gearbox questions

[TeflonTom]

can everybody do me a favour post up info about what rpm the engine is doing vs road speed please

so.. for example in 1st gear 1000rpm = 15mph or whatever it is.. and what type of felicia you have..

i'm thinking about swapping the gearbox on my pickup for a 1.6 petrol one or diesel one, so i'm just trying to figure out which will be best for my setup..

i reckon by my calculations with a diesel box in 5th gear 70mph is roughly 2550rpm

at the moment i've got a 1300mpi box in there, and the 1st and 2nd gears are far too short for the amount of power i've got, and in 5th gear 70mph is above 3000rpm which gets really tiresome on a long journey becuase the engine is quite throaty

i know that jimbo and darren will probably have something to say on this subject

Edited 22 August, 2010 by TeflonTom

[VRS-Badman]

wack a vrs fab box on if u can gets 70 @ 2000rpm in 6th gear :yes: and has the short 1st and 2nd gears to which would aid your motor for picking up speed

[TeflonTom]

ha.. it's already quicker than a fabia vrs :yes:

there's lots of reasons why a fabia vrs box wont fit it, bellhouse is a different shape, hydraulic clutch mechanism, gear linkage, driveshafts, space.. etc etc etc

[rolo]

Best (highest) was 2900 at 70 (correct by gps, the speedo was nearly 10mph out) using 205/50/17s on the diesel box (and coilovers!). Started detuning now so there`s 205 /40/17 on. Got similar on195/65/15 using favorit struts for clearance. Will make a list with 40`s on if it`ll help. 100mph at just over 4 on a rolling road. I wish on the gearbox for clutch reasons-paddle lasted 2 days, time for kevlar plate, uprated springs and power down to around 90.

Edited 23 August, 2010 by rolo

[Ravenskull]

Have tacked the various ratios/toothing of all 7 possible standard gearbox combos to the PM thread.

Edited 23 August, 2010 by Ravenskull

[TeflonTom]

thanks guys, looks like i'm on the lookout for a diesel gearbox then

[VWD]

thanks guys, looks like i'm on the lookout for a diesel gearbox then

If a 1.4TDi(Fabia) box will fit , I'll get some data, though suspect it'll be short on 1st/2nd .Certainly is on the 1.4 .

Edited 29 August, 2010 by VWD

[Ravenskull]

If a 1.4TDi(Fabia) box will fit , I'll get some data, though suspect it'll be short on 1st/2nd .Certainly is on the 1.4 .

The thought occurs that the info i gave tom might be of some use to others also, so i'll bump my post count up a notch and post it here too

This info is taken from Binder 2 of Skoda's official service manual for the felly. (I only have binder 2 though, so far...)

Unfortunately, as the forum wipes out any attempt at carefully formatting the data, please use the following to translate:

G'box specs should read:

Gear number, number of teeth (Driving:Driven), Transmission ratio

Therefore:

X, YY:YY, Z.ZZZ

Gearbox data as follows:

Although only 3 models of gearbox are quoted in haynes, binder 2 tells me there are in fact 7 possible Gearbox/engine set-ups:

