So here is what I have been playing with most of this afternoon. (yes the Mrs is getting pissed)

I took your advice Hustler. I played with the 2871R and the 3071R compressor and turbine maps from Garrett. The green lines are the 1.8 and the red lines are 2.0. The low end is at 5psi and the high is 20 psi. Not that I plan on running that high but I used it to push the upper limit as a cushion. The 28 series compressor is a nice fit for my goals but the turbine section looks small.

I am still a little confused about the turbine sizing. Sixshooter you have any tips here. My guess is the higher I am above the line the more power to run the turbine, but wouldn't that also mean there is more restriction?

Yes I know the map sizes are not matched. When I click on the map another comes up. I guess their hotlinks are out of date.

i lol'd

Ok, this is for you guys that told me so. I used the 2860RS at 2psi to 18psi. Starting at 3000 RPM to 7200. I will be calling Mr. Bell to talk to him about the S4 and 2860. It looks good on paper but I don't think it will make 350 at the wheels.

that looks pretty good. 15-18psi is the turbo's sweet spot looks like

i have an s3 with a gt2860rs and a ~1.9l (1mm over)motor about to hit their dyno next week. Looks like my 14psi spring is right in the heart of the sweet spot of that map. I guess corky recommended it for a reason. Hopefully the slightly extra displacement will get the hot side spinning early enough to make me smile.

Hmmm I have been playing with this spreadsheet and it will compute the flywheel HP. I see now that to make that kind of power I will need to be in the 20+ psi range, with a stroker.

Man that V8 is not looking so bad.

Thanks guys for putting up with me.

you are beginning to see the light:giggle:

You need to stop posting and start reading. Read and think. Repeat.

I want a v8 too. But I need a/c. If you do look further into it. Check out Cold air productss in Fort Worth Texas. The have every brack imaginable for a/c on 350's. I bet they have a bracket a pulley setup that will bolt and play right up.

Regarding the compressor side:
Your operating range will be roughly between those two lines you plotted depending on where you limit your boost. The left line being to the left of the surge line on the map indicates that you won't be on boost at 3000 RPM but probably will be starting by 3500 or 4000 if the turbine gets going well by then.

Regarding the turbine side:
I'm curious where you came up with your turbine graph points. They don't look right. I came up with these in red.

I was a little generous with the EGTs on the low side. And you weren't up in the PR's on your graph points where 18PSI is. Did you use lower numbers than on your compressor map?

Anyway, as you can see from the lower line, you aren't going to get boost at 3000rpm unless you count about 2 or 3PSI with the .64ar . You will start seeing enough flow and pressure to start doing work as you move vertically up the graph (increase exhaust flow due to RPM rise) and approach the max efficiency line.

You will see work accomplished before you reach the line and start making some boost depending where the same moment falls on the compressor side map also. And after you reach the line the wastegate will eventually open somewhere above that line to relieve excess gasses that the turbine doesn't need (It is already at or above max efficiency at that point and doesn't require more to do its job). If the wastegate didn't open you would create excess backpressure and would lose power.

You see the .64ar reaches the max efficiency line (comes on boost) earlier than the .86ar. Thats where you determine how many RPMs you want before you start making power. Looks like about a 3.5lb. to 4lb per minute difference. An intrepid man could figure out how many RPM's those lbs./min would equal with a little math.

P.S. You want to be above the line to use all of the turbine. That's part of why we use wastegates.

Sixshooter, Thank you. I looked on the garret site but they only discuss the compressor in detail but nothing on the turbine. I didn't know if I needed their plotted lines above below or in the middle. I got it that line is the work line required to run the compressor, below it and it wont run above it and you are over spinning the compressor. The wastegate is the governer. I am thinking if you are too far above the line you have boost creep issues if the wastgate cant bypass enough heat.

I used the excell sheet I attached in an earlier post. For the compressor I used lines 43 and 54. For the turbine I used lines 84 and 90. Line 84 is with the waste gate open. I was not sure if I should use it or line 82. I had so many maps and using different rpm, displacement, and boost pressures I am sure I got screwed up. Also, I am not sure about some of the data used.
EGT I used 1600
ambient 85
Manifold temp(boost after cooler) I used 100, this has so many variables, high boost = high temp, dont know where to put it. Could be 100 could be 250?
Turbine outlet pressure, 5psi

I thought about the v8 some more last night but I'm still willing to do the turbo over the V8. Call me stupid I guess.

It's not stupid. Turbos are fun because they are mechanically interesting. I've already done the big v8 thing so much that I want to do something new and interesting. There is much to learn here and that keeps it fascinating.

I used an outlet pressure of 1psi on the 3000rpm #'s and 2psi on the big end. If you are running a 3in downpipe and a suitable exhaust, you should be able to keep that down pretty low.

I used 1600 at the top rpms. I think I used a lot lower egt's on the lower rpm stuff, though. Under 1000. There's lots more time for heat to dissapate at lower rpms, and you aren't putting as much fuel and air through the engine either.

Manifold (Inlet air) temp wasn't a factor in the formula I used. But I know it effects air density.

Don't worry about boost creep. If you buy the right size WG, and have it plumbed right it'll never be a problem.

You need the turbine to get above the line early enough to be useful. If you were sizing it for a generator or a pump engine that worked at a steady state rpm all day, you would aim for a point right on that line or just slightly above. But our engines work across a broad range of rpms, so WGs were created to allow us to use the wide range effectively. Don't be afraid to be well above the line. It is where you should be. Be afraid to be below it for too long. Nothing happens down there. Nothing.

I think you should look at doing a sr20det swap or a s2000 motor swap its a 2.0l that makes 250hp n/a and with a gt30 u will make close to 420whp. The v8 swap is nice just more weight gas and less room in the engine bay

True......not true......not true.

190lbs total gain in weight. 2/3 of that over the front wheels and maintaining a ~52% / 48% balance.

Corvette's get over 30mpg on the highway anyway. Same motor, with less weight to push in the Miata, can only net you better mileage than the Corvette.

I'd say there is no less room than a turbo miata with all emissions items and cruise control.

When I was talking about more weight and bad mpg I was talking about the older v8 the cast iron bocks. If you go with an ls2 ls3 then yes mpg is not bad and the weight is less but the s2000 motor is a motor that make a lot of power stock for a 2.0l 250hp and he could still go with his turbo set up and make 420hp with stock internals. Plus the s2000 engine is aluminum not cast iron like the Miata blocks so it’s lighter.

dude you're completely missing the point. what about the s2000 engine would be any more appealing than a ls1 v8? its got no torque, completely maxed out from the factory, and the only real way to make power on it would be with forced induction. It actually cost a lot more than an ls1. If you go that route might as well just build a miata engine and boost that: way simpler/easier and cheaper.

It is true but its some thing i have never seen done and if he wanted i know were you could get a whole s2000 for 2500 my friend totaled the car this winter. every thing but the frame and body is good.

I like that you are searching the forum and reading threads, but don't bump 3-week old posts.

Yeah, hopefully dohcpanther doesn't get email notification on here or I may have to log-out for a while.

That's a giant +1.