Fiat Seicento 1.1 VAN - budget tuning

[Abarthnorway - Remi L]

Remi Lovhoiden
Marbella
Spain


Hi all!

I am not sure weather to post this in "readers cars" or here, but as I will need some expertise and input from members of the forum, I have decided to put it here. This project is purely hobby based - may never produce any useful results - the timetable is not set - so do not get Your expectations too high!!

I have now - at the age of 36 - finally done my first good car deal.....You are allowed to get a good laugh.

A Seicento 2002 1.1 VAN with 68.000 km was bought 14 days ago for the price of a night on the town.
My only intentions was to get the most economical and practical small errands car for the lowest possible price.....but shockingly this minicar inhibit the "magic fun factor" usually not found in modern cars. Feels like I am connected physically to the road with it.....and with the current setup it feels thrillingly scary;-) I haven`t had this much fun in a small car since driving around in an Autobianchi a112 Abarth some years back. Seems like I have forgotten how much fun 54 hp, 155/13 tires and ground clearance like an SUV can be. The thrill of driving is not directly connected to HP, low profile tires, spaceship cockpit and on board entertainment.....

The car is bought for company purposes, and is as such subject to a strict degree of economic limitations..... but this car has such a "fun potential" that it would be a real shame not to exploit the possibilities for improvements.

A few pictures of the Monster:














"The Project":


Goal: Getting the most reliable, flexible and powerful engine within a certain budget and limits, while learning a few new things in the process.

Limitations: Retain the seic 1108 block. All mods DIY except machining. Fuel injected engine (no carbs). Car must be (reasonably) road legal after mods.

Budget: 800 Eur incl induction and exhaust modification. Tools and freight on parts not included in budget.

Measurement of modifications:
As rolling road testing is cost prohibitive, I will find a suitable stretch of uphill road and register the time for accelerating from - f.ex. - 50 km/h to 130 km/h in third gear after each of the mods....always full tank - empty car. This is - I hope - a useful strategy to check out the real world effects of engine modifications...


I am sourcing information regarding the engine and management system, and some basic info is found already:

1108cc (70 mm bore x 72mm stroke)
SOHC 8 valves
54bhp @ 5,500rpm
88Nm @ 2,750rpm
Compression 9,6:1
Valve sizes: Inlet 30.2 - 30.5mm Exhaust 27.2 - 27.5mm
Cam figures:
Inlet: 7-35 Exhaust: 37-5 leading to a duration of 222` duration, timing inlet 104` exhaust 106` (running clearance not known)
Lift 8mm (supposedly cam lift = 0 clearance)

Engine management and fuel:
Multi point injection
32mm throttle body
Rev limiter kicks in at 7000 rpm ..... (but You`ll struggle to get there:-)


Please correct me if data is wrong.


Will keep You informed as I get some progress.


Best regards

Remi Lovhoiden

[Guy Croft]

It's got to be gasflow, valve seat mods and raise the injection pressure a few psi?

G

[Abarthnorway - Remi L]

Hi All!

Mr Croft...... Your suggestions really come as a shock to me!! ;-)

....... Because after trawling some forums regarding this car, the most popular and used mods seem to be:

- Induction kits
- Replacing the throttle body with a larger one


So I took off the airbox today to check out a few things:




Hose going from front chassis rail




90 Degree turn ..... no good


The air intake hose
going to the airbox, has a few curves and "dents", and it has an internal diameter of 40 mm. It is connected to the front chassis rail(???) unsure of the correct term) and draws air from the the front corner of the engine bay through a rather obstructive path. So its the hose in the picture + 50 more centimeters of twists and turns before the airbox.....hmm

I will try to replace this hose to create a straighter and shorter way into the airbox from behind the grill, just in case - won`t hurt.... but I really don`t think it will make any big difference though. To make sure the new hose will recieve fresh air, I removed some "makeup" on the front bumper to let the air flow into the engine bay:




My 2 Year old son giving a helping hand ..... (by throwing some of my tools into a sewerhole closeby...)




The standard bumper.....




Part taken off




New bumper modified for later fitment of new cold air intake.....



The airbox itself
is huge, and has a round filter that has a circumsicion of approx 70 cm, and its height is effectivly a bit more than 4 cm with the top cover on: That means a filter area ca 300 cm2. The entry section from the air intake hose is 45 mm and the shape looks ok to me.




Filter.....




Inside of filter box....




Air entry section into airbox...


As a comparison of entry sections and filter area - The Ritmo 130 TC Abarth with its 2 liter 130 hp engine has an entry hole into its airbox of ca. 40mm, and a filtration area of approx 300 cm2 as well. That means that both standard air entry section and filter has more than enough potential for this engine. Will be kept bog standard.




130 TC filter element




130 tc Airbox


The throttle body size is 32 mm.
I am really not sure what to think about going bigger..... first of all this car has a throttle positioning sensor that feeds the ECU that again control the fuelling. If enlarging the throttle to 40mm or bigger as many do, I do suspect that this will upset the fuelling somewhat. At a throttle angle of lets say 30` - the 40mm throttle will flow at least 50% more air than the 32 mm one (40x40 / 32x32 = 1,56).... I am afraid that the the increased flow at part throttle will lead to a lean mixture especially under light throttle cruising. I don`t want the throttle to be a bottleneck for flow, but how much does the throttle need to flow?? I am not sure??



Throttle....


