[TRDemon]

is it true that if a turbo wastegate is open the turbo still produce boost? if so how much so. For example i have a T28 turbo with a internal wastegate do u feel if the wastegate is constantly open do you feel it would still boost and if so how much?

 

[Flashmn]

wastegate limits the boost. if you didnt have a wastegate your turbo would keep spinning and eventually blow up.

 

[neil85AE86]

is it true that if a turbo wastegate is open the turbo still produce boost? if so how much so. For example i have a T28 turbo with a internal wastegate do u feel if the wastegate is constantly open do you feel it would still boost and if so how much?

Yes, this is true and is a good method to check for expected spike levels. Since internal wastegate ports are soo small they cannot possibly bypass all the exhaust gasses from hitting the turbine, 2 to 6 psi isn't unreasonable, but it will be proportionate RPM and you'll probably only noticed the maximum psi at full throttle in the upper rpm. How much boost yours will generate is hard to say cause every application reacts a littel differently.

Neil

 

[TRDemon]

ok thanks :thumbup:

 

[TRDemon]

but remember flashmn!! the turbo can only spin depending on the exhaust gases has been sent to the turbine. its not like the turbo spings on its own. and i dout my can push that much gases to hurt the turbo.
Its a Garret T28, these turbos are found on 1800cc - 2000cc engines and i'm using it on a 1600cc engine, you do the math!!

 

[Flashmn]

and i dout my can push that much gases to hurt the turbo.

You can overboost...

Its a Garret T28, these turbos are found on 1800cc - 2000cc engines and i'm using it on a 1600cc engine, you do the math!!

Well... it depends greatly on flow, not likely, but still possible.

However, its not so much as to avoid the turbine exploding, thats a worse case scenario, the wastegate is whats used to control the amount of boost your engine gets. for example, a wastegate would be more open on 1bar than 2bars, because the turbine speed would be less.
Having a closed wastegate will effectively kill your engine AND your turbine.

Since internal wastegate ports are soo small they cannot possibly bypass all the exhaust gasses from hitting the turbine

They're big enough, you could basically run your car wiht 0.0bar boost if you kept the wastegate fully open all the time, your turbine wouldnt really spool that well, because exhaust gasses have a way of taking the easy route out

 

[neil85AE86]

They're big enough,.....

Then explain to me why I can take a turbo from a 2.3L engine, bolt it up to a 1.6 4age on a custom manifold, wire the wastegate full open and still make 6 psi at 7000 RPM?

I assure you, their isn't a single mainstream production car with a wastegate big enough to flow all the gasses around the turbine from any modern 16valve 4cyl engine that has a decent design and a decent VE. It's pretty easy to figure out, these internal gates are 10 - 20 mm in diameter, once that puny little route has been overwhelmed the remaining gas is going to take the next easiest path of least resistance ....through the turbine. Not only are internal gates small they are not placed with flow efficiency as the primary deisgn consideration, packaging usually wins.

If you are still not convinced ...put a 10-20 mm orificed restriction on your exhaust and tell me how well your car runs.

Neil

 

[Flashmn]

35mm wastegate....

Almost as big as the turbine outlet diameter...

relatively big...

Notice how the wasteagate has basically straight access to the downpipe?. Anyways each to their own, I'm not gonna argue about this.

 

[neil85AE86]

I'm not arguing just stating the facts, notice that the last photo was taken at an angle, if it was straight on I guarantee you'd see the turbine straight on and the wastegate port would be cut off, not one of those wastegates actually points straight out, pipe is round..not oval, and not too many standard style dump-pipes come anything close to giving optimum flow to the wastegate port over the turbine, for packaging or routing reasons. Take a look at the top photo, the actual wastegate port is only ~50% the size of the flapper door, which is typical, you can't judge the size of the wastegate by the size of the flapper, I guarantee not one of those ports is close to 35mm. The largest I've seen was a custom one off designed by IHI and it was 25mm, unfortunately this didn't leave enough material around the seat for a decent seal. I'm sure someone has done 35mm internal custom or on a big truck unit but I doubt a car sized unit would work very well without a special turbine housing. Their is a reason why 35mm wastegates are an expensive external option. My current setup has an 8 psi actuator, and actually runs up to 12 psi due to spike thanks to my latest free flowing exhaust system. I designed the dump pipe for decent flow, but the 12mm port just doesn't cut it. If an engine generates enough exhaust gases to make 8 psi at 3000 rpm and fully open the wastegate, how much additional gas is trying to be pushed through that port at 7000 rpm?

Neil

 

[TRDemon]

Very good point Neil, well i guess i have an idea for my project, so what i could do is wire my wastegate open to start with since i don't want to use alot boost. then i'll use a pressure guage to help me control the boost going to the intake.

 

[Flashmn]

Why dont you just get an adjustable boost controller. Lot less ghetto than wiring the wastegate open.

 

[TRDemon]

flashmn thats money i don't have. so i'll have to do it some other way

 

[TRDemon]

so do you have any brighter ideas bud

 

[neil85AE86]

..

flashmn thats money i don't have. so i'll have to do it some other way

Adjustable boost controllers can only adjust the boost to levels equal to or above the stock actuator, the challenge is to first find a low psi actuator. Shouldn't be too hard for a Garret, but will probably cost $100 U.S. + unless you can luck out on a used one, some of the Chrysler T3 actuators are only 5 psi, but not sure if they'll work with your turbo.


Neil

 

[Flashmn]

flashmn thats money i don't have.

And you're planning to do a turbo conversion without sufficient funds? You're gonna have alot more moolah go to that than a boost controller and a external wastegate.

 

[DRaKeN]

Then explain to me why I can take a turbo from a 2.3L engine, bolt it up to a 1.6 4age on a custom manifold, wire the wastegate full open and still make 6 psi at 7000 RPM?

Neil

My question is: why would you want to wire the wastegate permanently open? Wouldnt this bypass a large amount of the exhaust gas away from the turbine and therfore, majorly defeat the purpose of having the turbo there in the first place? 6psi at 7000rpm on a 4age....thats kinda sad with a T28 turbo... :thumbdown

If its your intent to do this, why not just get a decent boost controller/ECU and get it to control the wastegate? This just makes more sense to me...

But since you dont have the funds, there is another solution, there are solenoids/actuators(with ECU's) from (I kid you not) diesel locomotives that do the same job, look similar, are of the same if not better construction, and are about 1/3 of the price of an aftermarket item. Trouble is finding one and a mechanic who knows whatthefarkitis, whatthefarkitdoes and wherethefarktoputit.........Not to mention one to fit, as the one I saw was on an RB20DET in a 240Z...NFI what kinda turbo it was tho..

Cheers
DRaKeN

 

[TRDemon]

thanks neil, but i have a way of getting things down

 

[TRDemon]

well i have a T28 turbo neil, what do think