lv6l

i have a 94 civic hatch cx. jdm d16a sohc vtec with 92-95 ex/si tranny & cluster.

running on stock cx 13" donuts with 175/70/13 tires.

i'm pretty sure my speed is off because on freeway i have to cruise at 85 to 90mph to keep up to traffic. i live in california where the traffic can be fast but during regular busy hours, 85-90mph is too fast. ne ways i want to know is there a way i can calibrate my speed or someplace i can take my car to so they can do this for me? thanks.

sicky

I couldn't find it, but some where on this site is a link that has a mph calculator that will determine your mph by your rpm's, it's pretty sweet.

sicky

One more thing, what the hell is a "d16a"?

lv6l

hehe, i got a feeling you would ask that. tel tell the truth i dont know the full spec of it myself beacuse in theory this is the rarest of all honda motors. i have tried searching for specs on this motor and have ask many people, nobody knows. a lot of people confuse it with a 88-91 obd0 d16a6 motor or a zc motor which is incorrect. my best guess is this motor is the jdm version of the usdm d16z6.

Cute EK

If he is using the wrong size tires for the speed sensor, rpms aren't going to help him either.

lv6l

my tires are correct i believe. before i swap the motor i did not have this problem.

BUMP

old man neri

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">

running on stock cx 13" donuts with 175/70/13 tires.

</TD></TR></TABLE>


I do believe stock tire for that car is 165/70/13. Check the sticker on your door jam. It should only cause it to under-read by 2.5% though.

lv6l

oh. even the width of the tire effect the speed? i thought it was only the diameter.

2.5%, man i hate percentage, can you estimate for me roughly how many miles it'll be off? like say i'm going at 60mph, will my speedo meter be higher or lower?

TurboEM1

iTrader: (1)

no the width does not affect the speedometer but the fact that the width went up with the same aspect ratio means the tire is a larger diameter.

With a larger tire the speedo reads slower and with a smaller tire the speedo read higher.

If you are off by 2.5% then at 60mph it will read 1.5 mph off depending if its a larger or smaller tire.

old man neri

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TurboEM1 &raquo;</TD></TR><TR><TD CLASS="quote">no the width does not affect the speedometer but the fact that the width went up with the same aspect ratio means the tire is a larger diameter.

With a larger tire the speedo reads slower and with a smaller tire the speedo read higher.

If you are off by 2.5% then at 60mph it will read 1.5 mph off depending if its a larger or smaller tire. </TD></TR></TABLE>

Bingo

So seeing as you have bigger tires. If you see 60 on your speedo you are actually doing 61.5. Like I said, not a big difference.

thisisntjared

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

So seeing as you have bigger tires. If you see 60 on your speedo you are actually doing 61.5. Like I said, not a big difference.</TD></TR></TABLE>other way man. what do the rpms read with a given speed? give me a few examples.

old man neri

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

care to explain? bigger tires mean you go faster.


As for RPMs for a given speed I would need to know all the gear sizes and what not.

thisisntjared

i know where the rpms should be for the speeds with the z6 tranny.

the cx wheel/tire combo is smaller than the normal civics. the tires that are on there now are bigger than the stock cx size, but not bigger that what it is calibrated for.

lv6l

but isn't my tires and wheels the same as the stock cx spec? its both ...70/13, just the width of the tire is wider a bit.

but rpm wise at 60mph my rpm is at 3.5k i think. not 100% sure but i'll double check today and get back to you guys.

Soccerking3000

the 70 in the tire size is a ratio not a distinct size such as 165 or 175. I believe its 70% the width of the tire so logically a 175 tire will be larger in diameter than a 165 tire.

old man neri

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">but isn't my tires and wheels the same as the stock cx spec? its both ...70/13, just the width of the tire is wider a bit.

</TD></TR></TABLE>

165/70/13 is stock, you have 175/70, it is wider and a bigger diameter (not by much) the 70 means 70% of the 165. 70% of 175 is bigger than 70% of 165. (I know you hate percentages, sorry but there is not much way around it this time)

this is the FAQ thread in the wheel/tire forum, it should give you a good idea of what all those numbers mean.

wheel and tire faq

Tire Rack tire size help

another one


Hope this clears things up a little.
CHeers.

lv6l

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thisisntjared &raquo;</TD></TR><TR><TD CLASS="quote">i know where the rpms should be for the speeds with the z6 tranny.

the cx wheel/tire combo is smaller than the normal civics. the tires that are on there now are bigger than the stock cx size, but not bigger that what it is calibrated for.</TD></TR></TABLE>

at 55mph my rpm is 2.5k

thisisntjared

at 55mph on the speedo in 5th your tach should be between 2200 and 2400rpm. this is somewhat trivial but it helps to give you an approximate speed to work off of. what car did the tranny come from? coupe, hatch, delsol, or sedan?

edit: this could be correct if you have a tranny from a civic/crx 88-91 dx or si

lv6l

i'm not sure. all i know is that it came off a 92-95 civic ex/si. ex/si have the same tranny dont they?

lv6l

i found a pretty cool site that might help a lot of us that is having this problem. punch in the before and after tire size and it'll tell you what your actual mph is. pretty good.

http://www.net-comber.com/tirecalc.html

grimpy

Even if it is the tires, it should only be off by a little bit...

For example, my 4Runner came with 265/70/16 stock tires and my new tires are 295/75/16 and my speedo is off by 7 mph at 80mph... So when my speedo shows 80mph, I am actually going 87mph.

So considering that your car came with even smaller tires than you have right now... Now if tires were the case, if your speedo is showing 85mph, you are probably actually going 87mph or so...

I don't think the tires is the problem here..... It might have something to do with the gearing.

thisisntjared

the si(hatch/delsol) had a .75 5th gear but the ex(coupe/sedan) had a .702 5th gear. at 55mph thats a difference of about 150rpm. everything about these are equal except the 5th gear.

but even at that case if your at 2.5k at 55mph thats still off cus the ex tranny should be around 2200 and the si should be around 2350.

that makes me think that your tach is accurate to the speed of the vehicle but the speedo isnt. if it were strictly tire size causing the problem then the speedo and tach would still match but match incorrectly to the actual speed. anyone follow me?

lv6l

yeah kind of. how do i know if my tranny is from ex or si. also how can i tell if my speedo is messed up, is there anyway??

old man neri

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">yeah also how can i tell if my speedo is messed up, is there anyway??</TD></TR></TABLE>

Bust out the cell phones and have a friend tale gate you, have him read out the speed you are going at. Simple yet effective.

thisisntjared

switch the vss with a known good one and if thats it buy a new vss. or do the same thing with another cluster.

otherwise get it calibrated(i dont know how to do that)