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Thread: 4.3 dyno 300hp

  1. #16
    Slow Ride
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    you just need to worry about cylinder pressure. If the cam has lot's of overlap then you can spray at lower engine speeds. ti you might need to upgrade teh heads a bit more and add more cam to get that much juice into the engine. The bottom end might be able to handle it but teh induction system might not be able to get it all in the cylinders even with a good fogger system.

    http://www.carcraft.com/techarticles...uke/index.html
    Last edited by Slow Ride; 01-02-2005 at 11:47 PM.

  2. #17
    Registered User Catching Second's Avatar
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    Originally posted by ti28
    the engines running about 120%volumetric efficiency and with my overlap and with that efficiency its inertia superchargered..i hope you know what that is or do i have to elaborate???not to come off like a dick...i just whanna point out that i do know what i am doing..i just dont whanna sound a biligerent asshole or arrogant for that fact
    So in other words the air/fuel mixture is more than thoroughly burnt (no gasses/air going unspent).

    volumetric efficiency: the percentage of fuel/air burnt inside the combustion chamber when the spark plug ignites the chemical reaction. the higher the percentage, the less air/fuel there is NOT being burnt or used.

    Good? :smoker:
    "A true hotrodder wouldn't be content untill he had created a car so violent, so hairy, so totally sick that the very act of dropping the hammer would result in instant death. Anything less results in the need to go faster." - Tony DeFeo

  3. #18
    holeshot
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    Originally posted by 964pt3
    What gets me here is the carb deal. 800 CFM rejetted and tweaked???? Cant make a carb flow more CFM unless you change the main body out, then it would be dam near impossible to correctly meter and jet a Rochester for a motor that only needs 350 CFM max to run!! Dyno chart would also show the spikes of having too large a carb which it doesnt!!

    What heads are you running?????
    What compression ratio????

    265 is obtainable, but not with what I currently see!!
    i agree with this guy about the 800 you cant change the CFM without chaging the body rejetted doesnt do anything but change the air/fuel (if you shit a 1/2 lb turd when your tired when you wake up in the morning your not gonna be able to shit a leprechaun cause your ass is still the same size) Perfect example i think sounds stupid though oh well, however 800 cfm is way to damn much that would kill a 350 hp 350 but the 350 cfm he claimed is wrong seeing as my 2.8 has a 400 cfm throttle body i think 525-600 cfm "jetted and tweaked" as you say for use with nitro.

  4. #19
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    Originally posted by Catching Second
    So in other words the air/fuel mixture is more than thoroughly burnt (no gasses/air going unspent).

    volumetric efficiency: the percentage of fuel/air burnt inside the combustion chamber when the spark plug ignites the chemical reaction. the higher the percentage, the less air/fuel there is NOT being burnt or used.

    Good? :smoker:

    Okay, so how the hell are you at 120% efficiency then, TI28??? Shouldn't that be theoretically impossible?
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    In 1095, Pope Urban II commanded the beginning of the most heinous period ever documented: The Crusades. While killing over 100,000 Turks in 1098, the Christians "did no other harm to the women found in [the enemy's] tents - save that they ran their lances through their bellies," according to Christian chronicler Fulcher of Chartres.

  5. #20
    Registered User Catching Second's Avatar
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    http://www.installuniversity.com/ins...n_9.012000.htm


    "Volumetric efficiency is the measurement of how close the actual volumetric flow rate is to the theoretical volumetric flow rate. A engine has a set volume (displacement) that can be calculated. However, your engine will not use the full volume (100%) it has available because of friction losses, leaks, and the fact that a mass produced engine can only be so good before the money out weighs the benefits (the point of diminishing returns)."


    So how exactly are you getting 125% vol. eff.?
    "A true hotrodder wouldn't be content untill he had created a car so violent, so hairy, so totally sick that the very act of dropping the hammer would result in instant death. Anything less results in the need to go faster." - Tony DeFeo

  6. #21
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    Also, in order to destroy your theory of 120% volumetric efficiency, lets take a look at the 2nd law of thermodynamics.

