no, you noticed the difference between one clapped out piece of carp and another that [maybe] wasn't quite as bad.
uh huh. and cam timing doesn't make the slightest bit of difference to exhaust note - valves being open for different durations just doesn't come into it.
again, you're completely clueless - big pipe != better flow if it causes turbulence. real dyno'd racing pipes are all about flow dynamics, not size.
Greetings Nate, That reply you got from jim beam was only aimed at insulting you and is typical of the replies coming from all those cowards who get off from acting like experts and trying to insult people. I can't figure out if it's mostly a bunch of teenage boys or cowardly old guys who can't defend themselves, verbally or physically, in face to face contacts with normal people. Either way, the posts come from cowards. It reminds me of the CB craze in the 70s. All these guys would get on the radio and pretend to be something they weren't. Well, Usenet is where a lot of those guys ended up on. They can pretend to be anybody they want. Walter Mittty types. And who wants to pretend they are just regular folks? So these cowards get on Usenet and pretend to be tough guys and experts. They make up names for themselves instead of using their real names when they post messages. Then they feel free to insult whomever they want and go to bed at night pretending to be real men instead of facing up to reality, that they're cowards, and they are too cowardly to even try to change. It's best to just ignore them. That's what kill filters are for. Eric
Greetings Nate, That reply you got from jim beam was only aimed at insulting you and is typical of the replies coming from all those cowards who get off from acting like experts and trying to insult people. I can't figure out if it's mostly a bunch of teenage boys or cowardly old guys who can't defend themselves, verbally or physically, in face to face contacts with normal people. Either way, the posts come from cowards. It reminds me of the CB craze in the 70s. All these guys would get on the radio and pretend to be something they weren't. Well, Usenet is where a lot of those guys ended up on. They can pretend to be anybody they want. Walter Mittty types. And who wants to pretend they are just regular folks? So these cowards get on Usenet and pretend to be tough guys and experts. They make up names for themselves instead of using their real names when they post messages. Then they feel free to insult whomever they want and go to bed at night pretending to be real men instead of facing up to reality, that they're cowards, and they are too cowardly to even try to change. It's best to just ignore them. That's what kill filters are for. Eric
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And Nate is quite right. As one who raced sports cars in the early '70s, I can back him up that a high-compression engine sounds a lot crisper and sharper. When I replaced the stock engine in my Alfa with a Tom O'Brien high-compression racing engine, the difference in the exhaust note was very distinct. And that was with the same carbs and exhaust system.
Yes, clearly, a brand new engine with all NOS, never-used parts, isn't "quite as bad as a piece of crap."
I glossed over a bit, but I have actually heard quite a few standard Stude 289s with R1/R2 cams installed in them - it's a fairly common thing for enthusiasts to do. There's still a difference in sound between a cammed standard 289 and a R1.
Not entirely wrong, but in any case, that was a peripheral comment to the original point.
nate
dude, if you leave the exact same engine in place and simply replace the cam, you'll hear the same difference. that's all that's happening here
- valve duration is making it sound different, not compression.
you're an illiterate retard - re-read what i said.
duh, no shit.
uh huh.
wow, disingenuousness at it's finest.
no, it's central to the point that you don't understand what you're talking about - you're misattributing one cause to another effect.
dude, if you leave the exact same engine in place and simply replace the cam, you'll hear the same difference. that's all that's happening here
- valve duration is making it sound different, not compression.
ok, stop right there. compression, as in compression ratio, is swept volume divided by static volume. the cam makes no difference to that.
if you mean volumetric efficiency, that does indeed change with the cam, but that's not the same thing, and it's certainly not what was being described earlier.
as a function of the breathing, or volumetric efficiency, and valve open duration, not the compression. you're listening to burning gas that's being allowed to escape after doing work.
10,000 people all misunderstanding the same thing together doesn't make a single one of them correct.
Fuel price is based on therm content - diesel has a higher energy density - and supply and demand. Diesel fuel, furnace oil, and Jet fuel are all closely related - and if the demands for those fuels are high the price goes higher than gasoline. With catalytic cracking they can make gasoline out of what would normally be diesel - but it's more difficult to make diesel out of gasoline.
