falcongsr

i need to increase the flow of my internal WG and it looks as though I can get some relief from my creep problem by doing so. i dont know if it will be enough though.

it might hold boost fine at 5-6psi but at 7psi or more i am worried that the exhaust volume will be too great and it will resume creeping.

i experienced minor spiking with 2" open downpipe. with a 2.5" downpipe and 3" exhaust its impossible to control boost.

is porting it going to be worth it or am i gonna have the same problems on anything above low boost?

JM Performance

That makes no sense. Think about it. If you run more boost, that means you want more exhaust going through the turbo, and less through the wastegate. You'll have more spiking at lower boost than at a higher boost.

I dont know why, but everyone has this misconception: that with more boost you need a bigger wastegate.

KC GSR

he needs his wastegate to hold boost more steady, which means that it needs to be able to flow out more exhaust if I recall correctly.

xci_ed6

more boost=more exhaust.

I don't know how to port the WG. You could try an open dumptube, if you dont have that already.

-Dustin

falcongsr

well here is where i get my misconception.

when i have the WG actuator arm disconnected and the WG port is wide open

how much boost should I see? none would be ideal. at about 6500rpm i see about 8psi spiking to God only knows how much boost!

what do you recommend i do to make this setup stable?

glagola1

I've got an internal wastegate and I've dealt with some problems too so I hear you. Anyway, do you have an EBC? I had some creep before I got the controller simply because I was using the length of the actuator arm and the spring in the actuator to control boost. That didn't work when I turned up the boost by putting more preload on the spring and I got creep up in the high rpms.

I got a Greddy PRofec B and dialed in to 10psi and it holds like a rock all the way to redline. I still get creep when it's at the low boost setting of 6psi. Near to redline it will creep up to 8.5psi but I can't overcome that with an internal wastegate. At least it will hold at 10.

falcongsr

interesting. maybe there is some compressor wheel load vs exhaust flow equilibrium point at reasonable boost levels. i think i will port the WG and give it a try and check out the boost control setup on the ems.

BigD+Itsuki

Well this post really put the brakes on my soon to be custom exhaust for my Greddy SOHC turbo. I was planning on having a custom fabricated 2.5in to 3in down pipe followed by a full 3in cat and thermal exhaust. Im just trying to take every precaution I can seeing as I can not afford to overboost an engine and have it blow up.

Would an EBC be able to solve this dilemma? Would an EBC just control the WG similar to the stock boost controller and more or less regulate boost spike rather than boost creep. The boost controller can't open the WG more than it already does correct? So if the waste gate flows insufficiently electronically regulating it isn't going to be any better, correct?

I know in an earlier reply someone had an EBC and noted the fact that he was still creeping from 6 to 8.5. But at his higher boost setting of 10 he noted it was rock solid. Would this lack of creep be caused by the fact that the turbo is using the previously dumped excess pressure to keep the turbo spinning?

1.) Less excess pressure ->
2.) Less air needed to be moved through the WG ->
3.) Less boost creep because the WG can control the new, lesser, amount of air. ?!?!?
If this equation doesn't make sense to you your not alone...

Is there any way to fix this problem? Besides an external WG? Ported Internal WG? EBC controller? I really don't want to restrict performance i.e. using crap exhaust to prevent boost creep.

Any information regarding my nonsensical rambling is appreciated. Well, not any information ... try to keep it informative and don't say search. (its been done)

DeepSi

People are hitting 12-18 psi on clubsi with the greddy kit with not that much of a problem, well not many people have reported problems. So with a 2.5" dp and 3" exhaust you have large boost spikes? That sucks. What kinda boost controller are you using, the one with the AEM boost controller?

DeepSi

I know Avatar and 2000Si-at-UK on this board have taken the Greddy kits up to 8-10 psi from my knowledge maybe they can reflex their experience with us.

b18CT

i was boosting my old greddy kiy up to 18 psi spiking up to 22 psi (18gturbo kit)
i had lots of prob (boost spiking,boost creep)
i took of the greddy downpipe whit a custom one (2.5inch steinles) whit dumptube and 3 " exaust no cat
a dsm mecanic guy told me that i had to port and put a bigger cent (wg)but i didint doit
i have picture of my old downpipe if someone wanna see

b18CT

ohh forgot to tell that i had the spiking and boost creep after i did the new custom downpipe
this kit is no good for 15 psi and + so just sell it and get a real custom kit whit a real external wastgate

paulzy

iTrader: (1)

