Why does everyone say that a 700R4 loses 20% power? Every racer I have talked to, numbers I've checked out online, and a friends dyno run would suggest otherwise. I have seen no proof as to why this is said. I have also read that that 20% number is just an average number assigned to automatic transmissions in general, NOT all. I would just like some proof to the statement.

If that were the case, I have a hard time believing that any automatic tranny would make it into production because of fuel mileage.

Between an auto and manual firebird formual 305 TPI, the auto (at the crank) made 210 horsees (th700r4) and the manaul makes 230 horses at the crank. Now YES this is at the crank, but I have seen MANY Dyno Tests results, some of which posted in various places at this site and others that have PROVED that the autos lost roughly between 5-10%.

This would suggest that the loss is not just because of the transmission and may be because of the rear, etc. I just don't think the transmission is the only reason.

Let the flame (or flag) come up. I know its inevitable, but I want some proof!

thanks!

 

I think you misunderstood. People quote percentages of DRIVELINE loss. That includes the tranny, driveshaft, rear, etc. The entire driveline loss for an auto may be about 15-20% or whatever and 10-15% for a manual, but this IS including the rest of the driveline, so the tranny is only a percentage of the percentage, lol.

 

I think the reason being is because the 4L60E out of the fourth gens are rated at 18-22% drivetrain loss with an automatic and 16-18% using the T-56 manual. Count this with the aluminum driveshaft as well. Isn't the 4L60E the 700r4 with beefier internals? Hope that helps.

 

thats insane to think those numbers could be correct on just a transmission though, or even through a drivetrain (especially if the whole thing is built) that would mean a 1000 hp car, is only putting down 750 to the ground....I find that very hard to believe.

Also that would mean that a 92 Z28 would lose horribly to a stock first gen DSM. Which they don't. So there is something up with those numbers.

Oh yah, if the whole drivetrain is true, why is is that the 2002 camaro SS (and firebird equivalent) can do a quarter mile VERY quickly for a stock car and only have 325 horses? theres no way with 20% drivetrain loss theyd be able to make it down that track as quick as they do, with the amount of weight those cars have.

cheers

 

the amount of power to spin the trans and entire drive line is going to be fixed, say XX amount of HP not a variable like XX% of the HP produced. the way you're appling it the amout of lose goes up as HP goes up.

 

Right. Ede nailed it.

Think of it as a percentage of you cars particular power output.

So...

If a stock thirdgen L98 gets engine dynoed at 245 horsepower, and then loses 20 or 30 horsepower because thats what it takes to "spin" the drivetrain then it is in effect losing 8 - 12 percent of its power.

If a modded thirdgen L98 gets engine dynoed at 300 horsepower, and then loses 20 or 30 horsepower because thats what it takes to "spin" the drivetrain then it is in effect losing 7 - 10 percent of its power.

In actuality, the more power your combo is making, the LESS it loses to "spinning" the drivetrain.

 

One of the reasons why they run such great times is because #1 that 325hp rating is bogus and LS1's make about 350 at the crank and #2 they have very flat power curves. 15 to 20 percent loss is really really good when it boils down. There are a tremendous amount of moving parts in a tranny that create dry friction, and viscous fluid friction. Auto trannys suffer a little more than manuals hence the higher loss ratings. Both types of friction are lost energy that cannot be put to the ground. If you think that is bad, just think that your N/A engine is only between 25% and 40% efficient.

 

LT1's have a flat torque curve, but LS1's don't.

LS1s run 13's stock in the quarter because they put down about 290-300rwhp on a chassis dyno. and for the weight of the car, that much of horsepower should get you low 13 second quarter mile.

 

An LT1 makes its torque a bit faster in the curve but the LS1 curve overall is still pretty flat. My LT1 is no match at any speed for my roomates SS.

 

my LS1 makes well over 300 tq from less than 2k rpm all the way to more than 6k.

 

Thanks 25th. I needed some backup.

 

Ok, I understand that the drivetrain uses said amount of power to turn and that power is then lost when measuring from the wheels...but 20%?? I'm sorry, unless I see numbers proving that I just can't believe that such a high percent of our power is lost.

For instance, My brother has a 1st Gen DSM, Turbo, AWD DOHC (manual)...all that. My car is a 305 92 Formula (th700r4). My car isn't stock but it was when I got it and I could probably take him, maybe not all the time but I could.. not by all that much, but I could and now that I did a full header back system I would smoke him!..and he drives pretty good. Now take our stock numbers, 210 HP with 215 lbs of torque or so (and that is fact, we just got the new engine), and mine 210 stock with 285 lbs of torque. Now I know torque makes up for a lot BUT if your numbers are correct THEN His car losing 10 percent as a manual would yeild 189 HP, and mine at 210 Stock with my auto would yeild 168 HP with the 20 percent loss. Now, even with torque, I would not be able to beat him, also because he's AWD. So I just can't believe those numbers...because I could BEAT him. I couldn't do that if these numbers were correct. And assuming those are correct and his car weighs 500 lbs lighter...he would SMOKE me, but he can't! so

cheers

 

60 more RWTQ definitely makes up for 20 less RWHP.

