Let's assume 20B, rebuilt, single turbo (T66), and the fuel and electronics to run it. This is going to be a summer vehicle. By summer, I mean all summer, so it needs to be reliable. The turbo is fairly large so the ports are going to need to be opened up... What would you do?

Aaron

 

stock ports the T-66 is small for a 20B.

 

Really? I've actually just starting to reseach the 20B (I'll be sorcing parts next Fall) I am doing this for my senior design project for school here in Mankato, MN. A T78 is pretty big and moreover a lot more expensive. What would you suggest?

 

By a T78 I would assume you mean a Greddy T78, ( I don't think Garrett makes a T78, they go T72, T76, T80 and T88) that too is to small for a 20b. A 20b with any other port job besides stock would suffocate pretty much anything smaller than Garrett T66, and then a Garrett T66 and T72 maybe small depending on the port job. Search Red-Rx7, he made 630ish rwhp on a Garrett T72 with a 1.32 A/R and above 6000rpm the turbo was chocking and eventually died so he up'd to a Garrett T76 which is what I have. A well port'd 20b can flow ALOT of exhaust gas!!!

 

https://www.rx7club.com/20b-forum-95/mr-lvs-3-rotor-dyno-run-380264/
http://homepages.paradise.net.nz/gwmaz/drag.html
http://www.mymazdarotary.com/your_ma...x-7_photos.htm
http://www.msprotege.com/forum/showthread.php?t=52572
http://www.3rotorrx7.com/images/My3Rotor/index.htm

 

Thanks 20B_3rd_Gen and Evil_Aviator for the info. I had no idea that they could flow so much. I'll check out the links.

 

All T-66's... Very Nice.

 

If you run the numbers, the Turbonetics T66 is too small.
The GReddy T78 is too small also.

The 20B can easily push a Turbonetics T76, by the numbers.
The 20B can push a GReddy T88 - easily the smaller ones, and quite possibly some of the larger T88's - there are more than one model of "T88".
I think sillbeer ran a T88 on his 20B FC?

By the numbers, the 20B flow matches these turbos "well":
Turbonetics T76
GReddy T88
HKS T51R SPL

I don't consider anything less than 600hp on a 20B to be a large enough turbo.


-Ted

 

Imagine that!

Actually, the GT-42R is probably a better turbo if you plan on a lot of porting, but the T-66 has proven to be a good turbo for stock or mild porting. Other common turbos include the T70 and T72. If you have the money, I would recommend the newer GT-R series turbos that are more efficient and faster spooling than the older T-Series turbos.

I think that it is best to start with the stock 20B-REW, and then move up to aftermarket turbos later on, after the rest of the car is dialed-in better.

Edit: I forgot that the drag racers seem to like the T-76.

 

If you run the numbers, the T66 is good for roughly 650hp.

 

At what?
25psi???


-Ted

 

I'm not quite sure what kind of numbers you are running, but gauge pressure doesn't really have much to do with the equation.

This website contains much of the calculation process, but it does have some minor math errors:
http://www.gnttype.org/techarea/turbo/turboflow.html

 

i've been trying to figure out a turbo for the past month also. my goals aren't too lofty 20b wise(500-600rwhp). i would like the turbo to spool like the apex rx6 does on a two rotor. i've read many times that the t-66 is too small, especially since i have a "healthy streetport." but it might fit my needs, on the other hand i dont want it to burn up either. red-rx7 is kind of a special case, he has MUCH more than just a big street port in that setup. i'm also looking into the gt42r, using a 1.15 exhaust a/r. not sure how that will do though, still trying to figure it out.

 

I heard from a few people here in Japan that the greddy t88 is a perfect match for the 20b with stock ports. I didn't ask what model though. Mine is the 34d. I think the t88 has a 72m compressor wheel.

-Destin

 

Those are all old setups, Im sure most have upgraded now, I have the T66 off Garys drag car & will be quickly upgrading it also...

 

Hmm...what do you use as a displacement value?

Did I miss something - I can't find the power output estimate?
BSFC?


-Ted

 

Oh, sorry about that. Yes, I forgot that website doesn't go into the power estimate portion. I use my own calculations, but it is easier for me to link that website than to take the time to explain everything in a forum post. Basically, I take the airflow rate and multiply it by the estimated AFR to yield the fuel flow rate. Then, the fuel flow rate is multiplied by the estimated BSFC to estimate the hp. The calculation can be done for each rpm point by using the calculations on that website, or you can just use the turbo's maximum airflow rating to estimate the max hp potential of the turbocharger and reverse-engineer the pressure ratio and engine rpm required to make that hp level. Granted, this will yield the estimated hp potential of the compressor, and not the turbine or engine, but it's still a useful estimate IMO. You can take engine efficiency, intercooling, system pressure loss, or other factors into account as needed.

The rotary engine's rated displacement needs to be doubled for use in the 4-stroke piston engine formulas. This is because of the /2 or 0.5 multiplier used in the equation to account for the 4-stroke piston engine's problem of only firing half of its rated displacement per output shaft revolution. You could also remove the /2 or 0.5 multiplier, but most people find it easier just to double the rotary engine's displacement.

 

I typically use 2.5l to 3.0l 6-cylinder engine displacement with a BSFC of 0.60.
I'm just wondering what you use?


-Ted

 

Sure, you could use those numbers. The nice thing about equations is that you can use whatever numbers you like.

I use somewhere around 85%-100% Ev (which would equate to 1.668L to 1.962L for a 20B), and around 0.45 to .65 BSFC. <shrug>