Compound Turbo

[Toysrme]

muwahahahahaha!
Let's say if he dropped both turbos to 8psi & drove around. Then droppe dthem both to 4psi in a compound arrangement. He'd be in for a shocker LoL! I don't feel like doing the math. But it's be more akin to running like around 10-12psi the "normal" way instead of 8psi.

It's a big differance.

 

[V8Supra]

So its really double the volume at the same pressure? I thought the pressure was a factor of restriction, and the restriction would be the same (same intake/heads/valves/compression).

I can understand why bigger turbos push through a bigger volume at lower pressure, but I thought that was because the bigger turbine was creating less pressure on the engine.


Oh also. On a compound setup; the turbo sizing compared to a standard single turbo, would the turbos be smaller/same/bigger in size? ie. do you replace one medium sized one with two huge ones?

 

[Anaema]

it may also depend on how big the intake pipes are. if you have a 4" TB and intake pipes, with 1 BAR, you will have more airflow than if you used 3" pipes.

 

[KazeSupra]

If you're interested in a long, technical read on this subject, you might want to read this:

http://supraforums.com/forum/showthread.php?t=166688

Might have to have a username and password to view, but it's very extensive and technical as far as how things could work. I will warn you though, a lot of it is based on thoery and not 100% fact, as it hasn't been done thoroughly yet, but still a good read and still a lot of things to think about.

Chris.

 

[Toysrme]

1.689655172

It's not that technical, or complex to understand. I laugh when Supra guys can't give example end-result math, when I've seen the Saturn & Honda crowd do it before LoL!

Ok. Here goes an example for you guys. It will be a pair of T3 60 turbo's run in a normal parrallel configuraton VS a compound configuration. All turbo's set to boost 10psi above what the incoming boost is.
Air data will be taken from the current conditions here, Birmingham, Alabama @ the Birmingham International Airport (airport code - BIR):
647' above sea level
69.1 *F Current air temeprature
41 *F Dew point
30.31 in. Hg Altimiter Setting
The ambient absolute pressure is 29.61 in. Hg = 14.5psia (PSI - Absolute meaning what all pressure added together are.)
Alrighty. So we've got a pair of normal T3 60's blowing together in a traditional setup @ 10psi. That adds up to 14.5psia+10psia = 24.5psia. The Pressure Ratio increase is 1.689 bars of atmosphere, remember this for later! Now, that was achived by running the turbos out to 70% effeciancy (Because I like calculating at 70%... It's a good number to target stopping at.) By the time we run all that re-calculation:
We've got a charge temeprature of 219*F. It skews our numbers down to 23.98psia The relative density of the air when all was said & done increased 124.82%.

Whew! Now for compound charging the same setup! The calculations are done in step. First step & those results used to process the second step. So the same starting numbers. 10psi. The PSIA out of the first turbo is 24.5psia.
Now the second step takes that 24.5psia / 1.689 bar as a starting point! The second turbo is set to add *another* 10psi on top of that. This is where compound charging get's fun! The Pressure Ratio at the end of this process is has been multiplied up another 1.408 bars of atmosphere! (Because @ 24.5psia, 10psi = 1.408 bar, not another 1.689 bar.)
Coming into the engine, the charge is now 2.378 bars above normal!!!
The total PSIA entering the engine is now 44.91psia (30.41psig, i.e. boost gauge pressure compaired to ambient) not the 14.5+10+10 = 34.5psia (20psig)!!!! The relative air density has increased by 164.71%!!!!!!!! FnA!!!

I'm leaving out calculating afew psi loss (it's about 3 not major. It'd change the air density % to like 161-162% at worst) because it's a total bitch to take that high of a pressure & calculate it against the 411*F charge temp.
So you've got an air density of about 124% going against an air density of about 160%.

Now I'd like to point out something else... If you were to wastegate the second turbo to the same PR increase as the first turbo. It would be wastegated from 10psi, to some 16.898psi. Because remember. The first turbo's wastegate is going (14.5+10) / 14.5 = 1.689 PR rise
The *second* turbo is going (24.5+16.881psi) / 14.5 = 1.689 PR rise.

