1750 TBI sector
It’s official !
We are happy to announce that MTD has started developing tuning parts and custom softwares for 1750 tbi engine.
The reason of our existence may be the development of multiair engines , but the fundamentals of our philosophy is maximising the performance and efficiency of I.C.E. beyond limits. This can be achieved only in combination with advanced variable timing systems. That’s why 1750 tbi engine should be at our development list.
A few specs of 1750 tbi engine:
-1742 cm3 or 106.3 cu-in
-83 x 80.5 mm / 3.27 x 3.15 inches
-16 Valves Turbo
-CR 9.5
-Direct injection
-Double variable timing cam system
How Alfa double VVT works
Alfa Romeo makes use of a variable phase camshaft gear for both intake and exhaust camshaft, controlled by the ecu. It’s not the first time we have seen this kind of system , actually they have developed it since the 80’s , long before BMW presented their version with the Double Vanos system.
The philosophy of this system is to advance/retard both camshafts in order to create negative, zero or positive OVERLAP.
NEGATIVE OVERALP
Conditions of idle , low load driving , low emissions demand , low consumption demand .
Intake and exhaust valves are never simultaneously open at the whole cycle. This means that a/f mixture cannot escape at the exhaust. Maximum dynamic compression is achieved at conditions that intake air has not enough kinetic energy .
POSITIVE / MAXIMUM OVERLAP
Condition 1 - Scavenging :
Turbocharger has stared building boost which means incoming air has gained some kinetic energy/ momentum. Absolute pressure at intake manifold is higher than pressure at exhaust manifold. This allows the cylinder scavenging if exhaust and intake valve are both open for sufficient duration. As a result turbine wheel spins up immediately at the the maximum rpm we wish. Although it is not recommended for high rpm , because as rpm increase , backpressure is also increased at the exhaust manifold, causing gas returning inside cylinders , decreasing maximum power.
Condition 2 - internal EGR :
At very low rpm and vacuum conditions , absolute pressure at exhaust manifold is higher that the one at intake manifold. If the combustion quality is not sufficient, oxygen sensor will detect unburnt oxygen at the exhaust. Maximum overlap will be chosen by the ecu in order to recirculate exh gases back to intake manifold. That way combustion efficiency is increased and fuel combustion redused.
ZERO / SLIGHTLY POSITIVE OVERLAP
At condition of high rpm and maximum power, zero or slightly positive overlap is requested by the ecu . That way it achieves the maximum volumetric efficiency of the cylinder, preventing gas returning because of backpressure, at the same time. Maximum dynamic compression and thus cylinder pressure is achieved at this point.
Tuning potential
Taking advantage of this contentiously double variable timing we can improve we can the cylinder filling at each strategy by using custom designed camshaft profiles especially for this job . In combination with upgraded exhaust and intake systems we can achieve maximum resonance at a big rpm range , increase even more the volumetric efficiency and achieve great results.
Tuning potential:
Taking advantage of this contentiously double variable timing we can improve we can the cylinder filling at each strategy by using custom designed camshaft profiles especially for this job . In combination with upgraded exhaust and intake systems we can achieve maximum resonance at a big rpm range , increase even more the volumetric efficiency and achieve great results.
