Loss of power going thru bends

yes, that`s true....
for the Stratos new carbs had been developed, but they are higher and don`t fit into the Ferrari Dino...

 

The Weber DCNF's were designed for an east-west orientation such as in the Fiat-Dino. In the Dino 246GT it is north-south. In left-hand bends you can experience fuel starvation, in right hand bends you can experience flooding. I have played and adjusted my carbs to where they're "pretty good" and I'm 90% happy with the performance(I can offset the issues with throttle position before going into the turn). Matthias is correct (as "almost" always) that the Stratos used the Weber IDF carbs. The 500 Dino motors that were delivered to Lancia for the Stratos were identical to the Dino except Lancia installed their own intake manifold and IDF carbs. I have an NOS Stratos setup on my work bench ready to install soon. Also I've completely digitally scanned my engine compartment and the engine deck lid along with the Stratos induction system. All my data so far points to everything fitting under the stock deck lid with a prototype OEM looking airbox/filter assembly. The stock height of the original Stratos airbox was very thin. I am encouraged it will all work. Of note is the stock Stratos didn't have velocity stacks inside the thin airbox. The system I've designed has very thin custom rapid prototyped mushroom shaped velocity stacks inside the airbox. In any case, I'll report back what I find.

Freeman

 

Excellent project.
The trumpets are one of the tuner's tools

How much "loss" are you experiencing?
It should just be a minor stumble and would depend on your carbs being in tune. Jump to 1:05 in this video to see the starvation being minor but present and predictable in Dino 05082. So slight that it needed to be pointed out to the passenger
https://www.youtube.com/watch?v=n1s2iHEL7vs&feature=relmfu

 

I think this is what most Dino owner's experience with the DCNF's. I am curious to experience the difference with the Stratos IDF set-up. The good thing is, it's basically the same four bolts that hold the assembly on, along with hooking up the linkage and fuel lines. Totally reversible bolt-in/bolt-out.

Freeman

 

Sounds interesting Freeman, keep us posted on your progress as it will be a good engineering project to discuss.

Personally I don't buy the orientation theory [just my opinion] as the carbs will be subject to roll either way or pitch and yaw under braking. To empty the fuel bowl x 3 so quickly when the throttle is re-applied and momentarily doesn't figure.

I think the problem is in the design of the carb itself and most of the problem comes in the size and location of the progression ports / holes. It always seems to happen in that range.

I have pretty much cured most of the stumble on my car since upping the idle jets to 0.55mm and decreasing the AC jets to 190.

Sooo much better driving but I seem to have a tad more effort when hot starting. Perhaps I need to learn a new approach?

 

This video shows the heart of the Dino and it's potential! The fun starts at 2:27!

https://m.youtube.com/watch?v=mXgWWNJVdYA

Freeman

P.S. No stumble!

 

I'd have to look at diagrams of the carbs, but my recollection is that the float bowl on a dcnf is toward the front of the engine. This would be ok on a longitudinally mounted engine because the gas would be trapped in the bowl during braking, when the throttle is closed. But as mounted in a Dino the gas is held in the bowl by centrifugal force during a left hand turn.

The IDF has the float bowl between the chokes so it is less prone to that happening

 

How is the driving characteristics with the Stratos set-up?

Freeman

 

The car had this setup when I got it and it is the only Dino I have owned, so I can't compare it to a standard car.

It drives great after some time on the chassis dyno to adjust the carb jetting.

Jim

 

It would be great to see your Dino and meet you one day. We have a great C&C in Aliso Viejo every Saturday. I take my Dino there on occasion. Never a problem finding a spot whatever time you arrive. https://www.facebook.com/candcav/

My friend Derek who is a young Ferrari/vintage sports car tech is usually there. He's really great on Webers, vintage Ferraris, Lancias, Porsches, Alfas etc and has his own shop.

Freeman

 

I track a Daytona, which has essentially the same carbs as the Dino, mounted 90 out. We had to seal up the vent hole in the float bowl. My vent faces the rear, and vents to the emulsion tubes, when it overflows.

In turns, both left and right (remember, 90 degrees out) I would flood my emulsion tubes with gas that was overflowing due to G's from that vent. We sealed it up, and fashioned a vent tube out the top. I was fine in braking and acceleration.

I look at Weber's design, and I can't fault it, as when I get fuel out the vent, it gets pulled back into the motor from the emulsion tubes…..a flooded engine is better than fuel where it could get ignited outside the engine.

Below you can see our tubes or chimneys as I call them….in front of each intake.

One of the weber experts told me how to fix my problem….buy sh#ttier tires, lol.

Hope this helps

Bill
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Thanks Bill!

We actually tried that. I found that Gene Berg of VW racing fame used DCNF's on Bugs modified with snorkels. The carbs were orientated the same as a Dino. He created a snorkel from the small vent hole from the floats. We got some extra 308 tops and did this. Really didn't do much vs the stock tops with the float level at spec. We even tried lowering the float level to absolute minimum. Always a "bit" of starvation in corners under high G's. We truly experimented with everything and anything we read or researched. I have an area where we tested that we could get up to high speeds and high G turns. We got it tuned really well but always that small stumble on high G turns. You can always eliminate it by adjusting throttle position though. My DCNF's are now set back to stock specs with .55 idle jets (we experimented with stock .50's and fatter .60's as well).

Freeman

P.S. Nice motor by the way!

 

Freeman,

Thanks for the compliments.

I still do have a small stumble around corners when the G's come up. I have some wider rims, 9" front, 11" rears, so I have more movement (angle) of fuel in the float bowl.

Bill

 

At some point I'm hoping someone will experiment with fuel injection. I see that Jenvey makes a direct replacement for the DCNF as a throttle body that looks like a DCNF and looks to be possible to bolt right up to a stock intake manifold and use the stock air box Twin bodies DCNF style : TC body 40mm. DCNF - Jenvey Dynamics

Freeman
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The factory did try fuel injection for the Dino I think more for emissions than performance.

 

Have you researched any fuel injection options? What solutions were used successfully on the Stratos?

Freeman

 

I know a few Stratos ran the Kuglefischer injection. I had a pair of NOS fuel injection manifolds for the 4-valve engine. Used butterflies and dual injectors in each port. I sold them to Roberto Cassetta as he has an original racing 4-valve Stratos project that used fuel injection back in the day. He is still looking for the injectors and maybe the pump as well.

 

I've been in contact with Robert Cassetta. He's been very helpful. My colleague at work also has a Dino, a '71 Italian spec GT. He bought it years ago with the 4 valve motor installed but with Weber IDF's. The IDF's sit higher than on my motor, I think because of the heads. He has been in corresponding with the guy that built it. We can see the heads were intended for injection, possibly slide valve. I'll take some photos of the motor next time I see it. His goal is to recommission it.

Freeman

 

It might be you are doing higher g's than I. My favorite places are some 270 degree onramps near me where I can get the car to rotate slightly on the throttle. Helps to have cheap Sumitomo tires.

You probably saw this youtube video I uploaded:

https://www.youtube.com/watch?v=RXDlHQbypuo

I believe I did speak with you for a few minutes at the Best of France and Italy show a few years ago. I recognized you because you had a Dino t-shirt on.

Jim

 

Jim,

Fabulous video, fabulous Dino! I hope to meet you again!

Freeman

 

The same basic 4-valve engine was used on the Dino Tasman and it used slide injection.

 

Not great when airborne
https://www.youtube.com/watch?v=sJSynKt0X2s