    The 2nd law states that " - No continually working engine can take fuel from a source and convert it completely to work."
    Therefore, it is impossible to be 100% effiecient in anything where a fuel is being burned and converted from one type of energy to another. This not only violates the 2nd law of thermodynamics, but also Carnot's law regarding heat engines.

    Basically due to mechanical friction and other irreversiblities no cycle can achieve this efficiency of 100%. The gross work output of cycle, i.e. the work done by the system is: Wg = W41 + W12

    and work ratio is defined as the ratio of the net work, W, to the gross work output, Wg, i.e.

    W / Wg

    The Carnot cycle has a low work ratio. Although this cycle is the most efficient system for power generation theoretically, it can not be used in practice.



    So, TI, unless you figured out a way to make a Carnot Cycle engine work, which is theoretically impossible, then you do not have 120% volumetric efficiency with an N/A motor.

    So do you want to start over and try to explain again what you mean about you engine, maybe we misunderstood you? I really want to understand, I just dont quite get what your saying and how it relates to the numbers that you are talking about.
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    In 1095, Pope Urban II commanded the beginning of the most heinous period ever documented: The Crusades. While killing over 100,000 Turks in 1098, the Christians "did no other harm to the women found in [the enemy's] tents - save that they ran their lances through their bellies," according to Christian chronicler Fulcher of Chartres.

  7. #22
    Slow Ride
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    the efficiency of thengine is actually very low.

    Volumetric efficiency is different. Say you have a 350 and its VE is 90% then only 315 cubic inches of air/fuel will enter the engine in a complete cycle. Supercharging forces more air into teh engine than would be possible by NA thus the VE will be above 100%. Inertial supercharging is a hard thing to get ahold of. The intake tract has to be tuned like a correctly built header. The problem is that the intake is only inertial supercharging at specific RPMs and actually pulling air/fuel out at others.

    I will explain further if anyone is interested.

  8. #23
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    Ok, it makes sense then that the Volumetric Efficiency would be able to be above 100% with a supercharger or turbocharger, but it is not possible to make ita bout 100% naturally aspirated, correct?
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    In 1095, Pope Urban II commanded the beginning of the most heinous period ever documented: The Crusades. While killing over 100,000 Turks in 1098, the Christians "did no other harm to the women found in [the enemy's] tents - save that they ran their lances through their bellies," according to Christian chronicler Fulcher of Chartres.

  9. #24
    Registered User BoostedTy's Avatar
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    It is possible but very difficult to excede 100% VE on a naturally aspirated engine. Most engines are 65-85%. It takes extremely tuned runners with killer head flow, and a matched exhaust to get there...Think Nascar. Rumor has it they are over 100%, but for a very short power band.

    Hot rod or car craft did an article on the gm QUAD 4 motors, and graphs showed spots of over 100 % but only by 2-3 percent, and for very short lengths of time.....Because the times that they are over 100% are when everything is perfect, engine RPM, intake plenum volume, intake runner length, etc. 125% is too high.

    Take another point.... Ford Taurus SHO. It has 2 sets of intake runners for a particular reason....the long runners aid in torque production, and Good VE at low end while the short runners are for WOT, and are better for higher RPM. They hoped that the 2 runners will have the car closer to 100% more of the time.

    It sounds like a sweet setup. Should be interesting to see what it lays down with intake, heads, and headers....
    Damn.

  10. #25
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    Originally posted by Catching Second
    I can respect you wanting to be different I guess. It's all in what you like.

    About the nitros thing, I am no expert on it. I'm just going by what I was told on here when I was thinking about running a 175 shot through my engine. I was told to spray at nothing lower than 3000rpm and nothing within 200-300rpm from my rev limiter.

