Quiet exhaust for circa 1000hp

[Noz]

8 hours ago, Mgrene said:

Is it this one you are running with your 4" exhaust?

 

That must be the one I'm using then. I sourced it from UK years and years ago. 

I'd be surprised if the reduction in diameter for that short distance would do any reduction in flow.

As a comparison for flow I get 603hp at 1.5 bar on a 62mm. On an NA engine without head upgrades. So I know its got good flow capability.

Having a 4.5" exhaust may or may not make a difference. There's only so much benefit at that sort of power really.

Edited February 18, 2021 by Noz (see edit history)

[Mgrene]

7 hours ago, Noz said:

That must be the one I'm using then. I sourced it from UK years and years ago. 

I'd be surprised if the reduction in diameter for that short distance would do any reduction in flow.

As a comparison for flow I get 603hp at 1.5 bar on a 62mm. On an NA engine without head upgrades. So I know its got good flow capability.

Having a 4.5" exhaust may or may not make a difference. There's only so much benefit at that sort of power really.

Maybe I was not clear.

the back pressure I was talking about, was only when the valve is closed and especially when cruising on highway and I decide to close the valve to reduce noise, wheter that would be any good for the engine.

I don’t doubt that the inner diameter is large enough to flow the sort of power I’m runing and will in that sense not create any restrictions. But for easier installation it would have been nice that it matches the inner diameter of my exhaust system

once I have sold my Varex muffler, I will buy this one

Edited February 19, 2021 by Mgrene (see edit history)

[Burna]

11 hours ago, Mgrene said:

Maybe I was not clear.

the back pressure I was talking about, was only when the valve is closed and especially when cruising on highway and I decide to close the valve to reduce noise, wheter that would be any good for the engine.

I don’t doubt that the inner diameter is large enough to flow the sort of power I’m runing and will in that sense not create any restrictions. But for easier installation it would have been nice that it matches the inner diameter of my exhaust system

once I have sold my Varex muffler, I will buy this one

I think perhaps you're misunderstanding how these work, or I am, all I can comment on is how I have seen them fitted and used in the past on track Supras. To make it quieter you fit an exhaust system that is quiet, with silencer boxes etc... which will be restrictive. You then divert a pipe from the exhaust system just before all the silencer boxes that exits to the street, and fit the butterfly valve in that pipe. So when the valve is closed your exhaust gases will all pass through the silenced exhaust system and be restricted, when you want to have fun and use the full potential of the car you open the valve and the exhaust gases will be allowed to flow freely through the pipe that exits straight to the road. Of course the only downside is that you wont be using the resonator can on your exhaust system to make it sound pleasant/good.

The other way to do it, and the ideal way, would be to add along side your existing exhaust system a set of silencer boxes. You have these welded in to pick up from part of your exhaust system in your second de-cat stage, and then re-enter into your exhaust system just before your rear resonator can. You fit the butterfly valve in your main straight through exhaust just after it the diverts into your silenced system, so when the valve is closed the exhaust gases will be forced through all the silencer boxes. When the valve is open it will free flow straight through your existing exhaust and rear resonator can.

The down side is I've not yet seen one of these valves cope with the heat of a single Supra, they always fail. 

Edited February 19, 2021 by Burna (see edit history)

[baldy]

VMK18-400 | XForce USA

For some reason my pc at work won't copy links, but Google the above

Edited February 19, 2021 by baldy (see edit history)

[mattdavies]

1 hour ago, Burna said:

....... The down side is I've not yet seen one of these valves cope with the heat of a single Supra, they always fail. 

I saw on piston heads a guy bought an OEM backbox off another car with the valves in and repurposed those valves for his exhaust, this may be something to look into for those wanting to put valves in their exhuast system. I am guessing these OEM valves will outlast the eBay valves that are available. 

I get that the OEM valves may not be that big but they might be enough to gain some additional flow. for example a with a 2" cutout running in parrell with your 3" exhaust would have an combined cross sectional area slightly larger then a 3.5" exhaust. a 2.5" cutout with your 3" exhaust would have an cobined cross sectional area slighly smaller then a 4" exhaust 

[Burna]

I think it's all getting a bit over complicated tbh. It's a 4" exhaust on a single turbo, it's never going to be quiet lol As Luc said, just pop the baffle in when it's first started and drive off boost until your a mile down the road and take it out, simples.

[Style]

There's not really enough room under a Supra for a complicated, twin exhaust system with silencers in one etc. GTR's on the other hand seem to have some room at the back for a some trickery and you can build quite a nice setup. So yeah, what Burna said!

[mattdavies]

the stock system has 4 silencers in a 1-2-1 sort of format, you could easily fit another silencer in the spare slot that isnt filled by most aftermarket systems. 

