MrFunk

Thanks for all the reviews.
No negatives with this system at all?

justince

It's still new to me, but if I had one gripe -- with the top down at around 2200 rpm there's a bit of drone. Interestingly, with the top up, I don't notice the drone. Note that I did the collar mod, so I imagine with the valves closed this would be eliminated. Some other observations:

• With the collar mod, under light loads, it isn't obnoxiously loud. I imagine it's probably close to stock (never collar modded stock exhaust). But, under high loads and high rpm, this thing really does scream and is probably a bit louder than I would have personally liked. Volume wise, I think stock at WOT was a good level. Collar mod also makes the transition between valves open/closed way less noticeable.
• Butt dyno feels no difference from stock, to be expected with stock headers/tune.
• Lots of pops and bangs under decel, but it does sound authentic (unlike the 981 pops and bangs which seemed super artificial)
• It's certainly anecdotal, but I ceramic coated my link pipes (techline coating) and I definitely notice less heat from the rear wheel wells after a drive.
• I mainly did this for a change in tone, which I'm very satisfied with. It's reignited a love I had for the car. I was always a bit let down that my old 981 sounded better than this. 981 still sounds more....refined and boutique? 718 with kline sounds much racier than the 981 now (and louder). Not better or worse, just different.
• The way I look at the drone, it almost completely masks the injector chirping sound these motors make so it's a win

UncleDude

@justince when you say drone do you mean a constant unpleasant sound under even throttle at that RPM (to me that is real drone). Stock this system has none of that IME, and only a slight bloom of bass around 2200-2400 rpm that is *nothing* like the real resonance issues my other system had (like rattle the cabin). Oddly enough I have the collars on too, and I put them in the most conservative position and it eliminated that little bass bloom, I have not noticed any negative cruising sounds, and it definitely makes it a bit more raucous valves “closed”. I’m still not sure I’ll keep them, and agree on the transition closed to open, I can barely hear it.

Agree on the top end volume. I used to think it was close to stock but I think it is a good deal louder.

UncleDude

The only negative for me was not doing it first! If you’re considering it, you should really read this thread. Make a pot of coffee and watch all the videos etc. The system is pretty well documented in here and I think the reporting has been as honest as possible (we all have some bias after spending thousands LOL).

justince

Yeah, there's a bit in that 2200-2400 rpm range while the engine is under load. Gone when lifting off throttle. It is not remotely close to a deal breaker or anything like that. Only noticable with top down...it's not super unpleasant, and it doesn't cause any rattle or anything like that.

If that came off as me complaining about it, that was not the intended effect. It's just something that I noticed and figure I'd mention it since he asked. I imagine with OEM valves it's probably completely gone, but then you'll hear more injector chirping -- pick your poison. I also put the collars in the most conservative position and personally I love it.

MrFunk

Has the topic come up of the now "open void" where the rear box once was (once the Kline system is installed)? It seems that flat bottom portion of the OEM rear box is used in conjunction with the rear diffuser to create a smooth transition from underside of vehicle to rear diffuser... I guess that could be considered a negative? I guess that would be a minimal impact on aero... especially on a street car... I could have sworn I read this one topic come up before.

flynlo

None in my opinion. I can produce drone if I try and it is in a RPM regime I do not visit often. Basically it is a low RPM high load/throttle. IOW, cruising along in 6th gear at 45mph and then mashing the throttle instead of downshifting. I don’t do that so it doesn’t happen. I do think it would be interesting for those that mention this to clarify the type of transmission they have. There is a tendency to be a little lazy with a PDK car and allow the computer to pick the RPM….in which case you are more likely to encounter that RPM regime. Especially if in “Normal” mode and the computer is more concerned with economy and low RPMs and has a tendency to be more stubborn on downshifting.

I will reiterate….in my experience and opinion, this system has no drone.

Josh_357

To remind folks, who say they have drone, check the clearance of the rear system to the heat shielding under the rear hatch area. Some folks, myself included, found some areas were touching the heat shielding under the floor. This can add drone, under certain load conditions, especially decell in gear.

Josh_357

Started mocking up something in CAD for prototype this winter, for this!

jimdillard

Can somebody please point me to the Kline "Collar Mod" in this string or elsewhere? I'd like to study it for my Kline Inconel system. Thank you.

Josh_357

I used the same collars as the stock system, 6mm rod size. This is the lowest position I could get without it binding with the valve arm. A little goes a long way.

jimdillard

Thank you. So you don't have to repeat what's been written elsewhere...is there a description of how this collar "works" elsewhere in this thread?

jamesrg

https://rennlist.com/forums/718-gts-...d-options.html

UncleDude

Josh how did you bend / move the heat shielding? I've been living with the collars on the valves for a few weeks (same position as Josh's above) and I would say it makes a pretty significant difference. I can barely hear the valve transition now, and I've noticed I have to be more gentle on the throttle around town due to the added volume valves closed.

MrFunk

I think it was perhaps a post of yours I'm remembering.
Without a wind tunnel I guess it would be impossible to know what reduction in overall aero function results by removing the OEM rear box.
I think the Akrapovic system is the only one with a similar design to the OEM system retaining that smooth lower portion.