    The 3000 rpm rule is from the old days of nitrous. What is meant by that is the timing. If you have too much timing off the line it will backfire through the intake. I am sure most of you have seen either a video or witnessed this firsthand at the strip. That is the reason for people to run window switches or delays on their nitruos systems, or not turning it on till second gear when your timing is all in and your motor is up to speed. If you have a good retard and timing controls you can pretty much spray off the line. It takes alot of tuning, and it will be a dog off the bottle to go this route.

    just my .02

    Back on topic now.
    dave -

  11. #26
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    Originally posted by holeshot
    i agree with this guy about the 800 you cant change the CFM without chaging the body rejetted doesnt do anything but change the air/fuel (if you shit a 1/2 lb turd when your tired when you wake up in the morning your not gonna be able to shit a leprechaun cause your ass is still the same size) Perfect example i think sounds stupid though oh well, however 800 cfm is way to damn much that would kill a 350 hp 350 but the 350 cfm he claimed is wrong seeing as my 2.8 has a 400 cfm throttle body i think 525-600 cfm "jetted and tweaked" as you say for use with nitro.
    No, I stated 350cfm is what the motor would use. You still want oversizing of a carb beyond that amount so you can get the correct pressure drop changes in effect. A 500 would be more than plenty jetted out correctly for the nitrous and a 600 down jetted would also be the ticket too. A 800 CFM carb would have such a pressure drop change at part throttle the dyno would have shown wild spikes. You want to maintain around 1-1.5 inch at WOT and racers like bigger carbs to maintain .5-.75 cause they dont care about part throttle reponse where higher faster drops in pressure create havoc cause there never in this RPM range.

    If you could obtain 85% VE on a NA motor you would be doing very well!!

  12. #27
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    Originally posted by ti28
    1st off dude what the hell are you talkin about?265????cant you fuckin read the dyno dont lie(not the last time i remember)..and one more thing were do get off telling me that MY motor only needs 350cfm to run max.hahahhahahaha are you fucking kidding me buddy...im running 11.5:1 and i using stock vortec heads...and one more fucking thing you can take a stock rodchester to flow 1200cfm..so i dont whanna here that shit buddy
    1200 CFM on a Rochester Carb??? And where would we find such a main body for such. People shy away from Rochester carbs for many a reason, from parts no longer being available to its one of the hardest for even a seasoned veteran to attack and rebuild properly. Oh you''ll find so old schoolers, me included that actually like to run those carbs, but the majority will run other aftermarket because of the simplicity and parts availiablity to change configuration.
    Not saying you did, but you can copy other peoples dyno sheets and 1..5:1 on the road with the current readily available gas and shooting nitrous. Boy I hope you stay on the track with it, cause it sure aint gonna last without some form of racing fuel!!!

  13. #28
    holeshot
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    Originally posted by 964pt3
    1200 CFM on a Rochester Carb??? And where would we find such a main body for such.
    Get me a roll of duct tape a frying pan my snorkel and an avacado.

  14. #29
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    Originally posted by holeshot
    Get me a roll of duct tape a frying pan my snorkel and an avacado.
    Trust me bro, I've made bongs with less.. :rofl:


    Ok, back on topic of the thread... Volumetric Efficiency and the size of Main Bodies on carbs.. And I'm still waiting for Ti28 to chime back in on hi idea that he has 120% VE
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    In 1095, Pope Urban II commanded the beginning of the most heinous period ever documented: The Crusades. While killing over 100,000 Turks in 1098, the Christians "did no other harm to the women found in [the enemy's] tents - save that they ran their lances through their bellies," according to Christian chronicler Fulcher of Chartres.

  15. #30
    gas assassin slackware's Avatar
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    who said you cant have more volumetric efficiency than 100?

    lets say theres an N/A motor, if it could draw in as much air as its displacement will allow and completely burns all of the fuel/air, we would call that 100% VE.
    Now, if your using a turbo/supercharger to indroduce say 20% more total volume than the original amount, it is described as 120% volumetric efficiency.

    not sure if someone replied to that, but its an accepted idea that makes sense
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