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3" vs 4" exhaust

Discussion in 'General 4x4 Discussion' started by Crashtastic, Jul 4, 2018.

  1. Crashtastic

    Crashtastic Member

    So, the time has come to get rid of the poxxy stock exhaust on my VDJ79 landcruiser.

    I was looking at buying the manta 3" twin exit system (with cat), as they sound dead sexy and I've heard good things.

    I also popped into the local exhaust shop who have had quite a few VDJs come through, and they quoted me a bit less to fabricate and fit an identical system than to buy the Manta system. Now I had the dangerous idea, why not see what they'll charge to do the twin exit system in 4" instead?

    For those who have experiece, how much louder is a 4" than a 3"? I'm hoping that a 4" with give a deeper note, but I'd still like a system that's not obnoxiousy loud. Secondly, do you think a 4" is worth it for an extra hundred bucks or so with a high flow cat, or does the cat make the extra inch redundant.

  2. billolga

    billolga 4x4 Earth Contributer

    It depends if it's mines a bigger than yours thing I guess.
  3. mac_man_luke

    mac_man_luke Well-Known Member

    4" is nice on the cruisers but really only is of any benefit if your going to put a bigger turbo on.
    Makes it a lot more complex as it needs a unique dump pipe fabricated - normally a 5" dump that bolts on from the inside and then reduced to 4"
    3" should be fine especially if your going twin system.
    Albynsw likes this.
  4. Pubski

    Pubski Member

    Twin 4 inch system. I made a single 4 inch that support 1000hp motor i dont see why you need such a big exhaust personally twin 3 inch it a bit overkill
  5. 2luxes

    2luxes Well-Known Member

  6. discomatt

    discomatt Well-Known Member

    Have you heard most of the 70 series getting around these days?
    Most are so loud you would struggle to spend 8 hours behind the wheel without needing shares in Panadol :eek:
    Spooner and LCV8VICTORIA like this.
  7. CaptainBanana

    CaptainBanana Active Member

    Larger diameter doesn't usually mean deeper sounding, in most cases it's either airy, farty, tinny or otherwise shitty sounding unless of course you're talking a large displacement engine or one moving tonnes of air. Also as the exhaust travels the length of the pipe it cools and occupies less space meaning you need nowhere near 4 inch for your cruiser... Not to knock what's probably an OK motor but it's hardly making 500hp/1000ft of Tourque is it.

    LCV8VICTORIA Active Member

    I have a 3” pipe high flow cat and resanator to make it quite at 100km but still slap when giving it the berries on the tracks
    Straight pipe drones heaps when cruising and will annoy the crap out of you lol well It annoyed me haha
  9. monk2

    monk2 Active Member

    I take it that it is the V8 diesel engine I would be running a 3 inch single system from turbo back replacing every thing with high flow items cat the lot you will not need a 4 inch system unless you going to work over the diesel change the turbo and rev the living hell out of it 3 inch will be fine
  10. Deccas

    Deccas Active Member

    i just bought a 3" high flow cat to dump pipe on my 79, so when i fit it this week ill tell you how it is
  11. Crashtastic

    Crashtastic Member

    Thanks all. I went the 3" into twin exit with the high flow cat. Sounds mint when you give it the boot and subtle enough just cruising around town now to piss everyone off (or attract attention!). Doesn't drone really at all, and boost comes on a lot faster and stronger (looking at MAP readouts).

    I dunno if it's a positive bias, but I put in a stereo about a week after having the system which meant disconnecting the battery for a few hours. I reckon that the ECU must have reset because she drives alot better since then, boost seems to come on even better and the throttle response seems a bit better too

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