What about boost hurts a rotary? IF I could hypothetically get 25psi @2000rpms and taper the boost down to 15psi by redline, would I still get the benefit of good low end torque without the damage of high boost at redline?

 

its not boost that hurts a rotary, detonation/preignition hurts a rotary. many causes for detonation, and it can be hard enough to detect that the first clue is a dead engine.

 

LOL first clue is a dead engine LOL

 

i've been around long enough where the 3rd dead engine sometimes isn't the first clue.

 

Turtle13
What about boost hurts a rotary?
What about boost hurts a rotary? IF I could hypothetically get 25psi @2000rpms and taper the boost down to 15psi by redline, would I still get the benefit of good low end torque without the damage of high boost at redline?

I am not sure high boost at redline is harder on the rotary than full boost at 2,000rpm, but then I am not sure how to go about calculating this.

Mazda achieved full boost at 2,000rpm on stock engines no problems, so there is that.

Is this something you want to do or just an idea you had?

You can really change the power curve of a rotary as my EFR dyno below shows, but if you made 26psi at 2,000rpm and 15psi at 8,000rpm I have the feeling it would be the kind of power curve where you shift at 4,000rpm to get back into your torque at 2,000rpm anyways.

This is 26psi ~3,750rpm tapering to 21psi at 8,000rpm on a single 57mm/76mm compressor. Its felt equally fast shifting at 6,500rpm or 8,000rpm on this, but any more boost drop (less peak hp) and it would be better to shift at 6,500rpm IMO.

 

BMEP, Brake Mean Effective Pressure, basically its a calculation from Rpm, torque and displacement. combustion pressure would tell you the same thing.

 

Maybe this guy has built the most bad *** compound turbo set up for a rotary... but i doubt it.

 

Quote:
Originally Posted by BLUE TII
I am not sure high boost at redline is harder on the rotary than full boost at 2,000rpm, but then I am not sure how to go about calculating this.


j9fd3s
BMEP, Brake Mean Effective Pressure, basically its a calculation from Rpm, torque and displacement. combustion pressure would tell you the same thing.

Definitely a factor.

As far as harder on the rotary you have to look at how peak combustion pressure is going to affect bearing loads and other lubrication requirements as well as how the boost is being produced with will affect EMAP and EGTs.

A small turbo or antilag will produce much higher EMAP and EGTs, a traditional belt driven supercharger will produce much higher bearing loads on the front bearing.

Here is a really practical example. Oil pressure- do you have adequate oil pressure at 2,000rpm to deal with the bearing loads of full combustion pressure?

I remember reading a thread here long ago that had CCM of rotary main bearings and it showed wear adjacent to the 3 zones of peak combustion pressure corresponding to the 3 rotor faces.
So, bearing loads for a rotary do have a lot to do with combustion pressures as well as the high rpm loads that decades of NA racing has taught us how to work around.

I don't have answers, but like the OP I want to find out.

I don't think I will be able to get peak torque/peak boost lower than 2,500rpm with the two sequential EFR 7163 turbos I want to use and contrary tot he OPs question; my whole reason for doing the sequential EFR 7163 instead of improving spool on my existing EFR 7670 is because I DON'T want the boost/torque drop at higher rpms.

 

See there's nothing wrong with taking advantage of a rotary engines full rpm range. Now you know why I started that 20b rev limit thread.