*So* if you run the second turbo up to equalize the amount of work the first turbo is doing. You wind up with 2.852 PR rise. (Really being 168% rise in air density, minus afew % for air temp ofcorse) Big big big with very very very little work!!!!!





Anyways... The end result being, that compaired to running parrallel charging, sequential charging will give another 40-60% pressure gain depending on how you want to set it up, which will result in an 30-40% power increase when compairing un-cooled engines. Now if you cool your charges down... It'll wind up being antoher 40-50%.





I hope that sheads some light on why compound charging rocks hard-core engines.

 

[robertk515]

im sorry i must have had a dumbass attack looking at the pictures, i KNOW for a fact that the system i set up uses one turbo to spin the other. the second turbo looks like it has 2 compressor housings, both in a lighter cast color and not dark like an exhaust housing. i am not sure of the company that makes this kit, but i did install it, DIRECT bolt-on replacement from the manifold back. i want to get some fuckin pictures but my fuckin moron friend will not send my digital camera cable back from my trip to oregon last summer!!!

what would this system be considered if not considered compound?? series turbocharging?

Toysrme, i am very impressed with your math, nice!!

 

[Zuffen]

Toys,

One question.

With a 411degrees F intake temp you will need to pull a lot of timing or run a damned good intercooling sytem.

Whilst the boost is serious what would you guestimate the final % gain in HP to be given the air temps?

 

[Toysrme]

Well, see that's the thing. I'm the kinda guy that failed Algerbra-II because I spent the entire semister playing with the hot girl in high-school. Unless you just need the numbers, don't make me do it LoL! Cause I've done the math in excel & I get lazy & don't feel like doing it by hand.

I still think I had my priorities straight tho. Oh My God was she !¡!gooooood¡!¡

But what you'll wind up with is awhole lot of power. Remember that was non-intercooled. In that example straight twins would have been 220*F.
If they both were intercooled it'd have dwindled down to around 110-130*F on a good cooler.
Same for intercooling after the first stage in the compound charge.

Say in the first compounding example (1.689 * 1.408): It'd have jumped up to 219*F, A descent intercooler would have dropped that to atleast 130*F, the second turbo would have jumped it back up to 271*F. And an indentical intercooler to the first would drop it all the way back down to around 157*F.
In the second example (1.689 * 1.689): it'd have been 130*F, up to 320*F & back down to 185*F.




That's why you see turbo + turbo, or turbo + roots blowers used on diesels, or some drag cars running methanol where it's not as big of an issue.
But at any rate. The charge temps wind up being lower than if you used a single turbo making the same pressure & flow rate @ the same thermal effeciancy.


Compaired to using the same setup & parrallel charging like normal. Just by re-routing the piping you'd gain another 30-40% ontop of what the previous woulda been. I guess the best thing I could tell you that you could relate to, would be if you re-routed a 300zx twin turbo. You'd wind up with like 340-350bhp instead of 300bhp. Or a 3000GT would make 360-375bhp from 320bhp.


It's worth about 30-40% using the same compressors @ the same base boost levels. If you take them & run the second compressor the same as the first, it's worth more like 40-50%+.

 

[Toysrme]

What I'm getting at, is that unless you have pistons (Like the mid 90's-00's that Toyota began to put into about everything. I'll leave that comment for someone that palys with the v8's more, but it's true for everything else out of Toyota in that time frame! <sniff>) that are high compression & have the ringlands too high, indentions too close to the edge of the piston & rings too high. It's not that big of a deal.
Aslong as I don't see the end charge temps in the 200*F range. I'm normally OK with a setup provided it's tuned well & the OEM pistons are not prone to breaking. See. You get all thse roots blowers & un-intercooled centerfugal engines running 200-230*F charge temps. I just don't like seeing those kinds of temps. When I put one together & tune it. I'll get all I can get out of it safely & then over-tune it so the damn thing runs forever LoL! I dont' care much for engines that blow up.



And they're always water injection. I've gotten to where I put WI on about anything I touch with a turbo. It's freaking cheap insurance. Lets you get by with "daily driver" levels of boost on low octane too. Great stuff! (And adding in a mister for any coolers you have -> nice!) If Frank Whalker, the father of water injection, could take a Pratt & Whitney R-2800 in the P47 from 2000bhp to 3800bhp over years of developement on water injection without ever blowing an engine. No knock sensors. No electronics. And a roof mounted compression blower so big it took minutes to spin up & spin down. If you ever got one too far, it was gone. The way I figure it, none of us have excuses for mistakes!

