2000ultraZ1911

Lol ill drink to that!

ddnspider

iTrader: (26)

That sums up my argument. Since you feel the need to call others out on not reading your posts properly, If you bothered to read my post I specifically stated a purely streetcar on pump gas. Please explain why Chevy didnt put a high compression engine with less boost?.....better drivability, better emissions due to the cam they chose, and more margin to account for all operating conditions, not to mention room to grow.

Sales@Tick

iTrader: (3)

So some idiot doesn't go and put a rod through the side of block hoping to claim a warranty after being an idiot? Because they only needed a certain amount of power? Because they felt it wasn't necessary? I'm not a GM engineer I really can't answer that question truthfully

How does a car drive better with less compression? More cylinder pressure will combat the negative affect that holding the exhaust valve open longer has on cranking compression. Less cranking compression the less cylinder pressure you have the less efficient the engine is.

Every time we add compression to a car that has any type of positive valve overlap or even negative overlap it gains drivability and pulls more vacuum at idle.

I don't believe I called anyone out? Why are you so defensive? I just responded to your post...?

Your entitled to your opinion that less compression and more boost allows for more safety. I respect that.

Everything else I stated about cylinder pressure and filling the cylinder with air mass(pressure) is true though and is physics/science.

cmac06

iTrader: (16)

I think this is the most important point made. Boost doesn't make power, only air consumed by the engine. This was the hardest point for me to totally grasp when I started building my motor. Boost is only so widely acknowledged because it is often used to counter other inefficiencies in the design of the induction system. Of course there will be some back pressure in the induction system, but ideally the goal would be to minimize this as much as possible.

There are other benefits to running the higher compression, like better quench and mixing of A/F due to the better quench. I understand margin, but I don't believe lower compression necessarily increases margin.

The only reason to really reduce compression is if you don't size your compressor properly and run them out of their efficient area and not paying close enough attention to keeping the intake air cool enough. The whole point is to keep the burn controlled. The higher compression will really help off idle and at lower engine speeds where the lower compression motor is going to suffer. 9:1 is not really that low considering that a lot of decent performance cars use this CR. You're not going to see a lot of 7:1 CR built for street use.

ddnspider

iTrader: (26)

Im a bit disappointed by your ZR1 comment. I honestly thought it would be interesting to breakdown a high performance boosted production car into advantages and disadvantage since we're talking about boost and CR advantages/disadvantages in this thread.

As for my drivability comment, The lower CR usually drives better because of the cam associated with the setup.....lower overlap/duration compared to some of the higher overlap cams you referenced in your earlier post about bleeding off pressure on the higher CR setup.

And I'm hardly getting defensive.... Just following your lead in threads where people disagree with you

smokeshow

iTrader: (17)

You can argue with me all you want, but you can't argue with the math.

I will break it down in a simple manner holding lots of variables constant to illustrate my point. I pose two different scenarios, one with lower compression, and one with higher compression.

Assume the following as constant, arbitrary values: fuel octane, cylinder volume, ignition timing, compressor isentropic efficiency, cylinder pressure detonation threshold

Suppose that the cylinder air mass for a manifold air pressure of 200kpa is 2.0 grams at 100% volumetric efficiency. Now, take two different static compression ratios, for example 11:1 and 9:1. Suppose that the cylinder pressure detonation threshold is exactly the pressure at which the higher compression cylinder reaches when it compresses the air. This value in this example is 2200kpa, or 11scr x 200kpa. The value for the lower compression cylinder is 1800kpa. Since the detonation threshold isn't reached by the lower compression cylinder, you may increase the manifold air pressure accordingly. So, take that threshold pressure level and divide it by the lower compression number. 2200kpa / 9scr = 244.44kpa. This means you can run more boost. With the same cylinder volume, you can calculate the additional air mass contribution due to the additional boost using the ratio of the different pressure values: 244.44kpa / 200kpa = 1.2222. Now, multiply that by the initial cylinder air mass value, and you get your increased cylinder air mass: 2.0g x 1.2222 = 2.44 grams. With the increase in air mass, you increase the mass flow rate (horsepower) at a given RPM.

As for the change in piston dish or head chamber, consider a flat top 5.3 engine at 9.9:1 SCR. With 243 heads, the volume of the sum of the cylinder (assuming 0 deck clearance) and the chamber (including head gasket) is 741cc. By using a bigger chambered head or a dished piston, you introduce additional cylinder volume. A piston in that 5.3 with an 8cc dish (which lowers compression to 9:1)effectively adds volume, in this case going up to 749cc. Not a lot, but not necessarily negligible either.

