Can I install a wastegate in an odd location? Details inside

[Guest Magnum Rockwilder]

I have a Chevy V8 with a turbo.

 

It has a single turbo mounted on the passenger side manifold. There's no wastegate, so it's running full boost, which is 15psi peak.

 

I don't have room for a wastegate on the flange where all 8 cylinders combine, but I need to install a wastegate so I can drop the pressure.

 

Can I install an external wastegate on the exhaust crossover pipe that ducts the exhaust from the passenger side of the engine over to the turbo manifold? That way I wouldn't be bleeding off exhaust gas from all 8 cylinders... just 4.

 

Any formula I can use to decipher the size wastegate I need to drop boost from the current 12psi constant/15psi peak, down to 5psi?

 

Also, to install an intercooler and BOV, all I do is duct the intercooler in, and weld a flange for the BOV between the turbo and carb and hook up the vacuum lines, right?

 

Any idea what size intercooler I need?

[frank280zx]

I actually have seen it done to z31 before ( google external wastgate on l28, and you get a page on z31 i think)

 

It would work why not it is just a pressurized zone on both sides ( backpressurewhise )

 

 

 

 

http://www.z31.com/wastegate/

 

 

http://www.z31.com/wastegate/xover.jpg

[Scottie-GNZ]

This might be what you are looking for. Ignore the dump pipe if you are not using one.

 

[Guest Magnum Rockwilder]

This might be what you are looking for. Ignore the dump pipe if you are not using one.

 

 

That's exactly how I envisioned it, but do you think I'll be able to bleed off enough exhaust gas with only 4 out of 8 cylinders being relieved through the wastegate?

[technicalninja]

The wastegate will be venting all 8 cylinders as long as the cross over tube is not restrictive. You need to comput total flow expected and turbine discharge area to properly select a waste gate. I would expect you will need a fairly high flow unit.

 

Rick

[Guest Magnum Rockwilder]

That's what I was thinking, regarding the wastegate actually venting all 8 cyls.

 

Any formulas I can work with?

 

I really need a BC on this thing because it's cranking out 15psi right now, even with some kind of diaphragm restrictor on the intake pipe.

 

How do I find out what this turbo is? What all do I measure? All I know right now is the guy says it's an "RF40, because I ran an RF40 on my Yamaha FZR1000 and it looks identical to this one". He also mentioned "T04"

[Hugh]

I don't like that idea. You will be running uneven pressure from side to side. The turbine side of the motor would be performing more work, and probably seeing higher exhaust temps and back pressure than the open side.

 

How about running two small wastegates... maybe putting them on the front of each manifold? Many cars like GT-R's use dual wastegates.

 

You can use smaller ones, because you're only running it off 4 cylinders.

 

I'd just think its best to keep things balanced... and wastegating one side doesn't sound good to me. The internal turbulance in the manifold can make you lose 50-100hp if your manifold is bad enough.

 

For example, from a log style to a perfect equal length manifold on an SR20DET we just saw a 60hp increase with all other things remaining the same. Thats a 2.0liter with a turbulent manifold design... your results could differ. But 60hp is a lot to forget about in my book.

[auxilary]

rule of thumb is put it as close as possible to the turbo exhaust housing. you could do what this guy did:

 

and make it off the turbine housing itself takes skill tho

[Guest Magnum Rockwilder]

I don't have room anywhere on the manifolds. The only room I have is under the turbo where the crossover pipe bolts up to the turbo manifold. I may end up getting a turbo with a built in wastegate, but I'll probably try the wastegate on the crossover pipe first. The manifolds are pieces of crap from a 70's Massey-Ferguson tractor with a turbocharged Chevy V8. They weren't exactly designed with performance in mind. I'm going to run huge, wide open exhaust piping, but later when I win the lottery I'd like to make turbo headers to replace the log manifolds.

 

Maybe I could torch a hole in the exhaust housing and snake a pipe off it for a wastegate...?

[auxilary]

that would work, but remember that you want it somewhere near the collector, because you won't be alleviating much pressure if it's right next to one of the exhaust ports.

 

finding a big turbo for a v8 with an internal wg isn't easy - they're somewhat limited in selection

[baddriver]

I had a question, but in trying to phrase it intelligently, I accidentally answered it.

 

Later,

Jeff

[Scottie-GNZ]

If another turbo with an internal gate is an option, then look into some of the turbos used by the Buick turbo folks. It would require you to mod the turbo mounting on the header with a 3-bolt-unit but that should not be too difficult unless the manifold is made from some kind of "pig" iron that is difficult to weld. No problem finding one on the Buick boards that can support 500-600hp for a reasonable price. Of course, the trick with the internal gate is finding a wastegate cannister with a spring soft enough to keep the boost at 5psi. The GN stock spring is 12psi so that is out. Most that have a spring that soft are for small turbos so you have to mod the cannister bracket to fit a bigger turbo. I have extra brackets if you decide to go that route.

 

If the reason for running such low boost is to avoid detonation, then consider an alcohol injection unit. Again, fairly common in the Buick world and when you consider what you might have to spend for making the external wastegate setup or replacing the turbo, it might be a good option.

[Guest Magnum Rockwilder]

I'm going to run propane injection to combat detonation.

 

My reason for wanting to turn the boost down is the fact that the car will already be fast as shit all-motor, but my wife is dead set on having a turbo because she likes all the sounds and being able to say "I have a turbocharged V8". She'll be happy with a high 12 second car as long as it lopes, blows off, trills, and sounds like something from a science fiction movie. She wants a loud BOV, a loud gear drive, and lopey cam. I figure I can dial the boost down to 4-5 psi for her daily driving, and if she wants to go to the track and race in a safer environment we can crank it up. Also, she wants overdrive, so we're going to be running a near stock 200-4R and upgrading it bit by bit... or replacing it with a TH350 and Gear Vendor's OD when we win the lottery. If I send her out with full boost and a stock 2004r she'll come home via AAA.

 

I ran Desktop Dyno and found that with all of our planned modifications (heads, intake, carb, cam) and 15psi it would be some ridiculous number like 700hp. Neither her nor the car can handle that kind of power.

 

One thing I'm wondering about is the tuning:

 

do I need to run a single or dual plane manifold? I like both the RPM Air Gap and the Torker II on my N/A engines... will either of them be appropriate for the turbo engine?

 

Do I need to overcarb? How about a Proform 800cfm main body on a Holley DP?

 

How about the cam? I usually run a 244º @ .050 cam on my n/a motors, or sometimes a split 234º/244º for heavier cars, but I assume I need to run a smaller cam to allow the turbo to spool. Do I need to run a split duration? Any recommended cams for max power <6000rpm? How about a 224º/234º .465/.488 split with 1.6:1 rockers to add lift?

 

We're removing the engine from the donor car this weekend and installing it in the Z after Thanksgiving. We bought the donor car for $1100, and have already sold it for $1600 with a bone stock 350 from a Chevy Van! The guy is paying us to deliver it to Ohio next weekend!

 

Is there a message board where I can get familiar with turbo Chevies? I've looked and haven't found one.

 

Thanks for all your help!

[Hugh]

Maybe I could torch a hole in the exhaust housing and snake a pipe off it for a wastegate...?

 

Yes. Thats what was going on in the picture posted earlier.