On some cars it definitely is. On my 63 Valiant 170 if I tuned it for hightest I got a lot better mileage (and power) than if I tuned it for regular. The heads were shaved 25 thou if I remember correctly - it put 206 HP to the rear wheels through the pushbutton automatic at 6500 RPM (160 ft lbs torque) on premium. I had to adjust the timing for the fuel.
There are a lot of engines today that recommend premium - and some that will take advantage of roughly 115AKI fuels like E85, (there is no such thing as 101 octane fuel - 100 and over is technically AKI (Anti Knock Index)
Yes - particularly on a high compression engine with a sweet cam. The compression alone makes for a crisper exhaust note if you have an open enough exhaust. - but through the average muffler you don't notice it much without the better cam
MOST higher compression engines have different cams - with the right cam you can run over 15:1 on regular pump gas because the effective CR is much lower at low speeds - making the engine less likely to detonate under load. The CR and VE goes up when the engine comes "on cam" - where it sounds sweet.
The R1 had a gnarly cam as well as the higher compression.
But a different cam. The hot cam with lower compression sounds a lot tamer than the high compression engine with the hot cam - the high compression engine with the standard cam sounds only moderately sharper than the low compression engine with the standard cam. - but the difference is definitely there.
Just putting on a set of High Compression heads on a Ford Flatty - 4 or 8 cyl, definitely made a difference to the exhaust note - without any other changes.
Oh yes it does!! Not the "theoretical" compression ratio, but the "effective" compression ratio. The important thing is how hard is the f/a ratio squeezed before the spark lights it off.
With a hot cam in a 15:1 CR engine, at low RPM the squeeze will only be in the neighbourhood of 10 times atmospheric. - 10:1 ratio. At peak torque rpm, it will be 15 times - and with a properly designed intake and exhaust, in a narrow RPM range, possibly as high as 16.5: times.
Definitely correct - the trained ear will be able to tell the difference.
To a point - but not exclusively. High compression changes the pressure of the pulse, just like valve timing does - and even fuel mixture. The sweet spot is neither too rich or too lean.
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(JB)
ok, stop right there. compression, as in compression ratio, is swept volume divided by static volume. the cam makes no difference to that.
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(EH)
Ok, now YOU stop right there. You're talking about nominal, or static, compression ratio. That's why I said ACTUAL compression ratio, which varies with engine speed, valve lift and timing, and intake or exhaust tuning.
Nominal is usually higher than actual. Actual compression in a racing engine runs close to nominal, and can actually run HIGHER than nominal. The BRM H-16 F1 engine of the early '60s supposedly ran at 1.4 times nominal, at peak horsepower rpm. I would be surprised if today's F1 engines aren't running higher than that, but I haven't kept up. Racing motorcycles run even higher.
I was trying to give you the benefit of the doubt, pointing out that the sharper, louder exhaust note CAN result from different cam timing, but that's because it's getting more fuel-air into the engine, increasing its effective, actual compression ratio.
If you have an engine that has a nominal compression ratio of 10:1, and it has well-tuned intake and exhaust and optimum lift and overlap, the actual compression can be, for example, 12:1 at a particular rpm with full throttle. You're getting 1.2 times more fuel-air into the cylinders than you would if it were running at the nominal compression ratio at atmospheric pressure. It's a slight supercharging effect, without a supercharger.
The sound you get from an engine's exhaust, ignoring any muffling going on, depends on the quantity of gas leaving the cylinder and the abruptness of the impulse, both of which are higher with a higher compression ratio. That's true whether the higher compression is the result of the mechanical ratio of swept volume to combustion chamber volume (nominal compression) or the result of getting a higher-than-atmospheric charge into the cylinder, with supercharging or pipe tuning, combined with cam design.
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(JB)
if you mean volumetric efficiency, that does indeed change with the cam, but that's not the same thing, and it's certainly not what was being described earlier.
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(EH)
Same result. It's the amount of escaping gas and the abruptness of the impulse that determines the note at the exhaust manifold. Unless you have something in the exhaust system to change that, that's the note you'll get.
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======================================================== (JB)
as a function of the breathing, or volumetric efficiency, and valve open duration, not the compression. you're listening to burning gas that's being allowed to escape after doing work.
