RE DUMP VALVE

[WRC No 1]

moved to keep people happy

[the squiggle]

I need to know, how you came to the conclusion that you only dump half the air or less than half the air and recirculate the rest. The pressurised volume of air contained between the throttle butterfly and the turbo outlet will be expelled to atmosphere, not half kept and recirculated.

At 1 bar of boost, 14psi, which is the equivelent of atmospheric pressure times 2. The dump valve will try to equalise the pressure in the intercooler and the pressure in the atmoshere, so in theory there is still atmospheric pressure present in the intercooler ready to go in the cylinders. Since the throttle butterfly is now closed and the car is idling through the Idle Control Valve the pressure in the intercooler/turbo area is now trying to pul vacuum conditions. On a std recirc this area would now be filled with the volume of air the the recirc has rerouted into the turbo outlet but on a VTA that volume air is expelled until both intercooler and atmosphere is equalised.

On throttle lift off condtions, on a std recirc the AFR would be 12 - 1 with the volume of air being accounted, if you expell this volume of air to the atmosphere then it will drop to 6-1 or even lower.

Grant

[the squiggle]

On another wee point, there is a wee section on SIDC and Scoobynet called General Technical. This would be a bit more appropriate place to post this thread where you would get a wider audience to respond. There has 1000+ posts on this subject by numerous respected people, Harvey, AndyF, Pavlo, David Wallis, etc, etc. Please feel free to browse these fine respected peoples posts and come to your own conclusions.

Grant

[dougster]

Trusting local knowledge is always helpful but I tend to agree with Grant.

I don't want to start shifting threads until the new software and guidelines are in place though.

On the dump valve note; get an aftermarket recirculating valve like my APS and get the best of both worlds.

All ears welcome to have a listen (if it ever moves again!!! )

[paddy247]

1 bar of boost is 14.7 psi, atmospheric pressure is also 14.7 psi. Wink wink nudge nudge.

[WRC No 1]

i dont have the recirc valve back on

[dougster]

I had a Bailey VTA on mine for a while with ITG panel filter and resonator removed.

Now Hyperflow (k&n cone) with APS recirc.

No problems with MAF or turbo to date.

[fraser_drinkwater]

Everyone buy Jap Performance this month it has a section dedicated to this,and the truth will be told.

[Carl Davey]

I need to know, how you came to the conclusion that 14psi is the equivelent of atmospheric pressure x2...

Atmospheric pressure = 1 bar

1 bar boost = 1barg (gauge) or 2bara (absolute)

I do agree with Grant that the technical knowledge in here is a little 'bloke down the pub' - as proven above. I'd recommend eductating yourself before making your own judgments based on facts divulged on the various websites, here, SNet, 22B etc.

My thoughts on dump valves are pretty well documented on here, i see you have a flamer kit fitted already though so will leave you to screw up your cars fuelling on your own.

[the squiggle]

Atmospheric pressure = 1 bar

1 bar boost = 1barg (gauge) or 2bara (absolute)

Thats what i meant but it did not come out right.

Grant

[fraser_drinkwater]

psmsl now thats entertainment lol

gotta love the humour.

You cant be serious about this now can ya!!!

[fraser_drinkwater]

Think this should do...

Engine Genetics

Engine performance for the genetically curious or engine genetics for the performance curious ...

Why is it that your cultivator engine plods along at a mind numbingly 3200 rev/min?

Why does your average gasoline passenger car engine run to 6000 rev/min?

Why are passenger car diesel engines restricted to 4500 rev/min?

What's Montoya?s BMW engine got that gives him 19000 rev/min?

Is there a link between all reciprocating engines and are they ?brothers under the skin??

The Eureka moment comes from an understanding of the relationship between mean piston speed and brake mean effective pressure (BMEP). If you don?t know what these terms are, open an engine textbook and find out. For the terminally lazy, consider that mean piston speed is the average speed of the piston as it travels from top dead centre to bottom dead centre. BMEP can be considered as specific power per unit swept volume per unit rotational speed.

