Why does my car overboost?

[s14alex]

I have a blacktop sr

gt2871 .64
deatschwerks 740s
enthalpy rom tune
fmic
tial 38mm on stock mani

My 1 bar spring gives me 1.35-1.4ish

I thought it was due to my shitty dump tube, but my new one makes almost no difference other than sound.

The wastegate is located in the same spot I've seen on other successful builds, right above the turbine flange.

The car runs perfect, but the higher boost is causing it to studder (detonating....?)

Any ideas?

:aw:

[xblack240x]

Re-check the spring or get a new one.... Just a guess this happened to a friend of mine before....

[Big Bronze Rim]

Where are you getting your wastegate signal from? Off of the compressor housing or from the intake manifold? Does the overboost hold constant or is it more of a spike coming onto boost?

[SuicidnS13]

I have a blacktop sr

gt2871 .64
deatschwerks 740s
enthalpy rom tune
fmic
tial 38mm on stock mani

My 1 bar spring gives me 1.35-1.4ish

I thought it was due to my shitty dump tube, but my new one makes almost no difference other than sound.

The wastegate is located in the same spot I've seen on other successful builds, right above the turbine flange.

The car runs perfect, but the higher boost is causing it to studder (detonating....?)

Any ideas?

:aw:

You say its studdering, like while under boost its hesitating? This could be a maf problem as well.

[ROIDMONKEY]

what type of boostcontroller r u using?

[s14alex]

Im not using a boost controller, just the Apexi AVCR as a gauge (not plumbed into the vacuum source)

The maf is brand new from oreilly auto, wired correctly, been working for over a year perfectly

Im getting my vacuum source to the wastegate from the compressor housing. (bottom nipple on wg)

[s14alex]

Oh and as far as the studdering problem im using ngk bkr8eix (iridium) gapped to .024in

[s14alex]

The overboost is constant

[Z U L8R]

it's more accurate to run the boost source from the manifold, cause the initial charge at the compressor housing will start off a little more than what is actually going into the plenum passed the throttle body.

also make sure you have zipties on all your boost/vacuum lines, doublecheck ur guage is accurate (find a way) and if the problem continues you may want to inspect your wastegate diaphram for tears/rips/holes.

hope this helps
Dave =]

[kamikazekid]

it's more accurate to run the boost source from the manifold, cause the initial charge at the compressor housing will start off a little more than what is actually going into the plenum passed the throttle body.

also make sure you have zipties on all your boost/vacuum lines, doublecheck ur guage is accurate (find a way) and if the problem continues you may want to inspect your wastegate diaphram for tears/rips/holes.

hope this helps
Dave =]
shouldnt you be running the pressure source from the turbo side of the throttle body to the wastegate.? and the blow off valve from the mani? If you run the vacuum hose to the waste gate from the intake manifold, when the throttle body closes it cuts of the prssure signal to the waste gate causing it to not open and overboost correct?

[Z U L8R]

no. for an external wastegate it doesn't really matter if it gets boost and vacuum or only boost, for an internal wastegate it doesn't really matter either, however it is recommended not to have vacuum, but only boost going to your internal wastegate actuator.

it doesn't matter what's in your intercooler pipe, it matters what your engine is ingesting from the manifold. typically there's close to no variation because when you're building boost YOUR THROTTLE BODY IS OPEN BECAUSE YOUR FOOTS PUSHING THE GAS PEDAL......so theoretically you will have 14psi on the charge side, and 14psi on the throttle body side. but in reality, blow off valves are more responsive when they're on the throttle body side of the intercooler pipe (which u will see factory on RB20 and RB25 stock intercooler piping for an OE example)

and what i said, the boost source for the wastegate, if you look on sr20's is after the throttle body flap (technically after the tb), on rb's is after the throttle body so...........no kamikaze that's not correct.

when the throttle body closes, it blocks any boost from going into your engine (discounting the bypass for the iacv) your blow off valve will open (another reason your car won't overboost when the throttle body closes), with the throttle body closed and little/none air going into the engine, your exhaust gases aren't building as much pressure either, therefore little/no boost output from your turbo. so of course it won't overboost with the throttle body closed...at idle my throttle body is closed, and my engine has a shit ton of vacuum and my car never overboosts with the throttle body closed.... :P *hug

Dave =]