Non-turbo 428rwhp FD build up and history by GtoRx7

5 minute(s) of a 136 minute read

1-16-2011

The 27 extra horsepower is not what makes it so much more powerful. Here is a comparison to explain. Lets say each engine achieves its redline, then shifts into the next gear. I will start each one at the correct rpm of second gear-

*10k 20b ---------*8.5k 20b----------Difference

6500 rpm 270hp 5000 rpm 180hp -- 90hp 

7000 rpm 320hp 5500 rpm 225hp -- 95hp

8000 rpm 365hp 6500 rpm 270hp -- 95hp

9000 rpm 420hp 7500 rpm 340hp -- 80hp

9500 rpm 428hp 8000 rpm 365hp -- 63hp

1000 rpm 420hp 8500 rpm 400hp -- 20hp

So you can see that in real life the extra 1500 rpm gives an additional 90 horsepower gain average over the majority of powerband.

No worries you are fine! I was planning on going 4 rotor after this, but honestly I have changed my mind. If we build a 4 rotor it will be in a different car, meant for a different purpose. Extra weight, location, heat, and expense in my opinion are not worth the extra power. It would be complex to explain and I will if someone requests me to post it. But in the end it just cant match this current setup of front/rear balance, lower CG and weight. 

Quick rundown of the three options, engine only- 

8500 rpm high comp, balanced, ported 20b- $11k 246rwtq 400rwhp

10000 rpm high comp, balanced, drysump, ceramic 20b- $18k 246rwtq 430+ rwhp

8500 rpm high comp, 4 rotor, drysump 26B- $23k 340rwtq 530rwhp

So for $5,000 more on engine, and roughly $1200 more on intake and exhaust, the 4 rotor is $6,200 higher expense than 20b. Additionally the mods to possibly make the 20b into a 450-480rwhp engine are not much more. I just need development time 

Since before this car was even started on, I wanted to use the Ferrari F40 for the power/weight benchmark. Now its been exceeded. In the real world is different than on paper though!

I thought it would be fun to look up and post several popular well known factory powerhouse engines. Here is the first- the world famous F40 ferrari. Only chart I could find. The red lines are a different car, yellow lines F40. You can see the outstanding boost response and power down low the F40 has. Enough to take many cars by surprise. 

Next up is a excellent comparison. The Ferrari F430. Being a full half liter larger, its is interesting to compare to my 3-rotor. Naturally aspirated, and 4.3 liters, its a prime example of well made power. This chart I think is stock vs modified. I used the modified one, why not. 

2010 Corvette Z06. Now this one I was nervous to even look up. Sure the n/a 20b in my lightweight Rx-7 will beat it. But engine vs engine...... what a scary challenge! Coming in at a massive 7 liters, its a full 3.1 liters larger! Look at the torque! Even a beginner driver cant miss. ANYWHERE in the rpm large power is there  However once both are in the effective powerbands, the micro 20b is only at a 22 horsepower disadvantage. 

Last one I found is my favorite. The Porsche 996 GT3. The best of the best in a 3.8 liter n/a package. With 435 horsepower and 317 ft-lbs, it produces a staggering 83 ft-lbs per liter! Very Very efficient engine. It will be my new personal goal of torque  This example has had full headers/exhaust/intake and computer upgrades. First line is without computer re-flash. Second is with.