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Post by Deleted on Aug 31, 2015 15:06:32 GMT -5
Hi Anders When the oil has had chance to warm a little, does the idle temp come down any and what is the idle oil pressure All Best Andy Hi Andy, When the oil has warmed up I have 4 kg oil pressure and the temps are still high, actually temps tend to creep upwards during long idle runs. /Anders Hi Anders Thats 60 psi ish, think you could back it off a little for idle ? I dont run kart or bike that high at idle, both ramp up with p2 ? but i dont know how your system is set up so this mite not be suited for you But do you think the temps going up could be heat soak, bits heating up ? its Odd All Best Andy
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Post by Johansson on Aug 31, 2015 15:28:11 GMT -5
Hi Anders Thats 60 psi ish, think you could back it off a little for idle ? I dont run kart or bike that high at idle, both ramp up with p2 ? but i dont know how your system is set up so this mite not be suited for you But do you think the temps going up could be heat soak, bits heating up ? its Odd All Best Andy I don´t think backing off the oil pressure will help. I did a test during the gas producer construction where I measured the rotor speed while spinning it with a brushless motor and changing the oil pressure, and the revs didn´t rise much even when I dropped the oil pressure below what is healthy. The Borg Warner S500 turbos we use in the jet kick spin by a flick of the fingers even with 6-7 kg of oil pressure, so I see no reason why the TV94 rotor should be this draggy. Since I will use the same rotor and bearings for the upcoming JU-02 engine I need to solve this issue.
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Post by Deleted on Aug 31, 2015 15:51:39 GMT -5
Hi Anders Thats 60 psi ish, think you could back it off a little for idle ? I dont run kart or bike that high at idle, both ramp up with p2 ? but i dont know how your system is set up so this mite not be suited for you But do you think the temps going up could be heat soak, bits heating up ? its Odd All Best Andy I don´t think backing off the oil pressure will help. I did a test during the gas producer construction where I measured the rotor speed while spinning it with a brushless motor and changing the oil pressure, and the revs didn´t rise much even when I dropped the oil pressure below what is healthy. The Borg Warner S500 turbos we use in the jet kick spin by a flick of the fingers even with 6-7 kg of oil pressure, so I see no reason why the TV94 rotor should be this draggy. Since I will use the same rotor and bearings for the upcoming JU-02 engine I need to solve this issue. erm..... does sound like your picking up some extra drag some how... like you have said a strip down may show something,
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Post by Johansson on Aug 31, 2015 16:00:24 GMT -5
It has been doing this since I built it so there must be something wrong with the design of the shaft tunnel.
Since the engine runs and doesn´t seem to wear the bearings out things must spin freely at higher revs, it just sort of bogs down when the revs are low.
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Post by racket on Aug 31, 2015 16:43:56 GMT -5
Hi Anders
The bearing drag on my 10/98 measured ~0.5 ft lbs prior to spoolup , now assuming our idle is 25,000 rpm , that works out at 2.4 HP at idle , there will also be rotational drag from the rpm at idle, but only another HP or so .
At say a 5 psi - 1.34 PR idle and a flow of ~1 lb/sec theres a temp rise of say 34 deg C during compression , so the comp is consuming ~20 HP , our total bearing drag with warm oil isn't a big percentage of what the turb wheel needs to produce .
If your ambient temps were a bit higher than normal, then your TOTs will be up by 20 or 30 degrees , but gas producer temps are most greatly affected by flow restrictions downstream , we really do need a "wastegate" in the interstage duct for producing "cool" idling .
Hopefully I'll be able to get that TV94 initial drag "problem" sorted with the 12/118 before its first spoolup .
Cheers John
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Post by Deleted on Aug 31, 2015 16:59:17 GMT -5
Is it only when oil pressure is on, it seems to spool well on the air..... just wondering if something is heating up, expanding.... pulling ?
have you tried seeing how free the engine is after its been run..... Just saying
I spent weeks looking for an issue on the 9/04, i convinced my self it was the engine, something i had done .... it turned out to be a change i had made else where that was causing problems.
Have you done any more with the electric start
All Best Andy
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Post by smithy1 on Aug 31, 2015 18:15:44 GMT -5
This is where the GT6041 is excellent, essentially no drag even at ~65psi oil pressure, I believe the thrust plate has oil pressure on both sides which helps greatly with the drag. Even when cold and oil pressure is @65psi (4.4kg), a flick of my finger will see it spin freely.
