Installed 4:30's, how do I calibrate my speedo with several influential mods?

tmoneyballin

tmoneyballin

New Member
Aug 16, 2006
113
0
0
Suwanee, GA
#1
Finally got the car back to 100%! The P1506 error code was none of the above as far as solutions. I replaced the PCV valve(didn't help) and was going to replace the IAC when my buddy came up with the genious idea of switching his IAC from his 96 Cobra(which has no problems) to my car and both cars ran the same - we even installed my IAC on his car and it ran fine - we decided not to switch them back b/c it wasn't a problem! I still had the check engine code and the car still had a rough idle when put into neutral. So we lowered the idle about 150 rpm's to 900 rpms exactly and the problem went away! Now instead of it jumping from 1,000 to 2,000 when put in neutral it jumps from 900 to 1050 on occasion. More importantly it does not throw any more codes. Just wanted to share that progress for those who had helped. Thanks again.

Now I need to adjust my speedo because it is clearly off with my new setup.

Things I am concerned about are the new 4:30 gears and my 18 inch Saleen rims. How will I adjust the speedo to compensate for these two factors? Also, my compression is lower than stock(ready for a supercharger), so will this affect calibrating my speedometer? I add this point about compression because it makes my 4:30 gear behave more like a 4:10 would as far as rpm/mph ratio.

Any thoughts on calibrating this setup....Thanks in advance!
 
#2
I'd have to say it's more your 18s making your 4.30s act like 4.10s, rather than the lower compression. The compression shouldn't have anything to do with the speedo calibration at all. If you get a Dallas Mustang Speedcal, it can adjust for gear changes, tire size changes, and even transmission swaps. That should cover everything for you. I know most handheld tuners can also correct the speedo for gears, but I don't know if they offer such versatility as the speedcal does.

EDIT:

This was me assuming your car is a 5 speed. Here's a link to the Speedcal. If you send them an email before you order telling them what you already have done, they will set it up for you, so all you have to do is hook it up, and run!
 
#3
No I would definately say compression is a factor because I had the stock rims on when I was making the comparison of my setup to my friends. I mean the key ingredient is I could drop the car into 2nd going 60mph on stock rims with a 4:10. The Saleen rims were put back on upon completing the rear end swap, so I didn't drive the new setup with the stock rims to compare. I mean if someone else can prove me wrong - you can't drop a stock motor into 2nd gear going 60mph without blowing your engine on a 4:10 gear!

So is this my only option, buying the SpeedCal, or can I get a chip or something that would accomplish a similar goal? I really have never messed with calibrating the speedo so call me very ingorant on the subject...I ask because I am going to take my car in to a mustang shop in the next month or two and get a custom tune or chip burned so if I could "kill two birds..." I am all about waiting for the chip...

Thanks
 
#4
The PCM/EEC has no idea what kind of compression you have, and your compression ratio has absolutely no bearing on making changes to the gear ratio or tire diameter within the EEC.

You will need to manually change the tire diameter and rear axle ratio in your tune.
 
#6
The compression does not change how fast the tires, rear end gears, tranny and engine are spinning. These are the factors that the Computer uses to show speed. So the only things that you have done to your car to throw off the spedo are the tire size and the rear gears.

The low compression surely costs you some HP and can cause your car to "feel" slower, but I suspect you have other problems that will be taken care of during a dyno tune.

You can get the tuner to calibrate the spedo for you.
 
#7
I suspect that it's possible that the speedo was already off from the previous 4:10 swap - which was done by the previous owner without my knowledge...
Is this tune accomplished through a chip that can be reflashed or is it more complex? I ask because I don't want to get a custom setup prior to supercharging my car and spend several hundred dollars on both ends to get increased performance within a year. I mean I know getting a "perfect" tune for a supercharged setup takes time - I on the otherhand would just be going the daily driver/supercharged application route when I got to that point...

Thanks
 
#10
With it being a 98 cobra, no tuner will fix that as the speedometer is not electrical like the 99+. However, a DMP speedcal will. In fact here is a link and the right hand side is the calculator. Click that and put in the rear gear ratio of 4.30 and the tire info and it will tell you what switch settings to set the speedcal at.
http://www.dallasmustang.com/page/speedcal.php


The engine itself has ZERO to do with the speedometer regardless of compression, exhaust, supercharger or nitrous. The gears in the rear differential, the transmission and VSS will throw off the speedometer
 
#11
blackfang said:
With it being a 98 cobra, no tuner will fix that as the speedometer is not electrical like the 99+. However, a DMP speedcal will. In fact here is a link and the right hand side is the calculator. Click that and put in the rear gear ratio of 4.30 and the tire info and it will tell you what switch settings to set the speedcal at.
http://www.dallasmustang.com/page/speedcal.php


The engine itself has ZERO to do with the speedometer regardless of compression, exhaust, supercharger or nitrous. The gears in the rear differential, the transmission and VSS will throw off the speedometer
Click to expand...

Good catch blackfang. This is a good example of why a signature is such a good idea. :)
 
#13
So once I order this I can recalibrate it myself if I switch rims, transmissions, or rear end gear setup, or do I need to order a new custom replacement.