For comparison:
The 124 1800 (118 hp) has 25 and 26 venturies in its largest available carb - the 34 adf - often reffered to as an performance option on bigger Fiat twin cams. Those two combined represents an area of 1022mm2. The 32 mm throttle in the Seicento represents an area of 803 mm2 ...... True enough the throttle shaft takes up quite some space so lets take away say 5mm x 32 mm lenght = 160. That gives an area 643 mm2.....

Some more calculator fun....
643 mm2/1022 mm2 x 1756cc (124 1800) = 1104 cc ....... pretty close to Seicento 1108 or what??
643/1022 x 118hp (124 1800) = 74 hp...... some way to go then:-)

Anyway - to minimise flow loss the throttle shaft will have to be slimmed down - increasing the throttle opening and improving aerodynamic shape. The opening from airbox towards the throttle is not the worst around, but maybe some kind of ram pipe could better it. The clearance towards the top of the airbox is sufficent.... About 9 cm, so I will check what I can get hold of.

I have decided to keep the throttle body size standard at least for now....and a with an optimised throttle shaft, it will be much better than the production item. At least it is capable of a nice powerhike, if the venturi area of the 124 is comparable to the Seicento throttle size..... Would gladly install a slightly larger one of 36 mm, but I am really afraid of the effect on the fuelling.

So for now, no plans for an induction kit or oversized throttlebody - very good!!
Then I can spend 800 Eur on other things!

I have been searching for a suitable road for testing, but no luck yet - Too far away, too much curves, highway too long between exits or too much traffic / intersections. Will go for a sunday cruise tomorrow..... and maybe perform some testing:-)

More to come!!!


Best regards

Remi Lovhoiden

[miro-1980]

Remi,

No offense but :

I am surprised you were surprised by Guys' suggestions!

I am certainly not!

I would do exactly as Guy suggests and forget the rest. You would be surprised by the result.

I would say that no real meaningful performance modifications can be achieved under project limitations you defined and at this budget and what Guy suggested would give you the "most bang for the buck.

The suggestions you found elsewhere are - pardon the expression" - "weekend mechanic's tips" rather serious approach at power improvement.

You cannot simply apply few sports modifications and expect to achieve anything significant. Air flow feed into filter maybe the important , but fist you need to do the basics.

The rule is that power is on the head, so unless you do something long this line this may actually be more cost than effect (and a bit of risk you might destroy the engine or end up with less power and torque than you have now.

It looks like what you are after is not engine modification but air flow to carburetor enhancement. I believe you can do it at practically no cost (100 Euro max) - just open it up. What you did so far is very much on track. I would clean the air and fuel system, replace filters, get the car tuned properly , pour Motul Racing oil, use Shell Racing 100 octane fuel and have fun. This way will cost you practically nothing and you take no risk off messing the engine up. If you have spare cash get a stiffer and lower suspension and buy yourself nice larger wheels and good "sporty tires" This would be my advise. Total cost would be close enough to 800 Euro you plan to spend. I would do nothing more. A assure you this can give you all the fun you can buy for 800 Euro, and really you will enjoy this car Seicento. I also love driving a Seicento , whenever I have a chance

And by the way remember that flow improvement will mean increased fuel consumption. I know guys that have a lot of fun on Seicento but fuel consumption in excess of 10l/100km. Performance improvement always come at cost of fuel consumption.


Miro

Sorry for my frankness but I would also suggest a less scientific (and more trial and error) approach to air flow. Air flow is one of the fundamental elements of any performance aimed modification. Unfortunately this is far, FAR more complex than your limited approach and calculations would suggest.

[Abarthnorway - Remi L]

Hi Miro!

Remi,

No offense but :

I am surprised you were surprised by Guys' suggestions!

I am certainly not!

........;-).........

Well - I`m sorry I was a bit unclear - expressing shock over Guys suggestions was meant as an irony.....

Thanks otherwise for the input regarding the way forward, all comments and experience welcome:-)

Regarding the planned power modifications, I will decide which way to take when I inspect the various parts of the engine and auxillaries. I will also try my best to explain why I made or didn`t make the mods.... and as a true hobby mechanic I expect to make at least a handful of choices and calculations of questionable quality and reason. As a matter of fact discussions regarding my calculations and changes are the reason I am posting it on the forum + register and post road test results after each mod. Do not expect rapid progress though, this will take time as I am very busy with my professional life as well.

The 800 Eur is for the engine and auxillaries alone.
Suspension, brakes, bushes, wheels, tires etc have their own budget, but to keep the thread focused on the engine aspect, I will not post it on the forum except for when it might affect the performance recorded on road - like f.ex a change in tiresize.

Best regards

Remi Lovhoiden

[Abarthnorway - Remi L]

Hi all!

I have just found a decent uphill testing ground for the Seicento for acceleration testing.
The margin for error is quite huge, so I consider the testing results as approximate......

Biggest problems are:

to have the right start speed
at the right point,
read off the exact top speed
stop watch at that moment

The test is in third gear starting from 50km/h and ending at 120 km/h
At 50 the engine has ca 2450 rpm and at 120 ca 5870 rpm

Condition of Car:
100 % standard
Not serviced
No Mods

Outside temperature 15`c

Run 1: 45.3 seconds
Run 2: 43.1 s
Run 3 : 44.7 s
Average : 44.4 seconds

Result Test 1: 44.4 sec


Best regards

Remi Lovhoiden