sf887

alright since a twin turbo is just two turbo chargers..from what i understand..correct me if im wrong and larger turbocharger would give better high end power and a smaller turbocharger would give more low end power would it be ideal to have one large and one small turbocharger in a twin turbo setup?

Camaro_Zach

iTrader: (19)

not that simple. not by far. i will let someone else go into full depth as im not 110% sure as to why and i dont want it in writing if im incorrect.

V8 Supra Builder

iTrader: (37)

***There are a LOT of variables here***

From what I've researched for the current LM7 project & found with the rear mount LT4 on my Trans Am, the advantage to twins on a flat or V motor is less plumbing and lag. The low vs. high end power is really decided by the AR/trim of the turbine housing, but the compressor AR and trim factor in as well. Turbos need to be matched to the engine based on many factors... RPM, CID, Compression, etc.

I have a 62-1 on the TA, and on the dyno it drops power like crazy over about 4500 RPM, but spools nicely at lower RPM (needs more tuning as well). A larger AR turbine housing would help out on the high end, but I'd lose some low end.

Here is a link to a good website for turbo calculators & related items:
http://www.turbofast.com.au/turbomap.html

Hope this helps.

Camaro_Zach

iTrader: (19)

i thought it had something to do with exahust backpressure being different on the 2 banks...since one would hit full restriction MUCH sooner vs the other one which would be free flowing down low and have "no" backpressure compared to the other side. and again, if you get a "small" turbo ONLY for down low...at 3g rpm you get 100% backpressure because all the air cant get past the turbo...this and this alone should be the only factor. i mean there might be more factors....but this is the biggie.

V8 Supra Builder

iTrader: (37)

Reason # 101 why not to reply after 1 AM... I missed the two different size turbos part of the original post...

This would not work for the reason stated above IF you are talking about connecting parallel turbos (one to each manifold). If you are talking about sequential (two stage, one feeding another) turbos, your idea has merit, but this would entail a lot of work and $ and would require intercooling or possibly two stage intercooling. I believe the last RX7's had this setup (I'm sure someone that has/had one will jump in on this since I know a few are here w/ Gen III motors in their cars). This setup is used on tractors in pulling contests, and they run up to 130 PSI without . I don't see it being worthwhile on the street with the technology that is available today. I'd think the smaller turbo would end up being a restriction at some point in this setup on a large displacement V8 for street use.

Some more info is here:
http://en.wikipedia.org/wiki/Twin-turbo

JZ 97 SS 1500

iTrader: (2)

Sequential and compound are two different things. We build both for customers and the last thing you want is a compound setup on a gas engine. We run as high as 245psi now with some new turbos (quad compound) and a TON of fueling. Sequential is also a pain, but it does not compound the boost from one turbo into the other. It simply goes from 1 turbo blowing into the engine to both blowing into the engine at a preset level depending on the actuation used.

Jose

V8 Supra Builder

iTrader: (37)

Thnaks JZ, my old turbo book called the compound setup Tandem Turbos. I've never looked into the sequential setup and thought they were the same. It is good to learn something new, and that is an interesting concept. I can see how it would be a pain to set up, as mapping 1 or 2 non-sequential turbos can be time consuming.

bboyferal

iTrader: (9)

Besides the RX7's, weren't the late-model 3Si's 3.0 liter V6's Twin Turbo powerplants also sequential?

sf887

alright, so another question. would it be possible on an LSx v8 engine to have a sequential turbo setup on each side of the engine since its a v8? like have a sequential setup running the 4 cylinders on one side and then anothe sequential setup for the other 4 cylinders? would this give good amounts of power and boost? im assuming it would be expensive cuz you'd need 4 turbo's right?

turtle and the hare

Bi turbos have had multiple arrangements, but theoretically you are correct. Multiple car mfr, such as Maserati BiTurbo have attempted this arrangement and have had some success.

But it presents other issues as well, many comments with in this thread have managed to address some if these issues

andy
turtle and the hare
C5 Corvette STS-TT w/ TNT
Porsche 911 3.8 Cab
Porsch 911 T Targa
MBZ ML 350 Special Edition
MBZ 500SE

JZ 97 SS 1500

iTrader: (2)

Yes it could be done. We have designed sequentials for 4 and 6 cylinder cars already. We have never worried about V8's since we have some much displacement its a waste of time. Even with the car not on boost a well built 346-408 can have anywhere from 340-400+rwhp even with low compression . So off boost response is wonderful. Now if this board was the supra board or honda board then this discussion would be leading elsewhere. The main problem we ran across was the actuation and transition from 1 turbo to 2 done electronically.

Jose

bboyferal

iTrader: (9)

Any sequential set-ups on street cars? Supra's maybe?

sf887

alright...so for an ls1 v8 rx7 is having any turbo a waste? i'd like to have it just to say and for the sound of the spooling and BOV more then anything. although the power would be nice...to run something in the 7's or 8's would a good turbo be needed?

bboyferal

iTrader: (9)

Okay, when did anybody in this thread post any turbo on an LS1 was a waste?

The lack of significant incentive to build a suquential turbo LS1 is what was raised... Turbo on an LS1 is a DAMN GOOD idea.

V8 Supra Builder

iTrader: (37)

I'm having a hard enough time trying to figure out if it will be easier to run 1 or 2 on a 5.3 in a MKIII Supra. I'd hate to try & figure out how to put two per side in there! Not sure about the newer RX7- I know the engine bay in the '84 I built was REAL tight for a Gen I 383.

Turbo + Gen III= Great!

JZ 97 SS 1500

iTrader: (2)

Sequentials done so far for the street have been Barra 240 engine, Ecotec, RB26, and Nissan Patrol.

Compound setups have been the 5.9 12V, 5.9 24V for the street and for our pulling boys, JD tractors, Case/INT, and the latest one is another 4 turbo monster 540CI 6 cylinder IHC Case/International. Makes around 2500hp on Diesel......241psi . I absolutely love compound setups for diesels, but for gas engines.....waste of time.

Jose

JZ 97 SS 1500

iTrader: (2)

Not a waste at all if done right. Sequentials are a waste though......

sf887

what exactly is a compound turbo? thanks

bboyferal

iTrader: (9)

Exhaust spools one turbo and forces air into another turbo instead of the intake manifold. Boost ratings of over 200 psi are possible in this way... Boost pressures NO gasoline engine can take. The unique qualities of diesel combustion make them the only motors that can take that abuse with ALOT fo fuel. I think that's the gist, but Jose knows these inside and out.

On that note, QUAD COMPOUND? Holy **** !!!

JZ 97 SS 1500

iTrader: (2)

. Diesels really are fun......