Dunno if it's been posted on these forums before, found it while looking up some info about shift points and gearings

http://www.datsuns.com/Tech/whentoshift.htm

Quote from kurent :

I always wondered this. On BL1 with the XRT you drive the last corner uphill and just before the end of the climbing the magical shift light© comes on. Should you shift and cut the power for a short time when climbing uphill which I guess is a bad idea, or wait until the top and then shift?

That's a good question, but I guess in racing it doesn't make any difference. In hotlapping?

But in general, it's important that common sense has a bigger weight than the shift light. Stubbornly changing gear everytime the light comes on, is surely not the fastest way around a track, atleast for the more curvy tracks. It wouldn't make sense to shift to 4th if you have to shift back to 3rd half a second later

Quote from kurent :

I always wondered this. On BL1 with the XRT you drive the last corner uphill and just before the end of the climbing the magical shift light© comes on. Should you shift and cut the power for a short time when climbing uphill which I guess is a bad idea, or wait until the top and then shift?

hehe, i had that problem alot when i drove XFG at BL.
i always tried (still do) to shift when i cleared the "hill" or when i drive downhill.
seems to be the best way

Quote from AndroidXP :

That's a good question, but I guess in racing it doesn't make any difference. In hotlapping?

But in general, it's important that common sense has a bigger weight than the shift light. Stubbornly changing gear everytime the light comes on, is surely not the fastest way around a track, atleast for the more curvy tracks. It wouldn't make sense to shift to 4th if you have to shift back to 3rd half a second later

Very true! A good real life example of this is autocross. The courses we run on are designed to be run by most cars in 2nd gear the whole way. Quite often however I will be on a course where I hit the limiter in 2nd on maybe two or three spots on the course. I will ask other Miata drivers if they shift to third and some say they try it, but in almost all cases (even if you're hitting the limiter for say 3 or 4 seconds on a quick stretch of the course) we've found it to be better to stay in 2nd.

I don't think it's as crucial in LFS compared to real life because you're not dealing with clutch and shifter and one hand on the wheel while dealing with g-forces at the same time. There would be times in real life when I'd stay in second in autocross when I'd change to third in LFS just because it's only the click of a button and no chance of human error. So I guess we should all use a clutch and shifter Even then though, it's easier to juggle all that stuff when not being subjected to g-forces...

Well of course that's an easy one, you're not gonna shift if the light comes on for example right before a corner. Shift up, shift down, take the corner.

I always try to set my gear ratios for a specific track which is very important. Some people have is set so they have to change gears in the most weird parts of the track.

But ok what about this one:
The wheels that are connected to the drive train just happen to be in the air at the speed that is optimum for a gear shift. Do you:
A: step on the gas, rev the engine, the wheels have no resistance in the air so they spin wildly. When they land you should get a little boost right?. The engine goes into the "red" revs but you immediately shift.
B: You shift while in the air, but you're not a bird so the wheels are not spinning as fast when you land because of little air time. Not a big boost but you're already done away with shifting.

Oh what we will all do for that final 0,01 second.

Haha, it's funny you say that because I used to set my gearing in Grand Prix Legends so that I'd shift gear while airborne in one or two spots!

Quote from BigDave :

i wanna know wot is a good time to change gear at wit the XRT for best performance. I normaly rev to about 7,500 and sometimes the full 9,000.

The red light indicates when it is the best time to shift up. Maybe if you're going up hill you may need to hold the gear fractionally longer.

How has there been 31 posts to say "shift when the light comes on"? lol

Quote from sexynipps :

almost redline

Say, wanna do a drag race?

In real life my car has no rev guage or light. so I guess I change at about 7000 (could be 8000)
It's very hard finding specs for my car.

Quote from Stew2000 :

In real life my car has no rev guage or light. so I guess I change at about 7000 (could be 8000)
It's very hard finding specs for my car.

I doubt very much your road car revs to 8000. What is it.

Most standard road cars rev to between 6,800 and 7,200

Quote from Gentlefoot :

I doubt very much your road car revs to 8000. What is it.

Most standard road cars rev to between 6,800 and 7,200

Those rotary engines rv high don't they, in the Mazda's

Quote from CSU1 :

Those rotary engines rv high don't they, in the Mazda's

very true - the RX8 revs to 9000 rpm - as does the Honda S2000 believe it or not.

But they are the exceptions to the rule.

My Golf will rev to 9000 too but it has a competition engine with stronger rods etc.

But then my GSX600R revs to 14000! wheyhey I love revs!

