why so much boost?

[stizkidz]

I am still trying to learn about how boost can be controlled manually on our cars. I read yesterday that the stock wastegate has a spring set to around 15 psi. I know for a fact that the wastegate on my car is stock and un-modified. However, my aftermarket mechanical boost gauge is showing that my boost can peak at 20 psi! How is this possible? I have an old Pitbull chip. Could this be the cause? If so, what are my options for turning down the boost and still maintaining some performance gains from an aftermarket chip? I want to run approximately 16 psi max on 93 octane gas with the mods I have listed on my car below. Note: A hotwired Walbro pump and adjustable fpr is on hand and will be installed this spring!

Is there any way to rebuild my wastegate (new diaphram) so I can make mine adjustable or is it just easier to buy an adjustable one from Kirban's?

[Keller]

Every change to exhaust and airflow can affect boost.

- Your exhust is flows better, and may affect boost.
- Your air intake is flows better, and may affect boost.
- Your MAF flows better, and may affect boost.

Not to mention your chip is likely asking your wastegate solenoid to command more boost as well.

The spring in the wastegate is only a small part of the equation. That can be helped by cutting the rod to the wastegate and making it adjustable per the instructions on the website. Or, you could get an adjustable one, which saves you the trouble. Or get and add-on adjustment device. No matter what, every air/exhaust change you have made has been part of the reason for the things you are seeing.

[Ormand]

As you noted originally, stizkidz, the stock CONTROL is by the wastegate actuator, and the spring/diaphragm. The air pressure at the turbo discharge is routed to the diaphragm, and should open the wastegate, starting at about 5 or 6 pounds, and reaching full open at around 15 pounds. But the ECM can bleed off some pressure, using the wastegate solenoid, to INCREASE boost- no way to decrease it, only increase it. Or, you can use an aquarium valve to put a controlled leak in the air line to the diaphragm, to increase boost. Or you can use a pressure control valve, like those sold by some vendors, to control the pressure going to the diaphragm.
So, basically, you need to make the stock actuator adjustable, so that you can change the base setting. Then, if you want, you can use any of the above mentioned methods, or a combination, to increase the boost above that base setting.

[stizkidz]

Would it make more sense to use an adjustable wastegate or to use a vacuum line style bleeder valve? What are some pros and cons to using each method?

[Keller]

If you read Ormand's message carefully, an adjustable wastegate is the only way to get your boost to decrease. That is via achieving less tension in the wastegate actuator spring. The other types of devices can only increase and control boost. Both can be used together, but the adjustable rod for decreasing the spring tension will let you bring the curve down.

That, and getting the chip to do it to some extent, of course.

[stizkidz]

What is the max level of boost that can be set using only an adjustable wastegate (not a high pressure wastegate)? I am now understanding that if I set my wastegate to 15psi, then I will not be able to reach anything over 15psi unless the chip tells the solenoid to increase boost? If this is so, then it seems like all I really have to do in my situation is get a different chip????

[Keller]

Hmmm...

With the stock wastegate, and a relatively stock car, using a stock chip or one with the stock chip's boost scalars, you should get ~15 PSI.

In theory, the chip could be modified to get the boost down to ~10 PSI by direction all boost pressure to the wastegate.

With full stock wastegate tension, and chip modifications, you might get ~21 PSI +/- out of the stock wastegate in a fairly stock combo.

[Ormand]

The old "Pitbull" is not as good as many of the current generation of chips, so getting a new chips is a good thing, whether it solves the boost problems or not. But even with the Pitbull, if you just use a straight piece of hose, and run it from the turbo discharge to the wastegate actuator, then you will get only the boost that the actuator is set for. Or, you can just pull the hose off the boost solenoid, and plug it with a golf tee, or equal, it amounts to the same thing and is less work. That way, the solenoid may cycle, but it won't bleed off any pressure.

[NOTACARLO]

Depending on your current set up, you may want to add in the adjustability soon. 20 psi on pump gas can hurt things. Do you have any way of reading knock? I'm curious as to what you are seeing for knock at 20 psi. If you are not getting much, then I would say things are in the green.

Knock is the enemy, and alcohol is the iron fist. :six:

[NOTACARLO]

I just noticed your mods, get the boost lower.

[stizkidz]

If I am understanding this correctly: The ONLY way to ensure that the boost will max out at 15 psi is to run a stock wastegate and then either have 15 psi prigrammed into a chip OR use an adjustable vacuum boost controller and keep the valve closed????

It sounds like a temporary fix would be to simply plug the hose from the wastegate. Could I also just disconnect the wire to the wastegate solenoid to get a similar effect?
(Just to put everyone's mind at ease, I do NOT run this car at WOT and I have not allowed the car to make anything above 15 psi ever since I realized that it was making too much).

[Keller]

Running the stock wastegate is a good start. However, with mods on the car the boost will tend to be above stock due to better airflow and exhaust flow.

A chip programmed to 15 PSI is a good idea. Having the wastegate modified to be adjustable, or buying one that is already set up to be adjustable could allow you to do some fine tuning - up or down. Note that it is hard to program an exact boost level into a chip when you can't tell precisely how things will work in a given car. Its usually close, however.

An adjustable boost controller run fully closed will be just like stock. So what would be the point?

Not sure what hose you propose "plugging" from the wastegate. Providing no boost pressure to the wastegate would let your boost shoot up very high. If you really want to lower the boost, just skip the stock "Y" hose assembly and run a hose directly from the compressor to the wastegate solenoid. That should keep you at about 10 PSI. Plugging the "Y" up at the solenoid should be about the same.

Disconnecting the wire to the wastegate solenoid will provide you with a troble code.