I am unsure of the airflow units. It could be one of the lesser used mass units... grams/sec * 100 maybe?

 

And thy Lord Wankel proclaimed to the admins: Thou shall not fail to Sticky

There should be a 20B-REW FAQ for this specific purpose. Combine this thread with the Torque curves (https://www.rx7club.com/20b-forum-95/20b-torque-curve-stock-twins-vs-naturally-aspirated-933797/), DMRH's dyno run thread (https://www.rx7club.com/20b-forum-95/20b-rew-dyno-550648/) and then link to my "12 Days of Rotormas" build thread (for FC-specific issues and solutions) and that would sew up just about all of the loose ends currently not known to anyone seeking to use the Cosmo twins.

 

you do know the secret sauce turbo upgrade is to swap the stock HT-15 and HT-10 for an HT18 from an FC and HT-12 from an FD?

 

I was thinking about that a month ago, might make for a cool springtime upgrade. Already got a HT18 sitting on the shelf and my buddy has a spare set of FD twins with one blown turbo.

 

done.

 

I was thinking about this as well BUT, looking at the impeller housings from the FD secondary and the ht-18 from the FC... it doesn't look doable. I mean, the inlets need to line up (or at least be the same shape) and they arent. But yeah really all you need to keep would be the center section of the twins... the issue really lies with the inlets. Now if this CAN be done, we would have some seriously fun 20b turbos to play with.

I spoke with Brian at BNR about their 20b upgrade, but we came to the conclusion that max power from a set of re-worked stock turbos would be between 450-475 whp @15psi . Since you can get damn close to that with a 13b, it's not really worth it to stick with the twins. So, how do you swap an ht-12 and ht-18 in? Inquiring minds want to know

 

What about an ht18 and the ht15. i wonder what rpm the ht15 would spool at, or if you would need to stay smaller with the ht12 from the fd twins.

anybody got pics of the 20b twin turbo package? would they in anyway fit an fd exhaust manifold? whats the turbo side flange look like?

 

Not quite sure about using a HT-18 for the front and HT-15 on the rear.

Here's a pic of the mounting flanges, from my build thread "The 12 Days of Rotormas":


Assuming that Hitachi and Mazda did everything numerically, the HT-18 would be 50% larger than the HT-12 and HT-15 being 50% bigger than a HT-10. And by that reasoning, a HT-12 would be approximately halfway between a HT-10 and HT-15. Maybe after my car is done and running nicely, I'll crack open the spare twins here and do some measuring.

 

by eye, you're close. the HT-15 is right in between the HT-12 and HT18. however the HT-10 and HT-12 are really similar, unless you had both to compare, its hard to tell, the wheel sizes are very close.

the HT-10 and HT-12 also seem to share center sections (i believe its like a garret t2/t25)

and the HT-15 and HT-18 share center sections.

there is an HT-20 also, the RB bonneville car used TWO of them

 

Then there are

BNR Upgraded 20B turbos.

 

Might as well revive this, there is still more to learn. And i have a twin turbo Fc setup to be completed soon.(turbo is mounted, just running lines and small fabrication)

 

Thanks.