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.:thumbsup:

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...:thumbsup:

[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!:thumbsup:

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

[samd]

Silver can!

[TARTMAN]

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

380 silver can(grasshoper style) hehe:thumbsup:

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.............:thumbsup::woot::(:confused::lol :

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:woot:

[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!:thumbsup:

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


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:woot:

[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]

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 :thumbsup:

[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/ccc?key=0Al5B3MQ2F4JTdC1DUkFrMlZteWRoeV9hQ1JZTVlDb FE

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 (http://www.teamnovak.com/products/brushless/motor_spec_chart.htm) to do the same comparions, this time with motors specifically for racing cars...check the spreadsheet for updates!

[colmo]

I've added a comparison to the spreadsheet of a non-boosted Ballistic 7.5T to a boosted 10.5T, using the same assumption of 1% Kv gain per degree timing.

The result is while the RPM range of the 7.5 is linear, the 10.5T is not - comparatively, it initially yields less RPMs at lower voltage, but more at higher voltage - the Kv ramps up steadily through the range as the timing is advanced more and more.

The effect is much like a little negative expo on the throttle, which would give a boosted motor a 'softer' feel, of less punch, yet excellent top speed.

Link to Google Doc again: https://docs.google.com/spreadsheet/ccc?key=0Al5B3MQ2F4JTdC1DUkFrMlZteWRoeV9hQ1JZTVlDb FE

http://www.worldinfocus.net/Pics/7.5T_v_10.5T%20boosted.png

[Timee80]

This is what I was talking about. Finally someone understands me!

[colmo]

One other thing to keep in mind - of the 60 degree additional timing you can boost by, you must include mechanical timing of the motor. Most motors have some dialled in automatically and some can be adjusted too. The old Speed Passion (Feigao-made) motors have a fair amount of timing dialled in, and I recall the LRP/Nosram x11 had quite a lot. It appears that 30 degrees is the normal 'zero' for brushless motors - they don't perform well with less.

The touring car guys, who know more about this than off-roaders, know the Speed Passion v3 and GM motors have zero timing set mechanically. I'm not sure what other motors do too.

Note that the Ballistic motors have 30 degrees of timing as standard (the usual), so the additional 60 degrees of boost timing aren't actually attainable. I'll recalculate to add only 30 degrees boost timing - see below.

http://www.worldinfocus.net/Pics/7.5T%20v%2010.5T%20boosted.png

[James]

I did a fair amount of testing between different winds/boost etc.. Came to the conclusion just to stick with a 7.5 or 8.5 in 2wd with no or very little boost.

[colmo]

It seems the norm for boosted brushless setups are 30 degrees mechanical timing, and up to 30 of boost plus turbo.

See the Hobbywing Xtreme Stock manual (which states true degrees of timing), giving 21 degrees of boost, plus a further 8 of turbo, for a total of 29:

http://www.hobbywing.com/upload/manual/HW-09-XST.pdf

In a situation where there's no motor limit, the greater efficiency of a lower wind motor and no ESC trickery, plus the simplicity of setup, makes boosted motors seem unnecessary. If traction is low, dial in some negative expo or lower the punch setting on the ESC.

The one advantage of boost is adjusting for different tracks without changing motor - just leave your gearing alone (set for technical tracks), and dial in some boost to give the car the legs on the longer straights of a bigger track.

[stumpiey]

iv ran a turbo'd 10.5 and a non turbo 6.5, on bigger outdoor tracks i would use my LRPx12 6.5t but indoors it's to much so i use a 10.5 which i feel a bit is better for my driving, plus coming from TC i understand how to get some real ponies out of a 10.5 set up:thumbsup:

[ianjoyner]

I did a fair amount of testing between different winds/boost etc.. Came to the conclusion just to stick with a 7.5 or 8.5 in 2wd with no or very little boost.

How come? :)

[colmo]

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 :thumbsup:

My comparison of the Ballistic 10.5 with 30 degrees of dynamic timing boost to the 7.5 without supports this (limited as it is with massive guesstimaton!); similar top end, with the mod motor giving more mid-range.

I'm wondering if dialing in positive expo on the throttle would 'flatten' the curve and give more punch?

[TARTMAN]

so technical...

I am oldschool style. fast motor, sort the grearing and use the throttle thumb to sort it....

works for me.............

wil prob try the new stuff soon, but only been back in it since sept this year after 22 years out..... so early days...............:o:o:o:o:woot::):drool:


My comparison of the Ballistic 10.5 with 30 degrees of dynamic timing boost to the 7.5 without supports this (limited as it is with massive guesstimaton!); similar top end, with the mod motor giving more mid-range.

I'm wondering if dialing in positive expo on the throttle would 'flatten' the curve and give more punch?

[Timee80]

It would be nice to have one motor you could use on all tracks in all conditions, achieved by simply changing punch / boost + turbo timing. I think a 10.5 would be about perfect once people more knowledgable than me have fully sorted the programming side of things. Ive tried a 13.5t boosted in 2wd too but I had to use alot of timing to gain enough from the motor which made acceleration feel "funny"- I dont know how to describe it really.
I think the strange feeling comes from when the buggy is in the air/landing because rpm's are all over the place.
The yanks may know better than us because theyve been using slower motors for ever?

