How to make boost with stock stall with gt42

[orangeute338]

is it possible to get more then a few psi with the stock zf with big turbos? when i had the stock turbo i could get it to stall to 3k and 10psi now with the gt42 its going to 2psi and no much over 2k. ive heard people say retarding the timing brings boost on soon is that true? also is it better to have it richer or leaner(more heat) to bring the boost up? or its just to big and i need to put some nos on

here is a vid of me testing the stall

http://youtu.be/h8kgNDE1aa0

heres some pics of the install




cheers
Josh

[hiddeous]

Leaner will bring boost up quicker, also retard the came and ignition timing. Be mindful that you may get more boost due to higher airflow through the motor, but the retarded timing and cams may cost you torque and keep it off stall

[Huddo]

retarded timing brings the boost on earlier but at the cost of power, so effectively no gain is acheived

[orangeute338]

i tried setting the timing at 3 at 2000rpm and 1 and above on the table but if you see in that run it was high and only got to 12deg before i backed off, might have needed to hold it for a bit longer.

in general driving because it doesnt make boost till 3k would it be better to have the timing higher off boost more like a na to make more torque to help spool rather then low like the stock map because it has boost sooner? im going to look at getting some bigger cams and i have fixed cam sprockets already

[turbotrana]

I had an ED turbo where I changed to a bigger cam and lost about 5psi at boost at stall. I tried every which way but from memory having the timing advanced like a N/a ended up giving the best result for take off boost and running leaner from memory. I had the ability to alter the timing live.

Retarding timing works with Antilag but it needs a manual and revs for it to work but does build boost. No good for autos.

[orangeute338]

i tried more timing and leaner around 2k try and get some boost on the stally but nothing.

i did a 3rd pull to check my boost and its a bit fluttery i think i will have to get a flash box so i can log the wg error and tickle my dc table. does the fluttery boost cause the timing to be the same? it flutters between 8-10 you can notice it in the pull the power isnt 100% smooth

here is the tune and log run is torwards the end the first part is skating 1-2-3.

another thing does the ecu use the wastegate dc table at part throttle? i have commanded 1 till 4000rpm and i have i think about a 8psi external wastegate and if i go half throttle and rev it upto 3500-4000rpm and it starts to make boost it will open the wastegate at about 3psi. my thoughts were that there might be 3psi after the throttle body because its half closed but could have a lot of boost before the tb at the turbo which sends the boost ref to the wastegate if i got wot when the gate is cracked at 2-3psi it will shut. do people eva use the manifold for reference for the wastegate or off the front of the turbo is fine? i should commanding 1 upto 4000rpm it should send no boost to the wastegate but thought maybe part throttle didnt use that table or because i have closed loop boost it might be letting some boost through

[turbotrana]

You also got to accept that with something like a GT42 to just aint gonna get boost on stall without doing a stally.

[hiddeous]

[orangeute338]

yeah i just wasnt sure if there was any tricks to get it to spool. one thing i am considering it a quick spool valve block off one side of the twin scroll and is meant to spool quicker. i have a 125 wet shot i could put on if things get desperate also.

any ideas about the boost table is it used at part throttle or only wot? also in the desired boost table is it in kpa so 100 in the map would be no boost or 14.7? looking at the stock map it only commands 50odd kpa so made me think 100kpa would be 1bar boost then i got confused looking at the scanner because it is psia so 100kpa is 0 psi etc...

[orangeute338]

I found the on/off boost threshold and lowered the tp for when it uses the cl boost control and that got rid of the external opening at low throttle, I had the wg sonenoid closed till 4500rpm so
now doesn't open till then

[DarrylC]

any ideas about the boost table is it used at part throttle or only wot? also in the desired boost table is it in kpa so 100 in the map would be no boost or 14.7? looking at the stock map it only commands 50odd kpa so made me think 100kpa would be 1bar boost then i got confused looking at the scanner because it is psia so 100kpa is 0 psi etc...

Desired boost table is in inHG, so about 1/2 the reading is the psi. For example 29 in the desired boost table equates to about 14.5psi of boost.

[orangeute338]

Desired boost table is in inHG, so about 1/2 the reading is the psi. For example 29 in the desired boost table equates to about 14.5psi of boost.

you sure about that? i have my table at max 140 and i get about 20psi with that.

[DarrylC]

you sure about that? i have my table at max 140 and i get about 20psi with that.

Yes. I have not found a way to change its units so no matter what you set (Imperial/Metric) it stays the same.

You can set what every you like in the table doesn't mean the car will support it. I have my table set for 26 at 3000, 29 from 3500 -> 5500 and 27 at 6000. so the car holds 14.5psi of boost from about 3500 rpm -> about 5300 and then tails off to redline where it is holding about 13.5psi. Increasing the values from 5000 up does nothing to the boost as I am restricted by the exhaust and I could not get to 14psi@ 5000rpm until I changed the factory wategate actuator.

You might need to keep an eye out for the limit of the MAP sensor as well but others are better able to advise you on that.

[hiddeous]

Darryl is correct.

I doubt your going to see 70psi not matter what you do....

[JETURBO]

Remember just because you ask for it, does NOT mean you will get it

Logging before,during,after is the only way to be sure your getting what your asking for ( with in mechanical limitations )

[trbo 6]

My desired boost table is in kpa.

[VYSSLS1]

changing your desired boost table is not going to do anything, nor is the wastegate duty stuff,

to get boost on quicker the only way is to run LOTS of timing and lean, on auto cars on E85 i normally run 40-45deg timing and 14-15:1 afr on the petrol scale..

use at your own risk!!

if it wont come up at that you need a looser converter or gas