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Discussion Starter #1
Something I've been rattling around in my dome. After looking at some old f1 and rally set-ups, I've noticed that they seem to use smaller hot sides than I would expect.

If you had WG priority, with enough potential WG flow, why couldn't you run a smaller hot side for quick spool with the WG bleeding off the excess energy when you reach your boost goal?

Is there a way to eliminate stall at lower rpm's?

Anyone know WHY it won't work, or ideas to make it work?
 

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Discussion Starter #3
a larger hot side will allow for more top end power
Not necessarily. If the WG allows enough exhaust to bypass the turbine, then the turbine is no longer a restriction.
 

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Eyeyeye, google. Your wrong.


Bigger hotside will make it have potential for more top end power, also allows for higher boost levels to be achieved if the smaller isnt adequite, like the small exhaust holsets. Allowing the compressor map to somewhat over extend.
Smaller exhaust housings will cause faster spool rate allowing that the compressor isnt surging during boost as volumetric efficiency rises, like some of the gt35/40 hybrids on the rb and supra emgimes. Bigger exhaust housings would fix the issue and allow for more stable safer boost building, google ;)
 

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Discussion Starter #7

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Lol, so run a gt45 with a t3 exhaust houaing is what your saying ot am I miss understanding, nowhere did you mention flow as a limiting factor in terms of size, also, your idea would never work on a rotary. Your wrong
 

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Not necessarily. If the WG allows enough exhaust to bypass the turbine, then the turbine is no longer a restriction.
wow, i totally see your point!
by simply discarding the turbine, i should make infinite hp with my d16.
allowing my civic to traverse time as well as space....
 

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Discussion Starter #10
Maybe the way I explained it isn't coming across?

A larger turbine allows for more flow, but reduces transitory response (lag).

If you go with a smaller housing, you reduce the max potential as any exhaust restriction does.

You use a wastegate as a way to bypass excess exhaust gas, as it is currently intended, just to a greater degree in order to compensate for the smaller housing.

I'll try it this way - Your large housing flows 2X at peak rpm at WOT, but doesn't produce desired max boost until 5500 rpm. While a smaller housing, that only flows X at peak rpm at WOT, achieves desired max boost at 4000 rpm. Since the smaller housing only flows 1/2 of what the larger housing does, you need to allow that extra flow to go somewhere. Use a larger WG, or a secondary WG. Will this work? Not has anyone done this, but will it work in theory?

I am also looking for ideas on how to prevent Surge/Stall. When surge/stall happens, do you see a spike in P/R that causes the stall? Would having a WG on the cold side that opened a few psi higher than the exhaust side wg bleed off enough to eliminate stall?

Is my logic all screwed up?
 

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Its right when in the right co,bo but they are pre built or even customized, ie-gt40 with .58 ar t3 housing, doesnt surge on certain motors will, some wont, theory works halfwaay, its just missing everything else we poimted out, make sense.
 

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They ran small turbine housing fro response.
You look at a lot of those setups and you see massive compressors with very small turbine housings, unlike any turbos you see now.

This came at a cost to them. That small turbo e housing generated a lot of heat and back pressure and the oversized compressors by comparison had the tendencies to surge at low rpm.
Sure, you could set your car up like this now, but it's a bit extreme for most.

That being said, I have seen someone switch to a larger turbo with a smaller A/R turbine housing improve both power and spool.
I believe it was from a gt2860 to a 3071 on a Mazda BP
 

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For smart guys like you.
thanks bro, i love proving people wrong like you. lol

it has nothing to do with being able to divert the gases away from the turbo
you need a bigger housing so more volume of gas can turn the turbine more efficently. think of taking a large stick and have a big heavy fan on one end and a small light fan on the other end. the air to push the little one is going to take a lot more effort and volume to spin the other side as if they were both the same size. the easier and more efficent a turbo spins, the more power it will make. your compressor side of the turbo is what makes the power, but if the hot side isnt large enough your power is going to be limited to the hot side.
 

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Discussion Starter #14
I feel like I'm in the fucking Twilight Zone here.

The theory DOES work. It has been applied NUMEROUS times.










Look at the turbine size vs compressor size. These are motors that were running VERY high rpm's, yet have TINY turbines, relatively speaking. How did they prevent surge?

According to your logic, what they did wouldn't work because the turbine is too small.
 

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Discussion Starter #15
thanks bro, i love proving people wrong like you. lol

it has nothing to do with being able to divert the gases away from the turbo
you need a bigger housing so more volume of gas can turn the turbine more efficently. think of taking a large stick and have a big heavy fan on one end and a small light fan on the other end. the air to push the little one is going to take a lot more effort and volume to spin the other side as if they were both the same size. the easier and more efficent a turbo spins, the more power it will make. your compressor side of the turbo is what makes the power, but if the hot side isnt large enough your power is going to be limited to the hot side.
You are joking, right?

A larger turbine allows for more flow (gasses to pass through), so it allows for more power to be potentially made. If the housing is too small, it becomes a restriction. Big = Lag, more top end power ; Small = Quick spool, less top end power.

FLOW IS THE PROBLEM!!!

By diverting gases around the turbine after peak boost is reached, you control the compressor side. You use a wastegate to do this.

Why can't you use a wastegate to do the same thing, but divert MORE to compensate for the smaller turbine?



Tilt - Surge is essentially the compressor attempting to flow more than the engine consumes, right? So wouldn't the pressure on the cold side spike right before stall? Couldn't you use a WG to bleed off that excess flow? Wouldn't that then allow quick spool, but no restriction in the exhaust, while having a compressor big enough to make big power up top?
 

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Discussion Starter #16
Or even using sequential WG's on the exhaust side?

I.e. 2 WG's are closed at idle. When the cold side hits 15 psi (or whatever p/r keeps you right of the surge line), the first one opens. Because you have a tiny hot side, you continue to build boost, even with one WG open, but you still remain right of the surge line. Second WG opens when you hit peak p/r and keeps you there.

I'm not talking about 6766's hitting 30 psi at 2500 rpm's here. I'm talking about improving transitional response and effectively creating a VGT, but in a round about way.
 

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Can you still produce enough power with the small turbine to power a big compressor wheel?

Two WG's sounds like a good idea, IMO, since I've read that a large gate is a bit 'touchy'. Like a big throttle body, just on the other end of the engine... Could also do a twin scroll turbo and have two small WG's. Possibly even better spool/top end, since you can design the turbo manifold to act like a header too (scavenging); but I'm not sure how traditional wastegates will work (typical WG = abrupt 90* turn).

Honda put a VGT on the K23 RDX.. Should be pretty easy to control, but that's getting off the topic a bit.
 

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Discussion Starter #19
Twin scroll/divided housing.
I was hoping you would chime in, since I know you have spent a lot of time on this goal.

I know divided housing/twin scroll maximizes pulse energy conversion, and having an efficient system to start with is always a good idea, but do you think with priority and properly sized gates I can get the control I am looking for with the smaller turbine?

I ask for clarification because I know you have focused on sub 300hp systems. Do you see this as a practical solution for quick spool on 350-450hp systems?

Do you have any ideas on how to control or eliminate stall?
 

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Discussion Starter #20
Can you still produce enough power with the small turbine to power a big compressor wheel?
Don't see any reason why not. You are still dealing with the same amount of energy per pulse and will actually have higher pulse velocity in a smaller housing, up to a point. The added mass of a larger compressor (relative to the turbine) will have some effect on response, but I would think it would be offset by the smaller housing focusing the pulse.
 
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