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  1. #181
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    +1 for an oil cooler or a bigger one
    " Money is for those without skills"

  2. #182
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    I've heard of a rule of thumb, "poor oil pressure kills big end bearings, high oil temp kills main bearings" So far I'm for believing this one but I'd like to see more proof.
    " Money is for those without skills"

  3. #183
    Registered User neil_se's Avatar
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    Cheers Staples, it's good to know someone else has similar experiences. I have AN12 lines off each breather but I don't think the catch can itself can handle the air flow as it still blows oil out of the filter.

    I'd be surprised if the oil was getting too hot from a short session at moderate pace, cool air temps, Penrite Ten Tenths racing 10w40. When I say the pressure drop matches the rise in water temp, water still only peaked at 85 degrees. I don't have an oil cooler fitted as most of my events are 5-10 min runs so I didn't feel the need as it struggles to get up totemp. Next practice day is in a month so as the first measure I'll fit an oil temp sensor and run 15w50 oil.

    It's fairly well documented with these L92 heads that oil gets trapped in the heads and can't drain well enough. There are plenty of documented bearing failures in LS3 Corvettes running sticky tyres on long high G left-hand turns due to running dry at the oil pickup. I did what I could during the engine build to mitigate the risk by using a deep, winged and baffled pan, crank scraper and windage tray. I don't think feel that's what's happening here though.

    Dry sump is the obvious cure-all to give me the crankcase vacuum I need to better seal the rings, reduce blow by, aid oil drain from the heads, stablise oil pressure, give more ground clearance, etc. It's a pretty significant investment for a grassroots motorsport toy though and would severely eat into my sequential gearbox savings plan. There's some packaging issues too as my balancer is already very close to the radiator so everything would need to be reworked.
    Last edited by neil_se; 18-05-18 at 10:04 PM.

  4. #184
    Down with ma homies Greg Rust's Avatar
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    Ok cool. I was interpreting your data as an excessive oil temperature issue and lowering of viscosity leading to a drop in oil pressure.

    Any chance you can tap into the heads and put large drain lines direct to the sump.
    xw Falcon 393 full race cam, NGK spark plugs.

  5. #185
    Registered User neil_se's Avatar
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    My mechanic suggested that, I need to pull off the covers and see where it might be possible.

  6. #186
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    Quote Originally Posted by neil_se View Post
    After the last track day I changed the oil and worryingly drained 0.5L from the catch can as well (was emptied before). The LS is known for breathing pretty heavily but that amount from about 1 hour of run time had me concerned. I had it compression and leakdown tested this week and they checked out fine.

    I took it down to Morgan Park practice today to test the 5/8" front brake master and I also ran some logs. In my first stint after about 10 minutes, the Haltech ecu cut power as the oil pressure had fallen below the min value. I immediately pulled over and shut it down for a short while before restarting, checking oil pressure and slowly driving back to the pits.

    The catch can had about 100ml in it (it also did a few dyno pulls yesterday) but there was also a lot around the can vent and the dipstick had been forced out. I added another 1L of oil and went back out a while later. He's some of the logs from that stint.



    The oil pressure gradually drops over the session until I back off and return to the pits. This curve would inversely follow the increase in oil temp (I don't have a sensor but the water temp increased in that manner) so perhaps the oil is too low viscosity (10W-40 Penrite).



    This snippet shows the oil pressure dropping quickly and dangerously low with braking/dropping rpm. I can't really determine whether it's just the oil pump being spun slower or if the oil is also moving away from the rear sump pickup (which is in a deep and baffled pan).

    Need to do some more thinking and consider what my options are.
    That looks to me like you are getting oil surge under brakes (This correlates with it being a rear sump), which is getting progressively worse as the engine accumulates more oil in the head over the course of the session, and therefore has less oil around the pickup.

