AWD with Resistor Mod for steering

cool_cars · #1 11-08-2004, 01:00 PM

Hi all,
I haven't been on the site in quite awhile, but I started poking around to see what was new and found the inline or surface mount resistor mod to fix the steering in the xmods. Well, I was really excited about this because the bad steering has really kept me from enjoying my xmod. Searching the various forums, I was finding all different types of values being used, anywhere from 2k to 3.7K for inline, so I used two 10k micro pots that I had laying around. After alot of experimentation, I found that 2.7K gave me the perfect throw in the servo. It goes right to the stops, but doesn't want to go past them. Anything abouve 2.7K, especially 3.3K which was a more common value being used, you could tell the servo wanted to go farther and I was worried about the servo stressing to much. Once I was satisfied with this, I removed the pots and put in 2.7Kohm resistors, and it was perfect.

Now on to the AWD. It seems there has been concern with binding, so people have been avoiding the resistor mod with the AWD, or dialing out the steering throw if they used the mod with AWD. I found that there was no binding at all. I did test the diff at fully left and right and it was completely smooth. The only problem I found was that the bevel gear on the drive shaft catches the tie rod when turning hard left. I had to mod the tierod to fix this. Basically, the groove on the top of the tierod is for the bevel gear to clear properly. I had to cut and shave out some of the tierod, basically extending the left side of the groove, so the gear could clear properly when turning hard left. After that I had smooth running fully left and right with no drop in speed. I ramped up the throttle slowly and really watched and listened for any sign of binding but didn't find any signs of it at all. It might be because of the resistance value I'm using is a little less than others, so it's keeping everything within proper operating range, except for the tierod.

The real test was driving it. Before this mod, I could turn about a 40" circle at full speed with a white stage 2, 4.5 degree toe in tierod, red suspension on the front and yellow on the back. I used 4 of 24"x24" floor mats to make a 48"x48" area to test on. After the mod, with everything still the same I can now turn about a 15" circle at full speed. I have a large technical track that I build out of the mats, total of 32 of them, for my 1/24th DRR's and mini z's. There are about three hair pin turns, that the xmod couldn't excute, but now it'll blast through as well if not better than the mini z due to the AWD. It sticks to the track like it's on rails. Really amazing mod. After a lot of running, I did check the front end over and didn't see any signs of wear, so now I'm truly excited about the xmod, where before, I almost thought it was a waste of money. Unfortuneately, I don't have a way to shoot video to demo the results but I hope this info helps.

Skurge420 · #2 11-08-2004, 04:25 PM

hmmm I'm gonna have to try this mod soon

thats my main complaint with the xmods

when you get sticky tires on them the AWD doesn't let it turn at all, but if this fixes it....i'm all for it

cool_cars · #3 11-08-2004, 04:53 PM

Hey Skurge,
It sounds like you're wanting the car to perform the way I wanted it too. I saw a thing on ebay, do a search for "xmods tight turns", they sell ready-made to install resistors, but I don't know the value of them, but that's kinda dumb when a person can buy them at RS. More importantly, they had a link to their on-line tutorial about doing the mod. This kinda helped and had good pictures. I must have spent numerous hours on the xmod trying to tune it to get it turn properly, but knew that the real issue was that the servo didn't have the throw in it. I kept looking at trying to mod the controller, but couldn't find any way to do it and didn't even think about a servo mod until I hit the forums again. Now I'm just totally pleased with the xmod and would probably consider getting another now that I know I fix the steering. Oh, just so you know, I am using both of the diff's included in the AWD. I do have the front running extremely smooth. Most of that was to get the front wheels adjusted to the right tension, so there was no play but no extra pressure on the shafts and diff. This allowed the diff to run really smooth. But this was done way before I did the steering mod. I checked the movement of the diff at center and then at both far end points by turning the wheels by hand, the other would rotate smoothly the oposite direction and felt no tension or difference in the way the diff worked, which told me there was no binding. The car really sticks and turns amazing. It'll corner fast and tight with no drifting, like it's glued to the track. Anyway, good luck, you'll really like it.

Skurge420 · #4 11-08-2004, 05:45 PM

Ya I have 5 xmods right now and a new mini-z awaiting my return at home tonight

I haven't run the mini-z yet and I know i'm not gonna want to touch the xmods after that......so i would love to have better handling mods

I think this will help me

ynad · #5 11-16-2004, 10:27 AM

yeah tis mod works.
my jaw droped.
i turned miniz fan to xmods, after he saw what it does.
i got the 10k resistor . wanna try 2.7k.
that tie rod thing and "limiting stops () " on the shasis.
here is the pic for clarity. btw there is thread about this mod.
thanks to someone for posting those up.

