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T-Jet 120 boost-by-gear? (Doblo)

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T-Jet 120 boost-by-gear? (Doblo)

Candisa

Candisa

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Hi,

From the beginning I have the feeling my 2016 Doblo T-Jet limits torque/boost in first to third gear: 60-80km/h just feels faster in 4th than in 3rd.
Now since I've installed an open air filter with very short, almost straight piping between it and the turbo, I can very clearly hear the turbo do its magic, which sounds a lot louder in 4th gear and up than it does in 1-3.

I'll have a boost gauge installed soon, I'm going by "butt dyno" and sound at the moment.
I don't mind a tame first gear to spare the clutch and gearbox, but the heavy (even when empty) Doblo could use a bit more "go" in 2nd and definitely in 3rd, "go" that I would think is actually there but only unleashed in higher gears.

Is my feeling that the T-Jet doesn't unleash all its performance until 4th gear?
If so, would that be a feature that can be adjusted/disabled by the dealer, or could it be tricked to give full performance in lower gears?

The more I think about the cost and risk involved in upgrading the turbo/injectors/exhaust/mapping (which is actually illegal in my country), the more I'm focussed on first trying to unleash what's there and see if that's enough.

Isabelle
 
I've got a boost gauge installed today: suspicion confirmed:
1st gear: no boost
2nd and 3rd: 0.3bar
4th and up: 0.7bar
No changes with ASR off

I also did some acceleration testing and it is in line with the numbers: I get the best acceleration when shifting to 2nd gear soon, go high in the rev range, and shift straight to 4th.

I will contact a reputable chiptuning company soon to ask if they can remove this limitation in 3rd gear and maybe dial in a little more boost in 2nd gear.
If this is possible, combining the gearing of 3rd with the boost I now only get in 4th+ should make a noticeable difference in the 50-90km/h time even if I don't gain a single hp or Nm.

Maybe this trick could be enough to satisfy me and save me the money, risks and turbolag of doing a turbo+injector upgrade.

To be continued...
 
Before contacting a chiptuning company, knowing the actual power gains without hardware modifications is very limited on a 120hp T-Jet, I contacted Fiat support.

I told them I have the feeling of lacking performance in low gears and my findings based on the numbers my boost gauge is showing.
I told them this "feature" is nowhere mentioned, definitely not in the brochure, so I feel a bit ripped off paying for a turbocharger system that doesn't do much when accelerating, and I want a software update that at least disables the limitation in 3rd gear.
I also told them I understand limiting torque in 1st and 2nd gear for driveability and reliability, but unless they have absolutely no faith in their gearbox design, limiting such a low powered drivetrain all the way to 3rd gear is just ridiculous and smells like false advertising.

They've told me they'll forward my complaint to the technical support and try to work out a solution in cooperation with my Fiat specialist, plus they gave me a case number, so I'll know soon enough if they're taking my complaint seriously.
 
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Fiat service as we all know it:
- My Doblo meets the requirements, although nowhere in the brochure is it mentioned maximum torque is only available in 4th+ gear.
- If it was so important to me I had all torque available in low gears I've should have asked about this when I ordered it, as if it's normal...
- My Fiat Specialist got blamed for selling me the wrong vehicle for my needs and "he should have known this".
- If I dare to pay somebody else to remove this restriction, even without changing anything else, "I will lose all warranty and service".

I wonder why Fiat has such a bad reputation...
 
Because I kept arguing it is misleading to advertise performance that isn't available in normal driving situations (the brochure says "206Nm", not "206Nm in high gear"), Fiat service agreed to look further into it.

In order for them to better understand my issue, they asked my Fiat specialist to do a monitored test drive, recording the boost pressure in 1st to 4th gear from 2k to 4k rpm.
My specialist confirmed the readings I've got from my analog boost gauge and the rather lazy acceleration in 3th gear compared to 4th.

Let's hope Fiat finally agrees 3rd gear performance is unnecessarily limited and is willing to do something about it.
 
Update: Fiat agreed performance was limited in low gears, however they claim this is normal behaviour and basically told me I should have bought a diesel if I wanted torque. :eek:

I got in contact with a well known FCA tuner in the Netherlands which name's starting with an S.
They have read out the software and for now only found a serious torque limitation in first gear (only 105Nm!), which has been removed.