 

Yes, 60 torque does make up for 20hp less BUT does it make up for 20 less HP, 500lbs and him in an AWD?? I think not

 

you are not going to get the answer you are looking for by arguing with people on the boards, either go look for some stock dyno numbers or get your car dynoed and do the math.
Also, dont those all wheel drive cars loss a **** load of power through the drivetrain, i think that 10% claim is alittle on the light side for the the DSM.

 

Arguing Lol You call that arguing?? Hmm, ok. Anyway.....I was just stating my thoughts, and numbers I've gathered...so I am doing the math. But good point on the AWD loss, I'm going to do some more checking on that too see what their loss is.

 

Their loss is tremendous compaired to a 2wd vehicle. But their gain is traction. They really suffer at higher speeds when all of that parasitic loss catches up to them. Plus you can beat you buddy from the get go because you are making more power than him. Your car has a flat power curve and you make your peak torque early in the revs as compaired to your buddy who has to wind his up. Well why he is winding his up you are beating him. For the same reason why a 240V8 will be faster than a 2404 cylinder. They area under the power curve for the V8 is HUGE compaired to the peaky 4 banger. So your buddies car may make similar power to yours but only at a small RMP span, whereas yours make its peak power over a large RPM span.

On a side note, they claim that newer cars have a driveline efficiency of 90% but I am skeptical a bit. That is what they tell us here at school for any driveline calculations.

Also if your torque converter is not locked than the power losses increase as rpm does. In a viscous situation the faster go the more friction there is. That is how shocks work. This is not true for dry friction where you just have to overcome the weight of whatever it is you are moving.

 

Awesome. Thanks Shifty Capone, lots of good info there, and it makes sence...AND you stated reasons why That's what I'm looking for. Ya, I knew about the power curve, but I just didn't think it would benefit me all that much vs him if we had the same power going through (even though I have more torque) with him in an AWD and with a lot less weight. I knew I would pull on him at higher speeds due to his loss, but I figured that wouldn't matter as much in a 1/4 time since he would have a greater amount of traction. So all in all, that makes sence, and I would tend to agree more with the 90% efficiency on new trannies..I wouldn't think the 700R4s would be THAT much worse. Anyway, thanks

Cheers

 

I've always heard that the 4WD cars had alot of rolling resistance, which I guess is why they lose more in higher speeds. I guess thats why they've created four wheel drive systems that transfer torque and poewr only to the back wheels when your already movin. Pretty innovative stuff. And I also still think that 20% is too high of a number for how fast the newer SS and WS6 can move. Even with 360 Horses (advertised 320). *** I hope they brind one of those cars back.....But I digress..

BTW rode in a WRX (not STi) that lil car can move! I was impressed.

cheers ya'll

 

On my old 88 bronco 2 it was a night and day difference between rwd and 4wd. You could feel the engine lugging really bad in 4wd.

 

Well think of it this way. GM rates the LS1 at 350hp for the vette. This is the same motor that is in the f-bodies but it was a lower rating because GM can't advertise it to have the same as their bread and butter. Now the T-56 has around 15 to 18 drivetrain loss. So if you do the math and take 300 to the wheels times 1.18 (adding 18% loss) you get 354 at the crank. Or right at GM's power claims. Some vettes even dyno LOWER than f-bodeis because of their unique transaxle assembly in the rear. It was a bit more loss than your stand alone bolt on T-56. They are still faster because they weight less and are more aerodynamic. Just look at dyno numbers of guys running 15's. You will see that they put anywhere from 150 to 200 to the wheels. 300 to the wheels now takes you farther and makes you capable of running the times that LS1's do.

 

Minor detail I know, but what the hell is a first gen DSM???

 

If I'm not mistaken, the F-Body LS1 has iron heads and the Vette has alum heads, and a different cam. I could be wrong, but I thought that was how the two differed. At any rate, who cares what the loss is, or why the numbers aren't adding up, you are NOT getting your *** handed to you by an import. I don't care what the numbers say about any car out there, all I care is who comes through the lights first.

 

Nope both are identical minus exhaust manifolds and oil pan. The later LS1's got the LS6 manifolds which made them literally identical in power output towards the end of their productiuon run. Same for the LT1 except the vette, beside the manifolds and oil pan, got 4 bolt mains. Both LS1 version shave 6 bolt mains and share everything alike. Some late run 02 f-body LS1's even came with the LS6 block. My roomate and I have yet to check on that one though to see if he has one in his. His was one of the last cars to roll off the line. You are thinking of the F-body/vette and Imapalla differences. The B Bodies (all SS impalla's and LT1 equipt Impallas) recived an Iron version of the LT1 head and had a bit smaller cam with more LSA than the F-body and vette heads and cam that were identical.

