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Thread: 7MGTE Oil pressure system.

  1. #51
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    Default Re: 7MGTE Oil pressure system.

    Given the gear pump is a fixed displacement pump, does pressure matter at all?

    Assuming you add extra resistance to flow from say the stock oil feed tube & banjo bolt, or an external full flow oil cooler and tubing, why does it matter? The system will still be flowing the exact same gpm flow rate and therefore the pressure drop inside the engine post filter and cooler will be identical. The only downside of the extra resistance is a bigger load on the pump, and more wasted hp driving the pump, the engine internally won't know anything different.

    Sure, if taken to the limit with ridiculous extra flow resistance this obviously fails,as the pump pressure relief opens at something like 80 psi and at that point flow rate will drop, but that's not happening with any of these setups.

    Compared to the stock system, it would seem any full flow arrangement would be superior as it will always direct the full pump output through the engine instead of diverting some fraction of pump flow through the parallel connected cooler like the stock setup.

    Even so, below 40 psi pump pressure, both stock and full flow behave identically. That is, all the pump output goes through the engine.

  2. #52
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    Default Re: 7MGTE Oil pressure system.

    You're right, it shouldn't matter. It would all depend on the releif valve. At what point does it start to open to bleed volume off? It may be rather low pressure or the springs are suffering from major fatigue because I've seen several reports of increased oil pressure at idle with shimmed pumps, which shouldn't be affected.

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    Default Re: 7MGTE Oil pressure system.

    Quote Originally Posted by 3p141592654 View Post
    Given the gear pump is a fixed displacement pump, does pressure matter at all?

    Assuming you add extra resistance to flow from say the stock oil feed tube & banjo bolt, or an external full flow oil cooler and tubing, why does it matter? The system will still be flowing the exact same gpm flow rate and therefore the pressure drop inside the engine post filter and cooler will be identical. The only downside of the extra resistance is a bigger load on the pump, and more wasted hp driving the pump, the engine internally won't know anything different.

    Sure, if taken to the limit with ridiculous extra flow resistance this obviously fails,as the pump pressure relief opens at something like 80 psi and at that point flow rate will drop, but that's not happening with any of these setups.

    Compared to the stock system, it would seem any full flow arrangement would be superior as it will always direct the full pump output through the engine instead of diverting some fraction of pump flow through the parallel connected cooler like the stock setup.

    Even so, below 40 psi pump pressure, both stock and full flow behave identically. That is, all the pump output goes through the engine.
    I wouldn't make the assumption any 7M oil pump is a truly fixed volume pump. If the gears seal perfectly it's theoretically a fixed volume pump, but I doubt that's actually the case. Is it negligible? I don't know. As seems to be the theme of this thread... without data it's all a guessing game.

    For a street driven car, I think the big detriment of the full flow system is that you now have exposed lines running around the lower part of the front of the engine bay that carry 100% of your oil. Hit a rock or something that ruptures a line or springs a leak in a fitting? You could have a dead engine in seconds. That's less of a concern with the factory system or one like piratetip's where you would slowly lose oil and have a much higher chance of catching it before you're running on no oil.

    Do any OEM systems run full flow oil systems with exposed line any longer than a few inches? I've never seen it, but maybe I just haven't looked at the right engines!

  4. #54
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    Default Re: 7MGTE Oil pressure system.

    the lines aren't any more exposed than stock unless you've done a really shitty job installing them. If I hit a rock hard enough to hit the lines I've got, I have much bigger problems than a leaking line or fitting.

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    Default Re: 7MGTE Oil pressure system.

    Quote Originally Posted by Enraged View Post
    the lines aren't any more exposed than stock unless you've done a really shitty job installing them. If I hit a rock hard enough to hit the lines I've got, I have much bigger problems than a leaking line or fitting.
    Yes, but there is a massive, monumental difference between the stock system and full flow in that scenario. The stock system can take a hit to the line, spill oil and actually be perfectly functional if the pressure relief valve closes well. An aftermarket full flow in the same situation would very easily yield catastrophic engine failure because you immediately lose oil flow to the internals.

    This is the key pro of the stock system I think a lot of people overlook.

  6. #56
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    Default Re: 7MGTE Oil pressure system.

    You would think that someone had at least characterized a small block chevy oil pump, but I came up empty handed. This is data of a gear pump very similar to the 7M design, so at least it is representative. You can see that the "slip" pf the pump is pretty small over a huge pressure range. These pumps really are pretty close to ideal as far as flow versus pressure goes. Remember ideal would be a vertical line.

    Its true that hose failure would be bad news on a full flow. But I am always reminded of jetjock who knocked his fumuto valve out of his oil pan and drove his supra a couple of miles on the freeway with no oil before realizing something was very wrong. Engine never failed, and he put many thousand of miles on that car after the incident with no apparent issues.
    energies-10-01113-g013.jpg

    The 2GR-FE has an oil-water cooler and the oil is carried to the cooler using two rubber hoses molded into a contraption. Those hoses are prone to pinholes on high mileage cars and the results can be catastrophic. There is also an all metal version of the contraption. I put that on my car as I was worried about the rubber hoses. So I guess if you are asking for production cars with hoses this is an example.

    Image2.jpg

    there is also another rubber oil hose on that engine that was the subject of a recall due to early failures, again with bad results.

    Image1.jpg
    Last edited by 3p141592654; February 12th, 2018 at 07:38 PM.

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    Default Re: 7MGTE Oil pressure system.

    Quote Originally Posted by suprarx7nut View Post
    Yes, but there is a massive, monumental difference between the stock system and full flow in that scenario. The stock system can take a hit to the line, spill oil and actually be perfectly functional if the pressure relief valve closes well. An aftermarket full flow in the same situation would very easily yield catastrophic engine failure because you immediately lose oil flow to the internals.

    This is the key pro of the stock system I think a lot of people overlook.
    If you hit a rock hard enough to damage something, are you going to keep driving? Or are you going to immediately pull over and check the car? I don't think you're an idiot, so I'll assume that you, like I, would pull over right away. So that negates that one benefit of the stock system. Now if the owner is an idiot, you might be right.

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    Default Re: 7MGTE Oil pressure system.

    Quote Originally Posted by Enraged View Post
    If you hit a rock hard enough to damage something, are you going to keep driving? Or are you going to immediately pull over and check the car? I don't think you're an idiot, so I'll assume that you, like I, would pull over right away. So that negates that one benefit of the stock system. Now if the owner is an idiot, you might be right.
    Valid point, I suppose. Depends what causes the damage. If I hit a big rock, sure. I think the complete failure point of many of the hoses and fittings is well below a chassis jarring collision though. Full throttle with some music playing and I could see not hearing something happen that could spring a serious leak or rip a fitting off. Pending the placement of the cooler you could also take a small rock to the heat exchanger and leak.

    Look at Pi's story above about Jetjock - not exactly a clueless idiot. You'd like to think you'll always catch a damage inducing incident the moment it happens, but that's not always the case.

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    Default Re: 7MGTE Oil pressure system.

    Yes, that's also a good point. I would hope that if you have a full flow system, you also have an oil pressure gauge with alarm though.

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    Default Re: 7MGTE Oil pressure system.

    Quote Originally Posted by 3p141592654 View Post

    I have always liked the more modern coolant-based oil coolers such as on the JZ engines or pretty much anything else these days. Seems it has the advantage of warming the oil when cold without requiring a thermostat which will eventually fail.
    Even Ford does it.
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