Also I have friends that are very schooled on mustangs, more so than myself, is this an easy install once it gets shipped?

I appreciate the advice guys, I post on here to be corrected when wrong and more importantly LEARN so I can help other newbies out in the future, whether on this forum or at the gas station when they want to talk stangs:nice:
 
#14
Yeap, it can be recalibrated for all those you just asked about. It's pretty easy. If you have a VSS sensor that was the only thing I had trouble finding. Scour the net though and you can find pictures of it, plus Dallas Mustang gives you some good instructions.
 
#15
blackfang said:
With it being a 98 cobra, no tuner will fix that as the speedometer is not electrical like the 99+. However, a DMP speedcal will. In fact here is a link and the right hand side is the calculator. Click that and put in the rear gear ratio of 4.30 and the tire info and it will tell you what switch settings to set the speedcal at.
http://www.dallasmustang.com/page/speedcal.php


The engine itself has ZERO to do with the speedometer regardless of compression, exhaust, supercharger or nitrous. The gears in the rear differential, the transmission and VSS will throw off the speedometer
Click to expand...

LaserRed01GT said:
Good catch blackfang. This is a good example of why a signature is such a good idea. :)
Click to expand...

tmoneyballin said:
So once I order this I can recalibrate it myself if I switch rims, transmissions, or rear end gear setup, or do I need to order a new custom replacement.

Also I have friends that are very schooled on mustangs, more so than myself, is this an easy install once it gets shipped?

I appreciate the advice guys, I post on here to be corrected when wrong and more importantly LEARN so I can help other newbies out in the future, whether on this forum or at the gas station when they want to talk stangs:nice:
Click to expand...

TMoney... Did you even read this? Your car apparently does not have an electronic spedo so the Xcal won't do anything. You must get a speedcal.

The more details you give about your car, the better advice you will get. And this will help us all learn.
 
#16
Wow, damn I read the install, a little more complicated than I thought...

So from what I gather once you buy the speedcal kit you can adjust it for any future changes that would impact the speedometer by adjusting the 0's and 1's in the unit itself?

One other dumb question, for some "unexplained" reason I had put a metal paper clip into my cigarette lighter (the one next to the shifter) and it appeared to short both cigarette lighters out - the other one being on the center console. I went to autozone or wherever and they said the fuses were fine...and couldn't recommend a fix....Will this potentially impact installing this since it refrences using that wire for the install? Also do you guys have any idea how to fix those cigarette lighters, I mean I mainly would need them for cell phone, but in this case it may impact getting my speedo fixed.
 
#18
tmoneyballin said:
Wow, damn I read the install, a little more complicated than I thought...

So from what I gather once you buy the speedcal kit you can adjust it for any future changes that would impact the speedometer by adjusting the 0's and 1's in the unit itself?

One other dumb question, for some "unexplained" reason I had put a metal paper clip into my cigarette lighter (the one next to the shifter) and it appeared to short both cigarette lighters out - the other one being on the center console. I went to autozone or wherever and they said the fuses were fine...and couldn't recommend a fix....Will this potentially impact installing this since it refrences using that wire for the install? Also do you guys have any idea how to fix those cigarette lighters, I mean I mainly would need them for cell phone, but in this case it may impact getting my speedo fixed.
Click to expand...

Don't trust anyone at AutoZone, they are idiots. They probably didn't even know where the fuse is for those accessory ports. The fuse is under the hood in the Power Distribution Box (assuming it's the same as my 95 GT), they probably looked under the dash. Mine were blown and I just replaced the fuse in there.

Second, the SpeedCal is not a difficult install. It's easier to install with a lift, but not too bad if you just jack the car up. The most annoying part is getting the clips out of the VSS. Other than that, running the cable and attaching scotch locks is a cinch. I would recommend running a more secure connection though, as mine lost contact from time to time (you will know when this happens, because your car will stop running). Also, you will never need to buy a new one. You set it by flipping dip switches, so if by chance, you change gears, tranny or tire height in the future, all you have to do is use the calculator to get the new settings and then flip the switches in the box.
 
#19
Awesome guys! I really appreciate it - there is nothing worse than seeing your high mileaged car put on inflated miles b/c your speedo is off! I will definately order this part and get one of my buddies to help install it - I figure if we can tear apart a DOHC engine, then we can probably figure this one out.

If there are any more suggestions keep them coming - especially the one about fixing my cigarette lighters!


THANKS!!!:nice:
 
#20
tmoneyballin said:
Awesome guys! I really appreciate it - there is nothing worse than seeing your high mileaged car put on inflated miles b/c your speedo is off! I will definately order this part and get one of my buddies to help install it - I figure if we can tear apart a DOHC engine, then we can probably figure this one out.

If there are any more suggestions keep them coming - especially the one about fixing my cigarette lighters!


THANKS!!!:nice:
Click to expand...
I just told you how to do it. Change the blown fuse under the hood in the PDB. It won't 'be hard to find.
 
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