A/trans. hp losses

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morpheus
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A/trans. hp losses

#1 Post by morpheus » Sat Jun 13, 2009 9:19 pm

:? Clarification on losses please. I've had the following HP loss figures given, as estimates, for the following GM trannies.

Powerglide... 18 hp loss

TH-350... 36 hp loss

TH-400... 44 hp loss

Now I realize these are "estimates", as convertor slippage couldn't be measured exactly, soooooo, could I consider these losses apply just for the internal trannies mechanical/hydralic operations? In other words, if the input shaft was a solid mechanical link, these figures could/would apply?

Seems as though the losses wouldn't be so high thru internal slippage, as increased line pressure, better disc/fiber components would "almost" eliminate these causes. I realize driving the pumps takes some power away, but this much?

Thanks for any insight on this subject.......


Alan

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Re: A/trans. hp losses

#2 Post by jmarkaudio » Sun Jun 14, 2009 9:01 am

Internal rotating friction and weight are the cause. It takes HP to turn a heavier part. Slippage can be controlled and should not be a factor.
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Re: A/trans. hp losses

#3 Post by Marty Chance » Tue Jun 16, 2009 6:57 pm

these numbers reflect the power losses on a non modified trans and there are some transmission builders who really know how to lighten up the rotating weight and get the power losses down. I have noticed that a lot of people are quick to point out that the 3 speed takes more hp to turn but has anyone considered how much power you loose going from 1.80 to 1 to 1 at only 250' ? When reading a G meter you can see that your slowest rate of acceleration is in high gear and the bigger the split between gears the longer the recovery time is . This does NOT mean that a 3 speed is the best choice for you , there are other things to consider. This may be an interesting thread- lets hear what you think. Marty Chance
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Re: A/trans. hp losses

#4 Post by jmarkaudio » Tue Jun 16, 2009 11:30 pm

Well, actual weight of the trans is a factor, hard to get a 400 as light as a glide. Worth a little ET. Next, the glide helps cars with too much HP for the suspension, it may be a cop out on fixing the suspension but it works. And I think if the car has the proper gear and converter, the converter will make up a little for the lack of the extra gear.
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Re: A/trans. hp losses

#5 Post by John_Heard » Wed Jun 17, 2009 6:52 am

It's interesting that some of the guys with the top of the line 3 speed stuff like from Rossler are launching in 2nd also. I don't know how many are doing that, but I know a few are - something like a 1.50 1st gear.

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Re: A/trans. hp losses

#6 Post by Marty Chance » Wed Jun 17, 2009 7:45 am

i agree that you will not get the rotating weight down to the same as a P/G but i do not agree that the P/G is worth "alittle ET" . It cost more ET to shift into high gear at 250 feet (550 feet 3 speed) than to have a 3 speed that takes an extra 10 HP to turn but has an intermediate (2nd) gear. Example Nat. Asp classes like Hot Street and Pro Stock (NMRA & NMCA) where they micro manage every HP , have made ET gains by going to the 3 speed transmission. Now on the other hand there are applications that have made gains going to a 2 speed such as Turbo Charged cars where the motor makes power faster by having more load on it or some 1/8 mile cars have gone to a close ratio 2 speed (1.66/1.57/1.48/1.40/1.29) and put much more gear in the rear end but have the same starting line ratio as before with their 1.80 p/g. Example 1.80 first gear with 4.30 rear gear = 1.57 first with 4.93 rear = 1.40 first gear with 5.53 rear gear all of these gear ratio combos have the same starting line ratio (7.74)
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Re: A/trans. hp losses

#7 Post by Chevyfireball » Tue Jun 23, 2009 7:43 am

I reckon the best way to lighten the rotating mass is to get yourself a Chance aluminum convertor. Worked for me.