Gearbox 10S Mated with Final drive 4.118 (4.167) & Engine 135/135B/136B/136M

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 43:13 3.308

2 44:23 1.913

3 38:30 1.267

4 38:41 0.927

5 33:46 0.717

Final 75:18 4.167

Drive 70:17 4.118

Rev 38:13 2.923

Gearbox 10S Mated with Final drive 3.833 & Engine 135M

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 43:13 3.308

2 44:23 1.913

3 38:30 1.267

4 38:41 0.927

5 33:46 0.717

Final

Drive 69:18 3.833

Rev 38:13 2.923

Gearbox 14S Mated with Final drive 3.579 (3.350) & Engine AEF

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 43:13 3.308

2 44:23 1.913

3 38:30 1.267

4 38:41 0.927

5 33:46 0.717

Final 67:20 3.350

Drive 68:19 3.579

Rev 38:13 2.923

Gearbox 14S Mated with Final drive 3.833 & Engine AEE

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 43:13 3.308

2 44:23 1.913

3 38:30 1.267

4 39:40 0.975

5 35:44 0.795

Final

Drive 69:18 3.833

Rev 38:13 2.923

Gearbox 14SK Mated with Final drive 3.833 & Engine AEE/135M

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 45:13 3.462

2 45:23 1.957

3 38:29 1.310

4 39:40 0.975

5 34:45 0.756

Final

Drive 69:18 3.833

Rev 38:13 2.923

Gearbox 14SK Mated with Final drive 4.118 & Engine 136M

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 45:13 3.462

2 45:23 1.957

3 38:29 1.310

4 39:40 0.975

5 34:45 0.756

Final

Drive 70:17 4.118

Rev 38:13 2.923

Gearbox 14SK Mated with Final drive 3.579 & Engine AEF

Gear No.of Teeth Transmission

No. Driving:Driven Ratio

1 45:13 3.462

2 45:23 1.957

3 38:29 1.310

4 39:40 0.975

5 34:45 0.756

Final

Drive 68:19 3.579

Rev 38:13 2.923

---------------------

3 kinds of 5th gear synchroniser body:

002-311-310A (diameter 9.85 - 10.1mm)

002-311-310B (diameter 10.2 - 10.45mm)

002-311-310 (diameter 10.55 - 10.8mm)

---------------------

Locking pieces of 3rd/4th gear Synchromesh clutch:

G'Box 10S;

-Pre sept 96 - shaft dia 3.4mm

-Post sept 96 - shaft dia 8.0mm

G'Box 14S & 14SK

- shaft dia 8.0mm

-------------------

Locking pieces of 3rd/4th gear Sliding sleeve:

G'Box 10S;

-Pre sept 96 - gap size 4.0mm

-Post sept 96 - gap size 8.0mm

G'Box 14S & 14SK

- gap size 8.0mm

---------------------

Locking pieces of 1st/2nd gear:

G'Box 10S;

- shaft dia 3.4mm

G'Box 14S & 14SK

- shaft dia 7.2mm

-------------------

Ok, i'm done spamming the forum for the day now :p

Dan

[Mariosti]

Apologies for digging up an old thread, but I have a pressing question.

 

1. How can you distinguish between the 14S and 14SK gearboxes?

(I'm guessing that 14SK were used after the facelift, although most likely pre-lift cars from 97-98 might have the 14SK also, so is there a way to identify one from the other looking at just the gearbox?).

2. What kind of felicias had the 14S gearbox with 3.350 final drive?

(And as in the previous question is there a way to distinguish them).

 

The 3.350 14S would have a very nice 5th gear for cruising 60-70mph.

[RicardoM]

[Papez]

On 22/03/2019 at 13:42, Mariosti said:

2. What kind of felicias had the 14S gearbox with 3.350 final drive?

 

It was 1.9 gearbox. You can use 14sk to. It has 3,579 FDR, but it has longer 5th gear, so overall ratio is 2.66 (vs 2.7 of 14s)

 

It can be identified by gearbox number. Last number is FDR, "1" means 3.350/3.579

 

Difference between S and SK type gearbox is 5th gear cover (see in riccardo's picture) and oil drain plug - "S" uses 19mm hex head screw, while "SK" uses 17mm allen.

Edited 23 March, 2019 by Papez

[KenONeill]

Isn't the 1.9l gearbox designed for a diesel engine? Will the 1.3l petrol actually have enough torque to pull top gear?

[Mariosti]

@KenONeill

50kW 1.3 mpi has like 10% more torque across the rpm than the 40kW 1.3 spi engine, and yet, the 50kW engine has 4.118 final drive and the weaker 40kW engine has 3.833 final drive.

As i mentioned in another topic, factory gear rations aim at getting near the theoretical top speed in fifth gear, not real world economy at constant speed of 90-140km/h. The fuel consumption testing cycles also didn't really test this, which is why the factory gearbox has in fact not the best gears configuration for a  specific car and engine.

Of course the 1.3 mpi will not have the same acceleration in a diesel gearbox fifth gear, it will most likely have a significantly lower top speed then. But at the same time, with the longest gearbox, the 4th gear will be a tiny bit shorted than the 5th gear in 1.3 mpi box, which means that it will have better performance in 4th, and most likely a bit better top speed in 4th, while at the same time long 5th gear would work more as an "overdrive" for high speed cruising.