Joe, I got an Idea...weld that baby shut, weld an external WG flange on teh turbine housing, and throw an external on there

DeepSi

Yeah that is the easy way out, but for the people that want it to stay legal does not help us any

b18CT

you will have to ditch the cent (wg) and port the hole (where the cent is)alote bigger, then weld an external wastgate but it will cost you $$$$
just sell the kit and go whit a custom t3t4 whit a better manifold
that my personal opininion
im sorry for my engrish gramatical

falcongsr

i wont be running over 10-12psi on this turbo ever...i'll go external wastegate if i want more than that. but i doubt it.

here is my temporary fix:

replace the gasket between the cast downpipe piece and the downpipe with a steel plate with a 1.5-2" hole in it to add some restriction. this should allow me to at least handle the stock boost levels. then i can enlarge/remove this plate when i port my WG someday. i know adding restriction to a freeflow exaust is dumb but its a cheap *** fix that will get me on the road tuning my car again. i am ******* broke just bought a washer/dryer no money or time.

DeepSi

This might be a stupid question, but why are you add a restriction plate on your downpipe for?

falcongsr

because with a 2.5" downpipe, and the WG port wide open, i got lots of boost. no control at all. with WG port wide open, i'd hope to get 0psi but that doesnt happen. she spools and boosts A LOT. the restrictor plate will help me observe and control this problem as an easy short term fix - at the cost of optimal exhaust flow for the time being.

boost controller wont gonna do anything if the WG port is too small to control boost. so i have to add restriction. i dont know how this actually allows more exhaust flow to go thru the WG port vs the turbine. its some kinda dynamic feedback thing with the turbine/compressor increasing the flow.....

falcongsr

after a brainstorm session with a mechanical engineer here at work it sounds like it comes down to the pressure differential between the exhaust manifold and the downpipe is what causes the turbo to spool. to control boost, you can lower the exhaust manifold pressure (which a tial WG does very very well) or raise the backpressure in the downpipe to minimize the pressure delta on either side of the turbine wheel.

i really need to port the WG. just concerned i wont be able to port it enough.

falcongsr

falconGSR: i think i got it figured out
falconGSR: i think i understand how it all works
falconGSR: why the internal WG needs ALWAYS needs SOME restriction
falconGSR: cause not only does it bypass the turbine wheel but it INCREASES the pressure on the downpipe side and that slows the turbo
falconGSR: where the external tial WG just relieves so much manifold pressure that it just controlls the turbine speed directly
falconGSR: you need some restriction to trap some of the exhaust gases near the turbine outlet to raise the pressure enough to minimize the pressure differential on both sides of the turbine.

i just proved conceptually why external wastegates own.

Boostless97Lude

hrmm... this is good info. i was think of buying THIS to help eliminate a boost spike problem at higher psi


[Modified by Boosted97Lude, 9:49 PM 1/9/2003]

falcongsr

Success!

I installed the restrictor plate in between the cast part of the downpipe and the 2.5" downpipe that tony made me. With a 1.5" diameter hole, I get very good spool characteristics and controllable boost. Was steady at around 7psi which is perfectly adequate for my current setup.

I might go a little bigger than 1.5" diameter if I can get away with it to get a little better spool and only have as much backpressure as is needed to keep the internal wastegate functioning... pending further testing.

falcongsr

pics https://honda-tech.com/zerothread?id=382227

Full-Race Geoff

sir, you are very incorrect by saying more boost doesnt require a bigger gate.

More boost most certianly does require a bigger gate. When the boost is higher, the turbine speed is higher, the compressor speed is higher and the amount of air leaving the engine is higher. YOu need to get rid of that air, and if the wastegate is small it cannot sufficiently do that.

BudaKai

Sounds like it was creating a vacuum and spooling the turbo with it. If a big exhaust will do this, Hmm. I wonder if you can regulate a turbo with out the use of a WG (like I was saying a week ago) by properly sizing a plate when the WG would be and running it a certain distance away from the outlet of the turbine to create a vacuum. This sounds very similar to the Bernoulli effect used to aircraft lift. Am I on the right track here? I know there's a few aerospace engineers here.


[Modified by tzsir, 10:28 AM 1/11/2003]