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I'm still a bit confused and probably misunderstand something, the piston in a budack still travels the same distance right? it's just the cylinder gets closed at say... 70% of the stroke? So if I imagine a cylinder in my car (at WOT) will draw in 100 grams of air in ordinary operation, under the budack cycle the valve closes at 70% of the stroke and draws in 70 grams of air, but the piston keeps going down, reaches BDC and comes up and compresses the 70g of air and fuel mix. If my cylinder had a throttle opening of 70% and drew in 70g of air and fuel but this time the valve stays open for the whole down stroke, that to me seems to be the same thing? Obviously those are numbers I pulled out of my rear end, I don't know if my car draws in 100g of air and I don't know that closing the valve at 70% duration or restricting with a throttle at "70%" will equally deliver the exact same air fuel mix with those specific values, but it seems like you could have the same mass of air in a cylinder with either strategy, i don't understand how a partial cylinder fill from either one actually gives you the separate expansion ratio, and the other one doesn't?
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Feb 3, 2021 18:42
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Crankit posted:I'm still a bit confused and probably misunderstand something, the piston in a budack still travels the same distance right? it's just the cylinder gets closed at say... 70% of the stroke? Yes, but with the budack cycle the piston has to go all the way down (reducing the intake charge pressure) and then move part way back up to get back to manifold pressure. Compression only starts at that point, so the ratio ends up lower. The exhaust valve stays closed for the whole expansion cycle, so it ends up expanding more than it was compressed. The budack's variable compression ratio happens in addition to throttling, so it gives the computer more variables to work with for maximizing economy and providing power when needed. eta: Here's the PV diagram of an Otto cycle:  The work output is the area inside the curves. An Atkinson or budack cycle engine will have slightly lower P values for 3 and 4, and larger V values for 5 and 6. The net effect is to have a greater area between the curves, or more work output for the same amount of fuel. Deteriorata fucked around with this message at 19:48 on Feb 3, 2021 |
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Feb 3, 2021 19:31
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I'm with Crankit, and I'm also not satisfied with the explanations so far and am confused about how this works. Forget compression ratio for a second and just think about cylinder pressure. At the top of a compression stroke, without changing cylinder geometry or stroke length, cylinder pressure is a function of fuel-air charge mass. Drawing in less fuel-air before compression gives lower pressure. These explanations of the budak cycle seem to suggest that how you arrive at the same charge mass makes a difference. How does the method or mechanism of limiting the mass of fuel-air inside the cylinder during compression affect engine performance? The throttle and the intake valve both control flow of intake charge, why does using the intake valve to limit charge mass "change the compression ratio," but using the throttle valve to do the same thing doesn't?
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Feb 3, 2021 19:45
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RadioPassive posted:I'm with Crankit, and I'm also not satisfied with the explanations so far and am confused about how this works. It's not about the amount of fuel, it's about the amount of work you extract from that fuel when it's burned. The Atkinson cycle increases the efficiency of the engine, giving you more power from the same amount of fuel.
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Feb 3, 2021 19:52
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Now I'm wondering what happens if you do a budack with a turbo/supercharger.
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Feb 3, 2021 19:55
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So I'm getting ready to replace the thermostat on my 2005 Camry V6 280,000 miles.... Any guesses wtf is going on here?
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Feb 3, 2021 19:59
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Deteriorata posted:giving you more power from the same amount of fuel. But the only thing that's changed is how we arrived at that amount of fuel. The burning and the power-making strokes are the same. How does budak's changes to the intake stroke make more power from the same amount of fuel?
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Feb 3, 2021 19:59
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RadioPassive posted:But the only thing that's changed is how we arrived at that amount of fuel. The burning and the power-making strokes are the same. How does budak's changes to the intake stroke make more power from the same amount of fuel? Compressing the air/fuel charge takes energy. Compressing it less and expanding it more results in more net mechanical energy for a given mass of fuel. https://en.wikipedia.org/wiki/Atkinson_cycle The budack system is another way of achieving the effect without the messy mechanical systems on the con rod.
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Feb 3, 2021 20:05
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Action Man posted:So I'm getting ready to replace the thermostat on my 2005 Camry V6 280,000 miles.... Any guesses wtf is going on here? I would guess somebody put a stop leak product in the coolant. It works by hardening on exposure to air, so if a bunch of coolant leaked out it could end up like that.