[samd]

I'm not sure this means anything with just assuming a certain kv raise per deg off boost.
Also the esc dosent vary voltage, it's constant, motor speed is determined by the + - wave, and boost timing speedos add timing to motor rpm not running voltage.

I think:lol:



I've added a comparison to the spreadsheet of a non-boosted Ballistic 7.5T to a boosted 10.5T, using the same assumption of 1% Kv gain per degree timing.

The result is while the RPM range of the 7.5 is linear, the 10.5T is not - comparatively, it initially yields less RPMs at lower voltage, but more at higher voltage - the Kv ramps up steadily through the range as the timing is advanced more and more.

The effect is much like a little negative expo on the throttle, which would give a boosted motor a 'softer' feel, of less punch, yet excellent top speed.

Link to Google Doc again: https://docs.google.com/spreadsheet/ccc?key=0Al5B3MQ2F4JTdC1DUkFrMlZteWRoeV9hQ1JZTVlDb FE

http://www.worldinfocus.net/Pics/7.5T_v_10.5T%20boosted.png

[lochness42]

I didn't like supercharger/turbo in TCs. It used to upset car when it kicked in.

[TARTMAN]

I find in the 2wd, when the turbo kicked in on the strait it was a little unsettling and just meant harder braking and that unsettled it again.

I will stick to no turbo and a madder motor.... also, i think that a turbo'd/timed motor will get hotter than a mad one just doing its thing...
Might be wrong on that thou.....:confused:.....???? Answers on a post(card) please lol...:thumbsup:

I didn't like supercharger/turbo in TCs. It used to upset car when it kicked in.

[Timee80]

I didn't like supercharger/turbo in TCs. It used to upset car when it kicked in.

Surely that depends on how much timing advance is used and how aggressive it is set up?

[Timee80]

Agreed, a milder motor will get hotter when turbo settings are used but its a small price to pay if you can use one motor everywhere and have a buggy that is more driveable at lower speeds. I tend to get nervous on the rostrum (especially if doing well) and having to tickle the throttle with a quick motor to get the right speeds in the infield becomes harder when your shaking like a sh!tting dog:)

[h0m3sy]

Agreed, a milder motor will get hotter when turbo settings are used but its a small price to pay if you can use one motor everywhere and have a buggy that is more driveable at lower speeds. I tend to get nervous on the rostrum (especially if doing well) and having to tickle the throttle with a quick motor to get the right speeds in the infield becomes harder when your shaking like a sh!tting dog:)
:lol::lol::lol::lol:

[colmo]

I'm not sure this means anything with just assuming a certain kv raise per deg off boost.
Also the esc dosent vary voltage, it's constant, motor speed is determined by the + - wave, and boost timing speedos add timing to motor rpm not running voltage.

I think:lol:

Oops, yes, you're right. Brushed ESCs do vary voltage, brushless vary pulse frequencies, so voltage in this case is nonsensical. I'll change the X axis to percentage of maximum power, as I can't think of anything else to put there that means anything!

[jaywestwood]

I didn't like supercharger/turbo in TCs. It used to upset car when it kicked in.
Change the turbo delay up.. 10.5 with generation 3 speedo is faster than a non boosted 7.5 motor.. If you also turn the start rpm up it will be smoother of corners and will only kick in when your ready for it

[guinness]

in my trf201 i been running a 6.5t pure evolution together with a stock no timing esc for a wile,and i must say that that motor was to much to handle,then i swapped to a 10.5t lrp vector x11 and my times improved big time but not really enough quick/torque in the straight ,so now i just fitted a 8.5t bullistorm and i will race with it this coming friday ,i hope this would be a good middle ground.

[RogerM]

In offroad I have found that using very little normal dynamic timing but lots of "turbo" timing, with very slow rates of timing rise and the lowest possible start RPM gives a car that is lovely and smooth to drive and just as fast as it would be on a faster motor.

As has been said previously be careful of the mechanical timing on the motor and make sure you keep the total timing to sub 60deg (I use 58deg as my peak value, just in case I am a fraction off on the mechanical timing).

[Si Coe]

I've been running turbo'd 10.5's in 2 and 4wd for the whole last season.

At the end of the straight they can hold their own, but they certainly don't have the same punch as a 6.5t. In particular out of slow corners they lack poke, its better further up the rev range though.
I have found a few problems with certain types of jump due to that lack of initial grunt because you can't just gun it to get a good takeoff.
However, overall reckon I drive better with them - I'm a throttle jammer anyway so the softer config just tames my natural tendencies. In 2wd in the wet its certainly better - for 4wd not so much.

Oh, and they run hot. Really hot. Really really hot! Does depend on the esc though - my GM seems to offer the most boost but runs coolest, my LRP has less boost but things get a lot hotter.