Technical JTD boost fluctuating at full throttle.

[Shadeyman]

Full throttle in 4th gear boost is fluctuating plus or minus 90mbar(max).

Is this normal?

If it isn't normal what could be causing it?

 

[Yellow Peril]

Full throttle?! You'll be throwing the car around like an F1 driver soon...

 

[Shadeyman]

Full throttle?! You'll be throwing the car around like an F1 driver soon...

Flat out in 4th gear is about 95mph(I think) the last thing I, or anyone else, should be doing is "throwing" a Multiwagon about at that speed. :nono:

Although I have stupidly done 175mph on the M1 on 2 wheels when I was yonger. 60, 70, 80 MPH on the gently curves of a motorway is about as good as it gets for me now.

Edit.
Just found the screen shot of FES. Rolling start 2nd gear. Accelerated quiet hard through 2nd, then 3rd and finally you can see the "desired boost" flatten out in 4th but the "actual boost" fluctuating about 80mbar above and below the "desired boost". Also seemed to be overboosting while in 2nd gear, could this be due to the remap?

 

[richydraper]

sorry shades i work in psi!

anyway 33psi desired and its fluctuating between 32/34psi so thats roughly a 3% fluctuation... is this not 'acceptable' due to mechanical wastegate operation?

(yes i know i dont own a turbo lump)

 

[Shadeyman]

sorry shades i work in psi!

anyway 33psi desired and its fluctuating between 32/34psi so thats roughly a 3% fluctuation... is this not 'acceptable' due to mechanical wastegate operation?

(yes i know i dont own a turbo lump)

3% fluctuation does seem an acceptable amount now you put it that way.

Would the same apply to a Variable Vane turbo(the type fitted to my JTD)?

 

[richydraper]

VGT's only have Variable Geometry on the compressor side as far as im aware. there is still a need for a wastegate. i didnt realise they were VGTs on the dizzles... id suspect there is DEFINATELY scope for a 3% fluctuation in the controller for the vanes. youll probably find that the wastegate is working properly and this fluctuation is due to the reaction times of the vanes rather than due to the wastegate operation.

im not confirming or denying you have an issue just pointing out that IMHO 3% wouldnt be a reason for concern in an OEM setup for me!

 

[Shadeyman]

VGT's only have Variable Geometry on the compressor side as far as im aware. there is still a need for a wastegate. i didnt realise they were VGTs on the dizzles... id suspect there is DEFINATELY scope for a 3% fluctuation in the controller for the vanes. youll probably find that the wastegate is working properly and this fluctuation is due to the reaction times of the vanes rather than due to the wastegate operation.

im not confirming or denying you have an issue just pointing out that IMHO 3% wouldnt be a reason for concern in an OEM setup for me!

I'm pretty sure there is no waste gate on a JTD and I'm sure the Variable Vanes are on the exhaust side.

Edit.
Vanes are deffinately on the exhaust side and there's no waste gate because the boost is maintained, not dumped.

Low Load
When the load on an engine is low, the vanes on the turbo charger remain closed. Little exhaust causes flows across the turbine impeller, or rotor, producing little turbo charging effect.

High Load
When the load on an engine is high, the vanes on the turbo charger are opened by a servomechanism, or actuator, controlled by an electronic control unit (ECU), which monitors engine speed and load using sensors. This allows a stream of exhaust gases to flow over the impeller.
http://www.ehow.com/facts_8001924_variable-vane-turbo-charger-works.html

 

[richydraper]

dont listen to me then

id suspect there is DEFINATELY scope for a 3% fluctuation in the controller for the vanes. youll probably find this fluctuation is due to the reaction times of the vanes.

on a seperate note it seems a crappy way of doing it... VG on the turbine side (where all the crud is)... and not fitting a wastegate, what happens when the VG controller takes a funny and boosts the pipes off! nice one fiat

edit:- just read wiki and it would seem WG isnt required! World 1-0 Stain

 

[Shadeyman]

edit:- just read wiki and it would seem WG isnt required! World 1-0 Stain

I think the variable vane thing works well on small turbos, helping to maintain rpm and boost for when its needed.

However, large turbo's seem not to have variable vane geometary probabely for the reason you suggested "what happens when the VG controller takes a funny and boosts the pipes off", hence the need for a waste gate.

I'm sure modern diesels don't have a waste gate because they don't have a throttle.

