IWG not giving me desired boost
 

The wastegate that came with my turbo was rated at around 7 psi.
However, the wastegate will open nowhere near that. It was opening around 21 psi. No matter how much I adjusted it, I brought it down to a minimum of 13 psi.
This is the turbo I have,
http://cgi.ebay.com/ebaymotors/T25-T...d=253266173196

So, I was wondering, does angling the wastegate slightly cause the wastegate to open at a much higher PSI then what it is rated. Here is how my wastegate was originally mounted.
https://www.miataturbo.net/attachmen...ine=1312620269

Then I switched to another wastegate and brought it down to lowest 11 psi but I only want to run around 8 psi. But this wastegate is too big and I can't move it anymore to angle it better.
https://www.miataturbo.net/attachmen...ine=1312620269

Do you suggest I try to buy the same wastegate that originally came with the turbo because maybe I bent the old one? Or what should I do?

Also, does having a 3" exhaust make any difference?

anyone?

It looks like in both pictures the rod is crooked going into the canister. That part needs to be a's straight as possible for it to function. Also, if that is the begi sgdp it has been known to boost creep slightly

Yeah, that should be straight as possible. Cocking it may be causing the spring to have more pressure on it, thus making it open at higher PSI. You can test it...take a regulator with a gauge and a barbed fitting on the exit end of the regulator. Obviously have an air compressor supplying air on the inlet side of the regulator. Connect a rubber hose from the exit side of the regulator to the actuator. Start at zero psi and increase the pressure of the regulator until the actuator rod moves and opens the wastegate. Now you will know roughly how many psi's it takes for your wastegate to open.

Would having a 3" exhaust change anything though? I can't think of any physics behind it that will cause it to change but I remember reading somewhere that it does.
Thanks guys for the help. I will go find a way to make it straight.

Probably, I noticed an extra 1.5psi after replacing my stock exhaust with a 2.5" system.

I'm, in the same boat because my wastegate actuator is supposedly set for 8-9psi but I'm seeing 12-13.5psi.

-That WG rod is crooked as fuck.
-Yes, a bigger exhaust makes a huge difference.
This is typical boost creep, port your turbine housing. Make sure the flapper doesn't hit the downpipe as it opens. If none of that works, you're going to have to make the exhaust/turbine less efficient. The best solution is an external wastegate but thats expensive.

I have a thread on the front page of this subsection talking about my issues with boost creep. May wanna do a search as well.

Thank Abe,
does anyone know if say I wanted to run at 7psi, do I want the cracking pressure to be at 7psi or the opened pressure at 7psi?

Cracking. My wastegate is for 7 psi and with a hand pump it barely starts to crack open at 7 psi. With the car actually running there is pressure pushing the flapper door open.

crooked wastegate is not the issue.

What do you think the issue is?

But aren't you having the problem of not being able to run at a lower PSI (around 8 PSI, even though your wastegate cracks around that PSI)? So, if I got a lower rated PSI wastegate (cracks at 3 PSI, opened around 7 PSI), wouldn't it end up being slightly higher.

For example, your wastegate is rated at 7-8 PSI, and actually runs at 10+ PSI,
so maybe a 3-4 PSI will actually run at 7-8PSI. lol

Your turbo and exhaust are still too efficient so you'd creep anyway.

Where is the signal line connected to?

Also make a new mount with some metal and a bench vice.

It is connected to a nipple after the throttle. I will be making a new mount if Brain confirms that the problem doesn't actually lies in the wastegate.

Err the signal that opens the wastegate. Where is that connected to?

I think it is due to your new exhaust and I reckon porting a channel toward/into the wastegate hole will fix it.

It needs to be connected to a source BEFORE throttle body. That is most the biggest issue. Also, crooked wastegate could definitely have negative effects on performance. Borg Warner says a max of 2 degrees from straight is allowable, although that is another brand

I dunno sounds like your wastegate is rated too high.



I've run worse than this:

https://www.miataturbo.net/attachmen...1&d=1312806521


It probably doesn't help you any, but it appears you could easily bend your bracket to point the can inward.

i dont see how this would be a problem... ive ran them both ways without issue... the upside to connecting the wastegate to manifold pressure instead of pre throttle body pressure is so you can compensate for a crappy low flowing intercooler that creates a pressure drop. making the wg open at a specified manifold pressure and not the higher pressure seen on the turbo side of a poor flowing ic.

just my $.02

Dude what.

All intercoolers create a pressure drop. Not "crappy low flowing" ones.

Okay so what happens when you're stepping on it at 30% throttle and 5k rpm and the turbo has spooled up however the wastegate is reading somewhat vac/low psi and is fully closed?

If you want to avoid the "poor flowing ic" connect the source right between the IC and the TB, not in the intake manifold.

first, fix your wastegate can. It is a problem and will continue to be a problem, regardless of how the rest of your drivetrain is setup. Make it straight.

Second, yes, your 3" exhaust can affect boost, *BUT*, it will only be due to boost creep, and if that was the problem, you'll probably only ever see creep beyond 5k+ rpms anyways. The only good solution to boost creep is to have your wastegate ported professionally. I tried having a wastegate ported by a machinist, he did a good job with what he did, but he didn't have a thorough understanding of what needed to be done, the problem was only marginally better afterwards, but still nowhere near fixed.

Third, wastegate signal needs to be sourced somewhere before the throttle body. It's not a BPV. Sourcing your wastegate after the TB is going to turn your throttle into an on/off switch instead of a smooth controllable throttle.

got it. I will fix the wastegate and get a signal before the throttle.
Thanks for the help everyone.

Well give it a try and then celebrate.