An increase in compression can optimize the efficiency at which the air in the cylinder is used to make horsepower. However when using this argument with a boosted engine, the optimization from a compression increase is outweighed by the added air from increasing boost. Similar effects are found when trying to increase an engine's output by increasing ignition timing vs increasing boost.

toslow5o

iTrader: (4)

Could it be that race gas is over $10/gal and not readily available in every town?

Or that lower compression/higher boost doesn't always mean you're any more on edge?

... My guess is a combination of the two.

smokeshow

iTrader: (17)

Seriously. Mass flow rate is a rate, not pressure. For example, pounds per minute, grams per second, etc... Pressure is pounds per square inch, pascals, etc. They are different. Good things come to those who know and understand the differences.

Mass flow rate IS how much a compressor flows. What else could you be referring to? A turbo flows mass. It can't flow volume.

No, it isn't. Torque is force x radius. Horsepower is joules/second. Similar to watts. Again, horsepower is a rate...not of air, but energy.

Again, mass is NOT pressure. You are confused here. So everything else you stated is not true, it is nullified.

No its not. Please actually understand the physics before you claim radical things and call them science. I am embarrassed on your behalf after having read some of the things that you say on this site. And don't be so arrogant when people question your statements. It really makes you look like an *** and reflects poorly on your company.

Forcefed86

iTrader: (4)

I disagree.

Assuming you had a fuel with enough octane to fight auto ignition at higher compression ratios you would be correct. There is a reason you don't see many (if any?) performance NA guys pushing 17:1+ compression ratios. Once you reach a certain point the air can't be compressed anymore without getting so hot it auto ignites. (think diesel)

That is why you will make more power with lower compression and more boost. As I described in post #6.

So if we use the same numbers in post #6 and say 28:1 is our max effective compression for the fuel we are using, both motors would have the same charge density's. The larger of the 2 combustion chambers will make more power. It's as simple as that! Higher compression = smaller combustion chamber. The smaller the chamber (IF you are max charge density for your fuel) the less power it will make.

I think in Martins real world experience they are making more power when they use higher compression because they have not yet maxed out the fuel they are using. (haven't hit that hypothetical 28:1 yet) Once the detonation threshold of the fuel he is using is maxed out, upping compression(or adding more boost) would not net any gains and would auto-ignite. No reason at all to drop compression if they are meeting their power goals on 10:1+ and not having detonation/auto-ignition issues with the fuel used.

Boost doesn't change max flow it only changes charge density.

And for what it's worth I respect Martin and everything he's done for this community very much! No disrespect or "bashing" intended. Just friendly discussion going on here.

Sales@Tick

iTrader: (3)

I have not said one word out of line to anyone in this thread.

No need to argue.

ddnspider

iTrader: (26)

I completely agree with you. I posted that to find common ground with martin to continue the discussion. I should have clarified that a reasonable hp level can be achieved in multiple ways with multiple CR's and multiple boost levels.

toslow5o

iTrader: (4)

I don't disagree with any of your points or deny your vast technical theory/knowledge. To me, however, you look like an arrogant ***.

I do think you take statements too literal. Obviously torque is not literally equivalent to horsepower and they are not directly related. They both are a component to the desired end result.

Regardless how much you understand the physics and theories of an air pump I guarantee Martin has more real world experience. Of the two of you, who is more trusted by people seeking advice on how to spend their hard earned $$?

Not trying to **** you off but maybe self-awareness is the next subject you should focus on. For some soft skills are much more difficult to master....

Sales@Tick

iTrader: (3)

Why are you making personal attacks at me? I have not said one negative thing about you, yet I make myself and my company look bad?

Horsepower=torque produced x a given rpm/5250. 400rwtq@5000rpm=380rwtq. You can try and make me look bad I guess by using Newtonian physics and big words, but in the sense we're discussing torque=horsepower and horsepower is a mathematical figure.

I understand that our engine's computer's register air flow in g/minute and calculate fueling based off that. I understand that. I understand that this is how air flow is measured.

