Zooming in on both exhaust ports (when viewed from the engine), we can see the bypass door is closed, which causes the exhaust from the rear rotor to bypass the rear turbo and go through a crossover tube to the forward turbo. You can see the bypass channel on the left side of the photo inside the manifold.
The sequential turbo system in the FD RX-7 is impressive from a packaging standpoint, and it does an amazing job at improving low-end response and power with early 90’s turbo technology.
Its easy to make 200lb-ft of torque at 3,000-3,500rpm with a downpipe and exhaust. However, the stock turbo maxes out around 350whp and modified twin turbos are significantly laggier and will only increase that output by 50-60whp. Meanwhile, a Borg Warner EFR 7670 will get to 200lb-ft of torque before 3,000rpm and will make more power. The larger EFR 8374 will have similar spool as stock, with exhaust work, while producing 400-450whp on pump gas.
Needless to say, modern turbos are far simpler, reliable, and can outperform the 30-year old twin turbos.
The stock Hitachi HT12 turbos have tiny 57mm, 10-blade compressor wheels and a 51mm, 9-blade turbine wheel.
With the power steering pump removed, we were getting closer getting inside the engine.
There was still a lot of burnt deposits on the engine from the fire.
4 comments
Good luck! so sorry about the fire mishap.
Looking good 😊
I love how this project went from “OEM+ Restomod” to “make our rotary engine one of the most highly-modified 13B REW engines on the planet.”
Yeah, fires, pulling the engine, downtime, boredom, and beers have the effect of changing the strategy. lol.
We originally planned on retaining the stock motor for a while, do a lot of baseline testing and comparisons and then slowly upgrade the fuel system, turbo, and other bolt-on parts. Since the engine was out, we decided to tear it down entirely and go for an extreme build instead.