Lithium

I don't think the path is necessarily significantly more torturous than your typical I4 or I6 single turbo exhaust manifold, it may seem exaggerated by the length of the things. The firing order is still evenly spaced (funnily enough) so equal length/timed headers are very possible, in fact the later ones run them factory so the pulse timing is not really a factor. Yeah agreed on the T1 damper, as I said earlier I was already raising my eyebrows at the claim- again the temperature isolation alone makes them worthwhile still even if the smoothing doesn't change the delay versus signal processing.

Not sure if we are on the same page or not regarding spool, I'm not quite clear on what you are saying.... but I think runner length means a LOT in regards to spool. Subarus should be able to spool like Evos and SR20s if runner length didn't matter. Alas we have immediately gone to the T1 dampener so can't comment on unsmoothed signals. I have to admit I chuckled at the "because electronic filtering causes a delay" thing but I am not certain that they would both be equivalent. Either way, the dampener also serves a purpose in regards to temperature isolation so worth using

Almost completely different kettle of fish compared to the low mounts on RBs tbh. Gets rid of a few of the huge fails about them haha

My comments relating to this I tried to make really clear was to do with transient/spool conditions, but even then the pressure is actually not as steady as it sounds like you'd expect - also if you want meaningful EMAP logging it is worthwhile running something like this: https://www.t1racedevelopment.com/product/gt1r-emap-kit/

Definitely on a similar wavelength. Look up "pulse converters" in regards to manifold design - especially in patent applications etc. There is some irony in the amount of effort that the aftermarket have put into making pretty tubular manifolds when OE manufacturers have highly qualified people with massive financial backing designing things, and decide they know better. There is naturally often space/reliability/other factors often at play, but then there is still more method behind the madness which is factoring performance into things as well than credit is given - at face value it may look too agricultural but actually the reasoning can be brilliant. There is quite a bit of data out there in SAE papers etc if you dig deep enough. Also, while pondering on this kind of thing - check out the AMS AlphaX exhaust manifolds which are used for >1900whp R35 GTRs....

Lol truth (aside maybe for the need for twin gates), however quite a few ideas being bandied about here apply to designing any manifold.

I am still thinking on it, but at this stage I think it's wildly overestimated in many situations UNLESS the lengths and/or the amount of pulses you are collecting can result in significant interference at the collector. When you have a group of 3cylinders merging into one on a 6cylinder you probably almost have to try to make that an issue. The path they follow and the merge itself are probably more significant factors, and it just ends up convenient that making a nice merge involves bringing the separate runners around from different directions and bringing it in evenly. Basically, I would put equal length as a pretty high priority if there was going to be any chance of high pressure pulse overlap at the collection point, otherwise I'd lax quite a fair bit and focus more on making the exhaust maintain as much energy as possible between the exhaust port and the turbine - which really is why we try and avoid interference at the collector in the first place.

Weeeee a big math session and I missed out!!! lol I assumed it was a wording issue as opposed to actually literally referring to mass flow past a given point - by definition a flow rate is past a certain point, having a pipe length involved in that wouldn't make sense unless as @GTSBoy was essentially covering... you are taking into account external factors which could influence the flow. I think friction/pressure ratios etc are beyond the cope of this conversation. Well I thought so before haha. I interpreted the statement (and I still feel that this is more relevant to this topic tbh) as effectively the rate that the manifold could be filled based on the current flow rate of the exhaust, I guess an equation to describe it could be something like "FillRate = volumetricflowrate / manifold volume". The reason I feel that is more relevant in this situation is that the gas flow through a manifold is extremely transient, when you are talking a 3>1 manifold on one of these things you are going to have a VERY inconsistent concentration of gas through the manifold so when a new EVO event happening you aren't going to displace gas at the turbo flange at the same rate the gas exits the exhaust port. I feel like this kind of thing is key to building drive pressure which will have a very significant effect on response - which I feel is one of the major things we are trying to optimise with this kind of thing.

So what benefit do you think there may be in having a lower flow rate? And yeah, very interesting stuff. Hoping we can try some stuff out with a design on a car we're doing, but the problem is there won't be any comparisons - it will just be part of an overall setup so hard to know what will contribute to what.

Hell yeah, honestly the amount of things I wish I had the time money and skill to put together and try because there are PLENTY of commonly accepted routes which I feel like could potentially be improved on - but would not push for people to try, or try myself without having more certainty. And just for trying to see what happened haha. Not just velocity, but essentially yeah - it does. This conversation could get very big very quickly, and no doubt the line between knowledge and opinion can start getting blurred but my 2c on that particular comment is that you shouldn't control velocity with runner length, the longer the runner the more time the exhaust has to shed energy. When "tuning" a steady flow rate through a pipe you usually adjust the diameter of the pipe, the length usually has more to do with synchronizing events and balancing up other factors involved with managing the bigger picture.

