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Old 08-19-2009, 07:17 PM   #1
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Default the hustler effect. smaller A/R on bigger turbo = better spool.

resources:
MX-5 Miata Forum - View Single Post - 1.8 Dyno GT30R

MX-5 Miata Forum - View Single Post - 1.8 Dyno GT30R


OK so the pictures are below. These are a GT30R and a GT35R.

In the first graph (two lines)
the blue is the GT35R with a .63 A/R turbine housing
the red is the GT30R with a .82 A/R turbine housing

Yes, the bigger turbo with smaller A/R turbine housing makes more power everywhere. and SPOOLS EARLIER.




This next graph is just a comparison of the GT30R with .63 housing and the same two above. It is green.




I think these graphs illustrate why I feel I'm awesome.


Discuss.
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Old 08-19-2009, 07:25 PM   #2
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badass. no discussion needed.
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Old 08-19-2009, 07:26 PM   #3
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Illustrates what you and I have discussed and agreed on many times; Hustler is just regurgitating bad information. Also, a chance to laugh at all the people who took his advice.

Timing on all miatas is very similar, 1.6 or 1.8, with similar turbos. It the beauty of the pent roof combustion chamber.
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Old 08-19-2009, 07:31 PM   #4
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Still, you gotta remember that's a T3 housing, so the .82 in this case would be like a T25 1.1
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Old 08-19-2009, 07:49 PM   #5
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It doesn't really matter, it still shows what the point is. That turbine housing size on a smaller motor like ours does not need to be large to make great power.
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Old 08-19-2009, 07:57 PM   #6
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i too want a 500whp miata
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Old 08-19-2009, 08:00 PM   #7
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Pretty damn cool. I'm actually thinking of going bigger next year or so and just making my car a toy/drag car. The more I drive the miata the more I realize I can't do what savington and the other track ****** are doing: I'm more into acceleration/drag racing than road racing. This is very interesting should I decide to go 35r in furure
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Old 08-19-2009, 08:34 PM   #8
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I didn't pick that turbine housing for these reasons. I picked it because I run the car on the track, like a man and low-egt is my goal.

Nice try though. Let a playa play.
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Old 08-19-2009, 10:01 PM   #9
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Quote:
Originally Posted by hustler View Post
I didn't pick that turbine housing for these reasons. I picked it because I run the car on the track, like a man and low-egt is my goal.

Nice try though. Let a playa play.

first off, if low EGT was your goal, you'd have an EGT gauge
.

beyond that, what's the point of low EGT? to keep your tailpipe cool?

Understand that EGT is, first and foremost, a function of what is happening inside the combustion chamber. Or more precisely, WHEN it's happening. the later you start your burn (relative to exhaust valve events), the higher your EGT goes. hence why retarding timing raises EGT and why lean mixtures (that burn slowly) raise EGT. If you dump fuel, you lower EGT by evaporative cooling (powercard?) like water injection does.

So next we wanna know how the A/R (flowyness) of the turbine housing affects EGT. If you chose it to lower EGT, why does it?

And since turbochargers work based on extracting energy from the exhaust gas (which is directly related to temperature difference across the turbine or EGT - Turbine Outlet Temp), why would you want to reduce the input energy available to the turbine?

Let's be honest here: once the hot gas is past the valves, it's not gonna hurt nothin unless your manifold is made of cheese with a low melting point.
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Old 08-19-2009, 10:14 PM   #10
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Big A/R lowers EGTs because you can run more timing. Same reason you can delete a cat and run more timing - less restriction means more timing. I wouldn't dream of recommending a .86 housing on a street car, but on a track car? Built motors aren't cheap. There's a reason I run 100 octane and water on Hustler's 94 octane map. Anyone else doing MBT across the board on 94 (91?) octane?

By the way - did you notice the 30R with the .63 housing spooling SLOWER than the 35R with the .63 housing? Something's not right there.
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Old 08-19-2009, 10:15 PM   #11
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Quote:
Originally Posted by y8s View Post

first off, if low EGT was your goal, you'd have an EGT gauge
.

beyond that, what's the point of low EGT? to keep your tailpipe cool?

