Mk7.5 GTI - car feels slow, averaging 7.2s for 0-100 km/h

[Crescendo]

Hi all,

I'm unable to get below 7.0s for the 0-100 km/h sprint with my Mk7.5 GTI. Most of the time I'm averaging 7.1s or 7.2s, but have seen as high as 7.4s!

Here are the relevant factors:

• 2017 Mk7.5 GTI, 6 months old.
• Car is stock other than a K&N drop in filter + REMUS catback.
• DSG in sport mode, ASR is off.
• Dry road, sea level, negligable wind, <20 degrees C ambient temp.
• Michelin PS4 tires - good traction, minimal wheel-spin, no or minimal wheel hop (better than stock tires).
• Launch control NOT being used, as I feel the car should be able to easily achieve <7.0s without it.
• The best I could achieve WITH launch control was 6.9s.

I read on another forum to also test the 6th gear 80-120 km/h time, and that "somewhere close to 7 s" for this time is good. I'm not sure exactly what this is supposed to prove, because surely the turbo isn't doing much at such low RPMs, but nevertheless my car still only does it in 10.5s! Wtf?

I started measuring these times because the car has 'felt' slower than I remember, and this seems to agree with that. Getting 'used to' you cars power is definitely a real thing, but the car does seem slow.

Am I expecting too much? Would you guys be happy with >7.0s times on good tires? What do you think the issue might be?

Thanks

[tigger73]

Did you have the same problem before you fitted the exhaust?

You could have an exhaust leak or the system may not be as free flowing as you think. Put the stock system back on and retest.

Also go back to the standard panel filter. If the k&n has been too heavily oiled you may be causing issues. If your MAF sensor has oil on it this could be a possible cause. Pull the MAF sensor and check it is clean. If its fouled you may need to replace it.

Finally what fuel are you using? I’d run on BP Ultimate and put in some octane booster just to be 100% it’s not a fuel issue.

Also how many km on the car?


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[Crescendo]

Thanks for the reply, I appreciate it

Did you have the same problem before you fitted the exhaust?

I did not measure the 0-100 time with the old exhaust, mainly because I was still on the stock tires at the time and was getting really bad wheel hop. So unfortunately there's no baseline to compare, not very scientific of me.

You could have an exhaust leak or the system may not be as free flowing as you think. Put the stock system back on and retest.

I have since sold the stock exhaust so I don't have it anymore.

I had the REMUS catback fitted by a reputable shop, and then rechecked after 500 km (to confirm alignment and re-tighten any connections / bolts). My thinking is that any leaks would have been noticed at those times, but I did not specifically ask for them to look.

Would any reputable shop be able to diagnose a leak? I don't know anything about exhausts and I currently don't have a garage or any jack stands myself.

(Side note: REMUS is a good brand and it's all 3" piping so a restriction doesn't feel likely to me, but I agree anything is possible.)

Also go back to the standard panel filter. If the k&n has been too heavily oiled you may be causing issues. If your MAF sensor has oil on it this could be a possible cause. Pull the MAF sensor and check it is clean. If its fouled you may need to replace it.

The performance was the same with the standard paper filter.

Also, it's my understanding there is no MAF sensor in the intake for the MK7? Could be wrong about that.

Finally what fuel are you using? I’d run on BP Ultimate and put in some octane booster just to be 100% it’s not a fuel issue.

I am using the 98 octane fuel from Puma, whatever it is.

I will try BP Ultimate this weekend, that's easy enough to do. What booster do you recommend, that Nulon stuff from Supercheap?

Also how many km on the car?

5000 km

- - -

Do you think it could be a small boost leak somewhere? I forgot to mention, but at about 4000km while I was driving one night I noticed an audible increase in the 'air rushing' sound that comes on at approx 2000-3000 rpm. It wasn't a big increase in loudness, but it was enough to notice that the sound signature had changed. I was still on the stock paper filter at the time and the exhaust had already been for a month by then.

I've never owned a turbo car before, so I promised myself I wouldn't worry about any 'funny noises' when the boost comes on, but now I'm not so sure.

