a wastegate, either internal or external, allows excess pressure to vent off the exhaust side?
a BOV does the same thing but on the intake side, right?

the deltagate is an example of an external wastegate, where as my t25 has an internal wastegate. if it is set to "factory 11 psi"(thats what i was told it was) thats not the same as boost psi is it? and lastly, if so, where would a MBC go?

i do plan on buying the turbo bible, but you guys are it for now.
thanks for the patience and answers.
tim97rs

>a wastegate, either internal or external, allows excess
>pressure to vent off the exhaust side?
>a BOV does the same thing but on the intake side, right?
>
>the deltagate is an example of an external wastegate, where as
>my t25 has an internal wastegate. if it is set to "factory 11
>psi"(thats what i was told it was) thats not the same as boost
>psi is it? and lastly, if so, where would a MBC go?
>
>i do plan on buying the turbo bible, but you guys are it for
>now.
>thanks for the patience and answers.
>tim97rs

Yeah you really should buy a book first :)

Anyway, to try and explain it in beginners terms a wastegate is what controlls your boost. The exhaust comes out of the manifold and enters the turbo and as your RPMs get higher more exhaust comes out and your turbo will keep spinning faster and faster. A wastegate has a vacuum line plugged in and when it gets to (in your case) 11 psi then it will open up and instead of all the exhaust gas spinning the turbo, it will be directed elsewhere. This way the turbo won't keep spinning faster and you will stop building more boost.

A BOV is used because when you shift you let off the gas and your throttle body closes. When it closes all the excess air that was going into your engine now starts heading back to the turbo (which will cause damage!) and so the BOV opens up and lets out the excess pressure and none of the compressed air makes its way back into the turbo.

Ymm what else? Check out howstuffworks.com they explain it a lot better then me.

Tim you will have to mod your wastegate to make it boost lower. Either that or get a nice Tial external wastegate. I think I will end up getting the Tial one. It is only like 200ish and to put it on would only be a hundred or so. That will make the T25 spool soooo fast is would almost be scary. :)

in response to where the mbc goes, it is placed on the vacuum line that goes from the westgate to the intake manifold (or compressor housing, depending on how you have it set up). By being in between these two, what the MBC does is not let the westgate see any pressure build up until your desired psi setting is reached. when you reach your desired psi, the MBC will open, letting the westgate finally see boost and opening so as to release the excess pressure.
This is why you only use an MBC when you run more boost than the westgate is set for, so that it will not open and allow you to build up pressure to your desired psi.

Hope that helped.

Late.

So to make a long story short, a MBC will not lower the factory set boost level, only raise it. You will have to mod the actuator arm like he said above. What that will do is it will actually leave the wastegate flapper open a bit. It doesn't allow pressure to build up inside the turbo past your set point (5psi etc.)

Sucks that we have to do that but unless you want an external wastegate thats the only way to go.

I read somewhere how to mod it to like 5 psi. but cant remeber where. So could any of those that have done it tell me or if you know a website that explains it post it here.

Thanks,
Chris:thumbsup

What you do is cut the rod where it is straight, and thread it about an inch or so on either side. Then you get a long nut and put it back together, screwing both ends of the actuator arm into the nut. To lower boost you simply make the arm longer so it holds the flapper open. To raise boost do the opposite. You cannot raise the boost past the level that the actuator is set for though.

thanks I found the website I was thinking of and it was like you cut the arm then put these peices on. It was no help. But I understand it the way you explained it.

Thanks,
Chris:thumbsup

I think using a spring pushing the rod out would be a better idea then lengthening. I would think you would have some added lag by leaving the wastegate always at least a little open.

Does the wastegate make a farting noise when shifting at high boost?




99 GS OZ EDITION
MODS-
Hahns Stage 2 Turbo Kit
Apexi N1 Catback
Testpipe
Progress Sport Springs
Audio- Sony LCD entertainment stereo
Pioneer XM Radio
2 Alpine type R 12s
MTX-775 Watt Amp

Future Mods-
17in Rims
JSP Carbon Fiber Blade or Arospeed Carbo

Hmmmm I dont' think it makes a farting noise. But that would make me laugh. It would be like krusty the clown car :)

I read the spring mod thing and it does not make sense to me. I don't see how it can make the wastegate open any sooner than if the spring were off.

And I seriously don't think lag is a concern on a t-25. Maybe on some of the bigger turbos but not a t-25. I think RxR_Eclipse said he hit full boost at 3k rpms with the lengthening mod... (a confirmation would be appreciated :) )

I've read about both methods and think that the spring mod is more effective. I wish I had the link to it, but I lost it with the rest of my old bookmarks. It was on Gus' site.

I think it's a bit hard to explain, but I'll give it a stab. The way that the actuator works is boost comes into a chamber with a diapragm on the bottom. The actuator arm is attached to this diaphragm, and there is a spring pushing the diapragm toward the boost chamber. The amount of force that this spring pushes against the diaphragm dictates the amount of boost pressure is required to move the actuator arm.

In it's default state(car off/vaccumm/0 psi), the actuator arm holds the wastegate in the closed position. As the actuator arm moves, the wastegate opens.

If you lenghten the rod, essentially you are opening the wastegate. An open wastegate will divert exhaust energy that could be used to spool the turbo. As you build boost, pressure is applied to the actuator spring, pushing the arm, opening the wastegate MORE. The boost will stabalize at a lower psi than it would have without lenghening the rod, but it will do so slower than it would have if the wastegate was shut initially.

If you install a spring on the actuator arm, less force is required to depress the actuator's spring. The wastegate will be closed, therefore allowing all of the exhaust energy to be used to spool the turbo. As you build boost, pressure is applied to the actuator spring, pushing the arm, opening the wasetgate...PERIOD. The boost will stabalize at a lower psi than it would have without the "counter" spring, and it will do so quickly...because the wastegate was closed while you were initially building the boost.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

I get it now. So if I have an actuator that is set at 10 psi, does that mean that its a 10lb spring inside? so in order to achieve 5 psi I would need a 5lb. spring on the actuator arm??

Something like that.

Actually in Gus' writeup, the "counter" spring is somewhat adjustable. The mod looked real similar to the rod lenthening one, in so far as you cut the rod. But you're only cutting the rod to be able to thread the section closest to the actuator. Install the spring, and hold it close to the actuator with a nut and washer. Piece the rod back together - but make sure it's the same length as it was to begin with. Then you can make the spring as tight or loose as you need it by adjusting the nut that's holding it against the actuator. Whatever tension gets you to your desired "minimum boost".


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

http://www.denverspeed.com/wastegates.html

is this similar to the mod?

yes

yep, thats the one.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

Yea I hit just a tad over 5lbs at 3k. But if my wastegate not modded up, I could easily hit 5lbs at 2200 rpm. You have to rember that the wastegate flapper is always open a little bit when you make the arm longer. That is why it spools slower with a modded arm. If I had the Tial external. Set @ 5Lbs I am sure it would spool up to 5lbs of boost at around 2200 rpm.