Edit.
Just looked at my screen shot again.

Is 29 seconds to accelerate from 21mph to 95mph good or bad?

 

[richydraper]

ur asking a man who drives a 1.6 petrol LMAO

 

[Shadeyman]

ur asking a man who drives a 1.6 petrol LMAO

and I drive a tractor ... lol

She accelerates quite well from 21mph to 95mph concidering shes done 105,000 miles and is burning 100% bio. Just wondered if 29 seconds was good or bad ...

 

[sussexa]

that looks reasonable to me.
https://www.fiatforum.com/[URL=http...ntfesdata7911.png[/IMG][/URL] Uploaded with Uploaded with ImageShack.us
heres a 4th gear pull desired boost actual boost and vnt %.id be happy if mine was within 90mb, but at least i know why its not.
if you logged vnt as well i would imagine its opening and closing to match boost.
as i get no errors even with this overboost i wounder how much it has to over or underboost to trigger a eml?
just looked back at your log and what update rate was it on?time is every 5 secs, might look better on a graph logged every 1 sec or less if you can get it(i still struggle to get much over 60/min,sometimes luck and get 100/min)

 

[richydraper]

0-100kmh= 11.1 secs from what i can find

 

[emzo]

Here is mine on 4th gear
Gotta clean the turbo solenoid some day ...

 

[Shadeyman]

if you logged vnt as well i would imagine its opening and closing to match boost.

Tried it in 4th gradually putting my foot down this time, not just stamping it to the floor. Got an over boost spike for some reason?

Edit.
I'm not sure these readings are accurate, they seem to change, not very constant. :chin:

 

[sussexa]

accuracy wise i had a logging day a while ago and found most runs i thought would look similar didnt on graphs.
i thought you were remapped shady? 2314mbar=33.56psi-14.5psi =19psi isnt that standard boost?

 

[Shadeyman]

accuracy wise i had a logging day a while ago and found most runs i thought would look similar didnt on graphs.

Yeh thats the results I keep getting. :chin:

i thought you were remapped shady? 2314mbar=33.56psi-14.5psi =19psi isnt that standard boost?

The car is remapped, the max boost I've recorded so far is 2553mbar but as far as I know the system(turbo, sensors etc.) has a safe max of 3000mbar.

I think basically the remap enables full boost to come on earlier plus more fuel giving a lot more power earlier on.
Its made a big difference to performance between 2000 and 4000 rpm, she pulls like a tank.

I don't think the remap increases the max boost, just how the car uses it.

 

[Stilo Nutter]

I'm sure I read a thread on here saying that there are 3 MAP's for the diesels. JTD 80hp = 2000mbar - JTD 115hp = 2500mbar - Multijets - 3000mbar.

I could be remembering incorrectly.

* Found it - https://www.fiatforum.com/stilo/278925-tuning-my-stilo-jtd-turbo-upgrade-help-please-2.html

It's the first post on the second page, coincidently posted by sussexa.

He also posted links to the alfa forum that show at least one of the serious tuners have fitted to 3000mbar from the 16v multijets to their 8v JTD's

 

[sussexa]

i looked back to your earlier post on map failures and your desired boost was approx 2100mbar back then i think so maybe your std boost was 15psi and hes lifted it to 19psi.
looks like the extra fuel is causing the overboost as the vnt is close to fully open at 25% as the turbine overspeeds the boost spikes.
when im driving i rarely see overboost but when testing and logging its always driven harder so it always looks worse.
i finally managed to read my map with galletto but so far have only identified (guessed)half a dozen of 153maps on winols
and i also think yours is probably 2500mbar map

 

[Shadeyman]

i looked back to your earlier post on map failures and your desired boost was approx 2100mbar back then i think so maybe your std boost was 15psi and hes lifted it to 19psi.

looks like the extra fuel is causing the overboost as the vnt is close to fully open at 25% as the turbine overspeeds the boost spikes.
when im driving i rarely see overboost but when testing and logging its always driven harder so it always looks worse.

Shouldn't overboosting illuminate the EML?

i finally managed to read my map with galletto but so far have only identified (guessed)half a dozen of 153maps on winols
and i also think yours is probably 2500mbar map

I've been trying the same thing, its not easy to say the least. :shakehead:

So Stilo Nutter is correct, there are 3 default MAPs used on the different JTD engines?