[tigger73]

I did not measure the 0-100 time with the old exhaust, mainly because I was still on the stock tires at the time and was getting really bad wheel hop. So unfortunately there's no baseline to compare, not very scientific of me.

OK so stock 0-100 is 6.4sec which is usually a fairly conservative figure. You should be able to get this without too many issues.

I have since sold the stock exhaust so I don't have it anymore.

I had the REMUS catback fitted by a reputable shop, and then rechecked after 500 km (to confirm alignment and re-tighten any connections / bolts). My thinking is that any leaks would have been noticed at those times, but I did not specifically ask for them to look.

Would any reputable shop be able to diagnose a leak? I don't know anything about exhausts and I currently don't have a garage or any jack stands myself.

(Side note: REMUS is a good brand and it's all 3" piping so a restriction doesn't feel likely to me, but I agree anything is possible.)

It's probably not so much a problem with restriction. You can actually cause the air flow in the exhauist to stall if you increase the pipe size. It's possible that just fitting a larger cat-back is causing some undesirable issues for the exhaust flow and you're not getting the power. This is one possibility.

YOu can check for exhaust leaks by putting the car up on a hoist and looking for large streaks of soot.... it's a bit of a give-away

The performance was the same with the standard paper filter.

Also, it's my understanding there is no MAF sensor in the intake for the MK7? Could be wrong about that.

Yeah you're right - no MAF on the Mk7. It;s certainly been a problem on earlier models where oil from an overl;y oiled air filter gets on the airt flow sensor and kills it.

I am using the 98 octane fuel from Puma, whatever it is.

I will try BP Ultimate this weekend, that's easy enough to do. What booster do you recommend, that Nulon stuff from Supercheap?

Yeah any octane booster should do. No idea on Puma fuel, though if you have low octane fuel it can cause the ECU to pull timing and not make power. Run your tank down low and then refill.

5000 km

OK so should be run in by now. Some cars won't free up until closer to 10,000km but I think this impacts more on fuel economy than peak power.

Do you think it could be a small boost leak somewhere? I forgot to mention, but at about 4000km while I was driving one night I noticed an audible increase in the 'air rushing' sound that comes on at approx 2000-3000 rpm. It wasn't a big increase in loudness, but it was enough to notice that the sound signature had changed. I was still on the stock paper filter at the time and the exhaust had already been for a month by then.

I've never owned a turbo car before, so I promised myself I wouldn't worry about any 'funny noises' when the boost comes on, but now I'm not so sure.

It could be any one of a number of things. Hardest thing is that with the car modified VW are going to take one look at it and blame the modifications. I'd be looking to see if I could get your hands on a stock cat-back just to test. Otherwise you're looking for boost leaks. You may need to take it to a reputable independent workshop if VW is going to play funny buggers.

[Crescendo]

I'm no expert, so what you say about the exhaust could very well be true, but what you described is not my understanding of how a standard cat-back will behave. It's my understanding that with a less restrictive exhaust you'd maybe lose a bit of power/torque in the low RPM range due to lowered exhaust velocity, but you get it back plus some extra at the high RPM range. The effect will even then be pretty small because the 'restrictive' stock downpipe is still in place, which means the critical part for low RPM exhaust velocity is not changing much.

In any case, REMUS does have dyno runs showing a small improvement in performance for a stock Mk7.5 (a tiny improvement mind you, cat-back is really for sound only).

Regarding dealerships, I guess I never really thought that a cat-back would be a cause for concern. Of course everything from the cat back can no longer be warrantied because it's not a VW part, but it seems a stretch to argue that it would HURT performance, when the opposite is proven by dyno results.

But you're right, who knows what a dealer or VW will think. Sometimes logic doesn't come into it, or they have a really strict no mods mindset.

On that point, do most guys NOT mod the exhaust while they are within warranty? For sure you would NEVER do turbo-back or downpipe if you want hassle-free warranty, but this is different. Everything that is critical for stock exhaust performance is from the cat fowards, which is untouched, making a cat-back benign.