This is important for two reasons - one is engine noise, 1.3mpi is far more noisy doing 3-4k rpm than 2-3 k rpm. second - this type of engine has the best efficiency at around 50-75% engine load at 2-3,5k rpm.

Engine load depends on the car's speed, and on the potential maximum power of the engine at specific rpm.

 

This whole idea comes from understanding actual numbers.

For example, a felicia at 62mph (~100km/h) will require around 10kW of power from the engine to just cruise around on a flat road.

With the stock 1.3 mpi 4.118 fd gearbox in 5th gear you get around 2950rpm (lets say 3k rpm), and the engine at full throttle at 3k rpm actually can produce over 30kW (stock engine).

This means that cruising with the stock 1.3 mpi engine and stock 4.118 fd gearbox you get less than 33% engine load. In this situation the engine has very poor efficiency (even two times worse than in the sweet spot rpm/load area). 

With the longest diesel gearbox you should be doing around 2200rpm at the same 62mph(~100km/h) in 5th gear. At this rpm the stock 1.3 mpi engine produces a peak of ~21kW of power , which means that the engine will have around 50% engine load, (and similar/more engine load at 100-140km/h) this means that the engine will run at it's maximum break specific fuel consumption, meaning it will use the least amount of fuel to produce a given amount of hp. And as we wan't to cruise at the same speed, we need the same amount of hp, and that's why I expect a significant fuel consumption reduction with this gearbox swap.

 

(this answers the question, that yes, the engine has more than enough power/torque to accelerate even in 5th gear with a diesel gearbox, although the power surplus will be halved compared to the short box, which is why it will be two times worse at accelerating from that speed/rpm. The thing is you don't often accelerate in 5th anyway, so this doesn't really change anything, as you still have to do a gear reduction to get a reasonable acceleration, but you'll just have to go to 3rd instead of 4th)

 

@Papez

From what @RicardoM mentioned in another topic,

the 14s 1.9d gearboxes have these gear ratios: 3.398, 1.913, 1.267, 0.927, 0.717 and final drive of 3.35 or 3.579.

At the same time 14sk 1.9d gearboxes have these: 3.462, 1.957, 1.310, 0.975, 0.756 and final drive of 3.579.

 

To get the actual engine to wheels rpm ratio you have to multiply the gear ratio by the final drive.

This means that comparing 5th gears, in 1.3 mpi 14sk 5th gear is 0.756 and fd 4.118 gives actual ratio of 3.113 engine rotations per each wheel rotation.

For this example I'll use 185/60 r14 tyres that i use, they have 577.6mm diameter (2,8% more than stock 165/70 r13), and circumference of 1.814 meter.

Therefore when i cruise at 62mph my wheels have to rotate at ~918.8 rpm.

So in 5th gear at 62mph (~100km/h) you'll get this many engine rpm:

 

1.9d 14s 0.717 fd 3.35 -> ratio 2.402  -> rpm 2223

1.9d 14s 0.717 fd 3.579 -> ratio 2.566  -> rpm 2357

1.9d 14sk 0.756 fd 3.579 -> ratio 2.706  -> rpm 2486

1.3mpi 14sk 0.756 fd 4.118 -> ratio 3.113  -> rpm 2860

 

It kind of lines up, although i'd guess that the 1.3 mpi should calculate a bit closer to 3000rpm, although I'm not sure how precise the tachometer is. i mean the signal from injectors is 100% precise as it exactly represents the amount of engine cycles and that's exactly half of engine rpm. I'm just not sure about the scale precision, as indicated i get 3k rpm at about 102km/h  measure by gps, which would give us about 2941 rpm at 100km/h, but that's just 80 rpm off the calculation, so it's possible that it's just the measurement errors. 

 

So to sum up. If I'm mistaken then please tell.

@RicardoM Thanks for the comparison drawings, great info!

 

One last question still holds. What pre lift 1.9 diesel felicias had the 3.335 final drive and which had the 3.579 final drive?

I'm currently looking to buy one, and have a shop ready to rebuild it to ensure it's reliable, and would really like to get the longest gearbox possible, to bump up the engine cruise efficiency to the theoretical maximum and actually just drive it around, and collect fuel economy data, and compare it to current gearbox data.

