rx7passion

i was reading a article on vw motors and a guy was talking about staging turbos. feeding one turbo into another in get insaine amounts of boost. here is the link to the thread, http://shoptalkforums.com/bbs/NonCGI...ML/000350.html i was thinking of like a 60-1 for the first turbo and a huge secondary like a t88 or t-76 and it would be possible say 15 psi from the first and 20+ out of the second. that would be 35psi!! more if your ballsy.

i was thinkin this shoudl be tried with a rotary cause they can take great amounts of boost and have very good exhaust pluses.

any opinions from crispeed or riceracing on this?

thanks

spyfish007

you don't do pressure addition ..... it is pressure ratios so you would get WAY more boost that 35 psi ... more like 55 psi ..... plus sizing is more complicated than you could imagine .... not to put down your imagination ... I applaud that.

Cheuk in Seoul

This is a common setup for huge diesel engines. But I agree is impractical for our cars.

This staged / serial turbos is where we get the term Intercooler. It is a cooler inbetween turbos. Most cars actually run Aftercoolers.

rx7passion

i dont understand why it would be impractical for a rotary, if it was a BP or PP that could rev real high and you match the turbos compressor maps so you dont over kill them. like if you had a t-100 or something over kill right off the exhaust ports and a t04 with a small a/r and a good compressor wheel to help spool the turbo up. imagine 55psi at like 4000rpm to 10,000 that would be tire roasting fun!

spyfish007

imagine the heap of metal you would have @ 55 psi ++ !!!!!

crispeed

Hey Spyfish!
The quickest car at Orlando was running 45+psi on a 13B without any heaps of metal!
I on the other hand left one of my apex seals somwhere on the track at the end of the 1/4 mile!

crispeed

crispeed

That's the problem I'm going to have to deal with my new set-up.
One turbo or two to flow enough air to support 40+psi at 10K+!

crispeed

spyfish007

Well this conversation is getting into the 55+ psi range ... now we are starting to talk about some HUGE power. The question does become, how long can we keep it all together?

Also you need a nice big 1st turbo or you aren't going to flow the air needed ..... so one big turbo and one medium turbo in our small engine bay ..... I'll enjoy seeing those pics!!

Node

iTrader: (1)

ball bearing for the first smaller turbo to help it spool

Styk33

When you run staged turbos you can run them one into the other. Just like Cheuk said, that is were the term innercoolers came from. The thing that you need to figure out is the size of the first turbo to get enough air into the motor and yet not have to much of turbine. Then the next turbo will be sized based off of the first turbo size since you will be spinning both of them. Since T-88 is a kit and not a turbo, you might want to pick something else out. Plus if most people get full boost around 6k on the T-88 kit, what RPM and porting will it take to get full boost with having to spin another turbo on top of that.

Even still, I would take N20 to spool a big turbo over a twin turbo setup for anything but traffic driving.

spyfish007

staged turbos will take longer to spool up than a large single ....

MeLoco

There is some one out there working on a 60+lbs boost(13B)as we speak they are doing testing right now,also would not plumbing be a issue my understanding is if not plumbed right the second turbo could make first turbo spin backwards (not good) I think this is why both toyota and mazda went with same size turbos just different size wheels if staged to dramaticly you had problems with transition.Do not hold me to this though it's been awhile since I even botherd looking into staged setups so if I'm wrong please school me

spyfish007

The plumbing is real easy to figure out ..... the turbos better be WAY different in size ...... you'll never get it to work with just different wheels. The interaction between the two turbos is complex is sizing must be done correctly. I am friends with a guy who builds twin turbo (staged) kits of diesel trucks. It is very involved and he is like one of four people getting it to work for diesel trucks .... note: big tractor pullers have done this for years! (280 psi w/o any air cooler )

crispeed

I've seen pullers using 3 to 4 turbos staged! Some of them used water injection between stages also! Most of the present racers are divided amongest those who use alcohol or diesel as their choice of fuel. We all know the perfomance that can be obtained when using alcohol as the choice of fuel.
I've seen some of the internals of one of those tractor motors and was amazed at some of the parts that those guys are running to maintain 250+psi of boost pressure.
A friend told me some of those tractors are producing between 2000 to 3000 + horsepower!

crispeed

peejay

Here's something to consider.... if you have one turbo running 15 psi boost (2:1 pressure ratio) feeding into another one with a 2:1 pressure ratio... well, 15psig is 30psia (absolute pressure) times 2:1 makes 60psia, or 45psi boost! (I want to do this someday to a VW Rabbit diesel... So what if it takes forever to spool up?)

New let's take a turbo stuffing 30psi (3:1) forcefed by a locomotive diesel's turbo ( ) also running 3:1... 45psia times three is, ah, 135psia, or 120psi boost!

