Dumb question, and I'm going to feel like an a$$ after you guys flame me, but what's an AST?

- JyRO

 

AST is an Air Separator Tank. It helps remove air bubbles from the cooling system. The stock plastic one tends to crack and break after a few years of the underhood high temps.

 

Thanks for clarifying. I should have made it clearer to leave the hoses to the solenoids in place, and unplug the electrical connector to the solenoids. That will leave them in an always-open state, which will result in an over-active wastegate that keeps boost lower.

Dave

 

I have highlighted in the picture below. Is the highlighted item the AST?

- JyRO

 

Yep, that's the AST.

Dave

 

Well before we go off on a tangent about this AST (which going off on a tangent is fine by me), I want to clarify a few things to/from you guys.

I'm not interested in blowing this car up. That's why I'm here asking. My cousin seemed excited to tell me how much boost the car was making, but did mention he hit fuel cut and it wasn't good.

What I want is this: as much hp as I can get with the current mods, but overmatched by reliability. Meaning, I know what I have is not going to beat everything out there, but I don't want to out run a stock Mustang only to have him pass me when I pull over to the side of the road with a blown engine.

That being said, in order for *ME* to do what I think is best for the turbo's and engine, I need your opinions. Knowing what you know from what I've told you about this engine, what kind of max psi is safe for these turbos on a very frequent basis of max psi?

And, if that psi is say, 11 psi, is 11 psi on the engine safe there too?

I need to have a target to achieve before I decide on what I may have to buy to achieve a certain target. Its like I need a clear target to aim at, before I take the safety off and put my finger on the trigger. Thanks.

- JyRO

 

Max safe boost for stock twins and reliable = 10psi, that's why engineers designed it that way.

 

dude, looks like your rear turbo doesn't have the intake attached??? don't drive like that...

 

i think he said its a older pic bro

 

JyRo,

Where are you located in Alabama??

If you are near Bham, I'll take a look at your car. Give you some pointers and such.

PHIL

 

First, know the engine has no "limit" for boost. What you want to throw at it is what it (may) take. Higher boost places higher demands on fuel, cooling, intercooling, and tuning, and mistakes will cause greater damage at higher boost levels. And just like any other power mods, higher boost = shorter engine life. So you have to choose a point that you can live with.

For stock turbos, running sequential with stock solenoids, upgraded fuel and ECU, I would go for 14-15psi to get a good balance of power and reliability. Everybody has a slightly different opinion for "best" non-stock boost level, but I shouldn't be far from the norm here.

Knowing what I know, I *suggest* the following upgrade steps. This may be too conservative, but it's grounded. To get to 14psi, I suggest these things:
1) Fix the boost control issue now. Don't pop your engine with another 17psi boost spike. Control it by unplugging the electrical connectors to the wastegate and precontrol solenoids (it will produce an ECU code but harmless). Leave the vacuum lines in place. Do maintenance and make sure the cooling, turbo control, etc systems are running solidly.

2) Install appropriate boost control. Adjusting the pills will be easy but is tedious and a litte tiresome, but it's nearly invisible from stock when done. Manual boost controllers are cheap, effective, and easy to adjust. Electronic boost control is the fanciest with the most bling, but arguably no better than the manual. Set it at 11psi and plug in the wg/pc solenoids again. 12psi is the limit of a stock ECU, but 11psi is ok if controlled well.

3) Upgrade fuel and ECU. To get safely in the 12-14psi range, more fuel and appropriate tuning is needed. You can research the breaking points of both systems using the forum search - I'm not an expert. I think intercooler upgrade is also important at this point.

4) At 14-15psi, the stock turbos are working hard but with reasonable efficiency. That means that while they could produce higher boost, going much above this point the output air gets hot enough that even with intercooling it results in too high of an intake temp. As well, the turbos and engine run a lot hotter and add a bunch more heat to an already oven-like engine bay. It's not a magic turning point - 14-17psi is run regularly on stock turbos, but 13-15psi is probably a reasonably streetable and reliable number.

For even better detail, read the "advice for newbies" thread by Jimlab in the FAQ. He treats this subject in better form than I ever could.

Dave

 

Hehehe. I had taken it apart to find this boost leak! I took the intake to the turbo off, the top torsion bar off (whatever you call it from tower to tower), and the Y-Pipe to IC pipe off, and found the problem. I took picture from then.

- JyRO

 

Phil,

I'd love to have somebody to look at it that knows a lot about them. I'm in the Montgomery area. If you're in for a road trip, let me know. You could help me figure out what to do to stop the over boosting.

- JyRO

 

Dave,

You're talking about this approximately 5,000 posts over my head. But I'm going to learn all that stuff you just talked about as fast as possible.

The one thing nobody caught that I asked is: Will putting the stock airbox back on make any difference. I figure if its more difficult to get air, then it will richen up a bit & should make it harder to achieve boost at that level. What do you guys think about putting the stock airbox back on?

- JyRO

 

Putting the stock airbox back on will reduce flow, and also reduce peak boost. It might not prevent the high spikes, but it will certainly help.

Dave

 

Dave, if I do your suggestion number 1 (unplugging ...) will the car be driveable? And how much boost will it make driving it in that condition? Thanks.

- Jason

 

It'll make 8psi and be very driveable without feeling a major loss of power.

Dave

 

Interesting ... I read that it takes 8 psi from the primary turbo before the secondary turbo will be operated. I suppose there will be no problem of the secondary turbo kicking in?

 

Nah, works fine when I did it.

Dave

 

JyRO, I'm not sure if I could come down there anytime soon.. But we get together here in Bham at least once a month. Check periodically on SE section of the forum.

You could also become part of CAMS and we'll have tech day at local mazda dealership every 3-4 months. You'll have free access to lifts and such.