 

[striker]

hey all,

as said charge density enhancement is what's achieved buy compound charging,
unless you're using it the way scania does, they just put a gear on the turbineshaft instead of a blower, and drive it through a gearbox right down to the crank which gives them a healthy 80hp @ 1000rpm over stock with no extra fuel consumption or loss of boost from the first turbo whatsoever, that way the can scavange a lot of fuel consumption at a full weight pull-up. that was the goal and that's what they achieved.
they are in fact pulling 80hp from the turbine, or am I missing something in their set-up. the don't do a sort of ALS trick in the second one so....

so the Tigers project is really on to something here and the greencarcongress admits the 17kw powerclaim in the tiny hybrid diesel set up.

on a 1uzfe however I don't realy see the point in doing so, majoola has proven that a 0-200mph in 19seconds engine 900+rwhp can be build with a normal turbo perbank set-up can be achieved. which would make the plumbing a lot easier. especially in a front engined car.
personaly I think that a alloy blocked v8 at that boost will become a BOMB instead of an engine. and I wouldn't want to have that lurking 2 inches from my back at all (building midengined hey)

very nice to try, but no reason really unless your dragracing it.

also remember that the BMW Megatron F1 engines of yesteryear put out over 1400hp in qualifying trim on just 1500cc's without compound charging,

grtz Thomas

 

[robertk515]

those f1 engines spin one hell of a lot more rpm than any engine we use. and plus they are designed by masters of this game. with titanium-aluminum alloys that are super strong and really light in comparison to what "normal" production engines run. its comparing apples to oranges.

and qualifying trim on one of those engines is soo much because they are only running the "qualifying laps" thus, they do not have to make the engine last. normal engine horsepower in a race for those particular engines is between 600-900hp to save on engine durability so it can make it through the whole race.

 

[Anaema]

compound charging isnt a very weight effective way to plumb any V type engine. two turbos per bank is getting on the portly side of things. it would be great on say, an L4 or six, or a rotory engine. imagine a 20B with compound charging.....

 

[Pro]

the CAT truck racing series here in Australia uses compound turbo setups.

one truck actually has the BIG turbo feeding the SMALLER turbo - and he's the class leader so it must work effectively.

 

[Pro]

. imagine a 20B with compound charging.....

three turbos to produce roughly the same amount of power as a single turbo?

the weight and cost of the setup would outweigh any further benefits.

the trouble with the compound charging maths with rotors is, each rotor is (for lack of other comparison's sake) a 3cyl piston engine by itself, but working in unison with the other rotor(s).

you'd be compound charging a compound charge in case of a 13B, or compound charging a compounded charging of a compound charge in a 20B's case.

now, after reading that, who thinks the word "compound" looks funny...?:Eyecrazy:

it's the reason why triples fed by one exhaust port on 20Bs don't work as well as a single fed by three exhaust ports. pulse wave reflection timing on both the inlet and exhaust ports dictate power, not the amount of boost stuffed in or out of them. that's why you can make so much power in a rotor's exhaust, and lose so much at the same time.

 

[striker]

those f1 engines spin one hell of a lot more rpm than any engine we use. and plus they are designed by masters of this game. with titanium-aluminum alloys that are super strong and really light in comparison to what "normal" production engines run. its comparing apples to oranges.

and qualifying trim on one of those engines is soo much because they are only running the "qualifying laps" thus, they do not have to make the engine last. normal engine horsepower in a race for those particular engines is between 600-900hp to save on engine durability so it can make it through the whole race.

