Bingy Posted October 26, 2012 Share Posted October 26, 2012 So, now that i managed to fit the trigger wheel,lol im now onto the exhaust. I stupidly bought a full stainless system for the earlier 3.9 v8 i was going to put in including the 4-1 headers. Since reading up more, for more torque a 4-2-1 header system is preferred like the original headers. Now that i have changed to a 4.6 v8 i have got some original stainless headers, together with the downpipes all the way back to the y connection. but the exhaust for the 4.6 has catalytic converters on. So the next conundrum is Would i be better using the full exhaust kit, (it is supposed to be for a 3.9 - 5.0l v8) with the 4-1 headers (no cats) Would i be better using the 4.6 headers and downpipes together with the cats? with the 4-2-1 headers? Do i use the 4.6 headers and downpipes and cut the pipes before the cats and re weld back together? with the 4-2-1 headers? Do i use the 4.6 headers and downpipes and then join to the exhaust kit? Cheers chaps Just wait til i start the wiring, lol Quote Link to comment Share on other sites More sharing options...
zoltan Posted October 26, 2012 Share Posted October 26, 2012 The difference between a 4 into 1 and a 4-2-1 will be where the bulk of the torque is produced, 4 into 1 tends to produce it's peak torque at higher rpm and 4-2-1 is better for midrange torque That said much will depend on how well the relative exhausts have been designed in terms of achieving a balance between the ideal tuned lengths of the pipes and the constraints of fitting the pipe runs into the space available under the bonnet. Also, size isn't everything In an ideal world you would aim to run each option on the dyno to make your choice. In this world it sounds as if your third option would give best spread of torque Quote Link to comment Share on other sites More sharing options...
Bingy Posted October 27, 2012 Author Share Posted October 27, 2012 Cheers, Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 29, 2012 Share Posted October 29, 2012 Depends how seriously you're taking it all really - unless you're chasing the last few % then it doesn't make much difference what you do with your exhaust compared to all the other sub-otimal stuff going on in the average Land Rover. Cats - if you don't need 'em for MOT then I wouldn't bother fitting 'em. Quote Link to comment Share on other sites More sharing options...
Bingy Posted October 29, 2012 Author Share Posted October 29, 2012 I will just put the kit on and see how it performs, rather than cutting up a brand new stainless exhaust set. If it doesnt work well, then i will cut it up. Cats - if you don't need 'em for MOT then I wouldn't bother fitting 'em. Fridge, how do i know if i need the cats or not? I thought that megasquirt tuned the engine enough to pass the mot emissions? Quote Link to comment Share on other sites More sharing options...
zoltan Posted October 29, 2012 Share Posted October 29, 2012 What year is the vehicle? If it originally left the factory with cats fitted you will need them but there used to be a caveat that if the engine number doesn't correspond with the DVLA database then a cat test couldn't be performed. I don't know if this is still the case. I expect someone with more modern MOT knowledge can/will confirm or dispute this Megasquirt (or any other management system) alone cannot achieve the low emissions of a cat equipped vehicle so you'd struggle to meet cat limits without cats fitted Quote Link to comment Share on other sites More sharing options...
Bingy Posted October 29, 2012 Author Share Posted October 29, 2012 What year is the vehicle? If it originally left the factory with cats fitted you will need them but there used to be a caveat that if the engine number doesn't correspond with the DVLA database then a cat test couldn't be performed. I don't know if this is still the case. I expect someone with more modern MOT knowledge can/will confirm or dispute this Megasquirt (or any other management system) alone cannot achieve the low emissions of a cat equipped vehicle so you'd struggle to meet cat limits without cats fitted The vehicle year is a 1988 (F), BUT is registered as a 200TD at the moment. Once finished it will have a 4.6 in. The engine number is a new one specifically put on by the company who built the engine for me Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted October 29, 2012 Share Posted October 29, 2012 It won't need cats then. As Fridge says, you shouldn't be worrying to the nth degree about 4-1 or 4-2-1, it will be very, very little difference in all honesty, get it fitted up and drive the thing Quote Link to comment Share on other sites More sharing options...
Bingy Posted October 29, 2012 Author Share Posted October 29, 2012 It won't need cats then. get it fitted up and drive the thing Just needs a LITTLE more work on it Quote Link to comment Share on other sites More sharing options...
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