RAD951

I am considering installing one of those wastegate blow off valves that install on the inake pipe rather than the exhaust. I will plug up the wastegate pipe and completely take out the factory wastegate. I will then fabricate on the intake boost tube, an adapter to install the B.O.V. I think its a better upgrade than a regular wastegate, because the turbo is always receiving the full potential of the exhaust and the boost is always there. But with an exhaust wastegate, to control the boost, you are limiting the exhaust gases, thus more turbo lag if more boost is needed. With the intake B.O.V. the boost has already built up at the turbo, but is managed at the intake pipe, thus less turbo lag. Has anyone done this, and how loud do you think its going to be? Kinda ricy, but whatever for performance.

Luke

with out a wastegate, you'll make 22psi and hit fuel cut.

You already have a recir. valve on an intake pipe ?!?!



BLow off valves are much different than wastegates

RAD951

I know I will hit overboost if I don't use a wastegate. Thats not what I am saying. I am talking about using a B.O.V. to control the boost instead of the wastegate. The B.O.V. I am talking about is not the black bosch recirculating unit you currently have in your 951 its different. The B.O.V. is the type japanese cars use like in toyota supras, or what greddy makes. They mount on the intake tubes and release air or boost, to control psi. I just have to find a spring for 13 psi for the B.O.V. and fabricate it on the boost tube.

CS Mende

Yikes! Correct me if I'm wrong guys, but I think the major problem you'll run into is the turbo over-revving. It's gonna be spinning ***** to the wall when you're on throttle because the pressure release device you're installing in the intake tubing is going to act like a big pressure leak.

The reason there is a wastegate is to SLOW the turbo down AND keep it from generating too much boost.

In your setup, the turbo is just gonna grenade itself eventually.

It's an interesting idea and is something that would probably work well -- and probably has -- if a turbo is sized exactly right to generate X PSI of boost where very little bleeding off is ever needed, and most of the duration is under part to full throttle.

~C

tazman

Don't forget you will also have to have a map sensor instead of the normal air flow meter or you will run rich.

Danno

"I am considering installing one of those wastegate blow off valves that install on the inake pipe rather than the exhaust."

Uhh, the compressor-bypass valve and wastegate serves two COMPLETELY different functions. The ONLY time the CBV comes into play is under closed-throttle states between shifts. Its only purpose is to keep the turbo-compressor spinning by venting the turbo's outlet back around to the inlet. The CBV (in bypass or blow-off mode) DOES NOT control boost, and it shouldn't be used to do so.

The wastegate on the other hand, operates under open/full-throttle conditions. It's a mechanical feedback circuit that opens the exhaust and bypasses gases around the turbo's turbine, when the intake boost-pressure hits a preset level.

So by removing the wastegate and monkeying around with the CBV to control boost, you're going to really shorten your turbo's life. It's going to be running full-steam ALL the time now. At 4000rpm, it'll hit its peak at 22-25psi with only 15psi making it into the engine and the rest being dump. However, the turbo will be spinning at 125k-rpm now instead of 80k-rpm like before to develop the same boost...

RAD951

I thought about that situation, but it will only be spinning real fast when I am on the gas real hard or running full boost. But, when i will be running less than 15 psi around town and on the high way, the turbo will run just like normal and spool up real fast when I would need it. I understand fully what you said because that is one of the draw backs of using this system. But now one runs on 15 psi all the time not more than a couple of seconds. I wouldn't recomend it to racers or auto x, because they are always redlining the motor and pushing it hard. But for a street enthuasiast like me that will only push the car once in a while past 4000 rpms to race some one, you will be fine I suppose. I just wonder about the sound it will make, but couldn't be louder than a wastegate. Plus, these B.O.V. do not cost that much compared to tial's $400 wastegate.

RAD951

Danno, I know what the CBV does, but there is a wastegate that think its called a "B.O.V. or Wastegate" that works with the same princeple of a CBV but backwards. Its what import cars have.

CS Mende

RAD951,

3000GTs, Supras, Eclipses, etc, all have wastegates and BOVs. They operate on the same principle as our cars do. Some have two turbos instead of one. Some wastegates are integral to the turbo and not external like ours.

Often they have, or are modified so that the BOV vents to the atmosphere -- adding somewhat to that WOOOSH sound you hear when they let off throttle... or two blocks away.

~C

Perry 951

RAD - you are kidding right?

In case you are not, spinning a turbo to 125k-130k rpm will explode a turbine or compressor wheel, not to mention burn up bearings. Running a turbo to it's mechanical limit is like you driving around in 1st gear on the highway. Turn 9000rpm in one of these motors (about their possible mechanical limit) and you will toss rods like it is your job.

The benefit you will gain will be minimal since it will still be just as laggy, if not more so, than having a wastegate limit boost, and a proper recirc/BOV. If the wastgate is working right and does not leak, the turbo will see all the exhaust anyway, just as much without one. Having a good BOV will keep the turbo spinning (and creating boost) while shifting, thus having reduced lag.

And if you want to run 25psi, you need a turbo that can do it without coming close to it's mechanical limit.

Peace.

Paul Bloomberg

Brian,
How is everything going with the rebuild?
Paul

Perry 951

<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=15&t=007551" target="_blank">The rebuild has been delayed. </a> But your turbo will work great!!

Danno

" But with an exhaust wastegate, to control the boost, you are limiting the exhaust gases, thus more turbo lag if more boost is needed. With the intake B.O.V. the boost has already built up at the turbo, but is managed at the intake pipe, thus less turbo lag. "

Hmm... almost. At low-rpm/low-boost/partial-throttle operation, the wastegate is completely closed. So from the exhaust gases & turbo's perspective, it doesn't even exist and 100% of the exhaust gets directed to the turbo. The issue that causes turbo-lag (boost-response when you floor the pedal), is the amount of exhaust gases present when you floor it. Regardless of the presence of a wastegate or not, there's just not enough exhaust to drive the turbo quickly.

If you are talking about boost-lag, or the shape of the boost curve without wastegate regulation, that's simply a relationship between the turbine and compressor sides of the turbo (housing & wheel sizes, AR ratios). There's nothing you can do externally to the system to change this (other than to make it worse). If you want max-boost to hit earlier, pick a smaller turbo and sacrifice high-RPM boost. If you want higher max-boost at higher-RPMs, pick a larger turbo and keep the revs up.

I guess the ultimate question is 'what result do you want'?

marksportcts

If you want faster boost response, what about the LBE? All turbocharged cars have wastegates, mostly internal and few like the 951's external.

Luke

No lagg you say? buy a DTA DFI system and dial in some anti lagg ROFLMAO