Abarth 130 TC engine hesitation in right hand curves.

[Abarthnorway - Remi L]

Hi All!


Currently putting together a 130 TC engine (for the second time after reading Guys new Bible) destined for racing.
It will use the standard Solex 40 C ADDHE carbs as fitted originally.

The engine is transverse mounted and the carbs are facing forward with a 5`upward tilt

A known problem with this engine is a very clear sudden hesitation after long right curves - not ideal on clockwise tracks.....
The same issue is present even for cars fitted with Weber DCOE`s. After fitment of Dellorto 45 this issue disappeared on mine.

I have not investigated the issue yet, but I will have to look into it.
If anyone has some ideas or experience please share Your knowledge.

Thanks in advance!!


Remi Lovhoiden





130 TC engine with original Solex carbs

[Guy Croft]

NEVER HEARD OF THAT!!

I figure I would definitely have seen it in NHRA on long circuit if such a problem ever existed with 45 and 48 DCOE.

Could certainly be a problem with float needle and fuel pump though...

G

[Abarthnorway - Remi L]

Hi!


As far as my memory serves me all standard Abarths I have known have had this hesitation. It only appears after LONG rights while using the throttle.
I have good contact with a friend that runs my previously owned Abarth on the third year in this racing series, and he still suffers hesitation when giving full throtttle after long right turns.
The fuel pump is new uprated, the car has a fuel cell, and the carbs were overhauled and set up by me just before he bought the car - so those parts can be ruled out.

I am wondering if this can be related to the transverse configuration maybe combined with the carbs upward tilt. The float chambers look like this in the pictures underneath:




Solex float bowl.




Basic drawing:

Black: Floats
Green: Needle valve location
Red: Fuel flow in float chamber during right hand turns

My theory is that the flow of fuel to one side causes the floats to rise enough to close the needle valve in right turns. After powering through a long curve the fuel gets so low in the bowl that it makes the engine hesitate for a second until the bowl fills up again.....

Can probably be caused by incorrect procedure while adjustmeting the float hight .... they are quite flimsy....... the needle valve might close at the right point when standing still, but it the floats themselves are in some way tilted wrong it might not work out correctly during racing. Makes me wonder if I have ever seen an untouched horisontal Solex carb??

Might be completely wrong though - will try to solve when the car is up and running = later. Its easier to fix with the car on the road and when the temperature is not - 18`c outside.


Best regards

Remi Lovhoiden

[Nobby]

Is it hesitation due to no fuel or too much?. Perhaps the floats are being forced to stick up/down due to the amounts of g-force, or the fuel is sloshing up one side in the chamber.

Does the 5deg slant of the inlet/carb mean the float pivot can go higher than horizontal?

[Guy Croft]

all sidedraft carbs will tolerate 5 deg tilt as a matter of routine, FWIW,

G

[Abarthnorway - Remi L]

Is it hesitation due to no fuel or too much?.

Hi!


If my theory has anything in it, the hesitation comes from the fuel level being to low - which means a too lean mixture.

The tilting on the carbs could be a factor as well, as the two floats maybe should be adjusted individually to be horisontal - floating equally deep in the fuel. No idea. If Guy says it tolerates 5 deg - it does.

I am just speculating at the moment - just started thinking about this issue.


Best regards

Remi Lovhoiden

[Abarthnorway - Remi L]

NEVER HEARD OF THAT!!

.......I figure I would definitely have seen it in NHRA on long circuit if such a problem ever existed with 45 and 48 DCOE......

Hi Guy!

I have never used 45/48 Weber myself - only Weber 40s as fitted to the Abarth. With the Dell 45 the hesitation disappeared (With Facet Pump).

Could it be as simple as a slightly too small needle valve on original carb?? I do not remeber the size at the moment....


Best regards

Remi Lovhoiden

[Guy Croft]

No idea, Remi.

You will need wide-band Lambda and data-logging to determine what is really happening.

I've heard of so many probs with the 130TC ignition I would not even use it. Could be that..

G

[Abarthnorway - Remi L]

Hi Guy!


I have driven more than 100.000 miles with 6 different standard Abarths with no problems with the ignition whatsoever.

I am not saying that the ignition is any good, but has never caused me any problems personally..... and cannot see why its related to hard right hand curves misbehavior......

The - among Abarth owners - well known 130 TC problem with hesitation on hard right turns, must in my mind be located somewhere else than the ignition. At the moment I cannot say where or why - I am just trying in my own way to find some more definitive answers - and I am starting from scratch with no hard facts.


Best regards

Remi Lovhoiden

[Guy Croft]

essentially what I'm 'driving at' Remi is the corners and the misfire may be a coincidence of some other problem and not actually fuel related.

G

[roseglen]

As a Strada Abarth 130tc owner since 1994, I have one other idea/thought that you should also put into your minds, Body roll (not that I am saying it rolls badly) but on a long corner you can bring the rear inside wheel off the ground and the change in pitch and tilt may also be a factor. This problem has never happened on my car though!

This problem can happen on a badly set up or very old X1/9 'carb, on very keen cornering. A rebuild and resetting of the float so both halfs are level and needle heights spot on will fix this - full 'carb strip, clean and rebuild recomended tho- This resetting can take time to get spot on.

I have helped many people with this problem in my role as a Fiat X19 Owners Club technical officer.


Oliver

[Abarthnorway - Remi L]

Hi All!


Thank You for Your response.

Will hopefully find a solution this summer - I will at least do my best to set up the carbs as well as I possibly can, and take it from there.

Would be very nice to find a solution to this, both for me and my already Abarthracing friend.

HAPPY XMAS!!


Best regards

Remi Lovhoiden

[Abarthnorway - Remi L]

Hi Guy & All!


I have changed the heading of this thread - as the response from Guy seems to rule out carb issues - and I cannot be sure that the carbs are to blame.

I have been wondering about another important fluid - the oil and oil pan.

The phenomenom only occurs on very long and hard right hand curves of several seconds. If we suppose a continuous G-force of well - lets say 0.9g the oil will probably have enough time and force to climb over the baffles and hit the rotating crank. I have never experienced it on left turns, and on right turns only during racing, and on the road only on a specific long sweeping 270` turn. I suppose it might happen on left turns as well, but the tracks I have used are clockwise with longer right hand curves.

The problem also disappeared with the fitment of a tuned engine (Dellorto 45, fuel pump and Alquati aluminium sump with slightly bigger baffles)

Still just speculating - and as always comments very welcome.




This is the 125 aluminium version - 130 TC almost equal but with the addition of an extra horisontal baffle at the left side of the pan.


Best regards

Remi Lovhoiden

[Nobby]

Is there any sign that the oil is foaming up at all (i.e being churned up by the crank) with possible oil pressure loss too?

[Guy Croft]

Windage is certainly in itself not probable cause if that is what you are thinking about.

But you would certainly get power loss if there was sustained and chronic oil starvation - the crank would go tight.

G