Wide = Faster?
- Thread starter sicbeing
- 47 comments
- 2,683 views
Whoa. Lots of misinformation on this thread.
First off, all of your are wrong about the shifting before red line thing. You can't tell where the ideal shift point is by looking at the engine torque or horsepower curves by themselves.
It works like this. In virtually any engine, the torque drops off as it approaches its red line rpm. It is possible that the torque can fall off far enough that, in spite of the next higher gear's reduced torque multiplication, the next higher gear may put more torque down at the drive wheels than the lower gear does. Just because it moves the engine back to a beefier part of its torque curve.
This only happens in engines with high amounts of low end torque which are mated with close ratio gear boxes. (It wasn't uncommon in the old muscle cars)
It's the combination of the torque curve (not the horse power curve) _and_ the gear ratios that determines whether an early shift will be ideal.
Almost all cars... especially modern cars... aren't subject to this. They're better off shifting at the red line.
As for getting better results with wider gear in a drag race... there a number of reasons why this might happen.
1) In a short gear box, 1st gear may be too low. If 1st gear provides so much torque multiplication that the car will just spin its tires, then it's a waste. The driver (or the traction control) will have to feather the throttle and so can not use the full power of the engine. And then the first shift comes early because the gear is so short. A 1st gear which is juuuust long enough that the tires don't quite spin (after the initial hook) is ideal for the launch.
2) The shorter gear box may lose time by having to make more shifts. No power to the drive wheels during a shift. Pretty obvious. It's not uncommon for fewer shifts to be a better tradeoff.
3) Your shorter gear box may not have been finishing the drag race at max rpm. You'll be slower if you're only part way through the gear as you cross the finish line. You had to pay the price of a shift to get into that gear, so you really aught to get the full benefit of it. The worst case is when you have to shift just before crossing the finish line. Then you pay the full cost of a shift, but barely get any time to use the gear you shifted in to.
As you can see, the selection of 1st gear and the selection of the gear a drag car will cross the finish line in are the most critical. The inbetween gears are then simply chosen to... well... fall inbetween. You can play with the number of gears inbetween to find the most ideal. Engines with wide power bands tend to favor fewer, wider gears. While peaky engines generally want many shifts.
- Skant
First off, all of your are wrong about the shifting before red line thing. You can't tell where the ideal shift point is by looking at the engine torque or horsepower curves by themselves.
It works like this. In virtually any engine, the torque drops off as it approaches its red line rpm. It is possible that the torque can fall off far enough that, in spite of the next higher gear's reduced torque multiplication, the next higher gear may put more torque down at the drive wheels than the lower gear does. Just because it moves the engine back to a beefier part of its torque curve.
This only happens in engines with high amounts of low end torque which are mated with close ratio gear boxes. (It wasn't uncommon in the old muscle cars)
It's the combination of the torque curve (not the horse power curve) _and_ the gear ratios that determines whether an early shift will be ideal.
Almost all cars... especially modern cars... aren't subject to this. They're better off shifting at the red line.
As for getting better results with wider gear in a drag race... there a number of reasons why this might happen.
1) In a short gear box, 1st gear may be too low. If 1st gear provides so much torque multiplication that the car will just spin its tires, then it's a waste. The driver (or the traction control) will have to feather the throttle and so can not use the full power of the engine. And then the first shift comes early because the gear is so short. A 1st gear which is juuuust long enough that the tires don't quite spin (after the initial hook) is ideal for the launch.
2) The shorter gear box may lose time by having to make more shifts. No power to the drive wheels during a shift. Pretty obvious. It's not uncommon for fewer shifts to be a better tradeoff.
3) Your shorter gear box may not have been finishing the drag race at max rpm. You'll be slower if you're only part way through the gear as you cross the finish line. You had to pay the price of a shift to get into that gear, so you really aught to get the full benefit of it. The worst case is when you have to shift just before crossing the finish line. Then you pay the full cost of a shift, but barely get any time to use the gear you shifted in to.
As you can see, the selection of 1st gear and the selection of the gear a drag car will cross the finish line in are the most critical. The inbetween gears are then simply chosen to... well... fall inbetween. You can play with the number of gears inbetween to find the most ideal. Engines with wide power bands tend to favor fewer, wider gears. While peaky engines generally want many shifts.
- Skant
- 1,019
- Canada
- n00bxqb
Talk about hypocracy ...
Nice try, but physics owns you ...