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Re: A/trans. hp losses

#8 Post by jmarkaudio » Tue Jun 23, 2009 8:58 am

My point was the actual weight, close to 100 lbs difference will help ET. Rotating weight as well, saves HP loss. And I still think the right converter helps overcome the loss of the extra gear, but it's all relative to the combination it's going into as well. And the aluminum converter does look nice...$$$
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Re: A/trans. hp losses

#9 Post by Marty Chance » Tue Jun 23, 2009 9:39 am

thanks for the compliments on the aluminum converter and jmark i do want to point out you always have valuable input and i hope i did not offend you. Marty Chance
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Re: A/trans. hp losses

#10 Post by jmarkaudio » Tue Jun 23, 2009 1:11 pm

No problem. Anytime you have optimized combos, class cars like super stock, comp eliminator... the extra gear does help. And usually those cars have the best suspension setups and race at tracks with better than average track prep. The same with heavy, low powered vehicles. A glide is usually more economical to set up and maintain, more forgiving on bad tracks and less than optimum suspensions, and with one less shift potentially more consistent. As far as John's post on launching in second gear, that is a perfect test for anyone to try to see what their race car wants. I've seen quite a few find their cars gain starting in second, in those cases going to a glide will be even better.
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Re: A/trans. hp losses

#11 Post by morpheus » Tue Jun 23, 2009 6:05 pm

Well considering i'm the one who started this thread, I suppose I should stick my nose in here.

First... Marty thanks for your input so far, and jmark, well we've already sort of spoken on this subject a bit. Even have an offer for him to shovel my snow, if I cut his grass ! LMAO

It appears that it's application specific, as are most things we use. The "majority" of folks have normal door cars, run 11.50-13.50's, maybe a bit faster. It's hard for them to equate to what someones suggests, when they have a RED or in my case an altered, not a maxed out engine-drivetrain, etc.

So lets try to take the middle of the road here. 1/4 mile only, cause we don't have any 1/8 tracks in NJ.

23 altered, 1500#,Gas sbc 406, steel rods, 12.5cr. AFR outa the box 220 cnc, by them, heads, 1020 Holley/Super vic mani, solid roller with wide 112* ctrs, .675/.673, 267/274 @ .050", 1.5/1.6 Sharp rockers, 1 3/4" headers, typical MSD w/7AL2. 15x33x15's with 9" 3.89 rear, 4 link rear.

This is a fun car, yet to be run. Still need tranny/convertor Marty. I run mostly nostalgia races, MANDRA when I join, maybe a few(6) brackets a year. Bunch of old farts just sittin under the shade tree yaking away about what we coulda-shoulda-woulda done :>)

Could care less what it runs et wise as long as it's consistant. So where do I go tranny/convertor wise? Light car, no need for a first gear, probably. No electronics allowed, but t/brake ok.

Would be interested Marty what you'd estimate the hp losses would be on a non-killer bracketmaster or like tranny, all types for the masses to ponder.

Thanks fellas.... should be interesting, cause it a setup that's not on full kill.

Alan

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Re: A/trans. hp losses

#12 Post by jmarkaudio » Tue Jun 23, 2009 7:01 pm

Grass is getting long, hurry on down.... :lol: :lol: :lol:
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Re: A/trans. hp losses

#13 Post by morpheus » Tue Jun 23, 2009 8:42 pm

jmark.... stuff your grass and feed it to da gators ! It's been raining up here in Jersey for the past damned 16 years. Man I got me own green problems here. Darned polar caps melted and dumped it all on the east coast....I haven't seen it rain this long a time since I was in 'Nam. LMAO

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Re: A/trans. hp losses

#14 Post by Marty Chance » Wed Jun 24, 2009 8:06 am

no doubt about it , I recommend a p/g for your application , as for power loss - most p/g only take 20-25 hp to turn.
As for the converter , give me a call and i can give you an estimate and what i would design as i try to keep my part of this board more on the "info" side and less on the NEAL CHANCE CONVERTER sales side because i want everyone to be comfortable with tech questions regardless of who's brand they are loyal to. (316-542-9869)
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Re: A/trans. hp losses

#15 Post by hsutton » Sat Apr 03, 2010 12:50 am

That altered should be real easy to get moving no matter which kind of transmission you have. At 1500 lbs. the 'glide will probably be as fast as a T-400 and be more consistant to boot. Sounds like a very good racecar. The gear, tire and engine size seem very well matched. Either transmission would work well but a good 'glide will withstand more abuse than an average Turbo.

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