Not that I plan to do it... just more of a conversational piece...

Any pro's or cons to it over single methods like turbo or s/c's alone?

I know its gets more complex cause your basically feeding compressed air into another unit that compresses it further... I would think this would get very confusing.

Anyone feel free to chime in

 

you tried searching, only good for diesels really, so are you talking about diesels or gas
if people to it on gas it is just for the bling.

 

Great for diesels that need good emissions and high pressure ratios. Bad for gas engines cause you can't keep the heads down. Compound systems are typically for 40-100psi of boost.

 

only thing i would do would be a huuuge blower going into a roots on a 346 motor...set the wastegate to read pressure before it blows into the roots, then just pulley the roots for something reasonable. this way the turbo thinks its blowing into a bigger engine, and it allows responce to be quicker when using a gigundo turbo. But then again...why bother lol.

 

i do it all the time....part of a mods cost on this credit card...the rest on another

I dont think its needed for 99% of the FI folks out there. With a tbrake, you can leave on as much or as little boost as you want

 

As long as the wife say's it's ok Jerry!! I know how it is also!

 

 

works for MINI's pretty well! they run a GT30 to 35r with the stock supercharger.

thinking about it from a more logical point it works really. you are using a supercharger to get you going then just feeding the SC with the boost form the turbo. if you dont spin the nuts off the SC then it will still be efficent and you can just use the turbo to make higher boost.

there are problems though. mainly trying to cool the air once its passed throguh the SC. most top mount SCs run very poor chargecooler setups (take a look at some of RJWs posts on here. he has redesigned the whipple unit to make it more effective). this reults in high intake temps and less power.

also you have cost, you have to buy both a SC setup AND a turbo kit! this isn't a problem on a MINI cos you already have the SC. and a turbo kit is problably the same ish price as a new bigger SC.

as i said it works really well for them so there is no reason it shouldn't work on any other platform.

there are some other intresting ideas being kicked around though. ECS is doing some work on a sequential STS kit for the Vette. quiet a simple idea of blocking off one turbo and forcing all the exhaust down the other pipe. this spools the first turbo very fast. once you are making boost you cna start to bring the second turbo in. some say that its going to be hard on one turbo more than the other. but when you see turbos lasting 150k mile form the factory, and the fact you could just unbolt the turbos and swap them over, the agruement doesn't really stand up!

hope this helps. if you want any info on the minis let me know.

thanks Chris.

 

Good info, I guess it can be mainly a bling factor , just trying to figure out if theres a way to get benifits from both...

If there were a way to cool the charge from one form of FI to the next, I think from what ive heard that seems to be the biggest issue. I think one of the other issues is in this particular scenario... making efficient use of both FI systems. So in my opinion, barring all traction issues, if you could have a roots/twin screw setup going into a turbo I think that would be ideal.

Problem is twin screw setups are extremely good for downlow/mid range but not up top, and turbos take a bit to spool so down low they arent so great (unless tiny) but mid and top end are killer...

Maybe theres a way to have the twin screw run, compress air to spool turbo quickly, and then once the twin screw is no longer efficient it can have some type of device to let it "free rev" or disengage kind of like pushing in the clutch and letting the motor still rev, but not under load and then let the turbo do the rest of the work. Then when you get back to that magical efficiency range from shifting gears it re-engages to the point where its no longer needed again.

Or am I just over complicating things?

 

yes you are you think your set up is complicated now, image 2 times the headaches.

 

ya but I dont know 1/4 the stuff you guys do (you for example actually build turbo setups... I on the other hand just talk about them and use mine lol).

but then again im sure even for the most knowledgable person it would definately put a damper on simplying things.

 

We have a local guy that has a twin charged setup on his Talon. He used the car strictly for rally and when it worked it worked very well. He had a 16G on the car as well as a small roots blower on the manifold. It would make about 400 AWHP from about 2000 RPM to redline. The probem was that it was SOOO complicated plumbing, vacuum line, and intake wise it was just a big headache.

Since he was into rally he needed a crazy powerband so he didn't always have to rev the car to get it moving. With this setup he achieved that and he could change his driving style to not be as agressive and still go fast. In a street car or drag car a more simple route will make the same power and be a lot less complicated.

