wierd Q about a twin turbo setup

[raven_240]

Ok, First off please no replys on how One turbo, or sequential ,or anyother setup is the best unless directly compared to this "proposed" setup. I know the basic possitives and neg about these set ups i just whant to know how to get this to work, or if need be why its a bad idea (this is where you can use other setups to compare with).

Ok i want to use the stock turbo i already have on the SR. Now i wanna take the compressed output of that turbo and use it to spool up a bigger one T3, T4 what ever. Im hopeing that this would eliminate turbo lag on the bigger turbo giving me max boost right away as apposed to a little boost followed by big boost like in the sequential set up. It seems good in theary but then if it was everyone would do it.

Side question how much psi do you think a normal exaust would have? maybe 2psi?

[turbo2nr]

yea the theory sounds good but you still wont make good boost untill half way thru 2nd gear, it still takes time to spool the t-25 and it will take longer to spool the bigger turbo,i think personally its a not worth it b\c is very hi maintance and lots of work you have a better chance of building your motor and select a good size turbo with the right a\r and trim,
exhaust might have a little more pressure in it, i know a turbo exhaust might free up about 2-3psi on your car.
good luck
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[J SPEC SilEighty]

Originally Posted by turbo2nr

yea the theory sounds good but you still wont make good boost untill half way thru 2nd gear

Boost is related to engine airflow/rpm, not the gearing.


raven_240, it could work, but it wouldn't really be practical. I'm at school right now so I don't have time to go in depth about how it wouldn't be very practical, but when I get home at 12:45 I'll type something up for you.

[I<3hks]

having a turbo setup like the one raven described is ultimatly the same idea of a hybrid style turbo, trying to reduce the amount of lag by using smaller wheel on the turbine side and a larger one on the compressor side. Basically its the same idea that he posted..... useing a smaller turbo to spool a larger turbo. The efficiency of one turbo greatly effects the performance of an engine and getting the right wheel combo to get power where you want it can be tricky at times..... now take that trickery and double it....... lots of hours would have to go into changing wheels and experimenting with different A\R's, although it can be done if you were to measure and compare how much cmf the engine will flow into the turbine side of the smaller turbo then get the cfm rate of the compressor side of the smaller turbo. then be able to match it to the turbine side of the larger turbo.... and make it effective on creating boost..... but then after all that math and testing and hours the A\R you would need on the smaller turbo would be too much back pressure on the engine and wouldnt produce the power. very expensive, high mantience, not effecient..

solution to this...... a single hybrid turbo same concept more power =)

oh and the side question about exhaust creating 2 psi... no the same amount of air that enters the engine leaves the engine...... air is denser when going in the intake and is burned (expanded)... then it leaves though the exhaust less dense it dosnt produce psi... now if your talking about how much air will flow through the engine that is CFM (Cubic Feet per Minute)

[J SPEC SilEighty]

Ok, so what you want is a small turbo to compress the incoming air and then send the compressed air to another turbo to be even further compressed... right?

Well, it would be a waste of time and money for you. This setup is really only used to create very high boost numbers (70+ psi). It's mainly used on diesel trucks who can handle that kind of boost. Here's an example: Say that the air around you is at 14.5 psi (normal atmospheric pressure is 14.7 psi). This is the air that will be entering the turbo. Say that you want your first turbo to make 12 psi of boost. To get 12 psi of boost, the air will need to be compresed to a 1.83:1 ratio. That will give you 26.5 psi of absolute pressure. Subtract the current atmospheric pressure to get boost (26.5 - 14.5 = 12 psi). Now if you send that compressed air to a 2nd turbo to be compressed another 12 psi, the boost that comes out of there will be 34 psi, or 33.995 psi to be exact. Remember, you first started out with 12 psi of boost and now your up to 34 psi! I sure hope that you have one built ass motor to handle all this boost. If you originally wanted to run 18 psi of boost then after it comes out of the 2nd turbo, you will be putting out 58.3 psi. I sure as hell hope you don't plan on running that on your motor.

