JasonC SBB

Anything that improves naturally aspirated torque at 3000 RPM will help spoolup at that RPM.

For example:

- more displacement
- VVT
- compression ratio

k24madness

iTrader: (6)

First step IMHO would be a APEXI AVCR EBC. Sav is correct about the benefits of an EBC vs MBC. What most don't know is gain is set to avoid spiking in top gears. In lower gears you would want more gain for better boost response. The AVCR is the only boost controller (that I am aware of) that allows you to adjust boost gain by gear. Just think of how a turbo is loaded differently in each gear. That's why being able to adjust boost control by gear is important to someone like you.

On the other hand if you don't have the cash to buy a AVCR or want to deal with it try using a Greddy Profec B. Crank up the gain for the autocross runs and set it back down to normal for street driving.

Rocwandrer

Ebc/mbc: I currently run ebc with the boost threshold set above the actual boost threshold to just barely not overboost in second with the current spool characteristics. I have the other parameters also set for second gear. Since I'm never bogging 3rd on course, this works out ok. I just lower the boost threshold low enough so it is laggy but safe in 4th and 5th.

My plan is to run a ball and spring mbc with the bleed blocked and a check valve'd back bleed passage referenced to manifold pressure. This way, I get full wastegate actuation as soon as the ball leaves the seat. I'm having trouble finding a little check valve with a low enough cracking pressure, but I'll make it work.

bov:

I've thought about this a bunch. I'm less concerned with boost recovery during a shift (just because it isn't bad now at higher rpm) than I am with going from off throttle while cornering to wot through the apex. I'm not sure if I'd even see a gain in that scenario with no recirc valve.

left foot brake pre-spooling:

This does not work well with tight corners, rwd, lsd. It ends up altering the line enough to be a net loss loss compared with living with some lag. If I could coordinate ebrake with throttle well enough to avoid the understeer that comes from the front brakes engaging, maybe. I'm not interested in going down that road rather than fixing the car, though...

meth/water injection:

Rules don't allow meth. I plan on a small water to air system supplemented with water injection.

intake piping:

Anybody think can get away with smaller than 2" od charge piping (sweeping mandrel bends and so on)?

Rocwandrer

efr turbo:

That's a lot of money compared to a turbo i already own. Just how much faster "Just above boost threshold" spool are we talking?

JasonC SBB

AEM does it too.

baron340

iTrader: (5)

If you are you going to convert over to water/air intercooler, heat soak may be a problem. I'm running frozenboost's type 20 core and their small sized heat exchanger, and I don't think it's enough for auto-x. It starts to get soaked by the time my runs are over. On the street or in the mountains it's never been a problem though. Either a larger reservoir or heat exchanger would probably fix this. I also would advise against smaller than 2" piping. It will choke up top. That said, I love my water/air system. My charge piping is all of 2' long, and response time is absurd, but I'm also using a teeny turbo.

Leafy

iTrader: (1)

You want the EFR, barring that, you want a 2 liter stroker and a turbo just big enough to hit your power goal. The only turbo miata I drove was a 2 liter stroker with some sort of turbo setup from FM, no idea on the size of the turbo supposedly it was making 300 wheel. There was zero turbo lag. Some of that could be contributed to the fact that he has that super rare (and horrible) adjustable australian helical diff and a rear sway bar, so I spun the inside rear coming off of every corner.

Or if you're super money bags. Beyond the Dyno: Rocket Anti-lag Teaser I know how to make this work and it'll cost you between 2 grand and 8 grand depending on how many prototypes it takes to get the aerodynamics correct in the rocket.

Rocwandrer

You don't have a turbo'd Miata?

There will be no getting into the engine internals this year. There will be no substantial displacement changes. There will be absolutely no FM parts on the car (nor anti-roll bars).

