Finding the best possible spool of the turbo

[A80Avant]

I need to try something to rule out a possible mechanical failure of the exhaust area of the engine.

Since my ongoing issues of later spool since vemsupgrade, and the inability to get it where it was, i need to try and see what is the fastest spool possible that i can get.

How can i try this?

I can use a fuel cut at about 1.5bar or something so that i dont spike. How can this be done? should i take the hose from the compressor of the turbo and plug it directly to the lower chamber of the wastegate to always keep it shut? or is it something else?

[EspenW]

Disconnect the hose going into the lower chamber (and upper chamber if any)

[A80Avant]

and plug them?

[DJones]

I need to try something to rule out a possible mechanical failure of the exhaust area of the engine.

Since my ongoing issues of later spool since vemsupgrade, and the inability to get it where it was, i need to try and see what is the fastest spool possible that i can get.

How can i try this?

I can use a fuel cut at about 1.5bar or something so that i dont spike. How can this be done? should i take the hose from the compressor of the turbo and plug it directly to the lower chamber of the wastegate to always keep it shut? or is it something else?

If you are using a standard wastegate your compressor hose connected to the top will keep it shut as pressure is applied pushing the wastegate shut.

Just be careful with your timing map as you may of added lots of advance to overcome late spool which will now potentially have increased boost in the same area due to the method mentioned above introducing knock.

Darren.

[A80Avant]

i was told to use less advance to overcome late spool!!!

in any case anything above 1.4bar has about 15-16deg only.

i have the OEM rs2 wastegate. normaly use the turbosmart version 2 connection using top and bottom port.

so what you are saying is to connect the compressor exit to the top chamber? not the one audi uses(bottom that is)

[DJones]

i was told to use less advance to overcome late spool!!!

in any case anything above 1.4bar has about 15-16deg only.

i have the OEM rs2 wastegate. normaly use the turbosmart version 2 connection using top and bottom port.

so what you are saying is to connect the compressor exit to the top chamber? not the one audi uses(bottom that is)

My experience has always been to use more advance to try and overcome late spool and rapidly reduce the advance as the boost comes on.

Yes top chamber, the bottom chamber is to push the valve open whilst working against the spring pressure. The top chamber will push the wastegate shut in the same direction that the spring is pushing.

[A80Avant]

so ill connect the hose from compressor to the wastegate and unplug the N75 to test
thanks

about the timing, ill leave it as it was before as i want to see the ideal outcome and compare.

thanks

[EspenW]

Good point about pressure hose into top chamber, as that will push the valve closed.

Two schools of thought on timing vs spool:
1) Advance timing to make up for less cylinder pressure
2) Retard timing in order to increase EGT, thus aiding spool

[A80Avant]

tried them both schools... no real difference.

i need to see if there is a mechanical issue with my spool so i can more comfortable blaming vems boost control for it!!
haha

[gnutz2]

When i ran boost control through my ecu (dta) it was ok.

It used a duty cycle vs rpm map so i would run a high duty at low rpm to keep the gate shut, then when it started to make boost it started to lower the duty cycle.

This was ok but every gear makes boost at different rpm's.

Then i bought a stand alone boost controller (Gizzmo MS-IBC) and wow what a difference it spool'd up a hell of a lot quicker.

Alot of the good aftermarket boost controllers have an adjustable gain which stops the gate seeing pressure until the the boost is at a preset level. This also resets in every gear.

Also a ball and spring (mbc) does exactly the same thing.

[A80Avant]

i have tried a turbosmart boost controller without the ball and spring and it didnt work. It overboosts(although without the ball and spring it shouldnt) and then it tails off not being able to hold boost steady.

[jade]

[QUOTE=A80Avant;531985]so ill connect the hose from compressor to the wastegate and unplug the N75 to test
thanks



If you are going to do that, why not T the line to bottom and top port then the wastegate should work properly with more holding power

[A80Avant]

i did the test with some odd results i might say

on the tacho of the car i was getting a fuel cut which was set to 300kpa slightly before 4000rpm on 3d and well before 4000rpm on 4th, as excpected from when i had megatune instead of vemstune.

plug up to see the files and vemstune shows again that the fuel cut happened well after 4000rpm!!!!

either vemstune is reading the rpm wrong or i have an eye problem

[Billman]

Do a test. When in neutral let the car rev to 4000 and then check if vt reads the same. Maybe as the rpm increase you have a deviation.

I think that I also noticed something like this in some logs. I think I saw 1 bar sooner on the dash as in vt but I thought that maybe I was not paying much attention.

[A80Avant]

they are saying that vems CANNOT be wrong, and i believe them, but surely there is a calibration sequence somewhere...