Schumacher Corner
11-05-2007, 04:36 PM
Hi Skiddins,
Generally a different charge rate will make zero difference in performance. 1 amp, or the maximum - the output will all be the same.
BUT - I suspect one of two other lipo eccentricities were in play there:
1) Temperature
Cold packs don't perform as well as warm ones. If the pack started at the ambient outside temp early in the day (50F) it would be a little sluggish. But after a few discharge cycles (and warming ambient temps) to build a little heat into it (maybe 80F?) it would have felt stronger out of the turns and faster down the straight. A lipo's peak performnce temperature is about 100F, and they usually start showing a noticable drop in performance around 60F or below.
2) Are the packs brand new?
A pack's performance will IMPROVE over the first 20 cycles or so. What you see on run #1 of a new pack will be different than what you see on run #20 and up. I don't know what crazy technical chemistry is going on inside the cells to cause it, but it's a documented reality that it takes around 20+ cycles to "break in" the pack to it's peak performing level. It's easy to see the difference between cycle 1, 2, 3 and so on on a graphing discharger, but I suppose a racer with a very discerning eye might be able to see improvement from one run to the next?
I'd presume it was #1 more than anything, but I can assure you charge rate didn't have anything to do with it. :-)
Generally a different charge rate will make zero difference in performance. 1 amp, or the maximum - the output will all be the same.
BUT - I suspect one of two other lipo eccentricities were in play there:
1) Temperature
Cold packs don't perform as well as warm ones. If the pack started at the ambient outside temp early in the day (50F) it would be a little sluggish. But after a few discharge cycles (and warming ambient temps) to build a little heat into it (maybe 80F?) it would have felt stronger out of the turns and faster down the straight. A lipo's peak performnce temperature is about 100F, and they usually start showing a noticable drop in performance around 60F or below.
2) Are the packs brand new?
A pack's performance will IMPROVE over the first 20 cycles or so. What you see on run #1 of a new pack will be different than what you see on run #20 and up. I don't know what crazy technical chemistry is going on inside the cells to cause it, but it's a documented reality that it takes around 20+ cycles to "break in" the pack to it's peak performing level. It's easy to see the difference between cycle 1, 2, 3 and so on on a graphing discharger, but I suppose a racer with a very discerning eye might be able to see improvement from one run to the next?
I'd presume it was #1 more than anything, but I can assure you charge rate didn't have anything to do with it. :-)
http://www.rcracechat.com/vb/showthread.php?t=37226
People are more interested in LiPo experiences and info now that the BRCA has approved them for the new 'Pro-Stock' class, but this will be at national level from the beginning of next years summer season, April 1st.
This has also filtered down to other race series etc which are mentioning that they will allow it in all classes etc.
Skiddins
11-05-2007, 04:39 PM
11-05-2007, 04:41 PM
11-05-2007, 05:24 PM
Thanks guys. I klnow PW always ran the diff tighter on foam tires in mod but I just wanted to make sure the same is the case in stock.
11-05-2007, 05:48 PM
... i've been running them really light lately. this summer i ran a 35t front pulley and decided the extra axle rotation would be enough pull, so i ran it loose (but not slipping). i noticed that the light diff makes it a little softer on center, at the expense of some added off power hook. i think it's all how you're setup, but the loose diffs last alot longer than jamming them down. i'm back to a 1:1 axle ratio, but have kept the light diffs for both, vegas and the classic. i also spend an excessive amount of time off power for a stock racer. as it stands, though, they are set about the same, and actually spin a little after you let them go.
also, i handled mcgoo's car a bunch in vegas and i don't recall either end being extra tight. (<< alright wise-guys, have at it
) maybe he can confirm this.
11-05-2007, 06:28 PM
I ran Mcgoo's set-up last week and had steering and traction everywhere. Both diffs were set "Medium". Car was dialed 
11-05-2007, 06:30 PM
11-05-2007, 06:35 PM
as posted, the general rule of thumb has been to run the front a bit tighter. but of course i'm going to throw a curve ball at you...
... i've been running them really light lately. this summer i ran a 35t front pulley and decided the extra axle rotation would be enough pull, so i ran it loose (but not slipping). i noticed that the light diff makes it a little softer on center, at the expense of some added off power hook. i think it's all how you're setup, but the loose diffs last alot longer than jamming them down. i'm back to a 1:1 axle ratio, but have kept the light diffs for both, vegas and the classic. i also spend an excessive amount of time off power for a stock racer. as it stands, though, they are set about the same, and actually spin a little after you let them go.
also, i handled mcgoo's car a bunch in vegas and i don't recall either end being extra tight. (<< alright wise-guys, have at it) maybe he can confirm this.
