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Old 05-09-2009, 08:37 PM   #1
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Default The 4:30 Fade

So I've been experiencing a problem the last couple of months that I've had trouble solving. Basically, at around the 4-4:30 during a race, my car starts to fade extremely hard. This problem has followed me around through different batteries, motors, speed controls, and a whole variety of attempted fixes that have all failed.

My leading theory is that I'm somehow cooking these motors (even though the temps are around 160, and the rotors still read high on the Zubak) by using increased timing. The problem seemed to start around the time I began experimenting with "boost" on the Tekin RS, and has now followed me to the SPX, even with the lower "mod" profiles. I haven't tried the TC Spec with a new motor yet, but that might be next.

All the other things seem to be right, though. The drivetrain is free, the batteries (SMC 4000) seem strong, the gearing is very reasonable, the equipment in general is in good working order. I've got couple of new motors coming which I'll try without timing, but the older motors (2 DUO's and a Novak) are all doing the same thing, even with new rotors. I guess I should mention these are 13.5's, and temps after races are in check, usually 150-160F. I'm running sedan with rubber tires on a medium-sized very high-grip carpet track.

One thing that complicates tracking this down, is that around the same time I started messing with these new ESC's, I also started running a spool (things run hotter) and we switched to 6 minute races. I noticed the problem before during 5 minute races, but it wasn't as much an issue since the races ended sooner. Now, though, there's 1.5-2 minutes where people start reeling me in, 'cause I've faded and they're all still running strong.

So, anybody else seen this? Are there any theories? I feel like I've checked all the obvious things, but perhaps there's something I've overlooked.
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Old 05-09-2009, 08:56 PM   #2
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My guess is that you're overheating your front tires...more of a setup issue than motor and gearing. And if that is the case, you'll need to alter your setup to create more steering from the rear of the car.


(just a thought)
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Old 05-09-2009, 08:59 PM   #3
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How much are you using in the battery in 6 minutes? I know I noticed a huge difference even in 17.5 going from a 3800 pack to a 5000. Even though I may only use 15-1800mah??? Now the car seems much stronger all the way til the end....and Tamiya rules run 8 minutes!!!
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Old 05-09-2009, 10:00 PM   #4
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Unfortunately, I've experienced the same thing.
Nor have I figured out a solution yet.
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Old 05-09-2009, 10:03 PM   #5
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Quote:
Originally Posted by J.Filipow View Post
My guess is that you're overheating your front tires...more of a setup issue than motor and gearing. And if that is the case, you'll need to alter your setup to create more steering from the rear of the car.
Wow, that's an interesting theory! Would the car feel different on the track if the tires were overheated? It generally feels very good, aside from slowing down noticeably. I guess I don't know how to really tell if tires are overheated?

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How much are you using in the battery in 6 minutes? I know I noticed a huge difference even in 17.5 going from a 3800 pack to a 5000. Even though I may only use 15-1800mah??? Now the car seems much stronger all the way til the end....and Tamiya rules run 8 minutes!!!
Hey Charlie! In the end, it may be a 5000 pack I need to try. The 4000's just fit so nice in the 416! I usually take out around 1900-2000 after a 6 minute race. We've got a TON of grip here, which really seems to change things in terms of gearing, heat and such.
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Old 05-09-2009, 10:19 PM   #6
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Use your IR temp gun to check tire temps. You can even check inside, middle, and outside temp of all four tires to get really great info on your camber settings and the car's balance.
Not sure about the really fast guys, but I generally see the front tires around 90, rear tires low 80s, and if there's a big sweeper the outside tires will be a few degrees hotter than inside tires. 13.5t rubber TC carpet, with 17.5t being a few degrees cooler.
And yeah, try a big fat 5000 40C pack.
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Old 05-09-2009, 11:00 PM   #7
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is your SMC the 28c? If you decide to go with a 5000 40c, please post your results. I am very interested in knowing what happens.