[Noz]

Removing a baffle is a pain in the ass. Hopping in and out your car. No one wants to deal with that.

Mufflers don't reduce sound by restricting flow. Look them up for a good explanation but they do disturb the flow therefore causing loss in turbulence, reduction in turbulence would of cause change the flow rate and capability.

These aren't bypass valves. As bypass valves usually come with the bypass Y pipe.

I have a single pipe with the valve inline with it. I dont have any divert boxes or any other pipe magic. Simply in line with my exhaust.

I've never had an issue. I can drive through the rev range so cruising speed is well below its capability.

The turbo spools but the boost is so low it feels like an NA.

Its only used for low driving in built up areas and partially shut on the motorway.

I agree there will be an increase in backpressure but the engine feels smooth and the valve isn't ever going to stall it.

There must be a line where the engine can't run properly I'm sure. But I've had the valve for over 7 years. 

Never had an issue (on my 3rd engine and 5th head LOL joking of course, but triggers broom comes to mind hahahaah)

Edited February 19, 2021 by Noz (see edit history)

[CBR]

 

 

[Swampy442]

6 hours ago, Style said:

There's not really enough room under a Supra for a complicated, twin exhaust system with silencers in one etc. GTR's on the other hand seem to have some room at the back for a some trickery and you can build quite a nice setup. So yeah, what Burna said!

Of course it does, it shares a Soarer/Aristo floor pan, theres plenty of space to fit a big silencer on the drivers side

[mharvey]

12 hours ago, baldy said:

VMK18-400 | XForce USA

For some reason my pc at work won't copy links, but Google the above

Do you use one yourself? Their advert one on a Scooby sounds impressive. 

I like the idea of a 4in version that would massively reduce the noise of my car on the way to/from the house

[Mgrene]

7 hours ago, Noz said:

Removing a baffle is a pain in the ass. Hopping in and out your car. No one wants to deal with that.

Mufflers don't reduce sound by restricting flow. Look them up for a good explanation but they do disturb the flow therefore causing loss in turbulence, reduction in turbulence would of cause change the flow rate and capability.

These aren't bypass valves. As bypass valves usually come with the bypass Y pipe.

I have a single pipe with the valve inline with it. I dont have any divert boxes or any other pipe magic. Simply in line with my exhaust.

I've never had an issue. I can drive through the rev range so cruising speed is well below its capability.

The turbo spools but the boost is so low it feels like an NA.

Its only used for low driving in built up areas and partially shut on the motorway.

I agree there will be an increase in backpressure but the engine feels smooth and the valve isn't ever going to stall it.

There must be a line where the engine can't run properly I'm sure. But I've had the valve for over 7 years. 

Never had an issue (on my 3rd engine and 5th head LOL joking of course, but triggers broom comes to mind hahahaah)

And that is exactly how I want to do it as well, so nice to hear that it works.

I know the optimal (and most probably the healthiest setup) is to do a bypass solution, but that will require soo much more than just welding in a valve and for that reason, I’m out.

[Mike2JZ]

I've got a 4'' system on mine and even with twin box whifbitz 4'' its still loud and drony. 

Recently I did some logging with a bung stuck in backbox whilst using an exhaust backpressure sensor mounted in my exhaust manifold. 

To make a long story short. 

Driving off boost, there was no noticable change in backpressure whilst cruising, idling etc. So you have nothing to worry about there. There isn't enough exhaust flow to warrant any special attention under these conditions. 

As expected, on boost however the backpressure went through the roof. Along the lines of trying to blow through a very small straw.  So not advisable to boost hard with a bung in the back as you are choking the engine. Also sidenote, don't use antilag with a bung in the back. Managed to break the bolts holding my bung in and blow it off into a nearby field whilst driving along lol. Wish I had the footage from that. 

[Noz]

Truly insane anti lagging with the bung in lol.  I mean, what the hell.

Take it you went and picked it up after??

Do you run a tube off the exhaust for the sensor mate, how close do you have the pressure sensor to the pipework.

[Mike2JZ]

11 minutes ago, Noz said:

Truly insane anti lagging with the bung in lol.  I mean, what the hell.

Take it you went and picked it up after??

Do you run a tube off the exhaust for the sensor mate, how close do you have the pressure sensor to the pipework.

All in the name of science and data lol! 

I looked for it, but gone with the wind. 

Yes I have a copper tube that runs off the manifold collector, coils around itself a few times before going into a T1 Race EMAP Damper which a 5 bar map sensor is screwed into. Probably between 30cm-45cm of copper tubing. Works really well. 

[Noz]

Lucky you didn't kill an animal!!

Great idea with the coils, I've not seen copper used before to be fair. What kind of pressures do you see in the exhaust? I read somewhere the 6870 isn't limited on it's exhaust flow usually, as in the exhaust housing flows quite well or maybe it wasn't the turbo's limiting factor. I'm only repeating what I read somewhere, so I'm just guessing technical information here.

