leggete questo:
The Cross-Fire Injection conspiracy/sabotage theory


The Cross-Fire System is much ridiculed for being a weak performer. This is not entirely true since it has more Hp than all standard option engines in the previous years Corvettes. The L83 Cross-Fire Injection was the only engine available that year so it can't be compared with high performance optional engines.
The standard L48 engine had the following ratings by year:

74/195hp
75/165hp
76/180hp
77/180hp
78/185hp
79/185hp
80/190hp
81/190hp

These account for the most Corvettes produced in these years so the 205 Hp L83 Cross-Fire Injection engine has more horsepower than the most C3 Corvettes on the road.

The problem however is that the Cross-Fire Injection system has tremendous low end torque but almost no high end Hp. There is however a reaon for all this. The Cross-Fire Injection system was originally designed for the LU5 305 cid engine for the F-Body cars. GM expected that the demand for 350 cid engines would drop when emissions laws became more demanding. When the 350 cid L83 was introduced they put the Cross-Fire Injection system on it. Also the manifold has a very poor runner design. The runners are very small at the cylinder heads (almost 2/3 of what normal runners are) to increase the torque. The L98 TPI (Tuned Port Injection) engine was however also designed for a 305 cid engine. There is NO difference between the TPI manifolds on the F-Body cars and the Corvette. This is the reason why the TPI also runs out of breath on high rpm's in the 350 L98. If you've ever driven a stock L98 you may have noticed that the engine sounds like an over-full vacuum cleaner on steroids at higher rpms.

There is a sort of sabotage/conspiracy theory about the Cross-Fire manifold's runner design.

Because the L98 Tuned Port Injection engine wasn't production ready the L83 Cross-Fire Injection engine was installed as an intermediate between the "old" carbureted engines and the "new" multi point fuel injection engine, the L98 with Tuned Port Injection. Probably the initial manifold wasn't so poorly designed and had larger runners and put out tremendous torque and Hp. More than the new L98 (that has only about 25 Hp more than the "sabotaged" Cross-Fire) That couldn't go on like
that, after the oilcrisis and the constant decrease in Hp the buyers
wanted more Hp and the L98 was supposed to bring this.

A stronger performing L83 wouldn't fit in this scheme and was sabotaged to make the L98 look more glorious.
The sabotaging was done very professional. They casted the manifold so (with an indentation in in the runner bottom at the cilinder head) that a handy do-it-yourself-portmatcher couldn't open the runners up so that a strong performing system could be obtained. As lousy as the craftsmanship is in the casting of the manifold, that good is done the act of sabotaging the stuff.

There is even more circumstantial evidence for this. The CFI system is a weak performer but is a direct descendant of the cross ram system found on the highest performing chrysler/dodge production engine. The crossram layout is in fact a very good design that combines tremendous low end torque with good high end Hp and streetability.

This all is just theory but in a way it does make sense.

This all does by no means mean that the Cross-Fire Injection system is a better system than the Tuned Port Injection system. The TPI system is a more sophisticated dry induction system (meaning that the air flows dry through the intake manifold and fuel is added just before the cylinder intake ports by an injector. This means all multipoint injection systems are dry induction systems) The Cross-Fire Injection system is, like carburetion, a wet induction system. These systems have problems with fuel puddling in the manifold and this is part of the reason they have a more lopey idle. Also multipoint systems have better driveability and throttle response due to the better controllable flow of fuel to a particular cylinder.