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Old 05-09-2009, 11:32 PM   #8
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Yep, 4aH 28c. I have a TP 40c 5aH that seems to do the same thing.
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Old 05-10-2009, 09:36 AM   #9
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Originally Posted by syndr0me View Post
Wow, that's an interesting theory! Would the car feel different on the track if the tires were overheated? It generally feels very good, aside from slowing down noticeably. I guess I don't know how to really tell if tires are overheated?
If you're having to 'saw' on the steering wheel of your transmitter to get your car around the track (ie, full throw for every turn on the layout), your setup is probably understeering. You can monitor this by not only temping your front tires after a full run, but also temping your rear tires. The thing to look for is the comparison of front tire temperature to rear tire temperature. Ideally, the two should be relatively close (ie, 95 degrees front, 90 degrees rear). If there is a HUGE contrast in front and rear tire temps (ie, 115 degrees front, 90 degrees rear), your setup is definitely understeering, and overheating your front tires. This would account for your "4:30 Fade".

I would suggest making adjustments to your setup by trying to 'free up' the rear of the car; lengthen your rear camber link or add more rear camber, for example. Try one setup change at a time, and monitor the contrast of tire temps (front to rear) after a full run.


My guess is that you'll find improvements in lap times and consistency with setup adjustments as opposed to chasing electronic timing, mechanical timing, battery capacity, charge rates, etc.
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Old 05-10-2009, 10:22 AM   #10
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I think I read something like this on the SPX stock spec thread. Same problem after trying high timing from the speedo.

If you are feeling a lack of punch and top end it is a motor/speedo problem not tyres.
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Old 05-10-2009, 11:08 AM   #11
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Pablo, yeah, but the guy posting that 'data' was syndrome.
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Old 05-10-2009, 11:15 AM   #12
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I have the same exact problem. From what ive seen, it seems to increase with timming advance (either by software or motor). Im not sure if it is from motor fading or the increased consumption followed by voltage drop. In any case, it seems everybody where i race suffers from same problem.

I race with lipo and 9.5T, with 7 min finals BTW.
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Old 05-10-2009, 12:36 PM   #13
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Quote:
Originally Posted by J.Filipow View Post
If you're having to 'saw' on the steering wheel of your transmitter to get your car around the track (ie, full throw for every turn on the layout), your setup is probably understeering. You can monitor this by not only temping your front tires after a full run, but also temping your rear tires. The thing to look for is the comparison of front tire temperature to rear tire temperature. Ideally, the two should be relatively close (ie, 95 degrees front, 90 degrees rear). If there is a HUGE contrast in front and rear tire temps (ie, 115 degrees front, 90 degrees rear), your setup is definitely understeering, and overheating your front tires. This would account for your "4:30 Fade".

I would suggest making adjustments to your setup by trying to 'free up' the rear of the car; lengthen your rear camber link or add more rear camber, for example. Try one setup change at a time, and monitor the contrast of tire temps (front to rear) after a full run.


My guess is that you'll find improvements in lap times and consistency with setup adjustments as opposed to chasing electronic timing, mechanical timing, battery capacity, charge rates, etc.
Regardless of whether or not this is the issue for my existing problem, I'm definitely going to take a closer look at tire temps after a run. I actually have my dual-rate down quite a bit, and generally have pretty good steering. The spool wants to understeer mid-corner, but that seems to be the nature of the beast. I'm always trying to find ways to tune around that without affecting the rest of the setup too much. Thanks a lot for the info and suggestion, that seems to be something that's often overlooked.

I did mention this problem in the SPX thread, but only after I saw someone else bring it up. I'd been thinking it might be related to timing prior, but when I saw others talking about it, it really got the wheels turning.
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Old 05-10-2009, 04:46 PM   #14
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Hi guys,

Just to share what i have found with the SPX. Since having it i have been using the high profiles 7 and 8 and have backed right off on the gearing, ive gone from 7 to 8.5 and im yet to experience any sort of fade within a 5 min race? a couple of times i have really pushed the temps with gearing around 6.1 and the temps have gone over what people call the brushless "safe" zone.
So for me even though my equipment has got very hot, im not seeing any sort of fade and im using NIMH instead of my orion LIPO. Dont know if that helps?......
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Old 05-10-2009, 05:07 PM   #15
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does it have anything to do with the 4:20 high?
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