Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Internal Combustion Engine

ciechanow.ski

Post reply on HN
Print view View original

101–110 of 415 posts

Re: Internal Combustion Engine

#101

Post by mgarfias »

specialp wrote: post #41
tmh88j wrote: post #32

Earlier quoted context omitted.

Nice! What engine did you build? >The distance between a crank bearing or rod bearing is less than 2 thousandths on modern engines. A small amount of oil in that tiny space is all that keeps your engine from having metal on metal seizure. The BMW S65 and S85 engines are prime examples of what happens when the wrong tolerances are chosen. I can't think of another engine family where rod bearings are considered a maint…

I built an LSX (Aftermarket GM) iron block engine (V8 LS) for a CTS V. I had to get some very precise tools (Have to measure to 10,000ths) or they were useless for bearing clearances and verifying cylinder diameters. My cylinders were 4.155 bore, and the bearing clearances were around 1.8 thousandths. Forged pistons, rods and crank. I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the…

17-18 thou here on my LS6 on the rods. 23-24 on the mains. I'd like to see tighter on the mains, but not sure if its worth ordering another set of bearings and using 1/2 of them to tighten up 1/2 a thou like i did on the rods.

what amazes me is the cam lifts we're running these days. I'm running .646"/.649". In the 90s .500" was big for a street motor, and only full blown race motors were running whats normal now.

Re: Internal Combustion Engine

#102

Post by tmh88j »

zeusk wrote: post #83
tmh88j wrote: post #32

Earlier quoted context omitted.

Nice! What engine did you build? >The distance between a crank bearing or rod bearing is less than 2 thousandths on modern engines. A small amount of oil in that tiny space is all that keeps your engine from having metal on metal seizure. The BMW S65 and S85 engines are prime examples of what happens when the wrong tolerances are chosen. I can't think of another engine family where rod bearings are considered a maint…

Any race or high power engine, especially those that rev quite high will need rebuild - not just in bottom end but often with piston rings and valves as well. You don't really hear about those other engines much because their buyers understand that a race engine needs more maintenance than any other road car. Also, not beating on the engine until oil has warmed up to temp will elongate the bearing lifespan quite a bi…

The S65 and S85 are road car engines, not racecar engines. They're also hardly BMW's highest performing motors. Even Dinan built engines don't suffer from that problem.

Re: Internal Combustion Engine

#103

Post by mgarfias »

mywittyname wrote: post #91
tmh88j wrote: post #55

Earlier quoted context omitted.

>I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the work so I did a lot of research and did it all myself I love working on cars so I totally get wanting to do that, but why didn't you trust someone else to do the work? There are probably more reputable LS builders across the US than any other engine family.

It helps that they are abundant (in the hundreds of millions units produced), have been in use for decades (since the mid-50s), and are simple to work on (as evidence by the OP randomly learning to machine one). As cool as 2-atom thick plasma transfer wire arc cylinder liners are, that's not something which will ever be available to a layman.

I really doubt the OP did the machine work himself, those tools are not affordable for just using once or twice. Buying bore gages and mics however is totally doable.

And no, the LS motors have been in use since '97. Including the gen1/2 small blocks doesn't count, there are no shared parts between them.

Re: Internal Combustion Engine

#104

Post by distortedsignal »

londons_explore wrote: post #45
kingsuper20 wrote: post #31

Earlier quoted context omitted.

>So one would think that when EVs reach the same scale they will be significantly cheaper than ICE vehicles. I expect that batteries are the only hangup, there's probably not that much magic left in an electric motor. Additional cost for regen brakes of course. I agree on the amazing cheapness of it all if you stick with the common stuff. That, along with the low cost of flat panel TVs is a miracle of the modern age.

> Additional cost for regen brakes of course. Regen braking has no physical cost associated - it's pure software/firmware. The exact same hardware that is used to power the car forwards can be used for regen braking. It can be as simple as a single negative sign in the code to cause the phase to be 180 degrees out, current to flow backwards, torque to go the other way, and the battery to be charged instead of dischar…

> Regen braking has no physical cost associated - it's pure software/firmware.

I think this is a slight exaggeration.

The way I understand regenerative braking is that you (effectively) run your AC generator in reverse of what you would in order to accelerate in the direction of motion and then take the current generated by that, rectify it to DC, and use that current to charge a battery. The energy in the system is provided by the back EMF induced in the stator by the magnetic field generated by the motor rotor. I agree that the AC generator is going to stay the same, but I think there's specialized hardware needed for the rectification and charging cycles. At the minimum, you need a more specialized battery and battery management system to make sure that you're balancing the charge across the cells in your battery.

Re: Internal Combustion Engine

#105

Post by B1FF_PSUVM »

kingsuper20 wrote: post #31
specialp wrote: post #15

I just built an engine for my car. One thing I gained an appreciation for was how CHEAP cars and engines are. There's probably nothing else with as precise machining that is as inexpensive. Engine cylinders are honed to accuracies that are less than 1 thousandth of an inch. Crank journals as well and rod journals. This is all precise machine work with metal. I use inches here because in machine work thousandths of in…

>So one would think that when EVs reach the same scale they will be significantly cheaper than ICE vehicles. I expect that batteries are the only hangup, there's probably not that much magic left in an electric motor. Additional cost for regen brakes of course. I agree on the amazing cheapness of it all if you stick with the common stuff. That, along with the low cost of flat panel TVs is a miracle of the modern age.

> the low cost of flat panel TVs is a miracle

That's really astounding, I just looked at a 55 inch brand name 4k TV going for 400 bucks retail.

Guess it's the same logic as cramming more CPU, etc. into the usual couple hundred sq. mm chip. But you get more CPU for the same money and chip size, which is not as spectacular as more screen size for less money ...

