TPS based AFR map for better mileage (?) - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-20-2015, 04:02 AM   #1
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Default TPS based AFR map for better mileage (?)

Hey,

I started testing this AFR map in order to improve my 15mpg...

This map is great, it will not shoot 11.5 when only "accidentally" getting in to low-mid boost for a sec or two, it will go for 14.6, only near and @ WOT it will go to 11.5.


My question:

Running 7.5psi of boost for a few seconds at 14.6:1 AFR (knock free) good ? bad ? do ? don't do ?

The traditional AFR map (MAP based) will go to 13.5-12.5-11.5 anywhere from 100kpa and up... so 150kpa will be 11.5, even if it was for a second or two - wasting fuel ?

Thanks !


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Old 09-20-2015, 04:09 AM   #2
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I've run 14:1 at 100kPa, 13:1 at 150kPa with my GT3271 setup. This actually made it spool a lot better and drive much better. It still went to 11.0 once it got around 200kPa, and high 10's by 250kPa.

Whether or not you can Pull off running lean at low boost really depends on the setup. Copmression, AITs, fuel octane, how safe/conservative/aggressive/ignorant your tune is, how equal your injectors are, is the motor carboned up and old, AITs, and the list goes on a lot.

If you don't know what you are doing, don't try to run lean in boost. It's a fantastic way to break stuff fast.

For reference with my SC setup on 93 octane, it made better power by throwing the fuel at it FAST and adding. I was running 11.0:1 by 150kPa but this allowed me to run 2-3 degrees more timing and it really made a difference in low end torque. If I ran 14:1 I had to pull 3-4 degrees to get it to not knock, and then it was slower. No driveability/spool benefit (no turbo) so it stays rich in boost now.

Also you need to make it load based, not TPS based.
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Old 09-20-2015, 04:12 AM   #3
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If it does not knock, could be other damage I'm not aware of ?
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Old 09-20-2015, 04:13 AM   #4
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Actually, just checked, this is how the car was tuned on pump gas before I switched to E85.



If you wanted to modify that for turboage, I'd change 11.0 to 11.5, and have it to go 11.5 by whatever your target boost pressure is, interpolate between of course.
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Old 09-20-2015, 04:14 AM   #5
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Quote:
Originally Posted by elior77 View Post
If it does not knock, could be other damage I'm not aware of ?
It could not knock now, but knock later. You're a lot closer to the edge running lean. Lean will drive up EGTs a lot, which is great for spoolage but harder on exhaust valves.
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Old 09-20-2015, 04:17 AM   #6
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I try to get better mileage, it looks like a good way, TPS based AFR.

I run a very small turbo (53mm compressor wheel), every tip on the gas pedal will get me into boost, and then run 11.5...

With this table I can get in to low-mid boost for a few secs and run 14.6 - saving fuel.. (?) - it happens a lot... (maybe I need a bigger turbo - 60mm)

Last edited by elior77; 09-20-2015 at 04:50 AM.
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Old 09-20-2015, 04:19 AM   #7
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Quote:
Originally Posted by elior77 View Post
I try to get better mileage, it looks like a good way, TPS based AFR.

I run a very small turbo (53mm compressor wheel), every tip on the gas paddle will get me into boost, and then run 11.5...

With this table I can get in to low-mid boost for a few secs and run 14.6 - saving fuel.. (?) - it happen a lot... (maybe I need a bigger turbo - 60mm)
Mazda BPs are not modern direct injection engines. If you try to tune it like it is, you'll break it. I promise whatever fuel you save won't justify the cost to fix your motor.

MS3 has time based fuel enrichment, you could play with that to find a compromise.
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Old 09-20-2015, 06:38 AM   #8
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You need an MS3, which supports blending AFR tables 1 and 2, based on TPS.
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Old 09-20-2015, 10:02 AM   #9
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Whoa, didn't know it could do that. It's funny cause I've been getting about 16 mpg now, and was thinking about how to get better mileage
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Old 09-20-2015, 10:45 AM   #10
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You don't need tps based Afr. You need a not shitty tune. I hit 32mpg on my last trip to California. Don't be a shitry driver. I'll post my AFR map soonish.
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Old 09-20-2015, 11:02 AM   #11
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Actually op, why are you running 11.5 at 100 kpa? I'm running 12.8 or so at 100 kpa, and that's still too rich. Keep in mind 100 kpa is just starting to become boost
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Old 09-20-2015, 02:33 PM   #12
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<p>I leaned out my cruise range (40-50 kpa &amp; 3k-4k rpm) to nearly 16:1. I was getting ~25 mpg average. This was also with RX7 550cc injectors. I bet with the gt500's I have now I'd get much better mileage.&nbsp;</p>
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Old 09-21-2015, 11:32 AM   #13
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Quote:
Originally Posted by aidandj View Post
You don't need tps based Afr. You need a not shitty tune. I hit 32mpg on my last trip to California. Don't be a shitry driver. I'll post my AFR map soonish.
Something that came up in a facebook discussion, the amount of fuel that equals 14.7:1 at one spark degree won't be the amount of fuel at another, so it could be that part of the problem is ignition timing and possibly fuel timing allowing you to run a smaller pulsewidth of fuel at a given load/rpm.

Just a thought experiment. I'd be interested to see what your timing is at in cruise.
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Old 09-21-2015, 11:44 AM   #14
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Yeah.... you just need to tune and maybe change your driving habits a little if you're worried about MPG on a turbo miata.

My last turbo Miata did a best tank of 35.3mpg running a DIYPNP. Typically averaged 33mpg highway, 31mpg combined.
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Old 09-21-2015, 11:51 AM   #15
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how about just don't cruise leaner than 15.5 AFR?


that map posted above (i havent read anything) would suck dick holes for MPGs.
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Old 09-21-2015, 11:51 AM   #16
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Quote:
Originally Posted by aidandj View Post
You don't need tps based Afr. You need a not shitty tune. I hit 32mpg on my last trip to California. Don't be a shitry driver. I'll post my AFR map soonish.
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Old 09-22-2015, 08:02 AM   #17
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TPS based seems to work great, when you leave a stoplight or when you accelerating mildly and get in to 110-150kpa for a few seconds, afr will not deep to 11.5 it will stay at 14.6, but when I WOT or near WOT I get to 11.5.

I cruise @ 38deg that helped get my EGT back to normal, if I get 15mpg I guess I must tune and lean where possible.

All is knock tested and cleared.

I would love to know how to get 30-35mpg (!!)

I run a small turbo (TD04-13C), 460cc injectors, 6spd trany, 4.11 lsd dif, TOYO R1R 205/55/15 tires.
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Old 09-22-2015, 08:29 AM   #18
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why not always go for MBT
when you are cruising, you need ... torque
The farther you throttle is closed for that torque
the less fuel you consume

That's my theory, but I could be wrong
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Old 09-22-2015, 09:34 AM   #19
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150kpa @ 14.6:1 AFRs, what could possibly go wrong?
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Old 09-22-2015, 09:36 AM   #20
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Can create AFR targets based on load and RPM. Chooses to use TPS% instead.


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