 

I ve thought about trying it on a gas engine for awhile. You just need an exceptionally strong engine. I do run a compound turbo set up daily on my cummins. I can only think of two possible engines that might be able to do it, the srt 4 and the 2jz. Many of the imports are running 40-55 psi now so why not a larger engine? An lsx, 6 bolt heads and low low compression? 6.5-7.5 to 1, liquid intercooling, and run on methanol instead of gas. A 427 running 55 psi should produce some pretty high power numbers....and maybe not even spool bad for a street car, but who really needs a 2200 rwhp street car?

 

Just want to add 4G63. Many people running up to 55 PSI on those as well.

 

hhaha, tell that to the guy with that mid 50's car (forgot what it was) that had 2000hp but turned it down to 1000hp on the street

 

and 4g64s... ive seen those ams evo guys run 40+psi I believe.

 

ForcedAirTechnology out of Arizona have been playing with compound charging with EJ25 Boxer engines. They use an AMG supercharger with a magnetic clutch feeding into a single gt35 or twin gt30's. Power output isn't all that great since a lot of people make the same power with a single gt40. It's more for the "look what i got" factor. Have you guys ever heard of twin-scrolls for turbo's?

 

you are very right on the cooling issue. the mini guys haven't really looked into it yet. it could be done very simple for them (well ok not to hard to do! lol). you could mount a small ish charge cooler over the gear box. that way the hot air from the turbo would be cooled before going to the SC. then form the SC you run a bigger intercooler in the stock location. not the BEST solution but it would work!

as for the SC turbo thing, keep it simple. all you SC is doing is moving a fixed volume of air (ok not true in a twin screw! ). normaly that presure is 1bar (14.7psi). now if you where to 'feed' the SC with air at a higher presure, it would just 'move' the compressed air.

once you put an engine in the way it gets more complex, but only a little. to have an engine setup to run lets say 16psi then you would do thid. have the SC pullied nice and low so its still efficent, say pullied to make 6psi. thenyou would plumb the turbo (with an intercooler to drop the temp of the boost) into the SC. you set the wastegate/boost controler for 16psi and take the referance of the manifold (ie after the SC) as normal.

when the engine is at low RPM the SC will produce 6psi of boost. as the rpms build the turbo will start to spool and diliver compressed air to the SC wihch will then 'pump' this compressed air into the engine. now i dont have a clue what presure will be in the boost pipe from the turbo to the SC, and it doesn't really matter. this is because thw wastegate will still open once 16psi is reached, no matter if its all off the turbo, or just of the SC.

this idea is used in industry to get REALLY high air presure. you basicaly have two compresures in series. the first BIG compresor feeds into a tank and the second compressor (sometimes in the tank) then compreses the compressed air! to brake it down let say the first compresor runs at 10bar. it fills a tank upto this presure and cant compress any more. the second compresir then takes this compresed air and compresses the 10 bar 10 times (like what happened in the first compresor) this gives a combined presure of 100bar! now its easie to mount the second compresor in the tank because then it effectively on running at 10bar so it doesn;t have to be built to tkae 100bar. the probelm is you need the first compresor to be 10 times the size to get the volume in there. thats why compound diesels run a MASIIVE blower and then a little tiny one.

back to real life though, i have seen an ozzy company running a twin blower setup (it on here somewhere, think crafty posted it) on a GTO. basically a vortech blower going into a magy. worked good for them so it should do for others to.

thanks Chris.

 

sounds like a geat project! it has been used in rallying before in the Groupe B days.

now they tend to run small turbos and spin the nuts off them, but thats cos they have really small restrictors (34mm) so larger turbos are pointless. also with modern turbo tech being sooo much better, and with things like anti-lag, they get almost instant boost responce.

but when you think a WRC car will probalby set you back close to $800,000 (£400,000), all that plumbing seems easy! lol

any chance of pics of his setup???

thanks CHris.

 

and finally, as im sure you are all bored of me going on and on lol, here is some actually twin turbo minis to prove im not talking crap!

http://www.altaminiperformance.com/p.../22/Twurbo-Kit

http://www.fireballed.com/machines/m600

thanks Chris.