legacycentral bbs

Ok i got an Saab900 intercooler (with plastic end tanks, some punk beat me out at 41.00 on an aluminum end tank version 1 hour to close..) I got 2 feet of 2.5 Silicone pipeing, Rallitek Turbo Intake, a heat shield, Joe P. MBC all on it's way to my house.. What am i missing..

Any fore-notes/problems/ tips anybody have before i have my car apart, and i'm back here asking what to do next..when you've all figured that all out..

Oh should i spring for a GFB BOV? i want the "tiiiiiissssssss" sound or can the stock unit do the same Blow off to atmosphere..or is that a big nono..heh.. OH! where do i want to mount the bov..after the turbo but before the intercooler, or after the intercooler but before the intake.. I really have no idea.

Oh at what point will i have consider a performance fuel pump, FCD..

I don't want to run 16psi.. i just want 9-11 or as high as i can go with out having to rethink my completely stock fuel system.

Thank you

David Carter

P.S What can do for electronics with our crappy MAF.. i want a Super AFC to control things for me..but i think it only deals with MAP..

David Carter wrote: ....some punk beat me out at 41.00 on an aluminum end tank version 1 hour to close..) ..

hahahahaha...... hmm.

http://www.bbs.legacycentral.org/viewtopic.php?t=2067

read the third post.

Just run 11 psi to stay away from the ecu cut off and that way your ecu will deal with the boost (instead of fooling it and having it run fuel maps for less boost than you are really running). Most bypass valves are mounted somewhere on the IC or before it.

[quote="David Carter"]Ok i got an Saab900 intercooler (with plastic end tanks, ...some punk beat me out at 41.00 on an aluminum end tank version 1 hour to close..) ]

LOL!! I think I'm the punk

David Carter wrote: or can the stock unit do the same Blow off to atmosphere..or is that a big nono..heh.. OH! ..

supper big no no. i did this because my intake pipe/bov return line busted off. anyways, the oem bov will leak if you try to run the car at 3k rpms and not boost. its kinda strange. and it sounds funny as well. bad part is, you are sucking infiltered air into the motor.

Yeah, you can't just run our stock blowoff valves to atmosphere because of the mass-air fuel system. On speed density (MAP-based) systems you can just put a filter over it and the engine will run fine.

If you position it right, the stock valve is actually loud enough to notice. Where it is stock, it's surrounded by plastic and on the underside of one of the hoses so its sound gets muffled. Mounted between the turbo and a metal intercooler, on the top of the hose, it's much louder. So's the turbo, by the way. I guess maybe the intercooler kind of acts as a resonating chamber for the sound.

Ok

Yeah, you can't just run our stock blowoff valves to atmosphere because of the mass-air fuel system. On speed density (MAP-based) systems you can just put a filter over it and the engine will run fine.

But a non stock blow off valve can? as i see in this pick:



I purchaced off of e-bay:



and i just was wondering if'd work.

And where does that hose from the nipple run?

David Carter

There are two potential problems with atmospheric blowoff valves:

- If they are vacuum-actuated (as opposed to being built as relief valves), then they are open at idle. So, the engine sucks air in through the valve. This air is unfiltered (so dirt can get in the engine) and unmetered (so a mass-flow engine computer won't know about it).

- Regardless of the type of valve, when the valve opens during a shift, it lets metered air escape. So, the engine computer is expecting a certain amount of air but the engine actually receives less.

The unfiltered part of the first problem is easily solved with a small air filter.

With the stock ECU, the first problem causes really bad running at idle due to unsteady airflow and incorrect mixtures and ruins the air/fuel ratio learning control (which affects running at all engine speeds). The second problem causes overly rich mixtures during a shift, potentially to the point of misfire.

The valve you have is vacuum-actuated; that's what the nipple is for. You connect that to the manifold.

Call me retarded (and I know I am) but I thought it was a lean mixture that leads to detonation.

Yes. "You can run rich all the time, but you can only run lean once."

But overly rich mixtures aren't good, either. They can clog up oxygen sensors and catalytic converters, cause backfires, cause misfires... And the mixture won't immediately come back to what it should be if there's too much fuel in the manifold.

