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.
http://y8spec.com/turbostuff/miata35r%20vs%2030r.jpg



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

http://y8spec.com/turbostuff/miata35...20vs%2030r.jpg


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


Discuss.

badass. no discussion needed.

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.

Still, you gotta remember that's a T3 housing, so the .82 in this case would be like a T25 1.1

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.

i too want a 500whp miata

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 whores are doing: I'm more into acceleration/drag racing than road racing. This is very interesting should I decide to go 35r in furure:eek5:

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.

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.

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.

I hate to take this off-topic, but can anyone tell me the melting point of Velveeta?

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.

Next time my car is working I'll go out and do a 5th gear spool pull.

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.

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

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.

good for you

if you ignore spark angle, then why waste time with this bullshit question?

Either #1 or #3 will spool quickest but if you can get the turbine maps then I can tell you for sure.

the 2871 has the same hot-side as the gt2860rs super turbo.

GT2860RS with 0.86 A/R
vs
GT2871 with 0.64 A/R

I'd need to see the full turbine maps. Basically look at the compressors, for say 3500 RPM and 7.5 psi, read out the RPM and efficiency. Calculate the shaft power and engine horsepower. Then, look at the turbine maps and determine if that exhaust flow at that horsepower can deliver that required shaft power at that shaft RPM. Whichever has more excess shaft power will spool quicker at 3500 RPM. Repeat this at 0, 5, 10 psi; at whatever psi there is no excess shaft power from the turbine, will be the max boost at that RPM.

P.S. my gut feel is the 2871 with 0.64 would spool quicker, but a 2860 with 0.64 would be even quicker.

The reason for that is the small A/R would generate more shaft power at lower exhaust flow rates, even when comparing the 2 compressors (and thus at different shaft RPMs).

what if I let you pick one of two conditions? all used with the same spark table OR all tuned to MBT by whatever means necessary--like a super low comp motor or water injection or 100 octane fuel.

you can't really argue the point about MBT without actually putting the .64 on and tuning it because even though it might seem to preclude running near MBT, none of us has data to prove it. so lets assume we can cheat that portion by other means in choice 2.

All those turbos share the same hotside wheel. 53.8mm 76 trim. here's the garrett excuse for a map.

http://www.turbobygarrett.com/turbob...&064turb_e.jpg

I'm with Hustler on this one. I'm switching to a bigger A/R turbine because I almost exclusively track my car and I would rather have lower underhood temps and lower engine load than 400rpm earlier spool.

Bigger A/R = less restriction = less overall heat output by the turbine = lower underhood temps = happier track car..... at least that's what "Maximum Boost" taught me.

circular logic.. hustler got his turbo originally from Corky who wrote that book :)

Well, I'm new here, so I'm not going to jump in the fray...but I do have a question:

Where are the pre and post turbine pressure measurements? That is what dictates whether a turbine A/R is too "big" or too "small."

Turbine pressure ratios dictate spool. Not EGT's, although EGT's and mass air flow dictate how much energy there is to be extracted from the exhaust.

I am running the .64 on my 2860 for my street/track car. I did that beacsue I am ultimately not looking to make 375 hp, just around 300-340. Even then, the car will be a handful on the track.

I don't feel that in the range that I will be running, with respect to power, that the heat will cause a significant enough difference to merit a larger A/R. If and when I push it further, then it may come into play more. At that point I will move up to an .86 2871, IF I need more than 325hp on the track for some retarted reason. These assumptions were made on my limited knowledge of how all of this crap works, so if my logic is wrong please call me out on it.

Garrett agrees with that line of thought too:
TurboByGarrett.com - Turbo Tech102

I may have fallen victim to my own idiocity. With my smaller .64 ar I am not hitting a brick wall for power. It may be the turbo or may not, but i have a feeling it is just because I thought I was doing the right thing for response, but it punished me severely in overall power. I should have gone with a .86 2871 to begin with.

Links to dyno sheet?

Sorry, I looked.

Details on how Y8's is a mouthy-------? Seriously, sentence #1 and #2 contradict the last sentence.

Not to cause a fuss, but I don't understand the third sentence with all the buts. Actually, it may have been infinitely more less clear if you had buts instead of periods between every statement. I am just saying that I had to read it twice and still don't know what it says. I think the first and last sentence make perfect sense though. Sorry for my idiocitiness.

:drama: Continue

These are really good threads, just the right amount of discussion vs. friendly shit-talking.

