Overrun hysterisis

Reverant · Post by **Reverant** » Thu Jan 24, 2008 5:00 am

For those of us who happen to drive our MS'ed car a LOT in traffic:

Arming RPM: 1500
RPM greater than: 1200

So the overrun stops when the engine speed drops lower than 1200 but does not activate again if I don't exceed 1500rpm.

Comments?

Jim

Post by **muythaibxr** » Thu Jan 24, 2008 8:50 am

Sounds right. It should've also been that way in ms1.

Ken

Reverant · Post by **Reverant** » Thu Jan 24, 2008 11:25 am

I would love to have it in my MS1 but I consider any further development on the MS1 "dead in the water". I'm in the process of upgrading to an MS2, so I thought I should suggest this here.

Jim

Post by **muythaibxr** » Thu Jan 24, 2008 11:44 am

Ahh, yeah, there isn't any hysteresis right now.

Ken

Ballistic · Post by **Ballistic** » Thu Jan 24, 2008 2:28 pm

I've wondered about the feasibility of having hysteresis in the throttle position as applied to resumption of fueling.

On coasting downhill, fuel cut can cause enough engine braking that more throttle is required to maintain speed, thus negating the fuel savings. If fuel cut could be maintained even though the throttle is being opened, fuel cut could continue and speed could be held constant.

This isn't a feature request, rather I'm asking if this would make sense.

Post by **muythaibxr** » Thu Jan 24, 2008 3:17 pm

It sounds plausable although I'm not sure how much engine braking would be negated by the open throttle alone... I guess it would depend largely on the engine and vehicle.

Ken

UnaClocker · Post by **UnaClocker** » Thu Jan 24, 2008 6:10 pm

Ballistic wrote:I've wondered about the feasibility of having hysteresis in the throttle position as applied to resumption of fueling.

On coasting downhill, fuel cut can cause enough engine braking that more throttle is required to maintain speed, thus negating the fuel savings. If fuel cut could be maintained even though the throttle is being opened, fuel cut could continue and speed could be held constant.

This isn't a feature request, rather I'm asking if this would make sense.

I makes sense to me, I think I'd simply install a toggle switch on the fuel pump relay feed or something if I wanted to do something like that. Cut power to the pump and injectors..

Keithg · Post by **Keithg** » Fri Jan 25, 2008 9:04 am

I guess I don't get the gist of this request.

What particular problem is apparent and what would this resolve? I have never had a problem in smoothness or drivability that I could attribute to this feature not being present. I am not saying it does not make sense, just that I have never run in to this thought before and why I may want it. IMO, some of the basic bits of MS2/E (lags, etc) which affect running characteristics are difficult to grasp at times.

Please explain why it would help.

Regards,

KeithG

Ballistic · Post by **Ballistic** » Fri Jan 25, 2008 10:49 am

As it exists, fuel cut is active above a certain RPM. If the engine is being operated at or about that point, fuel cut will cycle on and off resulting in an annoying jerking.

If fuel cut were enabled at 1700RPM and disabled at 1200RPM, then on deceleration, RPM would need to rise an additional 500 before fuel cut would turn on again.

My previous post is in regard to having a "window" AKA hysteresis apply to throttle position as well, which is another settable condition affecting the enabling of fuel cut.

neonturbo · Post by **neonturbo** » Sat Jan 26, 2008 3:45 pm

As it exists, fuel cut is active above a certain RPM. If the engine is being operated at or about that point, fuel cut will cycle on and off resulting in an annoying jerking.

My MS1 extra does this. The stock idle air valve interacts with fuel cut. If set to a value for RPM that actually cuts fuel, I get an annoying surge. If I raise the trigger RPM, it never cuts fuel. I have an automatic trans if this makes a difference.

My previous post is in regard to having a "window" AKA hysteresis apply to throttle position as well, which is another settable condition affecting the enabling of fuel cut.

Due to system voltages or noise the TPS varies slightly, and can sometimes kick me in and out of overrun. If I change TPS value I have a dead spot on throttle tip in, or never get fuel cut. I do not know if the TPS lag factor will help this because MS1e doesnt have lags.

My only other suggestion is instead of a full fuel cut, to have a soft cut. It would act like a reverse rev limiter. My original computer seems to act (and works well) this way.

Reverant · Post by **Reverant** » Mon Jan 28, 2008 10:47 am

So, any chance of seeing this feature in MS2E?

Jim

Post by **muythaibxr** » Mon Jan 28, 2008 12:51 pm

not for 2.0, but probably for a minor release after 2.0 is done... 2.0.1 perhaps.

Ken

eliotmansfield · Post by **eliotmansfield** » Tue Jan 29, 2008 10:26 am

neonturbo wrote:
As it exists, fuel cut is active above a certain RPM. If the engine is being operated at or about that point, fuel cut will cycle on and off resulting in an annoying jerking.
My MS1 extra does this. The stock idle air valve interacts with fuel cut. If set to a value for RPM that actually cuts fuel, I get an annoying surge. If I raise the trigger RPM, it never cuts fuel. I have an automatic trans if this makes a difference..

I also see this on MS1-extra, also with an auto-trans. I dont have an idle valve, but do get a cycling / surge. To be fair I've never tried to adjust the parameters - but i can see how having hysterisis on the rpm could potentially help.
Ive not driven my MS2-e yet, as i only upgraded this weekend, so i cant confirm if the cycling is present in ms2e.

Ballistic · Post by **Ballistic** » Tue Jan 29, 2008 12:06 pm

neonturbo wrote:My only other suggestion is instead of a full fuel cut, to have a soft cut. It would act like a reverse rev limiter. My original computer seems to act (and works well) this way.

I've wondered about this too.

I don't know that this would work, but have thought that if the injectors on bank 1 were cut, and then after a user settable number of engine cycles bank 2 were cut, this would provide a softer onset.

On resuming fuel the reverse would occur unless fueling was resuming due to significant TPS input and then soft resume would be bypassed.

What I don't know is if single bank mixture distribution would be OK. If only for a few cycles it doesn't seem like it would matter terribly.

richyvrlimited · Post by **richyvrlimited** » Thu Jan 31, 2008 2:43 am

CrystalBlue wrote:I would love to have it in my MS1 but I consider any further development on the MS1 "dead in the water". I'm in the process of upgrading to an MS2, so I thought I should suggest this here.

Jim

Good suggestion Jim

I feel the same way, during overrun espically on a slight decline, once it deactivates the addition of fuel is enough to push the car past the threshold so overrun kicks in again, which decellerates the car, overrun kicks in etc etc. it's really annoying in traffic, but just as much an annoyance when coasting up to a set of lights in gear.

wuffwaff · Post by **wuffwaff** » Thu Jan 31, 2008 5:19 am

Hi,

since you can also set a MAP threshold, throttle position and a responce time it should be possible to get the fuel cut on overrun jerk free.
I don´t quite remember the settings I used (the car´s on wintersleep since November) but it seemed to work fine.
What would be nice though is a "soft return" function to avoid the jerk when the fuel comes on again.

William