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View Full Version : So whats the "DIFF"? As in Differential? open, locking or "fake"?



deathshead
02-18-2012, 12:19 AM
Hi Guys, I posted this before on another forum but haven't gotten any real info..

Anyone have any info on the diff in the US spec Abarth?

My Current daily driver is a 05' Neon SRT-4 - ACR. The SRT-4 comes with a factory Quaife differential, while it can sometimes be a handfull.

(pull away from a light when turning, get into boost, think posi RWD getting loose-sideways but in the front. lol)


I dont know if I could live without a good differential in a FWD vehicle, having that outside right wheel on a hard right turn spinning doing nothing, straight line launches stink, etc.

With my srt-4 I can dump the clutch at 4k and the car will hook up and stay straight as an arrow, burn outs, again thumb and pointer finger on the wheel straight.
with open diffs it always seemed to fight or flat out stink having a "1 wheel peel"

Then we get into these terrible electronic diffs that just hit the brakes to the wheel spinning.
I had a Volvo 850 turbo wagon that had this and it was terrible, especially in the snow, left-right-left-right-etc and going nowhere.

Whats the deal with the differential in the Us Abarth? I searched a bit and I read that this is some sort of electronic locker.
Is this fancy talk for a fake "brake" diff?

For instance, the Caliber SRT-4 has a BLD, or Brake locking differential. and apparently all those guys HATE it.

When Chrysler replaced the Neon SRT-4 with the Caliber SRT-4 They cheaped out and ditched the $1000+ Quaife differantial and went with the Brake lock diff. Which is essentially a "fake" non locking diff. It uses its ABS sensors to determine if a wheel slips, then applies the brakes to the spinning wheel. Im hoping the Abarth does not have this system as it sucks and everyone hates them.

Does the Abarth have this abysmal system as well?
I cant even find a video anywhere with a nice burnout or launch..

A real locking differential isnt just for burnouts and drag racing, hah. Ask anyone who drives a light short wheel base car spiritidly or at the track with an open Diff.
(I used to drive a '92 Ford Fesitva with a Mazda B6 Swap.) Take a tight Hard right turn, especially on uneven, banked/hill tarmac and all you get is wheel spin..

Thanks, Cant wait to get me Abarth! Its like a new version of my old beloved Festiva, but with the potential to be as powerfull as my srt-4.

slowbird
01-03-2014, 04:00 AM
I found this online somewhere:



Unlike some small performance cars that simply use the front brakes to mete out traction to the front wheels, the 500 Abarth actually has a limited-slip differential. The differential is electronically controlled by the so-called Torque Transfer Control. The computer can adjust the amount of lock in the front differential, depending on how much traction is available. And to provide even more traction, the stability control system can selectively brake one of the front wheels to transfer engine torque from side to side. In essence, the 500 Abarth combines the virtues of a true LSD with brake-operated traction management. “You’ve got a high performance engine in a little car that’s pretty light,” Vincent said. “When you stomp on it, you want to go straight down the road.”

Read more: http://www.automobilemag.com/features/news/los-angeles-2011-six-things-we-learned-about-the-fiat-500-abarth-89141/#ixzz2pJuyAS2o

Me rod
01-03-2014, 08:37 AM
The Abarth has an open diff with an electronic brake distribution. Ignore the post above.

You can buy a 'proper' Quaiffe for it here: http://quaife.co.uk/news/quaife-atb-helical-gear-limited-slip-differential-now-available-for-the-abarth-500

jguerdat
01-03-2014, 08:43 AM
I've seen no practical evidence that there's any form of LSD on this car. Turn ESC completely off and you can spin an inside tire in a turn. ESC partially off uses the brakes for an emulated LSD but it's still not any form of mechanical limited slip. I've had a '97 Prelude SH that had the ATTS (Active Torque Transfer System) and used it when autocrossing (when it didn't go into a failure mode) - it acted like a limited slip but only in a corner. Nothing of the sort here.

BigDaddySRT
01-03-2014, 09:55 AM
I've seen no practical evidence that there's any form of LSD on this car. Turn ESC completely off and you can spin an inside tire in a turn. ESC partially off uses the brakes for an emulated LSD but it's still not any form of mechanical limited slip. I've had a '97 Prelude SH that had the ATTS (Active Torque Transfer System) and used it when autocrossing (when it didn't go into a failure mode) - it acted like a limited slip but only in a corner. Nothing of the sort here.

