Page 70 of 120 FirstFirst ... 2060686970717280 ... LastLast
Results 691 to 700 of 1198

Thread: Cuda's Cars, v2.0

  1. #691
    mAdminstrator Random's Avatar
    Join Date
    Jan 2014
    Location
    Davis, CA, USA
    Posts
    3,547
    Quote Originally Posted by thesameguy View Post
    it's just a matter of choosing a vector to get your feet wet.
    Clogged AC drain.
    Whoomah!

  2. #692
    Senior Member
    Join Date
    Jan 2014
    Posts
    10,171
    That checks out!

  3. #693
    TSG's discussion of gauges reminded me to post this.

    The MR2 came with an old Autometer boost gauge in the A-pillar. I dig it - it matches the age of the car, it lights up with a subtle green glow when the headlights are on, more or less matching the interior lighting, and it's much easier to see in peripheral vision than the stock gauge (which isn't accurate or useful with, like, real numbers or anything anyways).

    It has always read 1psi with the engine off. I gather this means it's a mechanical gauge because it doesn't sweep when I start the engine. Doing some reading tonight, apparently that's not uncommon with Autometer mechanical gauges. What I can't determine is whether the 'active' readings (boost and vacuum while driving) will be off at all, by a linear amount, or by a percentage amount. This is in the "magic happens" realm of turbocharged engine theory for me.

    It shows 16, sometimes 16.5 in/hg of vacuum at idle when warm, which is less than people say is normal (18-22 in/hg they say).

    On the boost side, I see max boost of about 11psi which is normal according to what I know.

    One wonders, though, if the zero value is off, maybe I'm actually only getting 10psi but also 18in/Hg of vacuum. How do I actually know if I have a real problem to investigate or just a bum gauge?

    I was looking around during/after my idle investigations for where the boost gauge is getting its reading from. I can't find sh_t. I'd think there'd be vacuum line coming through the firewall somewhere and a T in another line...

    Making me think about adding a different (electric?) boost gauge to my future upgrades list. But I really really like how the Autometer in there doesn't look out of place at all. And no stupid bright LED illumination at night. No, this car gets incandescents all around.

    Edit - the other thing I found funny, getting the cats warmed up for the smog test, was how the turbo lost boost during a quick shift. It seemed to lose too much too fast, but again I don't know what's normal. Scenario: full throttle in 3rd gear, full boost, a rapid shift to 4th gear going straight to full throttle again (no lollygagging!), and it seemed to take a full second or two for the boost to creep from ~5psi back up to 11psi. Seems like a rapid loss of boost being off throttle for such a short time. One would think the turbo would have some more inertia to it. Or something.
    Last edited by CudaMan; December 14th, 2016 at 11:13 PM.

  4. #694
    Senior Member
    Join Date
    Jan 2014
    Posts
    10,171
    It's been a while, but my recollection is the Autometer boost gauge in the '90 SPG also was off by 1psi at rest. I didn't notice the problem when it was new, so I'm not sure what the nature of the problem is, but 1psi is hardly worth worrying about. That's the difference between a cold day and a warm day as far as the engine is concerned.

    The sweep thing is kinda just a gimmick they do with stepper motor controlled gauges. It's possible that the gauges self-calibrate their limits on startup, but frankly I think it's a gimmick. Not all electric gauges are stepper motors. It's unlikely any single gauge technology is universally more accurate than another, but realistically mechanical gauges are probably the most accurate, since there is no abstraction through sensors or voltage, what happens over there is reflected over here directly by the same force. Between traditional electric and steppers? I dunno - the way the sensors work is typically completely different and whereas a legacy gauge will generally use voltage to move a needle, steppers will interpret a reading and then display it. You get into resolution issue, calibration issues, etc. I dunno. For boost/vacuum, I'd go mechanical every single time whereas with fluids you kinda don't want to have to pump them into the cabin if you don't have to.

    Does the 2 have a bypass/diverter valve? If that's not working you'll get exactly the behavior you described. I assume due to its age it has a traditional wastegate actuator and not some fancy electronic gizmo like a new car, so that's probably not on the table.

  5. #695
    I'm not sure what you mean by a bypass/diverter valve. It has a "BOV" that's fairly quiet. It has a wastegate to control boost.

    -

    Here's something from the 350Z files that I'm too dumb to figure out.

    So the 350Z has a differential vent tube that goes up, to the left, and into the rear subframe. There's a hole in the subframe that lets this diff fluid drain out if it happens to get all the way out the vent tube.

    One would think there would be a couple scenarios where this would be likely to occur:
    1) track work, drifting, donuts, etc where the diff is getting hot and the fluid is boiling over
    2) overfilled diff

    Now I've had this diff and fluid since I got the silver 2003 in January of 2015. Yeah, it's due for a change and it's on my mental list. But here's the thing - it has never leaked to my knowledge or spilled out the vent tube to my knowledge. Until now. I can drive 2 blocks to the grocery store, come back home, and when I move the car the next day there's a small puddle of diff fluid on the ground. Why on earth would it start now? Has the fluid broken down so bad it boils over at the slightest hint of being worked? Is something partially clogging the tube and creating some kind of pressure? Wtf mate?

