Gen-F GTS exhaust - advice sought

Gen-F GTS exhaust - advice sought

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AndrewJF

Original Poster:

6 posts

23 months

Monday 27th June 2022
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Morning all,

I’m a newbie to the forum so a virtual hello to everyone and thanks for reading the post.

I’m seeking some advice about my Gen-F1 GTS exhaust. The last posts I can find on VXR8 exhausts are around 2014 which I assume relate to the E series but if I’ve missed something more recent please accept my apologies and point me in the right direction.

I’ve owned my 2015 GTS from new and always thought some more V8-ness from the exhaust would be good. I finally got around to buying a Walkinshaw cat back system and they fitted it for me a couple of months ago.

It does indeed make a better noise above about 2500rpm (and I’d be quite happy if it was louder still in that part of the rev range). However, it has a bad drone between about 1500 and 2000 rpm. I do a lot of motorway miles and, between 60 and 80mph, it’s pretty unpleasant and gives everyone a headache after an hour+.

Walkinshaw tell me they’ve sold a lot of these systems with no reports of a drone but, nonetheless, have been very reasonable in offering me a deal to swap back to the original exhaust.

The options I can see are:

1. Swap back to the original exhaust. I don’t like this as it leaves me back at the start and the original exhaust will need replacing soon anyway as it’s corroding. Nonetheless I will have to do it unless I can find a different solution as the drone is too bad.

2. Spend more money on replacing cats and headers. The hope is this will allow the individual cylinder detonations to be heard thus breaking up the drone (and will make an even better noise higher up the rev range). Obviously the risk is that I spend more money just to make the drone even louder.

3. Try to tune out the drone. Walkinshaw don’t want to risk trying but perhaps a specialist exhaust outfit might be able to do it without replacing the whole system?

Any comments or advice very gratefully received. In particular, has anyone managed to tune out a drone from this type of system and if so, who did the work?

Many thanks

Andrew

vxr2010

2,566 posts

160 months

Monday 27th June 2022
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go to an exhaust place and ask their advice , you could add a mid section in , more back noise will be more general noise , is yours not bi modal ? could it be made bi modal if it is not already , i flick the switch on mine goes very quiet , last comment in humour drive at 65 or 85 mph

bigwheel

1,618 posts

215 months

Monday 27th June 2022
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Monaros tend to drone with cat back, mine only happens in a narrow band that I can avoid.
Forum members said that adding headers eliminates drone.

AndrewJF

Original Poster:

6 posts

23 months

Monday 27th June 2022
quotequote all
vxr2010 said:
go to an exhaust place and ask their advice , you could add a mid section in , more back noise will be more general noise , is yours not bi modal ? could it be made bi modal if it is not already , i flick the switch on mine goes very quiet , last comment in humour drive at 65 or 85 mph
Thanks for your reply. Yes, mine is bimodal but currently ECU controlled rather than manually switchable. It’s in quiet model normally on the motorway. I can force it into loud mode by reversing the 1-way valve but that just makes the drone louder. Changing down to 5th also gets around the problem but hurts a bit with petrol prices as they are (although I accept that nobody buys a 6.2l supercharged V8 for its fuel economy).

vxr2010

2,566 posts

160 months

Monday 27th June 2022
quotequote all
i re wired mine so i have manual control over it , i thought the f series could be adjusted by your info display , re wiring was easy , if you get too short silencers welded in pre back box it will have an impact , but a decent exhaust place can advise , im in herts and use emp not sure where you are based

AndrewJF

Original Poster:

6 posts

23 months

Monday 27th June 2022
quotequote all
The EDI has a screen displaying exhaust mode on a chart of throttle % v rpm but I don’t think there’s a way of manually changing the mode through the EDI. Walkinshaw can install a manual switch (but currently have the switch on back order). I’m based near Worcester but happy to travel for expertise and experience so will talk to EMP - thanks very much for that.

vxr2010

2,566 posts

160 months

Monday 27th June 2022
quotequote all
to do the switch it just needed a bit of re wiring and a simple on off switch that can be secured out of the way , just need to remember to turn it off when you park up and won’t drive the car for a while , i have the standard ls3 maloo ve 2 exhaust , i deleted the mid section silencers , then got emp to re do the back boxes in a bigger bore , in quiet bi modal mode it’s the quietest car i have , and no motorway drone unlike my monaro , but in noisy mode then it’s probably the loudest i have , plus a few pops and bangs

vxr2010

2,566 posts

160 months

Monday 27th June 2022
quotequote all

vxr2010

2,566 posts

160 months

Monday 27th June 2022
quotequote all
well that did not work ,

i can send you the noise difference is you email me , but can’t seem to upload a clip on here only a photo

fred bloggs

1,308 posts

201 months

Thursday 30th June 2022
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Headers eliminated the drone completely for me. Also bumps up torque through the whole rev range. You will need a tune.

Should really do headers straight away with the exhaust ,as only they make an actual difference.

Edited by fred bloggs on Thursday 30th June 11:03

AndrewJF

Original Poster:

6 posts

23 months

Wednesday 7th September 2022
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Thanks very much to everyone who replied/ sent me a DM about this. A quick update:

I decided to get the headers and cats done with Walkinshaw and picked the car up last week. The drone is much improved, both in terms of volume and narrower rev band, but is still there. The weird thing is that it did vanish completely for about 10 miles on the drive home, following a hill descent for a couple of miles in third gear with a trailing throttle. But then the drone gradually returned and I haven’t been able to replicate the vanishing act since.

The remaining drone is coming from the rear silencer cans - with the car on the ramp and the throttle set to give 1750rpm, the cavity between the silencer and the rear bumper is deafening - with the driver’s side much worse than the passenger’s side (inside, the drone is also noticeably louder from the driver’s seat).

I’m inclined to try some Dynamat/ Dynaliner in the boot next just to get the drone volume down a bit more. If that fails, Walkinshaw suggested opening up one or both silencer cans and repacking them. Any other suggestions gratefully received.

And on the plus side, I now have a much better sound throughout most of the rev range and changing down to fifth eliminates the drone if a motorway trip becomes unbearable.

AndrewJF

Original Poster:

6 posts

23 months

Thursday 14th September 2023
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Just to close off this thread and in case useful to any other Gen-F owners:

I worked through the ideas and suggestions that everyone very kindly offered without any noticeable effect on the exhaust drone. I also tried using modern sound- deadening solutions all over the floor pan and boot which unexpectedly seemed to make the drone even worse.

Eventually a mate who works in the restoration business suggested simply extending the tail pipes. Success! The drone has disappeared completely leaving a loud, well-defined V8 sound track at all rpm.

Previously the tail pipes exited into a cavity under the boot floor with plenty of sheet metal around to resonate. Extending the outer pair of pipes (the ones without the valves - see photo) into the embellishers seems to have removed the source of the resonance from the cavity and also lowered the resonant frequency of the source.

Anyway, thanks again for the help with this and hope it’s of some use to others.