ALFAGTV6.COM

[Mats]

O yes, I thought it looked familiar, I have looked at that starter too.
I see you piont about weight, I thought you had more acceleration through the whole course.
The seals around the VVT is a beatch to get to stay dry, seems like they never manage to pack the right piece of rubber in the gasket kits. :/
So the 155 head has the front left under-up screw through the timing cover in the Nord location? That sounds intresting...

[Mats]

I have now held a 155 TS 8v piston in my hand, what a difference compared to the 75 part! Much lighter, we're talking at least 100 grams...
The design of the piston raised a couple of questions though as the compression height is greater and there is a quite large dome as well, this means that either the rod is shortened quite a lot (bad move) or the crank is further away from the head (highly unlikely).
The crank itself seems to have a longer stroke since the engine is 1995cc compared to 1962 in the "old" TS, or so I've been told. Seems to be correct as all the 155 litterature states 1995 for the 8v TS.

So where does the extra millimeters go? Did they really shorten the rods even more (remember that they shortened it 1mm compared to the Nord already)? Why not move the wrist pin UP instead of down..?
What is the compression ratio on the 155 TS anyway?

[Jim K]

I finally accepted my fate and forked out some good money for a set of 38mm throttle bodies for the 12v 3liter. This diameter is just right for the flow potential of this engine, although the rpm for max power moves out of reach, necessitating other costly things like...rods ($$$)! We'll see...
The TB set I got from...ebay last week and I am expecting delivery soon.
We'll have a lot to talk about Maurizio!!
Jim K.

[Zamani]

Haha Jim, 6 throttles? We need to start a new thread.

BTW I have 3 sets of SPICA throttles (about 39mm each). They need to be cut and welded but looks promising. Cheap too.

[Jim K]

Hey Z,
I think you're going to have a hard time adapting the Spica TB's on the V6. I have a set of these and was looking at the same thing the other day...thats when I decided for something I'd have to pay for! The amount of surgery required just isn't worth it.
BTW, have you ever spent a long time in...jail? How the hell did you have the patience to open up the stock runners??? I opened one up to 38mm and I've just about had enough! How much do you charge for a 38mm set???Name your price!
Jim K.

[Mats]

Guys... TS! as in: this thread is about...

[Jim K]

Yo, Zamani, see what you did?? Now we pissed the big M off! Lets get outta the way,quick!
Jim K.

[Mats]

yeah.... YEAH!!

You motherbeatches, I blow you!!!



Just thought now we got this nice new forum, why not at least TRY to not go wildly offtopic in every thread after five posts.

[4sfed]

The 155 connecting rods are shorter than the 75 and 3 mm shorter than the Nord. I have no idea why . . . it makes no sense to me!?! Yes, the stroke has also been changed to 90 mm, but the block is the same as the 164. The 155, 164, 75 and Nord liners are all the same.

The Bonneville engine is a mix-and-match combination of 155 block with a Nord crank and rods (Carrillo) with custom pistons. The timing cover is from a Spica-injected spider. Cylinder head is a 155 and the 8 mm bolts from timing cover to head line up perfectly.

[Maurizio]

Maybe the difference is there to reduce the weight / innertia.
The 3 mm shorter steel connecting rod and a much lighter aluminium piston wrt the 75.

[Mats]

Thanks for clearing that up Jim.
Maybe they wanted a more torquey motor (lower in the revband that is)?
From an engineering point of view it is absolute madnesss though, increased force on the liners and surely acceleration forces on the rods.
On the second generation 155 stw engines they even removed one compression ring and made the wrist pin smaller to get a longer rod, everything to compensate for the silly bore/stroke ratio I guess.

That 8mm bolt moving around on the left hand side of the head is kinda interesting too, wonder what made them move it on the late Nords and then move it back to the previous position for the TS. It's not like they needed the space or anything.

[Maurizio]

Thanks for clearing that up Jim.
From an engineering point of view it is absolute madnesss though, increased force on the liners and surely acceleration forces on the rods.
On the second generation 155 stw engines they even removed one compression ring and made the wrist pin smaller to get a longer rod,

I don't know how forces of a combustion on top of a piston look like. But actually moving down the piston pin will reduce the radial forces on the liner. (M=F*l increasing l will lower F)

[Mats]

How do you figure? A beam with joints at the ends can only transmit forces in the direction between the two joints, shorter rod means more angle fron the centerline in the liner = more radial pressure on the liner.
Also means better angle for the transformation between a linear motion to a circular but more acceleration at TDC.

[Maurizio]

I was looking to the piston only, one pivot point (piston pin in connecting rod). Reacting force against rotating the piston has to come from the piston ring contact area. So moving the piston pin down will lower that contact force in piston ring vs liner.

But your comment is also true, there has to be a nice compromise in al the veriables.

[Mats]

The rings are floating in their grooves, they don't hold the piston centered, the oil film does that.
One of Newtons laws (the first one?) are about bodies in non-accelerating state and the fact that the forces acting on the body must then cancel each other out. Looking at the piston it is clear that it is not doing much accelerating in the side to side direction and since the rod can only take loads in it's own center axis direction there is a rather large chunk of the load through the rod that is transferred into the liner wall and it is getting bigger when you increase the rod angle from liner centerline.