You've a 1.0 AR as well if I remember.

[baldy]

18 hours ago, mharvey said:

Do you use one yourself? Their advert one on a Scooby sounds impressive. 

I like the idea of a 4in version that would massively reduce the noise of my car on the way to/from the house

I dont, but im seriuosly thinking about giving it a go

[Mike2JZ]

2 hours ago, Noz said:

Lucky you didn't kill an animal!!

Great idea with the coils, I've not seen copper used before to be fair. What kind of pressures do you see in the exhaust? I read somewhere the 6870 isn't limited on it's exhaust flow usually, as in the exhaust housing flows quite well or maybe it wasn't the turbo's limiting factor. I'm only repeating what I read somewhere, so I'm just guessing technical information here.

You've a 1.0 AR as well if I remember.

Copper is typically used for EMAP set ups as its cheap, easy to manipulate the shape, disapates heat decently and easy to flare the ends for various fittings. Although I have seen some people run braided hoses for this kind of thing as well.

On my setup I typically have a MAP/EMAP ratio of less than 1. So exhaust pressure is lower than inlet manifold pressure, even at high boost whilst under 7000rpm. After 7000rpm my exhaust pressure starts creeping higher than inlet pressure. I don't rev my engine beyond 7500ish as the heads flow is done (1.5jz life), so exhaust pressure isnt really an issue for me which is nice as it let me identify other restrictions with my setup. 

However if you look at the above graph on a 2J stroker 6870 with all the bells and whistles comparing 1.8bar versus ~2.8 bar (100% wastegate duty). Then you can notice two highlighted areas. 

From everything I've seen with the 6870, the green area is it's most efficient point. In this area your MAP/EMAP ratio is less than 1, and the compressor seems to be working very efficiently. So the potential gains in this area are huge.

If you command more boost here it will make it very easily, I've seen it on multiple occasions making north of 900ft.lbs of torque here with 2.4bar+. Obviously in the real world sometimes there are restrictions with traction, mechanical reliability, engine breathing/restrictions etc etc, so normally the boost is regulated in a way that you don't get hit with such a huge wack of torque. But the above image shows the potential gains in that area and how happy the turbo is to make power. 

Now looking at the yellow area. You can see on the red run, that power is nice and linear and torque hardly falls by redline. 1.8 bar on this turbo is efficient for the compressor and exhaust pressure is not a massive issue. Once you start turning the boost higher notice how the torque drops off significantly faster, and the power also drops earlier in the powerband.

This is a good example where the turbo is being asked to work as hard as possible and physically it reaches a level where it runs beyond its compressor efficiency and the backpressure from the extra exhaust flow causes it drop boost as the turbine wheel and turbine housing can only flow so much before bottle necking. By redline, even though the wastegate duty is still 100%, the inlet manifold pressure is back down to ~2 bar from the amount of restriction it is working against. So although it makes more power and torque, from a reliability standpoint the turbo will have a much harder life being run like this hard compared to being run at 1.8 bar. 

All SRD builds are running 1.0 A/R's on 6870. Seems to be the best fit for the way the 2J wants to breathe whilst having a broad powerband. Running a smaller A/R will just become a restriction on the high end quicker than what you can see in the example above. 

[Noz]

Isn't the higher boost level just highlighting the issuing whereas the lower boost setting isn't a delayed reaction its just not flowing enough go show anything.

I'm going to start calling you Dr Mike soon. You love the technical shit and I have to admit it's always great bouncing off ideas and getting your guidance.

Have to agree on the AR. I've not seen any improvement with spook using a lower housing.

[Swampy442]

Science bitch!

 

[Mike2JZ]

27 minutes ago, Noz said:

Isn't the higher boost level just highlighting the issuing whereas the lower boost setting isn't a delayed reaction its just not flowing enough go show anything.

I'm going to start calling you Dr Mike soon. You love the technical shit and I have to admit it's always great bouncing off ideas and getting your guidance.

Have to agree on the AR. I've not seen any improvement with spook using a lower housing.

Correct, not flowing enough to cause a restriction at "lower" boost (though still flows enough to make rediculous power). Argueably better for longevity of all components as well. 

Thanks, everyday is a school day for me but always working towards trying to understand more and help guide other people, not enough good info out there sometimes. 

Turbine housing A/R is interesting. Seems counter intuitive, but sometimes bigger is better. 

 

Edited February 20, 2021 by Mike2JZ (see edit history)

[Luxluc]

Great info Mike

[bayside_supra]

Update on this, just went for a baffle in the end. Really quiet now. Bit tight to get in and out so will try and sand it down a bit. Does the job though 

 

 

[Luxluc]

I told you ..