mspdmx3

Hey guys, i was wanting some ideas on what you guys with atmospheric BOV are doing for correct afrs in between shifts. I need some ideas because in between shifts i'm going extremely rich and its killing my mpg, i'm down to 25 mpg. So far what i've tried that works, is the "overrun" settings, because it cuts fuel immediately after throttle release, but it makes the car jerky in some situations. Theres gotta be another correction, please post some options.

Bryce

iTrader: (24)

We need more info regarding your setup.

mspdmx3

Ms1v3 w/ 029y4, wasted spark, sc6062 billet turbo, 1.8bp, 1000cc injectors,etc. Its sort of a general question, i know alot of people with vented bov's go rich between shifts due to the lost unmetered air, but MAP cars on Megasquirt should not have this issue. So i was wondering what other tuners are doing to fix this without hurting drivability. Let me know if you need more info.

wittyworks

iTrader: (6)

why dont you just get an IAT put in instead of MAF? I think everyone basically uses that to fix this problem. It shouldnt be very expensive at any local welding place to weld in a bung of any material, and its simple to hook up. Where are you located

Bryce

iTrader: (24)

He already is running an IAT sensor. The MAP sensor along with IAT sensor are used to determine the amount of fuel needed.

In Tunerstudio, you can play with Decel Fuel Amount in the acceleration wizard. You don't seem to have mentioned that setting.

wittyworks

iTrader: (6)

Um how is he using the MAF if the IAT sensor plugs into the MAF sensor location?

mspdmx3

well that is why i posted, to get ideas. I looked in the acceleration wizard, and saw decel fuel, but it seems very picky as to what values it likes. I am using TPS dot and i believe i have it at 90%. What value are you using and what are your afrs like in between shifts when your bov opens? Thanks alot fellas

mspdmx3

map 2.5 bar and also gm iat sensor right before throttle body

wittyworks

iTrader: (6)

Okee doke i mixed up MAP and MAF. I had the same problem as you and like bryce said, I just lowered the decel settings. I would just play with that while on a drive or even just revving the motor while stopped to get it to fluctuate less.

Bryce

iTrader: (24)

Is this city driving or max mpg highway driving?
My decel fuel amount at 89%. I do believe that is the default value on an MSPNP map.

How rich are your AFRs going between shifts?

Screenshot a log.

mspdmx3

This is city driving, in between shifts i go as rich as 11.0-12.5afr, BOV is as tight as it gets. Like i stated, the overrun settings helped a ton, but they make the car jerky per say, driving in a parking lot because it cuts fuel ASAP after letting off throttle, which is why i turned them off. I will try the decel settings to see if it helps, always good to learn something new. Any other suggestions fellas?

Bryce

iTrader: (24)

Set a 1 to 2 second delay for overrun fuel cut to make it smoother. I have mine set at 3 because I like the extra pops and bangs.

Braineack

iTrader: (62)

All you guys are going to do is make driveability go to **** the more you try to solve the car going rich for a split second when you lift.

Faeflora

iTrader: (2)

Yah just maybe you are getting 25mpg because you have a sweet *** turbo and drive the car like it should be driven.

Best mpg for me so far is 20mpg.

Is your motor built?

Braineack

iTrader: (62)

Or maybe the rest of the fuel map isn't tuned well? You can't solve going rich between shifts. Think about what's involved: You're dumping in a lot of fuel, you snap the throttle closed and the MS can only react to that and cuts injections/sparks. So have have some unburned fuel that makes its way through and your o2 reads rich.

If this is causing your MPGs to be so low, then you have other issues.

Your overrun should kick in if your coasting in gear, and if your RPMs are too low to trigger overrun and you're still rich, then your fuel map has too much PW in that area.

Jacking down the decay enrichments just causes other issues when you are simply manipulating your pedal. Everytime the computer senses TPS decel, if set to 90%, it cuts simply 10% of fuel. You'll find EAE enrichments to handle this better, they designed to handle slow manipulation of the pedal and to keep the AFRS stable when doing so.

What AFRs are you cruising at? what RPM are you idling at and what AFR? What is your timing like? What are your driving habits? How rich are you at 100kPa? How often do you cruise at 100kPa, just skirting boost? EGO enabled?

These are the things that will improve MPG.

FWIW, Shuiend made 30mpg driving back down from here to SC after I tuned him up. I am seeing 26-27mpg city driving only.

mspdmx3

Haha, thanks Faeflora for the comment, i wish that was the reason. No it is a stock bp (cryo treated) with a real nice turbo kit, going for 400-450whp on e85 soon.

As far as drivability goes, the fuel map is very fine tuned, ego correction is on, timing map is smooth, etc This is a street car, i daily drive it and this is the only thing that irks me that i want a solution to. There are ways to tune it out, but i was looking for alternative ideas, i'm not just gonna "live with it" because it is a standalone ecu and should have options for this. Hell, even my safc piggy back had a decel air setting to compensate for loss of air between shifts, so the megasquirt must have better options. This is definitely affecting my gas mileage, because if you think about how many times you shift if you daily drive your car, especially with a short geared g series tranny, you can see how big a difference this will make. I should be getting honda gas mileage 30-40 mpg, im getting 25-28mpg, but i want more and i think this will do the trick. Thanks for your feedback, just trying to gather ideas!

Bryce

iTrader: (24)

Another tip. Lower the RPM threshold for overrun fuel cut. Too low and you'll have stalling issues. I have mine at 1400 with the stock ecu controlling the IAC. It could go lower. The lower it is, the longer you can coast without consuming fuel, especially coming to a stop.

Faeflora

iTrader: (2)

Pics of your car and engine bay?

One other thing to check:

Log your driving and note the load rows that you hit in between shifts. Probably some high vacuum rows. Your fueling may be jacked up in those rows at those RPMs.

mspdmx3

Alright definitely will look into this to see if these suggestions work.

Heres a link to pics of my newest setup, pics are on pages 1 and 2.
http://clubprotege.com/forum/showthread.php?t=48831