[stradguy93]

I'm trying to learn more about the variable valve timing in Alfa's 1980 spider. Do all 2.0's after 1980 have it? Also is it cam phasing or cam changing? How does it work, I know it is mechanical but what triggers it to work?

 

[Tifosi]

?

I could be utterly mistaken, but I don't believe the VVT was something that appeared until the series 3: 1982 (pretty sure of that in fact)

If so, and if you've got one in an '80, then someones done a transplant with a later setup.

That being said, if present, the electrically controled version will have a big doohicky hanging off the front of the cam cover on the right front corner. Mechanical/interia types use a regular/stock/unaltered cam cover as the whole deal is contained on the cam itself without any external devices.

The solinoid/electric type works by changing a pressurized oil passages path through the device which in turn rotates the cam gear on the end of the cam in such a fashion that it advances cam timing by approximately 11 degrees.

I 'think' the interia type does the same thing AFA oil passage alteration, only flyweights (and this RPM) determine when the device activates.

 

[Tifosi]

Mmmm.... pitchure:

 

[andy303]

I have a Brooklands book of Alfa road test reprints in the library next to the "seat of ease" that I consult on occasion, and I seem to recall reading a article that said the centrifugal advance VVT on the intake cam was first introduced about 1980 along with the infamous single throttle SPICA setup as part of Alfa's struggle to remain emissions compliant. The reviewer was impressed with Alfa's technical prowess in that regard, but like most reviews from that period found the rest of the car to be somewhat dated. Philistini maldetto!

 

[Tifosi]

Well there ya go.

 

[Alfar7]

VVT Cam mounts

Both late & early mount to cams the same way. "Screw & Glue".

The pic is of internal VVt parts, not of cam mounting, FYI.

The early VVT can be modified and used without electronic hassles with good cams even on carbed cars..

 

[60sRacer]

Richard,
The mechanical vvt looks like it has a special cam - with a spiral gear on the end. Can good racing or high-performance cams be ground on this core, or are they otherwise available?

Seems like a good way to use a high-lift, high overlap cam set with some cam retard to get a decent idle. Anybody (besides Murray and his electronic wonder dual vvt) try this?

Robert

 

[Tifosi]

The early VVT can be modified and used without electronic hassles with good cams even on carbed cars..

I seem to recall you had words somewhere regarding tinkering the timing of the mechanical type through tweaking the weights and/or springs to be more of a performance advantage rather than to gain emission compliance, correct?

 

[stradguy93]

so does the vvt increse with rpm or does it kick in at a set rpm?

 

[stradguy93]

what type of vvt would a 83 have on it?

 

[papajam]

Your 83 has a centrifugally activated VVT when the crankshaft exceeds 1650 RPM.

 

[msiert]

Richard,
The mechanical vvt looks like it has a special cam - with a spiral gear on the end. Can good racing or high-performance cams be ground on this core, or are they otherwise available?

Seems like a good way to use a high-lift, high overlap cam set with some cam retard to get a decent idle. Anybody (besides Murray and his electronic wonder dual vvt) try this?

Robert

FWIW

Here are some conversations I had with my engine builder about the Montronic VVT. Don't konw how it differs from a L-Jetronic's

I had to buy a used VVT for the exhaust side and found that it's advance was different then the one I had.

Here is what Steve said about it:
"The intake cam advances 14.5 degrees when the oil valve is closed. This is more than indicated by the service manual so I was skeptical of the numbers. I then took apart the cam that I purchased to use as your exhaust cam and found that it did match the 11.65 degrees that the manual indicated. So Alfa evidently made a change in the VVT timing somewhere along the way. It will be easy to make spacers that will reduce the advance for the race engine."

Spacers were made to change the advance:
The spacers for the VVT cams are made so we can cut the stock advance of 22 degrees down to anywhere between 3 and 10 degrees.

Results at 1st dyno with 4 degree advance:
Bob tried the VVT cams and found that he gained 4 hp at high rpm with the advance turned on. There was no change in the power at lower rpm. On the exhaust side, with the advance "on" he gained 3 hp across the full rpm range, indicating that the initial setting should probably be set with more advance.

