[dberns]

I suspect it's some heavy duty drugs that even have me thinking this might be possible, but stranger things have happened, so I figured I'd throw the question to the group here.

When I'm driving my CVT at steady speeds ranging from pretty slow to 60 or so, I "feel" that the engine is just working harder than it should. I can't quite describe the reason, but it's the same sort of feeling you get when you're getting ready to shift a manual to a higher gear.

But... the CVT chooses the RPM/gear ratio using its own magical logic and design, with the only option to actually raise the RPM/torque by going into the "S" mode.

So my question, and please don't laugh... is there any plausable way of shifting the CVT gearing?

Thanks

 

[Insightful Trekker]

No.

Be happier in that the IMA batteries and their SoC can be managed better. In theory and on average a CVT's IMA batteries should last longer. But the hypermiler 5 speed drivers that minimize IMA assist should be able to equal a CVT in this regard. And a CVT's emissions are lower.

 

[Dougie]

"No" seems a bit strong. Obviously you could hack the control system to change the ratio in use, as long as it's not already at one extreme or the other of the CVT range. Of course, it would be quite a development project (comparable to MIMA) and would void all warranties, etc.

 

[Rick]

Sounds like a huge undertaking. I'd personally be more tempted to try and get a Japanese ECU and see if it works because from what I can tell their CVT's are lean burning.

 

[Insightful Trekker]

Dougie,

His key word was "plausable". If money is no object PM me and we'll get to work :!:

 

[joecvt]

The way that I think the CVT works is that it has its own control unit and
takes input from various sensors including the VSS (vehicle speed sensor)
and compares the readings from mapped values and adjust the ratio as
needed until the mapped values match again. If the CVT "thinks" that it
is going faster than normal without too much engine load, it will change
the ratio and lower the engine RPM....If you fake the VSS signal to read
slightly faster than reality then the engine rpm will become slightly lower.
The downfall to this is the acceleration will be more delayed before the
ratio changes enough to do any good. This may work for the intial topic but may have more negative side effects than positive ones.

JoeCVT - Just your average CVT owner

 

[IamIan]

the "easest" way if you can call it that .... would be to find some vehicle competition where the Honda CVT is being used....

I know in Future Truck GM gives allot of thier internal not normally shared information with the schools like Penn State that compeat in thier competition... .... Of course you have to sign legal waivers prommising not to tell anyone else when you apply to be part of the project.... But without telling other people the Industrial secrets you might be able to find someone in such a possition who just so happens to also be interested in modifying thier own Honda CVT control system.... And then thier "experience" with Honda CVT control system is just experience.... and thier results are thier own work.... without distributing or shareing the industrial secrets...

Other wise it is a ton of work to get a practice CVT and test and test until you figure out how to control it.

............. Or pay a engineering company to make you a CVT that fits the Honda Specs... and your control design.

 

[Insightful Trekker]

<snip>
I know in Future Truck GM gives allot of thier internal not normally shared information with the schools like Penn State that compeat in thier competition... .... Of course you have to sign legal waivers prommising not to tell anyone else when you apply to be part of the project....
<snip>

I thought that the waiver you signed also included this type of disclosure too :!:

 

[b1shmu63]

The real question to ask before anything else is: " Would Honda intentionally set the CVT to use more gas than it otherwise could?" I suspect that the CVT was setup to maximise fuel efficiency. The S button reduces efficiency to gain performance or power.

If the answer to the first question is yes, then the second question would be: "Can I improve gas mileage and decrease wear on the engine by setting the ratio to run the engine at a lower RPM.

If the answer is yes again then you have to afigure out how to accomplish this. The computer has many inputs. If you don't have a shop manual, you're nuked. Likewise if you can't read and understand schematics. I would gues that there are 5 to 10 inputs that deternine the operation of the transmission. I would not want to mess with the VSS input as that would likey throw off your vehicle speed display and mileage indicators. Besides, changing the rep rate of a pulse train is not trivial. I would start looking at the throttle position sensor and see if there is a torque sensor involved as well.

Personally I think that the main difference in mileage is due to lean burn, not transmission ratio. Check the RPM of the engine at a given cruising speed for the CVT versus the 5 speed in 5th gear. If it is noticeably higher in the CVT then there is hope that you can mod things. Again, if you have the real shop manual there may be a section on the CVT outlining what the correct RPM should be for a given speed. You may find that there is a way to adjust it to spec or in your case missadjust it to a different value.

Sorry I can't spend time researching this. I'm getting the twin latch circuit installed and tested. Interesting technical question though.

