single point injection

[swede]

Is there anyone here in the forum that has tried to convert a carburetor spider into SPI (single point injection)?
I’m actually thinking of trying this instead of buying a new carburetor.

I know other Fiat models that have SPI installed from factory (Regatta 100Si.e., 90Si.e. och Tipo DGT).
The Regatta use a 1600cc TC motor so I guess it should be easy to use all those parts on my 1800cc TC.

I’m not trying to make the car go faster just better idling and overall performance, I’m guessing that it also would be better MPG since it will be more exact with the fuel mix.

All input regarding this would be helpful.

[Fiat1980spyder]

Why not L-Jet injection off a spider 80+, or go to http://www.turbo124.com and ask around to see if one of those guys have the injection those guys are using megasquirt for there Fuel injection needs no longer need L-jet.

[BrianAz]

Hej på Dig Swede !
I used to work for Delphi Automotive who developed single point injection in the 80s and their unit is on one of the Fiats, I believe it is the 1.6L Regatta.
As you correctly point out single point injection gives a better air fuel ratio control than carburettors which improves the efficiency of the catalytic converter and hence lowers emissions. Unfortunately, that is about the only good news about single point injection.
One of the difficulties in developing single point injection was getting equal fuel distribution from the injector to all four cylinders. The injector sprays over the throttle valve and then hopefully in equal amounts to all four cylinders. A carburettor does the same thing but the SPI was very sensitive to things like manifold design. So, if you build an SPI system on your engine and deviate from the production SPI set up then you are in unknown territory regarding fuel distribution.

The same applies to idle control. this is achieved by a stepper motor integrated in the SPI throttle body, which is optimized for the engine's idle air flow. This is affected by things like engine size, engine loads (AC, electrical) and exhaust design (affecting backpressure). If you get a good idle with an SPI system, great. If not, you have no means to do anything about it as this would necessitate changing the idle control parameters in the ECU.

You will not get any more power by fitting an SPI. Both the SPI and the carburettor have the ability to deliver adequate amounts of fuel but what you need is more air into the engine which you can achieve by either fitting a multipoint injection system or twin Webers.

As with an SPI system fitting a Multi Point Fuel Injection system (from an 80s Spider for example) involves increasing the fuel pressure, rigging up a fuel return to the tank, controlling the fuel pump on/off, fitting the airmeter (multipoint) or MAP sensor (SPI) not to mention the associated wiring and getting an engine speed signal into the SPI or MPFI ECU.

Conclusion: You have 2 options:
1. Fit an MPFI system. You will get more power for the same effort and cost as fitting a Single Point Injection system.
2. Fit twin Webers, and a cool looking exhaust system from Allision Automotive, Yeah.

Lycka till,
Brian

[swede]

Wow thanks for the very good answer, guess the decision will be option 1 and actually convert into MPFI system.
Tack för hjälpen

[pedrofromspain]

Brian,

i noted your reply to the Fiat SPI.

The Regata 100 IEs Weekend i have just bought does not run that well, SPI just has no top end power and the car is generally gutless.

At present i can't get a Idle Air Valve for it so i have converted it to carb, mainly as it ran so badly .

*Now that the throttle position sensor and idle valve are disconnected what effect does this have on the ECU and the ignition?
I suspect the ignition is not advancing ??

What are my options if i go the carb way, do i need to convert to a points or different distributor?

These IE cars are very rare in Australia, i have two and neither ran well.

Any ideas?

regards
Cas

[lanciahf]

Robert I would not do it. You will take the "Fiatness" out of the car, might as well buy a Toyota. How about a new 32/36 DFEV? Small carb base like your DMS and same air cleaner top.

[swede]

Robert I would not do it. You will take the "Fiatness" out of the car, might as well buy a Toyota. How about a new 32/36 DFEV? Small carb base like your DMS and same air cleaner top.

Your absolutely right and it won’t happened it was just a taut I had, I might still be converted to FI but not right now so might get back to you on those FI parts again.

[pedrofromspain]

Previously mentioned by Brian is the lack of idle control.

Erratic idle is this ever caused by a malfunction of the ECU?
Might change the ECU.

Despite a new IAC valve/stepper valve , MAP sensor changed and what appears to be a new O2 sensor , the idle and fuel consumption are not right.

Car has done 180,000 klms and i wonder if common malfunction on high klm ?

[BrianAz]

Naaaa,
Erratic idle is most likely NOT caused by a faulty ECU. The operation of ECUs is a bit like their construction: digital electronics, meaning that they either work or they don't work, no in betweens.
Is the vacuum advance on the ignition distributor working OK ?? This could be the reason for both high idle (air leak in the manifold if the vacuum advance tube is leaking or has fallen off) and high fuel consumption (no vacuum advance giving very low ignition values at part throttle).

Brian.

[pedrofromspain]

Brian,

it turned out there was a vacuum leak , which i fixed the car then ran great, then just stopped one morning in the driveway.

I found the SPI was not fueling then engine in any way, not a trace of life.
Pump primed itself ,but no fuel to run the car.

I replaced in sequence with working parts from a spare car,
SPI
coil
computer
ECU
distributor
relays
sensors
Checked wiring
injector wiring active
bridged pump to work all the time , did nothing


this one has really got me stumped!

i then fitted a regatta carb and the car runs fine.
Adjusted advance then r/r spi and the car would not start.

Oddly could not start the car with aero-start at any point.

I am now running the car with the with the carb.

Any ideas?

I am thinking of a Strada distributor with a vacuum advance or points??

Any suggestions?

Pedro

[124JOE]

a carb system runs on a 3lbs pressure
a FI system runs on a 35lbs pressure
it seems you have said anything about that so i hope this helps

[pedrofromspain]

'a FI system runs on a 35lbs pressure
it seems you have said anything about that so i hope this helps"

yep,dealt with thaton a test/temporary basis .T-pieces to return to tank.
I never said any of this was straight-forward.
To convert properly you need a different tank unit and a low pressure electric pump.
85S/100S carb type.
Electric pump needs a different tank fuel pick-up.


You know anything about the relationship between the ECU and the lack of digi-plex box?

[BrianAz]

Hi Pedro,
Very strange. It sounds electrical but you have changed almost everything on that side.
Did you have a spark at the plugs when it stopped and after you changed everything. I guess so if it runs OK on the carb. How about the fuel filter? Does the pump run OK all the time?
Did you try draining the fuel and refilling. Again probably no point if it runs with the carb.
Do you change fuel pumps when you change between the carb and the SPI?? Fuel pressure
Any way of checking whether the SPI injectors are still opening when voltage is applied to them ?

Good Luck,
Don't give up,
Brian.