GMmexican

iTrader: (7)

engineer mike please stop calling the ls-1 a "350" .....this isnt opti-spark land

racer7088

HAHAHAHAAHA! I am talking about reality here! Not fantasy land!

With 4 cams and 32 valves and 32 valvesprings and 6 drive or driven chain or belt wheels and at least two but usually 4 chains and all the associated bearings and seals that eat up power as well as the extra oil pump capacity and oiling to take care of all this and control all the chains, a 4V DOHC V8 has much more frictional losses than a single cam pushrod V8 does period.

All the extra DOHC valvetrain mass adds some rotating inertia as well on top of that. The DOHC's smaller individual valves can be lighter and go to higher rpms because of that but they have more not less friction with double the number of valve springs and double the number of valve stem seals and followers etc. You haven't ever seen motored engine tests of multivalved engines vs a pushrod engine. It's no small difference.

4V DOHC allows more rpm and better breathing and cam timing with little to no real overlap for better emmissions and that's where they are superior to the pushrod stuff. They are great for those reasons but the extra cost and complexity and weight and drag are their downsides. This is not new knowledge to any of the engineers that work in this field.

engineermike

With 2 sig fig's the LS1 IS a 350.

engineermike

That's a good point, but keep in mind that DOHC with direct-acting bucket lifters require less than 40 lb seat spring pressure, so you get alot back there.

engineermike

Sure, but put the taller gear with the smaller engine, and the manifold pressure goes even higher and losses are further minized. The only downside is that a) you have to keep it out of power-enrichment with the calibration and b) it will be pretty "soggy" in roll-on response, but that's the compromise you have to make.

This is true, but I'd rather see more small-displacement 4v V-8's rather than switching us all over to 4-bangers. It's been documented that the 4v 4.6 gets the same mileage as the 2v 4.6. Also, keep in mind that my arguement has been that 4v is superior to 2v - it just so happens that the 4v arrangement geometrically fits better with DOHC. Of course, actuate them with pushrods and you then have to use much higher spring rates and the friction goes up accordingly.

1) Container ships, 18 wheelers, and trains generally use diesel engines. Diesel engines do not have a throttle blade, so they do not have vacuum in the manifold. No vacuum in the manifold means that the piston doesn't have to work against a vacuum during the intake stroke. This equates into an engine that's similar in efficiency at different loads. Hence, 1 of the reasons diesels get better mileage than gas engines.
2) Maintenance considerations. An engine turning 100 rpm doesn't require maintenance very often. At work, I have 7 recip engines that turn 300 rpm at full throttle. They've been in service since 1942 and will run for years without going through them.

I don't think anyone in their right mind will argue that 2v makes more power than 4v. I sincerely believe that, even if displacement were not limited, every form of racing that is allowed to use a 4v head will use it, assuming they are not penalized in other areas. This is somewhat beside my point though, because I say that displacement will be limited in the future to promote fuel savings, so in order to obtain more power from less displacement, 4v heads will be used more (and already have been).

I don't think this is correct. With most turbo's, we look at the Supra's to see what the limit of the turbo is, then try to get somewhere near that. With my turbo, the Supra's have made over 1000 rwhp, while no V-8 that I know of has broken that number. But there are other reasons for that. . .

Mike

racer7088

For unlimited high horsepower per inch or liter the 4V stuff is the only way to go so I absolutely agree that it's a great choice and enabler for high Hp/L at extreme rpm. You won't see any 2.5 L pushrod engines in F1!

For lower rpm it's not always the best choice though or at least not any big advantage over the pushrod stuff as far as power is concerned. This is why you see the bigger LSX stuff running the mileage numbers that these small high rpm mini-mee engines do while making more power and going much faster even in bigger heavier cars.

Now if we ever saw a japanese or German or American or ANY similarly sized DOHC 4V engine making spectacular and superior mileage to the pushrod stuff it might have some merit but we don't really see that right now.

All that extra DOHC valvetrain is just more drag when your cruising around at low rpm. It does allow nicer valvetrain timing but it won't make a lot more power or anything down there in rpm where the pushrod stuff can still keep up and do it with a lot less friction as well.

What we do see instead is smaller-engined lower-hp high rpm DOHC stuff making WORSE mileage even in smaller lighter cars yet still going slower most of the time. But they do have better Hp/L at least.

racer7088

I agree with you engineermike in that for ultimate power the 4V head has the potential for better breathing per square inch of bore area so it will allow more potential piston speed and more potential rpm on any engine. It also does this with smaller and thus lighter valves so it also alllows more rpm that way as well. The advantage of the lighter valves really takes off as rpm starts to increase.

