MPG- give me some input please
 

Hey,

I would like to know if my fuel consumption is normal.
Lately I run on low boost 7-8psi in order to see if that will help my mpg.
It almost made no change, I run 12-17mpg (5-7km/liter)

Normal ?

This is my AFR auto generated table:
https://www.miataturbo.net/attachmen...1&d=1400844469

What do you think ?

:party:

Thats very low MPG. Seams rich in the middle. Could be closer to 15-16.

first off, you mean mpg right? cause even a semi truck doesn't use 17 gallons per mile

second, your target afr table means nothing to us, you'll need to post logs or tell us what its actually achieving.

third, what fuel are you using.

lastly, if you're not getting the same mileage driving it normal as you did when it was unmodified, then you either have a problem or your tune sucks. at worst it should be within 10% difference. that's assuming you're not constantly WOT and in boost

Please stop posting lazy uninformative threads, or we'll stop helping you. I realize you're foreign, so there's a language barrier, but you'll still have to try harder and provide more info.

I got 23mpg on my last highway cruise and it was very spirited... (cruising 4-5k)
Run ~15.5-16 at cruise on HWY.

Car is still very untuned so these numbers should get better

MPG fixed.

I will post logs asap, but this table was used by the autotune so it represent quite good the actual AFR - I see my AFR live when I drive and it is the same as the table.

I use 95 (RON?) fuel.

I use a small turbo TD04-13C when I'm at 100-120kph I'm in boost (or very close to) so I can not compere it to the unmodified MPG.
When I disconnect the actuator I get close to normal MPG.

I'm sorry to understand that you think this is a lazy uninformative post, I disagree.

If some info is missing I would be happy to give it.

This is my first turbo project, I have no previous background in turbo charging or mechanics (I'm an IT guy) I do my best...

:party:

logs asap.

If disconnecting the wg nets close to OEM gas mileage, then your tune might not be that bad actually. Looks like you're just dipping into boost WAY often with that tiny turbo. Also post your timing map to make sure you're not retarded too much and giving up efficiency.

I meant no disrespect with my "lazy" comment, just frustrating because I'm genuinely trying to help you out here.

My ignition map:

https://www.miataturbo.net/attachmen...1&d=1400864003

Thank you for your help.

That ignition map looks pretty average to me. Is your turbo really that small that you are just constantly sitting in or near boost even while cruising? I am getting around 26mpg combined with mine and I am using the tiny stock IHI turbo.

Yeah, not a bad spark map. You can bump up the 35-80kpa rows to 40 or closer to it if you want, but otherwise not bad. So far I see nothing bad with your maps. If you're in boost when at steady state cruise like you say, then yeah that's gonna eat gas like crazy

I beat the crap out of mine and usually rev it in the driveway until it's warm. I still get 19mpg regularly. This is with cruise cells tuned, as others have said, to 15.5-16 afrs.

Here's what you do:

Go out for a drive on the freeway. Get in the slow lane and go 50mph. Put the car in 5th, or 6th if you've got it. Drive for 10 miles, paying attention to your RPM and map readings, remember them. Then go to your fastest cruising speed. In Oregon we don't have speed limits over 65, so I'd probably do this at 70mph, but your results may vary. Again, drive 10 miles at this speed, paying close attention to your rpm in top gear and map reading when CRUISING (aka: not the readings when you're letting off if you accidentally go too fast, or boosting back up).

Find the 50mph numbers on your afr target table, and draw a line straight up at the rpm, and horizontally right at the map. With the 70mph (or whatever) numbers, draw a line straight down at the rpm and horizontally left at the map.

Make all cells that fall in the box created by these lines equal to 15.5-16.0. Tune for these. If you have an hesitation or you're worried about the transition into the box, or out of the box (and/or if you have a giant MSII or better target table), you can reduce the boarder to a smaller number.

Come back with results.

P.S. Your signature is a lot better than most newbs, but make sure to ad your car's year and engine type. 17mpg with a 1.6t is much worse than a 17mpg 1.9t.

he's got a 1.8 nb iirc.

another reason I asked for logs is cause I want to see if he really is in boost at low throttle accelaration

Is that the highest octane available in your area? I would put 97 or 99 RON in your car if it is available. Depending on the blend, 95 RON is somewhere around 90 AKI octane. 97 RON around 92 AKI and 99 RON is around 94 AKI.

Keith

Way too rich. As said a target afr map means nothing however i'm assuming your real map is fairly close. That said...

1600-3800 up to 64kpa tune for 15.2. Your location is unknown however in the winter i go up to 15.5

Between 1600-3800 change 78kpa to 14.3 , 92kpa to 13.5

Also a small turbo wont make it so you're always it boost. Doesnt work that way. That depends on your throttle / rpms. Yes it spools faster than a large turbo however if u find ur self at 120kpa all the time in low rpm then you need to ease on the throttle and keep it in a higher rpm. An engine at 3-4k rpm at 70kpa will give u a better mpg than lugging it at 120kpa at 1500 rpm on every green.

Like that ?

https://www.miataturbo.net/attachmen...1&d=1400911430

I drive a 1.8 1997 NA.

Winter here is 15-25C and summer is 30-35C.

I will get some cruising logs today hopefully.

