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326 Posts Member #: 1323 Senior Member |
26th Feb, 2012 at 03:03:23pm
Just stumbled across this
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 8604 Posts Member #: 573 Formerly Axel Podland |
26th Feb, 2012 at 05:08:57pm
I've linked to that before. He's not wrong about the exhaust downstream of the turbo.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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 9258 Posts Member #: 123 Post Whore Betwix Harrogate and York |
26th Feb, 2012 at 05:24:38pm
I think that the official garrett website differs on the exhaust too. Thy state that backpressure is required to keep the oil in the turbo. Fastest 998 mini in the world? 13.05 1/4 mile 106mph
On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination, talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry. |
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326 Posts Member #: 1323 Senior Member |
26th Feb, 2012 at 06:10:26pm
On 26th Feb, 2012 Paul S said:
I've linked to that before. He's not wrong about the exhaust downstream of the turbo. Although I don't agree with him on the turbo manifold and neither does the official Garrett website: http://www.turbobygarrett.com/turbobygarre...ength_manifolds hadn't seen it before - where does he disagree with the official Garret manifold ? |
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8604 Posts Member #: 573 Formerly Axel Podland |
26th Feb, 2012 at 06:19:54pm
3rd paragraph contradicts what Garrett say. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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3594 Posts Member #: 655 Post Whore Northern Ireland |
26th Feb, 2012 at 08:04:06pm
Which bit are you classing as his third paragraph ?
9.85 @ 145mph
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326 Posts Member #: 1323 Senior Member |
26th Feb, 2012 at 08:58:06pm
On 26th Feb, 2012 Paul S said:
3rd paragraph contradicts what Garrett say. I don't see a contradiction ? I think what he is trying to get across is in an ideal situation tuned length etc should be used , but its not the most important aspect , trying to get/keep your exhaust gas velocity is the primary objective . This seems like sound advice to me ? |
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 2909 Posts Member #: 83 Post Whore Glasgow, Scotland |
26th Feb, 2012 at 11:35:15pm
just to throw this in as a thought, tuned legnths and so on are not going to work on your average turbo motor, as the turbine poses such a large restriction, getting gas to it and through it quickly is the priority. But what about a turbo where the turbine is very free flowing in the off boost region, talking peak torque >5000rpm. on such a setup short stumpy runners ought to strangle and tuned legnths could even help spool as they will increase VE in the off boost areas. Obviously i cannot back this up, but is my feeling that on an oversize turbine the engine becomes more like an NA to tune than your average turbocharged motor. Atleast i hope this is the case as its the route im going down turbo 16v k-series 11.9@118.9 :)
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3594 Posts Member #: 655 Post Whore Northern Ireland |
26th Feb, 2012 at 11:49:44pm
All an oversize turbine will do is make the car spool very late.
Edited by stevieturbo on 26th Feb, 2012. 9.85 @ 145mph
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2909 Posts Member #: 83 Post Whore Glasgow, Scotland |
27th Feb, 2012 at 12:27:11am
i just want to try it :) every time i went bigger on the turbine i gained power so i want to see how far i can push it. Probably be a waste of time, but makes sence in my head!
