Holley EFI

[twobjshelbys]

What is your motivation for an EFI system in an old technology engine? It gains you virtually nothing over a properly adjusted carb provided you don't have adverse usage conditions:

1. Track/autocross
2. Huge changes in elevation, ie, sea level to 10,000+ feet for extended periods of time, ie, Phoenix in the winter, Aspen in the summer coupled with aggressive driving (ie, having fun on twisty high mountain roads)
3. You have or want a faux weber setup. I wouldn't wish a set of real mechanically connected Webers to anyone. Really. Maybe there are a few that are talented enough to keep them properly adjusted but unless you're one and want the Weber look, EFI is the only way to go.

In the case of #2 the only way you gain an advantage is IF you use a MAF system since without it the EFI system will not do altitude compensation. Please note the MAF does not dynamically adjust for altitude. There can be no flow over the MAF during the period altitude is sensed since it uses static air pressure. (It's not really measuring altitude but air pressure/density from which it infers an oxygen content for determining AFR.)

If you do not have a MAF then you end up with a static tune for the EFI at your altitude and you have the same issue as with rejetting a carb if you change altitude. Both a carb and a static EFI tune will operate just fine if you change altitude operating conditions for short periods - ie, a drive across I70 tunnel or if you visit Denver for a week.

What is the difference between a EFI system and a well adjusted carb? About $5000.

EFI systems in a Cobra are an even more compromise than putting one in say a Mustang. The reason is that there is no IDEAL place to put the O2 sensor. My setup actually had two locations (not sensors - only one at a time). One in the header right off the cylinder exhaust and the other in the passenger exhaust just after it went from the 4 tubes collected to 1. It is not possible to put the O2 sensor in the ideal upright position and the near horizontal is not ideal, and the muffler location is prone to false readings at low idle speeds due to air getting back into the exhaust. The single cylinder location overcomes that but the downstream at least gives you averaging of 4 cylinders. I don't know of anyone that is running two O2 sensors.

Then after it's all done, you've got to seek out a shop with a dyno and a tuner that knows your system. The "self learning" systems are OK only approximate. If you're OK with that then you'd be OK with a carb out of the box.

Just (consistently) my 2c worth.

PS, I had EFI on my engine and very nearly had Roush switch it back to the carb version. I admit it was a system they didn't understand and have since abandoned due to its complexity. I needed EFI because my typical driving DID involve 5000' to 12000' and the engine would backfire when going high because it ran rich. In all it cost me nearly 20K to get it running correctly and I got to learn alot about EFI systems which is what led me to the conclusion that if you are in a static environment, a carb will perform as well for a lot less money.