I have 2 cars, both d16y8 5spds

the older car shifts like a bike

the newer one shifts like an automatic. What I mean by this is when I shift quickly from 1st to 2nd (or 3rd to 4th- or any gear), the time it takes for the revs to fall and it seems like the clutch to grab is almost 1.5-2 seconds As if I have a 4lb flywheel, and really long gears. Almost like im slipping the clutch.

The older car, its like there is .5 seconds to switch gears, almost instant reaction time. It seems like im switching gears on a crotch rocket, super quick.

Is this the clutch slipping on the newer car? I can drop the clutch at 5k and light the tires up on both cars- which ive only done twice.

Both cars have the same mods, all stock internals/trannys. Same bolt ons exc the older has a 2.5" exhaust vs a 2.25 (newer), both short shifters with prothane bushings

Another thing is, it seems as if I have a dx tranny in the newer one since @ 80mph im at 2.7krpms,

and the older car @ 80mph im at 3.4k

could the clutch not be grabbing on the newer car as well? clutch doesnt slip in gear, it just feels like I have a VERY light flywheel, and VERY long gearing; even though they are both y8 ex trannies.

both changed with honda OEM MTF.

thanks!





Modified by bigsyke at 8:23 PM 3/17/2008

 

How are you identifying the transmissions?

They could have different final drives internally.

What are the ID codes on the transmissions??

Do they both have black plastic speedo drive gears on the differential??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bigsyke &raquo;</TD></TR><TR><TD CLASS="quote">IWhat I mean by this is when I shift quickly from 1st to 2nd (or 3rd to 4th- or any gear), the time it takes for the revs to fall and it seems like the clutch to grab is almost 1.5-2 seconds As if I have a 4lb flywheel, and really long gears. Almost like im slipping the clutch.
</TD></TR></TABLE>

Your description sounds contradictory. What do you mean by "the time it takes for the revs to fall"? Do you mean that the rpm drop almost instantaneously when you get off the throttle and depress the clutch (as would be expected with a very light flywheel), ot that they seem to 'hang' at higher rpm and then drop slowly?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnlear &raquo;</TD></TR><TR><TD CLASS="quote">

ot that they seem to 'hang' at higher rpm and then drop slowly? </TD></TR></TABLE>

My shitty stock clutch would do the same thing if I hurried it. Felt like a slip(and it took the clutch about a second to fully engage if I shifted at 8k), but I could dump the clutch from a stop and smoke the tires. Hondas use wimpy clutches to begin with(possibly to save the trannies from destruction), and yours is possibly worn down pretty well, I think.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by johnlear &raquo;</TD></TR><TR><TD CLASS="quote">

Your description sounds contradictory. What do you mean by "the time it takes for the revs to fall"? Do you mean that the rpm drop almost instantaneously when you get off the throttle and depress the clutch (as would be expected with a very light flywheel), ot that they seem to 'hang' at higher rpm and then drop slowly? </TD></TR></TABLE>

they seem to hang and drop slowly. Yes it seems contracdictory, but thats how it feels. I shift pretty quick, however on my newer civic, it seems like super long gearing. I could shift at 4.5k, and it would fall down to 2k in 1st-2nd or 2nd to 3rd.

3rd-4th and 4th to 5th arent nearly a problem.

On the sedan, i could almost say its like a crotch rocket seeming that I shift at 4k the revs dont even drop, they are instantly seeming at 3k with almost no time inbetween. The car is responsive to my faster shifting, unlike the newer coupe.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Special Projects MS &raquo;</TD></TR><TR><TD CLASS="quote">How are you identifying the transmissions?

They could have different final drives internally.

What are the ID codes on the transmissions??

Do they both have black plastic speedo drive gears on the differential??</TD></TR></TABLE>

I havent checked for black plastic speedo drive gears. Ill try and get the ID codes here in a bit.


