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Old 10-01-2018   #46
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Quote Originally Posted by Candisa View Post
My Doblo seems to have this VL39 turbo as well after closer examination.
After some time on Google and trying to understand some Italian things written about the VL39, the VL39 is an improved version of the VL37 with some changes to the impeller side.


By the way: the boost-by-gear limitations in my Doblo's ECU are now removed, which drastically improved performance in low gears up to 4000rpm. However this now also means the lifeless top-end is accentuated.
I've talked about the possibilities with further ecu tuning without hardware changes, but most potential is in the 2k-4k rpm range. At 5k rpm power can be boosted 20hp to about 140hp, which is a very tame improval over the 60+Nm torque that can be gained lower down.

My Doblo T-Jet, and probably also the Tipo and 500L are apparently very similar hardware and software wise to the Alfa Romeo Giulietta 1.4TB 120 Euro6, which differs a bit from the older (Euro 5) Grande/Evo Punto or Bravo 120hp versions.
Have you tried using the Abarth Essesse boost sensors?
Along with a higher octane fuel such as shell vpower to help avoid knock you could gain worthwhile performance for little outlay.
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Old 10-01-2018   #47
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Quote Originally Posted by mattfred View Post
Have you tried using the Abarth Essesse boost sensors?
Along with a higher octane fuel such as shell vpower to help avoid knock you could gain worthwhile performance for little outlay.
I always start and once in a while drive on Total Excellium 98, and I drive most of the time on LPG which has an octane of 110-120.
The Esseesse MAP-sensor isn't necessary on the stock turbo, the stock MAP-sensor is rated up to more pressure than any of the IHI's can deliver.
The problem is the stock camshafts have too little lift and duration to let enough air in at high rpm. Pushing lots of boost could overcome this, but that requires a larger turbo (or at least compressor wheel).
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Old 11-01-2018   #48
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Re: T-Jet 120hp 'Chip-tuning'

Changing to na 1.4 16v cams plus big turbo is OK if you're searching for 200+bhp but if you want to keep the regular turbo a mild boost increase from the standard 1bar to 1.3 bar ss will increase power! Think the turbo is rated at 1.5 bar so there is a little scope. Nothing can change the standard turbos max capacity which is close to its performance limit!
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Last edited by mattfred; 11-01-2018 at 19:43.
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Old 11-01-2018   #49
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Re: T-Jet 120hp 'Chip-tuning'

I now (stock boost levels) have .7bar boost between 2k to 4k rpm, afterwards this quickly drops to .4bar and eventually .2bar.
I don't need much more torque in the mid-range, or I would need to reintroduce boost-by-gear restrictions to keep wheel torque manageable in 1st and 2nd gear.
I would like the torque to stay up higher up in the rpm range to get some more top-end power. I know it's safe to bump peak power from 120hp to 140hp without any hardware changes, but would a stock T-Jet120 VL37/39 be able to usefully push more than the stock sensors can handle in the 4.5-5.5k rpm range?

I keep the possibility for the NA cams and bigger turbo (probably modifying the stock one to VL36/38 spec for legal reasons) in the back of my mind, but I have other automotive and other priorities for a while, so the stock turbo and cams will have to do for now.
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Old 11-01-2018   #50
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Re: T-Jet 120hp 'Chip-tuning'

Nothing can be done .. the vl37 is very restrictive... the compressor housing just won't let more air in.
The inducer is to small.
https://www.fiatforum.com/gallery/da.../IMG_02651.JPG

The vl37 has ~2cm inducer
The vl36 has a 2.5cm (or2.8cm don't remember) diameter inducer.
That is the only passage way air enters the turbo=>engine.
So you can see how a small 5mm larger diameter will lead to 56% inprevement in surface area (possible air going to the motor)

Turbo, inducer diameter cm:, surface area cm^2, increase:
vl37 2 3.14 +0%
vl36 2.5 4.91 +56%
vl36 2.8 6.15 +96%
Thanks Candisa thanked for this post
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Last edited by aurick86; 11-01-2018 at 22:27.
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Old 12-01-2018   #51
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Re: T-Jet 120hp 'Chip-tuning'

I've seen this when I installed my intake.
It's a very small little thingy indeed, I should check and measure my VL39.
( link direct to the post about the intake in my Members Motors thread: https://www.fiatforum.com/members-mo...ml#post4248384 )

As far as my memories from physics class go, for a given compressor size the maximum pressure that can be created is inversely proportional to the amount of flow you want out of it, right?
By that logic, and since an engine demands more air the higher the rpm's go, esseesse sensors might allow more boost at very low rpm, but there's no chance the stock turbo (and probably even the VL36/38?) is able to exceed the maximum boost pressure of the stock sensors at med-high to high rpm.

