legacycentral bbs

hello i just have a few qiuck questions, any answers would be helpfull,
1, i have a 91 leg, turbo, all stock, how much boost is it running
2, where can i get the worlds cheapest boost gage
3 im intercooling it saturday, how many psi before fuel cut off
4, anyone ever made a manual boost controler,(home depot style)
is it possible?
5, any way to increase boost without a boost controller?

thanks in advance
rob

Most of your questions can be answered with a search, but I'll get you started.

1) If the boost control system is working right and the engine is healthy, it's making 8.7 psi assuming you're at sea level.

2) If all you want to measure is boost, something like McMaster part 4089K21 is about as cheap as it gets, at $8.32. Or if you have a PC-style laptop with a parallel port, you can build my scan tool, and it can show you the manifold pressure level read by the ECU if the ECU's not too busy to report it.

3) Fuel cut happens when you exceed about 13 psi for about 3 seconds.

4) Yes, I've made several, as have a few other board members.

5) I like the way I'm doing it right now. I strung a 40-cent tension spring from the hardware store between the end of the wastegate flapper rod arm and the wastegate actuator bracket.

thank you, thats all i needed to know

"granny butterin, not double slicin like you should, your lucky that 100 shot of rye didnt blow the welds on the bread lifters, now me and the mad scientist got to rip apart the crumb tray, and replace the lifter springs you fried" ROLF

I'm running the Home Depot Racing boost controller, no problem and the best 5 bucks I've spent. You might run into a problem with the cat in the DP limiting your boost mainly at high RPM.

could you give me a parts list for the depot mbc, or a pic, that would be great!

vrg3 wrote:

5) I like the way I'm doing it right now. I strung a 40-cent tension spring from the hardware store between the end of the wastegate flapper rod arm and the wastegate actuator bracket.

as i am new to turbo this intrigues me. especially the .40 part. please tell me more. is it reliable? safe? this would definatley need a boost gauge i would assume?

Lol, he just drilled a hole in the waste gate actuator bracket and ran a sping to the wastegate flapper arm. This will hold the wastegate shut until the boost is high enough to open the wastegate. I haven't seen or talked to Vikash in a few weeks, so I don't know how it works. It seems like a good idea, and probably does OK dealing with lag.

The only downside I can see to this is the potential problem of overboosting when lift throttle. The wastegate snaps shut so quickly because of the spring, that I would imagine a boost spike when off-throttle. The Diverter valve SHOULD handle this excess (if the throttle is closed) but as at least I know, the factory BOV doesn't always work. But I'm sure it's not a big deal, he is using a much more reliable BOV than we are.

I swear I think my BOV was a freak accident.

That is funny because I'm doing the same thing but the other way. My wastgate won't hold the boost I'm running so I had to use a spring to help hold it shut.

For a bleeder valve all you need is a small brass valve and some barb fittings.

Phil - Nah, nothing that fancy. I just strung the spring over. No drilling or anything.

What you're thinking of is the other idea I had -- I wanted to make it adjustable, so I was going to drill a hole in the bracket and put an eye bolt through it. The spring would go from the flapper arm to the eye bolt, and you could vary spring tension by adjusting a nut on the other side of the eye bolt.

This setup is pretty good in terms of lag... I mean, until the force on the diaphragm of the actuator exceeds the pretension of the spring, the wastegate won't open at all. It's really a lot like a ball-and-spring valve.

Most good boost control mechanisms shut the wastegate during shifts anyway... That's how you combat lag, and that's what the BOV is there for.

But yeah, I'm using a 1st-generation DSM blowoff valve.

We used a stock Legacy Turbo BOV on my brother's turbocharged Supra for a while and it worked well though... and he was pushing a lot more air than most of us are.

-K- - You and I are doing the same thing, except that you're using a combo of the spring and an MBC instead of just the spring.

Rob - For a bleeder valve, you can do like -K- said... just barbs, a tee and a needle valve... Thread the needle valve into one side of the tee, and put barbs on the two other sides.

For a ball-and-spring valve, you basically need a tee, barbs for two sides, a ball bearing that sits neatly inside the barb, a spring that neatly holds the ball bearing but won't bow, and some way to hold a bolt and locknut to tension the spring. I've done that last part by soldering a nut to the end of the tee, or by actually retapping the FPT hole into a fine bolt thread.

Ahh so that is the method you used!

