Fuel-injected Lancia Montecarlo intake layout

[Robert]

Guy and all others,

Context: Lancia MC equiped with Strada/Ritmo 130TC engine with injection.
Problem: Intake like Snakeman (Jenvey throttle 40mm dia same as DCOE) vs mine (Jenvey & horn 45mm dia)
See attached file for the drawings and different dimensions of different parts.
Precision: In a previous mail it seemed Guy prefers the fig B solution (despite the steps in the intake) so I ask if A' is better than A comparing to B...

Question:
Considering the actual configuration:
- 130 TC head : inlet valve=43.5mm. GC valve guides
- OE cams: 7 51 51 8 ; 10 mm lift
- 105 TC pistons giving CR:10.3
- GC MC manifold

and considering I don't want to change the throttle body (diam 45 mm).
Is the solution consisting to reduce the diameter of the horn like I drawn in fig. A' (or another way you can indicate) a good solution ?
Is it possible to get a gain in performance, specially in bottom end torque ?
Do you think the maping could remain the same in the ECU or the maping should be completely different (in this case I certainly give up).

Regards,

Robert
PS1: some snapshots of the work done on the parts.
PS2: I can give more details and photos...

[Guy Croft]

Rob,

Well laid out post, well done.

If I understand correctly you have 40 throttle bodes, and 45 trumpets (horns). So, going from a 45 trumpet to a 40 throttle body will only give a mismatch of 2.5mm on radius, which will not have any noticeable effect on power.
With the long trumpets as you have in the photo I'd expect higher-than-standard lower-end torque (in the range 1500-3600rpm) The standard 130TC motor with standard cams and 40 sidedraft carbs has 136lbf ft at 3600rpm, you will see more at 3600, maybe as much as 144lbf ft with injection and higher CR, fully flowed head.


GC

[Robert]

Guy,

In fact I've the 45 mm intake as drawn in fig A (TB and horns) allowing a very good alignment with the manifold thus allowing a good fluid continuity (theoretically).
Because you advise a 40mm dia for injected intake (eq to 45 mm DCOE carb) I ask if reducing from 45 to 40 mm my horns (keeping the TB because I don't want to replace them) will give better results. Because the velocity thus the pressure etc...

In fact the figures measured on dyno show that the torque is higher than the "130TC OE" from 4000. I hoped more torque in low revs. Measurements:

3040 3500 3939 4230 4600 4927 5250 5600 5895 6180 t.mn
16.9 17.1 17.4 18.1 18.2 18.0 18.6 17.8 16.8 15.9 kg.m
.....
Could you explain us the way you find the rev torque with the lenght of the intake...

Sorry to ask several questions in the same post but every things are linked and I'm so interrested in this part of physics.

PS: you say that 5 mm on the dia is not noticable but the increase of Surface/area is 26% from 40 to 45mm. And if I use my electricity background, a flow is proportionnal to S...

Au plaisir,

Robert