Revs vs speed

[Steps65]

Hello everyone,

I have Skoda Octavia style 4x4, 2L diesel, 6 gears manual gearbox, engine code CRMB, the revs of my car is 2300 rpm on the 6th gear at 120 km/h (90m/h) is this normal, because my previous car wasn't like that it was 2000 rpm at the same speed.

just want to know is it normal or do I have to do something about it because the car still under warranty until May.

Thanks for help.

[shyVRS245]

120kph is actually more like 75mph and as your car is a diesel seems reasonable to expect those sort of revs at 75mph. Remember my last 6 speed manual Octavia diesel was geared so that 2,000 revs was 70mph but it was a front wheel drive 2013 SE with the 150PS engine. My current 7 speed DSG Superb also does 70mph at 2,000 rpm in 7th gear.

[Steps65]

2 hours ago, shyVRS245 said:

120kph is actually more like 75mph and as your car is a diesel seems reasonable to expect those sort of revs at 75mph. Remember my last 6 speed manual Octavia diesel was geared so that 2,000 revs was 70mph but it was a front wheel drive 2013 SE with the 150PS engine. My current 7 speed DSG Superb also does 70mph at 2,000 rpm in 7th gear.

Thanks

[logiclee]

MPH/1000rpm differs for each model and on year.

 

We once run two Passats only a year apart 2.0TDi and there was massive difference in gearing.  The 4x4 may have different gearing to the FWD.

 

Our three current cars are very different motorway cruisers.

 

At 70mph.

 

Citigo 3200rpm

 

Octavia TSi 2300rpm

 

Jag XF  1450rpm

[shyVRS245]

Remember a 1.1 litre Picanto we bought in 2009 which had about 67bhp and no torque with a 5 speed manual box sat at a very noisy 3,500 rpm at 70 mph.

[Ootohere]

A 2006 1.1 68ps 4 speed auto Kia Picanto i had would go around corners at 70 mph with just as many revs as needed with the O/D button in or out and still get 42 mpg no matter if driven as though it was not mine. It was not, it was one lady owners, never raced or rallied, just used at Autotests.

Edited 13 April, 2020 by Roottootemblowinootsoot

[shyVRS245]

2 minutes ago, Roottootemblowinootsoot said:

A 2006 1.1 68ps 4 speed auto Kia Picanto i had would go around corners at 70 mph with just as many revs as needed with the O/D button in or out and still get 42 mpg no matter if driven as though it was not mine. It was not, it was one lady owners, never raced or rallied, just used at Autotests.

Our manual Kia owned for 4 years averaged between 38-41mpg but the small 35 litre tank would mean seeking a garage every 235 miles or so.

[Steps65]

3 hours ago, logiclee said:

MPH/1000rpm differs for each model and on year.

 

We once run two Passats only a year apart 2.0TDi and there was massive difference in gearing.  The 4x4 may have different gearing to the FWD.

 

Our three current cars are very different motorway cruisers.

 

At 70mph.

 

Citigo 3200rpm

 

Octavia TSi 2300rpm

 

Jag XF  1450rpm

Thanks 

 

[Steps65]

2 hours ago, shyVRS245 said:

Remember a 1.1 litre Picanto we bought in 2009 which had about 67bhp and no torque with a 5 speed manual box sat at a very noisy 3,500 rpm at 70 mph.

Thanks

[brettikivi]

a quick bit of Excel later, I get this for my 1.0 TSI.,

 

Revs vs Speed: 

 

speed
revs	1	2	3	4	5	6
1000	8	15	23	30	38	45
1200	9	18	28	36	45	54
1400	11	21	32	42	53	63
1600	12	24	37	48	60	72
1800	14	27	41	54	68	81
2000	16	30	46	61	75	90
2200	17	33	50	67	83	99
2400	19	36	55	73	90	108
2600	20	39	60	79	98	117
2800	22	42	64	85	105	126
3000	23	45	69	91	113	136
3200	25	48	73	97	120	145
3400	26	51	78	103	128	154
3600	28	54	83	109	136	163
3800	30	57	87	115	143	172
4000	31	60	92	121	151	181
4200	33	63	96	127	158	190
4400	34	66	101	133	166	199
4600	36	69	106	139	173	208
4800	37	72	110	145	181	217
5000	39	75	115	151	188	226
5200	41	78	119	157	196	235
5400	42	81	124	163	203	244
5600	44	84	128	170	211	253
5800	45	87	133	176	218	262
6000	47	90	138	182	226	271
6200	48	93	142	188	233	280
6400	50	96	147	194	241	289
6600	51	99	151	200	248	298

 

All speeds in km/h, tyre size 1985mm (205/55R16), ratios as in this document: https://www.skoda-presse.de/model-preliminary/download/174?nutzung_ok=1

 

That flips back to 

 

	revs
speed	1	2	3	4	5	6
10	1284
15	1926	996
20	2568	1328	872
25	3210	1660	1090	826
30	3852	1992	1308	991
35	4494	2324	1526	1156	930
40	5136	2656	1744	1321	1063	885
45	5778	2988	1962	1487	1195	996
50	6419	3320	2180	1652	1328	1107
55		3652	2398	1817	1461	1217
60		3984	2615	1982	1594	1328
65		4317	2833	2147	1727	1439
70		4649	3051	2312	1859	1550
75		4981	3269	2478	1992	1660
80		5313	3487	2643	2125	1771
85		5645	3705	2808	2258	1882
90		5977	3923	2973	2391	1992
95		6309	4141	3138	2524	2103
100			4359	3303	2656	2214
105			4577	3469	2789	2324
110			4795	3634	2922	2435
115			5013	3799	3055	2546
120			5231	3964	3188	2656
125			5449	4129	3320	2767
130			5667	4294	3453	2878
135			5885	4460	3586	2988
140			6103	4625	3719	3099
145			6321	4790	3852	3210
150				4955	3984	3320
155				5120	4117	3431
160				5285	4250	3542
165				5451	4383	3652
170				5616	4516	3763

 

The TDI is more complex, with 2 output ratios given and I can't work out where they are relevant to. 