You tune your gear ratios and shift points around the power curve ... I'd love to see you actually PROVE anything else is ideal ...
https://www.gtplanet.net/forum/showpost.php?p=1573114&postcount=9
Nice try, but physics owns you ...
You tune your gear ratios and shift points around the power curve ... I'd love to see you actually PROVE anything else is ideal ...
https://www.gtplanet.net/forum/showpost.php?p=1573114&postcount=9
Skant
I golded the license tests (the accelerate and brake ones on test track) over the weekend. My techniques for quickest times ranged from going past the redline - ie until no more acceleration on the under powered cars but changing before the redline on the Viper. I am no expert on the science all I know is that is what I did and I did this as a result of trial and error.
Therefore for each car auto was slower but for different reasons. On no car did I change at the same time as auto. Also on one of them (one of the short ones) I did not change up into third as the change itself slowed me down.
Therefore if you use trial and error on the test track (without even studying the graphs you will find a quicker method with the manual.
- 8
Just buy a huuuuuge wing. The BIGGEST wing you can buy. And get bling-blingin' rims. The gold-spoked BBS work best. Because all we all know, wings & rims add MAD HP, yo...
Oh, and the Honda civic is the fastest car ever. It'll beat anything, because it's fast & furious.
(for the record, I'm being sarcastic... please don't take that seriously... I just hate ricers)
Oh, and the Honda civic is the fastest car ever. It'll beat anything, because it's fast & furious.
(for the record, I'm being sarcastic... please don't take that seriously... I just hate ricers)
- 895
- GTP_Renesis
GenkiSpeed
👍 great post hehe.
Okay physics is a field of mine, but in terms of gear changes, the number of variables at hand is large, and so trying to balance them all out to get a decent shift time can be a bit of an art. As someone quite rightly said, you need first gear long enough to allow full power without getting wheelspin, but not so long that the car is sluggish off the line. Some engines wont allow you to do this, so you compromise and shorten the gear - better to be quick off the line than trying to use the whole power curve I think.
Shifting = time spent with engine NOT driving the wheels, hence slower. I could mention Zeroshift, but thats not in GT4 so not much point. However, shifting is unavoidable. I find its best to do a few test runs - if the engine seems to gain acceleration at peak rpm, hold on to the rev limit. If it drops off - be sure to shift up before it happens. As someone else said - you want to gear the car so it reaches its peak acceleration in the gear it crosses the line with. Shifting up at the last moment always kills your time - I had this in GT4 with IA-1 (i think). just space the gears inbetween to maximise the gap inbetween.
I think true drag cars have 2 gears - one to get off the line, one to accelerate like crazy down the straight. Its not like they'll reach the limit of the engine in 400m. (At Santa Pod, NHRA cars have to brake BEFORE the 400m line, otherwise they cant stop in time and crash into something).
Anyway I am no expert... besides, I intend to spend time driving like a European - around corners...
- 895
- GTP_Renesis
GenkiSpeed
Sorry for a second post - but I want to do my Essex Boy-Racer edit of your text...
"Nah need a HUUGE wing on da back innit yea! Den get sum MASSIV' rims, 20inches like, n dat wicked body kit - dat one on the Escort, yea, page after Jordan in Max Power innit. wood look wicked on me Nova. Den when I is racin', like, with me tunes poundin', all the fit birds will be staring at me, and I'll 'av all da respec' yea, an i'll beat everyone off the lights innit yea. Dat is kool dat is... eh - what you lookin' at? You disrepectin' me? AII?"
*loads shotgun* absolutely HATE them. Stay off the roads.
- 35
Jmac279
I have seen mention of this link three times in this thread, and even read it twice - and am happy to say that it was fantastic education for me and cleared up a lot of my confusion about proper tuning and driving.
Too bad the conversation continues to go on without mention of your effort Jmac.
- 8
Damn, Jmac... read the FAQ, and I'm damn speechless. props!
I don't know about that... See the problem with Orange County, California is that since we're such a big racial melting pot and yet people are so stupid and trend-prone, we end up with different kinds of ricers.
AzN BoYz (asian gangster-wannabes with rich parents): "What up duu, check my ride duu. Iss got VTEC duu. I race you, smoke dat Nissan, duu. Mah VTEC' fast, duu"
Wiggers (white guys trying to be black): "Yo what up biyatch, my Civic's hella-tight yo, check out dem 20's! BOO-ya! I gots the bling-bling, homie! Check this phat exhaust, my ride be slammin' low!"