======================================================== (EH)
It's true that you're listening to escaping gas, but the impulse is much greater with a high-compression engine. The peak pressure at the time of the exhaust valve opening is much higher, and thus the sound is sharper. In qualitative terms, it sounds a lot "crisper."
======================================================== (JB)
10,000 people all misunderstanding the same thing together doesn't make a single one of them correct.======================================================== (EH)
I'm losing track of your claims, and it's possible that we're just talking past each other with different terminology. But, to boil down what I'm saying, raising compression ratio raises the pressure in the cylinder, at TDC, certainly, but also at the time of exhaust-valve opening. At BDC, theoretically, it should be the same with high or low compression. But the exhaust valve does not open at BDC. It opens while the pressure is still high, and it's higher with a high-compression engine.
It's too bad I can't take us back to the late '60s or early '70s and compare the sound of a British Ford 116E engine in a Formula Ford (110 hp and low compression) with that of the same basic engine in a Lotus 23 (~ 180 hp with fiercely high compression, in most cases). You wouldn't mistake the difference.
Just putting on a set of High Compression heads on a Ford Flatty - 4 or 8 cyl, definitely made a difference to the exhaust note - without any other changes.
============================================================== (EH)
See, I was going to mention Ford flatheads, but that would open me up to charges of antiquity and senility. I have enough trouble with that already. d8-)
And since you brought it up, how about the sound of a flathead V8 with Offy heads, an Isky 404 camshaft, and open Lakes pipes? Mama mia, that was worth losing your hearing just to be there.
Or how about a 1275cc stage 3 cooper with a 2 inch straight exhaust??? IIRC it was over 13.5:1 compression - we could not get good enough gas to run it in Zambia unless we went to the airport and bought the "good stuff" The normal (at the time) 91/96 was not adequate - the 115/145 was good, but not always available. Not sure if 100LL would do the job or not today.
Or how about a 1275cc stage 3 cooper with a 2 inch straight exhaust???
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(EH)
I had one of those engines! MG, though, not Cooper, so I didn't have the steel crank. But I did have the 1-1/4" SUs, a Racer Brown 3/4 cam, shaved head, and a megaphone exhaust. That was my last race car.
I did love the sound. d8-)
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IIRC it was over 13.5:1 compression - we could not get good enough gas to run it in Zambia unless we went to the airport and bought the "good stuff" The normal (at the time) 91/96 was not adequate - the 115/145 was good, but not always available. Not sure if 100LL would do the job or not today.
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Oh, man, so you were an international rally guy, eh? That must have been exciting. I just raced in SCCA club events, and a couple of hillclimbs. Then I became diabetic and they lifted my license. d8-( Then my pilot's license was lifted a few months later. d8-((
Depends on your perspective. I consider the R1 cam to be pretty mild, something like what we'd call an "RV" grind today.
nate
Now we're getting way OT of the original post... but I agree with you, and I suspect the reason is actually the same as the reason a Studebaker (bringing us back a few posts) or Caddy V-8 sounds so good too... I think it's that siamesed center exhaust port. It just does something to the exhaust sound that makes it sound so much nastier than more modern head designs as found on a SBC, SBF, or LA engine...
Now I really am just speculating, I don't know why it is, but tell me that I'm wrong - all three of the old-school engines I mentioned sound fantastic when tuned up and wound out.
nate
Imagine that cooper with twin DCOE45 Webers in, of all things, A MOKE!!!!!
But definitely wilder than the stock 289. The stock 289 had 8.5:1 on the Lark, Comander and Daytona - In'65 and '66 the Avanti and hawk (r1) got 10.25:1 except for the supercharged engine, at 9.0:1
The base 289 8.5:1 was 210hp at 4600 rpm The R1 NA engine was 240hp - RPM not specified
The Avanti (r1)cam was closer to what we referred to back in the day as a "semi-grind". Good for about 15% power increase over the "stock" cam on a NA engine - just a bit of lump at idle, and a good fat torque curve 260/210 duration with 110 lobe separation and about 460 lift - max HP Rpm up closer to 4000 Rpm somewhere. - a 2800rpm cruise cam
Pretty close to a Crane Max Velocity 260-2-NC for a Ford 289 or a crane hmv-260-2-nc
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