2.0 vs 1800 question

[BEEK]

if i was going to built the cheapest performance motor i could i would use a 2.0 efi engine to start.
i would use high compression pistons, that would be my only budget buster so to speak. but that is the best way. the 2000 efi head has better flow than a 1800 head, the valves are less shrouded. i would use a 1800 intake and a 34dmsa, from a 74 spider/coupe. i would use a twin downpipe exhaust manifold or headers.

the 1608 head, i have seen 2 configurations, 1 was factory ported (cleaned up very well, all the intake ports were worked) i have seen many on unmolested engines, so i know they exist. the other is a as cast unit. the front water jacket on the 1608 head has to be welded to a smaller area so it wont leak on the bigger bore. but thats it. i know someone has the cc figures of all the combustion chamber sizes, so i will defer to them on the actual size, but from what i recall it is smaller than the 1800, which is smaller than the 2000.

also you could play with cam timing too with adjustable pulleys, even with the stock cams you might find a better setting.
the next place i would spend money is camshafts. but choose wisely as all are not created the same, its the area under the curve that you should be concerned with, not total lift or actual timing numbers. but how long the valve stays open and to what extent it is open before and after the tdc event.

[fiatfactory]

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[So Cal Mark]

I'd really like to hear an explanation of how the O2 sensor adjusts for altitude, atmospheric conditions and air density

[MrJD]

the O2 sensor adjusts the fueling to account for varying atmospheric conditions and things like altitude. (which affects the air density)

Does it now?

Rather than eurospec cars using the same ECU as US spec cars... i think its more like US spec cars ARE euro spec cars which were de-tuned and had smog equipment installed to be capable of passing new US laws. They took a Eruo car, and did the required things to make it legal in the US... to the detriment of performance.

Now, I am not sure that US ecu's and Euro ecu's are identical... if that is true, then GREAT! That means you can use the better Euro spec parts and not have to worry as much about the ECU.

Now, the O2 sensor: Yes, it will act to modulate the amount of fuel metered out to the engine, but stock ECU's are NOTORIOUS for being relatively rich in their fuel output... because we all know what happens to engines when they run lean (and no factory wants to be responsible for replacing thousands of warranty engines). That being said, running rich means you are not making full power. Also, I'd predict the stock O2 sensor is not terribly accurate, and is CERTAINLY not a wideband modern unit. ECU's of the 70's are archaic compared to modern systems. Archaic in that they likely are VERY inaccurate with the fuel they put out, and are likely Very rich.

If you want to heavily mod an engine (that means internals during a re-build) and you want FI... suck it up and pay the extra money for an appropriate stand alone system with an appropriate wideband 02 system to analyze it. If you're pretty good at what you do, you can likely get out for around $1k for a complete standalone system with 02 monitoring. (see megasquirt ecu and innovate 02)

I'll make this statement: no carb set up known to man will ever be capable of making as much power as a well-set up ITB FI system... But getting a well-set up ITB FI system is a PITA, lol.

Not as sexy as carbs either... but still pretty darn sexy! INSTANT THROTTLE RESPONSE!
http://youtu.be/CRGtUa03knM

[fiatfactory]

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[timinator]

the AFM only measures the volume of air... it doesn't know how dense it is..

The afm measures temperature also. If you know the volume and you know the temperature you can find the mass.

The O2 sensor modifier circuit in the L-Jetronic system is disabled by the throttle position sensor after so many degrees of movement. Narrow band O2 sensors can only detect if the mixture is richer or leaner than stoichiometric but can not tell by how much. They can not aid the ecu in determining the exact amount of change neccesary to injector pulse. As with many early injection systems if the O2 does not work the engine runs better.

In an engine the VE determines the volume inhaled, the pressure is constant, if the temperature rises then the density decreases.

In an engine the volume of air entering the cylinder varies with rpm, as does the pressure and temperature. The combination of these physical components determines the VE at each specific instant the engine is running. Peak torque is the point of highest VE. Add to this that each cylinder does not make the same power as the other cylinders at any specific time. Each cylinder swinging back and forth between rich and lean, higher and lower % of efficiency of combustion without regard to the other cylinders. The density changes for many reasons including compressability because it is a dynamic system.

I thought you would have known all this???

I like the three question marks. Very nice touch.

[BEEK]

back when i worked as a line mechanic at the fiat dealership in the early 80's o2 sensors were on perpetual back order an fiat sent a tsb that said to cut the wire from the old o2 sensor and take it out of the loop, as a bad o2 sensor hurt performance where not having one actually helped

[MrJD]

back when i worked as a line mechanic at the fiat dealership in the early 80's o2 sensors were on perpetual back order an fiat sent a tsb that said to cut the wire from the old o2 sensor and take it out of the loop, as a bad o2 sensor hurt performance where not having one actually helped

Lol. Thats excellent! Gotta love early computer based equipment.

[rebar1111]

1. Weren't the altitude correction on the US ECU's added after 1981?
2. Can't the static compression ratio be increased by using a thin soft metal gasket like we did in the '50's? And therefor save the cost of pistons? Or even milling the head (as in making them flat)?

[BEEK]

altitude compensation, other than plugging in a connector under the dash for high altitudes was not until 83 they put a barometric sensor.

shaving the head and a thinner head gasket wont gain you much with this engine

[RRoller123]

That is a good question. Could you safely take a little off the head to raise the CR? How much off to get what CR? This is an interesting solution and would be quite cost effective if it works?

[So Cal Mark]

as you shave the head you start changing the cam timing, making adjustable cam sprockets a necessity

[RRoller123]

I could install 'em, but I would have no idea how to adjust 'em.

[vandor]

That is a good question. Could you safely take a little off the head to raise the CR?

You need to shave the block, not the head. There is very little material in the head before you get into the intake valve seats. When you shave the block you get more CR increase for shaving the same 'height', as the piston bore has more area than the combustion chamber.
Very roughly removing 1mm from the block will give you a one point increase in CR (ex, goes from 8:1 to 9:1).
This will also cause approx one degree change in cam timing on each gear, not worth worrying about IMO, as with the stock camgears one is lucky to get within 2-3 degrees of spec.
The limiting factor is the piston will stick out of the bore and it needs .030-.040" clearance to the head when at TDC.

[Thunberg]

....the next place i would spend money is camshafts. but choose wisely as all are not created the same, its the area under the curve that you should be concerned with, not total lift or actual timing numbers. but how long the valve stays open and to what extent it is open before and after the tdc event.

Hi wonder which camshafts I should go for?
I have a 1995 original Argenta engine ie but now with 40idf, cam drive distributor and Fiats 4-2-1 system, Fiat original camshafts: 15/55 57/13 and 9,5mm lift (Argenta)
Fiat original head no 5991740 (Argenta), 43.5mm intake valve .
I use the car mostly at 2000-3500 rpm and driving on small twisty roads. Do you have any suggestions?