The curves I've seen for max safe potential performance on the stock hardware shows all the torque at low rpm I could ever want with road tyres and an M32 gearbox (about 280Nm), but this amount of torque starts to drop even sooner than stock: at around 3.5k rpm instead of 4k rpm.

My conclusion about the esseesse sensors is that stock sensors might be a limiting factor up to 3.5k rpm, but above that it's just the simply physics and it would take a significantly larger turbo (such as the GT1446 from the esseesse packs) to see real high-end benefits from replacing the stock sensors.

Since it is my ideal goal to extend the torque I already have higher up in the rpm range, matching or exceeding the power and rev-happiness of my previous 170hp NA 2.4l 5cylinder powered car (weight was similar to the Doblo), I don't need more boost (theoretically .8bar at peak-hp should suffice), I need much more airflow (turbo, camshafts) and maybe fuelflow (injectors).

Am I thinking the right way in this?
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Old 12-01-2018   #52
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Re: T-Jet 120hp 'Chip-tuning'

I can't correctly explain it.. because i don't understand it either... ut i'll try:
-When i replaced the stock vl37 turbo with the vl36, the max boost stayed the same (because it's electronically controlled)... but even so.. the max power measured on a dyno was at 148 hp WITHOUT A TUNE..... so that means that there was more airflow. (sadly i don't have a dyno run wit the stock turbo; even if mine was one of the t-jet 120 that have much more than factory specs say 130hp..there's still a big power increase).

Mighty Car Mods ..had similar results when they upgraded the turbo on Moog's Subaru.

On my car with the vl36 it revs nicely to the red line now... doesn't dye after 4k rpm.

The Cams will give you more power....if paired with a turbo that can keep up with them;
But i think the boost will fall off even sooner (on the stock turbo).. the turbo inducer will be the bottleneck.

At the same time.. NA cams have overlap.... that might cause problems on a small turbo .. the pressure in the exhaust before the turbo (right at the valves) si going to be 2-4 times bigger than the pressure in the intake.. you would need a bigger turbo with an even bigger exhaust housing (like a TD04) which will have a smaller pressure ratio (exhaust pressure/ intake pressure).
Read this for more info:
Turbo exhaust theory
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Last edited by aurick86; 12-01-2018 at 14:21.
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Old 12-01-2018   #53
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Re: T-Jet 120hp 'Chip-tuning'

There is some margin in the amount of boost the stock turbo can deliver, which can be unlocked through ECU tuning and maybe even the esseesse sensors, and is great if you want to create a diesel-like "torque monster".
I find there is plenty of torque in my stock T-Jet 120 now the ECU has been reprogrammed to deliver full stock torque in 1st (originally limited to 105Nm), 2nd (orig. lim. to .4bar of boost), and 3rd gear (same as 2nd). I am already negotiating for grip without the interruption of traction control now due to the short gear ratios.

If I ever want to tune it further I would keep torque level the same in low gears, but I would like the engine to behave more like a bigger naturally aspirated one by keeping the boost up or even slightly rising higher up the revrange with help of a turbo that supports the required flow.

Changing or modifying the stock turbo to VL36/38 spec definitely is step n1 to increase flow. There are even bigger popular turbo's for the T-Jet, like the GT1446 (esseesse spec) or TD04-13 (the stock turbo of Moogs Forester that ended up on Marty's MX5). Those are fantastic options for the Punto and I would go straight for one of those if I owned a Punto, but the massive turbogap those "horsepower monster" turbo's create down low is probably not the best idea on a ridiculously heavy Doblo.

148hp without even a tune is a fantastic result and can probably be brought close to 160 with some optimization in the ECU.
Do you have a roll-out of that dyno-run, I'm curious to see the torque curve of a T-Jet 120 with a VL36 turbo?