    I checked under the car and can't see any evidence of leaks from the diff cover, the stub axle seals, the cv boots.

  6. #696
    mAdminstrator Random's Avatar
    Join Date
    Jan 2014
    Location
    Davis, CA, USA
    Posts
    3,547
    New crack/split in the vent tube from underuse or overuse or just age? Pulled it too hard when swapping suspensions?
    Whoomah!

  7. #697
    Senior Member
    Join Date
    Jan 2014
    Posts
    10,171
    Quote Originally Posted by CudaMan View Post
    I'm not sure what you mean by a bypass/diverter valve. It has a "BOV" that's fairly quiet.
    Are you sure? It's very unlikely a blow off valve (BOV) would pass smog. It's definitely not factory.

    One would think there would be a couple scenarios where this would be likely to occur:
    1) track work, drifting, donuts, etc where the diff is getting hot and the fluid is boiling over
    2) overfilled diff
    I'd look at a damaged fitting, but it could also be fluid that is water contaminated or fluid that has been baked and suffered a viscosity breakdown. If it's puddling, I would change that ASAP - there probably isn't much to lose in there.

  8. #698
    I just don't want the same thing to happen to expensive new Redline fluid, if the problem is something else. Trying to think what else could be wrong I'd think a damaged fitting would have the leak closer to the diff housing, and not from within the subframe where the hose terminates. I'm having trouble finding a good picture of it but I imagine it's not a terribly uncommon setup.

    -

    On the MR2, I'm sure Toyota doesn't call it a BOV, they'll have some strange name for it, and it likely doesn't vent to atmosphere, so maybe bypass/diverter valve is a more accurate description. But there's something that serves a similar function to a BOV in there. Maybe you're onto something... I recall now hearing a faint fluttering BOV-type sound when jumping off the throttle in the past with this car, and I haven't heard it this week. People used to talk about aftermarket BOVs on the cars and how they were just for sound, not performance. The stock unit is apparently more than adequate at its job even at higher boost levels.

    Bit of digging shows that it's commonly referred to as the BPV and it routes air back to the intake rather than venting it. Still not sure what Toyota themselves call it.


    Maybe I'll pick up a cheap vacuum test gauge to see if my Autometer is accurate at idle. Eliminate one point of confusion.

  9. #699
    Senior Member
    Join Date
    Jan 2014
    Posts
    10,171
    Back in the day recirculating valves were typically called bypass valves (BPV), but for whatever reason more recently they've been renamed diverter valves.

    Valves that vent to atmosphere are blow off valves (BOV) are sometimes called dump valves and they wreak havoc on airflow-based fuel injection systems (VAM, MAF, etc.) and not explicitly legal on speed-density systems (MAP).

    When there is *no* valve you can damage the turbo - when the throttle valve closed any air travelling through the intake tract has nowhere to go and it will bounce back at the turbo. This can cause a fluttering sound from the air filter as air stalls out the impeller - think like blowing into a fan. Some bypass valves can have a little fssssh sound, but since the maintain a closed system they're usually pretty silent. I've definitely heard noise from recent Hyundai and Ford cars, but the XR is silent. Sometimes you can get a little hoooooo sound from older valves; most newer ones are weighted to prevent that. Blowoff valves obviously make a mess of noise as they dump an intake's worth of air out. You really have to be running a lot of air before modern diverters are overcome and you need to move to a blowoff. Older diverters could get overwhelmed at surprisingly low levels.

    On the Z, I'd just pull the vent off (it's usually just some rubber hose, maybe with a check valve at the end) and be sure it's in good shape. Make sure you can blow into the case. If all that's good, is pretty much gonna be something inside... That said, I know some Fords have congenital issues like this and there are all sorts of solutions, but since it used to work, I think it's safe to assume yours can.

  10. #700
    Maybe what I've heard before is compressor surge. It's a little faint, but it's a whistling noise that quickly steps down in pitch before going away after a second.

    I can hear the turbo spool up over my right shoulder since it's right there. Kinda neat.

    I ought to record a video of the boost gauge during a WOT 3-4 shift and see if I can figure out if it's normal. I've been hunting on YouTube but haven't found something comparable yet to see how quickly boost should build in the next gear. I imagine if the BPV isn't working right, some of the air trapped in the wrong path will slow down the turbo faster when you come off the throttle. Solution is flat-shifting I guess, but I like my clutch and transaxle just the way they are right now, thankyouverymuch.

    Looks like a new BPV is either $250 and/or discontinued. If it comes to that I'll have to buy used or see if mine can be refreshed. It apparently works in a way that the more boost you have, the tighter it seals against itself (the opposite of how a spring type BOV works). Perhaps mine is sticky from age or disuse.

    I really ought to spend a weekend just poking around the car and testing/inspecting many many things.

    Ideally I'd drop it off at Aggressive Performance or Chico Race Works and say "make it perfect!" [/Ziloid] but debt isn't my style.

    _

    IIRC on the Z when doing the subframe swap I had to lower the subframe just a bit to gain enough clearance to undo the vent hose. Don't want to do that again. I'll see what I can discover.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •