A turbo logic session

[gmustangt]

Simply put what is spinning your turbo is pressurized exhaust, hot exhaust takes up more area than if it was cold, so there is more volume to it. When it gets to your turbo the velocity is dictated by the A/R of the hot side of the turbo, a smaller A/R is a smaller opening for it to get through before it gets to the turbine. A smaller A/R will yield a higher velocity hitting the tubine wheel but also create more pressure in the exhaust before the turbo.

This^. Which relates back to my previous comments...


-Seeing we have low exhaust energy at low RPM, would it not be benificial to increase our exhaust energy into the turbine via venturi effect...? Amplifying our energy more , instead of just using whats coming at it...

-Leverage is great if we have a large pressure differential, do we have this when we are trying to light the sucker and get it going?

-We only have X ammount of energy coming at our turbine, would it be better having X ammount of energy directed at a Heavier 60mm wheel (.64) or X ammount of energy at a Lighter 54mm wheel (.64)?

Forget about backpressure for this convo, there's ways to deal with that.

 

[Dartos]

So what is the downside of a variable vane turbo?

 

[Wheel House Motorsports]

So what is the downside of a variable vane turbo?

your stuck with aero's limitations for the mot part, i have yet to find a VGT turbo in rational sizing for a sled. and most are from diesel apps and have GIANT exshaust housings and weigh 30+#..

other then that i have wanted to try something VGT besides an aero forever.

 

[tree climber]

this is silly question but something i have always wondered about. has anybody ever tried a twin scroll with twin pipe setup?

 

[Wheel House Motorsports]

this is silly question but something i have always wondered about. has anybody ever tried a twin scroll with twin pipe setup?

I think the better option would be to retain the single pipe(and its inherant consistancy) and do a twin scroll with a "quick spool" valve as they are known, forces the charge through the tighter of the scrolls until a certain boost or back pressure has been met.

so many ideas, i could test and run all day if i had the time and money!

 

[tree climber]

pretty much be forced to run vipec with qsv to be able to fine tune exactly when to open the valve then.... if i win powerball i promise ill try them all haha

 

[Wheel House Motorsports]

pretty much be forced to run vipec with qsv to be able to fine tune exactly when to open the valve then.... if i win powerball i promise ill try them all haha

i can think of about 10 different ways to do it that cost maybe 1/20th of the price.. but whatever. like anything, more then one way to skin a cat!

 

[gmustangt]

i can think of about 10 different ways to do it that cost maybe 1/20th of the price..

Lets here them!

 

[smwizzz]

Awesome!!!

a set of reeds in the back of a air box will do the same trick. that's a old, old practice, I don't know if it got lost over the years or it just was not that effective. I have lost a lot of hair and gained a bunch of grey since then.



in non-scientific terms or conclusions. Through some testing it seems like the larger wheel is more effective. It takes more revolutions for the smaller wheel to push the same amount of air.

It can be very hard to believe when the bulk of kit builders say smaller gives you better spool up.

I was thinking barometric damper... until you suggested a set of reeds! You basically covered the barometric damper. They open on negative preasure and allow air intake on the engine intake side of the turbo and close on positive preasure when the turbo spools....

Sweet!!!

The rest of the info is awesome. Thanks peeps.

One question asked a couple times is the one about heat and preasure driving the turbo. Someone mentioned diferential.... It is hard to explain but the could it be explained in terms of diferential preasure caused by heat load? Static and dynamic preasures are different also and equate to total preasure. Kinetic and potential energy equate to static and dynamic preasure. The math and science are a difficult subject to explain in a forum. I think if we look at it in terms like: heat travels from high to low or hot to cold (lack of heat) and preasure is similar. High preasures will flow from high preasure to low preasure. Heat causes a high preasure due to rapid molecular motion and expands as heat is added. So... therefore we could say the engine is producing heat from products of combustion that are rapidly expanding as they leave the engine creating a high preasure on the engine side of the turbine. It is not this simple but for simplicity sake could this be a close analysis?

Just a thought.... I've discovered ways not to do stuff before....

 

[Wheel House Motorsports]

-We only have X ammount of energy coming at our turbine, would it be better having X ammount of energy directed at a Heavier 60mm wheel (.64) or X ammount of energy at a Lighter 54mm wheel (.64)?QUOTE]

obviously, if we run the same AR, the smaller of the two(reasonably) sized wheels will spool faster. BUT, now we run into the issue of restricted on top end.

SO, if we have two exhaust sides, both with damn near identical flow based on backpressure, one bigger wheel, tight housing, VS, smaller wheel, loose housing, I would choose the large wheel, ten to one. better venturi affect and leveraging against the bigger wheel. and with the large exhaust sides you usually get mated to a bigger framed compressor

 

[gmustangt]

What I'm getting at is of designed properly a 28 series .64 can work,and is one fast spooling son of a gun. And can make the power up top.
You don't have to sacrifice spool due to backpressure on the top end...
There is a 3lb/min difference beetween the 2 housings (64 vs 82).
There ARE ways to make up this 3lb difference... But things need to be designed properly...
I rode a .64 28 series all year and it is so torquey and fun!

