just a rebuild - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

geeaj · 02-06-2002, 03:48 PM

I would have to agree with the last post. Just because a Toyota Celica is running high compression with 93 octane (compression higher then the 10.5:1 planned for the ka24 rebuild), doesn't mean jack.

The Toyota has different fuel mapping and air/fuel programming then our ECUs. I suspect that the algorithms used retard timing during certain scenarios so that detonation will not occur.

What this means is that the compression isn't static, it changes based on the variables such as throttle input, air temperature, etc.

You can very well run 10.5:1 compression on street gas and still run like shit, your car pingin' for dear life on WOT. It all depends on the fuel/air management.

Given your situation, give Rick at Rebello motors a call. This summer, I plan on having them build a N/A ka24e running high compression (but not as high as what you guys are thinking).

Another aspect to consider is using forged versus cast pistons. You can save the money on forged pistons and use the money for porting/polishing (only worthwhile if ka24e...ka24de head are siamesed together so there isn't much metal to begin with.) *thx dpro/dave for that tidbit of info*

If your are not going turbo, forged pistons ARE NOT NEEDED. The cons of forged vs cast for N/A applications, simply outway the pros.

For one, there is cost. That is self explanatory.

Forged pistons have a very different expansion rate vs cast pistons. What does this mean in real day to day driving? Your motor will be noisier, it will not be as smooth.

Do yourself a favor and give the Rebello guys or Sunbelt motors a call.

02-06-2002, 03:48 PM	#13
geeaj Zilvia Junkie Join Date: Dec 2001 Posts: 357 Trader Rating: (0) Feedback Score: 0 reviews	I would have to agree with the last post. Just because a Toyota Celica is running high compression with 93 octane (compression higher then the 10.5:1 planned for the ka24 rebuild), doesn't mean jack. The Toyota has different fuel mapping and air/fuel programming then our ECUs. I suspect that the algorithms used retard timing during certain scenarios so that detonation will not occur. What this means is that the compression isn't static, it changes based on the variables such as throttle input, air temperature, etc. You can very well run 10.5:1 compression on street gas and still run like shit, your car pingin' for dear life on WOT. It all depends on the fuel/air management. Given your situation, give Rick at Rebello motors a call. This summer, I plan on having them build a N/A ka24e running high compression (but not as high as what you guys are thinking). Another aspect to consider is using forged versus cast pistons. You can save the money on forged pistons and use the money for porting/polishing (only worthwhile if ka24e...ka24de head are siamesed together so there isn't much metal to begin with.) thx dpro/dave for that tidbit of info If your are not going turbo, forged pistons ARE NOT NEEDED. The cons of forged vs cast for N/A applications, simply outway the pros. For one, there is cost. That is self explanatory. Forged pistons have a very different expansion rate vs cast pistons. What does this mean in real day to day driving? Your motor will be noisier, it will not be as smooth. Do yourself a favor and give the Rebello guys or Sunbelt motors a call.