhaust ie. smaller diameter
fucked actuator.
try blowing on the line that goes to it (with your mouth..) or use a bike pump to see if its leaking
R31 POWER
03-12-2009, 06:12 AM
''gay divorced dump'' is my guess. Pics of it?
acutator is fucked I've had the same problem on my old evo. just find a replacment one.
1.5 bar... why is this a problem?
1.5 bar... why is this a problem?
easy for you to say seeing as your car has never seen 1.5bar!
to4garret
03-12-2009, 01:01 PM
http://team4g.com
those guys know their stuff when it comes to VR4's etc.
i think i know whats causing it, but just do a quick search on that as it has been covered numerous times. surfice to say its very common.
3" exhaust with a 16g yea? ;)
easy for you to say seeing as your car has never seen 1.5bar!
:lol: :lol: :lol:
I agree, because it see's more than that regularly.
Lonewolf
03-12-2009, 02:50 PM
1.5 bar... why is this a problem?
true, its not a DAK DAK is it
Nor does it rev to 10,000rpm and only make 150HP :D
Lonewolf
03-12-2009, 05:32 PM
Nor does it rev to 10,000rpm and only make 150HP :D
:lol:
I walk faster around wanneroo than you've lapped it. :shake:
streatracer
03-12-2009, 11:34 PM
acutator is fucked I've had the same problem on my old evo. just find a replacment one.
aha I'll start trying to source one. cheers
1.5 bar... why is this a problem?
cos its a mitsi lol. my nissan runs 1.6bar all the time haha
aha I'll start trying to source one. cheers
how about testing the one you have, its not hard
streatracer
04-12-2009, 09:09 AM
how about testing the one you have, its not hard
obviously I should have mentioned I'd test it first.
although after some time on team4g it sounds like the wastegate is just too small on these turbos (especially with big exhausts) might smash an external on for a laugh :P
boost creep due to smallish wastegate does not give you the result you seem to be getting.
because of the position & orientation of the actuator & the combination of age & water getting in, they are well known to fail. its a very common issue.
to4garret
04-12-2009, 01:18 PM
boost creep due to smallish wastegate does not give you the result you seem to be getting.
yes it does.
due to the car running a larger turbo (compressor side) than standard, while also having a more free flowing exhaust creates an enviroment where the stock wastegate opening (24mm) can be maxed early in the rev's.
its actually a design fault with the TD05H 070 exhaust housing, where the passage to the interal gate flapper is at 90deg to the exhaust flow and very poorly smoothed from factory.
basically what happens when a free flowing exhaust is installed, is its much easier for the exhaust to pass through the turbine housing rather than the small stock gate. this starts to over speed the turbo because the gate can not control boost by bypassing the required volume of exhaust gas. the higher up in the rev range the worse the problem becomes due to engine load and increased engine cycles.
mitsi's
DTM-031
04-12-2009, 04:21 PM
boost creep due to smallish wastegate does not give you the result you seem to be getting.
because of the position & orientation of the actuator & the combination of age & water getting in, they are well known to fail. its a very common issue.
common issue yes but if you think boost creep isn't caused by insufficient flow for a wastegate then you're an idiot lol. why do you think people use external wastegates - internal just doesn't flow enough, especially when the factory decides to manufacture them ridiculously small.
luke, i haven't seen these particular turbos but it may be possible to mill out the wastegate hole? otherwise yeah time for external - blessing in disguise! :P
to4garret
04-12-2009, 04:42 PM
you can usually gain a couple of mill by porting the wastegate hole and keeping the stock flapper. i think you can get upto 3mm if you go a larger flapper.
the biggest gain comes from porting the passage from the turbine housing into the wastegate hole.
the GTPumps housing is okay luke. but you can get the same/better result just from porting it yourself.
common issue yes but if you think boost creep isn't caused by insufficient flow for a wastegate then you're an idiot lol.
yes you would have to be a complete fool to think that & it would show a complete failure to understand boost control basics. so before you make stupid assumptions, try reading what i said properly.
i said to the extent that he is getting..
he seems to be FREEBOOSTING - you know, uncontrolled boost... Not somewhat controlled boost to a point & then creep
why do you think people use external wastegates - internal just doesn't flow enough, especially when the factory decides to manufacture them ridiculously small. yes i know that & yes i have experienced real boost creep, due to the w/g being too small
...
yes it does.
we can only guess what is happening from the op's descripton & to me it sounds like he has no boost control at all...& that is not techincally boost creep.
it sounds like he is freeboosting
The car is supposed to run .7bar, but when you rev it out it gets chronic boost creep and climbs massively (1.5bar+)
just because he describes it 'boost creep' doesnt mean it actually is..
to4garret
04-12-2009, 05:00 PM
if it was freeboosting it would spike over 30psi at 4krpm, what luke is describing is a really common issue with VR4's and his description is typical of boost creep not freeboosting.
luckily i didnt kill my engine when i free boosted it. stupid gizmo.
well he said hes hitting 22psi plus with a 10psi actuator, seems too high & sudden for creep to me.
he really needs to test the actuator, it takes 30sec.
question for op.
has this problem just occured for seemingly 'no reason' or have you just put this turbo/dump/exhaust combination together?
streatracer
05-12-2009, 11:02 PM
we can only guess what is happening from the op's descripton & to me it sounds like he has no boost control at all...& that is not techincally boost creep.
it sounds like he is freeboosting
just because he describes it 'boost creep' doesnt mean it actually is..
Not freeboosting, holds boost for a while rock solid at .7bar then starts rising
(I removed all the lines to the actuator yesterday so NOW its freeboosting lol. so wont be driving it till replace lines)
well he said hes hitting 22psi plus with a 10psi actuator, seems too high & sudden for creep to me.
he really needs to test the actuator, it takes 30sec.
tested. seems fine.
question for op.
has this problem just occured for seemingly 'no reason' or have you just put this turbo/dump/exhaust combination together?
car has always done this. but since my partner has been driving it and you have to rev it quite hard before it starts rising, it was never a problem for her.
holds boost for a while rock solid at .7bar then starts rising
ok that description seems quite a bit different from the first post & with the other info (actuator not leaking, allways done it etc), says that yes it sounds like creep.
time for gate mods or external :D
streatracer
06-12-2009, 12:00 AM
external ftmfw! :D
dumb question but can u weld ext gate flange onto factory cast manifold? (I know NOTHING about welding)
yeah it can be done, ive even seen them welded to the turbine housing.
another (slightly more bodgyer) way is a spacer plate mounted between the turbo & exh mani, that has a flange on it to mount the external gate
ZedEx
10-12-2009, 03:39 PM
http://www.gtpumps.com.au/turbine_housings.html
You can buy an exhaust housing to suit your turbo with an improved wastegate flapper/port... prolly a cheaper option than going external and should do the job. The GT Pumps gear is good.
POTTER
10-12-2009, 03:44 PM
1.5 bar... why is this a problem?
:werd:
perfect amount of boost for a performance dak:)
evo5aurus
19-01-2010, 09:31 PM
cos its a mitsi lol. my nissan runs 1.6bar all the time haha
not entirely sure about the 6 bolt 4g63's but the later 7 bolt ones will run 1.5bar quite happily
my stock evo V runs 1 bar and plenty of guys are running 1.5 bar with minimal mods (exhaust, intake, tune etc)
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