After reading a bit, I have the following conclusions... comments and corrections from the gallary :smiley_12 are welcome.

1. I can have all the bolt on's I want, as long as boost does not go above 10 psi.
2. After 10 psi, I need a aftermarket computer.
3. I can program an aftermarket computer with the same maps as the OEM - up to 10psi. Beyond 10psi, I can run similarly conservative (rich) maps to protect the engine.
4. The stock turbos's with an aftermarket computer can provide power up to 14psi with no problems.
5. If your turbos go, the chances that they will 'take out' the engine are minimum.
6. If your engine goes, the chances that it will 'take out' your turbos (ejected seals) are pretty high.

 

1-3: FACT
4: FICTION, most people do not get years of turbo life at 14+ psi
5: FACT
6: Partial FACT, apex seals don't always go shooting through the exhaust ports...

 

Hey Guys - Nice thread. I'm trying to learn stuff like this, and I find this helpful. Now if I can only find my boost spike problem. My guess is there is a vacuum hose cracked or popped off somewhere, and I have to find it. Then I'll fight boost creep after that.

- JyRO

 

isn't the 1st statement false though, guys? You can't have a midpipe, along with all the other bolt-ons (dp, cb, intake, etc) and just limit your boost using a boost controller to 10 psi, and run all that safely can you? Wouldn't severe boost spike be your downfall? You still need an ecu upgrade. Please correct me if I don't know what I'm talking about... reason why I bring it up is because there was just a recent thread on this, and Ramy also mentioned something about it, if I remember correctly...

 

Actually, boost CREEP would be the problem - the WG would need porting if the entire exhaust system were open.

However, he did say that "if boost were kept to 10 psi." With a MP the boost wouldn't stay at 10.

 

4. Fact, but only if your fuel system is up to the task. And like Rynberg said, the turbos will not last as long. Turbos in an all-stock setup tend to last about 100k. At 14psi, it will be much less - how much less is hard to say.

Dave

 

What is it about +10 psi high-boost operation that shortens turbo life? Do the oil seals or bearings wear out faster?

 

The heat in the turbos increases due to increased pressure (Pv=nRT) and increased frictional losses in the flow. As well, unless you increase intercooling to compensate, the intake temperatures go up too. The higher you push, the more energy goes into heat and less goes into improving intake pressure - a situation of diminishing returns.

All this heat make the job of the bearings that much more difficult, which means they go to crap sooner.

Its basic turbocharger thermodynamics - if you want more detail, I recommend Corky Bell's book on turbocharging.

Dave

 

^^I 2nd the curiosity. Anyone? Nevermind... I posted after Dave

 

Thanks - I suppose it contributes to the problem if you've opened up the exhaust, since the turbos reach those destructive higher speeds/psi more quickly.

 

You are also flowing more air - it takes more air to create 14 PSI than 10 PSI, and more air = more work for the turbos. More work = more heat, perhaps higher RPM (turbo speed) = higher probability the turbo bearing oil film will fail once in a while = more wear = shorter life. I've also seen the turbine blades fail, perhaps due to fatigue from the higher heat cycles (though the most common blades to fail are the compressor ones as they are weaker - aluminum).

That's why there's more power - more air and fuel = more power (if done properly).

I can't think of any reason an opened or freed up exhaust would come into the turbo life calculation, as long as the wastegate can handle the extra gas flow it would allow, boost would be the same. It's boost and turbo RPM that are the major factors.

 

Turbos are designed to run at a certain RPM, basically. If you spin them beyond their design limit, you'll accelerate wear.

Generally, 10-12 PSI is a safe ballpark to stay in for long turbo life. Going to 14 psi, and you'll be looking at dramatically less turbo life.

Also, the 10psi rule (#1) isn't totally proven. Yes, if you stay around 10psi with light bolt-ons, the stock ECU will do just fine. I don't think anyone has really tried to stay at 10psi with a FULL range of bolt-ons (full exhaust, intake, intercooler). Keeping boost at 10psi will definitely require porting the wastegate along with some luck.

Dale

 

So this brings Q1...

Can a boost contoller hold the boost at 10 lbs with a full exhaust (academic question - as a full exhaust would drive me nutz)? Or is creep inevitable with a full exhaust even with a controller?

 

I've done it actually with 2 home made ball spring boost controllers, though I had to periodically adjust them due to air temps. Like lets say it was a nice warm 75 degree day my boost would hold 10psi just fine, later that night it cools down to about 60F i would get a boost spike of aournd 12-13psi, pop the hood open the valves a bit more and bingo I was back down to 10. I have yet to experience boost creep though. Actually as far as boost creep goes I remeber reading a thread along while back that a lot of people got boost creep during the really colder air temp days.

 

I think that depends on the catback used and the car (how efficient are the turbos?). My car had a down pipe, mid pipe, and HKS Superdragger cat back, and didn't have boost creep. It also has the Efiny "Y" pipe. Oh, and it was loud. Not obnoxious loud, just loud. Now it has a "super high flow" metallic cat, which appears to function the same as the mid pipe gas flow wise, but the noise has dropped about 3 dB. Now I can hear all the suspicious noises I don't want to.

Oh, and if you want to trash the turbos in short order, let an intake hose (after the turbos) come loose. They will overspin and take themselves out very quickly.

 

Almost...

My set up:

Mild Street port
M2 CAI
PFS IC
DP
MP
STOCK catback
STOCK ECU
Boost set @ 10 psi

^^ Been like that for about a year now (10k miles) I boost it all the time. Car is fine.

 

Montego, how do you control it to 10 psi? Do you ever drive in temps below 60F?

 

Another question as far as #1 goes: What if you have all those bolt ons, and then set the boost lower than 10psi? Would that help as far as reliability, or would it end up causing some kind of damage?

I'm really trying to learn with all this, thanks

 

most of the question is a fact.

 

Turbos fail because they have to spin at extremely high rpm to generate 14+ psi of boost (200,000 rpm?). The stock turbos only have a 270-deg bearing instead of a 360-deg bearing (which the CHRAs in the BNRs do).

Yes, you still have perfectly safe AFRs at 10 psi, even with ALL the bolt-ons, assuming your car is in good running order (good injectors, etc).

Most people get boost creep, a few don't. A restrictor plate or ported wastegate will take care of that problem.

 

1) Boost control is performed via profec B spec 2
2) of course. Coldest it get's around here is 40 F. I really do not have to worry about over boosting in cold weather. I set my warning level at 10.8 lbs which keeps me from boosting past that. Nice little feature on that sucker .