I have noticed that when I go thru a long rythm section , thottle on , throttle off multiple times , the power starts to cut out to the car until I let it catch up and then it fine. What would cause this issue. I ran into the same issue with a different brand esc so I dont know if thats the issue. Radio maybe? Using the sanwa mxV.

What ESC's have you used?

It could be multiple things. First I would check the sensor wire by replacing it with a new one as that can cause intermittent power issues if it's going bad or gets jostled too much. It could just be coming loose ever so slightly going over the rhythm sections.

It could also be the electronics combo used. If the ESC can only do 6v or less and you are using a servo like the Savox line, that could be causing brownouts when the load is too high for the BEC to handle. That's usually resolved by adding a Glitch Buster.

There is a chance it is the radio but it's pretty unusual for a Sanwa radio to respond like that. It's generally one of the other electronic bits that cause issues. But if you have a different radio to try you can at least rule that out.

in the past it was a graupner budget brushless system , it does the same with a hobbywing v3.1 120 amp esc. running a 2s lipo. Both total different system have done the same. I am using a savox 1256

I'm guessing it may just be the savox servo. And unfortunately you can't bump up the BEC for it because the receivers for the Sanwa MX-v can only handle up to 6v. So next step after making sure the sensor wire is not the issue, would be to purchase a Glitch Buster and give that a shot. Or try a different servo (not a savox or any high voltage servo). Something that can run between 4.8v-6v.

Here is an example of a glitch buster, at least one of them.

https://www.amainhobbies.com/protek-...k-2950/p450146

Well, it could be some problem with the receiver, too. A HW V3.1 shouldn't have too many problems with that servo. I ran a 1257TG and 1258TG with the puny Reedy XP SC700-BL RTR ESC - a few possible brown outs at a grippier indoor track as I recall when used in an SC10, but at a lower-traction outdoor track none - and with the B5M buggy no problems even at the indoor track. The 3A BEC in the V3.1 should handle the 1256TG with relative ease by comparison.

By the way, the RX-37 receiver that comes with the MX-V can actually handle 7.4V, but of course there's no actual need to test at 7.4V. And the V3.1 doesn't do 7.4V BEC output anyway.

At any rate, different servo, different receiver, glitch buster - all good things to test out if possible, as well as the sensor wire EbbTide also mentioned.

This is from its listed specs so using anything higher wouldn't be recommended.

Specifications:
Channels: 3
Nominal Input Voltage: 4.8v ~ 6.0v
Weight: 0.34oz (9.5gr)
Dimensions: 1.18x1.04x0.57" (30.0x26.5x14.5mm)
Frequency: 2.4GHz FHSS-2
Fail Safe Support: Yes (Throttle)

My user manual lists 7.4V, though. Hmm... I had it at 7.4V briefly when I installed the Hobbywing combo on my 4WD SCT, but settled for 6V in the end. Didn't actually drive with the 7.4V setting though, only tested turning the wheels.

Here's the specs from my manual:

Receiver:
• Model: 92625 (RX-37E)
• Nominal Input Voltage: 4.8v ~ 7.4v
• Weight: 0.25oz (7.1gr)
• Dimensions: 1.18 x 1.04 x 0.57in (30.0 x 26.5 x 14.5mm)
• Frequency: 2.4GHz FHSS-2
• Fail Safe Support: Yes (Throttle )

I suppose they could've changed the specs at some point

I'm assuming Sanwa is just lazy with updating their site specs. The receiver itself doesn't say it's rated for more than 6v but the Mx-v combo on Amain with the same receiver does. Apparently they updated the mt4s in a similar way.

I ordered the glitch buster and a new radio sanwa mts. Ill report after i receive them and try out.
I also have my antenna wire circling the receiver. I wonder if it could be missing some of the fast repetitive signals from the radio. This only seems to happen at the furthest point from the drivers stand.

Well I know it's not terrible to coil the antenna up to keep it as short as possible but wrapping it around the receiver itself could have caused issues. The Mt-s is a great upgrade but you may have just needed to uncoil the antenna and add the glitch buster lol. At least this way you'll know 100% what the culprit is .

I think I found the issue. Last night I was trying to figure out why it will some times not reverse . Seems the throttle switch is not working correctly. Ill look and see if there is a replacement switch since I want to give this radio to kid. Thanks for the help Ill, come back and update.