me and a friend were debating about wether this would work or not. the theory was what if you ran dual turbos, ran them both through an intercoller and then fed the oulet from the intercooler directly into a centrifigul supercharger? 1 would it work, and 2 what kind of gains and boost numbers would you see from something like that

im not an experate or anything (and cant spell ) but u shouldnt see much more then u would if u just did the dual intercooled turbo set up becuase the air is already flowing at a faster speed so depending on the supercharger u use it might even slow airflow down until it goes threw it

i would think that theoretically, you would want the s/c in front of the turbos to spool them up quicker, but the heat from the exhaust would kill the s/c,....unless of course you could make the turbos forced air driven form the s/c instead of exhaust driven. but that sounds silly to me. lol
first you need about $10k though for the tubos and s/c

Compound air charging is really the only way to go for huge power applications. If you wanted to be super cool this is what you would to. Twin dual staged turbo chargers blowing into an intercooler and then into a roots blower. Big power everywhere in the operating range.

It is better to accelerate spool the turbo on the hot side than the cold side. The compressor is not designed well to be blown on. When you go to WOT you want as much hot air into exhaust manifold as possible(roots blower) then that spins the first stage turbine up and the engine starts ingesting huge amounts of air and the pressure is then compounded through the blower and then more exhaust power spins up the second stage turbine. Sounds like a fun way to blow stuff up. You don't have to run big overdrives on the blower either.

turbo-supercharged engines usually use a crank driven lobe-type supercharger (similar to an eaton) fed by a turbo. this is for WWII planes and industrial motors (like pumps), never seen or heard of anything like that on a car. On planes it was used to combat the thinner air at higher altitudes.

If you had turbos blowing into a roots blower, it would cause a huge backup in between the two at higher rpm, because this is where the worst restriction and worst efficiency come into play in a roots blower....of cours, the solution to that is to use a really big roots blower, like a 12 or 14-71.

did you guys ever see tht twin turbo twin supercharged nitrous sunbird? it didn't run very well but it would deffinatly make you say ohh $hit.

It's not going to cause that big of a pressure delta. Since a roots blower is a positive displacement pump it isn't as severely mass flow limited as a centrifugal compressor. Once you understand the fluid dynamics behind each it will make sense to you. You're going to have to compromise, but the goal is to improve overall performance.

The only other solution is to run everything parallel, and if you do that you'll have more plumbing under your hood than in your house.

i do understand fluid dynamics, which is why i qualified that statement with one about using a much larger blower than would otherwise be needed.

provided that there was no intercooling, the air entering the roots blower would already be relatively hot, and the faster the blower turns, and the more air is being forced through it, the amount of heat introduced by the roots blower grows in a non-linear fashion....that is why roots blowers reach a point where the heat produced and the drag produced exceeds the benefit of boost.

the solution to that problem is to use a larger blower that doesnt have to be overdriven as much to produce the same boost, or in this case support the same volume of flow. air can't bypass the blower, so if you would have to carefully calibrate the system to never deliver a larger volume of air than the roots blower can support at a given RPM.

our 8-71 blower is fine on the truck, because by rule we are limited to only 10% overdrive....if we wanted to make insane power it would be much easier to use a 12-71. With a roots blower size means alot. we arent even allowed to use a high-helix design, which provides alot stronger boost.

If you introduce already boosted air to a roots blower to further increase boost pressure, it would be imperative that it was synchonous with the first device (whether it be a turbo or centrifugal blower), and that the temperature of the charge is sufficiently cooled before it reaches the roots blower. Otherwise your gonna get some really silly intake air temperatures. PV=nRT

Exactly. I've done some compound boosting work in my day. Most of the time it doesn't work for ****. It works really really good at one RPM and load. After that it just makes life difficult. That'd be a good place for the CO2 injection from that other post.

I think it could work if you did a twin turbo in parallel with a top mount IC for each and then run that into the top of the blower. It would be a fairly short setup too. Not to mention super cool. You could even spray your ICs with nitrous or CO2 to get the pre-blower air even colder.

assuming proper cooling of the charge, it might be possible to make it more friendly using a more complicated than average BOV or bypass valve.

The last multi-tubo engine I worked on had a high pressure exhaust and compressor bypass like you were talking about. The control system for that was really complicated and there were issues with getting a big enough waste gate that would actually seal. It was a nightmare. Getting turbos to respond quickly and flow a lot of air is always going to be a challenge. The best basic design I've ever seen was on the TT RX-7. It was a parallel design where one turbo saw no action unitl a certain flow level and then valves started opening up so that the engine was running on both turbos. The control system on that I think only worked off of pressure deltas so there was a dead spot in the power before the second turbo kicked in. With a computer system it could have been a lot better. The BMW 4.0L diesel uses two VGT turbos in parallel. That helps it to come on faster, but it's still no blower.

ya, i can see how that would work. I would have to say after working on 15 bazillion roots blowers and researching all sorts of centrifugals that the centrifugals are far, far, far better for street applications.

the roots blowers have great low end grunt, but so do the centrifugals.....and most street engines arent big enough to use a really good size blower, and to get nasty top end power you need alot of overdrive, which really drags on the motor at low RPM.

the ATI prochargers seem to me to be far superior to vortech, paxton, and powerdyne in reliablity, quality of kits, workmanship, fit and finish, power potential etc. these guys have their game nailed down and they have the scientific results to prove it.

we are currently in negotiations with ATI for a major sponsorship.....

i'll keep everyone posted on how that works. There are currently no limitations on centrifugal blowers in ProMT, just bans on screw type and high helix blowers. Its very possible for us to use one to make alot more power than some of the big nasty blown hemis with our little 482 chevy. The damn things are so efficient. that would be something to mop the track with ramminator, rammunition and the 'foot team guys.....and do it really really cheap lol.

the TT rx7 you are talking about does have that flat spot where the power lmost seems to drop while the second turbo kicks in

but then again most rx7s that are fuel injectred do that as well at about 3800rpms

second set of fuel injectors kick in at that point also which is when the second turbo on the rx7 kicks in I think


but back on topic

if you guys want I do have a magazine that has a Mr2 with compound induction... I can post the major stuff in there and there tuning issues if you give me a moment


some interesting stuff in there and a few surprises for those trying to tune it

If you're interested in compound forced induction, Turbo & High Tech Magazine is running an article in this months issue (Gold IS300 on Cover) that might be a good read. Its a 2 or 3 part article about a compound forced induction setup (super and single turbo) on a Lexus v6 motor in an older Toyota MR2. Dont focus on what parts they use or what make it is, but you might get a little info about the theory of compound forced induction and what to look out for. You can also write to them and ask them questions about it.

Just read what rx7speed wrote, and its the same mag. Oops hahah

lol. good one just ignore the import guy

ive seen some turbo/ sc combos on tractor pulling...and no im not a hick... tracktor pulling is badass 8000 hp is awsome 4 facking blown nitro hemi's facing each other...badass

you hick


I can't blame you though
having that much power would get me to enjoy it