How-to: Increase Boost with Stock wastegate.

SON240sx Automotive
1

Hi,

While I was thinking about getting an adjustable wastegate to regulate boost, taking the same theory of the adjustable wastegate, and applying it to the stock one, I found a simple, cheap way to raise my stock boost.

How an adjustable wastegate works: Inside your wastegate actuator is a rubber bladder, as it fills up with air it increases it pushes on the wastegate arm, pushing the wastegate on the turbo open to allow air to flow around the turbo. With an adjustable one, you shorten the arm on the wastegate so that the arm pulls on the bladder increasing its size and causing the actuator bladder to need to fill up more before pushing on the arm.

How-to apply this: Remove the two (2) 10mm bolts holding the actuator mount to the turbo (you may need to remove some vacuum line to make it easier). Insert a washer inbetween the mount and the turbo (if you put it inbetween the bolt and the mount, it will do nothing!), hence making the arm pull on the bladder inside. Put the bolts back on. Go for a drive!

Washer:
http://forums.son240sx.ca/album_pic.php?pic_id=543

This washer shown above successully raised my boost 1 full psi. It is just a basic washer I found in my garage. If more washers are going to be used, a longer bolt may be needed. Also I do not know how much tension the stock wastegate bladder can take, so add more at your own discression.

Time taken: 10min (the bolts are in awkward places)
Cost: $0.00 (found everything in my garage)

`Nik

2

Awesome Info Nik… This gets a Sticky :smiley:

3

heh, good call … old trick there.

Here’s something else you can do, it’s called making your non-adjustable wastegate fully adjustable in under an afternoon’s time

http://www.club-s12.org/board/showthread.php?t=7559

No Ball and spring style MBC spiking

4

Hot Damn!
I’m going to try that custom one with the screws tommorow!

5

There is another way to increase boost on the stock wastegate. This is what I ran accross by accident, and I make no guarentees that it will work for everyones car…buuut it did raise my boost from stock of 8psi to 12.5 PSI!!! That is right…12.5 PSI

Anyway, this is what I did, and I cannot post pics as of yet, cause I dont have a web address but here it goes it is pretty simple.

There should be a vac line that runs directly to your wastegate. (Correct me if I am wrong on this one) but that line runs from just before the throttle body and monitors the amount of PSI running to the intake. At stock boost of 7 or so psi (depending on BPU) the wastegate will read 7psi and open up, thus stopping anymore boost pressure.

What I did was connect the line that is running to the wastegate to a T-offconnector. So picture the line running from before the intake to the T-off connector, then one side of the T-off connector going to NOTHING (OPEN AIR) and the other side connected to a line going to the wastegate. This gave me 12.5 PSI of boost, solid all the way to redline in every gear.

Again anyone may feel free to correct me if I am wrong but this is the explanation of what I THINK happens to increase boost pressure.

First I will basically explain what the wastegate does (in essence). It controls the exhaust air flowing around the turbine by use of a pressurized (air/spring) combo. At a certain air pressure the wastegate will open and let out a certain amount of exhaust gases (into your exhaust system, or downpipe). At this point, (where the wastegate opens) you will get no more boost.

Ok so with that being said…

The wastegate is supposed to be getting a 7PSI reading from the cold pipe (through the vac line), however if you let some of the air that is flowing through the vac line to the wastegate out, it will get a lower pressure than is actually being created. This will keep your wastegate closed for a longer time and thus enable you to build more boost. Again, the wastegate is supposed to be getting a reading from the cold pipe vac line, HOWEVER you can “let off” some of the air at a T-off connector, thereby reducing the supposed 7PSI in the vac line to something lower, like for eg. 4PSI. Thus the wastegate does not think it has reached 7PSI, and lets you build another 3PSI of boost. Because the air is moving at a high pressurized speed through the vac line, there should be a point at which there is enough air (even with some being blown off) to get a 7PSI reading to the wastegate. It is at this “fake” 7PSI setting that the wastegate opens and your max boost is reached. HOWEVER the fake 7PSI reading is ACTUALLY 12.5PSI with 5.5PSI being blown off at the T-off connector! THAT is how this $2 mod should work.