Understand that EGT is, first and foremost, a function of what is happening inside the combustion chamber. Or more precisely, WHEN it's happening. the later you start your burn (relative to exhaust valve events), the higher your EGT goes. hence why retarding timing raises EGT and why lean mixtures (that burn slowly) raise EGT. If you dump fuel, you lower EGT by evaporative cooling (powercard?) like water injection does.

So next we wanna know how the A/R (flowyness) of the turbine housing affects EGT. If you chose it to lower EGT, why does it?

And since turbochargers work based on extracting energy from the exhaust gas (which is directly related to temperature difference across the turbine or EGT - Turbine Outlet Temp), why would you want to reduce the input energy available to the turbine?

Let's be honest here: once the hot gas is past the valves, it's not gonna hurt nothin unless your manifold is made of cheese with a low melting point.
so then why stop with the .63...why not go smaller? I was always under the impression that less restriction in the exhaust would lower egt and turbine RPM. I thought the lower restriction would reduce load on the turbo and the engine, hopefully helping it to last longer and that lower pressure would allow for more spark advance (reducing EGT).

Also, considering that my car made target boost (15psi) at sub-4000rpm...why do I want a smaller turbine again? I want no more power, no lower boost threshold, and no more load on the engine or turbo. I don't understand how restricting the exhaust is going to increase output without changing MAP.

Also, we still have not compared from turbo to turbo, just switching turbine housings, bitch.
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Old 08-19-2009, 10:15 PM   #12
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Quote:
Originally Posted by y8s View Post
Let's be honest here: once the hot gas is past the valves, it's not gonna hurt nothin unless your manifold is made of cheese with a low melting point.

I hate to take this off-topic, but can anyone tell me the melting point of Velveeta?
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Old 08-19-2009, 10:17 PM   #13
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Here's more food for thought though, for your argument. I'm way "ahead" of detonation. I was able to puy 4* advance past MBT...so I can either add boost to hit the detonation wall or lower the turbine AR. I chose to not make a $400 mistake because I'm happy with the car.
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Old 08-19-2009, 10:26 PM   #14
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Next time my car is working I'll go out and do a 5th gear spool pull.
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Old 08-19-2009, 10:32 PM   #15
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Do the GT30 and GT35 have the same turbine wheel?
I don't think so, and therefore you can't say that the GT35 with 0.63 A/R is "flowier" than a GT30 with 0.86 A/R.

The reason the GT35 spools better may be a better speed match between turbine and compressor sections for the miata motor. IOW the GT30 with 0.86 is simply a sucky laggy turbo for the miata.
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Old 08-19-2009, 10:56 PM   #16
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A shiny quarter to anyone who can answer this question (I dont have the data so I can't):


Which would spool sooner / make more power?
GT2860RS .86 turbine housing
GT2871R .86 housing
GT2871R .64 housing
GT2876R .64 housing
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Old 08-19-2009, 11:11 PM   #17
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Woot. Subscribed for more drama. Actually, subscribed because this is the only place I have found that discusses this topic for our motors with people who sort of have a clue.

Somebody finish the extractor hood and sell to me please. I'm drunk and that is what I want right now.
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Old 08-19-2009, 11:27 PM   #18
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Quote:
Originally Posted by superslow View Post
I'm drunk and that is what I want right now.
good for you
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Old 08-20-2009, 12:26 AM   #19
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Quote:
Originally Posted by y8s View Post
A shiny quarter to anyone who can answer this question (I dont have the data so I can't):


Which would spool sooner / make more power?
GT2860RS .86 turbine housing
GT2871R .86 housing
GT2871R .64 housing
GT2876R .64 housing
if you ignore spark angle, then why waste time with this bullshit question?
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Old 08-20-2009, 12:33 AM   #20
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Quote:
Originally Posted by y8s View Post
A shiny quarter to anyone who can answer this question (I dont have the data so I can't):


Which would spool sooner / make more power?
GT2860RS .86 turbine housing
GT2871R .86 housing
GT2871R .64 housing
GT2876R .64 housing
Either #1 or #3 will spool quickest but if you can get the turbine maps then I can tell you for sure.
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