Plotting BMEP against mean piston speed we can see:-

The Heavy Duty (HD) diesel engine is limited to a mean piston speed of about 11.5 m/s irrespective of bore and stroke. The data includes 400 kW on-highway truck engines and 4000 kW generating set prime movers. This is essentially a limitation on peak inlet port gas speed, characterised by mean piston speed. Air consumption is limited by the need to produce both an inlet swirl and flow, resulting in a mean inlet flow coefficient that is significantly worse than a gasoline engine. Since the diesel engine runs a significantly higher compression ratio, the peak cylinder pressures are higher than gasoline engines, the structures to support this loading are more robust. The diesel engine is, therefore limited to a lower mean piston speed than the gasoline counterpart by the ability to transfer air from the outside to the inside of the cylinder and by the higher friction losses associated with the higher mechanical loading.

The Light Duty (LD) passenger car engine runs to 13 -14 m/s mean piston speed as the lighter structures and reduced load factors contrive to lower the parasitic losses. Electronic fuel systems are limited to 4500 rev/min by the speed of the control solenoids and the pressures required to inject fuel into the cylinder in a short time period.

Development of the diesel engine proceeds parallel to the abscissa restrained by mechanical losses and to a lesser extent by air delivery issues. Ever higher boost ratios and mechanical loading limit the progress via material tribological and fuel system challenges.

A gasoline passenger car engine doesn?t need swirl to mix fuel and air and runs to 18 m/s mean piston speed and slightly more in motorcycle configuration. The Honda S-2000 runs to 9000 rev/min, a staggering 23 m/s and would be the engine engineer?s choice for ?engine of the decade?. Formula 1 engines run to 26 m/s aided by a design brief to achieve an advantage irrespective of cost and aided by uncompromisingly expensive and light components to limit inertia loading and a 25 hour life.

The Gasoline Direct Injection (GDI) engines run slightly higher mean piston speed than the port injected gasoline engine as the air consumption of the GDI is higher as the inlet system has only to pump air and not air + fuel.

Development of the gasoline engine proceeds at 60 degrees to the abscissa limited by parasitic losses, thermal loading and in the case of F1 engines, by valve gear durability.

It follows that:

All engines are brothers, related by mean piston speed and BMEP.

The Honda S-2000 is the engineer?s choice for engine of the decade but would your grandparents be happy with one?

The diesel engine is capable of running faster than 4500 rev/min when fuel systems are capable. An engine speed of 10,000 rev/min is technically feasible.

In the future, will turbocharging find favour on passenger car gasoline and will the gap between gasoline and diesel structures narrow?

Answers:

The limiting mean piston speed of industrial gasoline turf engines and passenger car engines are not dissimilar. The turf engine has a restrictive exhaust (higher parasitic loading) designed to minimise noise and keep the neighbours happy.

The average gasoline runs to 6000 rev/min or 18 m/s mean piston speed as this is a happy balance between cost, rated speed power and the ability to sit at 70 mph at 2500 rev/min in top and still accelerate (just) with peak torque only some 1000 rev/min higher.

The diesel engine is restricted to 4500 rev/min by the ability of the fuel system to deliver fuel at the correct quantity and at the correct rate to ensure complete combustion. Higher engine speeds are possible with continued fuel system development.

Montoya?s racecar engine runs to 26 m/s or 19000 rev/min as the only mechanical development restraint on this engine is the ability of the valve gear to stay in one piece.

?Is there a common link between all engines?? ?... mean piston speed and BMEP.

By Fraser MEng BSC

[WRC No 1]

hope that was not a yahoo copy and paste ???

lmao

[fraser_drinkwater]

nut am just after help on whether to get a diesel turbo or a optimax turbo when a trade gayles car in ?

And also which should last longer??

[2559B]

for people like myself who ain't technically minded.......here's what a dump valve is/does

