Max boost on IHI...

Will a worn cam make it impossible to spool the turbo all the way up?

I have my wastegate disconnected and can't get more than 18 PSI out of my IHI. I have heard of people getting 25+ and blowing head gaskets this way. Well this is not the case for me. I have been daily driving without the wastegate hooked up since the beginning of last summer.

I have noticed that I can't always get 18 PSI also. It will shoot to 18 and hold under a load, but if I'm accelerating at WOT on flat ground, it will spike to 18 and sink down to around 15. My setup is mostly stock, mods in the signature.

I have checked my stock gauge's accuracy with my Autometer vac/boost gauge. It is right on the money. Also FIRM mode comes on right at 10 PSI like it should so I have every reason to believe my stock gauge is accurate.

Almost forgot! My timing is dead on, but my vac is a little low (17-18" at warm idle). No leaks anywhere, the entire top end has new gaskets on it. At 18 PSI I have not been getting any detonation (plugs look great, and no odd noises). I have ignition timing advanced 2* over stock, 12* BTDC.

I would think a worn cam would greatly influence turbo spool - but that's an opinion not backed by hard fact. Hopefully someone more knowledgeable will jump in on that subject.

It's my understanding that the IHI becomes veryinefficient at boosts above 18psi, and until your post I don't ever remember hearing about anyone running one above about 20psi tops. IMO the spike and drop thing could be wastgate creep, but I'm no expert.

Sounds to me like it's time for a hybrid and external wastegate!

I am wondering the same thing. Mine wont get above 10psi. The lobes are worn, but that may not be my only problem. I know the seals and or guides in the # 3 cylinder are shot too. I have to pull the plug and clean it out every so many miles.

mine seems to boost pretty good. check the video in my thread here

http://natomessageboard.com/ultimatebb.p...p=1#000013

A couple of issues in this thread.

First, I think you guys need to understand how boost control works. Both Pete and I have written pretty extensive write up on it, do a search.

Now, for the 18 psi limit, If you do not have ANY signal to the wastegate actuator, the boost will go to the moon, until the turbo frags, or until the puck is blown out of the way. Its that simple, the actuator holds the wastegate closed.

If you are getting 18 psi of boost, you are not bleeding enough of signal away from the wastegate actuator. What I learned a long time ago, was that Ford was pretty darned smart with these cars. They built a restriction into the tee on the turbo outlet, that wont let you bleed away any more signal than roughly 17-18 psi. Basically, the hose to the BCS could fail, and it wont overboost any more than 17 psi. If you have any kind of aftermarket boost control, the bleed orifice isnt sized right.

Now for the "wont go over 10 psi" issue. The wastegate actuator is set t o9 psi from the factory. To get any more boost than that, you must bleed signal away from it. In this case, the bleed is not working weather it be BCS, or aftermarket. The wastegate is seeing the rated pressure and opening up.

Spend some time searching on this, lots of info out there, and boost control should be the first thing you understand on a turbo car.

Bob Myers

I have the original cam with 190,000 miles and it is pretty worn out. I have not boosted over 18 psi with my IHI though. but It does not have a problem getting up there.

Originally posted by martin0660:


Now for the "wont go over 10 psi" issue. The wastegate actuator is set t o9 psi from the factory. To get any more boost than that, you must bleed signal away from it. In this case, the bleed is not working weather it be BCS, or aftermarket. The wastegate is seeing the rated pressure and opening up.


Bob Myers

I think I have a good idea on how it works, but then again I might not, since I am still new to turboing. I disconnected my gillis a week or two ago, and plugged the line with a bolt and clamp. I had nothing attached to the WGA still nothing over 10 or 11. Boost is somewhat slow to build, anyone think the waste gate is stuck open? When i get a chance I think I might put the car on the jack stands and crawl under it, have my brother apply a regulated 9 psi from our air compressor to the wga and see what happens. Then for chits and giggles I have a stronger spring I can throw in my gillis, but I dont think that will do any good.

Originally posted by charles88tc:
]I disconnected my gillis a week or two ago, and plugged the line with a bolt and clamp. I had nothing attached to the WGA still nothing over 10 or 11. Boost is somewhat slow to build, anyone think the waste gate is stuck open? When i get a chance I think I might put the car on the jack stands and crawl under it, have my brother apply a regulated 9 psi from our air compressor to the wga and see what happens. Then for chits and giggles I have a stronger spring I can throw in my gillis, but I dont think that will do any good.

If you truely had nothing attached to the waste gate actuator, and it only built 10 psi, either the actuator is hung open, or the puck fell off.

As you suggest, it owuld be a good idea to test with an air source, just be sure you can regulate it low enough.

Bob Myers

I know that 18+ PSI is pushing the efficiency level, however I am getting away with it and I do feel a difference from having less than 18 PSI.

As for spinning into oblivion, I have NOTHING hooked up to the wastegate! I have all of the ports capped. My turbo has not spun into oblivion. What could cause this?

bhazard, I noticed on your video that yours stays at 18 firm. This is what mine does NOT do but I would like it to. Maybe I'll try a Gillis, but I think there is some other problem.

Maybe the spring in my wastegate is too weak to hold the flapper door shut completely?

I dont want to sound stupid, but I dont know, so I have to ask what is the puck? Is it where the WGA rod hooks to?