Somender singhs groove theory tried.

I don't think it needs a hotter stat, as when it's warmed up, approx 4-5 miles it drives fine, i'm just trying to tell it like it is, i know one of the claims made for this is lower combustion temps, i had trouble with that one as i would have thought that a more complete burn of the fuel would have raised temps, any thermodynamics students/experts out there can probably explain why it burns cooler or whatever, if it does burn cooler would that affect turbo performance.

Ok theory time, feel free to shoot holes in it coz that's what theories are for.

Sorry, i got half way through typing it and realised that it would actually raise engine temps lol.

Edit: About the stat, i don't know, tell me what to look for and i'll go look.

you'd have to pull it out to see. volvo orginal are 87 or 93, aftermarket are often 88 or 93.

the question is does the more complete burn put more heat out of the exhaust pipe in gas temps instead of leaving fuel lingering around the edges and rings to burn slowly and put heat into the engine.

I guess a stat that opens later: 93C

about the theory, I'm following the line of reasoning of Singh here. I'm no thermodynamics engineer but I think that when a charge has burnt completly in a shorter time it has more time to exert pressure on the piston and less time to exchange heat/energy with the head since the burningproces itself has taken shorter.

sidenote: We all know that diesels are more efficient when it comes to converting fuel to propulsion. Here in Europe many cars use highly efficient commonrail direct injected turbo-diesels. These engines are so very efficient that it is a real issue in winter temperatures, the heater only starts working after about 10 miles... many carmakers now also offer a auxilary 2nd car heater as well. Therefore: the more efficient the combustion, the cooler the coolanttemp.

I got anoter 530 in yesterday but I'm still trying to get my car running again after the tranny swap. Foo bar'ed or forgot something.

Les: Have you changed your oil since this? Another thing that's reported by everybody doing this is that the oil stays clean. Or at least it stays cleaner for longer. LOL

Anyway, it appears that some of that unspent charge also makes it's way past the rings and into the oil supply.

Janspeed said:

I guess a stat that opens later: 93C

about the theory, I'm following the line of reasoning of Singh here. I'm no thermodynamics engineer but I think that when a charge has burnt completly in a shorter time it has more time to exert pressure on the piston and less time to exchange heat/energy with the head since the burningproces itself has taken shorter.

sidenote: We all know that diesels are more efficient when it comes to converting fuel to propulsion. Here in Europe many cars use highly efficient commonrail direct injected turbo-diesels. These engines are so very efficient that it is a real issue in winter temperatures, the heater only starts working after about 10 miles... many carmakers now also offer a auxilary 2nd car heater as well. Therefore: the more efficient the combustion, the cooler the coolanttemp.

Click to expand...

at the opposite end of the spectrum are turbines, think of how hot they get and how much fuel they go through to make a given amount of power...

very cool! i have been thinking about this too. time to find a small old engine!

With a cnc machine or normall mill, you could get some pretty wicked grooves in the quench area's of the head!

edit:

acbarnett said:

at the opposite end of the spectrum are turbines, think of how hot they get and how much fuel they go through to make a given amount of power...

Click to expand...

true, the higher the temp, the more efficient....

in terms of fuel efficiency, turbines are at the far opposite side of diesels, they make alot of power for their weight but you pay dearly in fuel consumption...

Janspeed said:

I guess a stat that opens later: 93C

about the theory, I'm following the line of reasoning of Singh here. I'm no thermodynamics engineer but I think that when a charge has burnt completly in a shorter time it has more time to exert pressure on the piston and less time to exchange heat/energy with the head since the burningproces itself has taken shorter.

Click to expand...

Also not nearly an expert in thermodynamics, but I thinks that's kind of right. Since the burn is shorter and optimum pressure can be achieved during a shorter time, then ignition timing can be advanced, so there is then less time for heat transfer after ignition.

Sound good? There's probably more to it. Thermodynamics is never simple.

In ye olden days ie 70s, to time a car you'd turn the dizzy until the idle was at it's fastest and then retard 5 degrees, i'll try that tomorrow and see what it gives, while i'm at it i'll try it to 30 degrees static advance and see if i can induce light knock.

mikep said:

It seems the other way to me. Power is the thing we want, heat is the byproduct. More efficient burn= more heat byproduct.

Click to expand...

true but not nesc. transfered into the cooling system.

I am not due an oil change, i only do about 5500 miles a year and change every 6 months.

I got the head chopped tonight, even with that deep groove i did there's still 4-5 mm of metal left at the thinnest point, pics tomorrow.

Will check the stat tomorrow as well, sorry i can't do any tonight, my busted bits are complaining.

