Stock CT-26 wastegate porting

[supradjza80]

Guys,

I was wondering if under any circumstances people have had to port a stock turbo wastegate on our cars. My car is currently spiking up to 13 psi (no shims, no boost controller) and I just replaced the wastegate actuator vac line from the compressor outlet.

I am aware that the problem could be the wastegate "flapper" hitting my DP (BIC DDP) or the wastegate actuator. The wastegate opens just as it always has, the DDP makes it very easy to hear it open, and it is beginning to open around 1-2 psi of boost. Assuming that both the actuator and the flapper are working correctly the only other thing I can think of for the boost creep and subsequent fuel cut (2-5th gear) is the the wastegate needs to be ported. Thing is I cannot find any information on a stock CT-26 needing this. I have seen that it is needed on upgraded wheels (57 trim etc.).

Does anybody know if it would be normal to have to port the wastegate with the following mods?

BIC DDP
Apex'i Intake
3.5" exhaust
Cooleze hardpipes
HKS BOV

Thanks,

Dave

 

[FullNelson]

I think I would check the wastegate/DP clearance before I went wild with a die grinder. Most people seem to just adjust for the spike and lower thier boost presssure so when it does spike it stays under fuel cut.

 

[s383mmber1]

I used to run a similar setup, and it would always spike. I made a manual boost controller, and shimmed my wastegate, and the boost never really spiked again. I set boost around 9 pounds, and it would hold it in every gear except 4th, which would slowly rise to around 11.

 

[WhtMa71]

You can port it a mm or two. The flapper is bigger than the hole.

 

[1992supraman]

On my old 1992 after I put on 3in exhaust I had to port the wastegate hole due to boost creep. My friend with a 7m mk2 also had to do the same. Upgraded exhaust outflows the stock size hole, causing extra exhaust to continue to spool the turbo. I would port it. There are a couple threads on here about how exactly to do it.

 

[supradjza80]

On my old 1992 after I put on 3in exhaust I had to port the wastegate hole due to boost creep. My friend with a 7m mk2 also had to do the same. Upgraded exhaust outflows the stock size hole, causing extra exhaust to continue to spool the turbo. I would port it. There are a couple threads on here about how exactly to do it.

I believe I am in your shoes but am not 100% sure yet since I haven't had a chance to check how far the wastegate is opening with the DDP (with a BIC I assume it should be ok anyway). From everything I have looked at it is unusual for a stock turbo car (of any amount of mods) to be needing a ported wastegate.

If I have to do it it is ok, but I do not want to split the turbo (turbine housing from center section) from fears of Fing it up. If I need to port it I will just take the turbo off and port it with the housing attached to the turbine center section with care taken to keep any grindings away from the turbo itself.

 

[1992supraman]

Before taking off the turbo I would disconnect the wastegate line from the compressor housing and use an air compressor turned down (~10lbs) to activate the wastegate, and you should be able to hear if its hitting the DP or not.

If I have to do it it is ok, but I do not want to split the turbo (turbine housing from center section) from fears of Fing it up.

?? Im not sure why you would need to split the housings... You can do it with the whole turbo together.

 

[grimreaper]

Cram paper towels into the exhaust side just past the wastegate so shavings wont find there way to the turbine. (cram them in TIGHT)

 

[Rennat]

if you go WOT, you shouldnt hear the wastegate UNTIL you get to 13psi...
if it starts to open at 1-2psi at WOT then you have a bad wastegate...
and i said WOT, not part throttle boosting or half throttle boosting, cause that normally doesnt fully spool the turbo.

and i have a BIC DDP and i know what you mean by you can hear the exact moment it opens, i've snapped necks with that sound. hahaha

the whole point of a wastegate is to bypass the turbine of the gasses and so it should only open at full boost, which you say for you is 13psi. so if you hear it under 10psi at WOT then you have a actuator problem.

 

[supradjza80]

if you go WOT, you shouldnt hear the wastegate UNTIL you get to 13psi...

I disagree with this, I have no shims, no boost controller and the stock actuator. It should open and hold boost at around 6.8 psi, maybe slightly higher with the mods.

if it starts to open at 1-2psi at WOT then you have a bad wastegate...
and i said WOT, not part throttle boosting or half throttle boosting, cause that normally doesnt fully spool the turbo.

Again, mine opens at maybe 1-3 psi which i think is perfectly normal operation leading me to beleive that the wastegate isn't opening far enough or i need to port the wastegate housing.

and i have a BIC DDP and i know what you mean by you can hear the exact moment it opens, i've snapped necks with that sound. hahaha

the whole point of a wastegate is to bypass the turbine of the gasses and so it should only open at full boost, which you say for you is 13psi. so if you hear it under 10psi at WOT then you have a actuator problem.

No it should be 7 psi, it just creeps up too 13 psi as RPM's increase and fuel cuts.

The reason for this thread is I cannot find any examples of people porting the wastegate on the completely stock trim turbo with any amount of mods. I was trying to find out if this is normal to have to port the wastegate on the stock turbo or if it is unusual and normally not needed (what i was hoping to hear )

 

[1992supraman]

if you search "boost creep porting wastegate" youll find some threads about why you need to.

and heres a link to a thread on how to: http://www.supramania.com/forums/sh...ighlight=boost+creep+wastegate+porting&page=5

 

[supradjza80]

if you search "boost creep porting wastegate" youll find some threads about why you need to.

and heres a link to a thread on how to: http://www.supramania.com/forums/sh...ighlight=boost+creep+wastegate+porting&page=5

I actually have already read this thread. That guy is running a 57 trim turbo which I understand needs to have the wastegate ported if you want to run stock boost levels. I am only interested in completely stock CT's. I have searched the forum using all terms related to wastegates and creep and cannot find examples of a stock turbo car needing to be ported. Upgraded wheel ct's are no longer stock.

 

[supradjza80]

Alright, so I just got done porting the wastegate this last saturday. I just wanted to post up that it alleviated all overboosting issues (wastegate was ported to 29-30mm and I smoothed the flow entering the wastegate). If people are having over boosting problems with the efficient DDP's I would be prepared to do this, even if you still are on the stock turbo (I do have a 3.5" exhaust after the DDP so the exhaust is very un-restricted).

Hope this helps others in the future who are unsure what there next move is if they experience boost creep with their DDP.