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Old 01-10-2009, 11:44 PM   #41
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Hmm. So I'm reading what I can find, but I'm not finding any badass articles on google yet. But from what I've gathered, older 2 valve engines do make more power running ~12.5:1 where newer 4 valve, fast burn engines make more power running a bit leaner, varying from 13-13.5, many using the 13.2 number. All of this is at atomospheric pressure though.

So here's what I'm thinking now. Now I ran this engine at 190 kpa a few times at 12.5:1, so I know it will do it. (and OMG it pulled like crazy!). But I want to keep it safe for now. So I'm gonna probably tune my VE table to this. Hopefully running a bit leaner at low boost will help it not feel like it "falls on its' face" when I first go into boost, as it does now.


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Old 01-11-2009, 12:11 AM   #42
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pat I'm liking that map. aside from the earlier discussed idle area of course.

next see if you can find something about leaning slightly as RPMs rise. and conversely richening up the low rpm/high load areas relative to the rest of the map. this is due to knock resistance changing with RPM. (it's also addressed some with spark)

but I can't search now, got a gf and dvd waiting for me!
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Old 01-11-2009, 12:17 AM   #43
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Quote:
Originally Posted by y8s View Post
abe's nuts running 15s at 100kpa! Though Ben does run that lean up to about 80 kpa (Ben?) I seem to remember.

a google search turns up the 13.2 number various places.
I agree with Abe. Stoich at 99kpa and moderate RPM is just fine. There's no reason to run so rich in vac. Screws up your high speed cruise economy.

Think about it. When you stab the throttle, if anything you're only going to quickly blaze through these cells. And as you're going through them, you have accel enrichment adding extra fuel.

FWIW, I watched my car make more power on the dyno in high 11s than mid 12s. I did not believe it until I saw it.

Can't wait to get the new car on a load dyno.
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Old 01-11-2009, 01:25 PM   #44
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Seemed logical to cross-link this
https://www.miataturbo.net/forum/t29956/#post351847
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Old 01-11-2009, 04:00 PM   #45
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Here's my latest AFR table. Very similar to the last one I posted. I tuned the car some on the table above this one and now it's a seamless transition going into low boost. It feels "normal", like I just pushed the gas pedal more, rather than boost building. Doesn't fall flat like it did running 11:1. Gonna put this table on later and tune some more. But overall, it's getting a lot better.

EDIT: Whoops, for got to post the table...

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Old 01-12-2009, 03:59 PM   #46
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glad it's workin' for ya. yeah, like i said, i may run 12.5 at the drag track, but change it back to high 11's map before i leave. of course it may run fine and be great at 12.5, but it leaves no room for error. like a bad tank of gas, or big change in temp. or altitude or any little thing that can happen. good luck
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Old 01-12-2009, 04:06 PM   #47
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Tuned it to the map above. Yeah, it's awesome. Power at low boost is much better. I did a pull today on the highway in second and it broke the tires loose around 50mph. I laughed out loud.

Exactly though, I don't want to get too aggressive and have a little something get off and detonate. I feel pretty comfortable with how it's tuned right now. I may lean it out a spec on the upper boost cells in the future, but not before I completely redo the fuel system. Because as of right now, I loose fuel pressure around 50% duty cycle on the injectors. I'd hate to tune it to run 12.5:1 on a day when it's pumping good, and then one cold day it doesn't hold pressure like before and I run too lean.
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Old 01-12-2009, 04:18 PM   #48
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hey pat, I felt like goofing around and adding a little fuel in my super-atmospheric region (90kpa and up) and I dont know if it's the mixture or the 30F air temps but the car seems to pull harder in the midrange as boost is coming on.

it's now basically a ramp from 13.4 at 90 kpa to the mid 11s in the 200kpa region.
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Old 01-12-2009, 04:37 PM   #49
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That's good to hear. Basically like the table I posted, but a bit more linear? I think this AFR table is gonna be a keeper. Also, you might appreciate this:

I cranked the car today at 30*F ambient and it idled fairly well at 12.5:1 cold. First time ever it's done that. I think having the spark advanced like I do makes all the difference though. Idling around 22* around 900 RPMs and 12.5:1 and it was solid and smooth. So who knows, maybe I can lean that spot out a bit more. I guess if anything I could lean it out and just dial in a bit more warm up enrichment. But it has been my experience that running high 12's at 100kPa from 400-1400 ish is the best AFR for power and smoothness. Any leaner and I can't get enough spark in there for good grunt, any richer and power falls off.
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Old 01-12-2009, 04:49 PM   #50
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who knows. my car idles fine at 14.5:1 and 12 BTDC. and plenty of vac.
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Old 01-14-2009, 01:49 AM   #51
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during enrichment 12.5 at idle is fine. i think that's where i'm at. but once warmed up, it should be 14.5-15.1 for sure. same thing when your just cruising (high vac.) at any speed. reason being, that is where your car spends the most time everyday. if your car is too rich in those cells, the extra fuel will wash your cylinders out and you can scour the piston walls and all sorts of other terrible things. i've seen a car that was tuned on a dyno before and never adjusted for cruising/light throttle conditions. his motor lasted 2mos. another was a rotory. he took the ''rotory's like to run rich'' saying too far and killed his apex seals in a few months. those are extreme examples, but you can be ''too rich'' contrary to what any women may have told you! lol
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