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Feb 3, 2021 20:08
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Could be. Could also just be years of buildup from Toyota red coolant coming out of a pinhole leak and drying on the block. I had a big goopy green-yellow mess on one of mine from regular coolant doing the same thing.
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Feb 3, 2021 21:16
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Yeah that's just Toyota red coolant leaking from the thermostat housing. Make sure you replace the housing gasket. My Matrix had the same poo poo going on.
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Feb 3, 2021 21:38
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Ford retractable running board question (2018 expedition) - how do I get them to work? Youtube videos seem to suggest just hosing the poo poo out of the joints with a PB blaster or equivalent, then WD-40 or equivalent, then finish with a spray lubricant. Is that basically it? Is there a secret?
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Feb 4, 2021 01:28
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Another thermostat (I hope) question. 1985 Toyota pickup. 103,000 miles. Gets driven once or twice a week. On the first drive after its sat a few days, about 10 minutes into driving there's suddenly the sound of rushing water from behind the dashboard. About 3 seconds later the engine temperature spikes and then comes down to normal after about 30 seconds. I'm assuming the Thermostat is getting stuck closed.... does that make sense? or should I be thinking something else? 
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Feb 4, 2021 03:17
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Action Man posted:Another thermostat (I hope) question. 1985 Toyota pickup. 103,000 miles. Air in the cooling system definitely. Thermostat could be completely dry up until it's ready to overheat and then finally get some coolant on it and opens. I'd start with bleeding the system and getting it completely filled again and see what happens. If it quickly ends up with air in it again....we're gonna need to talk about nasty things like head gaskets. But in the mean time changing the thermostat and pressure cap o the radiator while you bleed the system properly will hit the top 3 things that could be a cheap and easy fix.
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Feb 4, 2021 03:25
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Motronic posted:Air in the cooling system definitely. Thermostat could be completely dry up until it's ready to overheat and then finally get some coolant on it and opens. Just out of curiosity- is this the sort of thing that can be fixed by just "burping" your coolant with a coolant funnel like this and just topping up the coolant system? Or does the entire coolant system need to be dumped, flushed, refilled with new coolant, AND burped in order to properly eliminate air in the cooling system?
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Feb 4, 2021 18:02
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You could probably burp it out, yeah. That funnel would make it easier but I haven't used one in ... poo poo, like 16 years. Maybe I'll buy one to make the next one easier 
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Feb 4, 2021 18:44
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melon cat posted:Just out of curiosity- is this the sort of thing that can be fixed by just "burping" your coolant with a coolant funnel like this and just topping up the coolant system? Or does the entire coolant system need to be dumped, flushed, refilled with new coolant, AND burped in order to properly eliminate air in the cooling system? Yes, that's all you need to do. Or find the bleed valve that may or may not be in the system and use that. Or get the pressure cap as high as possible (jack that side of the vehicle up) and keep filling it with coolant until the t-stat opens, keep topping off for a while to get it through the heater core, etc and put the pressure cap back on before it boils and before you turn the engine off. What works best is heavily dependent on the vehicle, but I'd found those coolant funnels to pretty much be the cheat code for just about everything.
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Feb 4, 2021 19:47
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You can also give the upper rad hose a few good squeezes while you're filling/waiting to help it along. edit: Just wish they would all come with bleeder screws.
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Feb 4, 2021 19:59
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C-Bangin' it 
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2014 Mazda 3 Sedan, manual, brakes question. So the rear right wheel started making a horrible scraping/grinding sound so I bought new pads and rotors all around figured it was time. Yesterday I replaced the rear right rotor and pads but ran out of daylight and don’t have a garage so I had to stop there planning on doing the other side tomorrow (today). But last night after replacing just the one side I took it for a test drive around the block and after pumping the brakes and all that it ... somethings definitely off. It takes much longer to stop. Definitely not drivable atm because I slammed in the brakes a few times and it was way too slow to stop. I was hoping maybe it was a balance issue or something and replaced the other side (rear left) pads and rotors. Same problem. I’m going to take the rear right apart again tomorrow to see if I did something glaringly wrong but idk. Also maybe noteworthy, the side that had the grinding, the outside pad was worn down to past no pad (because I’m a horrible and irresponsible person) but the inner pad still had more than half left. Weird? Tldr: Did my brakes on my own now car don’t stop good.