When a turbo spins it compresses air into an engine. With fuel and spark this gives us the power we need to drive our car. When there is a change in desired boost pressure (ie the user lifts off the throttle or changes gear) there is still a large amount of air heading towards the engine. This air cannot get into the engine as the butterfly on the throttle has closed or has closed in comparison to previously. This air has to escape somewhere or it would cause the turbo to stall and potentially cause damage to the turbo or the housing to the inlet manifold. Fitting a ?dump valve? rectifies this. This unit basically ?dumps? excess air into either the atmosphere (atmospheric dump valve), or back into the engine (re-circulating). This ?whoosh? noise that you may here from other turbocharged cars is generally the result of an ?atmospheric? dump valve blowing off air to the atmosphere as the driver changes gear. The C20LET engines were fitted with a re-circulating Dump Valve as standard. Under high boost, problems with the standard (and atmospheric) dump-valve?s can occur, resulting in less boost pressure being held and therefore a drop in power. Fitting an up-rated dump-valve such as the Bailey DV26 double sprung dump valve or ?even better ? our recently developed electronic dump valve can rectify this problem. This completely eradicates any false openings on partial throttle giving the best all round solution for a performance car. The electronic dump valve is also an atmospheric dump valve producing a loud ?whoosh? when the next gear is selected under load.

[fraser_drinkwater]

As you see, Robert Boyle gave us a way to calculate the volume of a gas when the pressure on a closed, but flexible system is changed. His formula specifically states that the volume of a gas, under conditions of stable temperature and amount of gas, is inversely proportional to pressure. Thus, if the pressure is doubled, the volume of the gas will be cut in half, etc. The formula for this law is:

P1V1 = P2V2

whereas, P1 is the original or starting pressure, P2 is the final pressure, V1 is the starting volume and V2 is the final volume. We can use this formula to solve for either one of the four variables if the other three are known, for example:

V2 = P1V1 / P2

Take care in using Boyle's Law that you remember that the temperature or amount of gas (moles or mass) cannot change at the same time!

thats boyles law now charles this will help all peeps out ...

. Charles discovered a way for us to understand the relationship between the volume of a gas and its temp- erature. After a series of experiments, he concluded that the volume of a gas is DIRECTLY proportional to its absolute temperature. (V1 / T1 = V2 / T2) . This works ONLY if any temperature given is first converted to absolute (Kelvin) temperature and assuming that the amount (moles or mass) of gas and the pressure are held constant. It has also been noticed that the pressure changes if the volume is held constant and the temperature is changed. Click here < for a really neat site which will actually allow you to see what happens to the pressure in a closed container (volume held constant) when the temperature is changed. Note that the temperature must be in Kelvin when working Charles' Law problems!

The Combined Gas Law contains six variables, which includes all of the gas laws on this page except Dalton's Law. It combines the laws of Boyle, Charles and Gay-Lussac into one formula that can be used to solve for any one of the variables when the others are known. The formula is:

P1V1 / T1 = P2V2 / T2

by transposition like you all learned in high school you can now work out gas volumes against charge temp

[2559B]

hmm... think i know the answer, is it?

b= (6.44*10E-9 *c^3/2)/ B

where b, B is both known... and we need to find unknown value "c" hmm how should we go about doing it .. seems kind of simple but i actually have a hard time doing it....

b = (6.44*10E-9 * c^3/2)/B....(1)

a = (J *1.54*10E-6*B^2*exp(10.4/sqr©) / c...(2)

suppose a,b and j are known values... and we need to find c and B.... i have problem doing that.. initally i try to find one unknow first .. ie) making B the value we want to find first in terms of c.... so we have

B = (6.44*10E-9 * c^3/2)/b ... (3)

then we sub formula (3) into (2) so we have

a= (J *1.54*10E-6*(((6.44*10E-9 * c^3/2)/B)^2)exp(10.4/sqr©)/c....(4)

so with a, J and b known... how are we going to find the value of c since there is going to be exponential part to be solved... hmm i ask around and i was told that by bringing everything to one side and then solve by trial and error.. i would be able to find the unknown values.. but i have been trying and cannot seems to get it...

if (J *1.54*10E-6*(((6.44*10E-9 * c^3/2)/B)^2)exp(10.4/sqr©)/c - a =0

IS THIS RIGHT???

[fraser_drinkwater]

Definition of: veni, vidi, vici

veni, vidi, vici: I came, I saw, I conquered. (The laconic despatch in which Julius Ceasar announced to the Senate his victory over Pharnaces.)

[2559B]

<< Definition of: veni, vidi, vici

veni, vidi, vici: I came, I saw, I conquered. (The laconic despatch in which Julius Ceasar announced to the Senate his victory over Pharnaces.) >>

well done swiggi ! --- first person to get it!!!!! ( there goes my little bit of mystery )