I believe all I said was Mass flow rate is how much a compressor flows. The same thing you said while trying to make me look bad again I guess? The amount of atmosphere a compressor produces though, when we're speaking about what an engine can consume to produce torque by filling the cylinder we're speaking in terms of volume. Measured by g/minute as you pointed out. When that volume fills the cylinder after it's been compressed by the compressor to well above atmospheric pressure it carries much more volume and mass than could theoretically fit into the cylinder it's trying to fill. The engine wouldn't fire if it were an actual liquid from the amount of mass in the cylinder. It would have too much cylinder pressure and much in the same way how a top fuel engine does when the plug doesn't fire on the compression stroke and hydro locks due to the amount of uncompressible liquid in the cylinder. Air is compressible though.

Because of this, we can fill that cylinder with incredible amounts of volumetric efficiency(there's a word I was saving). One of your other arguments was that a dished piston and larger chamber adds volume. Correct, your 100% correct it does. Guess what though, it lowers efficiency.

Case in point, you have a 500 c.i. pro stock motor that makes 1600hp. You have a 800 c.i. mountain motor that makes 1600hp. Guess which one has more volumetric efficiency even though they make identical power? The smaller engine.

Volumetric efficiency is just as the word would describe when used in the term of describing power output of a combustion engine. It's basically how efficient a given volume is filled. In this case we're filling 8 individual cylinders with air mass. The more efficient it is in filling that given volume the more power produced.

What I am saying is you don't have to increase volume to make more power. If you increase efficiency you increase power output. Compression is efficiency.

Also your first post your calculations used static compression. You don't even need me to point out how flawed that is because you didn't take into account the most important thing of all which is cam timing.

Why do you think all the heads up racers are running 11:1-12:1 compression boosted engines these days? Is it because they know more power can be had with dished pistons, 8:1 compression and just "turn the boost up"?

What happens when you run out of compressor? I'm sure you'll say, just use a bigger compressor. It doesn't always work that way though.

I don't have anymore time or energy to really keep up this argument. I guess you can say these are my opinions on the matter. It's worked for all of my customers which is what I'm after in the end.

You can make fun of my posts not being "scientific" or "Newtonian". It doesn't bother me.

smokeshow

iTrader: (17)

That is why I do not run a business, nor do I have any wish to do so. I can't stand the bullshit from the customers or the competition. But I do enjoy helping people understand things and am more than willing to do so.

smokeshow

iTrader: (17)

I am not even going to respond, Martin. You are too confrontational and you can't stand being even the slightest bit wrong. I have had countless similar arguments with people like you and my efforts are always in vain. You stick to the business, I will just stick to the science.

ayousef

Sorry I had to lol, Horsepower is joules/second? Horsepower in itself is a unit, trying to define it by another unit is like saying that knots is mph.

Sales@Tick

iTrader: (3)

One other thing I'd like to say, is the words high boost and low boost are oxymoron's.

What one engine moves for air mass that registers 15psi of pressure above atmospheric and what another engine moves for air mass that registers 30psi of pressure above atmospheric are actually identical amounts of air mass, but one engine is much larger in comparison OR smaller and more volumetric efficient over the other due to compression and induction. Thus they register different pressures in the intake.

They both need the same fuel requirements and they both have the same end cylinder pressure. This is due to mass of the air being consumed and compressed in the cylinder.

I have a pretty good pulse on what the fastest guys at the track in the heads up radial classes are utilizing to go faster than the other guy. Not one of them, at least that I know are using low compression like is being mentioned in this thread and more boost. They are all high compression motors.

Sales@Tick

iTrader: (3)

I have not said one word out line to you, cursed you or made any negative comments about you or your business that you pride yourself in working at.

I'm sorry you feel the way that you do.

mrstepheneades

Lol....

Forcefed86

iTrader: (4)

First I'd like to say... I respect Martin and everything he's done for this community very much! If I wanted a cam he's the guy I'd ask. No disrespect or "bashing" intended. Just friendly discussion going on here.

Boost is more efficient than compression at making power, period.

The reason the "racers" are using higher compression is because all the classes are turbo size limited. If the goal was peak power output and racers were all limited to the same cubic inches, you would see low compression, huge turbo setups dominating. Of course your customers aren't concerned with that, they want fast quarter mile times in class limited setups. Obviously you know your stuff and are providing them with great results the most efficient way possible for their specific goals.

I believe the most power per cubic inch ever recorded on a gas engine (nitro excluded) was produced by the 7:1 compression 1.5liter F1 turbo cars. Some drivers claimed over 80psi of manifold pressure during qualifying. They made close to 16hp per cubic inch, thats efficiency! That would be the equivalent of a 5600hp LS1. They could not have accomplished this with 12:1 static compression!