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Feb 5, 2021 01:10
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yamdankee posted:2014 Mazda 3 Sedan, manual, brakes question. The caliper sliders on that corner are sticking. If you haven't you should clean them up and lube. Keep in mind, it is possible to use too much lube. If the inner pad was worn out, while the other side was still ok, then it would be the piston inside the caliper. Or possibly the parking brake mechanism. E: thats only why your one pad was excessively worn while the other wasn't so bad. Don't know why your braking sucks. Bleeding the brake system might help though.
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Feb 5, 2021 01:25
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So is the pedal mush? How did you compress the rear pistons? Is the parking brake within the rotor hat?
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Feb 5, 2021 01:45
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wesleywillis posted:The caliper sliders on that corner are sticking. If you haven't you should clean them up and lube. Keep in mind, it is possible to use too much lube. Thank you for this! I will get some lubricant to address that. This would also explain why the pads in the other side today weren’t actually worn out. It was this problem that wore out one brake pad quickly and made me say time to buy all new brakes! ColostomyBag, yes the brakes are mush. And I’m trying to Google what a caliper with the emergency brake in the hat looks like but I’m not seeing anything clear. All I see in the caliper is the main piston and nothing else. I used the cube tool to push and twist the piston back. How many turns before I googled you have to PUSH and twist at the same time to make it depress I will not disclose. 
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Feb 5, 2021 02:04
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yamdankee posted:Thank you for this! I will get some lubricant to address that. This would also explain why the pads in the other side today weren’t actually worn out. It was this problem that wore out one brake pad quickly and made me say time to buy all new brakes! If you had to twist the piston back, then its not a "drum in disc" style parking brake. My Corolla has that style rear caliper, but once I'm done that, I just hit the brake pedal a few times and the piston pops back out to roughly the appropriate spot. I don't know if thats the same with Mazdas of that vintage. My old Protege had a little gear in the back of the piston that I had to turn with an allen key to retract the piston and then to turn it back out, once the pads were replaced. Thats probably not the case with your car but I don't know for sure. E: When you pull up the parking brake does it come up really easily? Another more time consuming way to get the pistons out of the rear calipers on my car is to yank the parking brake up and down a bunch of times till the brake pads just come in to slight contact with the rotor. But again, thats for my car, not yours. Its something you can try anyway, if you feel it getting tighter, then try going for a test drive and see if that helps. wesleywillis fucked around with this message at 02:20 on Feb 5, 2021 |
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Feb 5, 2021 02:15
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Pedal feeling like mush and being really unresponsive sounds like air in the lines to me, I got that once by being a dummy and taking out the banjo bolt to make space, then being unable to take off my (coincidentally) cross-threaded calipers. Bleed the lines and see how they are after that.
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Feb 5, 2021 02:25
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Took the car out and yanked the ebrake up a ton and no change.  I’ve never bled brakes before. I watched a YouTube video and you gotta get a brake bleeder thing with a catch can with a line and do them diagonally in specific order and all that? Jeez I was just trying to make bad noise go away. Can I just take it to a shop and ask them to bleed/flush my brake fluid? Any shame in that? And then I can do the front ones? Also, not that I’m doubting just curious, why would air in the line show itself after replacing basically one brake pad and rotor? yamdankee fucked around with this message at 03:17 on Feb 5, 2021 |
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Feb 5, 2021 03:14
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Unless there's been a major change I'm unaware of, e-brakes are actuated by cables, and not the hydraulic system. As posted up-thread, it sounds like you have at least one stuck caliper. The only way air gets into your brakes is if the system is opened, either by opening a bleeder or removing a hose. Or, if the fluid in the reservoir is all drawn in and air gets sucked in after. If none of those events have occurred, check and be certain your claipers are all functioning normally and are not bound up.
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Feb 5, 2021 04:09
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quote is not edit. Here's a picture of the last time I refurbed my brakes (2016)
PainterofCrap fucked around with this message at 04:22 on Feb 5, 2021 |
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Feb 5, 2021 04:09
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I'm still brainstorming replacements for my offroad minivan. I want nominal 4WD of some kind, fake electronic bullshit is probably ok for my needs. But I need to be able to comfortably sleep in the back. So I went to a dealership and tried laying down in the back of some cars! I was surprised that I might be able to pull this off with a RAV4. It's somewhat small and I'd need to lay a bit diagonally. It would really suck to be stuck inside all day during a storm. The tradeoff is that it's much smaller than the Sequoia. Also cheaper, and there's a lot more of them for sale. The Highlander was definitely not happening with the 3 row seating. It would be a big carpentry project to make it sleepable. Subaru Outback, Forester: are they all CVTs? That's bad, yeah? Anyone else have some good ideas? Or bad ideas I should avoid, heh?