That quoted Article was written in November 2011 before the NA ABARTH even hit the Public Roads.

The NA ABARTH does not have a Mechanical Limited Slip Differential.

Me rod
01-03-2014, 03:50 PM
This is a very interesting article on Pistonheads explaining the difference between the types of LSD available. And I mean the engineered ones...

http://www.pistonheads.com/doc.asp?c=104&i=25275

Oh, Word?
01-03-2014, 03:51 PM
I had a 05 srt4 as well and now I have a 2013 abarth and I love it. It's got equal length axles which help A LOT. There's hardly any torque steer really and I drive my car pretty aggressively. I can't say what diff it has for sure but unless you plan on auto crossing you won't have an issue I've thrown it into corners real hot and it's not an issue these cars turn great. If nothing else you'll love that the fiat doesn't have the turning radious of a school bus like the srt. I generally don't hard launch my car but the couple times I have it spins them both no issue.

Crazy Otto
01-04-2014, 12:21 AM
The Abarth has an open diff with an electronic brake distribution. Ignore the post above.

You can buy a 'proper' Quaiffe for it here: http://quaife.co.uk/news/quaife-atb-helical-gear-limited-slip-differential-now-available-for-the-abarth-500

The euro cars are different so I wonder if this unit will fit usa spec cars. Quaife's us site doesn't list the unit.

Agree a mechanical Diff is best but don't find the abarth's to be bad. Haven't tracked it yet tho but does work well in winter. I just retired my winter beater 95 infiniti g20 t with viscous lsd and the fiat goes better in snow but that could be the tires graspic ds vs blizzaks.

Fiat500USA
01-04-2014, 02:49 AM
All US 500s use an enhanced traction control system. It is called Traction Plus in Europe, and is used in the 500L Trekking. Torque Transfer Control (TTC) is a subset of the Traction Control System (TCS). It works by applying the brakes during on throttle cornering and increases the torque bias in the open differential. It is similar to how TCS works but doesn't cut power. The TTC is nuanced enough to detect if you are just driving on slippery surface or are driving in a spirited way. I had a discussion about the system at a racetrack with the lead Abarth development engineer who also specialized in ESC calibration. Some of the ways they figure out what you are trying to do is with throttle opening values, for example, but it is an amazingly intricate and fascinating system. He set the car up with a certain amount of wheelspin coming out of a corner. There are pluses and minuses to any system, but it is important for an OEM to have a car that is predictable and not on the razor's edge of sharpness where normal folks can find themselves caught out if not paying attention. There has to be a certain amount of benign handling built in.

slowbird
01-04-2014, 03:32 AM
That quoted Article was written in November 2011 before the NA ABARTH even hit the Public Roads.

The NA ABARTH does not have a Mechanical Limited Slip Differential.

The intrawebs lied to me?

nnnoooooooooooooo :disturbed:

Fiat500USA
01-04-2014, 04:11 AM
You guys really have to read through the blog and my posts.gr_grin ;) Here's some info that I wrote before the car hit the streets and is in the sticky "Questions for the Abarth Engineers"


Hi Folks, Finally, here are some answers to some of the most asked questions. I had to work out the logistics to be in the right place at the right time. Thanks for your patience.


Question: In the Euro Abarth, the TTC has a separate switch while in the NA version there is an ESC/ESC partial/ESC off switch. When is the TTC activated in the NA car? Is it only when ESC OFF or in partial off mode (and what exactly IS partial ESC?)? After the WHEN is TTC activated is answered, does the TTC in the NA car replace the Traction-control when TTC is activated as in the Euro Abarth? If not, which has precedence?

This is very sophisticated system. Dan Fry, lead Abarth development engineer comes from the ESP department and worked a lot of magic here with the car. I'll have more on this system on the Blog, but here is a (brief) overview

TTC is activated in "partial OFF" and "Off."
"partial Off" allows some more spirited driving but still intercedes when something goes wrong.

TTC is part of the traction control system. Through the use of all the sensors it can recognize if you are driving on a slippery surface or are doing performance driving.

