High compression on low octane

[BongoBennie]

It's been a while but this seems to be the place to ask "dumb ass questions" per FB K series groups.

I have a K swapped Insight with the goal of power AND economy, I've had a K20a3 with 11.5: compression and 5psi of boost, 3.4 final drive and while its a blast to drive I average 30mpg with 40mpg being my tank record. Meh

I now have a K24a4 on the stand and will be swapping it in next year. No turbo, well muffled. Stock compression is 9.7:1 and made for 87 octane.

I'm interested in running higher compression on 87. TSX engine is 10.5:1 which seems possible. what about higher?

My thought are that the car is almost half the weight of the original Element/Accords the engine came from so the load will be less.

My other idea is to add EGR to the system and control it with Kpro or maybe another means.

Also FWIW I fully expect less power than my current setup and I'm cool with that, I have other cars for that.

[Gasoline Fumes]

The original Insight engine was 10.8:1 and only required 87 octane. But I don't know how that translates to a K-series.

I've driven a manual K24 CR-V and really enjoyed the engine. It's gotta be awesome in a lighter car! Cheap and torquey! But I think I'll be sticking with the 64 MPG 3-cyl.

[JRMichler]

Originally Posted by BongoBennie

I'm interested in running higher compression on 87. TSX engine is 10.5:1 which seems possible. what about higher?

Also FWIW I fully expect less power than my current setup and I'm cool with that, I have other cars for that.

The engine in my previous GMC Canyon had, if I recall correctly, 10:1 or 10.5:1 compression. It ran well on 87 octane. The best ambient temperature for gas mileage was about 70 deg F. It lost about 1 MPG per 10 deg F at lower temperatures. The mileage did not improve at higher temperatures. I think that the knock sensor was retarding ignition timing at temperatures above 70 deg F.

I saw timing as retarded as 2 deg after TDC at high manifold pressure and low RPM, and as advanced as 45 deg BTDC at low manifold pressure and higher RPM. That engine would slowly and smoothly accelerate from 21 MPH in fifth gear, which was about 600 RPM.

Your higher compression should be possible. Pay careful attention to ignition timing vs RPM, intake air temperature, engine temperature, and manifold pressure to prevent detonation. You may need a knock sensor to get your timing fully dialed in. I would not be surprised if getting smooth running at low RPM required ignition timing a few degrees ATDC at higher manifold pressures.

If you are happy with less power, try a camshaft with delayed intake valve closing to get some Atkinson cycle effect.

[Logic]

BYD serial hybrids with direct top gear have an ICE running 16 to 1 compression,
I posted about it here"
https://ecomodder.com/forum/showthre...6-a-41587.html

The only other place I have seen talk of successfully increased compression without ping is here:
https://turbobricks.com/index.php?th...y-tried.66779/

I would say low hanging fruit is you want your intake charge as cool as you can get it.
In a dry climate; using an Ultrasonic Mist Maker (or Pond Mister) or 10 to produce max mist for per 'space required' for evaporation in the intake may work.

https://www.youtube.com/watch?v=jekXeBRZnGY