Cholos (mexican gangsters who rice out their '87 accords): "Orale, ese'... Whatchuu starin' at, homes! Don't be checkin' my ride unless you wanna blast, fool! My ****'s got VTEC, ese, these 20's'll smoke you!"
Jmac279British ricers sound even worse than North American ricers ...
I don't know about that... See the problem with Orange County, California is that since we're such a big racial melting pot and yet people are so stupid and trend-prone, we end up with different kinds of ricers.
AzN BoYz (asian gangster-wannabes with rich parents): "What up duu, check my ride duu. Iss got VTEC duu. I race you, smoke dat Nissan, duu. Mah VTEC' fast, duu"
Wiggers (white guys trying to be black): "Yo what up biyatch, my Civic's hella-tight yo, check out dem 20's! BOO-ya! I gots the bling-bling, homie! Check this phat exhaust, my ride be slammin' low!"
Cholos (mexican gangsters who rice out their '87 accords): "Orale, ese'... Whatchuu starin' at, homes! Don't be checkin' my ride unless you wanna blast, fool! My ****'s got VTEC, ese, these 20's'll smoke you!"
Jmac279
Okay, little boy. I have a real championship trophy in my living room and several plaques on my wall. What have you got? Only a few days ago, I was making 130mph dives down into hairpins in RL against exotic european supercars. I'm guessing you were sitting on your couch in front of the TV.
Okay. I'm through being rude right back at you if you're through being rude to me.
The thing is... the post your link is refering to is not wrong. In fact, it's quite a good write up. But it's only looking at a single aspect of the equation. You're ignoring factors like limits of traction and time required to shift. Indeed, your post doesn't address the needs of launching from a standing start at all. And we're talking about drag racing on this thread, last I checked.
In fact, according to what you're saying... the guy who started this thread should never have seen a faster ET with wider gearing since wider gearing would _always_ lead to lower average power. I pointed out the factors that can lead to that result, and you flamed me over it and told me I didn't know what I was talking about.
The points I listed in my post are conventional wisdom from RL drag racing. It's not like I just made it up myself. This stuff is well known.
And, frankly, I can indeed prove that I have some oodling of what I'm talking about because you don't get trophies when you're wrong.
So try to calm down, k?
- Skant
- 1,019
- Canada
- n00bxqb
1) I'm not a little boy.
2) Sorry for being rude, I was probably grumpy or in a bad mood or something.
3) I posted that link as a possible explanation of why wider might be faster. I don't know his power curve. If it has a wide powerband, wider gears could save time because, like you said, shifting takes time ...
4) I would race IRL, but I don't think my 102 hp car would compete well nor do we even have a track within an hour's drive
2) Sorry for being rude, I was probably grumpy or in a bad mood or something.
3) I posted that link as a possible explanation of why wider might be faster. I don't know his power curve. If it has a wide powerband, wider gears could save time because, like you said, shifting takes time ...
4) I would race IRL, but I don't think my 102 hp car would compete well nor do we even have a track within an hour's drive
Admittedly, I wasn't in a very good mood even before I read your post, and I went off, too. So I will also apologize.
👍 Racing in RL may be a lot more accessable than you think. Watching racing on TV leaves you with the impression that nobody short of rich boys or super talented pros can participate. But, in reality, racing spans all the way down to where a normal joe with a regular 102hp grocery getter can go out and compete. It's just that only the big time stuff is televised.
Heck, I've watched an old grandma in her minivan who still had a load of groceries in the back staging on the drag strip. And not only that, but she was kicking butt because it's bracket racing! (The car in the other lane was not released until she was already half way down the track)
My point is... you don't have to be rich and famous or anything. Look up autocrossing and/or drag racing in your area. They do have race classes that you and your car fit into. And they only cost like $20-40 per event. The only thing you need besides your normal car is a helmet and sun screen.
(And actually, for a 102hp car, the drags won't even require a helmet. But autocross will)Clearly, you have a good understanding of car physics. And I'm sure you're a good driver already. So you really aught to go out and try it for real.
The small time events happen all over the place and quite often... not just at permanent tracks. Autocrosses, for instance, are usually temporary courses set up on (very) large parking lots or air ports. Heck, one of the events I ran at was actually on a large peer (and one of the cars biffed it so badly that he nearly went over the edge and into the ocean!).I'm sure you can find events within a reasonable driving range. You just gotta look into it. There's a lot of RL racing resources on the web.
- Skant
- 8
d
