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Davezj
20-05-2012, 01:17 PM
Right just a quick one from me for the fist post.

senario 1:-
1. i have EBC boost set to 7psi which is about stock. and the start value is 0psi (start value is point at which the EBC boost valve will initially open, used to eliminate boost creep at lower pressures).
2. on WOT it get surging, the power builds, then drops off then build then drops off but the car is still getting quicker each time.

it is not fuel cut, it is every gear and every speed and when ever i go to to WOT.

Senario 2:-
1. set EBC start to 5psi boost still set to 7psi.
2. All serging effect have gone.
3. boosts and drives as i would expect it to.

i have repeated the above and i get same result every time.

i have done a boost leak test and i have no leaks at 15psi


what would this suggest to you?



i am drawn to a wastegate issue, one of the wastegate is not holding pressure at the start and opens and closes and opens and closes then continues to flutter open/closed as the boost rises.

does this sound like a possible cause

Wodjno
20-05-2012, 01:53 PM
Start boost should be set close to Target boost.5 Psi is a good start boost for a target boost of 7 Psi. Servitude too close and u will get boost spikes. Too low and you will get the issue u have described.

So for a Target boost of 13 Psi, a start boost of around 10-11psi should work well. But it will all depend on the make of boost controller/valve and the car/turbos.
Sent from my HTC Wildfire using Tapatalk 2

Davezj
20-05-2012, 03:30 PM
excellent, thanks glenn.

that is put my mind at rest.
i must have just been lucky the way i have set the controller up in the past. i have always set the start value just below the low boost setting. unfortunately the same start point is used for the hi boost setting as well.
so if i set the start point at say 6psi and lo boost at 7psi the it will be miles away from the hi boost setting of 14psi. but this has wlways seemed to work in the past.

i have a BCU+
with a turbo timer and external triggers.

i am not sure why i set the start value to 0psi, it was after the rolling road day at Area 52. i thought it would be less stressful on the turbos, if i turned the boost down to 7psi and the start value to 0psi as i think my turbos are getting tired and leaking a bit of oil. as i get some smoke out of the exhaust when i initially drive off after the car has been stood for more than 4hours or so. but only for about Half a mile of driving.
it will be either the turbos or valve stem oil seals.


but thanks again glenn for the boost controller advice much appreciated.

Davezj
30-08-2012, 01:41 PM
well i am going to continue with this thread
firstly the smoke from the exhaust was totally down to the start pressure verses requested pressure issue i had due to poor setup by me. as soon as i had 6psi start and 14psi request the smoke went away. which was good.

i have been turning my boost pressure up and up, whilst monitoring knock and AFR which seem good. i think i have reached the max boost pressure on my current setup.
i can produce about 1.4bar (20psi) depending on what gear i am in (slightly less in lower gears), but the boost pressure is starting to bounce anound at 1.35-1.5bar up and down up and down, when i keep my foot planted paricularly in 4th and 5th gear.

i came up with a few possibilities:-
1. i was wondering if this could be due to the standard recirc BOV that i still have fitted.
2. i thought it could be standard boost hose issue, but a hard pipe kit does not see to make any difference.
3. I know at these sort of pressures the inlet temp will play a part in the performance of the car, i am working on that and i have ordered a thermocouple and reader to fit in the car so i can monitor this properly.
it could of course be my EBC not holding the pressure correcrtly.
4. Turbos can't produce 1.4 bar continuosly and are building pressure then effectively stalling then building pressure again, or something light that.

am i beteer off just turning the boost down until a steady level can ge reached or try to do something about it. i would like to try and do something about it but it before i start playing with the ecu map to add more fuel where needed and remove timeing to get rid of what little knock i do have.

what do you guy think.

mike74
31-08-2012, 12:43 PM
i have a similar issue with the EBC on my Pulsar. If I set the 'gain' too high it spikes & slightly overboosts (BUT feels quick!) & if I turn it down I get less spiking (but feels slower). Your EBC doesn't have a similar setting does it? Also, how long are the vacuum/boost pipes that connect the solenoids to actuators etc? If they're too long, it'll almost always surge/spike as the physical distance the controller solenoids are from the actuators/inlet means it can't control boost efficiently. I can't remember where I read it but someone somewhere said that EBC solenoids shouldn't be more than 2-3 feet away from the actuators because of surging...
Hope this helps anyway :)

Davezj
31-08-2012, 01:38 PM
cheers for the info,
the p[ipes to the solenoid are long er than i would like them to be but i think they are about 1.5 to 2 feet long.
so yes i could shorten them down, as a starting point.

the gain is set so i don't get any spiking in Gears 1 ,2, 3, it is only in 4 & 5 when i have my foot to the floor from about 50mph the boost rises to max then drop off, then builds, then drops off, then builds, the cycle take about 2 second to build and then drop off.

i don't normally find myself doing about 50mph in 4th or 5th with my foot planted to the floor verry often, but it is an odd thing for the boost to be doing.

It could be the wastegate spings being over come by the boost level being delivered.

i could try disconnecting the boost pipe to the wastegate and see if the max boost of the turbo is stable, with no control on it. If it is not stable then i know it is the turbo that is the problem. it is not advised to run with no boost control at all but a short one off run will show the issue up or not as the case maybe.
i will evoscan the run just for fun.