This thread, and about 1/2 dozen more like it have cemented my choice of the .64 Disco as the turbo of choice for a 300whp street-car.

What I really want is a few more people to start exploring the 300whp range on stock 99-00 motors and gather datapoints. So far, there are only a few guys who do it.

S4, exhintake, adj cam-gears, Adaptronic, 3" exhaust... I CAN'T WAIT FOR CRUISE TO BE OVER!!!

BTW this is what full turbine maps look like so one would be able to predict spoolup. Compare to what y8s posted above from Garrett:


http://upload.wikimedia.org/wikipedi...urbinechic.gif


And a subset of the above

http://www.turbodriven.com/images/tu...rinciple_g.gif

Edited for binge drinking post crapping stupidity.

Sorry, I need to clean up that last sentence. I really didn't read through it before I posted. What I was saying is that I thought the trade off for ultimate power for quicker response would be better than what it was. I am now feeling the punishment for not doing my homework and assuming my logic is flawless.

This turbo would really be great for a daily car.

There is a lot of assuming and bs in this thread. Making decisions without some sort of data and analysis means you all are tuning blind...

What are your pre and post turbine pressure measurements? What are your compressor efficiencies? What is your pre-turbo pressure to manifold pressure ratio? What data are you using to make your assumptions?

you of all people should know how important it is to question the current dogma. that's what I'm doing.

you mean you should have chosen the 2871 .86 at first instead of trying the 2860 .64 for a street car and hoping for better spool with the latter?

There are plenty of Suby guys running 3071 and 3076s with .64 A/R. You're giving up a bit of top end, but not anything a sane responsible person will see on the street. It's a worthy tradeoff unless you get a hardon posting dyno graphs all day.

Quite a few overlays between the two over on NASIOC that show spool differences and top end.

Frank

I'd love to compare them but I don't really want to spend another $500.

I think anything over 300 whp on a track is worthless unless your running wide ass tires. Atleast in a miata...:loser:

I might be willing to swap housings if someone had the standard .86, but it's kinda gotta have the wastegate welded shut.

incidentally, what's Pauls 2560 A/R?

WG doesnt need to be welded shut Matt. You can just tie it shut with some wire.

hell with no boost signal the WG wouldnt open anyway just swap and run the shit y8's

Remember the "GT2871R" also comes in 3 different compressor trims.

Anyone with one of my manifolds gets my price on TiAL stuff. At least for the foreseeable future. ;) I did order a seperate .64 v-band turbine as part of the buy in.

EDIT: I really mean you pay retail/lowest allowable price and pay less for the manifold/downpipe...yeah.

Paul's 2560 is the standard .64, I think the only way the smaller gt25 turbine comes in.

I can't find it anywhere.

Wrong

What I mean is that since this will be prodominately a track car, I should have gone with the .86 2871. If this was a street car, then I think the .64 2860 would be perfect.

Lemme see if I can find it in my email.

Or get a bit of the best of both, with a 0.64 a/r 2871 :bigtu:

judging from the dyno bleow, you and most others in this thread are wrong. Not shit talking...it just looks like the big turbine housing is prevailing. I lucked out.

At constant boost maybe, but what about flattening the torque curve by raising boost at higher levels? The bigger compressor wheel will keep the discharge air temperatures down (efficiency) and the added boost will help offset the higher flow turbine losses at higher RPMs. I plan on trying this myself. 225 ft*lb or so carried to as high an RPM as possible should be great. 225 ft*lbs @ 7000 RPM = 300 bhp. 225 ft*lbs @ 8000 RPM = 342 BHP (about 300 RWHP). Should be able to do this with a built motor from what I have seen.

There is no right answer here, just a matter of choosing one's compromise.

I'm no engineer, but it looks like the wrong answer is the intake plenum because a few of us are on a wall.

I'm working on the intake right now; I'm removing VICS and opening up the plenum. The top half is done, and I am working on the bottom half now. Not as good as a full-up custom intake with a larger throttle but cheaper and easier.

^I'm in for data on this. I don't think anybody has had a direct before/after dyno plot for gutting the 99-00 manifold.

I will most likely be gutting my 99 intake manifold after i hit the dyno for shits and giggles. Will create a thread if i do.

We may soon. I was going to do the same thing ZX-Tex is doing, but if he is doing it soon then I will wait.

How long do you think it will take? I was going to try to do it within the next few weeks.