 

[powderlites]

turbo logic

There is many things to consider when picking a turbo for your build.
What type of motor like 2 or 4 stroke and how it is built with port timing to cam timing etc.
Just with a turbo alone these are the things I want in a 2 stroke low boost turbo.
1=Thin light weight turbine wheel and shaft.
2=compressor wheel lightweight and most likely billet.
3=Lightweight bearings, Ceramic bearings as they can take way higher temps, out last steel 10 times, cage less so no melting of plastic cage and faster spooling.
No spacers in between bearings for less rotating mass and faster spooling, Bearings system that is loaded for no end play and no side play for tighter wheels in housings for more efficiency. lubricating bearings is a big deal on power loss and spin up.
4=A/R on housings plus waste gated or SS Tial type external waste gate or twin? SS lightweight and low .63 A/R I would pick for ultitmate turbine housing.
5= TRIM Too many guys over look what trim does on different types of motors or use of sled.
6=center section has to be water cooled and prefer lightweight Billet aluminum
7=Lube system or oil less and we are having great results with our own Oil less turbo system that we have built for us where bearings are used in Aerospace turbine motors.

This is some of the things I think about when picking the right turbo.

 

[die hard poo]

I was under the assumption that a .64 AR housing on a 28 series turbo on a 2 stroke was too tight causing too much back pressure on the pipe and potentially causing the exhaust side of the piston to get too hot. Not the case?

 

[Boyko]

What I'm getting at is of designed properly a 28 series .64 can work,and is one fast spooling son of a gun. And can make the power up top.
You don't have to sacrifice spool due to backpressure on the top end...
There is a 3lb/min difference beetween the 2 housings (64 vs 82).
There ARE ways to make up this 3lb difference... But things need to be designed properly...
I rode a .64 28 series all year and it is so torquey and fun!

So if there is a 3lb difference on the .64 how much exhaust pressure are you seeing at your boost level.

One thing you do not see much of is running a big A/R on the compressor side. The less restriction should help with the pre boost spool up. I ran a .70 A/R compressor housing with a 2.5" outlet for a bit this year on the cheap a$$ turbo project.

 

[gmustangt]

So if there is a 3lb difference on the .64 how much exhaust pressure are you seeing at your boost level.

One thing you do not see much of is running a big A/R on the compressor side. The less restriction should help with the pre boost spool up. I ran a .70 A/R compressor housing with a 2.5" outlet for a bit this year on the cheap a$$ turbo project.

I never got around to doing bp test, i knew i was gonna be getting rid of my machine and swapping my kit over to another machine, and i didnt feel like hacking my pipe, but i should have a spare pipe to play with next season.
Seat of the pants no difference of top end power being affected, no issues with motors nothing, couple of us guys are running these. I ran 6# all year and it ripped didnt need anymore. The .64 get you your shaft speed sooner seeing your boost sooner making it torquey and just a blast to ride.

But lets look at it like this, roughly a 15% difference beetween the 64 and 82. Now this is just the general concept...not the NASA version.

A. Lets put a divorced downpipe on it, wow great we can see a 5-10% reduction in backpressure because of the more efficient design.

B. Let port the gate, this is awesome we now have a gate which can pass more air- lets call that 5% more efficient at reducing BP.

C. Lets understand how the divorced functions , and the scavenging benifits as it will "pull" BP out, pretty slick. , lets add another 5% effiency for this... hey this is starting to add up.

D.The tighter housing is more effiecient at taking exhaust energy and turning it into boost pressure,it requires less drive pressure to give you your desired boost pressure with the smaller housing. Therefore your gate is gonna open at a lower BP to start with. The smaller housing requires less energy to be driven, aint that some backwards thinking. 5% here.

E. Holy chit, Here we have it 20-25% gained back from having the effecient PROPER designed system.

Well why dosent everyone run a divorced down pipe? - Time and cash money.
Lets look at silber kit, he now offers a new "formed" down pipe... Boston was saying they saw some minor gains with it... my bet is it was done becasue silber dosent wanna spend the time welding 100's of downpipes becasue he has better things to do id imagine...not saying whats wrong or right, just saying...
Now someone smarter than me explain how boondockers post turbine setup has any sort of flow thought involved... , well ya your gonna need an .82 with that design...

If a guy wants to run the compressor 4" inlet and 2.5" outlet (30 series), garret has an option for that and can go on your 28 series. you do not need to run a 3071 on your 800cc 2 stroke, not saying it dosent work but its not needed.

Alot of this stuff i have learned from Dave at Powderlites, he is one smart guy who knows his stuff, hes been playing with this stuff longer than ive been alive.
Thats why I run Powderlites stuff!

 

[jeepin270]

To good to be at the bottom