[Crescendo]

Before I go any further with this, I want to rule out the way that I'm measuring the time. I was using a stopwatch first, and then the car's in-built lap timer using the hand controls, both of which are very far from scientific.

With that in mind, I took some videos tonight and uploaded them to YouTube for you all to look at.

I measured the times frame by frame, using my video editing software. The question is, when do you START measuring the time? From first tacho movement, or first speedo movement (speedos have a lot of slop)? I figured I would post times from both methods:

Run 1 - YouTube - tach: 6.99 s ; speedo: 6.15 s

Run 2 - YouTube- tach: 7.02 s ; speedo: 6.86 s

Run 3 - YouTube- tach: 7.02 ; speedo: 6.85 s

Hmmm, I guess the times aren't as bad as I thought, and traction does still seem to be a factor given the 6.15 s result on the first run.

I think I might be an insane person looking for problems. I'll let you guys be the judge and jury

[blower]

Before I go any further with this, I want to rule out the way that I'm measuring the time. I was using a stopwatch first, and then the car's in-built lap timer using the hand controls, both of which are very far from scientific.

With that in mind, I took some videos tonight and uploaded them to YouTube for you all to look at.

I measured the times frame by frame, using my video editing software. The question is, when do you START measuring the time? From first tacho movement, or first speedo movement (speedos have a lot of slop)? I figured I would post times from both methods:

Run 1 - YouTube - tach: 6.99 s ; speedo: 6.15 s

Run 2 - YouTube- tach: 7.02 s ; speedo: 6.86 s

Run 3 - YouTube- tach: 7.02 ; speedo: 6.85 s

Hmmm, I guess the times aren't as bad as I thought, and traction does still seem to be a factor given the 6.15 s result on the first run.

I think I might be an insane person looking for problems. I'll let you guys be the judge and jury

I've always measured from tach movement - as it effectively includes clutch engagement delay (which you should account for as that's what VW would be taking into account on it's measurements for a 0-100km/h)....many people just use speedo movement - that is more comparable to a gps measuring device.

Another thing to note is that VW speedo's usually over-reads by about 5% (so ya really need to be measuring your time when speedo reads 105km/h to get a more accurate 0-100km/h)

[Crescendo]

I've always measured from tach movement - as it effectively includes clutch engagement delay (which you should account for as that's what VW would be taking into account on it's measurements for a 0-100km/h)....many people just use speedo movement - that is more comparable to a gps measuring device.

Another thing to note is that VW speedo's usually over-reads by about 5% (so ya really need to be measuring your time when speedo reads 105km/h to get a more accurate 0-100km/h)

I took the speedo into account by measuring the end frame when the entire needle was completely past the 100 km/h tick mark. That will be about 103-104 km/h.

If first tacho movement is the correct measurement standard, then I think the car is slow.

[Brycem]

Crescendo
I’m not one for measuring acceleration times so can’t assist with any of your questions on that issue. I am however looking to install a catback on my 7.5 manual gti as I find the current exhaust note dull at best. Did you go resonated or non resonated for the centre section? I assume you bought it from the Remus distributor in Melbourne? Any haggling on price? And have you been happy with the exhaust sound and quality? Any droning? Finally did you consider any other options?
Thanks
Brycem

[Crescendo]

Crescendo
I’m not one for measuring acceleration times so can’t assist with any of your questions on that issue. I am however looking to install a catback on my 7.5 manual gti as I find the current exhaust note dull at best. Did you go resonated or non resonated for the centre section? I assume you bought it from the Remus distributor in Melbourne? Any haggling on price? And have you been happy with the exhaust sound and quality? Any droning? Finally did you consider any other options?
Thanks
Brycem

I wrote a full review of the exhaust from a sound/livability perspective in this thread: MK7.5 GTI Remus Exhaust + Racingline stage 1

It's the fully resonated version (non-resonated would have been a mistake for me), and I didn't even think to try haggling.

I didn't seriously consider another exhaust except the Akrapovic slip-on, but that was too expensive. All the other usual suspects seemed to have concerns about quality/fitment (Invidia, Xforce, etc), or were too loud and 'boy racer' (Borla).