Well your not exactly right, (ger)BMW and (USA)megatron used stock!!! cast iron bmw2002 2.0L engine blocks which had drivven at least 100.000 road kilometers of the 1969era for the F1 turbo engines,
The internals we're custom because F1 regulations said <1500cc for turbo cars. crancks where steel and rods also. alloy heads with steel components for the valve train. so no fancy alloy's anywhere. exept for the bearings maybe...???

the 4 cylinder the quialifying trim had ONLY 11000rpm which was even in the 80's very low for 4 cylinders you can have a 1uzfe do that nowadays with off the shelf components.

the turbo's early kkk later garret, where operating at such an enourmous presure (don't know that) that the fuel they used had to be very heavy to keep the engine from becomming a fragmentation bomb.
in fact the fuel they ran had been invented 40 years earlier by the nazi's to run millitary equipment on. mainly the Tiger/pfanzer tanks.

so keep in mind that you need to do some serious mods to keep an engine in one piece but it also takes an enorumous amount of abuse to take one appart, unless you don't know what your doing offcourse.
hayabusa's are now running 800+hp on a stock redrilled (hamburger type) block

back to topic: Question? why does everybodie use compound systems on diesels and not so much on petrol? has it to do with boost levels vs fuel?

here's a piccie of a megatron btw, look at the sheer size of the compressor regarding its only 1499cc's of engine?
racecarsdirect has one for sale at the moment for only :hypnotized: $19000us

grtz Thomas

 

[Toysrme]

I think it's simply a lack of knowledge about the subject. There's no reason you can't do it with gas. Just keep the charge temps under control.

 

[91_4x4runner]

Maybe it adds too much boost for the vehicle to handle? (Diesels to handle almost double the compression of gasoline engines, don't they?)

 

[Toysrme]

Partly, yeah. But I don't see it being a problem for the types of built-engines that would really utilize it. It's like. The 10-11.8:1 engines would be around 30-40:1 peak effective compression ratio.

But a built engine @ 8 would only be around 25:1. There's alot of boosted re-pistoned gas engines around running that kind of compression ratio.

 

[Anaema]

three turbos to produce roughly the same amount of power as a single turbo?

the weight and cost of the setup would outweigh any further benefits.

the trouble with the compound charging maths with rotors is, each rotor is (for lack of other comparison's sake) a 3cyl piston engine by itself, but working in unison with the other rotor(s).

you'd be compound charging a compound charge in case of a 13B, or compound charging a compounded charging of a compound charge in a 20B's case.

now, after reading that, who thinks the word "compound" looks funny...?:Eyecrazy:

it's the reason why triples fed by one exhaust port on 20Bs don't work as well as a single fed by three exhaust ports. pulse wave reflection timing on both the inlet and exhaust ports dictate power, not the amount of boost stuffed in or out of them. that's why you can make so much power in a rotor's exhaust, and lose so much at the same time.

what i mean is all three exhaust ports runing a compound setup. that would be killer.

 

[robertk515]

Well your not exactly right, (ger)BMW and (USA)megatron used stock!!! cast iron bmw2002 2.0L engine blocks which had drivven at least 100.000 road kilometers of the 1969era for the F1 turbo engines,
The internals we're custom because F1 regulations said <1500cc for turbo cars. crancks where steel and rods also. alloy heads with steel components for the valve train. so no fancy alloy's anywhere. exept for the bearings maybe...???

the 4 cylinder the quialifying trim had ONLY 11000rpm which was even in the 80's very low for 4 cylinders you can have a 1uzfe do that nowadays with off the shelf components.

the turbo's early kkk later garret, where operating at such an enourmous presure (don't know that) that the fuel they used had to be very heavy to keep the engine from becomming a fragmentation bomb.
in fact the fuel they ran had been invented 40 years earlier by the nazi's to run millitary equipment on. mainly the Tiger/pfanzer tanks.

so keep in mind that you need to do some serious mods to keep an engine in one piece but it also takes an enorumous amount of abuse to take one appart, unless you don't know what your doing offcourse.
hayabusa's are now running 800+hp on a stock redrilled (hamburger type) block

back to topic: Question? why does everybodie use compound systems on diesels and not so much on petrol? has it to do with boost levels vs fuel?

here's a piccie of a megatron btw, look at the sheer size of the compressor regarding its only 1499cc's of engine?
racecarsdirect has one for sale at the moment for only :hypnotized: $19000us

grtz Thomas

Damn.... that is impressive, i should have researched these before i commented. i guess i was reffering to the newer F1 engines in my post.... i should really read more carefully before i comment.. oops.:tapedshut:

and yeah, back on topic.... diesels have more compression only because they have huge rods and a much larger stroke than any gasoline engine. but ill leave the math to the people that can do it correctly..