 

Hey Pat. The First Gen DSM's are in my opinion some of the fastest stock imports (or to be precise, DOMESTIC Imports, since they were built in american factories, in Normal, Illinois) to roll out of production for their time. They were the Mitsubishi Eclipse, Chrysler Laser, and the Eagle Talons..the talons were the faster of the two as far as I know. The Talons could come with a 14b Turbo DOHC 16 valve AWD Package...rated between 195 hp. They also had slightly more torque than HP (roughly 205lbs)which was kind of odd for an import. Either way, they are faster than the Second Gen Eclipses and talons....which used a smaller turbo running at max boost, whereas the 1st gen wasn't at max boost. My brother has the Eagle Talon model stated above...fastest of the bunch. I may not have included all the info here...but I'm tired and I put as much as I can think of. Night



P.S. when I call them "fastest" I"m not including the OUTRAGIOUSLY overpriced Imports such as NSX's and skylines...or any of the newer cars (i.e. EVO)

cheers

 

No problem there Raven. I just could'nt figure out what cars you were referring to using the term "DSM". Yeah I'd have to agree some of them are pretty damn quick. I had an eclipse gsx turbo and a nissan 300zx twin turbo both give me a really decent run for my money in my 69 Camaro. If I would've been in my 89, there would've been no contest, they would've blown my doors off in that car!

 

whoo hoo nice convo about the power loss. I think I will be agreeing with ede on this one. how would adding more power make the amount of power your drivetrain suck up go even higher? that really doesn't make any sense at all if you think about it.

Why is it that subaru and mitsubishi are holding on to the all time four wheel drive thing? I understand their evo and STi are both based off of rally cars, but why not make it so you can shut off all wheel and just run on front or all wheel, or back and all wheel.

cheers, nice convo, this is interesting



BTW thats plymouth laser, not chrysler ravenshorn

 

I'm no genius.. but from what I understand... there will be HP measured at the flywheel vs. the HP to the wheels. The HP to the wheels will be a smaller # due to energy used to operate the entire driveline (there IS resistance all along the driveline). Please correct me if I'm wrong.

 

oh your very correct, it does lose poewr, the debate here, is some say you lose 20% indefinately regardless of how much power your engine makes or how your tranny is built, and others (like myself,ede, and ravenshorn) who think that there is a set number your drivetrain takes up, and doesn't scale as your power scales.


cheers!

 

Wow, did I call it a chrysler? haha Sorry bout that. Anyway, I was reading through the posts again, and I would have to say that Ede and D Stroy both nailed it. I didn't quite catch what they said earlier but it makes complete sence. X-wolf and I were discussing how it didn't sound right at all that the same vehicle with 400 hp would use so much more hp to spin the same drivetrain than if it had only 240 hp. It didn't make sence. SO thanks Ede :

Thanks

 

There is truth and fiction to this. Gears generate dry friction which remains the same no matter what HP the motor in front of it is putting out. However because there is tranny fluid present there are also viscous friction losses that DO change as force changes. Since manual tranny's just have small viscous losses in a thin boudary layer on the gear teeth, plus a helical gear configuration, they provide a higher energy transfer and get lower percetage losses. The viscous losses are minimal and are for the most part negligable. In an automatic tranny where the converter is not locked there is a complete viscous friction system in there that gets the car moving. As power and rpm increase so does the percent loss. That in combination with their planetary gear systems equate to a higher energy loss that increase when power increases. This is the same as a shock absorber works. The way the rebound drastically depends on how fast and with what force is applied to it. The harder to press the more force there is.

 

ok maybe it does scale, but i don't believe that much. Thanks for the info.

 

Ummm... Your Formula has 210 (or 205 but whatever) NET hp... Everything past some year in the early seventies is rated as net hp... that means at the wheels already... driveline accounted for...

 

Ok, I have been told otherwise, i thought gm rated all thier vehicles at the wheels also but I was told its at the flywheel over at camaroz28. I don't know what to believe now =/.

 

Its at the wheels now for sure... When the exact change took place I'm not 100% sure of... But it was back in the 70's for GM...

 

Their ratings are 100%, absolutely at the flywheel. Before, engines were rated with no accessory drag, etc. Now they are rated exactly as they are put in the vehicle.

 

its been stated already, but no that is not the case. Thats at the crank with everything attached. if it was at the wheels with everything accounted for, these things would probably be a bit faster.

cheers

 

Ok so which is it? Flywheel horsepower or rear wheel horsepower ratings?


Take the lt1 for example, gm rates its camaro z28 /w lt1 engine at 275 hp

Is that flywheel or rear wheel?

 

GM and just about every car manufacturer rates their engines at the FLYWHEEL.

 

Thought so, thanks.

 

****, my bad...

 

This is absolutely correct. Also, net hp is measured at the motor without any accessories on it; not to the wheels. GM rates their vehicles with full accessories.

 

and on the newer vehicles thats alotta accessories!! I only have 3 on mine

cheers

 

Although, keep in mind, not all the specs they put out are always accurate. GM for 1 likes to underrate most of their engines big time.

 

Yea they did this for the f-bodies mostly. All their other ratings for other cars are pretty accurate. It helps sales and keeps insurance down to know that you have a 4 passenger car with only 300hp When we all know that everyone dumps the two rear seats and it takes more than 300hp to run high 12's.