Re: Internal Combustion Engine

#106

Post by esaym »

tmh88j wrote: post #55
specialp wrote: post #41

Earlier quoted context omitted.

I built an LSX (Aftermarket GM) iron block engine (V8 LS) for a CTS V. I had to get some very precise tools (Have to measure to 10,000ths) or they were useless for bearing clearances and verifying cylinder diameters. My cylinders were 4.155 bore, and the bearing clearances were around 1.8 thousandths. Forged pistons, rods and crank. I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the…

>I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the work so I did a lot of research and did it all myself I love working on cars so I totally get wanting to do that, but why didn't you trust someone else to do the work? There are probably more reputable LS builders across the US than any other engine family.

It sounds like he wanted some very precise work done. Quality in the blue collar trades has gone to nil in the last decade. And if you do find someone that is very detailed and "by the book" level of quality, you are going to pay 3X the normal labor rate. For instance, this is a performance transmission shop [0] that regularly takes apart "precision" rebuilt transmissions only to find they were not done right at all.

[0] https://youtu.be/aI5iO2YSHMs

Re: Internal Combustion Engine

#107

Post by elihu »

esaym wrote: post #96
Robotbeat wrote: post #86

Earlier quoted context omitted.

Tesla already uses aluminum for power cabling because it’s cheap and lighter weight. Tesla Model S were induction motors (at first at least) with no rare earths, and Tesla is partnering with CATL for lithium iron phosphate batteries in lower cost versions of, if I believe, Model 3 and Y.

Note to replace copper wiring with aluminum, you have to go up at least one gauge size.

Yeah, aluminum is a worse conductor so you need thicker cable. It's less dense, though, so I think it usually comes out as being lighter. Thicker cables can be more inconvenient. I think aluminum also tends to have more problems with oxidation causing too much resistance at electrical contacts.

I think for motors generally you just end up with a larger motor for the same amount of power.

Re: Internal Combustion Engine

#108

Post by outworlder »

rsj_hn wrote: post #68
dahfizz wrote: post #42

Earlier quoted context omitted.

This sparked my curiosity... Currently gasoline has about 50x more energy per unit weight than a tesla battery pack. Battery energy densities have tripled in the past 10 years. Keeping on that pace, it would take over 30 years for batteries to be competitive with gas. When you account for the astoundingly bad efficiency of ICE, though, the gap in usable energy decreases. This is why a tesla can go 300+ miles with a b…

The Tesla can go 300 miles by making it light, aerodynamic, brakes that recharge the battery, not turning on the heater, etc. Yes, it's a significant engineering accomplishment, but in the heavy long haul world when analyzing break-even points what matters is range improvements due to an increasing energy/weight ratio, not range improvements due to reducing air resistance and inertia. This is because the form factors…

> by making it light

If there's one thing that EVs are not, is "light". Model S ranges from 4,561 to 4,941 lbs. A model 3, 3,648 to 4,250 lbs. A Nissan Leaf - 3,538 to 3,946 lbs.

In comparison, a Honda Civic weights 2,771 to 3,012 lbs.

Regenerative breaking is nice but it's very dependent on the particular drive and terrain. Heaters are power hungry as there is very little waste heat that can be used (again, due to the high efficiency), unless they are heat pumps.

The main reason they can go so far with so little energy is the efficiency of electric motors.

> as hydrogen has similar power/weight characteristics to gas

No it doesn't! It has horrible energy density per volume, compared to any gas or liquid fuels. You can improve this by using high pressures (energy loss) or cryogenics (even more energy loss). But it's pretty bad to begin with. Turns out that the best way to store hydrogen is by adding some carbon atoms to it.

Re: Internal Combustion Engine

#109

Post by mgarfias »

kingsuper20 wrote: post #81
specialp wrote: post #41

Earlier quoted context omitted.

I built an LSX (Aftermarket GM) iron block engine (V8 LS) for a CTS V. I had to get some very precise tools (Have to measure to 10,000ths) or they were useless for bearing clearances and verifying cylinder diameters. My cylinders were 4.155 bore, and the bearing clearances were around 1.8 thousandths. Forged pistons, rods and crank. I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the…

Very cool. Although I own an LS, I've never touched an LS. The Sloppy Mechanics guy is impressive though. Since a short block is mostly just a short block, I'll be interested in seeing if LS heads/intake manifold/headers takes off in the SBC community.

Huh? What do you mean "takes off". Do you mean do we build LS motors now instead of gen1/2 SBCs then yes.

If you mean "do the LSx heads drop onto a gen1/2 SBC", then no, not at all. only thing common between them is the cylinder spacing. The LS uses 4 bolts per cylinder like a ford, instead of 5 like the SBC, the firing order is different, the valve layout is different (ports are symmetric vs mirrored), etc.

Re: Internal Combustion Engine

#110

Post by Grazester »

specialp wrote: post #41
tmh88j wrote: post #32

Earlier quoted context omitted.

Nice! What engine did you build? >The distance between a crank bearing or rod bearing is less than 2 thousandths on modern engines. A small amount of oil in that tiny space is all that keeps your engine from having metal on metal seizure. The BMW S65 and S85 engines are prime examples of what happens when the wrong tolerances are chosen. I can't think of another engine family where rod bearings are considered a maint…

I built an LSX (Aftermarket GM) iron block engine (V8 LS) for a CTS V. I had to get some very precise tools (Have to measure to 10,000ths) or they were useless for bearing clearances and verifying cylinder diameters. My cylinders were 4.155 bore, and the bearing clearances were around 1.8 thousandths. Forged pistons, rods and crank. I had cracked a cylinder/piston on the original LSA. I did not trust anyone to do the…

Why did you go iron block for your build? Is it that your were afraid you cracked the block again? How did you do that in the first place. Are you running any boost on this engine?
Post reply on HN