Janspeed said:

I

sidenote: We all know that diesels are more efficient when it comes to converting fuel to propulsion. Here in Europe many cars use highly efficient commonrail direct injected turbo-diesels. These engines are so very efficient that it is a real issue in winter temperatures, the heater only starts working after about 10 miles... many carmakers now also offer a auxilary 2nd car heater as well. Therefore: the more efficient the combustion, the cooler the coolanttemp.

Click to expand...

Diesel engines also are made with a good bit more mass to deal with the stress of uncontroled combustion. Generaly the coolant capacity is at least 30% larger than a gas motor of similar displacement. Both of thse contribute to longer warmup times.

In the warmup fase the engine and coolant are cold, if a diesel was producing so much waste energy the head would heat up very fast after starting the engine from cold > the thermostat would open fast too > the heat would start circulating through the cooling system relatively fast too. > heater would be giving of heat in the interior fast to.

But wait, it doesn't!
the heater stays cold for a considerably longer time then in a petrol/LPG-engined car. I've driven many Diesel cars, I just know from experience.
Once warmed up the Diesel with it's heavy block needs a bigger cooling system but before it's warm enough to need that cooling capacity a long time has passed driving the car. It really takes a long time to get a Diesel at optimal operating temperature.

so...

if you (les) are a scientifical type person and not a placebo type person.

how about some MPG figures.

warming up taking longer could mean a drop in efficiency... combustion not getting as hot.

im with mike P.

more heat=more efficiency.

this whole diesel thing:

diesels are efficent because of their high compression and that they USE That high compression... diesels have no throttle plates.

the throttling process of a gasoline engine makes the effective compression pretty darn weak under most driving conditions.

I understand the idea (inferior and Kenny) about where the heat goes, but my idea, and the other ideas, are mostly conjecture at this point. So don't side with me yet.
Cool discussion.

hmm...i'm not sure how i feel about the slower warm-up versus efficiency thing. i dont think it's as cut and dry as less heat = less efficient.

if the burn is faster, then i wouldn't think it would transfer as much heat to the head and piston. but it's thermodynamics, all i know for a fact is that you can't win, and you can't break even.

740Weapon said:

so...

diesels are efficent because of their high compression and that they USE That high compression... diesels have no throttle plates.

the throttling process of a gasoline engine makes the effective compression pretty darn weak under most driving conditions.

Click to expand...

Not quite correct. Diesels are effiecient because they are a lean burn engine - very little fuel goes out a well running diesels tailpipe. If gas engines ran at the same a/f ratios you'd have knock knock bang!

acbarnet said:

in terms of fuel efficiency, turbines are at the far opposite side of diesels, they make alot of power for their weight but you pay dearly in fuel consumption...

Click to expand...

Also not correct - a recirculating turbine is by far the most efficient petrol based engine out there but they lack operating range meaning all the work is done at 90 to 100% and in some cases 98% to 100% Throttle and turbine speed.

End threadjack

Renny

Renny_D said:

Not quite correct. Diesels are effiecient because they are a lean burn engine - very little fuel goes out a well running diesels tailpipe. If gas engines ran at the same a/f ratios you'd have knock knock bang!

Renny

Click to expand...

diesels only "lean burn" at idle/cruize.

and operate by compression ignition. i.e. there isnt a "flame front" so to say. any fuel injected around TDC on a diesel spontaneously ignites.

under WOT diesels go to the same type of a/f ratios as anything else.

gasoline engines will not ignite a fuel mixture at a diesel's idling a/f ratio.

the "lean burn" efficiency gain is because compression ratio up=efficiency up. and no throttle plates mean very high compression at all times.

gasoline engines do not "waste" fuel in the tail pipe.

Fun Fact: in thermodynamics the gasoline cycle is more efficient then the diesel cycle.

its the diesel's higher compression ratios and real world operating conditions that make them so efficient.

engine stuff

740weapon is totally right... I was just reading an engine design book and noted the same things. otto cycle (four stroke spark ignition) engines are more efficient than diesels when unthrottled... but in actual use they have to be throttled which reduces their efficiency (especially for cruising). they are also limited by knock so need to run lower compression ratio's than optimal. the lean combustion of diesel's actually hampers their efficiency. if you've seen a graph of fuel efficiency vs A/F ratio you'll see that the most efficient combustion occurs at a specific point, and this applies to diesel's as well.

also acbarnet is right about turbines. they are used in planes because they are very light for their power output. in terms of efficiency otto cycle and diesel engines are better. combined cycle steam/gas turbines can be more efficient, but these are significantly more complex, mostly used in power plants. you can do combined cycle piston engine/steam as well... although i've never heard of this being done in a production engine.(bmw has a system in development that sounds cool if you want to google it)

as for these grooves... lets see some hard data...

james