Now you keep RPM way down with extremely large strokes and the advantage is much less, hence the LSx family beating the DOHC stuff in economy and power quite regularly in the rpm range that real cars that have to last for 200K miles run in since it has still great breathing and less frictional overhead due to it's much more simple pushrod design.

black_knight

iTrader: (1)

What if instead of limiting displacement, they limited size and weight? I wonder what the size and weight of the C5/6 R motor is versus the OHCammers it competes against. And LSX proves that the LS family can support even larger displacements. (although we're still waiting to see if they can do it with aluminum and keep the size/weight) It seems to win races now. I wonder if a size/weight limit would see the same split on displacement as the rules allow now, or if it would be more or less. Frankly, since size/weight is a real world limitation and displacement as such is not, I think racing would be vastly improved with that change. You would see race engines built around the limits of the world instead of on the limits of an artificial metric which has nothing to do with anything.

germeezy1

Yes I have I owned a Cutlass Calais with the HO 2.3 so I know how bad it was but it does not explain why the 3.4 would be stuck at 200-210 hp.

germeezy1

If you can package 427 cubic inches into a weight and size envelope smaller than most competitors 260-281 cubic inch DOHC engines and still have more low end power, more mid range and a 7,000 rpm redline. All backed by a 5 year/100k warranty why would you want technology for technologies sake?

engineermike

Racing engines are inherently limited in size and weight.

mzoomora

iTrader: (36)

Not true really. Most stock cars, professional drag racing, boat racing, sprint cars, etc are limited by displacement. Limited weight would just be a bonus.
Open wheel (F1, IRL, etc) is completely different.

engineermike

"Inherently limited" means that it's not "expressly limited", as in by a rule, but limited by other aspects of design.

mzoomora

iTrader: (36)

But the fact is they are only limited by the production engines they are based on, not inherently limited by the chassis, total vehicle weight, etc.
The SB2.2 is really just an evolution of the SBC, most drag racing classes run a HEMI design that has evolved over the years or various other designs that are not chassis limited but actually made larger and stronger, sprint cars run small blocks, etc.
The only thing limiting their size is the production engines they are based off of and not by any design aspect of the vehicle or class they run in- you could easily fit a big block Chevy in a Cup car. The engine has to be approved by NASCAR though.

Louie83

iTrader: (3)

Holy crap! I've been waiting 26 pages for you to admit that.

burtonbordr09

ok i know i am going to get some crap since i dont have very many posts and all of that but the question was what can be done to make an lsx make 100hp/l not would it make it better not would it pull a car through the traps at higher speed not the fact that it is something that needs to be done but just what could be done to allow for this measurement just imagine that this is the only reason to build the engine not even to put it in a car just to make it create 100hp/ltr even if only for a nano second that was the question and that is what should have been discussed there is like 50 discussions within this thread mostly for the sake of arguing which is rediculous i know that this is a forum i which things are to be discussed but out of the 506posts for this thread there is about 1 % that pertained to the whole concept well there is my thoughts on this thread hahahaha

black_knight

iTrader: (1)

The whole point of all the "ot" posts is that it is a stupid question and we shouldn't be discussing it.

ZoDDy

hmm, Hi there maybe a bit out of topic but i thought that the turbo engines use low compression that ads LESS stress to the engine? How long time under it's lifetime is the turbo really active and add high cylinder pressure?

I thought that the naturally aspirated V8's need to increase the rev range and drop some of it's good low end manner to gain serious power?

I also thought that the turbo engine can increase it's power output without increasing the engine speed and still sound like an original setup?

Don't turbo engines using mild cams that giving you very GOOD mileage? Lot's of lobe separation and that create Lot's of low end torq, vacuum for it's engine size and also manners?

How much stress and friction will the high CR and heavy V8 add from that time you twist the starter key? hmm let me see here... 8 pistons, 24 piston rings, 8 rods, 16 valves, 16 valve guides, huge oil pump, 16 lifters, 16 push rods, 16 valve springs, friction friction friction.. Something fishy is going on here

I also thought that the turbo creating Lot's of turbulence on the inlet side that helping the air fuel to mix and burn faster more effective?

I LOVE V8's but i also believe that the V8 had Lot's of friction and inner mass that robbing power and limit the rev range comparing to a smaller engine?

I had no clue that a huge V8 engine could give me better gas mileage than a smaller engine? I thought that the A/F Ratio was normally around 14.7:1 and also the common goal for most engine manufacturer?

Is it possible to run that huge high CR. 500hp V8 engine successfully with a very lean fuel mixture? I thought that 5.7L needs more fuel and air than a smaller 2.4L?

low engine speeds saves fuel and engines, but i thought that you need to feed 5.7L of air with the correct amount of fuel to avoid running lean?
Do the 5.7L engine really need LESS air than the 2,4L engine in a normal sized car? under normal way of use?

It must be like carry food for a year when you going to be away for a day? Carry an 80kees bag all the time when you don't need it? A turbo works WHEN you need it not all the time. Is a turbo really that stressful?

How long time and how much do you have use of low end torq and crazy power when you drive on the highway? Do you really need super torq at really low speeds? Why do we have a gearbox? And how slow do you need 2 go?

In this case i would prefere to have a small 2.4L liter engine with a turbo. Normal power for the street, Turbo power when i need it..
less friction, Less weight, , less average stress, better mileage less moving parts! And manners like a priest !!

Plz correct me if i'm totally wrong here..

But of other reasons I love V8 engines and it's the engine of my choice anyway.. Here in Europe we have always scratched out heads over the American engineering.. huge engines more suitable for a truck than a car hahah AND WE LOVE IT!!!

High power Rotarys are very interesting too.. call it ricer engines and crap, but i won't agree, they are fkn insane!

1BadAction

iTrader: (10)

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Stang's Bane

iTrader: (22)

I agree, please!!!