Result:
- .5 bar of boost on flat roads and an empty cargo area (probably limited by the low load) instead of zero boost in 1st gear.
- Since I'm getting .7 bar in high gears, which should be corresponding with 206Nm (dyno tests of stock T-Jet 120 cars show closer to 230Nm), I think I'm getting 160-175Nm now, which isn't bad on very low gearing.
- instead of barely being able to break traction on wet roads with a full throttle launch, it's now up to me to feather the throttle just right to not smoke my front all-seasons tyres while already rolling. :eek:

Exactly what I want in a car: performance limited by skill and physics rather than helicopter nanny software! :)

Unfortunately this is only a small taste of what's still in the works, as the performance in 2nd and 3rd is limited in a different way they couldn't immediately figure out in the time frame I was there, so once I'm out of 1st the party's over. :(

However they now know how the Doblo behaves and they have the software, so it's only a matter of time before I get an invitation to go back and hopefully have 2nd and 3rd gear finally sorted.

I'll keep you posted!
 
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Candisa said:
Update: Fiat agreed performance was limited in low gears, however they claim this is normal behaviour and basically told me I should have bought a diesel if I wanted torque. :eek:

I got in contact with a well known FCA tuner in the Netherlands which name's starting with an S.
They have read out the software and for now only found a serious torque limitation in first gear (only 105Nm!), which has been removed.

Result:
- .5 bar of boost on flat roads and an empty cargo area (probably limited by the low load) instead of zero boost in 1st gear.
- Since I'm getting .7 bar in high gears, which should be corresponding with 206Nm (dyno tests of stock T-Jet 120 cars show closer to 230Nm), I think I'm getting 160-175Nm now, which isn't bad on very low gearing.
- instead of barely being able to break traction on wet roads with a full throttle launch, it's now up to me to feather the throttle just right to not smoke my front all-seasons tyres while already rolling. :eek:

Exactly what I want in a car: performance limited by skill and physics rather than helicopter nanny software! :)

Unfortunately this is only a small taste of what's still in the works, as the performance in 2nd and 3rd is limited in a different way they couldn't immediately figure out in the time frame I was there, so once I'm out of 1st the party's over. :(

However they now know how the Doblo behaves and they have the software, so it's only a matter of time before I get an invitation to go back and hopefully have 2nd and 3rd gear finally sorted.

I'll keep you posted!
Click to expand...
Do you think it's for safety reasons, economy/emissions or to protect the gearbox? I have a Twin Air Panda - and I think it does the same. It feels like the Turbo isn't doing much until you get to 3rd gear and above - then it pulls much more strongly. I particularly notice it coming out of slow bends in the road.
 
I don't think it's for safety as that's what ESP and traction control are invented, which comes standard nowadays.
I strongly suspect it's mainly done to score good on the standard economy/emissions tests. Torque really isn't high enough for parts wear to be an issue with Fiats petrol drivetrains, and many components including the clutch would wear in high gears just as hard if it were an issue.

Secondary the torque limitation in 1st (only in 1st) could be to nanny the driver so the traction control doesn't kick in when they floor it in 1st, but that's no excuse for limitations in 2nd and in my case also 3rd.

Greetings,
Isabelle
 
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Update: the boost-by-gear limitations are now completely removed, which means my turbo now happily whistles .7bar of boost into the engine in all gears between 2k and 4k rpm, and the drivetrain now basically has more torque than my all-seasons tyres can transfer to the Belgian asphalt when launching in 1st or accelerating out of a sharp corner in 2nd if I put my foot down. :p
This also means my 3rd gear is now actually usefull instead of just for cruising at 40km/h (aka never). :)

The downside, apart from actually having to feather the throttle properly to hold traction in 1 and 2, is this now accentuates the lazy (understatement) 4k+ rpm top-end of the T-Jet 120.
The unlocked, not even tuned torque makes the needle just fly from 2 to 4k rpm, only to reveal it only soldiers on to 5k to reach the 120hp claim in the brochure.

This 120hp number at 5k can be safely boosted to 140 without hardware changes, but that would also mean I should opt-out for the 60+Nm potential torque gain down low if that measly 20hp gain wants to make the stock T-Jet 120 setup feel a bit more natural.
I guess this is the downside of downsized engines in heavy cars.
 
