I am wondering there is data out there for any possible turbo we go look for. However, in comparing the output or flow rates of the twins to a single there doesn't seem to be much. So what kind of a single really matches up to the stock setup?

 

I think they're around 42lb/min.

 

At what kind of pressures.

Because isn't 42lbs/min like a GT35R @ 15psi

 

there arent any maps out officially for them. I think the most you can do is just compare power output. There are a couple guys making 400whp on them. Wouldn't that be around 42lb/min? I have read this a few times, it sounds legitimate.

 

This is the closest you'll find:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/compressor-map-gurus-ive-got-stock-twins-map-505850/

 

Thanks,

If only they would have had pressure ratios on the left indicated it would have been perfect. What good is a diagram without scale damn these guys.

 

the above is purported to be the twins compressor map. assuming around 380 rw rotary hp that would peg max pounds per minute at about 25 pounds.

given that the above is simply the COMPRESSOR output and given that the stock manifolding absolutely sucks from a flow and thermal aspect it might be best to give a tad discount toreal world output on the FD.

the bottom line is the compressor wheels start to cavitate and superheat the charge air around 15 psi so you will be getting less oxygen molecules into the motor per psi and make less hp. you will also be destroying the turbos.

all 15 psi readings on the boost gauge are not created equal. it is all about the number of oxygen molecules not necessarily the pressure.

add that to the fact you have 22 pounds of cast iron bolted to your aluminum housings and you have the makings of baking your engine.

cast iron is close to the top of the list for retaining heat and aluminum is similarly situated at near the top of the list for accepting heat. the rotor housings are the most critical part of the engine and the stock manifolding is diabolically designed to cook your housings long after you turn off your motor.

OTOH, the flanges on a single turbo weigh 4 pounds and contibute next to nothing in the baking engine dept.

add this factor to the greatly increased thermal efficiency of a single manifold and you have a win win.

my single turbo system, well actually it is two Garrett TO4s, not one, features backpressure at 20 psi boost of 21 psi preturbo... think of all the heat getting out of the motor. it is the opposite of the stock setup. backpressure pollutes the next incoming air and overheats the motor.

my motor hasn't been out of my car in 4 years, has over 100 2000-8000 4th gear dyno pulls on it, made 498 hp (on 93 octane pump and alcohol) at 20 psi last thursday and idles at 17-18 inches vacuum.

build it right and you'll be a happy guy.

are you getting the idea i hate the stock factory turbo setup?

howard coleman

 

I hate the stock twin setup as well. Right now I am having this annoying issue, it boosts fine sometimes and other times I am seeing 0.14-0.2bar.

In transition it flutters and sometimes when it is not boost I get off throttle and hear compressor surge, something I have never heard on a twin turbo fd.

The reason I ask this question is, I am looking to see what would be comparable in a single turbo setup so as to swap out the twins for a single that wouldn't require drastic fuel changes over twins such as to keep a relatively decent fuel economy.

 

http://www.rx7store.net/product_p/apexi%20rx6.htm

 

"to keep a relatively decent fuel economy."

fuel mileage is a function of work done and VE. as such there should be no significant difference between the stock setup and a single setup if properly tuned. i get 21 mpg on the highway.

hc

 

Howard, I definitively need to meet you in person, maybe next year at Gordon M's if there is another meet to Chris C's memory.

What I meant by relative fuel economy was I know some single people getting more like 12mpg highway or something like that, I would like it to be in the range you have mentioned. However, I do plan on using AUX injection as you do which to my understanding reduces the amount of excess fuel needed (excess fuel being used to cool the engine).

About that graph so from your calculations flow should be about 25lb/min, I think I remember reading your twin setup was 48lb/min or something close to that?

 

as i said, the two factors for fuel economy are work done.... and work done is constant since in both cases it is your FD.... and VE. VE has nothing to do w the turbo system and relates to the engine...

the primary factor is TUNE. bad tune 10 mpg. good tune 21 MPG.

none of this relates to under boost. under boost i want to use as much fuel as i can as it makes power. i do not care about mileage in boost.

my alcohol works only under boost. i am removing about 20 points of 93 pump IDC and replacing it w alcohol.

my turbos flow around 42-44 pounds per minute, each. max boost will be 27 psi where they will make as much air as a GT42 at 39 psi.

hc

 

So then I need to lean out my cruise and idle cells.