I have tried the search button several times and can't seem to come up with the answer I'm looking for.

I understand that the boost rises with mods on the TII. However this doesn't make a whole lot of sense to me. My understanding of how turbos work is that the boost will rise until a set point and then the wastegate will open and boost will stay at that point until the wastegate is closed (I know that the wastegate is actaully modulated, but for simplicity I'll say open/closed).

Now with that being the way things work why is it that on a stock TII if you do a better/more free exhaust, and more free flowing intake you get more boost? Is the stock setup so choked down that it cannot reach full boost? Is the wastegate not big enough to control boost? I would think that even with stock equipment boost should be solid and stay at the preset level (BTW what is the stock preset/factory boost level for a TII) once it has reached that level.

The only thing that I can figure out is that the stock components are limiting flow SO much that the factory boost seting cannot be reached, OR the wastegate is too small and cannot control the boost properly. BOTH of which seem a little wierd as you would think mazda could have done thier jobs a little better here.

Thanks in advance for any and all help.

Mike D

 

The wastegate is too small! Mazda designed it to work on the stock setup and a little above that. Production costs determine alot of what goes in these cars not what maybe would work the best.

And remember; peak efficiency for the turbo is not usually peak efficiency for the motor. There are very strict emission laws here and alot of sacrifices must be made to comply with them.

 

AHHH I see now...So is it a common deal to port the wastegate? I would think that would be one of the FIRST things to get done if you plan on runnig higher boost. Yet I don't see it alot in anyone's sig lines, or mod lists, etc.

 

Porting the wastegate does not add any performance to the car, it only prevents damage. It is also not the easiest thing to get at and do. Both of which are reasons some people just leave it alone. Another would be that they do not have the mods needed to reach those boost levels.

 

It's not really the level of boost I would be worried about but more the lack of control....Seems as though you can't take full advantage of your mods because you have to keep a strict eye on boost and not overboost.

Yea I can see what your saying too though that it is hard to get at and doesn't do anything really except help control the boost, and really if it will only climb to around 10psi with mods then really it is controlled, just not by the wastegate.

*edit*
Oh yea, if you were to port the wastegate on a stock car, what controls the boost? Does the car come with a stock bleeder type valve, or is there a solenoid that controls it? or is it just plugged right into a vaccum line and set to open at xpsi?

And what is the stock boost setting SUPPOSED to be? Isn't itl ike 6.5 psi or something??

Thanks for the help

 

Yeah, with my new exhaust, my gauge showed me boosting 11 pounds... Should I be trying to limit that? If so, how?

 

[quote]I hope you at least have a walbro

The only way to lower boost is to add restrictions along the airflow path, or port that baby wastegate! I ran 11-12 pounds for 2 or 3 months on just a walbro and my EGT said I wasn't running lean, but it's cutting it close. When I put on my TID I boosted 12 pounds in first lmao so I knew it was time to do something. Just give yourself a weekend to do this if it's your first time. It really isn't that complicated. There are a few write ups on porting the wastegate, but feel free to PM me if you have any questions

correct me if I'm wrong but I think on series 4 t2's it's 5.5 and on s5's it's 7.

 

Thanks man...Thanks exactly what I needed to know....Off with me to the search pages to find out how to port wastegate, and for info on boost controllers.....All this research and I don't even own one yet.

But I'm looking If anyone finds a nice S5 around Louisville Ky for around $3k lemme know.

 

hey...
I have the same concern.
I have a TII with all the BPU goodies ie, walboro, free flowing exaust, INtake
I boosted to 14 psi on one day and never tried it again, and this was i 3rd! In forth my engine would of blown. So i vowed never to boost like that again untill i get secondaries, some form of fuel management, boost managemnt, and id say an FMIC.
My prob with this **** other than the incredible cost, is i cant even really drive how i want cuz my boost level goes way too high. So untill i am able to spend some serious money, I really cant drive (RACE) how i want WHich really pisses me off
Anyways im in the same boat looking for ways to boost safely
So good luck my man

 

See this is why I would think that it would be one of the first upgrades I would do. I can't imagine not having control of boost. I think this would definately be one of the first mods to do on a car....reliable and solid boost is always better I think.

 

My next upgrade will be aboost controller and bigger injectors along with a FMIC. I just put my new exhaust on and along with the TID I made, I boosted over 16 psi yesterday in 3rd. I normally keep the car out of boost anyway, to save on gas and stuff, but I wanted to see what it would do. Like i said, I usually don't leet it get into boost, except at the track and I'm definetely going to chill out on it until i at LEAST get a boost controller.
Damn...

