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Running Mod... decisions decisions decisions!

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Running Mod... decisions decisions decisions!

Old 11-27-2019, 07:33 PM
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Default Running Mod... decisions decisions decisions!

What factors do racers consider when choosing what motor, gearing, timing, boost, etc. to run mod? I’ve been doing blindly so far, but the AWD class at Hot Rod Hobbies is open, so I’ve found setups that suggest a 6.5t with 81/20 gearing and 20 degrees of timing (plus boost) would work, but wondering how people come up with those specs in the first place.
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Old 11-27-2019, 07:57 PM
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Have you run modified before? 13.5 4wd?
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Old 11-27-2019, 08:33 PM
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Originally Posted by Davidka View Post
Have you run modified before? 13.5 4wd?
I have only run 13.5 blinky 4wd and 17.5 blinky 2wd. Never played with boost timing.
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Old 11-27-2019, 09:04 PM
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Boost/timing is a very minor adjustment for modified. A 6.5 will be overwhelmingly powerful without any. If it’s your 1st attempt at modified, you’d probably transition better starting with a 9.5 or 8.5 (will still be mind-blowingly fast compared to 13.5). You could increase power with timing as you get used to it + learn about those settings. Once you’re ready for a faster motor, you can drop this one into the 2wd. I think you’ll be faster initially with the softer motor & possibly enjoy it more.

just my opinion..
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Old 11-27-2019, 09:47 PM
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I think my 4wd 6.5 is somewhere around 20 degrees on motor. 30 boost. 30 turbo. Geared slightly low.

Fixed motor timing is what you want for slow sections. Less is torque-ier. Boost is what you set for jumps and the infield section. Turbo, if available, is for the straight. If your esc lacks turbo, set your boost end rpm higher and boost more.

It'll blow the tires off the rims. I literally have to conserve throttle to ''conserve glue''. 5 min runs, motor temp is only warm.

http://site.petitrc.com/reglages/hob...saw2018111618/
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Old 11-28-2019, 07:50 AM
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While I agree that a 8.5T might be a good starting point, I have struggled to find a good balance with timing/boost and temps... it was a lot easier for me to drop in a 5.5T with no boost and then gear for temps in my mini truggy. I started out with a 7.5T and played the timing/boost game until I cooked my motor, then I dropped in a 5.5T with no boost and haven't had a single issue since... kinda wish I started there to begin with, ha!
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Old 11-28-2019, 09:44 AM
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Originally Posted by billdelong View Post
While I agree that a 8.5T might be a good starting point, I have struggled to find a good balance with timing/boost and temps... it was a lot easier for me to drop in a 5.5T with no boost and then gear for temps in my mini truggy. I started out with a 7.5T and played the timing/boost game until I cooked my motor, then I dropped in a 5.5T with no boost and haven't had a single issue since... kinda wish I started there to begin with, ha!
Nice comment! I was considering dropping a 9.5 in as per the above suggestions, but I guess just starting out with no timing on a 6.5 could do just as well. Adding timing later would be simple if I ever decided to.

If I run no timing, do I run a fan on the motor and not the ESC (like we do in blinky stock)?
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Old 11-28-2019, 09:45 AM
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Worth note, if you go the softer motor route, try not to get caught up in the idea of making it faster. Run it where it is comfortable (gearing & temp) and accept its performance. If a guy with a bigger motor pulls you a couple car lengths on the straight, that’s ok, his faster motor is faster. It’s the rest of the lap that really matter.

This may have been why billdelong had trouble getting temps under control. I understand he’s a competitive modified driver and likely was working to make his motor pull like the most competitive cars in the class, which he later solved by going to a bigger motor, which he could already handle comfortably.

