curacaosfinest

iTrader: (12)

i've been searching around and havent heard of anyone do this in an FD yet

basically what i'm looking for is a good 380-415hp at the wheels but i want to be at full boost around 3200 rpm...i've seen guys with the a-spec gt3574 turbo getting at full boost around 3500 rpm...

now with that said...i'd also like to do something different...i noticed the setup on the ford dually turbo diesels...they run a small turbo into a larger turbo...

i get the advantage, small turbo for low end rpm power that flows into a larger turbo so you still have boost at low rpm while the big turbo spools up

does this make any sense on an FD?

by the way, i am going to be street driving my FD all the time like 3-4 times a week...so i want power with minimal turbo lag, and i'd rather not keep the stock twins

what do you guys think, dont go crazy if its a dumb idea, just wondering wut the turbo gurus think about the idea...

ByeByeSti

its a crazy idea thats why you havent heard of it sir haha. but yeah i know what your talking about, the new f350's are set up that way and we have had nothing but issues with ours. builds boost alootttttttt quicker than our 07 does. we have 07 single turbo and 08 twin turbo. without a doubt its instant power

Trots*88TII-AE*

iTrader: (11)

for 400 whp, it would be a waste of time, money and effort. you could get the same out of a T04E 60 turbo with equivalent or less spool time.

BTW It's called turbo compounding, some supra guys do it for outrageously large turbo setups. Adds complexity, extra heat, weight, and all kinds of bad things. Feel free to try it though.

Evil Aviator

Turbo compounding is when a turbine is mounted downstream of the turbocharger, and that turbine helps drive the crankshaft as opposed to a compressor.

I think the OP is talking about two-stage turbocharging.

curacaosfinest

iTrader: (12)

ok but wut if i did like a tiny little turbo into say like a gt42 or somthing...i wouldnt be doing this for real, but hypothetically if i did, it would pretty much be like 500 or 600 hp with like no lag right?

and wuts the difference between two stage turbos and turbo compounding?

Liborek

Two stage turbocharging-larger turbo at certain PR ratio feeding smaller one, at low revs large turbo basically isn´t working, all is done by smaller one, which is of course feeded by exhaust primaries... but here we are working with huge pressure ratios... I think that smaller turbo with appropriately sized turbine for this system will considerably choke top end, huge buildup of exhast pressure...

For what you want, properly build single do the work... there is much more things what you can do to enhance spool-right turbo for given power level, manifold desing...

Turbo compounding is extracting of energy from exhaust... For example in 200BHP N/A rotary is 300HP worth of energy in exhaust. NASA did study and found that even very basic system should gain net 100HP on shaft, so BSFC should go down to 2/3 of original value

Trots*88TII-AE*

iTrader: (11)

You're absolutely right. Sorry, I unfortunately got lost in the terminology of the un-informed.

http://www.boostlogic.com/xcart/prod...?productid=160

curacaosfinest

iTrader: (12)

so the larger turbo feeds into the smaller turbo? and what is meant by a low and high pressure turbo...is a low pressure turbo the same as saying a turbo that has less flow capacity than a large turbo? i.e. a gt25 turbo is low pressure and a gt42 turbo is high pressure?

sorry all this terminology gets me confused

Liborek

https://www.rx7club.com/showthread.p...bo+compounding

Originally posted by ScorpionT:

"Basically, the smaller turbo is spooled first then the exhaust is routed to the larger turbo, then to the downpipe. The larger turbo compresses the air a little bit, then it goes directly to the air intake of the smaller turbo compressing it even more.

The idea is that the larger turbo usually cant stuff that much air into the engine at low RPM, the engine just cant take it and the turbo surges unless it has a ported shroud. With a compound setup the smaller turbo compresses the volume so it fits, meaning you can more power at lower RPM. The small turbo cant take in a big volume at low speed so you cant make power, the big turbo can take in a big volume but its not compressed enough. Put them together and its the best of both worlds. Low and high speed power. Im not positive how the wastegate system works exactly, so Im not much help there."

Trots*88TII-AE*

iTrader: (11)

Don't get me wrong, for an 800 whp application, I think this would be a great way, although it does add complexity. But for the OP's goals, a properly setup single can meet those goals, for a lot less.