 

the 87-88 have a 5.5-6psi spring in the wastegate. so the WG doesn't open till it sees that amount of boost (which then forces the spring to open). in the 89-91 has the same spring. but also a bleeder boost controller that is controlled by the ECU to give 8psi.

 

If my understanding of a boost controller is right then mostlikely a boost controller will not limit boost, but can add boost. I am thinking that all a boost controller is, is a nice litlte bleeder valve so the wastegate doesn't "see" boost until later (i.e. you have 6 pounds of boost built but a boost controller would only let the wastegate "see" 4lbs)...If the wastegate is already maxed out then there is no way to lower boost back down until you have increased the flow through the wastegate...i.e. porting.

 

yeah you need to port the WG first before doing all these mods in my opinion

The reason i dident do it was i bought the car with the mods listed so now its up to me to port the WG which i have yet to find out how hard it may/may not be.

Anyways basically the way to do it is through edjucation and intelligence. Id say prioritise and figure out the best things to upgrade first for your goal in mind, or else youll end up like me and not be able to use your available power woithout the danger of blowing up your engine..
ehh life sucks

 

Actually I think it's pretty dayum cool you can't go WOT...although it would be WAY WAY cooler if it was a traction issue instead of a boost issue

 

are there alternatives to porting the stock wastegate? like can you buy a different bigger one? or is this too expensive?

 

yeah i thnk that would not be cost effective. The mod im pretty sure would be much cheaper to do than buying a new wastegate, also i think that porting the wastegate is all that is needed for a certain hp range like you know if your boosting to 14 psi and have only an free flowing exaust plus intake.
It would make more sense to upgrade the WG when your adding a lot more hp to your car


2kwik4u, yeah id be funny if i was telling you how not to stick with the stock tires cuz our cars put out so much power with these simple mods that i cant even keep traction on the highway when im racing someone...corse that sounds like itd be a mustang problem or somthing

 

maybe it's just me, but, if your WG can't keep up wouldn't you have mad boost creep??

are you guys seeing that amount of boost at 4k or 7k?

Craig

 

2kwik4u: I dont know why youre so hung up on this wastegate deal. You act like any problem with boost HAS to be directly related to the wastegate.

One thing that causes a turbo to spool is the pressure difference between the sides of the turbine. If you have a restrictive exhaust, youre not going to spool as fast and youll eventually get to a point where you cant get rid of exhaust gasses fast enough. This would cause you to reach a limit of boost. On my friends turbo Miata, we couldnt get more than 7psi at first simply because his stock exhaust couldnt get rid of the ehxuast gasses fast enough to allow anything higher.

Getting an open exhaust not only creates a larger pressure difference, but it also gives the ability to flow MUCH more exhaust....Hence, allowing you to boost more.




If you ever want to meet up sometime and talk about more stuff like this, let me know. Ill be more than happy to help you as much as I can.

 

Yea I understand that the open exhaust lets you boost more, but what gets me is that the factory set boost at 7.5lbs (S5) yet people can regulary hit 10-16psi....Telling me that the stock boost control is not working very well. Which leads me to see that there is a wastegate problem. The bigger exhaust leads to a greater pressure differential like you said and that leads to easier spool, and greater boost. BUT if the stock setting is 7.5lbs and you overboost regularly then something is nto working well.

When I started this thread I didn't know that the wastegate was undersized for the application. Ihave since been educated though.

 

I don't think you would go as far to say the wastegate is undersized for the application. It is more than sufficient for the stock application which Mazda intended it for. Once you go and change all of the stock equipment, you are on your own to compensate. This thread has been very informative.

 

OK thats true...Leaving everything stock the wastegate seems to do a good job of controlling boost....But who leaves there car stock

and yes I agree this has been a very informative thread

 

Like I said man...If you want to meet up some time and just talk RX's ( or just cars in general ) just lemme know and Id be more than happy to.

 

Thats cool man, I think I have met you before anyway...Your on louisvillestreets.com right?? I've been to a couple of those meets, well before I got banned anyway (btw I never did find out why I got banned), and I regularly race at the ky region SCCA events....I'm the guy that races the little red pickup truck...I'm sure you've seen me.....You got a red convert right??

 

Yes I was on LS ( keyword: WAS )

I was banned as well. Probably one of the first people to be banned from there. Havent been back since.

I remember the truck from the races but I dont believe Ive ever met you personally.

No, I dont own a red vert.