Hey Guys,

This is way offtopic but there are some smart math ppl in this forum :P

I am having problems with my HKS EVC, I think my 4mm boost line might be too long - resulting in the EVC having a delayed response to high boost.

Is there a formula or something I can put some values in to work out the delay for say 20psi at one end of the vacuum line to travel to the other end?

Cheers
Dave

 

Speaking from a mathmatical handicapped perspective (trial and error from 100's of different variations), for increased response to WGA limit the length from the unit to the WGA and keep ID diameter of tube smaller. The length of the line that goes to the unit (not from the unit) doesn't really matter unless the diameter is small but try to keep that one a little larger for sufficient volumes of driving pressure.

So basically, for supply (to the unit) use larger ID = increased psi and volume, for reaction time from the unit use smaller ID = increased velocity

Sorry I'm incapable of providing a formula for you to plug it in to, but it all boils down to Bernoulli's principle which can be googled

 

Damn dude, I could give it to you if I had one of my old text book's from college here. I know there is a way to do it, and I can imagine it is very similar to calculating head loss from a pump. Since your turbo is basically a pump, you could calculate the head loss over a section of pipe (Tubing), but as for the "delay" of when your turbo spits out 20 psi, to when it reaches the end of say, 4 ft of 4mm tubing, eh, well, I don't even want to think of that. You are almost calculating how fast the sir is being compressed in the pipe from say 0 inmg to 20psi. It can be done, but the real questions I have is: What is going on over there?

Sounds like you are trying to trouble shoot a slow reacting HKS EVC, so my questions is: What is going on to make you think that this might be a problem?

Reason I am curious, is I have a very rock solid boost curve, as well as when my logs of boost are plotted, it's not wavy in the least bit. I have a very unique set-up where I have an Eagle vacuum distribution block mounted in the triangle of the strut bar, inline of my brake booster line. All my vacuum actuated sources are run from there. Because all of my sources are run from there (Gage, Boost Controller, FPR etc..) The periphials seem to work a little better because a lot of the "Pressure pulsations" from the manifold are taken out due to the distance of pipework. It might indeed make them run a little "slower" due to the length of pipe, but it seems to make everything work more accurately.

Well, it's either Foor for thought, or just Miscellaneous ramblings..

 

Im definitely getting that vacuum block. Ive had such a mess of vacuum lines that i dont trust just havent ordered that dam block yet. Funny thing is i was going to buy one over at Swift and i was like how much for the vibrant block he was like 50$ i put it back and said i was all set.lol. Then a friend buys 4 vibrant t bolts they charged him 70 bills i was like dude ur dumb.

 

EVC problems

well if I set the wastegate boost value to what its meant to be (10.7ish psi) then I get this weird clipping/stuttering of boost when its spooling... also it will overboost like crazy..

I can fix the over boosting by dialing back the "offset/gain" on the EVC but then my boost tapers too much by redline..

either way the stuttering/clipping affect never goes away... and you can see it/feel it in the logs... its like the EVC is either fully open or full closed, so the boost tends to bounce up and down.. wierd

anyways manual says make the "boost sensor" line as short as possible, but because of the position of the BCS it makes it hard - its about 3ft atm

 

I have my EVC bolted right under the intake in front of the battery. My lines are only about 18" at most. I have never had a problem with it. But then again I dont have the screen just the boost controller box itself.

 

same place as me, I am bolted on the factory BCS bracket

the which EVC you got? do you know what settings you are using?

on the latest EVC you need to run a 4mm (as well as the 2 control hoses: turbo+actuator) vacuum line from the intake mani - presumably so the EVC knows how much boost there currently is...

 

I actually got mine in the car when i bought it. No screen just the actually evc controller. All i have on mine is the a volume and b volume. One is set for DD the other is all the way to the max for racing. Matter of fact i believe i have the stock size (not sure what mm that is ) vacuum line running to the evc vacuum controller and for the waste gate and inlet i have the larger line running both of them. Yah and mine is in the same spot bolted down. Sorry im no professional in any of this for more accurate answers. I kinda just figure things out doing them myself i like it that way.

 

wonder what the effect would be to fudge the wastegate input higher/lower than 10.7?

 

Bernoulli's principle:
flow rate in cu. ft/sec = cross-sectional area of pipe in ft² x flow velocity in ft/sec

 

if I put the wastegate input higher then I dont overboost as much but then I taper the same...

 

Set the initial boost at like 12.6 or so, it should help with the clipping you are seeing.

Then you need to use the RPM based set-up. You'll need to set up your RPM points also, at about every 400-500 rmps, so that it knows when to do what you want it to do. I think this is the RPM axis grid point set mode.
“5” Value = (rev limit – 400 rpm) Typical value 7600 RPM (shown as 76)
“4” Value = Value of “5” – X rpm) Typical value 7100 RPM (shown as 71)
“3” Value = Value of “4” – X rpm) Typical value 6600 RPM (shown as 66)
“2” Value = Value of “3” – X rpm) Typical value 6100 RPM (shown as 61)
“1” Value = (RPM where boost begins to taper. Typical value = 5600 RPM

Offset Map Correction Mode:

1st RPM Offset value Always 100
2nd RPM Offset value 110
3rd RPM Offset value 135
4th RPM Offset value 170
5th RPM Offset value 190

These numbers allow the actual holding of the boost and can be adjusted if you are not happy with how it hold the boost. Once all values have been entered. Push the round button to accept the values.This will dial out the taper. Push the lower button 3 times to return to the main boost setting/monitor display screen.

If you are confused PM me.

 

P2-P1= 4(rho)(f)((L2-L1)/(D))((v^2)/2)

P2-P1 is your pressure drop [pa i believe]
rho is density of fluid (in this case air [kg/m^3])
L2-L1= length of pipe [m]
D=diameter of pipe [m]
V=velocity in pipe given by mass flow rate divided by cross sectional area
f= fanning friction factor, empirical value--> you have to look this one up for the rubber hose

that should give you a good approximation of your pressure drop due to friction in your vaccum lines, of couse this does not account for any bends in the hose, there are more relationships for that

 

hrmm thanks guys...

yep setting the initial/wastegate boost up a bit fixes my clipping problem but then i taper like a biatch!

I didn't really want to use RPM/map based fixup.. hrmmm what a pita

 

Yes, it's a pita to set up, but once you do, you can change the boost to whatever, whenever,(with the proper tuning) and still have no boost taper.