 

Formulas: 

 

revs =((speed *(1000/60)/wheel circumference *1000)*final drive)*gear ratio

speed =(((((revs/gear ratio)/final drive)*wheel circumference)*60)/1000)/1000

 

 - Bret

 

[shyVRS245]

Blimey and I thought I liked statistics.

[Steps65]

Thanks everyone, I was just hoping to find someone with the same car or even Octavia scout to be able to compare with mine.

regards to all.

[Gerrycan]

10 hours ago, Steps65 said:

Thanks everyone, I was just hoping to find someone with the same car or even Octavia scout to be able to compare with mine.

regards to all.

 

Not sure quite what you wanted to check with your request?

Unless you are prepared to go to some expense and bother you just have to accept the gearing as supplied by the manufacturer for the model. They are not going to change anything under warranty  

 

The speedometer is usually a bit out (optimistic) but easy to verify with a gps.

Not sure how you can check how accurate the revs are though without a bit of third party software and a dongle.

 

The revs you are quoting seem about right for the model based on my experience with other diesels.

 

Edited 14 April, 2020 by Gerrycan

[PetrolDave]

1 minute ago, Gerrycan said:

The speedometer is usually a bit out (optimistic) but easy to verify with a gps.

The speedo has to over-read under EU regulations (so even export models do) by between 0% and 10% - typically it will over-read by around 5-7%.

[Gerrycan]

27 minutes ago, PetrolDave said:

The speedo has to over-read under EU regulations (so even export models do) by between 0% and 10% - typically it will over-read by around 5-7%.

I guessed it was illegal to under-read and knew that up to 10% was legal so assumed the manufacturers 'aimed' for the mid point.

Friggin painful when it is near the 10% point though especially when you are stuck behind someone who is 5% (ish) under the speedo reading to avoid a fine believing the speedo is accurate.

[PetrolDave]

5 minutes ago, Gerrycan said:

I guessed it was illegal to under-read and knew that up to 10% was legal so assumed the manufacturers 'aimed' for the mid point.

Friggin painful when it is near the 10% point though especially when you are stuck behind someone who is 5% (ish) under the speedo reading to avoid a fine believing the speedo is accurate.

Very true!

 

I always have a GPS "speedo" (actually a device to warn of the location of speed cameras) in my cars.

[Steps65]

2 hours ago, Gerrycan said:

 

Not sure quite what you wanted to check with your request?

Unless you are prepared to go to some expense and bother you just have to accept the gearing as supplied by the manufacturer for the model. They are not going to change anything under warranty  

 

The speedometer is usually a bit out (optimistic) but easy to verify with a gps.

Not sure how you can check how accurate the revs are though without a bit of third party software and a dongle.

 

The revs you are quoting seem about right for the model based on my experience with other diesels.

 

Hi Gerrycan,

I'm not planning to change anything, but sometimes the relation between the revs and the speed showing problems in injectors, the throttle valve or the clutch and more things, I just wanted to know if it normal for such a car or not before start digging.

Thanks 

[Gerrycan]

Unless you have clutch slip on a manual then the speed/rev relationship in a given gear will remain the same whether or not there are engine issues.

Most vehicles with automatic gearboxes have longer gearing than their manual equivalent although it might only be a couple of hundred revs lower at highway speeds, as per manual and auto versions of my 1.4tsi.

 

The most extreme example of gearing difference I have read about is the Australian issued Honda Jazz. The engine is a fairly basic 1.5L NA, a lower spec than sold abroad and the manual version runs at about 3500 rpm at 110kph but the CVT auto version with same engine is about 2000 rpm at the same speed.

I'm going from memory, which might be as accurate as their speedometers  

[Ootohere]

Constant Variable Transmission / CVT really is a whole other kettle of fish.

A kettle of fish that works very well in some applications.

 

Then TSI's and TDI's RPM's are not worth comparing.  IMO.

 Then 5 or 6 speed manuals and 6 or 7 speed DSG's, or 7 speed Torque Converter Autos, or 8 or 9 speeds in a petrol turbo and a diesel turbo.

 

Once you get to 8,9,10 speed Auto's or Automated Manuals you are nearly in CVT country when changing gear 7 times or more in acceleration from 0-70 mph, 

or even 0-60 mph.

[Steps65]

1 hour ago, Gerrycan said:

Unless you have clutch slip on a manual then the speed/rev relationship in a given gear will remain the same whether or not there are engine issues.

Most vehicles with automatic gearboxes have longer gearing than their manual equivalent although it might only be a couple of hundred revs lower at highway speeds, as per manual and auto versions of my 1.4tsi.

 

The most extreme example of gearing difference I have read about is the Australian issued Honda Jazz. The engine is a fairly basic 1.5L NA, a lower spec than sold abroad and the manual version runs at about 3500 rpm at 110kph but the CVT auto version with same engine is about 2000 rpm at the same speed.

I'm going from memory, which might be as accurate as their speedometers  

Thanks for your help, I just wanted to make sure that everything is working as it should be.