Fans are an “as needed” item. I find I don’t need one for 17.5 2wd but do for 13.5 4wd. I never had motor heat problems back when I ran modified. That was before fans were ever used on motors, so we just geared appropriately. Again, I think you’re going be surprised by just how powerful even a 8.5 would be, and that motor is a solid choice for a 2wd buggy should you want to move on to something faster in your 4wd.
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Old 11-28-2019, 10:15 AM
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I think it's one of those things that you just have to gain experience and play with to see what works best for you. Although I'm happy with the 5.5T motor in my Mini Truggy right now, the track is a large 1/8 track that has been shortened to run 1/10 classes (the large triple on the back section of the 1/8 track is closed off) so the wide lanes and hard pack surface make it suitable for the 5.5T motor, though I admit that the truck tends to wheelie in some sections to where I have to be a little more smoother on the throttle which can hurt my lap times when I have to back off the throttle to get all 4 wheels on the dirt... I might drop in a 6.5T motor soon which might give me faster lap times even though it might be slower down the straight and I think that's where boost comes into play which I haven't mastered yet. I just went down on my center diff to try this weekend to see if that helps prevent the wheelies, if that doesn't work then a 6.5T motor may be the ticket, at least I'm not thermaling, ha!
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Old 11-28-2019, 11:57 AM
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It also depends one the track you're running on and how you drive. At the same facility when we change layouts I will change boost, and turbo mainly depending on the straight sections and how hard the layout is if its tight and technical with a short straight I don;t use turbo. But we've had more open layouts where there is sweeping sections before you get ontop the straight where I put 30* of turbo timing to engage after .5s of full throttle to get that extra speed for the straight but not be over motor'd on the infield. But I messed with the amount of turbo and how long it takes to engage quite a bit until I get where i like it. My gearing and motor timing never really change.
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Old 11-28-2019, 11:58 AM
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I wouldn’t be surprised if I end up not being able to handle any of the mod motors and go back to 13.5 even though this track only runs 4wd mod (and 2wd is only stock). I just figured, it’s allowed so why not experiment?
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Old 11-28-2019, 12:16 PM
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Here's my little guide from another thread, should give you a little insight into how some drivers setup for mod. I setup all my mod cars like this.

Start with the recommended gearing and set your motor timing very low(hobbywing - 20°). This keeps the amp draw to the minimum throughout the rpm range and will drop max rpm to a stock motor speed. The esc timing is useful to adjust where in the rpm range you need more power/use more battery. Timing focuses efficiency and power in only one range of the rpm band, by adding boost and turbo you can produce better power and efficiency in places where power drops off in the rpm band, producing a broad linear power curve without having dips or spikes.

Initially you want to see maximum rpm being reached on the straight. Focus on the infield driveability as well, you want to be able to drive it 100% in control with low can timing. It may feel kind of slow depending on your motor turn but don't worry for now. My 7.5t with steel drivetrain and 20° can timing was actually significantly slower than my 13.5t+plastic gears+pucks setup. Moving up to a mod motor doesn't always mean more speed. But do not worry about all out speed right now, just driveability, you will get the speed later.

Use your gearing and punch settings as your 1st gear when accelerating and to control the overall feel of the buggy.

Boost timing is your 2nd gear. Use it to increase your low-mid rpm torque. It's very useful for clearing jumps and accelerating hard out of corners. Just be careful it can make your consistency suffer in the lower speed stuff because it will cover ground quicker, you need to use less throttle and be more precise on the trigger.

Turbo is your 3rd gear for top end acceleration for the straight and/or a big feature on the infield depending on the activation setting. Using the full throttle+rpm setting you can adjust where the turbo kicks in on the straight. The delay and increase rate can be useful depending on your grip level/motor strength to keep the tires from being overloaded as it kicks on, a higher setting will be more aggressive when it kicks on.

The difference between turns is slightly more power throughout the entire rpm range and more rpm. So for instance on a lot of setup sheets with a 5.5t you might only see 5° of turbo in conjunction with low can timing, because a 5.5t has so much power. With a 6.5t to get the same power throughout the same rpm you may need 5°boost and 10°turbo. I switched from a 7.5t with 20° can timing and 35° esc timing, to a 5.5t, and immediately took all esc timing off and even reduced the EPA to 95%. But the 5.5t still has too much mid rpm power, unless you have a large track or drive on carpet, the max I suggest for 4wd buggy is a 6.5t.

If it seems confusing well it is however if you start slow and work on each setting you'll get the hang of it pretty quick.

Last edited by trf211; 11-28-2019 at 12:41 PM.
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Old 11-29-2019, 09:50 AM
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I’ve been running mod wheeler for years and have yet to race on a track where a 5.5 with conservative timing and gearing won’t clear any jump. And have more than enough speed down the straight. JMO
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