Final dyno:
On the final dyno with a different exhaust system we pick up considerable HP but with the advance turned on the VVT had zero increase in HP across the rpm range...................Don't know why and by this time I just wanted the car back and we ended the testing.

 

[Tifosi]

so does the vvt increse with rpm or does it kick in at a set rpm?

Inertia types are RPM related while the solinoid types are tied into throttle position. (anything beyond 57 degrees deflection of the TPS kicks it on)

As they both work with redirection of oil flow, its relatively safe to say that they are both either on or off with no progression in between. The oil flow changes ports, the VVT advances the cam.

 

[junglejustice]

By the way, on one of the Spiders that we converted to the fully-programmable, stand-alone GoTech EMS, we drive the vvt straight from the ECU. You are able to then trigger it at ANY rpm you want - since it is simply triggered via a solenoid-switch!

That output trigger from the ECU is simply set to on AND AGAIN TO OFF at user-directed rpm-levels!

Worked great!

 

[Alfar7]

Vvt

Simple things first.

Murray:
VVTs on exhaust... are only for emission motors
Advancing the exhaust cam moves it from "best performance to better torque" (Tq creates Hp) usually a good thing in street motors, but with VVTs on that side, they are a waste of your $$.

The best position for a "performance" exhaust cam is where it is set so there is clearance of .090 between Piston & valve. Any change in that and exhaust cam timing is about something else. But exhaust cams are exhaust cams. General purpose cams are not.

The best setup is proper cam designs on both sides! Ask Bill!

As to VVT use:

Using high lift Performance cams with VVTs modified to advance at 27500-3000 RPM is somthing I have done for years. It is simplier for me to use Centrifugal as I understand the significant unreliability of any electrical component in a race environment. VVTs only do one thing and above the trigger RPM who cares. There is no reason to turn them on & off. Unless you are in Calif. No other sources of oil leaks either.
I won`t change my mind, so don`t bother arguing.

They all screw onto cams and are "LockTite"`d in place. See front & back picture below of both designs with the RJR221 intake cam on a VVT core.

This is a 12.1mm lift cam with Very Torquey high HP profile that is the same cam used on Bob Hoye`s (Subtle) 2 liter 101 Spider (without VVT but you need it with FI)

The elec VVT can be mod. for reduced advance on intake but 8 is the minimum worthwhile.

 

[60sRacer]

Thanks Richard.

Do I understand correctly?
Mechanical VVT on the intake only is good. Little advantage on the exhaust side?

I'd love to drop in a modern 12mm lift cam set - I have an older Shankle performance cam which is great for power but lumpy at idle (high overlap). 2L, 10.5 CR Borgo pistons, head shaved .040 for CR somewhere around 11. I use thick copper head gasket to bring the CR back down with modern (too much alcohol) fuel.

Robert

 

[Vintre]

VVT different?

So Alfa evidently made a change in the VVT timing somewhere along the way.

This comment caught my eye right away.

Sorry to ask AGAIN, but I swear that since I replaced the VVT in my '91 with a used one (don't know what year it came from), there is a slight hesitation when increasing RPM's. Not a big hesitation, but enough for me to feel it.

I started this post http://www.alfabb.com/bb/forums/spider-1966-up/128187-vvt-series-3-4-a.html and thought that VVT's were the same, only difference was how they were activated.

So, to ask again, is it possible that VVT's are not all interchangeable?

Confused but what else is new?

 

[Alfar7]

VVTs

So, to ask again, is it possible that VVT's are not all interchangeable?

They are. You should have enough mechanical savvy to set timing as when they screw down they will require adjusting.

Mechanical VVT on the intake only is good. Little advantage on the exhaust side?

VVT as Alfa builds is only good on Intake, Elec or Mech.

 

[mbb]

the Alfa VVT looks like it is designed to RETARD the intake cam from an initial, about, 114* before TDC to about 102*, assuming about 12 crankshaft * built into it's mechanism.

This correct?

Thanks, Martin

 

[Alfar7]

Retard?

the Alfa VVT looks like it is designed to RETARD the intake cam from an initial, about, 114* before TDC to about 102*, assuming about 12 crankshaft * built into it's mechanism.

This correct?

Thanks, Martin

114 to 102 is retard? Hmm......?
I think there needs to be more reasearch & less typing mmb