V8V upgrade man maths and noob questions

[stevieboy123]

The initial message was deleted from this topic on 21 February 2025 at 18:03

[LTP]

Hi Steve.

I have a 2015 4.7 non-S V8V SSII, but can only comment on two of your points:

• my V8V drops no liquids on any floor, and never has in nearly 6 years
• for reference my V8V averages around 22 mpg; I don’t cane it but I’m not particularly slow, and it does a mixture of journeys, including weekend shopping. I think 911s are known for being comparitively fuel-efficient

[NickXX]

The oem manifolds and cats I'd expect would be worth £500ish for all of them (have seen bits go over the years on Facebook groups), but not sure how active the market is. I've kept mine in case I ever need to revert back.

I think I got a very small increase in fuel efficiency - 1-2mpg on a cruise, but don't expect it to radically change (I think I can get around 26mpg if I'm careful on the motorway). It does make the car more fun to drive though, so this will likely kill any gains as you'll be revving it out more.

I don't think coolant leaks are common, so I would get it checked out. Radiators tend to have issues with age, so could possibly be one of the plastic components which has failed. If you take the slam panel cover off the engine bay, you may be able to track it.

People may have different experiences, but air conditioning seems to be a bit of a dark art with them. It took a few goes for a dealer to fix an issue I had, which was a leaky condenser pipe that got damaged when they repaired an oil leak.

[Dewi 2]

stevieboy123 said:

Could those that have done a cats and manifolds suggest what would be realistic to expect if you were to sell the oem bits on (manifolds with primary cats and secondary cats)

Those that have upgraded - did you see a real world mpg improvement too?

Your description appears to indicate that your V8V must be post 2010, ie. had/has manifold cats.
Therefore a good exhaust upgrade usually involves tubular manifolds and sports cats, say at least £3,000 fitted.

If mpg is part of the consideration, then not spending that £3,000 could be one idea. Buy a huge quantity of petrol with that.
I am sometimes asked, by people who have no interest in cars, "Does it use a lot of petrol?"
My usual reply tends to be, "The last time this car went to a filling station was seven months ago, so the answer must be no".

[V8V Pete]

I haven't sold my old manifolds/cats just in case things go badly downhill one day and it will only pass an MOT with the OEM stuff back on whatever the emissions test results may be. However, I doubt they have much value or there is much demand in the used market because I don't think they go wrong very often and they're quite hard to steal as the car is so low.

I think there may be a noticeable (if small) improvement in efficiency when cruising at 70mph on the motorway. However, the changes that potentially make the engine more efficient also make it more fun to work hard and perfect your redline gear shifts, so I still average just over 20mpg with a very mixed usage profile. Don't worry about it and don't compare it to your 911; it's a NA 4.7 litre V8 at the end of the day and, unless your 911 was a GT3, sounds much better when uncorked.

My mirrors were done by BR, which is near Stratford, so not too far from the SE. They do a very good job.

Mine has never dropped any fluids (even when the engine destroyed itself) and I've never had to top up the coolant in 65K miles between my 2 Vantages.

My Aircon has been very good and only been re-gassed when the engine was rebuilt as far as I know which is pretty good for an 11 year old car. AFAIK the pumps are currently on backorder and whilst they are a Denso part are apparently unique to AML (happy to be corrected on this if I'm wrong). You may have to get used to the parts situation: often unique, stupidly expensive and unavailable.

Anyway, I love my modified/up-graded Vantage S and I've owned it for nearly 10 years now so the positives must still massively outweigh the negatives or else it would have gone. Enjoy your new car!