My warnings are this. I have BPU mods on an SR, I was using a long ass vac line (worse spool up time) and a Y connector for this mod. My boost was 12.5 PSI (on 2 boost gauges) for a few days, until I decided to change some stuff. I HAVE NO IDEA HOW THIS WILL REACT WITH YOUR CAR. I HAVE NO IDEA HOW MUCH BOOST YOU WILL GET FROM THIS. Read my explanation of how it builds pressure over and over until you feel safe doing this mod, or until you find something seriously wrong with it and if you DO find something seriously wrong then let me know so I dont blow up my engine or something. IT SHOULD WORK for at LEAST A FEW MORE PSI THAN STOCK, and I know it worked for me. In theory it makes sense to me, but maybe not to you. Do what you will, it is your car, experiment, and have fun, but I take NO responsibility for what happens to your car.

BTW 12.5psi is damn fast. :smiley:

l8ts…

6

Lol, oh man! yeah what you stated as your explaination is exactly whats happening, heres a short form:

the air is going to go the path of lesast resistance, which at low PSI is out the tee, but as more pressure increases only a certain amount of air is can escape the open tee, so the excess finally goes into the wastegate bladder and fills it up.

the possible problem: one of your vacuum lines goes to your FPR, if it is also getting the same signal as your wastegate even though thats not the pressure in the intake manifold, then you are going to mess up your air/fuel ratio.

other than that, shouldn’t be a problem i think.

and Mr200, correct me if i’m wrong but is the majority of the sr20 wastage arm not perfectly cylindrical but flat, making the adjustable arm kinda hard? I’ll take a look at mine later today, and your post is exactly the adjustable wastegate you can buy, and i was thinking about doing something similar with my stock one, but i dont have those tools so i came up with a simpler way, but good find.

###EDIT: just checked, the arm is cylindrical for 80% of its length.

7

Hopefully you were running the 12.5PSI on a metal head gasket and not the stock paper one.

8

run the open end of the tee into the intake before the turbo. All the air flowing through taht tube is making the car run rich.

9

I believe you could also connect the open end of the T to a length of tubing (sealed at the end with a clamp) and attach clamps to the tubing at various distances apart. By removing or opening up each clamp will get you a different amount of boost.

10

It would have to be a rediculusly long piece of tubing or really wide, 8-10psi is alot of pressure, it would fill that up pretty fast. Either way, you’d stillbe running rich, good idea though.

11

or have an adjustable flowing T valve and run that to the intake so you can still alter boost instead of constantly running 12.5PSI.

12

why dont you guys just buy the hks actuator.

nice and clean and simple.

no extra hoses with tons of clamps. or washers or anything.

drive on stock boost untill you can afford to get something that is actually designed to adjust boost.

as well the stock head gasket on the sr will take 12 psi with out any issue

GT

13

Oh man, the whole point of this sticky was to show a simple way that doesn’t cost anything to increase stock boost, insead of buying an aftermarket one.

14

seems inaccurate and i would not trust it.

thats all

GT

15

Greg, are you talking about adding the washers?

If so, its exactly the same theory as the adjustable one :?

If you mean Mr. Zero’s idea of the open tee, then i totally agree with you.

16

yea the hoses scare me.

GT

17

I am not saying that it is the most accurate thing, however I had 2 boost gauges hooked up and they both read 12.5 for a few days until I undid this setup.

Yes you will run rich, but that can be corrected in other ways. Like the topic said, cheap ways of increasing boost. This is by far the cheapest and most powerful way. And in “theory” it should be pretty constant because of the airflow through the tubes.

Neway, everyone does what they want with their car, just remember to have fun! :smiley:

l8ts

18

Couldn’t you also buy a Manual boost controller for like 100-150 bux?