Dudemaaanownsanrx7

iTrader: (23)

I'm not sure everyone is on the same page. What the OP was asking about is referred to as compound turbocharging. The exhaust energy flows into a smaller turbo, then into a larger turbo, the larger turbo then flows pressurized air into the smaller turbo which compounds the boost. This system has been used on modern diesels, tractor pulls, and some of the supra guys have also picked up on it for both fast spool and high boost levels.

A turbocompound system is one that connects the second turbo to the crankshaft, it uses a gear and transmission type instead of a compressor cover for the second turbo.

Two stage turbocharging is basically any system that uses two turbos. it covers a wide range of systems. Could be anything from 2 turbos online all the time, or one large turbo and one small turbo that's staged, even the sequential system in the rx7 could be a form of two stage turbocharging. I'm sure even compound turbocharging could be lumped into the 2 stage category.

There is a pretty good thread on RCC covering compound turbocharging. For the OP's goals it's a big waste of time and money. If you wanted something like 600+ hp with faster spool this is the system to do it with. But, you have to match the turbo's correctly and it would take some trial and error to get it right. Here's a Pic of a compound turbocharger setup.

Evil Aviator

Some of these links may help answer your questions:

Garrett on how to size a staged turbo system:
http://www.turbobygarrett.com/turbob...esel_tech.html

Borg Warner's regulated 2-stage turbo system:
http://www.turbos.bwauto.com/products/r2s.aspx
http://www.turbos.bwauto.com/tools/d...nt&r=106&d=107

Huey helicopter engine diagram showing the various stages. Axial flow compressors are only good for a pressure ratio of about 1.2:1 to 1.5:1 but are very efficient, so they are best used for initial stages. Centrifugal compressors are good for a pressure ratio of about 4:1 to 7:1, making them better for the final stage.
http://www.aircav.com/Huey/compressor.html

Garrett TPE331 engine shows the design differences between the high and low compressor stages. The resulting compression ratio was 8:1.
http://en.wikipedia.org/wiki/Garrett_AiResearch_TPE-331

LOL, you are less confused than a lot of other people.

Yes, it is unfortunate when laymen screw up technical terms because I think it adds to the confusion for those who are trying to learn. Other than that, I guess it doesn't matter much unless you work in the industry. However, incorrect terminology makes it difficult to search the internet for good information because you will get mostly ghetto web links like the one you posted above.

Zero R

iTrader: (1)

All I know is one of my closest friends in the industry, who has been one of the largest turbo houses in the country for over 20yrs and competes in the diesel performance industry calls it compound turbocharging or a compounded turbo setup. He is about as good as it gets and runs well over 200psi He is not the be all end all in turbo's, but he is the only guy I trust when it comes to questions about these setups or flow issues over 50-60psi. We talked about doing it years ago on a rotary and his thought was it wouldn't be as efficient on a high revving motor, though he was very interested in seeing how it would perform.

~S~

Evil Aviator

... and many of the outstanding mechanics who build winning race cars may call a centrifugal supercharger a "blower", call a Roots supercharger a "compressor" (or "Kompressor" if they are German, lol), call a strut a "shock", call wheels "rims", mistake centripetal force for centrifugal force, mistake 1 BAR for 14.7psi, quote torque in ft-lbs rather than lbs-ft, etc. They may also use words like "ain't" and "orientated", lol. Fortunately for them, I am not aware of any case in which non-standard terminology has caused a car to lose a race. Also, industry standards are not necessarily required in advertising (at least in the USA), so you can pretty much call your own product whatever you like.

However, when possible, I think it is better to answer the OP's question with generally-accepted industry terminology and methods as opposed to slang and unsubstantiated speculation. I am sure the OP would appreciate it if anybody would like to post some "compound turbocharging" technical information from the supercharging industry leaders (Garrett, Borg Warner, Cummins, etc.) as I have done with the staging information.

He has a good point there.

Dudemaaanownsanrx7

iTrader: (23)

I think one drawback aside from the cost and complexity is the additional back pressure created. This would require additional boost to make up for the restriction. From a turbo standpoint this isn't too much of a problem, but from a heat and stress point of view it may hurt reliability on an engine that is already very particular.

