I don't think the spring will take the heat ? But if it was external with spring holding it closed then a diaphram connected to boost/ inlet that forces it open at say??? Above 6 Lb's boost or whatever suites your combo...Much like an internal wastegate....The door type gate seems the less restrictive....

 

subscribing. Very cool shit.

I can finally put the T70 on my lawnmower like I have wanted to do! j/k
This is an awesome idea I think.

 

lol, now that would be a sight haha.

I can see it now...all the huge diesel turbos on ebay that are super cheap start shooting up in price as more people do this. it'll be just like when the holsets were discovered by the masses

 

:withstu: :TW:

 

Wrong,
a Jake Brake opens the exhaust valve on the top of the compression stroke.

A normal compression stroke with no fuel (foot off gas pedal) compressses air, and that compressed air pushes the piston down again easily. That is why you can't slow down easily with a diesel by letting off of the gas pedal.

If you use the compression stroke to make a load, then bleed the load off at the top of the stroke, that energy (compressed air) is lost out the exhaust in the form of a loud pressure pop.


Braxton, that Aurora MST is cool. We are thinking this idea is new, they already have the idea in production!

 

:withstu: Subscribing.

 

I'm thinking this will work also! Why wouldn't it. As long as you get enough exhaust out of the incomming stream to the turbine, it should work.

Just block off one side of the tangeal housing, flow all your exhaust to one side, get 2 large ass wastegates to open to your desired PSI, and it seems like it would work.

Anyone disagree.

I mean, once the turbo spools up to it's desired RPM with little time, open big wastegates, release incoming exhaust, turbo holds it's rpms, and same amount of airflow is going into turbo, which would keep the same amount of airflo comming out of the turbo, engine is happy, turbo is happy.....??

 

Now that's a big HMMM....

 

i wonder about that from time to time.
get it going and then start to control.

 

It'll work.. kinda. thats the same thing as going to a smaller A/R housing and throwing a bigger gate on it. It'll spool faster but peak power will be less. This doesn't really have to do with the ability of exhaust to flow out the tailpipe, the huge wastegate will make sure of that, but more about the ammount of backpressure it will take to maintain boost.

For example, at 5000rpm and 15psi on a 351 cubic inch motor, lets say it takes 65hp to power the compressor. That horsepower comes from the exhaust molecules hitting the turbine wheel. If you go from a 1.0 A/R housing to a .50 A/R housing, keeping the same wheel, you're going to have to cram the same number of exhaust molecules through an area that is half as large as the original. Half the volume, same quantity, same temperature, equals twice the pressure. Eventually it will choke the motor.
I know its not this simple or linear, but for our purposes I think it works. Basically, that wastegate is going to hold closed until you hit peak boost, and as the power demands to run that compressor get higher and higher as RPMs increase, its going to take more and more exhaust going through that turbine.

Take it from the Supras - a huge friggin turbo will make great peak numbers. A medium sized turbo will have a decent spool time and still provide good power on the top end. A small turbo will provide super fast spool but suffer on the top end, and possibly cause damage to the engine up top.

Its as simple as this - sure the wastegate can flow enough to keep pressures down, but its just wasting energy to keep that compressor pumping.
Theoretical here - set up a wastegate to open up at a certain exhaust pressure. Put a large turbine on it, and see how much boost you can get it to make at redline. Do the same with a small turbine. I bet the big turbo will make more boost.

Now, a really good idea is the split turbine one. .5 A/R for spool time, 1.0 A/R for top end. Just gotta figure out a way to stick a valve in there to block flow to half the turbine during spool up.

 

edited........

 

This is one of those items someone has to actually try it rather than theorize about why it won't work.
I thought/said the idea of blocking off half of the turbine in a divided housing to decrease spool time was bullshit. Well in the real world it wasn't.

Duplox, I'm sorry, but I'm having a hard time following your post.
If you have too much backpressure from a small turbine housing, why not bleed it off with another wastegate set at the same boost level as the first one? Would you agree that the pre-turbine pressures would decrease with the addition of a second wastegate? Decreased pressure should translate into either more hp or an ability to raise your RPM, should the backpressure had been the cause of that.

I'm sure someone has to have tried it or has a better explanation as to why it will/won't work.

Maybe we need another thread started just on this.

 

COOL!

 

Heat riser valves would work. divide the incoming exhaust into 2 seperate legs, one leg for each side of the tangeal housing. Then put the heat riser valve on one side. Feed on one side uptil we get to our desired PSI.

Then we just have to figure out how to open the darn thing up when we get to the desired PSI. After that, let the wastegate take over.

Just a thought.

D Moss

 

I'm thinking, with a valve on one side of the tangeal housing, we can get the best of both worlds. quick spool up and enough exhaust gases on the turbine for upper RPM range boost requirements.

I can see small points from everyone's post that this seems to be the way to do this.

Hopefully within the next month or 2, I can have my project going and will have some concrete evidence of what I'm talking about, right now I'm just speaking my thoughts on what I think should happen.


Staying posted!

 

Yes that will work. Just using a smaller turbine housing(not a split) will not produce as much power as a larger one, regardless of how many wastegates are on it. A wastegate's control is boost pressure, not exhaust pressure, so it'll stay closed until boost is reached. Even if you have half the turbine area, you still need the same ammount of exhaust gas going through it to get a certain ammount of boost.

Anyways, for your project, the split turbine control thing, I've got an idea on how to control the secondary valve. I'd use something like the heat riser/EFE system plate, those seem to be about the right size. However I am concerned about durability at elevated temps, those things failed often on non turbo cars! However if you got everything coated I think it'd last a decent ammount of time.

Alright, back on topic. Use an internal wastegate actuator to control it. Hook the wastegate's inlet to boost, I'd use an MBC. Adjust it to open slightly before the wastegate, maybe .5psi lower. Set up your wastegate with an MBC(required on the wastegate!). If you don't have an MBC on the wastegate, your wastegate will be partially open at .5psi lower than the gate is set at, decreasing the effectiveness of the system.

Hopefully with this system the wastegate will stay closed until all exhaust is going thru both sides of the turbine. Then you'll gain an extra .5psi on the top end. You can then experiment in turning down the MBC on the wastegate to try to get the two as close as possible.

 

I have a detroit 70mm turbo 1.34 housing way to dam big for a 302 w/a f-cam. But given this info if I put a plate on it siince its a dual tang it will take it down to like .67 RIght?
If thats the case this guy saved me some grief of finding another housing

 

SUB

 

Do and take pics, post them here!!!

 

tossing out an idea for those who may be able to "run" with it..

for your valve use a slide valve in the blocked side of the split housing. carbon seals (similar to Apex seals on rotary motors) to seal from external leakage. the slide should seal rather well to the hole without internal seals. then when slid open there is no restriction in the path of the exhaust gasses.

oh and subscribing!!