... i've been running them really light lately. this summer i ran a 35t front pulley and decided the extra axle rotation would be enough pull, so i ran it loose (but not slipping). i noticed that the light diff makes it a little softer on center, at the expense of some added off power hook. i think it's all how you're setup, but the loose diffs last alot longer than jamming them down. i'm back to a 1:1 axle ratio, but have kept the light diffs for both, vegas and the classic. i also spend an excessive amount of time off power for a stock racer. as it stands, though, they are set about the same, and actually spin a little after you let them go.
also, i handled mcgoo's car a bunch in vegas and i don't recall either end being extra tight. (<< alright wise-guys, have at it
) maybe he can confirm this.LOL - Goetz tried to handle my car a bunch, but he was rooming with Caster...so ya'll might want to ask Caster what Goetz thought of his diff.....
I wouldn't say my diffs are tight, they would be more on a med/loose side. I have really liked the Schumacher diff lube combined with carbide diff balls (not ceramic). Once I get it all built up I tighten it up the diff screw until its snug and then i back off the screw about a 1/8 turn for the front and a 1/4 turn for the rear.
One thing that PW instilled in me is that diffs are key in these cars. I have spent more time prepping these diffs than any other car i have ever ran, and the dividends have paid off. I haven't had to rebuild by diffs as much as I used to.
11-05-2007, 07:27 PM
R any of you at or under weight limit that are NOT running lipo? If so, what electronics/motor combo are you running?
11-05-2007, 07:29 PM
hey guys, i'll be going to a brand new track with nice fresh carpet. any suggestions for mod foam on green carpet. or should i think about rubber 10.5 instead.
11-05-2007, 10:33 PM
Need some help??
Hey guys getting ready to put the LW bulkheads on and with just the 2.5 carpet chassis and all electronics (no topdeck/bumper/arms/etc., just all wiring/electr./bottom chassis) the weight is 419grams. Does anyone know the weight of the carpet chassis?
11-05-2007, 10:46 PM
Registered User
11-06-2007, 04:09 AM
I'm running a JR8800 servo, KO Hara Twister 2.2 speedo, CO27 stock motor,
Carpet chassis/topdeck/shocktowers, LW bulkheads, titanium screws/ballstuds, Parma Mohawk body, and BSR double pink tires on JACO Prism wheels and my car was 1458g. Thats with a EP4600 and a motor fan/mount.
Carpet chassis/topdeck/shocktowers, LW bulkheads, titanium screws/ballstuds, Parma Mohawk body, and BSR double pink tires on JACO Prism wheels and my car was 1458g. Thats with a EP4600 and a motor fan/mount.
Last edited by Big Features; 11-06-2007 at 04:11 AM. Reason: content
11-06-2007, 06:40 AM
Correct diffs make a huge difference to how the car handles.
It wasnt till about this time last year i was having problems with my car then running a Xray T2. I was talking to probably there best team driver over here in the UK about it. He looked at my car and said the set up was pretty much the same as his etc the rear diff would be causing the problem. To be honest i didnt even think it would matter to much if the diff had a bit of grit in it. Just to proove the point i had a new built up diff in my box i swapped it over he set the tension of it which was pretty much the same as what i had anyway and then did my next run. I couldnt belive the difference in the car it felt the best it had ever done ever since then the diffs in my cars get rebuilt etc very regular.
Also on this point im interested to hear why some of you have been running your diffs on the Medium - Loose side ? Is this just with foams or with rubber aswell ?
It wasnt till about this time last year i was having problems with my car then running a Xray T2. I was talking to probably there best team driver over here in the UK about it. He looked at my car and said the set up was pretty much the same as his etc the rear diff would be causing the problem. To be honest i didnt even think it would matter to much if the diff had a bit of grit in it. Just to proove the point i had a new built up diff in my box i swapped it over he set the tension of it which was pretty much the same as what i had anyway and then did my next run. I couldnt belive the difference in the car it felt the best it had ever done ever since then the diffs in my cars get rebuilt etc very regular.
Also on this point im interested to hear why some of you have been running your diffs on the Medium - Loose side ? Is this just with foams or with rubber aswell ?
11-06-2007, 06:49 AM
Adam and Shawn,
Package is on it's way.
Wes
Package is on it's way.
Wes