I’ve made a few comments on the discord about the V6 sounds before, but I could never go into a ton of detail and it would get lost relatively quickly. So here’s a thread about it! I’ll try to keep it as clear as I can, but… if i say something stupid or nonsensical, feel free to ask. 
(one more thing - assuming these suggestions even get approved in the first place, I don’t expect them to come immediately. Getting the game stable and working comes first. Content comes after, and I have no issues waiting for a more polished game.)
With that said,
This is what I don’t like about Automation V6s currently
This isn’t an angry rant btw, just some comments I wanted to bring up
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Lack of volume progression – Engines get louder the higher they rev, but automation V6s don’t do that. At lower revs, the volume does actually increase appropriately, but stops after 4,000 rpm. Above 5,000 rpm, it actually seems like it gets quieter. Interestingly, race intakes don’t seem to be affected by this.
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Drone – Between 3,000 and 3,500 rpm they’re very droney, even with a standard intake and 2 mufflers. Im not sure how this could be fixed, but it would be a nice QOL improvement
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Snore – Letting off from higher revs, they make a noise that can best be described as… the exhale part of a snore. I have no idea why this is a thing and I can’t seem to find any irl examples either. This is especially prevalent with performance and race intakes.
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Overall soundfile – I know, this is the worst point because it’s subjective, but stay with me. Honestly, auto V6s with a standard or performance intake just sound… a bit wrong. The soundfile itself falls flat on its face at higher revs, which leaves a rather synthetic and weedy sounding engine. The other thing is that auto V6s go from a growly purr into an inline-3-esque dulled ‘shriek’ after 6,000. This, imo, does not sound realistic or particularly healthy; from what I’ve experienced, irl V6s generally transition from a purr into a throaty roar, not so much of a dulled “reeeeeeee”.
apologies if i sound like im talking out of my ass, but if i do… that’s because i kinda am, I don’t know proper audio words lmao
To improve them, this is what I suggest
Disclaimer: idk what’s possible or how much time / energy would be required to implement these. i’m just throwing ideas out there 
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Progressively increase volume in the upper rev range. Even if the soundfiles themselves were otherwise unchanged, this would make a nice difference
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Fix the drone, if possible
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Get rid of the snore. It just sounds weird and doesn’t match anything irl
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Last one… I don’t know how willing y’all are to make more in-depth soundfile edits, but if that’s a viable suggestion, try to make V6s a bit smoother at lower revs and sound more realistic, kind of like these:
Six (6) video references
I’ve tried to get a fairly decent blend of engines, so… hopefully these can be of some help to get going in the right direction.
- HiAce has a good overall “generic base” sound. It revs freely and is smooth, with a decent top end roar. Also has some mechanical whirr
- RC has a very similar Toyota V6, but it’s slightly smoother and quieter here. Very healthy sounding engine overall, and my personal favorite
- Acadia’s V6 is deeper and throatier, but still pretty smooth, and the same basic principles still apply.
- PRV V6 has a unique character to it without being super specific, and it helps to have an older engine on the list. Sound is overall pretty solid, growing from a growl to a roar in the upper rev range (I think you’re getting the theme by now lol)
- Hyundai/Kia/Genesis 3.8 is a bit raspy revving freely, but the top end is good. Sounds more similar to the others when under load.
- Pentastar 3.6 is also pretty decent “base generic”, and is sort of a mix of toyota and GM V6s.
So although I’m not necessarily advocating a revamp of engine sounds, I figured I’d join the fray anyway and say if the above are great examples of “normal” V6s, below are samples of “sporty/racy” V6s.