sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jun 20, 2021 4:35:13 GMT -5
Dear all, I've gained a lot of knowledge from the forum, and built a turbo jet. To my surprise, I got it running after a few attempts! So, thanks for all the knowledge that you have unknowingly already provided! Here is a video of the latest run: www.youtube.com/watch?v=s6zuE0JLqng I think in that run the compressor outlet pressure gauge got to around 9 psi (at the end of the run where you see the whole thing slide along) I have plans to make various improvements (hot bits made from stainless, oil pressure alarm, fit a thrust nozzle, nicer sump, etc.) In the meantime, I had a few immediate questions, if you were able to guide me please: 1. What is the best way to measure rpm? The turbo is a cheap unit from eBay (although seems very solid). I'm scared to run it too hard for fear of destruction. 2. What would you limit the rpm to (given the cheap turbo)? 3. What is the best way to add a thermocouple to the outlet? 4. From the video, can you see anything else that could be improved, looks too hot, too dodgy or too dangerous, etc? Thank you very much in advance. I've included all the specs below. Steve. Turbo specs:See www.ebay.com.au/itm/123976088260 Cooling Type: Oil Cooled T4 Split chamber inlet to turbine Compressor Trim: 50 Compressor Inducer Diameter: 69mm Compressor Exducer Diameter: 98mm Compressor A/R: 0.66 Turbine Trim: 78 Turbine Inducer Diameter: 88mm Turbine Exducer Diameter: 77.5mm Turbine A/R: 1.05 Bearing Type: Wet Float Bearing Wastegate: External Wastegate Flame tube specs:length = 450mm ID = 140mm Typical 30/20/50% primary/secondary/tertiary holes, with total hole area adding to 100% of the compressor inducer area Mild steel (with a view to upgrading to stainless) Oil specs:Trochoid pump at around 40 psi, plenty of flow. Bleed valve and electric motor controller to control pressure/flow Oil: synthetic 0W-20 Fuel: LPG
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Post by enginewhisperer on Jun 20, 2021 6:07:47 GMT -5
that's a pretty smooth run for a first turbine! Ideally I'd switch to some higher temp rated hoses for the oil system so you don't have to worry about them failing when you do longer runs. I have used push lock hydraulic hose with good success, but hard lines for the areas close to the hot parts can be a good idea. The basic laser tachometers you can get on ebay work ok if you can paint the compressor nut matt black and shiny white, but it's always hard to get a reliable pickup. I have generally just used the comp outlet pressure and stayed below 30psi or so on a smaller turbo. If your turbine intake temps are ok and it doesn't surge, the turbos are pretty hard to kill
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Post by racket on Jun 20, 2021 19:51:45 GMT -5
Hi Steve Welcome to the Forum :-) A good choice of turbos with a sensible matching of comp and turb sizings . The ebay laser tachs come with stick on reflective tape , which if you cut a halfmoon crescent and stick it to the radial face of the comp snout outboard of the comp nut along with the half white half matt black paint on the snout , ibb.co/NCC1H79 you should get a reasonable chance of readings You may need to go to a 5W40 synthetic if your oil temps get hot , 0-20 won't keep the rotor under control quite as good. Yep , metal plumbing anywhere near heat and especially if theres pressure and flammables involved . You might find that just propane won't get you to full power with the flows you'll need , the cylinder will soon "freeze" from the drawoff rates. Take Andrews advice and keep below 30 psi P2 , maybe even ~25psi unless you have accurate RPM numbers and they're below ~85,000 rpm max, and no more than ~600 deg C max coming out of the turbine .............please , no glowing turb wheel :-) Ideally the oil drain should be a continuous downhill slope and empty into the tank above the oil level to prevent lube backing up into the turbo. Thermocouples best mounted into the jetpipe wall a couple of inches downstream of the exducer , a P4t pitot tube for measuring total pressure exiting the wheel is also a nice tuning device . Heh heh , no hanging onto that air delivery tube once up to higher P2s , you'll end up with bad burns ;-) Jetpipe and jetnozzle now required , maybe ~63 mm nozzle Cheers John
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jun 21, 2021 19:02:21 GMT -5
Hi Andrew and John.
Many thanks! Excellent suggestions.
For the hard lines, 1/2” copper is probably the easiest/cheapest option would you say? ie local hardware store has all the required bits.
What is the purpose of the jet pipe after the turbine exducer? ie you wouldn’t just attach a conical nozzle straight on to the turbo?
Thanks again! Steve.
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Post by racket on Jun 21, 2021 19:33:10 GMT -5
Hi Steve
Yep , 1/2" annealed copper for oil pressure line ,a very short section of plastic tubing on the turbo drain allows for inspection of lube flows , I use steel bundy brake line for the fuel and pressure pickup lines , fittings are brass air compression types.
You can fit the nozzle directly onto the scroll , but a few inches of jetpipe allows the gases exiting the exducer to sort themselves out and the straight wall of the jetpipe allows for fitting thermocouples etc , try to maintain a smooth flow area from exducer to jetnozzle , any steps create losses .
Cheers John
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jun 23, 2021 5:17:14 GMT -5
Thanks John. OK I have some improvements to make. I might also put the oil system below decks so it’s shielded from the heat. Was quite a surprised at just how much heat this thing generates! All good. Was a big buzz to get her going. Thanks again. Steve.
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jun 24, 2021 0:59:24 GMT -5
Hi again. Sorry another newbie question if you are able..... what thread tape / sealant do you use to seal (hot) oil pressure BSPT fittings? Thanks yet again. Steve.
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Post by racket on Jun 24, 2021 3:39:23 GMT -5
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jun 24, 2021 5:44:30 GMT -5
Legend thanks John
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Post by racket on Jun 24, 2021 17:07:18 GMT -5
I use it for lotsa sealing jobs , fuel, stubs, nuts , it lasts for years as you only need a couple of drops , and parts can be easily disassembled
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stevie
Junior Member
Joined: November 2020
Posts: 55
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Post by stevie on Jun 29, 2021 22:55:33 GMT -5
Awesome and inspiring. Was wondering about max RPM on the ST50.
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Post by racket on Jun 29, 2021 23:27:35 GMT -5
Use 1450 ft/sec max for the comp tip speed , so depending on its diameter the RPM will differ .
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jul 22, 2021 20:38:02 GMT -5
Hi John - sorry tedious detail question - the instructions for 569 sealant say you should use also the loctite primer when using 569 on stainless steel fittings (which mine are). Stupidly I didn't order any primer. In your experience is the primer necessary? Thanks very much. Steve.
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Post by racket on Jul 22, 2021 21:19:12 GMT -5
Hi Steve
I've never used primer
Cheers John
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sydneyoz
Member
Joined: June 2021
Posts: 18
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Post by sydneyoz on Jul 23, 2021 3:46:02 GMT -5
That’s what I wanted to hear! Thanks John.
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