(Q) RPM at certain speeds

BennyBuddz

Active Member
May 11, 2015
3
0
Israel
Hello, new to this forum.

One quick question, my current garage, which specializes in the VW cartel,
told me that my car is fine, but I want to hear your take on this:

My idle RPM is around 700 which can actually be felt through the car LOL
but the real problem is that at 120 km/h the RPM is 3500 which is kinda high for a 1.8,
140 km/h is a round 4000.

Wanting to double check, took my father's 2006 Focus (a 1.6) at the same straight highway at 120 km/h, which only took 3000 RPM.

Any suggestions?? Maybe something I can do by myself? Save some shekels??
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
I'm going to assume you have an APG engine, although at that age it could also be AGN.

Idle speed should be 660 rpm (760 for AGN)

Max power is at 6000 rpm, and 3500 rpm is where the torque peak is. This seems to me to be a perfectly reasonable rpm for 75 mph (120 kph).

I'm not sure why you think this is high rpm "for a 1.8" . Modern F1 units, for example, are 1.6 litre engines and are regulated to 15,000 rpm. In earlier years, 20,000 rpm was not unusual.

What do you think is wrong about your car?
 

BennyBuddz

Active Member
May 11, 2015
3
0
Israel
I think it's a bit excessive, since the larger engine my car should have more power at lower RPM,
that's why 4000 RPM for 120 km/h seems strange.
Plus, when idling i can actually feel vibrations through the steering wheel, since my car only did 40k miles but it is 13 year old, i thought it might be either low RPM or maybe dried out engine mounts.

Another thing regarding high RPM, the car is glitchy when cruising, sometimes when i only graze the throttle it launches a bit hard, and sometimes when i'm slowly releasing the throttle after acceleration i can feel a kick as if i'm dropping the clutch on a low gear (btw it's an automatic).

Any ideas then? if it's not an RPM issue?
 

Muttley

Catch that diesel!
Mar 17, 2006
4,987
31
North Kent
One caveat before I go further - I assume your car has original wheels and tyres, or ones that are the equivalent to the originals (205/55 R16 or 205/50 R17). If you have a smaller diameter wheel/tyre combination then the engine will need to rev faster for a given road speed... however your speedo will also read false.

Road speed per 1000 rpm in any gear is set by the gearbox and the ratios contained in it. Unless you have had a different gearbox put on, the car is doing what Seat designed it to do.

I don't have much experience of automatics, so I can't advise on the juddering at idle or the glitchy cruise experience. It does sound like it could be auto-gearbox related though.
 
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