Does your thrust plate have a full 360 thrust face..?? Also...what weight/type oil are you running??
Cheers, Smithy.
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Post by racket on Aug 31, 2015 20:19:48 GMT -5
Hi Smithy
Yep , the TV94 thrust bearing is a 6 pad 360 degree unit , but its only one sided , designed to take the air loads on the back of the comp , but without that "balancing" load the rotating section is forced against the rear thrust washer which isn't fed pressurised oil .
On my 12/118 engine I've made mods to that buffer bearing to feed pressure lube to it , so hopefully providing some balance . .
Cheers John
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Post by Johansson on Sept 2, 2015 6:41:18 GMT -5
John: That is true, the outside temps were probably 20-25C higher now than during the winter runs so the TOT would be higher as well.
Smithy: I use a semi-syntetic 10w40 oil. Nothing fancy, the same type of oil that I use in my cars.
Andy: I haven´t actually checked the rotor drag after a run with oil pressure still applied, I´ll try to remember to do that this weekend. I won´t be doing any more work on the electric starter until I have solved the rotor drag problem, I don´t want to toast the starter or motor controller.
Cheers! /Anders
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Post by smithy1 on Sept 2, 2015 16:21:40 GMT -5
Smithy: I use a semi-syntetic 10w40 oil. Nothing fancy, the same type of oil that I use in my cars. Cheers! /Anders Yeah...that should work fine, I'm using a full synthetic 10W40 in the 6041 and I've had no issues with it at all, she keeps good pressure, ~65-70psi when cold and ~60psi when warm... she doesn't leak, smoke on shutdown or use any....Since fitting the oil cooler the oil temp rarely goes above ~80C, even after a couple of back to back runs...gives me a warm fuzzy feeling anyway. If your oil pressure is good when warm, I'm thinking using possibly a slightly lighter oil may help with drag when cold, maybe 5W30 or a real lightweight 0W20.....can't hurt to try.... Cheers, Smithy.
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Post by Johansson on Sept 3, 2015 1:38:40 GMT -5
Smithy: I use a semi-syntetic 10w40 oil. Nothing fancy, the same type of oil that I use in my cars. Cheers! /Anders Yeah...that should work fine, I'm using a full synthetic 10W40 in the 6041 and I've had no issues with it at all, she keeps good pressure, ~65-70psi when cold and ~60psi when warm... she doesn't leak, smoke on shutdown or use any....Since fitting the oil cooler the oil temp rarely goes above ~80C, even after a couple of back to back runs...gives me a warm fuzzy feeling anyway. If your oil pressure is good when warm, I'm thinking using possibly a slightly lighter oil may help with drag when cold, maybe 5W30 or a real lightweight 0W20.....can't hurt to try.... Cheers, Smithy. Hi Smithy, I haven´t experienced any reason to change the oil viscosity, I´ve started the bike without a problem in -10C after being stored outside the whole night at Speed Weekend. Good thing since 10 liters of 0W20 oil would cost an arm and a leg... Cheers! /Anders
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Post by smithy1 on Sept 3, 2015 14:24:34 GMT -5
I'll just get back in my box then...!!
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Post by racket on Sept 3, 2015 18:19:46 GMT -5
Hi Anders
A 25 C increase in ambient temp could produce your 100 deg rise in turb temps , the comp is less efficient at the higher temps .
Cheers John
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Post by Johansson on Sept 4, 2015 0:26:56 GMT -5
Hi Anders A 25 C increase in ambient temp could produce your 100 deg rise in turb temps , the comp is less efficient at the higher temps . Cheers John That much? No wonder the temps were a bit high last weekend.
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Post by racket on Sept 4, 2015 1:01:01 GMT -5
Hi Anders
LOL, I've been trying to find the exact ratio of temp change amongst my books , but the best I've found is a 3:1 ratio in one of the model turbine books by Schreckling .
A 25 C ambient increase is a large number , at full power the comp would be consuming at least another 20 HP for the same PR and flow, and that power has to come from somewhere , either a greater pressure drop across the turbine , which is difficult when theres a fixed area nozzle/freepower downstream , or by an increase in temperatures .
You might need to backoff the throttle a tad at full power to keep max temps under control, or add a bit of water injection to keep temps down , ~1.5 litres/minute should be enough , sprayed into your air intake plenum .
Cheers John
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