ACT manifolds

[motul1974]

Hey Folks, is there anybody on here running both acts performance exhaust manifolds and one of their carbon air boxes?

I'd fairly well decided on going for CF's tuned equal length set up, but with more and more thought and research, I've come to the conclusion that for 'my' wallet, their somewhat over kill. Man maths calculating I could have BOTH acts inlet and exhaust manifolds for similar money, if I chose to go all the way that is!

I understand the carbon boxes are not about BHP increases before anyone says it, but they look great and I've no doubt there's better flow over the trumpets - I'm guessing more noise to boot? A good noise with the sports manifolds I wonder???

[motul1974]

Hi Phazed, so you recommend both. What they like for sound together? I a CF intake manifold on my e30 m3 many years and was worth it for the sound alone - i except revvy 4pot is not the same.
I prefer the tripple manifold for its looks, although I except it may be OTT on my 4.6 especially whem compared to yours, but the heart want a what the heart wants! Lol

[motul1974]

phazed said:

I like the Chimaru sound

Lol...that's what i like! May even prefer it to what I've heard of the equal tuned manifolds.

Seriously considered CF's equal tuned set up though. I've no doubt their probably the ultimate set up on a rv8, but the potential issues about having to fit a CAT to them at a later date if I was struggling with emissions READ: getting a friendly mot centre!
The ACT set up is clearly cat friendly without resorting to playing with cats in place of the silencer, with subsequent further silencing required further down the system. ALL doable, just extra cost and hassle I could do without.

'Lottery win' set up would be CF's tuned ceramic coated to keep heat in, leading to cats in front of a smaller silencer with silencer tail pipes....just too much money for I'm guessing not a huge gain - different though!

Acts performance set up also allows me to spread the financial pain of all this work a little more! Lol

[motul1974]

spitfire4v8 said:

Not quite sure what you mean about not being able to fit a catalyst, it's these I'm referring to :

https://www.facebook.com/clivefppa/photos/a.215180...


It's only me that doesn't like the subaru warble and motorway drone / pressure pulses in the cabin from the std setup then ..

Ahh, those ones!....I spoke to Clive about these a while ago. At that stage he'd only made them once for a guy with Wildcat heads and not the rv8, so he'd no experience of them on my engine.

[motul1974]

...oh, and they're 1600quid if I recall + the y piece.

The idea of them does complicate decisions though.....CF SHINEY bits and i can fit my decat pipe at mot time of necessary...hmmm lol

Dearer option than ACTs mind.

[motul1974]

angus337 said:

I also asked Clive about them a few months ago, I already have clive's decat pipe, so though they woud be a good option for me. Unfortunately not availabe yet, and the design would need modifying on the passenger side to accomodate the standard air inlet route.

My plan at the moment is to go with the ACT manifolds and sell the y piece. For the MOT I think ill try getting a couple of cheap sports cats made up to fit the ACT pipes, as i can't really justify the cost of the ACT cats for one days use a year.

Yeah, what's it with 800quid for the ACTs cats?...is that not VERY dear, or am I missing something??

[motul1974]

phazed said:

Looking good, but you think a triple manifold on a 4.6 running gems would be too much? Usual big bales, 45mm trumpets etc.

[motul1974]

The ideà of a carbon triple, or even double plenums, was born out of 'man maths'....I could have BOTH ACTs exhaust and inlet manifolds for the price of my previously interested cf equal/tuned set up.

It does sound like sticking with my 72mm plenum will more than suffice for now.......THANKS! lol

[motul1974]

900T-R said:

I've had a 72 mm throttle on the std plenum, ACT twin throttle and now a triple throttle plenum on my 4.3 (10.5ish cr, fairly elaborately modified heads but std sized valves, now replaced with intermediate large valves; Piper 285 cam, now replaced with TVR/Kent 885). The 72 mm is good for 2-3 bhp at best, the real gain is in the better airflow distribution over the trumpets with the carbon multithrottle options.

On a 270 bhp John Eales 4.6 (10:1 cr, 218 cam, intermediate large valves, GEMS) the twin plenum gave an additional 12 bhp on his engine dyno, which surprised Tim a bit at the time as he previously thought the bhp gains were only significant on 300 bhp+ engines. Subsequent tests gave another 2 bhp or so for the triple at a similar hp level; the triple however does improve throttle response further.

The combination of ACT exhaust manifolds, twin plenum with carbon trumpets underneath and a bigger Bosch AFM gave about 24 bhp compared to blended base and 72 mm throttle on my car, on the same dyno with the same correction factors applied to the previous run (long time ago). The real impact of the airflow mods only came to light after going to the 123tune mapped ignition, which gave another 26 hp - methinks the 120,000 mile old Lucas distributor might have been fairly worn at this point with significant timing variations as a result...

Many thanks, an Interesting read.

[motul1974]

Mr Haribo said:

I have a 4.6L on a triple, and yes a double will be fine even a single with a bigger butterfly will do ! Changing from a Mark Adams Ecu to a triple and a Emerald ecu got me 15bhp on the same dyno !
But the way it spins up..... love it I’m keeping the triple

Yours is the JE alloy one, if I remember correctly?