Skurge420 · #6 11-16-2004, 06:21 PM

well it seems the more i do to my cars the more I need the better turning.

with the CF driveshaft i installed my RSX gets up too fast to make the turns in the basement........I need to get my soldering iron and get on this

only 5 xmods to do it on

dIsEaSe · #7 11-16-2004, 11:35 PM

Which is surface and which is inline?

cool_cars · #8 11-17-2004, 10:29 AM

Hey dIsEaSe,
Surface resistors are used on the actual PCB. A few people are replacing two tiny surface mount resistors on the PCB that feed the control signal wires. I think they were using a 4.7Kohm for that.

The inline resistors are spliced between the sensor pot on the servo and the control wires, in particular the orange and brown wires. It results in the exact same result as the surface mount resistors and is the easiest of the two types of mods. Also because the existing resistors on the PCB are left in place, that is why the smaller value of resistor is used for the inline. Let's say the existing surface mount resistors are 2KOhm, (Just guessing here as I did not ohm them out with the meter) but to get full throw of the servo you need 4.7Kohm, so you have two choices, either replace the existing resistors with higher value ones, or just add to the existing.

In this case, on my car using AWD, I found that using 2.7Kohm resistors inline, allowed the exact throw of the servo that I needed. hope this helps!

dragon4450 · #9 11-17-2004, 02:26 PM

for anyone thats looking for the 2.7kohm resistors. take a look at the resistor it will have 4 color bands on it and the one you are looking for will have them in this order.

Red
Violet
Red
Gold

i dont know about you guys but there are a few electronics places near me that dont have the ohms or kohm level posted so all you have to do is look for resistors with those colors on it and you can safely know it is the right one you need. also you can click here

cool_cars · #10 11-17-2004, 03:52 PM

I thought I'd add to, that Radio Shack used to sell, and I think they still do, a little card thingy that has three disks that you rotate. It's used for resistor identification. You turn the wheels for the numbers, like to get 2.7K, and it'll give you the color code. for that value. I think the gold actually signifies it's accuracy, like within 5%, or something like that. Anyway, I've had this for years and it's very useful. I know that Radio Shack sells the 1/4watt resistors in a giant mega pack of various values for like $12 or $13. I bought one of these about a year and a half ago to stock up for various projects and I've never run out. Plus, I've always been able to find a value that I needed out of that pack, including the 2.7K ohm's for the xmods.

dragon4450 · #11 11-17-2004, 04:09 PM

you are corect about the metal colored band it does signify the % of the resistor. the gold is 5% and silver is 10% if it dosnt have a metalic colored band stay away cos it will produce a "dirty" signal at 20%. you seem to be an old school electronics guy like myself i have 4 big organizers with all sorts of resistors and other various electronic components. also here is a link to a resistor coder i found on the net. resistor coder

cool_cars · #12 11-17-2004, 04:19 PM

Yeah, I am. I've been a tinker-kinda person since was I was kid. If I could take it apart, I did. I've been to an electronics school, can read schematics and troubleshoot to the component level. I'm always keeping a stock of stuff, cause who knows what I'll be playing with next. Besides RS, we have a couple of great OEM type electronics surplus places here. I know I'm a geek when I can walk into those and just get excited to see what I can find.

dIsEaSe · #13 11-17-2004, 06:28 PM

Quote:

Originally posted by cool_cars
Hey dIsEaSe,
Surface resistors are used on the actual PCB. A few people are replacing two tiny surface mount resistors on the PCB that feed the control signal wires. I think they were using a 4.7Kohm for that.

The inline resistors are spliced between the sensor pot on the servo and the control wires, in particular the orange and brown wires. It results in the exact same result as the surface mount resistors and is the easiest of the two types of mods. Also because the existing resistors on the PCB are left in place, that is why the smaller value of resistor is used for the inline. Let's say the existing surface mount resistors are 2KOhm, (Just guessing here as I did not ohm them out with the meter) but to get full throw of the servo you need 4.7Kohm, so you have two choices, either replace the existing resistors with higher value ones, or just add to the existing.

In this case, on my car using AWD, I found that using 2.7Kohm resistors inline, allowed the exact throw of the servo that I needed. hope this helps!

Thank you!
I've decided I'll do the inline, because I dont have resistors as small as the ones on the surface.
But I don't have any 2.7k's... Will 3.3k be acceptable, or should I head over to RS?

dragon4450 · #14 11-17-2004, 09:50 PM

Quote:

Originally posted by dIsEaSe
Thank you!
I've decided I'll do the inline, because I dont have resistors as small as the ones on the surface.
But I don't have any 2.7k's... Will 3.3k be acceptable, or should I head over to RS?

i would really sugest trying to get the 2.7ks. i belive that the 3.3 will put too much strain on the servo and cause it to wear out quickly.

hotrod29728 · #15 11-28-2004, 10:50 PM

Can you get pictures on how to do this mod? I really need the help... I am 14 and I'm inspired by you older guys who know so much about electronics... I've been tinkering with things since I was born... But, I really love cars and wanna know as much as possible...I'm going to a tech school after high school so that may help out a good bit... But, anyways... Thanks for that bit of info it really helped....