Did yours die at 4k rpm before the turbo swap?
Mine rolls off at that point, sometimes more noticeable than other times, which is really a let down when you're used to naturally aspirated 2.0-2.4l 120-170hp engines that happily and linearly pull beyond 6k rpm. I own the Doblo for almost 2yrs and 50k km now and I still can't get used to it being so gutless beyond 4k rpm, it almost feels broken to me.
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Old 12-01-2018   #54
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Re: T-Jet 120hp 'Chip-tuning'

Quote Originally Posted by Candisa View Post

Do you have a roll-out of that dyno-run, I'm curious to see the torque curve of a T-Jet 120 with a VL36 turbo?
Yep.. here's the graph

194ps after tuning (it's also decat)... that's why I say you only need a vl36 (or mod your's to vl36 size) and you'll be anywhere around 180 with a good tune.

I'll be swapping out the injectors for slightly bigger ones soon(the Corsa 1.6T are direct fit), and the intercooler as well, mostly for safety...and i also want to know i have new injectors.. the car's almost 9 years old and 200k km... so she deserves them.

The stock 0280158167 (267 ml/min @3.5bar) injectors are about maxed out at the power i'm running.
The Corsa ones 0280158108 (304ml/min@3.3bar, or 320ml/min@3.5bar) will be fine for about 220 hp..maxed out..or a safe 200 at about 90% duty cycle.


Quote Originally Posted by Candisa View Post
Did yours die at 4k rpm before the turbo swap?
Yes... sort off... you'd feel the torque dropping off a lot and the engine just didn't feel that happy.
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Old 12-01-2018   #55
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Quote Originally Posted by aurick86 View Post
Yep.. here's the graph

194ps after tuning (it's also decat)... that's why I say you only need a vl36 (or mod your's to vl36 size) and you'll be anywhere around 180 with a good tune.
That stock cat must be a serious restriction to reach such numbers with just VL36 and decat, no cams, no injectors!

I've had a look at the website of Squadra tuning, who took care of my low gear limiters already and is well known in the Italian car tuning scene AFAIK.
They claim minimum 170hp at 5.3-6k rpm for the Bravo T-Jet150 which has more lift on the cams than the 120 but not like the NA, but ofcourse does have a cat (same as T-Jet120?).

I don't plan on doing anything to the stock exhaust system because of the strict regulations here in Belgium.
Cams also don't seem to be worth it as also the VL36 would probably run out of flow before the T-Jet120 cams become a restriction (I could live with power dropping off beyond 5-5.5k rpm).
Injectors probably aren't an issue either with +-170hp, which also eliminates the need to make alterations to the LPG hardware.

What I find important is what I see in both your graph as the one Squadra promises for the Bravo T-Jet150: excellent torque throughout the useable revrange: 200+Nm up to 6k rpm. This means if I don't boost low end torque in low gears, I can easily create a flat line from 2.5k rpm to well beyond 5k rpm and get the wheel torque needed keep up with most cars on the road from standstill to 70+km/h, probably 80km/h if I rev the engine out in 2nd gear.
Not bad for a Doblo!

As I said before, I have lots of other priorities and I have failed to grow money on trees thus far, so this is all future and maybe, but it seems VL36 spec modifying my stock turbo is the way to go for my expectations.

Thanks!
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Old 12-01-2018   #56
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Re: T-Jet 120hp 'Chip-tuning'

You could get the vl36 compressor housing for less than 50 euro; they also have the hot side for ~50 euro.
Then the CHRA (assembeled/balanced) is about 150 euro from Nerings in Latvia(ebay).. so 250 euro for a complete new vl36 turbo with good parts.

You could simply swap your's in at emmisions testing time..


That aside, the LPG system i am running is capable of max 160HP with the components it has now.
It would involve changing the lines, evaporator and injectors to be able to handle ~240 hp what was recommended by the tuner... he says an LPG system needs a lot of power margin in order to be able to keep up with the engine.

So i've just set it up to switch to petrol above a certain RPM + boost pressure ...(~140hp). I can still cruise on LPG at any legal speed before it switches to petrol.
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Old 12-01-2018   #57
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Re: T-Jet 120hp 'Chip-tuning'

That's cheap! Thanks for the link!

My LPG system now switches to petrol at 5k rpm, and since I don't really want more torque, just extension, so it'll probably keep up if I go VL36
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