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2018 Elantra GT GLS (Manual)
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Discussion Starter · #1 ·
Hello everyone,

I need help regarding a problem I have with my car.
I have bought a used Elantra GT 2018 (Nu engine 2.0L) Manual Transmission about 2 months ago. When I drive with partial throttle it accelerates fairly for that particular throttle, but when I need more acceleration and push full throttle I get less acceleration with marked worsening in Instant Fuel Economy with loud exhaust noise.

Partial throttle (given certain gear and RPM):
  • Fair acceleration
  • Normal exhaust noise
  • Fair instant fuel economy

Full throttle (given the same gear and RPM):
  • Less acceleration
  • Loud exhaust noise
  • Markedly worse instant fuel economy

What could cause this problem? How can I investigate this?

PS: I have no access to any authorized Hyundai service where I live, so I'll have to diagnose this issue on my own.
 

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Iy may have a blocked exhaust. At 2018 model It's not common but not impossible. You can check with a vacuum/boost gauge or remove the O2 sensor (safety) and see if it regains some of the power.
 

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Need more info like, what speed and gear are you in? Granted it's not a rocket, but if you use the gears it will get up and go.
 

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2018 Elantra GT GLS (Manual)
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Discussion Starter · #4 ·
Need more info like, what speed and gear are you in? Granted it's not a rocket, but if you use the gears it will get up and go.
It is generally applicable to any gear ratio with any speed/RPM. Take, for example, at second gear with RPM of 1500 to 2000
 

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You are not going to get a lot of acceleration at 1500 rpm. The motor doesn't wake up till it's over 2000.
 

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Discussion Starter · #6 ·
You are not going to get a lot of acceleration at 1500 rpm. The motor doesn't wake up till it's over 2000.
Well, I just tried the same scenario at approximately 2500. No acceleration gain; just rapid worsening of instant fuel economy with loud exhaust noise.
 

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Well, I just tried the same scenario at approximately 2500. No acceleration gain; just rapid worsening of instant fuel economy with loud exhaust noise.
That is not normal, I get very good acceleration at 2500, granted it get's louder.
 

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Discussion Starter · #8 ·
Need more info like, what speed and gear are you in? Granted it's not a rocket, but if you use the gears it will get up and go.
To provide sufficient info, I've collected sensor data for certain duration of driving, and I've selected some of the seemingly useful sensors for a particular period, during which I had pushed full throttle twice on each of 2nd, 3rd, and 4th gears. You can see clearly the slowly rising RPM despite those full-throttle events.

What might cause this?
441575
 

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Given it's a manual transmission, it sounds like the friction disc (clutch) is worn or glazed and it's slipping under load. If so, it will require renewing the disc and related components.
 

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Discussion Starter · #10 ·
Given it's a manual transmission, it sounds like the friction disc (clutch) is worn or glazed and it's slipping under load. If so, it will require renewing the disc and related components.
Wouldn't a slipping clutch show HIGH RPM with LOW SPEED? If you take a look at the last graph chart you can clearly see the engine speed/RPM (thick red line) is matching with the vehicle speed (dark green line), which removes the doubts about a failing clutch.
What I'm experiencing is the inability to raise both RPM and vehicle speed under load.
 

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Can you take a video with your windows down, showing your cluster gauge and do a pull in second gear? Like 1500rpm to maybe 5k if you can?

Might give us a better understanding.
 
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