turbo 16v k-series 11.9@118.9 :)
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 6752 Posts Member #: 828 Post Whore uranus |
27th Feb, 2012 at 07:34:09am
good thinking denis. Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM |
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3594 Posts Member #: 655 Post Whore Northern Ireland |
27th Feb, 2012 at 09:53:52am
On 27th Feb, 2012 evolotion said:
i just want to try it :) every time i went bigger on the turbine i gained power so i want to see how far i can push it. Probably be a waste of time, but makes sence in my head! On my old turbo(pulsar) the turbine was definately not a restriction, the compressor was about to be though, and if i can make the engine breathe better(valves, cams, another 1000rpm) i ought to be able to make use of a larger turbine and a more suitable compressor that wont fall on its arse above 30psi lol and if it goes tits up its no biggie to cut the flange off and swap to a more sensible turbo :) What is your current boost/ex manifold pressure ? Only car I tested recently was around 600bhp, and 35/57psi which was a pretty good result all things considered. It's amazing they go so well and rev so well when manifold pressure appears so high ( compared to n/a thinking ) 9.85 @ 145mph
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2909 Posts Member #: 83 Post Whore Glasgow, Scotland |
27th Feb, 2012 at 12:24:44pm
No idea Stevie, didn't get the chance to measure it before I cracked that liner and took the engine out. The fact that I got full boost just slightly north of 5k says it wasn't restrictive, but I was having to have the wastegate almost fully shut at the red line to maintain 30psi, I presume this was because the compressor was becoming inefficient and harder to drive. But as usual that's just a hunch :) obviously there are a lot more factors at play but see how it rolls! turbo 16v k-series 11.9@118.9 :)
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326 Posts Member #: 1323 Senior Member |
27th Feb, 2012 at 03:38:53pm
On 26th Feb, 2012 evolotion said:
just to throw this in as a thought, tuned legnths and so on are not going to work on your average turbo motor, as the turbine poses such a large restriction, getting gas to it and through it quickly is the priority. Surely tuned lengths do exactly what your suggesting you want to achieve , they use the exhaust pulses to maintain the gas velocity , rather than the pulses canceling each other out and so reducing their velocity . Sure the turbine is a restriction , but I would have thought Anything to maintain the exhaust velocity until it meets that restriction would be worthy while ? |
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326 Posts Member #: 1323 Senior Member |
27th Feb, 2012 at 03:55:37pm
can anyone direct me to a 'Simple' [I am crap at maths] explanation/calculation for working out tuned exhaust manifold lengths , both n/a and boosted
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8604 Posts Member #: 573 Formerly Axel Podland |
27th Feb, 2012 at 04:01:02pm
It is a very complex science.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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2909 Posts Member #: 83 Post Whore Glasgow, Scotland |
27th Feb, 2012 at 06:46:09pm
They do, with the right turbine(as i also suggested i'll be trying to use!, quite how im going to fit it all under the bumper is another matter) But i can see the merit in not using tuned lengths with a restrictive turbine as the turbine poses such a restriction that you can go small on the manifold diameters keeping the gas velocity very high, but the bottleneck will still be the turbine. and you gain in spool times, and can make up for the lack of VE near the red line by simply pumping in more boost. a-la pretty much all modern petrol turbos. imho ofcourse.
On 27th Feb, 2012 carl talbot said:
On 26th Feb, 2012 evolotion said:
just to throw this in as a thought, tuned legnths and so on are not going to work on your average turbo motor, as the turbine poses such a large restriction, getting gas to it and through it quickly is the priority. Surely tuned lengths do exactly what your suggesting you want to achieve , they use the exhaust pulses to maintain the gas velocity , rather than the pulses canceling each other out and so reducing their velocity . Sure the turbine is a restriction , but I would have thought Anything to maintain the exhaust velocity until it meets that restriction would be worthy while ? turbo 16v k-series 11.9@118.9 :)
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3594 Posts Member #: 655 Post Whore Northern Ireland |
27th Feb, 2012 at 09:20:25pm
On 27th Feb, 2012 evolotion said:
No idea Stevie, didn't get the chance to measure it before I cracked that liner and took the engine out. The fact that I got full boost just slightly north of 5k says it wasn't restrictive, but I was having to have the wastegate almost fully shut at the red line to maintain 30psi, I presume this was because the compressor was becoming inefficient and harder to drive. But as usual that's just a hunch :) obviously there are a lot more factors at play but see how it rolls! Either the compressor is too small to supply enough air. Or your turbine is so large there simply isnt enough energy to spin it fast enough to make boost. So what size is the compressor ? engine ? Power ? it certainly wont be because the compressor is too hard to drive. That's the easy bit. 9.85 @ 145mph
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326 Posts Member #: 1323 Senior Member |
27th Feb, 2012 at 09:24:46pm
On 27th Feb, 2012 Paul S said:
It is a very complex science. Pulses are very much alive and ready to be used to good effect with tuned lengths. That was my original point. I'm with you on this , I re read the original link , he does say ignore tuned lengths , originally I put this together [in my head] with his later comments on tight packaging and what is the most essential aspect of header design , ie maintaining exhaust velocity , Surely its pretty much a given , that if exhaust velocity is what drives the turbine , then Anything that maintains the available exhaust velocity from the combustion chamber to the turbine , Must be a +ve ps Paul , are there any simplified sorts of 'rules of thumb' to get a half decent , reasonably effective pulse tuned [or at least one that isn't working against you] tubular exhaust manifold |
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8604 Posts Member #: 573 Formerly Axel Podland |
27th Feb, 2012 at 09:32:57pm
Carl, basically what works best for NA works best for turbo. There is a slight difference due to the change in the speed of sound under higher temperatures and pressures.
Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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8604 Posts Member #: 573 Formerly Axel Podland |
27th Feb, 2012 at 09:36:16pm
And don't go any bigger in diameter than the port. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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326 Posts Member #: 1323 Senior Member |
27th Feb, 2012 at 10:08:49pm
On 27th Feb, 2012 Paul S said:
As a "rule of thumb"..... 1ft long on the inlet and 2ft long on the exhaust :) Thanks for your Pearls Please excuse my ignorance/slowness Is this a generalised 2:1 ratio or specific to the 'A'series On a turbo its an obvious dimension, head to turbine but on a N/A are you talking Primaries or the whole manifold to single pipe [ I'm trying to sort a 4-2-1 for 1200cc supercharged] |
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2909 Posts Member #: 83 Post Whore Glasgow, Scotland |
27th Feb, 2012 at 11:02:29pm
On 27th Feb, 2012 stevieturbo said:
Either the compressor is too small to supply enough air. Or your turbine is so large there simply isnt enough energy to spin it fast enough to make boost. So what size is the compressor ? engine ? Power ? it certainly wont be because the compressor is too hard to drive. That's the easy bit. I know you know your onions buddy, and i appreciate what your saying but i really want to build this engine to see what it does, i dont want to debate/discuss it :) you can be the first to say i told you so when i run a 15dead. only posted in here as i disagree with the generic "tuned lengths don't work on a turbo" philosophy but at the same time i can completely appreciate why a shorter, good flowing more direct manifold would be of more benefit in certain applications. i.e. a modest equal legnth manifold. i just feel a larger turbine would allow you to exploit a properly tuned manifold rather than just making it equal length and nice flowing. but obviously this is not for everyone as it will be very very laggy. turbo 16v k-series 11.9@118.9 :)
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326 Posts Member #: 1323 Senior Member |
27th Feb, 2012 at 11:53:29pm
On 27th Feb, 2012 evolotion said:
as it will be very very laggy. maybe not if you get the 'tuned lengths' working properly for you ? chuck in a bit of fuel at the right time when the ex valves are open and WOOOSH 
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8604 Posts Member #: 573 Formerly Axel Podland |
28th Feb, 2012 at 09:18:18am
On 27th Feb, 2012 carl talbot said:
On a turbo its an obvious dimension, head to turbine but on a N/A are you talking Primaries or the whole manifold to single pipe [ I'm trying to sort a 4-2-1 for 1200cc supercharged] I didn't think we were talking about A series here. The standard primary length of 375mm or 15" seems to work well. On 27th Feb, 2012 evolotion said:
i just feel a larger turbine would allow you to exploit a properly tuned manifold rather than just making it equal length and nice flowing. but obviously this is not for everyone as it will be very very laggy. I agree that you need a free flowing turbine to get the tuned lenghs to work. No point in tuning the lengths to get peak torque at 6k when the turbine is starting to strangle the engine by then. But it will only take a few extra revs to fill the larger volume of the manifold, particularly if you don't go overboard on runner bore. Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
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