[faker]

Ok. I got a little lost with all the numbers. Am I right in thinking the 1.3 mpi felicia estate and 1.3 pickup has the highest crownwheel and pinion gear? As in the opposite to the diesel box?

[aggel]

On 29/03/2019 at 16:58, Mariosti said:

Therefore when i cruise at 62mph my wheels have to rotate at ~918.8 rpm.

So in 5th gear at 62mph (~100km/h) you'll get this many engine rpm:

 

1.9d 14s 0.717 fd 3.35 -> ratio 2.402  -> rpm 2223

1.9d 14s 0.717 fd 3.579 -> ratio 2.566  -> rpm 2357

1.9d 14sk 0.756 fd 3.579 -> ratio 2.706  -> rpm 2486

1.3mpi 14sk 0.756 fd 4.118 -> ratio 3.113  -> rpm 2860

 This conditions are identically for highway driving cycle..

 

We must also check other driving cycle.

What i mean is that first of all we have to check the torque that is on the wheel with those rpm and the specific ration.

  Unfortunatelly i dont have the power and torque chart of the engine to make the calculations.

 

My point is that if for some reason you want a rapid accelaration or you have to brake and then accelarate, it is sure that you will have to shift down, and then to shift up.

This driving is very unconfortable for roads out of the city with curves, where your driving isn't with a stable velocity.

Edited 31 March, 2019 by aggel

[RicardoM]

11 hours ago, aggel said:

  Unfortunatelly i dont have the power and torque chart of the engine to make the calculations.

These are the charts for 1.6 and 1.9 engines. Please somebody upload the chart for 1.3 MPI.

 

[RicardoM]

[Papez]

My bad, I looked on 14S 1.6 gear ratios and failed to notice that 14S diesel has different 4th and 5th gear ratios.

 

I looked into service manual - and nothing. There's no data about how distiguish short and long gearbox. Identification number is same for both variants. My guess is, that shorter gearbox was meant for cargo variants (pickup, vanplus and praktik), while longer for passenger. 

 

Anyway, if my math is correct, you'll get ~90kph at 2250RPM even with short gearbox, on standard wheels. I'm not sure, if 1.3 has enough power for long variant, i often have to downshift in slopes, once my rpm drops under 2500 - i have 4,167 10S. I think, that 2500RPM at cruising is ideal for this engine. (Edit: from ricardo's graphs, it's also point where 1.3 reaches ~25kW, which is same as diesel at 2000RPM) And personally, I think that 10S is best 1.3 gearbox, with ballance between fuel consumption and dynamics. Unless you drive on higways.

 

Btw, what is your target? Lower fuel consumption or noise reduction?

Edited 1 April, 2019 by Papez

[Mariosti]

Hi,

 

Here's a chart that I've calculated off gear ratios and off 1,3 mpi 50kW power/torque curve.

The light green graphs show engine power in kW at specific speed in all gears. Light blue shows what i calculated for the super long 3.335 diesel gearbox.

The dark red line is the calculated theoretical drag based on car's cx, frontal area, weight and rolling resistance.

The power is a bit high as i based it on a low resolution image of the engine power/torque curve, so it should be about 2-3kW lower across the chart.

Usually engine manufacturers state engine specs at the crank, while you need power at the wheels to push through the combined resistance forces, which is why these would get even lower, although it would require some more calculations to do, as the transmission resistance depends on rpm and on power transmitted. When you take all of that into consideration the chart is spot on compared to real world.

 

@Papez

I'm after both fuel economy bump and noise reduction. I mostly use my car for ~300km routes. I don't have the heart to use it in the city on short routes where it's can't even heat up.

 

One more thing. Once I've talked about engine power at specific rpm, there's no need to talk about torque.

Torque times rpm gives power, and it's in fact power at the wheels that gives you both acceleration and top speed.

The difference between full throttle power at specific rpm and actual combined resistance is the engine load ratio(while cruising at that speed in that gear).

So basically I'd like to suggest to not talk about torque at all as it's totally unnecessary. The only thing that really matters is the power curve of the engine.

Torque figure is useful basically only to the engine/transmission engineers, as their designed strength must cope with maximum torque. Besides that it's a useless information.

