4722 replies to this topic

[siztenboots]

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

[Nev]

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

 

Thanks, seems his bypass gives him 100 HP back.

[leevx2.2]

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

very nice exhaust why can't someone make them that good for vx's 

[CHILL Gone DUTCH]

Does this exhaust bring each bank of (3) in from either side to cancel each other out ?

[Nev]

 

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

very nice exhaust why can't someone make them that good for vx's 

 

 

I expect because nobody would pay £8,400 for one: http://www.design911...pc&utm_content=

Edited by Nev, 04 January 2017 - 04:42 PM.

[leevx2.2]

 

 

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

very nice exhaust why can't someone make them that good for vx's 

 

 

I expect because nobody would pay £8,400 for one: http://www.design911...pc&utm_content=

 

Is that all       

[Nev]

 

 

 

nice exhaust thread with some nice measurement data for you, http://rennlist.com/...2-nip-tuck.html

very nice exhaust why can't someone make them that good for vx's 

 

 

I expect because nobody would pay £8,400 for one: http://www.design911...pc&utm_content=

 

Is that all       

 

 

It's ok though, I can make you one for a £5er and a pack of smarties.  

Edited by Nev, 04 January 2017 - 04:57 PM.

[Nev]

I've finally bought all the extra bits of metal I need to build a new silencer. It includes this Chinese 89mm boost activated flapper valve. I was in 2 minds as to whether it would be worthwhile as it has pros and cons:

 

PROS

1. It looks like it has a good seal on the butterfly flap.

2. It looks better made than what I could fabricate, particularly the sleeved spindle.

3. If the actuator trigger doesn't work out, I can always replace it with a spring system to make it automatically flow balanced.

 

CONS

1. It will take anything up to 2 months to arrive (assuming it even does).

2. The actuator won't open until 1 Bar of boost. As I generally drive with only 0.6 Bar of boost, this will likely need tinkering with or replacing with a low spring one.

3. The bypass will only work when the engine makes boost (so only when accelerating). I would probably prefer a flow load balancing system really, but it's a pain to make.

 

This is the new design (2 length variants at the moment). 1 quiet route and 1 bypass route. I might try and squeeze in 2 * 3" exit pipes in if space allows. The design has an new/extra expansion void (bottom right corner) with pipes leading out. This should mean that low RPM will be even quieter than I have at the moment.

 

My main worry is that when the butterfly valve opens that the whole thing will become too noisy (as the the exhaust will change flow to primarily become a simple 2 section absorptive design).

 

The trump card of this design though is that I can control if/when the butterfly valve opens, thus controlling the flow direction and hence both the noise and back pressure. Thus it will be configurable after I've built it. So on an early morning run in the middle of nowhere I can force the butterfly valve open for max noise +power, yet for the neighbours I can have it fully closed for max quietness.

 

 

 

 

 

 

 

 

Edited by Nev, 07 January 2017 - 10:12 AM.

[ditonics]

Love your build thread Nev. Looking forward to hearing the change over of the system when you have it working. What sort of HP and torque are you getting?

[Nev]

Love your build thread Nev. Looking forward to hearing the change over of the system when you have it working. What sort of HP and torque are you getting?

 

Thanks, I have a feeling (complete guesswork) that my power is down by about 50 to 80 HP with the current exhaust, so maybe only getting about 450 HP and 360 ft/lb at the moment.

 

I am hoping this new one will yield the old 520 HP and 430 ft/lb that I used to have. In fact, if it works well I intend to get a remap and use more boost as there were a few times last year when the car didn't have enough oomph. With 30 PSI of boost I know it easily makes 550 HP and 500 ft/lb, perhaps a bit more.

Edited by Nev, 07 January 2017 - 10:52 AM.

[Nev]

While I wait for the Chinese boost activated flapper valve to arrive in the post, I decided to mock up my 180 degree bend with the home made flapper valve. Really I just wanted to sanity check it would work as intended, so I only tacked it up with a few welds and with the spring location loosely located.

 

Overall it looks good to me, with adjust ability of back pressure controlled by raising or lowering the spring on the spindle arm. It is such a simple and elegant solution I really like it. It seems to rotate easily enough without catching.

 

Importantly, the trigger function of this will be different to the Chinese actuator flapper valve:

 

The Chinese flapper valve will trigger only when boosting (ie accelerating). It will also be more binary (open or closed) in function.

My DIY flapper valve will trigger at a set back pressure (regardless of whether I am boosting or not) so will give a smoother linear response based on flow back pressure (regardless of whether I am accelerating (ie boosting) or not).

 

At the moment I prefer my solution for a couple of reasons, but once I have the Chinese effort in my hand I will be able to fully evaluate which seems better and then utilise the best one.

 

Edited by Nev, 09 January 2017 - 02:53 PM.

[Nev]

Took the prototype flapper valve round to Josh's today as we were working on his Esprit. He liked it so much hat he wants to stick one in his own Tubular exhaust.

 

I'm still waiting on the Chinese flapper to turn up in the post...

Edited by Nev, 12 January 2017 - 08:00 PM.

[ditonics]

Chinese flapper; that conjures up a strange image. Can't wait to hear a sound bite.

[oakmere]

I think this is the right way to go. More power and the exhaust will last longer before repacking win win 👍

[Nev]

I think this is the right way to go. More power and the exhaust will last longer before repacking win win 👍

 

I'm hoping the next silencer will be quiet enough without any packing, we shall see if I am being too optimistic...

 

Considering the speed the Chinese post works, I might not even start building it until March

 

It amazes me that a country whos GDP is critically dependant on exports can't mange to deliver small parcels in under 6 weeks. *cry*

 

Edited by Nev, 13 January 2017 - 10:29 PM.

[stu8v]

The stuff I've ordered has always been delivered super quick tbh...

[The Batman]

It all depends on how tight you are with paying for postage

[Nev]

My eBay item didn't give me a choice, donkey delivery was the only option.

Edited by Nev, 14 January 2017 - 12:16 AM.

[oakmere]

I also ordered something by mistake from HK on eBay and was told delivery end Jan to start of March but got it yesterday. So you never know!

[Nev]

I used to sit next to a kid in school who's brother used to service Polaris missiles, he reckoned less than half would have ever got to their destination if fired due to complexity.   IT these days is much the same, over complex without enough emphasis on robustness and being fit for purpose

 

 

Got reminded of the above today when I heard the news about the Trident test.

 

Sheesh, each missile is £nnn million and still doesn't work. All paid for by us the tax payer. I'm in favour of a nuclear deterrent, but it has to bloody work!  

Edited by Nev, 23 January 2017 - 10:42 AM.