I don't believe it's available for people to buy yet, but garrett was working on a single turbo similar to what your looking for. The turbo used 2 compressor wheels, but in a single housing. This turbo is able to make massive boost at super low rpm's. On this turbo the air goes into the turbo the normal way and is compressed by the first wheel and is then sent to a smaller wheel to be further compressed. The 2nd wheel is smaller because the air is already compressed, therefore making it more dense, or smaller as you may say. To give you an idea of how quickly this turbo can make boost, on a 3.0 liter motor at 7500 RPM a T76 can make 30 psi with a shaft speed in the 85,000 rpm range. Garrett's new turbo is able to make the same 30 psi with a shaft speed of only 35,000 rpm.

[raven_240]

No sil not realy what im talking about, i was talking about sending the compressed air of the small turbo into the turbine of the other. But thanks for the info will be helpfull. Very helpfull.

I appreciate the responsis by both of you. Sil yours whanst what im talking about but im glad you posted.

[turbo2nr]

ok well what i ment was that he still wont get enough air flow untill mid second gear to spool up a big turbo like a t-78 of a t51 or something to that extent..
if you send the compressed air to the larger turbo in a way it will work but i will think that you will stil have lag from all the time the air circulates back to the bigger turbo..
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[J_Spec_NiTeMaRe]

Your idea is theoretically possible to achieve, but it's not any more efficient than just having that larger turbo as a single. You will still have to spool the smaller one enough to spool the larger one. They are both connected to your engine no matter what, and your engine would have to work to spool the smaller one, which in turn sends air to the turbine of the larger one...it's like twice the load on your engine. Plus the compressed air of the smaller turbo would be lacking thermal energy in comparison to a normal exhaust-driven turbo, so it would be that much harder of work on your engine. Possible, yes. Practical, no.

[raven_240]

hmm, ok i didnt even know thermal energy had anything to do with turbo efficancy. Thanks I'll have to look into that too.

Ok so the consecsuse still stands, bad idea.

Now what would be the best set up for a track car. I'm not looking for uber boost realy the max ill but in it will probably be about 18 psi, and drag racing isnt my thing. So what would be a good setup. Since you can rev the engine under braking im not sure if a sequencial setup is realy necessary, but hell I've only started into cars about a year ago by chance realy, im just lucky enouph to have good machanics around me, so i dont blow crap up, and a good learing curve.

[Soyo]

this might be retarded or already done or whatever, but I'm not very experienced with turbos so just yell at me and say I'm stupid if so

someone just needs to make a turbo with a small side and a big side, make the inlet of the smaller turbo like 3/4 the size of the larger turbo so you could get low and high rpm boost... would this work, or has it already been done or what? just something I threw out there

[J_Spec_NiTeMaRe]

Originally Posted by Soyo

this might be retarded or already done or whatever, but I'm not very experienced with turbos so just yell at me and say I'm stupid if so

someone just needs to make a turbo with a small side and a big side, make the inlet of the smaller turbo like 3/4 the size of the larger turbo so you could get low and high rpm boost... would this work, or has it already been done or what? just something I threw out there

If you're talking about a singular turbo with a turbine smaller than the compressor, then yeah it exists. It's called a hybrid.

[turbo2nr]

yea but those also have problems yes they spool quickly but they sacrifice top end.. so you get the hp quick but these only so much hp that the turob can put out, the trick is to find an a\r and a trim that will be a good match for your motors dispalcement and flows enough air to make the hp you need..
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[J_Spec_NiTeMaRe]

Originally Posted by turbo2nr

yea but those also have problems yes they spool quickly but they sacrifice top end.. so you get the hp quick but these only so much hp that the turob can put out, the trick is to find an a\r and a trim that will be a good match for your motors dispalcement and flows enough air to make the hp you need..
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Exactly correct. To help you find the a/r and trim go here.. It's for supras, but it will tell you everything you ever wanted to know about turbos.

[U want my Johny]

do yourself a favor and go with a turbonetics T3/T4 Hybrid turbo
You get the avantages of a smaller turbine with the larger compressor
and if you want more top end power then use a larger A/R Compressor
that will work all the way to 300-335 hp but u need to reinforce the
bottom end

[turbo2nr]

335 has no room for imporvement.. i would get a turbo that has room for imporvement, 335 isnt really alot these days with supras running around with over 1000hp and rx-7 havin 800hp and even some eclipse having 600hp 335 isnt all that.. maybe its just me but if i was gona turbo a car i want to get the most i can form it or else i wont be satifyed.. i say build the motor for boost and then drop a nice size turbo to get the max out of your motor.
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