1. Okay, I know the function of the wastegate, but I dont understand how to control it. Does shortening or lengthening the rod increase and decrease the boost (PSI)? Or, does it just help with spool?
The wastegate I have, the cracking pressure around 10 PSI. Is there anyway I can get this wastegate to run at 7-8 PSI?

2. Lets say my wastegate is rated at 7 PSI from the factory, is there anything I can use/change to make the wastegate run any lower PSI, or would 7 PSI be the lowest PSI I can run at.

3. Can I shorten my rod by adjusting it all the way to the limit? And, would I shorten rod all the way and then mount it or should I mount the wastegate first and then adjust the rod?

4. Can a MBC be used to lower the PSI below what the wastegate is rated at?

Sorry if I don't make any sense.

Would buying this item below and running it with a MBC solve all my problems?
http://cgi.ebay.com/ebaymotors/T25-T...#ht_1910wt_793

https://www.miataturbo.net/attachmen...ine=1313238971
https://www.miataturbo.net/attachmen...ine=1313238971

What I have seen people do is cut the rod, thread it, and have an adjusting nut for longer or shorter settings.


https://www.miataturbo.net/attachmen...ine=1313244419

Picture is from this thread, diy adjustable wg

If you want more boost put some washers where the wastergate is bolted on, between the compressor and wg plate.

@Hustler , I have no idea what that is

@mazpr , Will shorter settings allow me to run at a lower boost (7PSI) if the wastegate is originally rated 10PSI from the factory? Should I use more preload?

Short rod, wastegate opens later. Long rod, wastegate opens quicker.

I doubt you will be able to get it below 7psi. I have my 7psi IWG rod set max length so I see 3-4 psi at 6k, which is all my shitty injectors can handle because I'm poor. There is no "spool".

God, I am so confused. When people use the term "short rod", does that mean to adjust the length shorter and then mount it,
or
does it mean mount the wastegate, adjust length of rod (now the hole of the rod won't reach the shaft that opens the wastegate), and then apply preload?

Changing the rod length changes the "pre-load" tension for the inital opening of the flapper and adjusts how far it opens. "Shorter" means it takes more exhaust pressure to open the flapper and makes more total boost depending upon the angle of the rod and how far you need to rotate the flapper. The lower the boost the further the flapper needs to open. Make it longer to run less pressure and to open sooner.
Make the rod longer.
You tell me.
Bolt the can then pull the rod to the eyelet on the flapper mechanism.
No.

Thanks Hustler

How do I make the rod longer? Do I mount the wastegate first and then adjust the length? But in this case, the rod won't fit on the eyelet on the flapper mechanism?

Or, should i just elongate the rod as far as possible, and then mount the wastegate?

If the wastegate I have cracks at 10 PSI, is there any way I can check that the wastegate will be at 7psi when i elongate the rod?

You unscrew the threaded coupler to adjust the length. This is all going to be trial and error at this point.

but if i adjust the threaded coupler, which will increase the length of rod, the hole on the rod won't fit on the eyelet on the flapper mechanism.
I know then if shortening the rod, I can apply preload, but if I lengthen the rod, how do I make it work?

There should be a lot of preload already. By loosening it there should be less preload.


Basically if you run it once without connecting the rod to the arm, your waste gate will be fully open the entire time, in other words you will have lots of lag and very little boost. Take it to redline and keep your eye on the gauge especially at higher rpms. If you overshoot the desired PSI by doing this experiment there is no hope of you ever getting your desired low boost out of the turbo u're running just by toying with that arm. On the other hand if you do hit lower than your desired psi, keep loosening the arm and eventually you'll get it although your low rpm psi might suffer.

So if I am understanding correctly, increasing the length of the rod will lower the pressure of the wastegate, but at the same time, it will increase lag.
Would it be better to get a more stiff wastegate, lower than 7-8 PSI (what i want) cracking pressure, and use a MBC to raise my boost to 7-8 PSI?
This way, I can have better spool at lower rpms and maintain 7-8 PSI.

I was looking at this wastegate
http://cgi.ebay.com/ebaymotors/T25-T...#ht_1910wt_793

Yes new wastegate would be the best solution

I read somewhere about a rule of thumb, such that if I wanted to run at a certain PSI (say 8), I should always get a wastegate that has a cracking pressure half of the desired PSI (4 in this case).
Can anyone confirm that this is true

Someone said that in a thread I posted. That only applies if you are using a boost controller to get to 8 psi.
So if you want 16 psi with a boost controller, you need AT LEAST an 8 psi actuator. That doesn't mean you can't use anything from 8-16.

I see, okay, so should I get a wastegate that has a Cracking pressure at 3 PSI; opens fully at 7 PSI
or should i get a wastegate that has a Cracking pressure is at 7 PSI; opens fully at 10 PSI?

I want to maintain 7-8 PSI and have good spool, less lag.

Cracking pressure? That's dependent on whether you're testing it with a hand pump or with the car actually in boost. If you want 7-8 pounds, get a 6 pound spring with a boost controller. It's what I'm using minus the boost controller. Boost controller helps spool/lag.

That was some reading. I like the diy adjustable wg idea. You really just need a lower rated wastegate around 4-5psi if you can nail that on that spot. Attach your boost controller assuming you can figure that out. Loosen it a good bit so it doesn't affect the wastegate at all.

Then go drive the car, make sure it's hitting the said 4-5psi just fine. Pull over somewhere, turn boost controller clockwise to adjust your psi. Turn it slightly though and repeat your test run. Do this pulling over and boost controller adjustment until you have your desired boost then leave it the hell alone. :)