N1 vs EPR?

[Ray_the_pilot 0]

Hi,I have mostly, also while flying the -400F, used GE powered engines which uses N1 for power reference. Now I have tested out the PW and RR powered aircraft, but find it difficult to understand the EPR reference on the EICAS. I also find it difficult to find any information about it. So I just wonder, can anyone tell me the difference between using N1 and EPR as a reference. I know that N1 is the power of the large fan in the front of the engine, but what does EPR represent? What do the numbers on the EICAS mean?RaymondNorway

[downscc 1,327]

EPR: Engine Pressure Ratio is the ratio of inlet vs exhaust pressure or a common turbojet measure of roughly how much power is generated. This same subject was discussed in some detail earlier, perhaps a search of the forum would help. N1 is no exactly the measure of power, simply RPM; whereas the EPR can be visualized as more more direct measure of power. Both N1 and EPR have limits, it is usually only one that is limiting depending on temperature and altitude.

[Ray_the_pilot 0]

Ahh...I get it. So the numbers on the EPR in EICAS is the actual ratio of inlet vs exhaust, right?I tried to search the PMDG forum, but I got up so many hits that didn't help me at all, that I decided to ask instead. I'll try to do a more thorough search. Thank you for your help.RaymondNorway