twin t70 turbos - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 14 Old 01-20-2003, 05:33 PM Thread Starter
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Question twin t70 turbos

i switching my 88 lx from an s-trim to a twin turbo set-up from a local guy and have some questions.

i have to run very little boost to keep my stock block together until i can build a dart set-up.

what can these things put out for hp?
what is the least amout of boost they will do and max they will put out?
they have the q-trim option. whatever that means.
thanks, steve


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post #2 of 14 Old 01-20-2003, 07:00 PM
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Are you kidding me???? Twin T-70's Should be good enough for well over 1000 HP! That would be FUN!



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post #3 of 14 Old 01-20-2003, 08:06 PM
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Start saving for the Dart block now Precision Turbo rates their q trim T70's at 830 hp.....so you could have about a 1600 hp ride

Q trim refers to the size of the turbine wheel in the exhaust housing. Some have P's, which are a lil smaller than the Q you have and won't make as much power but would spool a lil quicker.

Scotty we need more power!!!
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post #4 of 14 Old 01-20-2003, 08:57 PM Thread Starter
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Question BOOST???

WHAT ABOUT THE MINIMUM BOOST? MAX BOOST?



THANKS for the replies!!!

later, steve

87' GRAND NATIONAL- 3.8 SFI TURBO
BIG TURBO, LOTS OF GO-FAST PARTS

88' MUSTANG GT- BONE STOCK,3.73 GEAR, 21 MPG

"INJECTION IS NICE, BUT I'D RATHER BE BLOWN. WHY NOT HAVE THE BEST OF BOTH WORLDS?"
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post #5 of 14 Old 01-20-2003, 09:30 PM
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Minimum boost is however low of wastegate springs come with them, and they can make enough boost to split your stock block in half like a coconut

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post #6 of 14 Old 01-20-2003, 10:16 PM
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Quote:
they can make enough boost to split your stock block in half like a coconut
ONE of them would make enough power to split his stock block in half.....I'd be afraid to see what two would do!
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post #7 of 14 Old 01-21-2003, 01:43 AM
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Split it in four, perhaps.
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post #8 of 14 Old 01-21-2003, 09:45 AM
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It's quite possible that you'll put 70mm turbos on the wrong side of the surge line trying to run them that way. To keep the stock block together you're going to want to stay around 600hp or 300hp each. Depending on your motor, that may be 6 or 7 psi or lower which I would venture to say would be right on the edge of surge. I would never recommend that.

Shane Hill
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Thanks to TranzKing, MMR, BS3, Don Bailey, Team Z, and Wolfe Racecraft
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post #9 of 14 Old 01-22-2003, 01:09 AM
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What exactly happens at that point Shane.
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post #10 of 14 Old 01-22-2003, 08:00 AM
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Josh,

Here's something I found a while back that somewhat explains it. I don't remember where I copied this from, unfortunately. In essence, to minimize surge, you must increase the compressor flow rate so that it's farther inside the operating envelope of the compressor(which in effect, gives you more power). You can also create surge(even with high flow rates) if you don't have a blowoff/bypass valve when you close the throttle. The high pressure air column in the inlet tract stalls the compressor wheel and turbine.

<snip>To understand what is happening inside a compressor you should think of thousands of little airplane wings all flying around in a circle.

Airplane wings must make lift, or in other words, increase the pressure on the bottom side of the wing so the airplane will lift off the ground. The wings do that by the angle at which they hit the oncoming wind and the curve of the wing. The compressor blades are the same. Each little blade acts the same as an airplane wing.

A wing needs a certain amount of velocity to start making lift at all. This is the same as the air velocity in the compressor at minimum flow, otherwise called the surge point.

Below this minimum velocity, for which the volume flowrate is given (rather than the airplanes lift-off velocity), a pressure increase on the discharge side of the compressor blades can not be generated very well, if at all.

This velocity is equivalent to an airplane's stall speed. The flow separates around the wing, or the blades in the case of a compressor, and the flow patterns disassociate, losing the capability to generate lift or make a pressure increase on the discharge side of the compressor.

At the same time as the flow patterns disassociate, there is still high pressure air that has already been packed into the discharge areas of the compressor.

When the compressor blades can no longer maintain the high pressure in the discharge area, that high pressure air that has already been packed in there, blows back through the blades into the still lower pressure suction area of the compressor.

This, of course, wants to turn the compressor in the opposite direction and plays heck with the drive shaft and just about everything else, and the turbine starts to slow down. It soon recovers and begins to build lift or increasing pressure again, until it happens all over again. If you have a lot of capacity and its a large high pressure compressor, it can sound like a pretty good thunderstorm is going on.

The opposite to this surge point is the stonewall effect(choke flow in turbo-speak) which can occur at maximum flow. The density of the air in the discharge portion of the compressor becomes so great that no more can be moved through and a pressure build up occurs which can no longer be sustained. The compressor has "stonewalled" or reached its maximum capacity and some of the high pressure air bleeds back through the blades with no further net increase in the flow.


Shane Hill
90lx with a 304ci 4v, Turbo400, and 105mm turbo
Thanks to TranzKing, MMR, BS3, Don Bailey, Team Z, and Wolfe Racecraft

Last edited by NoSlix; 01-22-2003 at 08:06 AM.
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post #11 of 14 Old 01-22-2003, 02:39 PM
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I think when everyone's done with this post, it should be moved to the archives. Great information.

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post #12 of 14 Old 01-23-2003, 01:45 AM
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Okay that makes sense. Kinda like compressor stall on a turbofan engine.
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post #13 of 14 Old 01-23-2003, 09:00 AM
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It's EXACTLY like compressor stall on a turbofan. Same basic principles apply to all centrifigul compressors.

Shane Hill
90lx with a 304ci 4v, Turbo400, and 105mm turbo
Thanks to TranzKing, MMR, BS3, Don Bailey, Team Z, and Wolfe Racecraft
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post #14 of 14 Old 02-01-2003, 01:23 PM
 
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I think one t 70 is more than you can handle, And they have compressor maps which will show you the sweet spot of turbo which you will be way below
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