Can the 20b oem turbos be modified to the stage 3 bnr specs ?

 

Yes, they can be. I spoke to Brain about it, actually. If I remember correctly, it was going to be around $2200. I had two issues with it. First, it's a complete pain in the *** to goof around with the stock manifold, etc if the engine is in the car. I have an exhaust leak that happened from the last time I pulled them. Secondly, although I have no doubt they will put out a good amount of power, he has no dyno numbers to back it up.

I'm pretty sure that if RETed replies to this, he'll mention the fact that the twins need to be tossed in the nearest river/canyon/what have you. Personally, I have nothing against hybrid setups, but in this case, for roughly the same amount of money I could make:

1) More power
2) Less heat
3) Easier to work on and get to.

Hope this helps!

Reese

 

Thanks for the reply, agree with your comment about working on the turbos when in the car ,looks like major pain in the ***. Motor is in the car at the moment but will be coming out soon and definatly want to upgrade them. Thanks.

 

Hey RX7TT20B.

I have upgraded them and have pictures of them if you want to see. Shoot me an email and you can check them out. They look beautiful. By the way you can modify them and make more power and have better reliability.

Bryan@BNR
www.bnrturbos.com
205 640 1193

 

Thanks for your reply Bryan , have sent you an email .

 

modify them how? i spoke with you awhile ago about the possibility of you modifying my twins, but after some thought a few things did not sit so well with me.

first of all a 3->1->2 setup (which id assume would be the case if you ripped out all the flapper doors etc for the sequential control) is rather inefficient.

secondly, the turbos are not balanced... one is a (relatively) huge ht-15, and the other is a teeeny tiny ht-10. how are the exaust gasses proportionally distributed to each turbo (or do they even need to be?). id think that one of the turbos would be under worked while the other was over worked?? maybe this is not the case? IIRC they are are unbalanced specifically for sequential operation to overcome the 3->1->2 dillema that you would run into w/ 3 rotors. IIRC, mazda solved this by piping all 3 rotors worth of exhaust gasses exclusively to the large primary untill transition, at which time a flap closes and splits off the first 2 rotors exhaust just for the ht-15, while the rear rotors exhaust is directed to the tiny ht-10. i believe the ht-10 (running just one rotor) was chosen to complement the flow characteristics of the ht-15 with 2 rotors worth of exhaust gasses. when all of the sequential stuff is defeated you are left with a very weird situation.

third, it would seem that running the turbos non-seq would cause a good amount of additional lag (one of the only downsides to going single...besides the cost). is the lag time less than with a sensibly sized single setup? also speaking of cost, how much would we be talking about for the modifications (whatever those might be)?

basically what im trying to ascertain is... if i were to stick with the twins and have you modify them, what would be the positive sides to this route as compared to a single turbo?

bryan, i would love to stick with my twins, but i have a few reservaions about doing so. do my concerns have any warrant?? if you have a sec, maybe you could touch on the points i talked about. also, if you could post some pics (or email them to me and i can host/post them) that would be great. my email is firewire5@hotmail.com thank you very much, heath

 

Rotor motor most people seem to run the turbos non-sequentialy as they dont use the oem ecu which seem to work ok from what i have read. My set up they will retain sequential operation as i use the original ecu.

 

Good luck with the stock ecu. I heard it's a huge pain in the ***.

-Destin

 

Sillbeer wiring has allready been done,not as hard as most people think.

 

As long as you limit boost, the twin turbo's are great for street driving, they spool quickly & the throttle response is excellent. Holding boost up high certainly strains them though.

Mind you, I have the REAL THING to drive so can't comment on after market applications like an install into a series-6 (92-95) RX-7.

REgards

 

I've recently tore down 2 x 20Bs and got a good look at the set up. My opinion, if you take of the restictors on the exhaust ports, it will probably spool the twin even better... Maybe too quick??

 

are teh restrictors in place for fuel economy or what? and if you swap the jackets for FD ones do oyu have to port match everything past teh jackets? i didnt know they were THAT restrictive (i havent started tearing my motor apart yet). -heath

 

Mazda installed the restrictors to limit NOISE output. The Cosmo was sold as a top level luxury tourer & an ultra quiet engine was important, hence the restrictors.

When my 20B engines finally goes, the exhaust sleeves will certainly be getting swapped for the RX-7 types.........

 

Your still running sequential right? I always wondered how fast the 20b twins spooled sequentially when compared to the Fd. Could you answer a couple questions for me? On my stock Fd my primary gets 10 psi by 2,600 rpm. What rpm do you get full boost by on the primary? Also at what rpm does your transition take place? Lastly how many ft lbs of torque does a stock 20b make on the primary turbo before transition? I'm asking this to see how much more low end a stock 20b Cosmo has when compared to an stock Fd.

 

do you still have them running in sequential mode? if so then i can imagine its a nice setup. however... when people convert them to use in FD, or FC setups etc... they are NOT used in sequential mode. this provides a strange situation where all exhaust from all 3 rotors is split between the differently sized turbos... which i would assume is far from optimal.

 

can anyone touch on a few of the points i made?? is my logic off in my assumptions about the turbos? what do you guys think?? id love to know -heath

 

Wow thats a bunch of questions! Just call me and we will duscuss it over the phone! lol

Bryan@BNR
205 640 1193
www.bnrturbos.com