JDM33

Good day all, I have a 95 civic cx Canadian edition. It has the 1.5 non-vtec with an auto trans. I am using it for local enduro racing. it does well cause its so light (3rd and 5th) but could drop lap times if I were able to stop the trans from shifting from 2 to 3 all by itself. I am looking for a cheap solution (cut/disconnect a wire?) as I have other expenses and race cars. This one is just for very cheap fun. here is a link to my incar video.

you can clearly hear the car shifting before entry into the corners and then promptly shifting back into 2. there is potential for this little car to win but I got to fix this issue first. Thanks.


Jack

slowcivic2k

If you have a factory service manual, you will be able to see the shift logic for each gear position. It is not that difficult once you know this info to create a "manual" shifter based on the info provided.

The shaffer shifter is a unit used to diagnose a lot of transaxles based on gear position. It also has the added benefit of directly controlling each gear position.

viper_boy403

iTrader: (1)

Could you not just adjust the TV cable? The other cable on the throttle body besides the throttle cable. Tighten it up some more. Firmer shifts and higher shift points

JDM33

I don't have a service manual.


I will try tightening the TV cable, see if that does anything.

slowcivic2k

Tightening the shift valve cable (TV cable) will produce a linear increase in the shift points at any throttle position in all gear positions. This may damage the torque converter clutch. This increased shift pressure can also be desirable in some instances, but in a street car will usually cause excessive wear on the oil pump and transmission gears due to the sudden engagement with additional fluid apply pressure. This is definitely not the way to solve this problem. Solving the shift points on a gear by gear basis is much more desirable, but much more difficult to accomplish. There are a few tricks that can be implemented during a rebuild to increase shift stiffness. Because these units are electronically-shifted though, the shift point cannot be moved without electronic reprogramming or manual control of the solenoids. Vehicles without a throttle cable on the pressure regulator valve cannot use this work-around.

If the OP chooses to do this, be advised that severe gear wear can occur. Let us know about your results so that others can learn from this.

viper_boy403

iTrader: (1)

I know why and how it works... it's obviously not a street car. I would never recommend that for normal driving

slowcivic2k

Then I suggest, based on the previous information provided, that you provide a more detailed description as to why the TV cable (valve) should be adjusted. The reason I suggest this is simple: There is simply too much crap information on the internet regarding issues like this without an explanation as to why or how it would be effective. Think about this the next time someone actually searches for this information. It is one thing to say the emperor has no clothes, it is another to say what clothes are missing and why.

viper_boy403

iTrader: (1)

If everyone had to provide credentials or evidence of everything they said, the forums would be cluttered with endless showboating and unnecessary arguments.

That being said, tightening the throttle valve cable is, in my opinion, the only viable option here. A bump in line pressure, along with "tricking" the trans into thinking you're at a higher throttle and therefore extending shift points would be beneficial in his situation. Might it cause premature transmission failure? Possibly. However it's a circle track/enduro car. The lifespan of which is generally not long to begin with.

I (unintentionally) experimented with this in one of my own cars years back, also an EG; the TV cable sheathing started to work itself out and bound up on the cable, effectively shortening the cable over time until it reached the throttle body cable mount and stuck at full throttle. Under part throttle it did not shift until ~4500rpm and at anything over half would hold it in gear until it reached the appropriate shift RPM, after which it would again hold that gear. Now, I'm not saying that he should get that extreme, but a mild adjustment might keep the transmission from upshifting when he doesn't want it to. Again, just a suggestion!

slowcivic2k

You didn't read my post at all did you? Adjusting the TV will linearly increase the shift points on all gears, but this does not correct the shift that will inevitably occur once the throttle is released: It will shift is the throttle angle is reduced.

The only real solution in this case is to maximize the line pressure as required, AND add a manual gear shift system. A solenoid-shifted system is easy to adapt to in this case, but requires additional effort to wire the solenoid grounds to a panel (or a shift switch) to command the gearshifts up or down like a Hurst-style shifter would.

Never once did I mention my credentials, my posting history is indicative of my contributions. Think about this before you post so needlessly with your own "credentials".

viper_boy403

iTrader: (1)

In theory, yes, that's how it SHOULD react to adjustment. However, from personal experience it behaves slightly different than expected. It will hold the gear at high rpm for ~3-4 seconds after releasing the throttle before it shifts to the next gear, which I believe will allow him time to get off the throttle, decel, and get back in it before the transmission shifts. Of course this is not the ideal fix, but it's free. Adding a manual shifter may actually even be illegal in whatever class it is that he runs in.

