badger
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Joined: August 2020
Posts: 17
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Post by badger on Aug 28, 2020 14:45:44 GMT -5
Here's 'another' preliminary question... food for future thought. I don't want to use a leaf-blower, etc. to start my engine. I'd like to introduce compressed air into the engine case in order to spool things up. Would it be best to introduce that compressed air onto the compressor, into the combustion section, or upon the turbine?
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Post by wannabebuilderuk on Aug 28, 2020 17:50:56 GMT -5
For choosing a turbocharger I'd say look for one with the following main key details - 1. No wastegate (if there's a wastegate then it probably doesn't meet rule 3) 2. Single scroll on the turbine housing. 3. Turbine wheel ~20% larger in area compared to compressor wheel (use the model number on the id tag to find it on turbo parts websites to get the dimensions) As for the compressed air starting you'd want to direct the air onto the compressor blades like so halfway down the page- jetandturbineowners.proboards.com/thread/1056/diy-turboshaft-engine?page=17
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badger
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Joined: August 2020
Posts: 17
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Post by badger on Aug 28, 2020 20:57:22 GMT -5
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Post by racket on Aug 28, 2020 21:45:05 GMT -5
Hi Tom It can be a frustrating business finding a suitable turbo , there are simply thousands of turbo configurations , take the "common" Garrett TV81 www.turbomaster.info/eng/catalogs/model.php?base=garrett&pagina=TV81 for most models theres no information because of confidentiality between turbo manufacturer and engine manufacturer, the few that give part numbers still don't give much explanation or size of comp/turb wheels. The Garrett site www.garrettmotion.com/racing-and-performance/ does have info , but mainly for automotive size turbos www.garrettmotion.com/racing-and-performance/performance-turbos/ where the downloadable maps, both comp and turb can be used to obtain a good flow match . Theres often a great deal of guesstimation with regards our engines . The TV84 turbo I used in my bike jetandturbineowners.proboards.com/thread/1366/tv84-turbine-bike needs a 1.39 A/R turb housing on the 110/96 mm turb wheel , with a 3.5"/4.625" comp wheel , its off a 475HP Detroit Diesel engine . The only "reliable??" rule of thumb is to have the turb wheel outlet >20% greater in area than the comp wheel inlet area. Yeh, there is a huge amount of variables with building gas turbines , thats what makes them interesting and keeps the old grey matter working , we'll never know everything , ..........I'm still learning after 30 years . Cheers John
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Post by sauerkraut on Aug 28, 2020 23:22:49 GMT -5
Badger, that is the turbo I used on my build. You can find the same one on like 10 different ebay listings for as low as $150.
Like I said, it is generally a good fit other than the split turbine housing.
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Post by racket on Aug 28, 2020 23:34:51 GMT -5
Hi Tom
Yep , that one would work , turb exducer ~26% bigger area than comp inducer .
But remember its a $199 turbo , not a $1990 turbo , so be modest with your temperatures , 600C - 1100F max for the jetpipe temp , and pressures, 15 psi "boost" P2 from the compressor .
OK to learn with :-)
Cheers John
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badger
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Joined: August 2020
Posts: 17
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Post by badger on Aug 29, 2020 14:40:03 GMT -5
Thanks guys! This will likely become my first set of 'training-wheels', 'per se'. John, your technical advisories are well noted, pertaining to this turbo. I'll not be pushing any envelopes. My current goal is to simply be successful in a build that will sustain a steady, controllable burn without a lot of 'sputter-fussing' and 'flame-outs' after I figure out just what the engine wants in the design of a burn can, hole patterns, hole sizes, hole locations, etc. I'll likely be able to figure out a lot of things as I go, however. Starting with a proper turbo platform is the most important first step. If I tried using a turbo unsuitable for this sort of application... I'd just be "Shooting from the hip", into the dark, and struggling to sort things out to the point that I'd likely give up through frustration and disappointment. If you guys give this turbo your blessings, I'll go for it and feel confident that I'm off to a good start! I'm truly grateful for the help so far. You guys are helping me out more than you probably know! Regards, Tom...
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Post by racket on Aug 29, 2020 18:10:55 GMT -5
Hi Tom
Yep , an unsuitable turbo will only give grief , you should be OK with this one , its not ideal having the twin entry into the turb scroll as twin scrolls have more losses due to the extra wall friction , but for the price its well worth using .
Google Jetspecs for flametube size
Cheers John
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badger
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Joined: August 2020
Posts: 17
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Post by badger on Aug 30, 2020 15:26:26 GMT -5
Hello John
Any idea as to how deep that twin entry 'baffle'/'wall' goes into the turbo-scroll? Is it something that I could 'whittle' out via the ol' Bridgeport Mill?
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Post by racket on Aug 30, 2020 16:50:12 GMT -5
Hi Tom
It goes all around the scroll to produce two independant "nozzles" feeding the turbine wheel , it maximises the exhaust energy from a 4 cylinder engine where the pulses don't overlap as with a 6 or 8 cylinder engine .
You just need to leave the stainless exhaust gasket across that section to protect the web from erosion
Cheers John
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badger
Member
Joined: August 2020
Posts: 17
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Post by badger on Sept 1, 2020 17:01:14 GMT -5
John, "Thanks again!" I'm gonna put this turbo on my 'short' list, for purchase, albeit. I'm willing to bet that with a little patience and a lot of shopping around I can find a similar turbo, as this one, 'WITHOUT' that 'twin-entry' design. Back to the ol' drawing board. I'm going to do a bit more shopping before I pull the trigger on a turbo.
It's little bits of 'Oh-So' important details, such as this that I seek. Thanks again, John!!!
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