jazzz007

This may be off the wall but I have been brainstorming about the complaints of the rear mounted turbo or turbo in general. Turbo lag vs total output. Using a smaller turbo with a lower A/R gives quick response but runs out of wind too soon... a big turbo that gives HUGE boost is great on the other end but the race is half over before it ever starts. SO.... here is my idea... A turbo driven turbo. Use a small T3/T4 with a smaller A/R to drive your Massive turbo which pipes back to the engine. This allows a lightning fast response with a total output big enough to keep a big V8 breathing well past 6500 rpm's... You could have the best of both worlds... Now... You FI guru's... tear it apart... I'm sure there is a reason that people aren't doing this... I just want to know why?? I'm new to the turbo scene and lookin' for a good education...

SpaZMaN

iTrader: (5)

I thought thats how a twin turbo setup worked? a smaller one for low end and a big one for high end?

smokinHawk

iTrader: (48)

turbos cant drive turbos, they pump air into the engine with the use of exhaust. ONE of the reasones a small turbo runs out of steam is because its small exhaust passage, the other is the compressor can not supply enough air or it super heats it. so having one big and one small doesnt really work.

Hennytime

iTrader: (33)

isnt that what a sequential system is?

camarols1

iTrader: (17)

Only high boost diesel applications are able to use sequential turbochargers.
The design is not practical for a gasoline burning engine.

mr. peepers

You should explain that to the Mitsubishi crowd. The 3000GT VR-4 runs twin turbo v-6's. Oddly enough, it is sequential.

LittleV6

Believe you are talking about a staged system. The outlet of the first turbo feeds the inlet of the next, compounding the boost, making 80+ PSI. Tractor pull engines use up to 4 stages (maybe more, someone just needs to make it) and make 200+ pounds of boost. Typically only use on diesels.

A sequential system has two turbo’s, only one is used at low RPM and the second is brought in as the Rev’s increase to support more power. Both turbos draw air from the atmosphere and push it into the engine. In this type of system boost pressures are not compounded. One example of this is the 4th Gen Toyota Supra, it uses two turbo’s of the same size and brings them on sequentially, one at low RPM and the second as Rev’s increase.

Then there are parallel twin systems, both turbos all the time. This is basically the same as having one turbo, but there are two smaller ones instead of one big one. Most twin turbo systems on gas engines are this way.

LittleV6

No they are not. They are parallel. (I have one)

As for the first post, I am unclear on how exactly you are talking about plumbing them, can you be more specific?

camarols1

iTrader: (17)

I agree, I believe the intended usage is unclear.
If you have one turbo feeding another, regardless of the proper technical term, it will obviously make way too much boost for a gasoline burning engine to deal with.
This is a topic that could be researched on the turbo diesel truck boards,
or tractor puller based sites.

bboyferal

iTrader: (9)

diesel engines for the tractor pull use "compound turbos," one turbo feeding into another. This is how they reach 150+ psi of boost.

sequential turbo is not the same... i.e. not feeding into another...

Roadie

In compound turbos, the second turbo (the one hanging off the downpipe of the first) is usually feeding boost to the compressor inlet of the first turbo. Air coming in is the reverse of air going out. They don't spool faster (in fact, they spool slower, but build extreme amounts of additional power).

If you can make 1000rwhp with a single on a gasser, there's no need to add another like this. Sequential or matched twin setups aid in spool time by using smaller turbos which spin up faster due to less impeller mass. Sequential helps more because one is sized smaller to spool really quickly.


The STS design is the reason you can't get better spool time from a rear mount. They lose the efficiency advantage that front mounts have due to loss of exhaust heat over the 10+ feet of piping to get to the rear. Wrapping the exhaust helps somewhat, but that's the only option you have without moving the turbo toward the front.

kbracing96

iTrader: (25)

Here is an example of a compound setup for a Dodge Cummins that BD makes

Speed

iTrader: (33)

I'm building an electronic sequential system right now. What you are refering to is compound turbocharging which is where the output boost of one turbocharger is fed into the inlet of a second turbocharger. Normally, both are driving off the same exhaust stream.

My setup diverts all the exhaust energy to one turbocharger so you take advantage of the entire displacement to spool the turbo. After certain criteria are met, some of the exhaust stream is diverted to the second turbocharger where it continues operation as a twin turbo system.

pdanrichey

iTrader: (4)

The TT Supra is also that way. One's a little smaller than the other, but one doesn't drive the other I don't think. It's a strait 6, not sure how that works but I imagine it's a similar concept...
The VR-4 was a TT V6 and each side of the V powered a turbo, then using a "Y-pipe", the charge pipe came back together and headed into the TB.

LittleV6

Supra's have two equal size turbos. They have a control system that runs all the exhaust to one till X RPM, then starts spooling the other. The control system is what makes it sequential. http://www.modernracer.com/features/...yotasupra.html

3000GT's have two equal size turbos also. One on each bank. Both are used at all RPM's. They are parallel.

Both parallel and sequential turbos do the same thing, add the flow of two small turbos. The 3000GT uses two really small turbos and makes 320 HP and 315 TQ. The Supra uses two small (but substantially larger than the 3000GT) with a complex control system and makes 320 HP and 315TQ. Stock turbo Supras can make more power than stock turbo 3000GT's.

Compounding and “stage” turbo systems are the same thing. One feeds the other and you get lots of pressure.

Project GatTagO

iTrader: (7)

The third gen RX7 twin turbo system works the same way.

Andrew

pdanrichey

iTrader: (4)

Well then, we learn something new every day. I'll be the first on this thread to admit I don't know jack about 6 cylinder foreign turbo cars...

LittleV6

I knew a lot less about LSX's till I got a link to a thread here and just kept browsing around. I don't know everything about Supra's or LSX's but I like to know more than one car so I keep reading. I am interested to see how well Speed's sequential setup works. I have though about doing one but they seem rather complex. I am working on doing a single turbo on my Dodge Stealth (same as a 3000GT if you didn’t know).

pdanrichey

iTrader: (4)

Ya, I use to own a 3000gt...sold it after I bought my SS. It was a 1995 NA with 103k miles on it. Sold it for $6k with a fading paint job...good car though.

Not to hijack the thread, but I raced a TT stealth not too long ago. Younger kid...had 2 girls in the car with him so I have to give him applaud for being a .... Raced from about 40mph to 110 or so. I actually wanted to give him a run for his money so I started out 3rd gear verses 2nd. I don't know what mods he had other than exhaust, a huge freaking tach and a shift light.

Obviously I'm not exactly in my power band yet and we honk it off. He pulls away pretty quick and I contemplate downshifting into 2nd, but what the hell...I just let it run. Once he shifts into 3rd, I'm about to his back bumper but I'm only doing 70 so I have plenty of gear left. By the time I'm well into my powerband...around 85mph, I'm passing him...then around 100mph, I shift into 4th and just keep pulling him. I let off around 110 or so and had him easily by 2 car lengths.

We're on the highway, but he pulls up next to me and tells me to roll down my car. He begins shouting explicit terms about how "cool" that was to race me. I could barely hear him so I nodded and then took my exit off the highway. Good race though!