Ah. . . okay. I've always been told "when in doubt, run a little rich"

Guess that answers my question as to why.

Yukonart wrote:Call me retarded (and I know I am) but I thought it was a lean mixture that leads to detonation.

Actually richening a mixture too much will increase flame front velocity to the point that you can cause detonation. The noise heard from an engine detonating is actually the a/f mixture burning so fast it's breaking the sound barrier.

I really wish I had a pic of it from an engine analyzer. I'll have to see if I can get a hold of a pic from one of my past instructors.

Well it actualy isn't burning when you get detonation. Burning is the flame or "heat" ignighting the fuel around it. It only takes a split second for that flame to travel all around the cylinder. Now detionation is an explosion, the shock wave from the explosion sets off the fuel around it. It moves much faster and is much more violent.
Makes me want to go blow up something

-K- wrote:Well it actualy isn't burning when you get detonation. Burning is the flame or "heat" ignighting the fuel around it. It only takes a split second for that flame to travel all around the cylinder. Now detionation is an explosion, the shock wave from the explosion sets off the fuel around it. It moves much faster and is much more violent.
Makes me want to go blow up something

Not sure I understand/agree with what you mean. Can you elaborate? Detonation is most definitely a super quick burn.

It is the shock wave setting off the fuel around it. It happens much faster than burning and this explosion is what is bad. I could light a chunk of C-4 with a match and it would just burn. Use a blasting cap and kaboom. That much energy released almost at once instead of a slow burn.

So. . . then lemme see if I understand, now. . .

A lean or rich mixture CAN cause detonation. . . for slightly different reasons. .

But can a lot of this also be attributed to timing? I would think that, in the case of running rich, not all the fuel is being burned in the cumbustion cycle, leaving some behind to detonate . . . but what's actually triggering that detonation?

Are we talking bleedover from the exhaust cycle to the intake cycle which triggers a secondary explosion that is largely uncontrolled and unutilized?

Pardon my ignorance in this matter. . . I've only recently started paying closer attention to detonation issues with the impending purchase of a turbocharged car.

David funny you should use the pic of my set up. I am using a vent to atmoshpere, but with the right spring pressure you do not get any venting at idle. My car idles perfect, and I have no backfires when I get off the throttle. One thing though is my leg is an auto so I'm not constantly haveing to hear that damn thing hiss.

I agree with you.....I think we're saying the same thing....just a terminology difference. It's definitely an explosion....an "uncontrolled burn/explosion" is a good way to put it.

What I was mentioning earlier, if you look at a pressure volume trace of a combustion cylce, your peak firing pressure will be through the roof and will be early, it will then fall down relatively quickly, but on the down side there will be a jagged/saw-toothed trace. This is the explosion actually extinguishing itself, and then reigniting.

I need to get a pic.....remind me to call tomorrow

I was not trying to disagree at all, just pointing out how an explosion is a little different than a burn. I just wanted to point out the shock wave thing. That is what makes the burn so fast.

Fernely wrote:David funny you should use the pic of my set up. I am using a vent to atmoshpere, but with the right spring pressure you do not get any venting at idle. My car idles perfect, and I have no backfires when I get off the throttle. One thing though is my leg is an auto so I'm not constantly haveing to hear that damn thing hiss.

Mine is also a slush box. i can add a spring to this model as well i just have to take it apart. i will tweak with it a bit, i'm not to worried about the rough idle as of yet, as my car already idles extreamly ruff at idle, which i'm learning is a common problem/err in these cars. and since there are 101 differnt ways people say they have a sure cure for low idle hick-ups no one can pin point the exzact reason why most peoples turbo subes do it..

k sera, sera

David Carter

David Carter wrote: i will tweak with it a bit, i'm not to worried about the rough idle as of yet, as my car already idles extreamly ruff at idle, which i'm learning is a common problem/err in these cars. and since there are 101 differnt ways people say they have a sure cure for low idle hick-ups no one can pin point the exzact reason why most peoples turbo subes do it..

On my car it was a vacuum leak: a wasted intake manifold gasket. I replaced both intake manifold gaskets and now the idle is rock solid.