Some tractor-pullers have been running over 200psi manifold pressure using three staged turbos. The trick is, you must size the final turbo first, calculate the INPUT airflow for that turbo, which is then the OUTPUT for the first (or middle) turbo. The math gets hairy, but it's a lot of fun. Basically it works out that your first turbo is HUGE, and compresses the air enough that it will "fit in" to a simply large turbo, which compresses it even more so that it fits in a normal sized turbo.

What I'D like to do, and have only seen as a theory, is a variation of the staged turbo system: Using a turbocharger between the main turbo and the engine as an intercooling device. You can shed more heat in three ways: Lower the temp of the cooling medium (colder air to the intercooler), larger radiator surface (bigger intercooler), or increase the temp of the cooled medium. This setup does the latter. The mid-turbo (as I'll call it) compresses the air further, making it even hotter still. The air then goes through the intercooler. (500degF air will lose more heat than 230degF air when cooled with 90degF ambient) The charge then DRIVES THE MID-TURBO, losing pressure and heat in the process. It can theoretically be possible to have intake air temps BELOW ambient with this setup, and it requires no water or ice setups, although space would probably be a problem. It doesn't matter how quickly the mid-turbo spools, as boost is only provided by the main turbo. The mid turbo is only there to compress the air, then decompress it. In a way it works like an A/C system, without the phase changing.

I think it'd fit nicely under the hood of a slant-six Valiant.

waynespeed

Hey Chris, Sounds like your going to break more records!

What changes were you planning on making to your fuel system, If any, to deal with all that extra CFM?

crispeed

Heh Heh Heh!

8 X 1600cc injectors
2 X 2035 Weldon Fuel pumps
2 X Weldon Regulators
100% proof Alcohol fuel

crispeed

13BAce

I gather 9's are no longer acceptable?

13BAce

Hey Wayne! Mike's car is almost done. Maybe after the motor is broken in we can get him and Anthony to go to the dyno with us to help defray the costs.

crispeed

I 'm going to run 8's with the present set-up!
I have till the end of the year before I change everything around.

crispeed

maxcooper

There do seem to be some hints at this issue, but it seems most people are forgetting that you will need to flow the same amount of air through both turbos if they are plumbed in series. So for those suggesting a small first turbo, remember that you'll be flowing gobs of air through it, which would seem to kill the compressor efficiency. The two axes of compressor maps are pressure ratio (y) and flow (x). You'll be at the same flow value for both turbos when the engine is running.

The FD turbo setup does not have the turbos in series. Below 4500 RPM, all the intake and exhaust flow through the primary turbo, and above 4500 the intake and exhaust flows are split between the two (nearly identical) turbos. Running all the intake through one of those turbos at 8000 RPM and 10 psi of boost would be bad. On heavily modded cars, the primary turbo compressor is already drifting out of its efficiency range by 4500 RPM.

-Max

peejay

If the turbos are in series, the second turbo must be smaller!

This is because the air is actually compressed inside the turbo, it's not a backpressure thing like with a Roots blower. When turbos compress air, they don't care if the incoming air is 14.7psia or 10psia or 35psia! They just compress it to a given pressure ratio, determined by shaft speed and that particular turbo's compressor map. (Centrifugal compressors are wunnnnnerful things, they just throw air at a wall and let inertia do the dirty work)

Since the compression actually occrs inside the turbo, the output CFM is going to be smaller than the input CFM. If a pressure ratio of 2.5:1 makes a density ratio of 2:1, then the turbo must take in twice as much air as it puts out.

When sizing staged turbos you must work backwards from the engine. Here's why: Let's say our engine requires 400cfm under a given situation - at a 2:1 density ratio the secondary turbo will be putting out 400cfm and taking in 800cfm. Now we must size our primary turbo so that it's OUTPUT is 800cfm, so it can keep the secondary turbo fed. At the same density ratio that means its input will ned to be 1600cfm and we're talking about a big-*** turbo.

I just wonder how much it's worth the compexity anymore, given that we have people showing 45-60-75psi into engines with just one turbo. Sure, a two-stage might be necessary, but no three stages. Unless you can make an engine live under 500-1000psi of boost!

spyfish007

peejay is writing it correctly .....

crispeed: My friend is going to run diesel for as long as he can to see how much he can get out of it .... then alcohol. I'd believe the 3/4 stage tractors making 2000++ hp .... have you ever seen the smoke cloud out of one of these?

crispeed

Yeh!
It's a whole lot of smoke! Got to have alot of diesel in there to burn with all that compressed air.
Everyone down here is into the diesel trucks! The Dodge vs Ford diesel truck street races are actually more fun to watch lately.
Most of the Ford trucks rule though. Some of the guys are using nitrous and injecting propane. I've been in a Dodge/Cummins that was running at 55psi of boost. It's a 4-door/crew cab/dually and it ran high 13's in the 1/4.
One guy dynoed 485RWHP and over 1000RWTQ!

crispeed

crispeed

The next thing I don't understand is how are some of these individuals running 50 to 60 psi with a single turbo! If you go by the compressor maps most turbos don't even support 40psi!
I know it works because I've seen it with my own eyes!

crispeed