    If I were you I would be looking at how to get the oil out of the head and back into the sump quicker, as Greg Rust says above, plus have a look at the effectiveness of the sump baffling. A lot cheaper and easier than a dry sump.
    Last edited by Sprinkles; 19-05-18 at 09:17 AM.

  7. #187
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    Do not dismiss oil temp, I was having issues with it in a 3 minute race!

    Another thing is, your water temp is controlled by a thermostat. Your oil temp can drag the water temp up as oil temp exceeds water temp. Ideally oil temp shouldn't exceed water temp and not go over 100 degrees c either.

    P.S. youv'e also got an oil surge issue, meh! As long as pressure isn't dropping to low ( looks at graph) hmmm yes you have an issue.
    " Money is for those without skills"

  8. #188
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    Quote Originally Posted by neil_se View Post
    After the last track day I changed the oil and worryingly drained 0.5L from the catch can as well (was emptied before). The LS is known for breathing pretty heavily but that amount from about 1 hour of run time had me concerned. I had it compression and leakdown tested this week and they checked out fine.

    I took it down to Morgan Park practice today to test the 5/8" front brake master and I also ran some logs. In my first stint after about 10 minutes, the Haltech ecu cut power as the oil pressure had fallen below the min value. I immediately pulled over and shut it down for a short while before restarting, checking oil pressure and slowly driving back to the pits.

    The catch can had about 100ml in it (it also did a few dyno pulls yesterday) but there was also a lot around the can vent and the dipstick had been forced out. I added another 1L of oil and went back out a while later. He's some of the logs from that stint.



    The oil pressure gradually drops over the session until I back off and return to the pits. This curve would inversely follow the increase in oil temp (I don't have a sensor but the water temp increased in that manner) so perhaps the oil is too low viscosity (10W-40 Penrite).



    This snippet shows the oil pressure dropping quickly and dangerously low with braking/dropping rpm. I can't really determine whether it's just the oil pump being spun slower or if the oil is also moving away from the rear sump pickup (which is in a deep and baffled pan).

    Need to do some more thinking and consider what my options are.
    And the pressure drop isnít from the pump being spun lower, looking at the second graph, the corner before the white line, you can see the throttle blip from the downshift, revs go up and oil pressure keeps going down. If you could overlay long Gs or brake pressures I think you would see the correlation to oil surge.

    +1 for an oil temperature gauge, before you buy a bigger oil cooler.

  9. #189
    Registered User neil_se's Avatar
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    In general the oil pressure follows revs though. Here's a snip from earlier that session.




    Here's an overlay of water temp against oil pressure too. There's no thermostat, it's a Moroso elec water pump with restrictor plate in the filler housing.




    I also initially thought that the gradual decrease was due to oil trapped in the heads, but the more I thought about it I don't think that would cause a gradual decrease in pressure. I imagine it would be a more sudden drop once it gets to the point where the pickup is uncovered. The oil is definitely moving away from the pickup under heavy braking though, I had a look at the first log before I added the extra 1L of oil and there were some deep drops in pressure even when the average pressure was higher.

    Anyway it's pretty much guesswork until I can log temp and try some thicker oil (35% off Penrite today at SCA) as the first solution.

  10. #190
    Registered User neil_se's Avatar
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    The other thing I should rule out is a loose or cracked oil pickup.

  11. #191
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    Quote Originally Posted by neil_se View Post
    In general the oil pressure follows revs though. Here's a snip from earlier that session.




    Here's an overlay of water temp against oil pressure too. There's no thermostat, it's a Moroso elec water pump with restrictor plate in the filler housing.




    I also initially thought that the gradual decrease was due to oil trapped in the heads, but the more I thought about it I don't think that would cause a gradual decrease in pressure. I imagine it would be a more sudden drop once it gets to the point where the pickup is uncovered. The oil is definitely moving away from the pickup under heavy braking though, I had a look at the first log before I added the extra 1L of oil and there were some deep drops in pressure even when the average pressure was higher.

