When out tuning on Sunday, we got the boost VE map at least roughed in for highway speeds in 3rd 4th and 5th gears. Challenge was not running over cars ahead of us as we watched the AF ratio. It is still a long way from being tuned in any fine way, but preignition is gone in those gears for now.

The new thing I noticed is that the boost gauge is now running up to 12 lbs of boost. This is up 3 pounds from the high boost range before. Is this the result of better tuning, or is something going on with the waste gate? I don't know much about this. I know how it works, but there are books full of products to upgrade, and better control the boost on this particular turbo, which I have not investigated. The term "dialed in" certainly is appropriate, since all along the tuning process has been one of making minor changes here and there, and then tweaking the rest of the program to accomodate the new settings. It takes a long time, especially when you are running down relatively unexplored territory. I am pretty certain every turbo slant has different base linen factors. One size does not fit all.

What can you tell me about the waste gate and boost rate adjustments to it, and/or products or mods that will improve this? At one point I was going to cut the boost back from 9 to 7, and was told that a waste gate could not be adjusted in that maner. I have put a turnbuckle on the actuating rod which can set when it starts, but this will not limit the total boost, since all the way open is all the way open no matter what. I guess you can create more boost by holding the waste gate closed longer.

The waste gate pot has two sides. Only one is hooked up to anything right now. Am I right in my understanding that the large short tube that runs from the turbo housing to the waste gate pot opens it with positive pressure? There is a small vacuum line to it, that I never hooked up. What is that for, and how does it affect things? I expect anothersix will have some practical experience about this.

Is there a way to check the waste gate pot to see if it is going bad? Could I see if the other side of it holds a vacuum? Thanks in advance. I am starting to eat an entirely new elephant now.

I am game for buying any new products that will improve the control of the boost, as long as there is positive experience to recommend it. Thanks again. I would go on the internet and search this, but I have learned there is a lot of bad advice on the internet. Just being on the internet is no proof of knowledge, wisdom, or quality. You guys are still the gold standard at least to find a good starting point.

Sam

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sam sounds like your having fun, what fuel and timing are you running at 7/9 lbs of boost, i know a blower and turbo are different beast`s but just querist.

If it only sets where the boost starts, then if you start making more power or more efficiency (via tuneup), then it will likely build more ultimate boost. You might consider a deltagate from Turbonetics.

Lou

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Home of Slant6-powered fun machines since 1988

Sam, I've done a LOT of dyno tuning of turbo EFI cars (Subarus and Mitsus), so I might be able to help.

So if I understand correctly, you're running your turbo on wastegate boost only - i.e. there is a direct vac. hose connection between the turbo compressor outlet and the pressure side of the wastegate actuator. Your WGA has a 9psi can (nominal 9 psi, they can be all over the place).

If this is correct, and boost increases above the WGA's setpoint of 9 psi, assuming that there is not a problem with the WGA, you are seeing boost creep.

Ultimately this is caused by the WG not flowing enough exhaust around the turbine for the amount of exhaust flow you're seeing.

To solve it you can:
- live with it (just accept higher boost at high RPM and tune for it)
- Restrict the exhaust (bad)
- Port the wastegate passage in the exhaust housing to allow more flow (tricky)
- Install a larger exhaust housing and possibly wheel (which raises the boost threshold and requires more exhaust flow to hit target boost at a higher rpm)
- Install an external wastegate (best, but most expensive solution)


IF, (that's a big if) your problem is as I've described, no boost control device will cure it. Every method of boost control can only INCREASE boost from WG boost. The other vac. nipple on the can is the vent side - by selectively applying pressure to that port, you can increase boost by countering the boost pressure trying to open the can.


Here's a quick test:
- Remove the circlip or cotter pin from the WGA arm and disconnect the can allowing the arm to swing freely.
- Run up to max RPM and hold it to see if you reach your boost point anyway.

If you still get boost (maybe not max boost) your problem is boost creep. It's not 100%, but it's a good quick test.

I just read your post again, and here's some more info:

- the wastegate can is just a diaphragm actuator like a vac. advance can. Suck on the vac tube to test it (it won't move backwards but it won't leak either). They take many years to go bad.

- The vac hose should run from a pipe thread fitting (or swedged tube fitting) on the outlet of the compressor housing to the proximal (furthest from the arm) end of the wastegate can. The second connection on the wastegate can is to balance the diaphragm as i described above.

- you don't need any fancy boost control devices for your setup. You want LESS boost, not more. All of those devices are intended for squeezing more boost from the wastegate actuator. A turnbuckle won't help, in fact if you loosen it enough all it will do is make the boost come on slower.

- If your problem is boost creep, nothing will fix it except for the items i listed above.

Don't buy anything yet.

What seems like very small tuning changes can make big differences. You lean it a little, the extra heat makes more boost, more boost leans it some more and it finds a new balance point.

Stock GN actuators were supposed to be set at about 10 psi, they ran a solenoid valve to bleed off pressure to the actuator to get up to 13-14 psi running pressure. The ecm could hold the valve closed to control knock.
However, GN actuators do not have two hose nipples, they only have one on the pressure side. This is from an 86-87?

The other line you mention, is it coming off an angled tee in the hose between the turbine housing and the actuator? You should plug it or get rid of the tee altogether, there is a orifice in the tee that you do not need.