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Feb 5, 2021 05:58
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ryanrs posted:I'm still brainstorming replacements for my offroad minivan. I want nominal 4WD of some kind, fake electronic bullshit is probably ok for my needs. But I need to be able to comfortably sleep in the back. Subaru Baja with a cap
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Feb 5, 2021 06:34
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Charles posted:Subaru Baja with a cap I thought you were joking, but holy poo poo: you can fold down the back seats and a door opens connecting to the bed. That's amazing!
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Feb 5, 2021 07:28
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My aunt had a RAV4 for many years. I can't recall what she has now but it may actually be her third RAV4, I know she got a second one in between her current car and the first one. The first one was the one I worked on a lot, the only real issues it had were rust which isn't your problem at all. I'd recommend them, given my experience working on them in the past. I'd take nearly any Toyota over nearly any Subaru, tbh, having worked on neglected Toyotas and owned 4 Subarus.
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Feb 5, 2021 07:40
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It was sort of a joke answer -- they're quirky vehicles and they're getting expensive and hard to find, and like said, a Toyota would be more reliable. Still, they're cool. Get a naturally aspirated one and change the head gasket and timing belt right away 
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Feb 5, 2021 07:54
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ryanrs posted:I'm still brainstorming replacements for my offroad minivan. I want nominal 4WD of some kind, fake electronic bullshit is probably ok for my needs. But I need to be able to comfortably sleep in the back. You only sticking with new cars? I'm with kastein in that I'd take Toyota over anything else to begin with. After doing general maintenance on varions Japanese vehicles and living with a bunch of old ones, wife and I have become 'Toyota People'. If you're going used there are a lot of, and they are expensive for what they are, 4Runners around and those should be able to sleep comfortably in when needed, though keep in mind I'm 25 years behind 4Runners are ubiquitous for doing the literal thing you are doing with your vehicle, they are everywhere, and reliable. I mean we're talking Highlanders, Rav4s and Sequoias so it seems like the 4Runner should be in the running as far as size and cost is concerned.
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Feb 5, 2021 08:02
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PainterofCrap posted:Unless there's been a major change I'm unaware of, e-brakes are actuated by cables, and not the hydraulic system. I suggested that as a possible course of action because on my (not mazda) car, when I change the rear pads, and screw the pistons back, cranking the parking brake lever on the caliper screws the piston back out. Although, it IS much easier to just apply the brake pedal once everything is back together and the pistons will go out on their own. I figured it wouldn't hurt for the goon to try. Fake edit: I think newer 3s have a hydraulic ebrake, but IIRC its electrically actuated.
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Feb 5, 2021 12:26
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ryanrs posted:Subaru Outback, Forester: are they all CVTs? That's bad, yeah? Only randomidiot fucked around with this message at 17:21 on Feb 5, 2021 |
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Feb 5, 2021 17:07
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KakerMix posted:You only sticking with new cars? Oh god, no. I'm going to destroy this vehicle by driving it into ditches and trees and poo poo. And I want to spend less than $10k. Right now I'm going to dealers just to get a sense of size, see how the seats work, try lying down in back, etc. But the actual purchase will probably be off craigslist. KakerMix posted:If you're going used there are a lot of, and they are expensive for what they are, 4Runners around and those should be able to sleep comfortably in when needed Yes that is a good suggestion. I'll try out one of those, too. (I have never paid any attention to truck and SUV models, so I barely know which is which.) ryanrs fucked around with this message at 19:55 on Feb 5, 2021 |
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Feb 5, 2021 19:51
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Wow, the 4runner looks like a much better match for what I want to do than the RAV4 or Sequoia.
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Feb 5, 2021 21:22
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It probably is, TBH. Also I'd just like to note how funny I think it is that two XJ guys are telling you to buy a Toyota.
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Feb 5, 2021 22:07
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I only ever offroad alone, so I definitely prefer something reliable. I have good radio gear, so I'm not going to die in the wilderness. But a disabled vehicle would really suck.
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Feb 5, 2021 23:00
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Is there a thread for trucks
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Feb 6, 2021 04:36
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