Its probably worth a shot, but honestly .3-.5 of a point of afr wont' make much difference, especially in cells that get swept through real quick and usually are bouncing around to find the target.
Your normal hwy cruising should be out of boost, and it should be in the 30-40* range, and it should be in the 14.7-15.5 range. Your idle should be in the 14.5-15.0 or so, and your startup/wue should not be pig rich.

just some general pointers

I can tell from older logs that my cruising is @ 60-70kpa.... @ 3000-3200rpm

I enriched my cruise map last gas tank was at 15.8ish, went down to 15.2. Went down from almost 25 to 23.3

Yes, that should help. Keep it less than 75kpa while accelerating and shift at 3500rpm.

Got my logs, this is after the AFR table change and autotune that, I can see that the AFR is very close to the table.

btw... my 3rd gear started knocking this drive.... very calm drive.... :\

3rd gear started knocking? Pinging?

tak tak tak tak.... only 3rd gear....

What wideband are you using? When I had an LC1 it would sometimes go out of calibration and read leaner than the mixture really was. It would cause the ecu to dump more fuel in and result in shitty mileage.

I use Spartan WB from 14point7.

oh wow....I have a theory about your issues now

I get 20-22mpg with a 5 speed/4.3 diff and when it gets driven, it gets driven hard. :giggle:

I use 5 speed with NB dif - I think it's 4.1, how can I make sure ?

My speedometer shows around 10kph less the gps speed, with the original dif it was 10kph more then gps speed.

I'm trying the best I can to get a better MPG, I don't see much improvement, even with low boost (>10psi) and 16:1 AFR cruise.

17.5MPG would be an achievement.

I noticed that my normal cruise is 60-70kpa that is a bit high, if I under stand correctly.

Anything I can try more or that is it with the current turbo combo ?

My current AFR:

https://www.miataturbo.net/attachmen...1&d=1416683765

That's a very high kpa for cruise. There is something wrong.

I know you'd think leaning it out like that would better your fuel consumption, but perhaps you should post your spark/ all of you enrichments. I get 29mpg and no less than 24 when I am mad at life and take it out on my car for a week.

Log:
https://www.miataturbo.net/attachmen...4_18.25.32.rar

You can see that my cruise 2700-3200rpm is above 60kpa

You can typically run 30 degrees up to 100kpa. Your high boost high rpm cells have too much timing. You don't need more than 14 on the top row.

After reading around about Volovs S70 (my turbo donor) mileage I think 18mpg is a normal number...

What is it's what it is...


Bigger turbo ?...

That's not really how that all works.

Will it not give any idea of mileage ?

You're wondering if the gas mileage a Volvo S70 gets has anything to do with your Miata?

I use its turbo

I use a radiator hose from an Escalade. Does that mean my cooling system could cool a 6.2L?

Uh, but you don't use it's manifold, down pipe, engine, injectors, intake, exhaust, engine design, head design, ecu, weight, or ANYTHING else related to the Volvo.

You have a LOT to learn if you think you can compare the car you've taken your turbo from to your Miata for mileage comparisons.

Just using the turbo won't give you similar mileage as the Volvo. Your fuel table and spark table need to be tuned properly and you will get decent gas mileage. On my 94 on the interstate I could hit 32mpg if I stayed out of boost.

When you go out shopping for a turbo one of the turbo specs are "supported" HP.

If I understand right: HP=air+fuel+spark.

The turbo HP spec is given without any consideration to your car/build.
The turbo HP spec is based upon the turbo capability of moving air, and for any given air volume you must apply a specific amount of fuel.

The air volume and fuel volume will be quite the same for any given HP on any car/build with the same turbo, this is way you can calculate your injector size without any consideration of the car/build.

There for I think it will be safe to say that for a specific HP output you can calculate the fuel amount that will be needed hence mileage.

Of course I'm talking rough numbers and just a rough estimation of mileage with a specific turbo - combined mileage - boost and no boost.


(Don't kill me)

Curly's comment still applies.

There is a general marketed "hp number" that a turbo can support, but it's not anywhere near exact, and it's not the same for every car. First of all, the simplest way to bust this is the neglect the engine all together. Weight, driveline efficiency, brake drag torque, tire rolling resistance, aero drag, etc all play into fuel efficiency.

On to the engine. If you simplify everything, as simple as you possibly can, you still have different sized motors. This immediately means the VE is off. Then you start to factor in bearing drag torque, piston ring friction, and all other mechanical frictions. Now think about head flow, intake flow, exhaust flow, exhaust pressure differential, and all of the efficiency factors for literally EVERY part of the engine. Every flow characteristic, friction surface, injector spray pattern, spark burn completeness, has an inefficiency, that will vary engine to engine.

So, all in all, you can create assumptions of "this turbo may achieve better fuel efficiency than this turbo, given the same motor" because you are changing one main factor of the system. You cannot assume anything based off of the same turbo on different car, unless you can calculate the differences in everything I mentioned above, and more (which you can't).

For better mileage I understand I need to lower my cruise kpa (from 60-80).

Should I use a bigger turbo or should I lower my final drive ratio ? or both ?

Current turbo TD04H-13C - Compressor 40/53mm turbine 52mm
for compression GT2560R is Compressor 46.5/60.1mm turbine 53mm
Current dif NB LSD 4.11


Thanks !