Could this be from different clutch fluids? my old civic is using dot3, not sure what th new one is using

 

This is the opposite of what you would expect with a light flywheel, i.e. with a light flywheel the rpm should drop sharply and rapidly, as well as rise rapidly. I strongly suspect your problem is associated with the IACV (idle air compensation valve).

The IACV is designed to adjust idle speed with auxiliary loads on the engine, i.e. AC, lights, tranny drag in gear (auto boxes), etc, and is a slave of the ECU. However, it also seems to commonly (at least not un-commonly) cause the rpm to ‘hang’ momentarily at higher rpm when you shift gears (i.e. when you lift off the throttle and depress the clutch), and then cause the rpm to drop only relatively slowly. Sometimes this problem is so bad that the rpm may actually momentarily rise slightly as you lift off and depress the clutch.

I had this same wildly irritating problem with my CB7, which I assumed was because for some reason Honda had designed the IACV to do this since the IACV didn’t otherwise seem to be misbehaving (i.e. idle speed compensation worked perfectly and promptly). When shifting gear the engine rpm wouldn’t drop sharply (would actually jump slightly) , meaning that when you re-engaged the clutch the car would irritatingly ‘lurch’ forward slightly and the rpm then drop quickly but only as a result of the clutch being re-engaged and the car’s mass forcing the rpm to drop. The only way to make smooth up-shifts was by making slow up-shifts (grrr!).

The fact that you have two more or less identical cars that do not both do this suggests that it may actually be a fault with the IACV rather than a design characteristic (?). I do know there are other people who have the same issue with manual gearbox Hondas.

To check whether or not your problem is IACV related, disconnect the IACV electrical connector (ignore the CEL this will generate). Drive the car with the IACV disconnected, paying attention to rpm behaviour as you change gear. If the rpm now drop satisfactorily when shifting gear then the problem is IACV related. Be aware that disconnecting the IACV will cause on / off throttle behaviour to become harsh and the idle speed may well drop causing idle vibration (especially with auxiliary loads), so you won’t want to do this as a permanent thing, just as a diagnostic test.

If the IACV is the problem then you could try replacing it (I’d be tempted to swap the IACV from the other car to see if this fixes it, and I’d be interested to know if it does). My ‘solution’ to this problem has been to block the air passages into / out of the IACV by fitting a blanking plate (made from thin metal shim) between the IACV and plenum chamber, so no air can pass into the IACV and thus the IACV can have no affect on anything at all.

This does mean that the idle speed no longer compensates for auxiliary loads, so idle drops when the AC etc are used (only a significant issue with AC really). However, I’ve set the base idle on the high end of the recommended idle speed and the engine is still relatively smooth with AC on at idle, though it was quite rough until I fitted new spark plugs.

This fixed the ‘hanging’ rpm at shift and allowed the rpm to drop much more satisfactorily (faster / smoother up-shifts, bliss!). It also made rev matching for down shifts easier and more accurate because the engine’s response to ‘blipping’ the throttle became much more consistent and predictable (faster / smoother down-shifts, double bliss!).

Blanking the IACV also resulted in improved light throttle / low rpm torque, allowing easier take off from rest and inclines that used to require more throttle and / or a down shift could now be taken on a lighter throttle in a lower gear.

Blanking off the air flow to the IACV causes no CEL nor harsh on / off throttle behaviour, as disconnecting it does.

Before I blanked off the IACV completely, I had fitted a restrictor plate (like the blanking plate but with a small hole and a large hole, one at each IACV port orifice) that allowed the IACV to work well enough to compensate the idle speed, but restricted air flow into the IACV enough that the IACV didn’t have as much affect on ‘hanging’ rpm when shifting gear. This made a significant improvement, but didn’t completely cure the problem, which is why I ended up blanking it off completely.

Shift problems associated with the IACV and rpm drop (or not) seem more pronounced in the lower gears.

You say; “I shift at 4k the revs dont even drop”, then in the same sentence say; “they are instantly seeming at 3k with almost no time in between”. Conflicting statements, which is it?