Traction control limits engine power TTC doesn't. Traction Control is off in "partial off"

Q: Internal changes to the engine besides the compression ratio? Are the pistons forged? Changes to the camshaft at all? etc.

The pistons are a lightweight design with low tension piston rings for improved fuel economy. The pistons are made of a high strength silicon aluminium alloy and the piston skirt has a MolyŽ coating. The floating piston pins are held in position by piston mounted circlips. Pistons are cast, which is usual for street driven cars and have the ring lands hard anodized. The regular 500 uses press fit piston pins.

According to the specifications I have, the static camshaft timing is the same. Of course, MultiAir controls the intake operation a good part of the time and that is tailored to the 1.4 L Turbo engine. Valves also look the same size.


Q: Are the brake calipers/pad size larger then stock? Or is it just the rotor size?

Brakes are by Bosch and the rotor is 1 inch larger. Caliper pistons are the same size.

Q: Is the ride height different from the Euro Abarth 500, the Esseesse, or the Esseesse with the Koni kit? If so, how much, and why?

US car is 5mmm higher, and many other changes results in a car that rides better and according to someone who owns the European car, is a better car. More info given in the "Bouncy" question below.


Q: This begs a question Chris. The NA Abarth engine has max 230Nm and the C510 shows 206Nm max input torque. Is the C510 being built for us in Italy stronger? I've never heard of a transmission, stock from the factory, with the input torque already exceeded.

Here is my understanding on these transmission figures I posted way back. The figures are a guideline used when selling the transmission to third parties.

As is common in manufacturing a high performance car, the envelop is pushed to achieve higher levels of performance. However, these figures I published two years ago don't really tell the whole story. It is not a clear cut " apply 1 lbs-ft over this amount something is going to break." The figure is a calculated, and includes a test applying the full stated torque over 100,000 miles. With all the testing and abuse we've seen in Europe and in the US, I wouldn't worry about the transmission. You are not going to shear a crown gear by driving the car hard.

Remember, cars with the ATM trans are running 200 hp, the difference is the auto clutch operation uses controlled engagement and takes the shock out of the gearbox. Probably the biggest factor in all this is how YOU drive your modified car.

Abuse systems and everything is out the window.

Q:Top Gear's review of the Abarth said the ride is 'quite bouncy'. Was the USA suspension modified to be less bouncy?

The US car is not bouncy. The European car spends a good amount of time on its elastomer bump stops. This is possible in Europe, where the roads are generally better. It is not acceptable here in the US, with the roads we have to work with.


Q:Are the back seats leather in a car equipped with leather seating surfaces?

This was a tough question to get an answer. The Fiat exec I tormented with my driving actually put in a call and found that, yes, the back seats are leather.


Q:I've read a couple of times that some guys who have track day'd their 500 with TTC 'on' have overheated their brakes (Pads and Lines/ Fluid) after a few vigorous laps.

I asked about this and they didn't have this experience. I was told the car was tested and met SRT8 brake standards. I find it hard to believe this would happen (at least in the US cars) after just a few vigorous laps. These cars were hammered during 24 hour endurance training at Nelson Ledges, no problem.

Maybe the cars this happened to had old brake fluid and/or aftermarket brake pads?

slowbird
01-04-2014, 04:50 AM
Q:Top Gear's review of the Abarth said the ride is 'quite bouncy'. Was the USA suspension modified to be less bouncy?

The US car is not bouncy.

^^ sconf ^^ I love my Abarth but the ride is exactly how Clarkson describes it. Quite bouncy.

I never realized how crap some of the roads I took to work are until I got my Abarth. Even on my VFR they seem smooth.

Fiat500USA
01-04-2014, 12:22 PM
^^ sconf ^^ I love my Abarth but the ride is exactly how Clarkson describes it. Quite bouncy.

I never realized how crap some of the roads I took to work are until I got my Abarth. Even on my VFR they seem smooth.

Everything is relative based on what you are used to and where you drive. The US Abarth rides better than the Euro car. I've been in cars a lot stiffer riding cars than the US Abarth, however, get on the "right" road with the "right" surface in a car with a tightly damped performance suspension and you'll get that up and down oscillation. In fact, the car rides better than my wifes Wrangler, but there's only so much that can be done with conventional springs and dampers combined with the short wheelbase, weight distribution, etc.