I think it was just my BOV that was at fault, to tell you the truth. Something went awry and it no longer could do it's duties.

what makes the 1st gen. DSM BOV better?

I dunno. People just say it's supposedly a good BOV that withstands a lot of boost... I don't think it's really all true. I ranted in another thread about how I don't believe the hype about BOVs leaking boost.

I just used the 1st-generation BOV because it mounts on a pipe that fits really neatly between the Saab intercooler and the compressor outlet.

Rob - For a bleeder valve, you can do like -K- said... just barbs, a tee and a needle valve... Thread the needle valve into one side of the tee, and put barbs on the two other sides.


ya lost me,

Okay, let's try this for an example.

You want a needle valve. Maybe part number 2203x4 here:
http://www.fittingsandadapters.com/comanneedval.html

Then you want a pipe tee. Like 23700x2 here:
http://www.fittingsandadapters.com/femalepipetee.html

And then you'll need two hose barbs. Like maybe MPT-4-2 here:
http://www.fittingsandadapters.com/malpiptap.html

So you'll thread the barbs and the needle valve into the tee (use Teflon tape or another appropriate thread sealant), and use some vacuum hose to connect one barb to the wastegate actuator and the other to the nipple by the compressor outlet. The more you open the valve, the more pressure you bleed off.

Depending on how the whole thing is set up, you may need or want to add a restriction on the compressor outlet side to make the bleed more effective.

now were on the same page, thanks for taking the time to look that stuff up for me.

vrg3. can you take a pic of the spring set up. what weight are you using and what boost are you seeing.

I feel like an idiot vrg3, no more posting when I'm tired. My wastegate would open from the pressure of the exhaust at high boost.

robsgotit, You are going to spend a little time finding the right pieces that will fit together. Sometimes the threads will be different, make sure it seals up right. I use a small butt connector as my restriction, just stick it up the hose towards the turbo when you cut the wastegate line. (make sure it's not loose)

after reading the parts list i realized that that is the same style setup u used to keep my factory bov from letting air out at idle,
when running atmospheric, i never thought to use the idea for a boost controller,

-K- - Yeah, but your spring basically makes the wastegate stronger. Just like mine.

Rob - You can see the spring in this picture:

http://www.graphics.cornell.edu/~v/pics ... legacy.jpg

I'll try to get a better picture though.

Sometime when your exhaust is cold, pull the wastegate arm by hand so you can get some idea how strong a spring needs to be to provide the ~6 psi factory boost level. Then just go to a hardware store and pick a tension spring that's about that hard to stretch. It's not an exact science.

You need to form a long hook in the end of the spring that goes around the flapper rod, so it stays in place. On the other end, the hook that's already there should work. You just kind of hook it over the bracket and it holds itself there.

When I first put the spring on, I got just one or two psi above stock. I increased it by cutting the spring shorter, forming a new hook by using the coils of the spring (just bend it 90 degrees and then cut it with a Dremel).

vrg3 wrote:
When I first put the spring on, I got just one or two psi above stock. I increased it by cutting the spring shorter, forming a new hook by using the coils of the spring (just bend it 90 degrees and then cut it with a Dremel).

and that is why a good boost gauge is needed.

looks good, i ordered the mcmaster boost gauge, so project legacy will be on!

oh by the way, how much boost are you running, and how many miles are on the motor?

Me? I'm running about 10ish psi. I have a Saab 15-channel intercooler and a no-name downpipe. The motor's a youngun, with only about 120,000 miles.

did you notice a big diffrence at 10psi, im pushin 140k you think ill be safe?

If your engine is healthy the age shouldn't matter. These engines are very long-lived. 140,000 miles isn't actually very old.

If you don't know the engine's history, though, I would first do stuff like flush out the cooling system thoroughly, use Sea Foam to clean the crankcase, injectors, and intake, do an oil change with a quality synthetic oil like Mobil 1, do a tuneup, perform a compression test, maybe replace the timing belt and water pump... stuff like that. You should have the engine in good running order before modifying it.

I noticed a big improvement in my car with its mods over stock. It's not gobsmackingly faster, but it's a good deal more peppy.

yeah i got the car from an older woman, she was the original owner, she bought at ruges subaru in ny, she said every service was done to it, it runs very well, minus a little 4th gear stumble at highway speeds, it got a 4eat, other than that its mint, i got it for 800$ its just a budget build up toy for me, ive got an 02 2.5 rs that consumes most of my money