The other statement was more directed at you asking for "proof," vs my word, paired with how you have your signature listing your master tech/advanced certifications. I guess that's supposed to increase your credibility, no? Irrelevant to the thread though, and I have edited the previous post to reflect that.

slowcivic2k

The fault in your logic is that TPS and other MAP-related inputs are the only input the TCM can "see" via the PCM. Because of this, a shift will occur nearly instantly because the TCM will receive updated engine load information, calculated, or raw, and inhibit a shift or shift early as a result. This phenomenon can be demonstrated on any newer vehicle circa 1995+. The pressure regulator (TV) does not inhibit shifts today, it only makes the gearshift harsher and capable of handling a larger load. As for your "manual shifter" comment: You are not the OP, and I will not assume it is legal or illegal. Most modifications are "illegal" with that in mind, down to the guy that guts his catalytic converter for extra power racing or not. Don't assume.

Please explain your personal experiences in this case, don't just state you have it. Most GM transaxles/transmissions support manual shifting because a boost valve is used and throttle angle is an input to drive the oil pump to provide higher outputs and pressure. Many Fords behave the same way as well. Unfortunately most import transmissions still use a hydraulically controlled pressure valve. These can be cable-controlled, but that is rare since 1995. Most use a solenoid or internal pump (like a governor), to determine shift pressure. This used to determine shift timing to a great degree, but this is not longer then case because the shift can be commanded electronically.

My personal experiences go back to the Shaffer Shifter, which is a manual control breakout assembly for electronically-shifted transaxles. It was provided to the automotive aftermarket to determine shift timing, shift completion, and shift comfort. I've used this data to complete diagnoses related to gear specific transmission problems. This box also has the benefit of providing direct gear shift controls, which can be utilized by other (aftermarket mostly) powertrain controls to command shifts outside of those the PCM or TCM would otherwise command with current firmware.

viper_boy403

iTrader: (1)

how is my "logic" flawed when I have personally done exactly what I suggested? I'm not theorizing here. Then please explain how adjusting the throttle valve increases shift points if the tcm controls it strictly based on load? not being sarcastic, I'm actually curious.

all that other stuff is cool and all, but this isn't "gm-tech," nor is it "ford-tech.". Honda automatics are an anomaly in the transaxle world. Not only in design but also function. You should know that *tsk tsk*

I never said it was illegal, merely suggested that it could be. Having been around that group a bit myself, the legal modifications in any class are quite limited. But I guess if you ain't cheatin' you ain't tryin'

slowcivic2k

In a hydraulically-controlled transaxle, increasing the throttle valve position will increase governor pressure. Governor pressure exists to retard to advance the gearshift. The more throttle pressure (and thus governor pressure) the longer the gear will ride out. The same goes for no throttle conditions. This type of shift is purely hydraulic, there is no solenoid control. This pressure may also act on a oil pump boost valve, to increase clutch apply pressure.

In an electronically-controlled transaxle, the shift points are directly timed by PCM/TCM control. This method uses sensor inputs (TPS, RPM, MAF/MAP, etc) to determine when to shift the transmission. In the mid-1990's, most transaxles using this type of control still relied on old hydraulic circuits to increase shift pressure to decrease slippage in high load situations. 92-95 Honda Civic automatic transaxles still use a hydraulic throttle valve. As you increase the stroke on this, the shift points will increase linearly as a function of how far you adjust it. It will also increase, by a similar function, the shift pressure. Since these cars do not use a linear pressure control solenoid, it is possible to re-time the shifts based on a simple cable adjustment. The consequence here might be excessive shift pressure, which in a racing situation is usually a benefit.

Most modern transaxles will use solenoids to shift, and well as pressure control solenoids to determine line pressure for shifting like the linear pressure control solenoids used on 96 and newer Civic's. In these units, you must adjust the duty cycle of the pressure solenoids to increase pressure. Since this requires a duty-cycle controller to accomplish, it is not feasible as an aftermarket "upgrade" without a power controller, or additional module.

If you need any more information about how transmissions work, see this link:

https://honda-tech.com/transmission-...ained-2086594/

PS: Honda transaxles are not an anomaly. They are very similar in design and function to almost any other small-engined import transaxle. If you want a real anomaly, look at the Ford 4F44E. To say that just because its a Honda, its way different, is simply untrue. If your only going to use Planetary vs Helical gear drive as an excuse for difficulty, 90% of the parts would be the same in either case, minus the bands, forks, and one-way clutches.