Zero R

iTrader: (1)

I think you're arguing semantics. Is it a engine or a motor?...lol. If he called any number of diesel places and asked for a staged turbo system chances are very high the shop on the phone will ask... do you mean a compounded system? You can call something whatever you want till your blue in the face, if everybody else excepts another term as the norm your the one stuck explaining yourself. We should all be talking in P/r's then instead of PSI or better yet "boost". Think about it, undivided or open volute, twin scroll or divided, Compressor or cold side, Turbine or hotside? You are compounding the pressure side (or "boost") of the system, and a FD could be said to have a staged system as well, but it couldn't be called compounded. Greeks gave up a long time ago getting americans to order a Gyro correctly. I agree though entirely, without a doubt it does a disservice to give out false or incorrect info.

ProjectD

iTrader: (15)

Perhaps your goals could more easily be achieved with some BNR stage 3's ran sequentially. Have you looked into that option yet?

Evil Aviator

That is exactly my point. If every major turbo manufacturer's website, engineering book, and SAE paper calls it staging, then you can search for "compound turbocharging" until you are blue in the face and come up with nothing but diesel turbo kit advertisements from mom and pop shops, misleading internet forum threads, or turbo-compound engines. Sure, a mechanic who works in some far-off shop somewhere may call it compounding, but that isn't going to help the OP or anybody else reading this thread search for useful technical information on the subject.

Yes, a stock FD does employ sequenced parallel compressor staging, as opposed to the serial compressor staging discussed in this thread.

Just for the record, Gyros are one of the few ethnic foods that I can order correctly because there was a large Greek community near my first college. I am still murdering the Italian food names even after 5 years in St. Louis. Fortunately, the Italians have much more patience than the French, lol.

Dudemaaanownsanrx7

iTrader: (23)

I'm pretty sure you will find more valuable information if you search for compound turbocharging, because that's what it is. That's what the supra guys, the tractor pull guys, the diesel guys and pretty much everyone that i've seen calls it. Staged turbos is too broad of a term that can refer to any turbo setup using more then one turbo per exhaust bank. And adding to the confustion is turbocompounding, which is not the same as compound turbocharging.

jaila05

iTrader: (12)

if u still looking for a nice N easy 350+hp turbo set up i got one that u might be interested..

just check out my thread. and lemme know if ur interested i can give sum info

https://www.rx7club.com/2nd-generation-rx-7-1986-1992-parts-194/n-rear-end-n-d-shaft-stockt2-down-pipe-868978/

arghx

iTrader: (3)

Chaotic_FC

I think a compound turbo setup is a great idea for a rotary engine!!
there is no reason why it wouldn't work amazingly!
you would just have to throw a nice 60mm wastegate around the small turbo, so there isn't a flow restriction at higher rpm.. have it open once you see boost raise past the max boost of the small turbo.

I'm sure its possible to create a lag-less system geared at 400rwhp with a compound turbo setup... but you have to ask yourself, is it worth it to have all the extra complexity thrown in there.

It is absolutely possible, so dont let anybody tell you it isn't, and only YOU can be the judge of whether it is worth it or not.
i mean, it would have an extremely fat torque curve.
if thats what you're after, **** all these haters and do it!

Trots*88TII-AE*

iTrader: (11)

I think you should boost the **** out of your motor with compounded twin-scroll turbos while eating gyros (jy-roh-s) and pissing on stock twins.

/problem

Evil Aviator

Well post it then. I would love to see an SAE paper or technical article by a major manufacturer that uses redneck terminology. My co-workers will get a big laugh out of that when I send them the web links.

Oh great, now all the rednecks on the internet are going to tell me that I don't know how to pronounce "gyros", lol.

ronbros3

it would be great to see someone try it.

here in Austin the supra guys got down and workin great , no lag 20psi at 2500,, 38psi at 5500,, shift at 9200rpm.

secret ,2 waste gates and 2 controllers,, 80 to 180mph 4th gear roll,

one guy boast never been beat,on a 4gear roll. including superbikes.

top end runs,, a supra 246mph clocked at Texas mile, thats a 1 mile drag race, not a flyin mile