Those pressures do not mean that much since you are running an entirely different engine. You can adjust the waste gate down, just not very much. It still needs some tension on the gate.

Porting the wastegate is actually very easy. Just remove the turbine and elbow, take them apart. Be careful not to ding the turbine. There will be a carbon pattern where the wastegate puck was closing. It is not usually centered over the hole. Just use a socket or washer that is about .9" in diameter to scribe a new hole that is centered in the pattern to where the puck closes, not to the hole. Then grind it out and radius the inside a little. If you clean it first use prussian blue on the puck to locate where it lands.

This will probably be the biggest step to fixing this. Then run a straight hose from the turbine fitting to the actuator. You should be able to tighten the actuator some and get quicker spin up along with the boost setting you want. The boost will always move up in steps with gear changes as the load and heat soak increase, this is not usually enough to matter and is not what is normally called "boost creep". Boost creep is an unstable condition that the waste gate cannot control. Not enough flow and a weak spring are the usual culprits. Yes. weak spring.

Good luck!

Yes, sorry I'm used to dealing with ECU-controlled closed loop boost. If you're using a mechanical boost control you will always see differences with the same setting depending on air density, etc, etc.

However, you should still see consistent performance of the boost control - normally you wouldn't expect to get more boost with the same setting and an engine change since the WG is still bleeding at the same setpoint. As long as your boost is under control, it will not increase based on just tuning changes...

That's the definition of boost creep, BTW - boost that increases beyond the ability of the wastegate to control it.

Thanks for the GN info anothersix - I didn't realize that was the turbo he was using. Personally my first choice wouldn't be a 1980's design with a non-standard turbine flange but they are cheap.

Knowing Sam, I would think he might prefer a $300 deltagate from Turbonetics. Just guessing. It would be sure fire, adjustable, and isn't that expensive. Any problem with using that part?

Lou

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Home of Slant6-powered fun machines since 1988

Perfect solution. A little overkill, but it will work.

Thank you very much guys. I am headed out of town tomorrow for 4 days, and may or may not have access to internet. At some point I want to ask about a deltagate. How it works, how it is different, and how it is better. I would like to take this back up when I get back. Thanks again. I will try to look up deltagate on line if I have a computer available in Boston.

Sam

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The Deltagate will work without a doubt. They have different springs that you can change out for different adjustment ranges and engine setups. The only downside is cost and some plumbing. If you get one make sure you order the flanges you need too. There is some import junk being sold to the tuner crowd out there, so if you go external I would stick with a real Deltagate.

I would not even consider any sort of electronic BS. I am an advocate of EFI, but boost controllers are just tuner toys. One glitch on a full throttle run and the fancy, no quality control box of led's just blew up your engine. It's not like you are going drive around changing it on the fly without re-tuning the whole system, that seems to be a missed point in some circles. Must have been in a B movie?

A big upside of the Deltagate is a much better flowing system can be put together. You can get a flange to replace the exhaust/wastegate elbow you have. It will plug the current wastegate hole and you can weld up a nice big mandrel bend, maybe 2 3/4" or 3 " to go into a nice fat downpipe. Getting rid of the restrictions in the original outlet makes a very big difference. You can get as much boost and drop your exhaust pressure and temp in front of the turbo. Or make as much power with less boost and be more knock resistant.

Any changes you make will still affect the boost pressure, but you will be able to reset it easily. Just a muffler change can move it a couple of psi, the wastegate is only referenced to boost pressure, not exhaust pressure, temp,velocity or any of those factors on the compressor side. It is routine to reset the boost after making changes as part of the tuning process.

I have caught up with this thread on a friends computer here in Boston. I went on line and looked up the deltagate from Turbonetics. I have not found a plumbing diagram yet, but have found umpteen places that sell them and associated hardware to contol the boost.

It seems as if getting one with bigger flow, and then restricting the opening to increase the boost to the desired level is the way to go. I am trying to imagine the layout of this set up under the hood, and haven't gotten the picture so far. The way it is currently set up, the integral waste gate is very close to the TB, thus limiting the space available on the turbine side of the unit. Does the Delta gate go between the header and the turbo if this Deltagate is added? Does anybody have a photo of a setup that uses it? Does the turbo have to sit at a different angle, or be in another spot? Do I have to reconfigure the down pipe in some way? I don't think I have enough room to raise the turbo, or move it off to the sideways in either direction.

I think maybe the first trick is just to "gasket match" the port to the puck, so to speak as anothersix suggested. If this brings down the boost, then I can always bring it back up in the future with a mechanical means such as stiffer spring, or one of the signal blocking valves of some kind.

Anothersix, there were actually three tubes coming off the waste gate pot. There were the two that were on a T off of a common nipple. I blocked one of these off. YOu say just put a single tube in there and remove the T. That's easy enough. Does this see boost pressure. The third one is on the other side of the pot diaphram and is just hanging for now. I always thought this must have been a vacuum hookup, but didn't know for sure. It would be easy to hook it up to a vacuum source. If this were hooked up, it would assist in closing the waste gate when boost dropped off.

For the record, I am running this with no mufflers,which might account for higher than stock GN boost numbers. Are there any opinions about whether running 12 lbs of boost is OK with a slant that is stock, other than porting the head, and forged pistons?
I am going looking for a GN forum for ideas.

Sam

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