Are there any drawbacks to running two quick spooling BB turbos in parallel? Why don't we see more of them on RX-7's? It seams like a good idea to me to have one turbo per exhaust port.

 

Price - Expensive
Install - Pain in the ***
Benefit - nothing impressive

 

And added complexity (more stuff to break) One of the best things about going single is it gets rid of the stupidly complex sequential system.

 

Aren’t the benefits faster spool up time?

 

Why go custom twin, when you can go single?

 

custom twin would be a plumbing nightmare...I'm not going to be the first to do this...

 

I believe ASP did it several years ago. I think Kevin sold the car to Dana in MA. I'm not sure what he has done with it since then.

 

no, 2 small turbos are like one medium sized turbos. You would benefit more from a duall ball bearing T4 turbo IMO...

 

Running two small turbo's means overcoming inertia on two instead of one turbo. It may mean more flow at low RPM because of the flow difference and efficiency of one large turbo. The difference's won't be that great because of the inertia issue. It's a trade off w/o much benefit and much more complexity and cost. You may do it just to be different, though!

 

Dana still has the car and its running beautifully, I also have a former ASP car

 

the benifits do not outweigh the pain in the *** and expense of the setup

 

exactly, although if you have th eloot to blow the by all means do and and try something different.

 

 

Gmonsen,
I agree with you about the different thing. I don't understand it. Anyway, I would go T-78 in a heartbeat, if you could keep the air pump. I think this is what makes some people think about using the twins. Emissions are getting more strict every year. Is it possible to pass emissions with a T-78?
Jim

 

i agree with going big single but if you would like to be diffrent a custom set of parallel twin t3/t4 hybrid bb turbos would offer some big power for a twin setup

 

What would that lag, and top end be equivalent to when running a set of t3/t4 bb in parallel?

 

i think cough cough cough ted falls into this catergory with is Bridge porting and hybrid turbo debates...

 

how could you say that the benefits of a twin turbo set up are negligable? I'm not talking sequential twin, I'm talking true twin Turbo. There are huge gains to be had from twins. You get double the CFM. there is a series 1 in australia with an S4 engine using 2 factory S4 turbos. it made 297kw at the wheels, which is something like 400rwhp. thats from 2 stock s4 turbos at 15psi!!!!!!!!! Imagine two higher flowing turbos. I've got single turbo on my car right now, but plan on upgrading to twin setup in the future.

 

Gordon -

I've got a lot of respect for your opinions as you've added quite a large body of work to the forum and the Big List, but there are mitigating circumstances concerning this 'true twin' issue that you have the liberty to ignore, but we in Kalifornia cannot. In the pursuit of big power we can't go single because we have a visual and emissions test, and a single is an automatic failure on the visual. Rotaries are being targeted and directed to 'test only' facilities and are under quite a bit of scrutiny. Basically you cannot street a single turbo 3rd gen in this state without serious 'help' from a testing station.

Please take a look at the following thread where I"ve been speaking about my true twin, non-sequential setup. I now have 200 miles on the new motor and turbos so I'm still in the break-in period. However, I'm convinced that this setup will be able to perform similarly to your T-78 and still be reliable. I plan on providing dyno numbers in the next month to prove/disprove this belief.

Some of the earlier comments are certainly true - this project has been complex and costly, but I'm relatively certain that you have also spent considerable sums in your pursuit of speed (on your RX and other toys I've heard you have :-)

I invite your comments.

Beast

https://www.rx7club.com/forum/showth...threadid=91272

 

Gmonson, that's a good idea. I was toying with it, but was worried about the "lean" thing. Thanks.
Jim

 

I'm suprised that one of the tuners in CA hasn't developed a CARB approved single turbo kit for the FD's. A kit that keeps the air pump with some good tuning on a PFC should do the job.

I also personally think that single turbo is the only way to go. I don't particularly care to be that different... owning an FD is different enough. Also agree with the statement that those people considering a twin turbo upgrade should drive a well sorted out single before committing themselves.

GMonsen... are you running any of the other emmissions stuff? I may have to resort to the leaning and no boost method to try to pass emmissions in the near future.

 

Im going to be running twin GT28 .64 on FC. should spool fast and still be efficent up to boost 1.8 bar

 

Well, Gordon, for only reading my post(s) once, you really restated my goals succinctly. You're spot-on regarding cost, power goals, boost levels to produce that power, the plumbing aspects, etc. You're also right in the fact that a single turbo would probably pass at normal California emission stations, but rotaries are being directed to 'test only' stations that have better trained personnel. Those folks might also not catch it, but all it takes is one fairly informed individual to catch you, then you're in their computer system and sunk. God I hate governmental policies that are vieled as 'environmental protection' when all they really are is a form of taxation.

For more info on what I've done to date, take a look at the Big List starting around May 20th. I'm trying to cross-post but there just are not enough hours in the day.

250 miles to go before a visit to the dyno....

Beast

 

i think hks has carb legal turbo kits for the fd, they do for the fc. the apexi kit now works with the air pump too

mike

 

Cross posted from other thread:

https://www.rx7club.com/forum/showth...114#post941114

I hope I can come up with comparable numbers to you single guys to stir up some controversy.....I'm not going to say anything until I have a dyno sheet to back it up.


Beast