I also know how to make that work, and I don't think it would cost anywhere near that much. It is just some basic engineering math to figure out the right geometry. The basic principle is that a nozzle has a high pressure, low velocity region and a high velocity low pressure region, and by doing the combustion just after the peak velocity region, you don't get backfeeding of your flame front. It would require a special bypass valve actuation routine, two exhaust gas capable 0 cracking pressure check valves (eccentric butterfly in a rectangular section of pipe will do), and "rocket" fuel injection that is a function of engine rpm, turbo rpm, and tps. The tricky part is mapping the likely turbo speed for a given wot condition, and then using closed loop control to achieve that speed any time als is engaged and the tps is low.


I'm hoping to make (hopefully minor) compromises to total area under the curve of interest and avoid needing that sort of ALS, and also avoid needing multiple turbos.

Leafy

iTrader: (1)

The electronic control takes a bit of thought but it shouldnt be that difficult an MS3 should be able to do it but would have to be separate from the engine control. Or you could do it with a pectel SQ6. There shouldnt be any check valves in the design since its basically a gas turbine that someone left the shaft out of. But the expense of prototyping is that the combuster needs to be made out of inconel for it to have any sort of longevity.

Braineack

iTrader: (62)

why not focus on things that actually improve spool/low-end?

fooger03

iTrader: (2)

Run variable pulsed N20 off of a 4d map that uses TPS, RPM, and MAP as inputs?

Leafy

iTrader: (1)

N2O is also not legal in his class.

Braineack

iTrader: (62)

why not focus on things that actually improve spool/low-end?

miata2fast

iTrader: (2)

/\ Alzheimer's?

Braineack

iTrader: (62)

Repetition or rehearsal is necessary for information to be stored in short-term memory or retained in long-term memory. Especially when additional unrelated information is presented before repetition or rehearsal is complete, it interferes with the brain’s ability to transfer the original information to memory.

Rocwandrer

One of the check valves is needed to reduce the effective exhaust volume upstream from the turbo when the system is not in operation (this also prevents flow reversion in transient pressure situations where no fuel is being injected). The other is needed as a safety against engine fire. Inconel isn't necessary for my application (less than a half second of operation perhaps 4 times in 50 seconds, then minimum 5 minutes of rest time.) I've got other ideas for how to implement such a system as well, but at the end of the day, I'm trying to start simple.

Rocwandrer

The compressor efficiency island is above the max pressure ratio I plan to use. Still think it is the best choice?

I'm considering the EFR, but also thinking of a lightened billet turbine wheel upgrade for the gt2560r (claims to slightly improve boost threshold, dramatically improve spool, and slightly improve efficiency at high flow rates.)

Leafy

iTrader: (1)

If the 6258 efficiency island is above where you're running you need a much smaller turbo than the one you have now.

Rocwandrer

That's where I started. I almost bought a brand new eaton blower for $250. I was designing brackets. Then I started doing the numbers.

I couldn't find a supercharger that would make 10 psi at 3000 rpm and also make 10 psi at 7000 rpm. I didn't look at anything crazy expensive, but the usual suspects have poor volumetric efficiency/effective displacement ratios at low rpm. An eaton blower will only make about 6-8 psi (depending on which one) at 3000 rpm if setup to make 10 psi at 7000 rpm. A rotrex needs a calibrated restrictor plate in order to make boost at 3k without blowing the engine at 7k, and the adjustment factor isn't linear, so you can't have constant boost without using a wastegate on the charge air. The response time with with a belt driven blower and a compact air to air intercooler is on the order of 300 ms to full boost at 3000 rpm, and only slightly faster at higher rpm. The thermal efficiency is lousy on the external compression types, and the price is lousy on the internal compression types. None of them are going to make as much hp in the mid-range as a decent turbo setup, given the same safety factor against engine failure.

None of that sounds appealing when compared with a more advanced turbo setup.

Leafy

iTrader: (1)

I dont think you were looking at the right blowers, the M62 on my last car (2.2 liter engine) would make 10-12 psi from pretty much idle till 7k. Of course because the cams werent right, the tune was as good as you could get with alpha-n, and the port flow sucked, it only made 226 hp and 210 ftlbs. There was no discernible delay between the the throttle and the power.