Skyline Owners Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
1,673 Posts
Discussion Starter #1 (Edited)
Some days are worse than others for me, on a good day I can see the horizon, on a bad day I can't see myself in a mirror, tomorrow I shall try the following alternative..

In my previous how to and associated posts for modding the Nissan and similar active dual mode exhaust systems, I struggled with one part of it. That aspect was how to include the original setup as an option with a simple switch, and I missed a very obvious alternative.

I initially established that the closure flap was actuated by first applying a 12v + feed to open it, then a 12v - feed to close it. I therefore set mine up to switch between the two, by soldering a simple crossover on the rear of the switch, allowing me to select between open or closed. (+ or - v)

This covered the legal requirements for MOT or roadside tests etc, but I wanted to add the original operating mode back into the equasion if possible.(opens at 4100 under acceleration)

I'm hoping that all that's necessary to get the best of all worlds is to use the original 2 wire operating connections for one side of the switch and an opposite polarity feed to the other! Accordingly I have redrawn the diagram and included below, hopefully my thoughts are on track!


Exhaust Tuning - Free mod How To

Niallyc raised a query here re having quiet exhaust when required but beasty when required, which has been discussed on that thread. I outlined a method to give the best of both worlds, now here's a how to with diagrams to make it easy. Level of difficulty - with this how to, Novice, time to complete - 2 hours, cost, £5 approx.

The exhaust system on many of our Skylines already has the ability to open a "straight through" path at a predetermined rpm, that's the normal Nissan setup, standard setting is 4100 rpm under acceleration. But that's a waste of potential, which is why I've done the mod, this way I decide when I want straight through performance and when I don't.

The dual mode active muffler fitted to numerous Skyline's has a novel feature, at 4100 RPM it opens a valve in one of the two tailpipes, providing a straight through exhaust path for a short burst during heavy acceleration.

This mod below allows those with the Nissan twin output dual mode muffler (or similar systems) to make considerable performance and sound gains virtually for free, whilst being able to stay within the law. (as and when required by flicking the switch) The mod allows you to manually select between straight through and normal exhaust modes, so no problems with roadside VOSA tests and MOT's etc. Hopefully this second wiring option will also allow standard flap operation rather than just open or closed.

Now that MOT's are computerised and VOSA has been allocated the funding for increased roadside tests, this mod could be a godsend, whichever method works best.

The mod shows how to fit a switch circuit, allowing manual selection of the straight through and normal paths. With the switch fitted to open & close the flap in the exhaust on demand, the Nissan dual mode muffler provides two exhausts for the price of none.

Look for the "choke flap" inside the right hand tailpipe on these twin pipe back boxes. The flap is normally closed in the straight through right hand pipe, which does not go through the "silencer" section of the back box. At street speeds exhaust flow is forced by the closed flap in the straight through tailpipe to go via the "silencer" section, but at around 4100 rpm under acceleration the flap opens, creating a straight through system path for a short period.

The link below shows a similar system:

http://www.skylineowners.com/forum/a...9&d=1182330502

The actuator on the Nissan system is tucked behind the boot trim on the passenger side, though control is excercised by the engine management systems. It certainly does change the exhaust note, quite a lot, but in it's normal setup only for short bursts during heavyish acceleration.

The actuator requires 12v + to close and 12v - to open, for my initial tests I wedged the flap in the "straight through" tailpipe section wide open, beautiful, so decided to make it a permanent feature. To this end I fitted a switch on the central console, I used the space provided for coin storage.

I can now run with a legit system or a straight through system at the flick of a switch, how cool is that?

Requirements: a few metres of 4 core cable, a switch as per my diagram included below, an inline fuse & holder and a soldering iron.

This mod provides two totally different exhaust system results, one for shopping and one for bopping..the straight through mode will not rip your guts out with base pulses but it's as much as I'd ever want and toooo much for the wife! Beauty is I can be legal or straight through at the flick of a switch!

At the end of the day this mod costs a few pounds and an hour or so's work, unbelieveable value, you really have to do this if you have the dual mode muffler, and if you haven't then get one! There is not a better way to spend a few hours and a few pounds this weekend, this time you can keep your promise to the wife, it really will only cost a few pounds and take an hour or so!

I have a few tips to make it quicker..

To run the cables from the actuator to the centre console where I mounted my switch, the following saves time.

Remove the bolt from the front of the rear seat squab on passenger side. Now find something flexible but robust to use as a cable pull, I used a length of 1/4" plastic tube from a nos system. Feed this from the boot at the left side of the battery, there's a gap through to the rear seat squab. By pushing it through the available space it will go under the seat on the passenger side, you will then be able to pull it through form inside the rear of the car. Tape the wires (x 4 core 0.5A is ok) to the tube and pull through to front of rear seat squab. Now feed the tube with wire attached under the carpet and come up in the void under the centre console.

You are now ready for the install, the rest of which is simple if you follow the diagram below.

The first thing you need is the twin tailpipe dual mode backbox, look up the righthand tailpipe of the two, if it's the right type for the mod it will have a "choke flap" type fitting in there. The flap is operated by an actuator behind the passenger side boot trim panel, which in turn is controlled by the engine management systems.

To avoid confusion, in the Nissan system for which I've discussed the mod, the right hand pipe with the flap is truly "straight through" in the true sense of the description, though of course only with the flap open. So when modded with the switch it can be left that way as long as you like, and switched back for tests etc., thus avoiding any and all risks.

The thing I like about this mod apart from the exhaust note improvement, is that it has allowed me to be "totally legal", but at the flick of a switch I can get down and dirty with a straight through system!

In synopsis, I've removed the decat pipe and replaced with a legal sports cat, which whilst it is heaps better than the standard cat does not quite provide the same gains as the decat pipe did. The mod I've now done to the Nissan dual mode back box IMHO restores everything to the same power levels as with the decat pipe in place. The additional benefits are that the exhaust note is hugely improved and no need to change parts around for MOT, plus no risk at roadside VOSA tests, which are set to become a feature of the motorists life in the near future apparently.

Have fun, you will afterwards!

OK, I TRIED THE OTHER OPTION WITH THE ORIGINAL SIGNAL WIRES, NO LUCK, IT DID NOT WORK CORRECTLY. SO, IT'S BACK TO OPTION ONE! THERE'S OBVIOUSLY MORE GOING ON WITH THE ORIGINAL SIGNAL WIRES THAN I'M SEEING, SO SWITCHING BETWEEN THE TWO MODES IS AS GOOD AS IT GETS FOR NOW..

I'll leave the second diagram in place on this post, in the hope that having sown the seed and achieved my initial ambitions someone with more knowledge may improve on it by finding a way to tweak it. I'm happy with on and off but would like to have the full original operation plus the straight through, anyone?

Aitch
 

Attachments

·
Registered
Joined
·
1,673 Posts
Discussion Starter #3
Well, so far I've not been able to find a way to have the original mode, (flap closed but opens at 4100 rpm) or open straight through mode via the switch. So I've modded the diagram accordingly to show the simple switch mod which works, exhaust is either straight through or standard, but the flap won't open at 4100 rpm, it's either always closed or always open, fine for me but I will try again to improve it.



Aitch
 

Attachments

1 - 3 of 3 Posts
Top