75 Twinspark lacks torque/driveability compared to single-spark Nord?

[Evan Bottcher]

After some opinions, not sure if I'll find any around here but I'll try anyway...

We've got a 75 TS, and I've driven a couple of others.  Comparing it to the various 105 and Alfetta single spark cars I've driven it's entertaining but feels like it lacks torque down low.  It gets up and moves at high revs, but is almost bloody dangerous below 3000rpm.  Second gear seems very long, and around a tight corner on a suburban street or over a speed hump the car won't pull away in second in any kind of hurry.

I just wonder if it's the 75 chassis/gearing/something, as people rave about these engines transplanted into 105s.

Enlighten me.

thanks,
Evan.

[Darryl]

This should be interesting - you actually *asked* for opinions....

1) Sub 3000 rpm isn't so bad in TS in broad terms - flexible/tractable compared to most modern injected stuff I've driven.
2) A bank of sidedrafts with accelerator pumps does certainly seem to give a more instant "kick" from idle compared to opening a throttle and waiting for a flapper and an 8051 (or whatever fossil is in a motronic) to notice.... The seat of the pants dyno/dragstrip says the carbs are better but after that initial kick I'm fairly sure they lose out to the TS/motronic....
3) I think it is probably true (depending on what it is running - but at least assuming stock cams and carbs) that the carb single spark engine is more happy to just cog along at very low rpm. This could/should bperhaps be expected as the TS cam would be considered fairly "wild" if an equivalent duration were installed in the older engine, which was definitely tuned for low-midrange torque. There is only so much cam timing variator can do.
4) I'm also guessing you could add some fuel at low rpm, highish load on TS and get more of a visceral acceleration at least - but emissions / cat might not like it much...
5) TS gearing is better than alfetta because 2/3/4/5 are closeish/well spaced. You aren't going fast enough

[GTVeloce]

My TS pulled 200nm on the dyno but as Evan saids, it feels a little sluggish sometimes below 2500rpm. However, remove the fuel quality plug completely and it improves dramatically. Sadly it doesn't idle as well without the plug and with the A/C on it stalls from time to time so the fuel quality plug stays in. Have you tried removing it and run the car for a while?

[aggie57]

I have to agree with your basic premise Evan.  The ones I have driven do feel flat down low compared with a classic nord on carbs, including my fathers one which he had for several years.  Probably a combination of things but you should try a 164 twin spark for sluggishness.  Dad replaced his 75 twin spark with one of those and sometimes it seriously struggled to get up hills.  Thankfully we didnt get them in Australia!

[Darryl]

However, remove the fuel quality plug completely and it improves dramatically. Sadly it doesn't idle as well without the plug and with the A/C on it stalls from time to time so the fuel quality plug stays in. Have you tried removing it and run the car for a while?

Ah - my aircon doesn't work - fuel plug is out. Should have thought of that in my point 4... (and it throws in some more advance too).

[Evan Bottcher]

I pulled out the fuel quality plug this arvo and did my normal longish drive home, my butt dyno says it does actually improve things below 3000rpm.  Once warmed up the idle seems quite high (over 1000rpm).  I've had that intermittently in the past so it might be unrelated.

I'm sure I've tried removing the fuel quality plug previously and not noticed such a difference, perhaps I'm being optimistic.

[DaveB]

Suprised that no-one has mentioned the airflow meter (AFM).

The top of the AFM prys off fairly easily after 20 years.
Carefully clean the electronic wiper contact with metho cotton bud & make sure the flap pivots freely.
The electric contact may be worn or scored. If you feel confident, carefully adjust the wiper arm to an unused radius next to the score mark.

Tape the top back down while testing, then a few spots of silicone to glue it into plave when you're happy.
A word of warning tho, don't go wildly poking down the AFM throat.  There's a delicate wire sensor behind the flap.

Everything you need to clean and lube is under the big square cover on top.
No need to remove AFM from engine - unless you have another to test -

Changing the AFM really changes the character of the car.
A Twinspark should have heaps of power, mine does, compared to the 2L '74 105 GTV & Berlina we had.

Just my 2c
Dave

PS, I have read that removing the center muffler gives a big flat-spot about 3K rpm.

[festy]

There's certainly room for improvement in the TS tune.
Here's a pic of one of the part-throttle ignition maps, you can see the compromise made for emissions immediately.

(don't panic about the 40* advance at low load, this map isn't used at that load range)
At WOT they lean out the fuel and reduce spark advance around 1600-2k rpm, again for emissions purposes I assume.
But is your VVT working properly? It should kick in at about 1280rpm at moderate engine load, if it's a dog below 3k maybe there's a problem?

Edit: forgot to mention - if you want to try tweaking the fuel and spark (or just about anything else), I can chip these ECUs.
Because they have 4 unique map sets inside, you can keep one standard and have 3 levels of modified tune to swap between so you can try different things out.

[AikenDrum105]

It's interesting how much difference in low end performance a tiny change in spark advance can make.

  In my TSified Super with DCOEs and one of those MarelliPlex jobs running single plugs (until I get my ECU setup)    - if I set advance up correctly at idle,  I get great low end, but significant detonation on partial throttle in the 2k-3.5k area with the VVT engaged.

Obviously the Marelli curve is too aggressive for this application -   If I retard the timing about 2-3 degrees to calm the detonation down - the car significantly bogs under load down low.

Been following Festy's Motronic degustation thread on the Alfabb - really interesting stuff.    here: http://www.alfabb.com/bb/forums/engine-management/190352-what-stock-75-ts-motronic-can-cannot-do-15.html#post1112177

Cheers,

[MD]

Something odd there Evan. The TS engine develops maximum torque @ 3000 rpm and I suspect the first thing to check is whether the variator is actually working-both the solenoid and the cam device.

[Mat Francis]

G'day Evan,

When I first got my TS i felt exactly the same. Took me a bit to find, but here is my first impressions from when I got it.
http://www.alfaclubvic.org.au/forum/index.php?topic=2740.0

If I were to guess again now, I'd say that it's the extra weight of the 75 that made if feel sluggish. With all the running gear in the alfetta now (when it ran anyway), it is definitely quicker from down low than the healthy Nord engine was.

[BradGTV]

people say that the twinspark produces more power (quoted from facotry aswell)  has anyone got any dyno results to prove that the ts produces more horespower (and where?) than a healthy nord ?

[MD]

Brad, I feel reasonably confident in saying that most skilled engine builders would say the ultimate (read practical)power from either engine is comparable- especially in racing applications. It may well be that up to a certain point, it is cheaper to make the power from a TS Vs the Norde however the Norde is still capable of matching the TS outputs given the right modifications.

The injected engine is more easily modified and will produce smoother idle and more linear power. The carburetted version may be more tempremental at idle and a bit harder to tune out a hole in output around 4-45000 rpm but after that it can be much of a muchness.

[Mat Francis]

Brad;

This picture, 1.8L Nord. Healthy motor with extractors, otherwise standard.

[Mat Francis]

This one; same car, same dyno. Now fitted with a stock standard, healthy TS.

I never drove any faster on the track with the TS, but that is solely due to my driving, and making too many changes to the car at once without learning how to control it properly.

Sorry if I've taken this a bit off topic Evan, but to get back to the point, the same car is definitely quicker and more responsive with the TS in it.