I dont have a Mazda so it is probably around 6 to 7000.
It's a 97' Daihatsu Charade 1.3 LXi. 4 Cylinder, EFI. Purrs at 30mph and Growls at 70mph
Top Speed = 105mph (that's what I can get it to)

Quote from Stew2000 :

I dont have a Mazda so it is probably around 6 to 7000.
It's a 97' Daihatsu Charade 1.3 LXi. 4 Cylinder, EFI. Purrs at 30mph and Growls at 70mph
Top Speed = 105mph (that's what I can get it to)

My guess it that that'll be a right revvy little engine - probably around the 7000 mark.

Atm my mate in work is looking into an engine change from 1.6 v-tech Fiesta to a 1.8 v-tech focus engine race spec everything done brand new still got the paint on it €2000(287bhp and revs 8000+ very loud.It's not looking good though as the engine mounts seem off slightly, but the gear box is the same.We work in automotive distribution and have some contacts in England whom specialize in ford changes can't remember their name he knows em', but they said it wasn't worth the hastle as to much work had to be done probably a weeks work and €1500 labour

Quote from CSU1 :

Atm my mate in work is looking into an engine change from 1.6 v-tech Fiesta to a 1.8 v-tech focus engine race spec everything done brand new still got the paint on it €2000(287bhp and revs 8000+ very loud.It's not looking good though as the engine mounts seem off slightly, but the gear box is the same.We work in automotive distribution and have some contacts in England whom specialize in ford changes can't remember their name he knows em', but they said it wasn't worth the hastle as to much work had to be done probably a weeks work and €1500 labour

2000EUR is damn cheap for a competition engine. Mine was nearer to £5k but that was fitted.

Moving engine mounts is not a simple job but I reckon 3500EUR for a 287bhp beast in a Fiesta is well worth the money. But that's just me I guess

I've gotta say though - 287bhp from a 1.8 sounds like rather a lot to me. I'm assuming normal aspiration. That would have to be running some ridiculous compression ratio to achieve that. In addition extremely high lift, long duration cams. Would make the car very hard to drive in traffic on the road.

Quote from Gentlefoot :

2000EUR is damn cheap for a competition engine. Mine was nearer to £5k but that was fitted.

Moving engine mounts is not a simple job but I reckon 3500EUR for a 287bhp beast in a Fiesta is well worth the money. But that's just me I guess

I've gotta say though - 287bhp from a 1.8 sounds like rather a lot to me. I'm assuming normal aspiration. That would have to be running some ridiculous compression ratio to achieve that. In addition extremely high lift, long duration cams. Would make the car very hard to drive in traffic on the road.

A friend of ours races in mondello for a hobby, dont know exactley what is done to the engine apart from they gave a port polish, changed the head,cams,rods, gasket and gave it a remap.I seen the very engine on a web site yest for £5.5k so is a good price, he is just worried he will ruin his car in the process, I think maybe the best solution is to buy a seconf hand bog standard focus and go that way

Quote from CSU1 :

A friend of ours races in mondello for a hobby, dont know exactley what is done to the engine apart from they gave a port polish, changed the head,cams,rods, gasket and gave it a remap.I seen the very engine on a web site yest for £5.5k so is a good price, he is just worried he will ruin his car in the process, I think maybe the best solution is to buy a seconf hand bog standard focus and go that way

I agree. get a cheap Focus.
Then again I hate the Focus
Get a Charade like mine

Quote from CSU1 :

A friend of ours races in mondello for a hobby, dont know exactley what is done to the engine apart from they gave a port polish, changed the head,cams,rods, gasket and gave it a remap.I seen the very engine on a web site yest for £5.5k so is a good price, he is just worried he will ruin his car in the process, I think maybe the best solution is to buy a seconf hand bog standard focus and go that way

Sounds a lot easier. Althought the extra weight is a big shame. And yes, trust me from the point of view of road use, the car will be ruined. If for no other reason than fuel consumption. Ofcourse if fairly mild cams are used then the car could drive pretty normally.

So only one proper response to the original post, the when to shift link?

Normally, you change gears when the rear wheel torque in the next higher gear is equal to the rear wheel torque in the current gear. If the rpm drop is great, like from 1st to 2nd gear, when you shift at redline, the next higher gear's torque will be less, but you can spin the engine any faster. For most cars, this is usually close to redline, at least in lower gears, but assuming the shift indicator is correct in LFS, the shift points are significantly lower for some of the cars, indicating relatively low torque and power peaks.