    Anyway it's pretty much guesswork until I can log temp and try some thicker oil (35% off Penrite today at SCA) as the first solution.
    I see your point on that second graph with the "trend line" (not shown) of the oil pressure falling as the water temperature rises.

    However, at the 3:20 mark the oil pressure has already dropped a fair bit (can't tell how much) and the water temp is only 70 degrees, barely warmed up. I'm assuming the left hand Y axis is showing the water temp. And if that's right, you are not even getting to 90 degrees water temp, so it's not running hot. I'm having a hard time believing that it's running that hot that it's affecting oil viscosity that much.

    I think your cracked pickup suggestion is worth investigating, the crack could be opening up as it warms up and draws in more air.

    See if you can get the oil temp logging and thicker oil tested on the dyno prior to your next outing, trouble shooting this sort of problem on race day will spoil your fun day out on the track.

  12. #192
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    When I was chasing possible oil temp issues it was the infra red heat gun to the sump that gave away the issue, 112 degrees C, engine coolant temp was normal @ 80 degrees C.....

    There is a point after which the oil temp will drag the coolant temp up with it.
    " Money is for those without skills"

  13. #193
    Registered User neil_se's Avatar
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    Yeah that's right Sprinkles, it only peaks at 88 degrees and that's on the cool down lap. It's had a fair bit of dyno time and they never noticed the oil pressure drop.

    Another simple thing I need to check is that the sump baffles are opening correctly.

  14. #194
    Registered User Staples's Avatar
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    I'm not sure I'm reading this right but that lowest spike is 16.8psi of oil pressure @980ish rpm?

    If so then I dont think you have a problem at all.

  15. #195
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    Quote Originally Posted by neil_se View Post
    Yeah that's right Sprinkles, it only peaks at 88 degrees and that's on the cool down lap. It's had a fair bit of dyno time and they never noticed the oil pressure drop.

    Another simple thing I need to check is that the sump baffles are opening correctly.
    I'd be interested to see photos of the inside of your sump and your crank scraper.

    The trapdoors in the sump baffling should swing freely ie they should flap if you rock the sump side to side in your hands.

  16. #196
    Registered User adamRSLC's Avatar
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    I've had both LS1 and an L98 my race car, front wet sumped early commo.

    I found breathers are everything on the LS motor, in my case i have two 1 inch (25mm) hoses (re tapped rear fitting on passenger side, modified filler on drivers rocker cover) to a 5ltr catch can with two 1inch breathers. Inside the hoses is steel mesh to trap the oil and let the air go by, it works very well but took a while to get the right combo of breather size and steel mesh. I now have around 100ml per 10 lap race.

    It does look like you are dropping pressure however, general rule of 10psi per 1000rpm applies for the LS motor. My hot oil base pressure with the new L98 is 40psi with it getting to the relief pressure of 80psi around 6k, i do have a higher pressure oil pump fitted however. The old LS1 didnt quite reach those numbers, hot 20psi at idle maxed at 60psi at 7k. I flogged that thing to death with water temp at 110c and oil at 120c being the norm, it survived for 7 years so they will take a beating.

    As other have mentioned and going by your logs, is it possible it's keeping oil up in the head causing the oil pressure drop and filling the catch can?
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  17. #197
    Registered User neil_se's Avatar
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    Quote Originally Posted by Staples View Post
    I'm not sure I'm reading this right but that lowest spike is 16.8psi of oil pressure @980ish rpm?

    If so then I dont think you have a problem at all.
    It was than a few times in the first session when revs had climbed back over 3000rpm. Milodon who make the oil pan just messaged me back to say that it should only have 6 quarts + filter as I had in the first session otherwise it'll sit high in the pan and get aerated by the crank. That oil level was when it had the lowest drops.

  18. #198
    Registered User lukevl's Avatar
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    Can you stop being so concerned please? I have ONLY an idiot light at stock pressure and havenít investigated anything after track raping. I figured itís an LS so should be fine lol

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