JoeB
01-04-2014, 03:29 PM
Everything is relative based on what you are used to and where you drive. The US Abarth rides better than the Euro car. I've been in cars a lot stiffer riding cars than the US Abarth, however, get on the "right" road with the "right" surface in a car with a tightly damped performance suspension and you'll get that up and down oscillation. In fact, the car rides better than my wifes Wrangler, but there's only so much that can be done with conventional springs and dampers combined with the short wheelbase, weight distribution, etc.

This. I get some "bouncy" on certain surfaces simply based on how short the Abarth wheelbase is, but overall it has a better ride than my previous two cars, an '09 Chevy HHR SS and '06 Civic EX Coupe. Also, I don't think you can compare a car to a singletrack vehicle which can maneuver through the best line in the terrain; especially the Honda VFR, which has a notoriously well-dialed-in balance of handling and ride. Most people who've ridden one say it's one of the best motorcycles ever built.

Crazy Otto
01-04-2014, 03:34 PM
After doing handbrake turns and having fun in the snow yesterday for 10 mins I could not get the car to go into esc completely off mode. Too much craziness I suppose.

Tweak
01-04-2014, 09:31 PM
After doing handbrake turns and having fun in the snow yesterday for 10 mins I could not get the car to go into esc completely off mode. Too much craziness I suppose.

So the quick push partial off and the ten second hold isn't causing it to shut off fully and show the msg across the gauge? Wonder if it is cause the hooning you were doing?

slowbird
01-05-2014, 01:04 AM
This. I get some "bouncy" on certain surfaces simply based on how short the Abarth wheelbase is, but overall it has a better ride than my previous two cars, an '09 Chevy HHR SS and '06 Civic EX Coupe. Also, I don't think you can compare a car to a singletrack vehicle which can maneuver through the best line in the terrain; especially the Honda VFR, which has a notoriously well-dialed-in balance of handling and ride. Most people who've ridden one say it's one of the best motorcycles ever built.

Don't get me wrong, I love my Abarth, but I can't help but think "man this thing is bouncy" on my way to work. But I can tell it's a sporty/firm suspension bouncy, and not the cheap suspension bouncy I get in my wifes Toyota Yaris.

I only bring up my VFR in the sense that it has a fairly firm suspension compared to the other vehicles I have owned/driven. There are a few roads I have ridden on my VFR that have shaken my teeth out but in a car are buttery smooth.
...and yes she is a great bike, thank you :-D

slowbird
01-05-2014, 01:05 AM
So the quick push partial off and the ten second hold isn't causing it to shut off fully and show the msg across the gauge? Wonder if it is cause the hooning you were doing?

Does the car have to be stopped in order to activate the full ESC off mode?

Tweak
01-05-2014, 01:33 AM
Does the car have to be stopped in order to activate the full ESC off mode?

According to the owners manual it is not required, it does not state anything but press and hold for 5 seconds (feels longer) for full off mode and a normal press for partial off mode, so either stopped or moving shouldn't be a problem or FIAT forgot to add that information.

jguerdat
01-05-2014, 08:33 AM
I've had a few times that I simply couldn't get even partial ESC to happen. No light regardless of whether I pushed the button briefly or held it in. Didn't matter whether moving or stopped. Key off/on fixed it but I can't explain why it happened.

Crazy Otto
01-05-2014, 09:47 AM
It was fine afterwards.......i get glitches with this car. Bit more than i like but i will grin and bear it.

ophidia31
01-05-2014, 11:51 AM
This cars bouncy? I think it rides like a cadiallac. sillylol Then again, my last car was 90% suspension/chassis work setup for a track and hard as a rock. lol

catman2130093
04-02-2014, 01:43 AM
I have driven my 07 Honda Element SC 74k miles-and my little Abarth is a MUCH nicer ride-even in Sport mode. However,the Element's steering is positively the best-very quick and direct with good feel. Still,the Abarth is the most comfortable,even in Sport. Try the SC on concrete freeway expansion joints-misery...

doverosx
10-24-2014, 08:44 AM
Compared to my old Nissan Sentra SE-R Spec-V the Abarth rides like a dream. Even when the road undulations start "matching" the length of the car and my head is being whipped back and forth, it isn't as bad as the Spec-V.