 

As to the gear reductions etc. I still have to do them now, so it makes no difference really if i have to change to 3rd instead of 4th on a steep climb.

 

Edited 3 April, 2019 by Mariosti

[aggel]

5 hours ago, Mariosti said:

One more thing. Once I've talked about engine power at specific rpm, there's no need to talk about torque.

Torque times rpm gives power, and it's in fact power at the wheels that gives you both acceleration and top speed.

 

This is correct  mathematically but for gears reduction as the gearbox.When you decreases the rpm from one ration, you increase the torque, but the power output stays the same. Also if this was true about engine power and engine torque, the two graphs ( power and torque), should have been similar. 

   So  engine power and engine torque are two differents things.

 

Another comment that i want to add is that looking at yours graph i saw is that you shifting up at 5000rpm, where the power peaks.As far as i remember from my studies ( 10 years ago) you should  shifting when you reach top torque for better accelaration consumption etc, means at 3500rpm.

 

 

Any comment is accetable.

 

 

 

 

 

[faker]

I just want to know where or on what model I'd find the biggest crownwheel...

[Mariosti]

1 hour ago, faker said:

I just want to know where or on what model I'd find the biggest crownwheel...

The biggest one should be on 14sk with final drive 4.118 as it has the most teeth. That's the 1997 and later 1.3mpi 50kW gearbox as far as I know

[faker]

Thanks Mariosti. 

[Papez]

On 03/04/2019 at 22:23, faker said:

I just want to know where or on what model I'd find the biggest crownwheel...

 

Not sure, if it'll fit Felicia box, but Lupo/Arosa/Fabia 1.0/OHV had 73:15/4,867. 002 gearbox used in these cars is evolution of 14SK gearbox, so it might be interchangeable.

 

@Mariosti This power/resistance graph is great, thanks. I think you can get rough estimation of drivetrain resistance by scaling resistance curve in way that it intersects with power curve at top speed mark.

Looks like that 1.3MPi will have enough power to pull this "6th gear"

[Mariosti]

On 03/04/2019 at 19:55, aggel said:

 

This is correct  mathematically but for gears reduction as the gearbox.When you decreases the rpm from one ration, you increase the torque, but the power output stays the same. Also if this was true about engine power and engine torque, the two graphs ( power and torque), should have been similar. 

   So  engine power and engine torque are two differents things.

 

Another comment that i want to add is that looking at yours graph i saw is that you shifting up at 5000rpm, where the power peaks.As far as i remember from my studies ( 10 years ago) you should  shifting when you reach top torque for better accelaration consumption etc, means at 3500rpm.

 

 

Any comment is accetable.

 

Actually power won't stay the same.

 

Take the felicia as an example.

1st gear.

a. super long diesel gearbox in first gear you have a gear ratio of 3.350 (final drive) x 3.308 (1st gear) = 11.08 (gear ratio between engine and the wheels).

b, short 1.3 mpi gearbox in in first gear you have a gear ratio of 4.118(final drive) x 3.462(1st gear) = 14.25 (gear ratio between engine and the wheels).

 

At 20km/h we'll have:

a. ~2036 engine rpm, giving around 20kW of power and around 90Nm at the engine. (looking at the above graphs)

b. ~2619 engine rpm, giving around 26kW of power and around 95Nm at the engine. (looking at the above graphs)

The wheels will have 20km/h = 333,33m/minute 185/60 r14 wheel circumference is 1,814 m, that gives us 183,8 rpm at the wheels at 20km/h

 

That gives us at the wheels:

a. 90Nm * 11.08 ~= 1000Nm at the wheels,    at the same time (1000 Nm*183.8 rpm)/9550 = 19.2 kW

b. 95Nm * 14.25 ~= 1350Nm at the wheels,    at the same time (1350Nm*183.8 rpm)/9550 = 25,98 kW

 

Therefore as you can see torque times rpm is just power, which is why if via gear reduction you have more torque at given car speed than your engine will have more rpm and must produce proportionally more power at the same time, because torque doesn't come from nothing.

 

If the engine didn't produce more power at the higher rpm, than even with gear reduction you wouldn't gain any torque at the wheels.

 

 

Edited 5 April, 2019 by Mariosti