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Old 06-13-2009, 09:20 PM
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Question, in anticipation of an argument with an idiot

I am anticipating an argument with an idiot.....I know it's coming. We have the same car. Similar motors.

So the question is....

RWHP number....

1. From what I understand a manual transmission is more efficient than an automatic. How much difference in HP, percentage wise, is the difference between automatic and stick.

2. How much is an AC delete worth in terms of HP. I'm running stock AC set up. It's a street can and I have to be comfortable.

I just want to slam this idiot to the ground when he brings it up.

The primary difference between the two cars are those two things I mention, what would you anticipate they are worth in terms of HP?

Thanks.

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Old 06-13-2009, 10:29 PM
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Both of these are hard to quantify, but the difference will probably be very slight.

A manual transmission has more efficient power transfer because the clutch has a more direct engagement, but the torque converter in the automatic usually gives it some advantages off the line. Then you have to factor in how good the person is with shifting the manual transmission. The manual gives more control, but requires more skill.

In most cases there isn't that much difference in performance. The automatic often wins out in a straight line race because its less dependent on driver skill off the line and for shifting. However, if you are looking at road race, the manual might be better because most automatics don't make it easy to shift manually and keep it in the right gear for best power.

The AC delete probably has no measurable effect on performance, since an AC compressor that is turned off doesn't offer much resistance. However, removing the AC parts would give a weight advantage.

Bruce
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Old 06-13-2009, 10:49 PM
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On the trans difference, 4-5% in high (1-1) gear because you are not rotating as much weight or turning a hydraulic (front) pump. AC is nothing when turned off, it is basically an idler pulley. As stated before it may show in track times because of system weight, but not on the chassis dyno.
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Old 06-13-2009, 11:05 PM
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Forgetting about off the line advantages, the auto absorbs more hp because more mass in the plantetary gear sets is being turned instead of a mainshaft and countershaft in a manual. You didnt say what car, as newer auto trans are more efficient now than years ago. But that is why around 3-5% more is lost with auto.
As said earlier AC only burns a little power when on. When off the pump is like another idler pulley.
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Old 06-14-2009, 06:37 AM
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This is pretty much what I suspected. This guy is all about dyno numbers. He likes to take completely oddball comparisons that fit his view of the world. So just double checking my position before I have to deal with him.
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Old 06-14-2009, 06:45 AM
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Bit of advise......Don't argue with an idiot....when you do, you become one too........
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Old 06-14-2009, 06:51 AM
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Quote:
Originally Posted by poncho62
Bit of advise......Don't argue with an idiot....when you do, you become one too........

It's a sport. I don't take it seriously. Just all in fun.
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Old 06-14-2009, 07:53 AM
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a slipping trans conv. is inefficent, a locked one is basically as efficent as a clutch. If the AC is on then it can take about 20hp in some cases, if it is off then it is basically just added weight, which can be around 300lbs.

I'd love to hear exactly how this argument goes- keep us posted.
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Old 06-14-2009, 08:09 AM
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Quote:
Originally Posted by ap72
a slipping trans conv. is inefficent, a locked one is basically as efficent as a clutch. If the AC is on then it can take about 20hp in some cases, if it is off then it is basically just added weight, which can be around 300lbs.

I'd love to hear exactly how this argument goes- keep us posted.
Not really an arguement, but some guy who keeps making comparisions that aren't apt to fit his view of the world.

His new favorite thing is a car that his friend has which is manual with no air, and he's comparing it to a car that is auto with air.

So my position is going to be.....throw away 25 HP for the difference, now the difference isn't so great. Not a strong position, but enough to twist him into convulsions.

The second part of his argument is that he's comparing the two, one has CNC ported heads, the other as cast. Brodix themselves stipulate that there's a 30 HP difference between the same head CNC'd or not CNC'd. So let's pile that on the final number.

So now we have 55 HP give or take that comes off the top of one car, in comparison to the other.

The funny thing is I don't care about dyno numbers as they never really tell the whole story, to a point. He lives and dies by them, which, in and of itself is amusing.
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Old 06-14-2009, 08:24 AM
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If this is an ongoing debate between aquaintances about whose car is is faster, harder, better..you know.. , I'd offer to find a 1/4 mile track somewhere and see how it all comes out in the real world.

As this was not really a technical question, but still related to an automotive discussion, I'm moving this to the lounge

later, mikey.
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Old 06-14-2009, 08:33 AM
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Quote:
Originally Posted by poncho62
Bit of advise......Don't argue with an idiot....when you do, you become one too........
words of wisdom,ponch
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Old 06-14-2009, 08:44 AM
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I'm sure you guys know waymore about HP than I, but when I was a kid we found a steep hill,make our tune-up changes and run it up the hill with a stop watch,we try differnt carbs,all kinds of stuff it really helped dial a car in back then.but dynos were like some urban legend in the 70s and duel points were the sheet, us kids had to do something and do it cheap
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Old 06-14-2009, 08:45 AM
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This is the FACT that most can't handle. If you go to the drags for an afternoon you find out. You see, most opinions of this kind are held by guys who have never grabbed a time slip from a booth at the end of a drag strip.

The average driver is SOOOOOOOOOOOOOO inconsistent you wouldn't even measure something as small as these differences! PLUS, there are a ZILLION other factors that could effect if car A or B is faster!

The ONLY legitimate way to figure it out:

1. Test about fifty similar cars and average out the et's and MPH over about 20 passes each.

2. Using the same car run it 20 times then pull out the tranny and ac and install a 4 speed and run it 20 times under the same weather and track conditions.

It is LUDICROUS to think argue about such a small change. Hell, the average guy even after running his car many, MANY times at the drags is going to have a fluctuation of 2, 3 or even a half a second in each run! Just because of tire spin, light reaction, etc.

You would have to have an experienced bracket racer who runs within a few hundredth consistently to even perform the tests we are talking about such a small difference.

If the guy doesn't understand that, he isn't worth the argument.

I have a guy at work who has a STOCK 305 powered 67 Chevelle with a 3.00 rear. He thinks it would run 14s in the quarter. I have told him I will pay the gas to get there and the entry fee if he runs anything better than a very high 15 or even 16 second et (this track is a good three to four tenths slower than the one we had here in town).

He has never ran it, and doesn't have a clue. But that is where the argument ended. I just told him, go to the track and bring back proof you ran the 15. End of discussion.

Brian
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Old 06-14-2009, 09:22 AM
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Quote:
Originally Posted by powerrodsmike
If this is an ongoing debate between aquaintances about whose car is is faster, harder, better..you know.. , I'd offer to find a 1/4 mile track somewhere and see how it all comes out in the real world.

As this was not really a technical question, but still related to an automotive discussion, I'm moving this to the lounge

later, mikey.
Mikey, you are right on, Jsup take him and his car out somewhere and settle it. Go to the track and grudge match race . Cole
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Old 06-14-2009, 09:33 AM
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Quote:
Originally Posted by MARTINSR
the average guy even after running his car many, MANY times at the drags is going to have a fluctuation of 2, 3 or even a half a second in each run! Just because of tire spin, light reaction, etc.
Reaction time will lose you the race, it will not, however change your quarter mile ET.

I'll just say this- if my car is off by 1/2 a tenth, I'm wondering why. If it's a run right after arriving and the car's not cooled down as much as usual, or if it's real humid, that could account for it.

What I'm saying is, the guys I know, know what their cars run. If they're suddenly down a tenth- let alone a HALF SECOND- they're finding out what's wrong.

What you say is true of someone who doesn't come out to the track much, like twice a season or something.
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