Motor choice for 2wd= fast, or slower + boost

[Timee80]

I run a 10.5t in my 2wd and i love it. I can use more of the throttle more of the time and its much easier to drive and make use of available traction. The motor i have in it is just a cheap speed passion sportsman at the minute and lacks a little bit of grunt
Should i buy a better 10.5t and simply up the turbo timing on larger tracks, or should i just get a 7.5 / 8.5?
Not long ago everyone was running 5.5 / 6.5 in 2wd and now the norm seems to be 7.5 / 8.5
Will people start to move to the even slower motors now that the new breed of esc's can deliver the dynamic timing that can make motors crazy fast?
Whats your thoughts?

[TARTMAN]

I prefer to run a fater motor in my cougar and have no turbo etc, means its more driveable for me, not a lover of the turbo etc(old school thumbs)
I have a speed passion 7.5T in it and a decent vortex R10 pro ESC from the box settings, its smooth and powerfull and easy to drive.....

I have tried the turbo etc in it but prefer it without. I Save the mad stuff for the sx3! It can handle the extra power and turbo.

Originally Posted by Timee80

I run a 10.5t in my 2wd and i love it. I can use more of the throttle more of the time and its much easier to drive and make use of available traction. The motor i have in it is just a cheap speed passion sportsman at the minute and lacks a little bit of grunt
Should i buy a better 10.5t and simply up the turbo timing on larger tracks, or should i just get a 7.5 / 8.5?
Not long ago everyone was running 5.5 / 6.5 in 2wd and now the norm seems to be 7.5 / 8.5
Will people start to move to the even slower motors now that the new breed of esc's can deliver the dynamic timing that can make motors crazy fast?
Whats your thoughts?

[samd]

You would be better with a proper puff motor like 17.5 no boost Tim

[john333]

this is interesting for me too, I've got a 6.5 in my Cougar and for indoors it's mad fast - never on full throttle, but last week I drove my mates car for the final which had (I think) a 10.5, and whilst it felt dog slow, I actually equalled my best time of the night with it. I would probably have beaten it with another run.

So it is a balancing act between being dead fast with the possibility of over cooking it, and being slower with no option of crashing or you wont catch up!

[ollyracing]

I think a nice brushed 27turn would be ideal for man of your talent...

[TARTMAN]

I think you lot are being mean.......... OK, I dont know the man in the firing line so may well be justified...... LOL.......

Happy racin!

Originally Posted by ollyracing

I think a nice brushed 27turn would be ideal for man of your talent...

[samd]

Silver can!

[TARTMAN]

thats low for anyone............. below the belt!

380 silver can(grasshoper style) hehe

Originally Posted by samd

Silver can!

[Timee80]

Thanks guys thats great. Any serious answers? By the way my driving is the shizzle

[TARTMAN]

My original comments were genuine and serious........ the rest were just joining the band wagon.............:lol :

Originally Posted by Timee80

Thanks guys thats great. Any serious answers? By the way my driving is the shizzle

[Timee80]

dont worry tartman, its the others being dweebs (what a cool word)
they'll not be laughing when i kick their arse with my new lrp x12 8.5t when it arrives- thats you olly and sambo!!
Oh yes, be very affraid

[samd]

Nice choice Tim

[TARTMAN]

Yes that they are!
Good choice, 8.5T is a nice one for 2wd. not to mental but mental enough!

I have an 8.5T as my backup motor for the 2wd.

Originally Posted by Timee80

dont worry tartman, its the others being dweebs (what a cool word)
they'll not be laughing when i kick their arse with my new lrp x12 8.5t when it arrives- thats you olly and sambo!!
Oh yes, be very affraid

[janus_77]

I prefer overkill, so my motors are mainly 5.5 on astro en 6.5 on clay/dirt. Maybe not the best solution for laptimes, but it's a lot more fun.
Normally full throttle is only used in care of emergency .
I tend to overheat/fry esc's when I use a 8.5 with boost.

[colmo]

This is a question I've been considering.

With dynamic timing advance, even a stock 10.5 motor can achieve mod level rpms. Their relative lack of torque is offset by the gearing, with quite high FDR to make them rev more.

They'll definitely run hotter, as increasing timing reduces efficiency and thus increases heat, but with the right boost settings (say, incremental timing advance per RPM bands, to give a smooth power boost), there's no reason they won't perform just the same.

I'd like to see some maths on it, especially the torque comparison of a mod motor with moderate FDR versus a stock motor with high FDR.

One touring car racer I know compared a 3.5T (no boost, that would pop any speedo!) to a 10.5T boosted to the rafters; his conclusion was at the top end, there was no real difference (both are crazy fast!), but the 3.5T felt like it was trying to pull up the carpet (massively more torque). In 2wd buggies, you'd be using at most a 6.5T, and you'll have a slipper clutch spinning away much of that torque anyway.

[reg]

i run an 8.5 octa in my vega,i run it on the slowest profiles on small tracks,then just turn up the boost on tracks with a long straight,

[Neil Skull]

Well if you are happy with a 10.5 and looking to improve go for an 8.5.
The boost is great on tracks with a long straight, but for most tracks you want a little more power than the grip and learn to use your throttle.
The top drivers can hang on to Hot motors but for most club guys an 8.5 is plenty in 2wd.

[Gayo]

Originally Posted by colmo

One touring car racer I know compared a 3.5T (no boost, that would pop any speedo!) to a 10.5T boosted to the rafters; his conclusion was at the top end, there was no real difference (both are crazy fast!), but the 3.5T felt like it was trying to pull up the carpet (massively more torque).

I agree with that. Last sunday I had a race indoors (slippy wooden floor and carpet) and instead of my usual 7.5, I used a 10.5 with dynamic timing.
While top end was the same (maybe even faster with the boosted 10.5), I felt I had less low-end torque, which was good on the wooden floor but Iwas lacking a bit of grunt on the first half of the carpeted straight.

So for me it will be 7.5 on carpet and astro, and boosted 10.5 on low grip conditions

[Craig W]

ive not raced buggy in ages i would go for 6.5 10.5 and a 13.5t thunder power and you got most thing covered

[colmo]

I couldn't help it, I had to run some numbers.

https://docs.google.com/spreadsheet/...V9hQ1JZTVlDbFE

Note there are a lot of assumptions here. I've used the stats provided by Keda motors, who make cheap inrunner motors, and proved their torque is roughly equivalent for that particular size of motor.

I've then calculated the comparison of a 5000Kv motor (roughly an 8.5) against a 3500Kv (around 13.5 these days), then added a boost component, which presumed that Kv increases by 1% per degree of timing. Timing is assumed to ramp up linearly from a base of 0 at 0 rpms, to the maximum 60 degrees (any more, and the motor can go backwards!) at the maximum rpm.

Note that the boosted motor will lose torque as the timing increases - however, the requirement of torque diminishes as the car's momentum increases (if I've read those Force calculations correctly), which coincides with higher RPMs, where boost is at it's maximum.

The conclusion is the comparison of these two motors is quite close - the boosted 3500Kv actually beats the unboosted 5000Kv by a little in RPM terms - this gain may be diminished by loss of torque.

In a real world comparison, two identical cars, in terms of weight and drivetrain, and geared to the same FDR, with the two motors, would give a definitive comparison.

I've just realised I can use the Novak Brushless Motor chart to do the same comparions, this time with motors specifically for racing cars...check the spreadsheet for updates!