Hi Isabelle,

How did the tuner management effect this? My T-Jet will be getting mapped once the new turbo is on and I'd quite like to have this limitation removed if it is straightforward enough.


Cheers

Ben
 
Hi Ben,

My mapping hasn't changed so far, I wanted this limitation removed to know how my Doblo performs with stock power available throughout all gears.

In my Doblo:
- 1st gear is a torque limitation which apparently is quite easy to adjust/remove
- 2nd and 3rd gear were limited by intake manifold target pressure in a map seperate from the normal boost/fuel/timing/... maps, which was apparently hidden quite well and relatively new for Fiat/Alfa.

I am not a tuner and I'm not one to fish after "secrets of the trade", but I would guess adjusting/removing these limitations is seperate from tuning the boost/fuel/timing/... maps and shouldn't affect one another.
Derestricting was a lot cheaper than normal "chiptuning", so I would expect this to cost very little when they're already "in there" to tune the usual things.

I've had my ECU work done by Squadra in Holland and I can't see a reason why I shouldn't go there again if I want to tune in modifications or just maximize the stock potential, despite it costing me a day's worth travelling.

Isabelle
 
Thanks, I'll get them to look at it when I get the mapping done. I don't think I'd want any torque limitations removed from 1st. It's already very easy to spin the wheels when pulling away quickly.

Cheers

Ben
 
Yeah, my Doblo was limited to 105Nm in 1st, but the tuner told me 150Nm is more common in other models. Since I still get a little less boost in 1 now it's unlimited, I guess I have +-170Nm in 1 now which is indeed more than plenty.

If I go further with my Doblo, I'll probably set 1 to 150Nm and 2 to stock torque level to keep things pleasant to drive.

Isabelle
 
Ben D said:
Thanks, I'll get them to look at it when I get the mapping done. I don't think I'd want any torque limitations removed from 1st. It's already very easy to spin the wheels when pulling away quickly.

Cheers

Ben
Click to expand...

You don't need the restrictions removed from first or second...even third needs some limiting.
Maybe just a bit more boost but definitely needs the limitations.
Mine still has them (mostly there...slightly raised) and it's way to easy to spin one tire (if i had an LSD it might be different), especially now in the sh*t weather.
Candisa might have different gearing...so it will be different for him.

The actual boost limitations are in multiple maps in the ecu.. it's not as simple as clicking a checkbox.
The work to remove them is similar to actually tuning the car for more power... but different in that other maps need to be modified.

The limitations are in multiple maps, so they can control each-other, so if it's not mapped correctly you will get errors...problems... or the limitation will still be in place.
 
aurick86 said:
Candisa might have different gearing...so it will be different for him.
Click to expand...
Her ;)

I have shorter gearing than a Tipo T-Jet120, and a bit more weight to get going, so my tyres are actually easier to spin. They even break free on wet concrete or dry cobble stones if I push on it in 2nd after fully releasing the clutch, but the +-206Nm in 2nd gear can be fully used on dry asphalt and the 105Nm in 1st was just ridiculously conservative.

The tuner told me most other models have a 150Nm limitation in 1st, which is probably all you need, so if that's also the case in your car I'd advise to keep that as is.
2nd gear doesn't need limitation with stock power, but you really don't need more either, so keep that to the stock +-206Nm torque or +-0.7bar boost.

I don't know if the potential 270-300Nm would be too much in 3rd gear, but 240-250Nm definitely should be useable, and limiting 3rd to something in between the 2nd gear limit and 4th gear full torque will also "bridge the gap" and feel more natural to drive.
This was actually the "problem" I had with my Doblo before derestricting: 1st (very limited) and 2nd (limited) were slow, but 3rd felt like something was wrong because it was limited identically to 2nd and 4th was a big step up.

So my recommendations for torque restriction based on what's possible with the IHI turbos:
1st: 150Nm
2nd: 200Nm
3rd: 250Nm
4th+: unrestricted

Isabelle
 
Candisa I'm sorry about that :eek:

The tune i have allows some overboost ... in all gears... so it feels more powerful than it actually is...and it's probably the cause for the spinning tire.
 
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