 

[joecvt]

I guess that I should have been more clear that when I suggested to
modify the VSS signal. I was only suggesting the modify the VSS wire
that goes to the Transmission Control Unit and leave the others alone.
If the TCM "thinks" the car is going slightly faster than the parameters
preprogrammed then it has to assume that less rpm is needed from the
engine to mantain the "current" speed.

On the other hand I would not suggest to try this mod. For starters it
would put more strain on the engine until the CVT catches up with the
reality that it is not making it up the hill as it should. This could lead to
long term damage to the CVT or the engine. Another thing to consider
is the CVT engine has 2 less horsepower and 1 less ft/lb due to the
lower compression ratio. The CVT has to make up for this sometimes
by using a different "gear" ratio than the 5SP in a like situation.

I think a nice compromise without mods could be made by your own
foot. Sometimes you hear the CVT changing ratios alot when going up
a small hill. You can see that your near the top of the hill but the CVT
does not know that detail. If you ease back on the throttle until the ratio
goes back down then you know the next time to do it slightly ahead of
time so the ratio hardly changes. If you travel the same route every day,
you can predict when the CVT will change ratios and use this throttle back
method. On long hills up can just bear with it or use "S" mode.


JoeCVT - Just your average CVT owner

 

[IamIan]

<snip>
I know in Future Truck GM gives allot of thier internal not normally shared information with the schools like Penn State that compeat in thier competition... .... Of course you have to sign legal waivers prommising not to tell anyone else when you apply to be part of the project....
<snip>

I thought that the waiver you signed also included this type of disclosure too :!:

double read it actually just to be sure.... It says I can't reveal any of thier secrets.... but the future truck competition itself actually encurages people to do PR type of promotional stuff..... So I didn't actually give out any of thier industrial secrets.... I just said that they share allot of said secrets with the people in the competitions.... But I did promote the Future truck competition by letting some people know that .... even if they are just voluntiers .... they get to see and learn things that they won't find any were else.....

Then if Honda was involved in a silumar compeition somewhere .... that the people in said competition .... Would be a great place to look for people who have the "experience" and "education" to be able to do this kind of thing....

Hell.... If I found out that Honda was doing a Future Insight type of competition with different schools.... I might be tempted to transfer.... even if only for a few semesters.... I would love that.....

 

[Insightful Trekker]

OK, :badgrin:

Now you triple read it and this time don't miss the "razz"

Truthfully I was trolling to see if maybe you were involved in some GM "secrets". And only in good fun. But now that I know your on the "other" ( ) side I'll have to watch what I let "slip" about Honda's.

So can you sneak into the archives and get the blueprints for all of those super MPG patents the GM has bought over the years and swept under the rug :?:

OK I'll stop now. Reads like a _GREAT_ learning experience. Stick with it :!:

Sincerely, <bad grin wiped off face now>

 

[IamIan]

It has been a GREAT experience.... I am just a first year... so most of the technical stuff is being done by graduate students for Master's and PHD work.... or by Engineering Faculty Voluntiers.... I would prefer it wasn't a SUV Hybrid.... but that is this 3 year comeptition they are finishing year 2 now.... GM aparently likes these kind of competitions not so much for finding new tech... but for finding new Engineers.... Undergrades just get Internships.... but the Graduate Student get to make some nice contacts with the right people if they want to go into hybrid vehicle production design.

Has been a Very Nice learning experience.... Some great people working on it too....

 

[Dougie]

One easy way to change the overall ratio is to buy bigger tires...

 

[Allnighte]

i think someone mentioned here that the CVT has a "tilt" sensor which helps the car decide whether you're on an incline or not, and puts the CVT into a lower gear if you're climbing. i don't know if you can "tilt" the tilt sensor to make you think you're always going down a slight grade, but i haven't been able to find the thread again.

 

[goat961]

i think someone mentioned here that the CVT has a "tilt" sensor which helps the car decide whether you're on an incline or not, and puts the CVT into a lower gear if you're climbing. i don't know if you can "tilt" the tilt sensor to make you think you're always going down a slight grade, but i haven't been able to find the thread again.

this may be as simple as useing the airsprings that mike has used to beef up his suspention in the battery pack he's been working on... but then again- i know nothing

 

[joecvt]

I was suggesting that awhile back...Here is the link of a the thread with
my original posting within:

http://www.insightcentral.net/forum/viewtopic.php?t=3079&highlight=

That was just a guess back then but I'm pretty sure by now I was
waaaaay wrong on that one. It just looked like the way is was mounted
that there was a possibility that there was an incline sensor. My test
drive afterwards was probably smoother due to better foot control.

Great memory Allnighte for remembering the post

JoeCVT - Just your average CVT owner