Hmmm not sure how the runner length would affect the turbocharger's efficient speed? Some of those other things I can see interacting with each other to a degree but compressor efficiency and optimal turbine speed I don't really see the runner length doing much. I very much understand choosing things which deliver sound etc that you dig, though... like realistically nothing is ever going to be perfect performance wise so if there are things which are going to make it more fun to you then by all means. Does my head in when people try to justify their preferences arguing until they are blue in the face when "I just like it this way" is a perfectly acceptable reason for choosing their own mods I am pretty sure I didn't say exclusively heat. A lot of it is theory but I feel there is quite a bit of reason to assume it has plausibility to it - not least that we have data already provided in this thread showing very carefully designed and nicely built manifolds with smooth curves and nice merges showing that it would be generous to say that it didn't gain... realistically that's probably charitable when I would guess in some instances like this if the "stock manifolds" result was the "after" in the comparison then it could have been arguably called a great success. Like anything it will come down to various variables, what the target is etc. If I had seen these headers before this test with what I've seen now (excluding this test) before this test was done and asked what would perform better overall I wouldn't be confident in much other than the tubular ones would likely sound cooler....

Always learning, looking for/analysing data and hearing other peoples experiences so really it could always change - but at this stage my view is that in this instance by increasing the distance from turbine to the valves you are sacrificing exhaust energy for no reason. There will be wasted heat which could be put into driving the turbine so more exhaust gas is required to generate the same amount of work... and also the greater runner volume means that it will take more time to build drive pressure. The fact that the bends and merges are cleaner probably offset some of the loss from that, but I am pretty convinced that the length of the runners would do more harm than good. The fact that you are collecting with 3 cylinders means that the exhaust pulses are lined up nicely anyway so the volume etc isn't needed to manage collisions, that length runner isn't needed to reduce turbulence so realistically the same idea COULD be applied with much shorter runners much more effectively. So yeah, avoiding the twins versus single debate - my comment can be applied to the sheer size of the manifolds versus what they need to do. If you were bent on twin manifolds and wanted them to perform well I'd lean more in the direction of something like this:

What are the odds this gets bumped - after not thinking about it for years I had a flash back to it last night while pondering some exhaust manifold design ideas we are looking at trying with one of the cars I help with, definitely finding it a bit less surprising that there wasn't any improvement with this after a few more years of learning stuff and looking at data for things :(. Still very cool, but

I've probably been involved with using a couple of tanks of gas just with these two and I live in a different country, so it's probably actually used a bit more than you'd guess looking on here haha. I forget it has a 4inch exhaust though, it's nuts how quiet it is considering

Jun 280deg man cams, petrol tuned to at least .7λ, half cage and Bee-R limiter?

Sweet, so all he needs now is VCam and it will be perfect?

So long as they have 1.45a/r housings

After years of struggling with twins and getting all the awesomeness of power and response with a well matched single why would he go back?

Ftfy

Hard to say without having had a look or go at it all and not knowing which ECU you are running etc, but it seems like there are a couple of things there which definitely are setting up to make it a bit of a challenge to make boost stable.... I'm not a huge fan of the internal wastegate EFRs personally, the 1.05a/r housing with external wastegate seems to be the way to go in most cases but as Welshy says, the 4-port actuator with a 1bar spring in it is definitely likely to make things trickier. You basically end up with much smaller duty cycle differences needed to have a solid impact on wastegate behaviour, and annoyingly a lot of ECUs with closed loop boost control don't factor in the dead time for the wastegate solenoid which means that closed loop corrections are counting the dead time as part of the effective pulse width... not usually an issue when you have a fairly wide duty cycle range for not a huge boost target range, but a bit more of an issue when the amount of the pulse needed to open the solenoid in itself could have a reasonable impact on boost if applied as part of the effective pulse width, if that makes sense? It's likely to make closed loop control have fits unless the ECU is able to provide the closed loop logic with just the effective pulse width to work with. We haven't actually tried it out yet, but one of the cars I work with that need a wide boost range we've plumbed up two 3-port solenoids and will use a PWM output on the Link ECU to regulate pressure to one side of the wastegate just using a table to effectively bump up the spring pressure based off boost target a bit, so we can use a .4 or .6 bar spring and be able to run sufficient boost to justify the setup with acceptable control.

Ahh yep, gotcha. Sounds like the 9280 is a couple hundred rpm or so laggier but the compressor map definitely paints a picture of a lot more flow. I think the 9180 compressor left a bit to be desired, so in that sense it may be a good upgrade depending on how much more power you want, and how much more lag you can live with. A shame results seem to take so long to filter through - most people who have run them so far have not shared anything, and the things shared so far fall well short of what the flow claims would suggest aside from the EFR8474 dyno result from a couple of years ago. Hopefully this changes eventually! Yusss!

G42 definitely has the exhaust flow to back it up - but a significant amount more lag too. Probably the way to go if you are looking for big power, but if you are looking for big power and response doing something a bit different a Xona Rotor 105-69S have the potential to be pretty epic when they get more available.

I might be in the right mood for this, but I love so much about this comment. 1000hp is such a random made up number, like I understand the bragging rights but seriously. If you get an EFR9280 on a strong RB28, and tune it until you hit around 117,000rpm shaft speed then who gives a crap what the dyno says - that is going to be a FAST car. Pick a bunch of parts which work well together and build, tune until it's sent and go forth and enjoy... that is the way to get a happiest result. The reality is those other numbers become academic in the end and sometimes result in people making compromises trying to hit a target which is academic and realistically you will make different power on different days or different situations depending on what various aspects of the tune kick in and compensate for whatever may be going on at the time, as you get ESPECIALLY on big high strain setups. A specific power number which can mean different things on different dynos and even days, or setups is not worth making compromises on imho.

Very good point.