boosted zenki

Whats up guys!

Just picked up my first Mazda the other day and thought i would jump on and say hello. Im a long time Nissan guy and had planed to use this as the DD while my coupe is under the knife but im starting to think this might be the next project when my s13 is all said and done!

a little back story, I blew the motor in the coupe up a few weeks ago and decided it was time to stop playing around and go big. after a few days i finally decided to sell the wheels off the coupe and pick up a friends miata as i would rather have a driving car then a blown up s13 with some shiny wheels. the car is in pretty good shape, needs a few small things like a driveshaft, tires, and new speakers but that's all pretty easy. As of right now my old plans are to lower it a little more ( the rear is already lower then the front and change out the ds and maybe get a hardtop.


Anyways a little about the car.

1991 1.6L B6
180k miles
d2 coilovers
Konig candy 15x8 polished wheels
APR carbon fiber mirrors
Racing Beat intake and catback

RedTurboMiata

Welcome to mfz, nice looking ride you got there. How about some pics of the s13 you keep mentioning?

boosted zenki

The 240sx isnt anything real special as of right now, i got it bone stock about a year ago with the sohc KA in it and its been through at least 3 stages of adding parts, taking them off and replacing them with better stuff I did a dohc swap about 6 months ago and the water pump finally went out on the way back from the beach last month and warped the head and dropped a valve.

Right now the list looks a little something like this.


1989 two tone 240sx
210xxx on the body
all OEM Silvia front

megan track coils.
s14 5 lug hubs
s14 LCAS's front and rear
50mm front and 60mm rear extended studs
mog rca ball joints
pretty much all the arms are aftermarket
white line sway bars
Q45 fronts and s14 rear bb kit.

DOHC swap
OBX header
isis rad with fans
def e-fan control
3" test pipe with stock exhaust
arp main and head studs.


loads of other stuff i just cant think of right now im sure.

i have had more wheels then i care to think about so i wont list those.














and the only pic i have of the motor for some odd reason.




Plan is to build the hell out of the KA and slap a gt30 on it, wire tuck, new coils, wheels, and paint.

djshoester

Very nice =)
Loving the Miata that you got!
Also best of luck on rebuilding your s13, what did you do to it that blew the motor?

sixshooter

Welcome to this easygoing forum. Miata needs moar turbo.

boosted zenki

Maybe one day... I drove a 94 with the flying miata ( i think thats what its called??) on like 14psi tuned for e85 and really wasn't all that impressed compared to the sr's and ka-t's on 7-10psi That i drive all the time.

Maybe it was just a bad tune??

sixshooter

Little bitty turbo at 14psi big turbo at 14psi, or even 7 psi. Power depends on CFM of airflow, not pounds of backpressure in the intake tract. Contrary to popular understanding, boost pressure is a measure of inefficiency of flow of the system, not volume or mass of air flowing through it.

djshoester

I did not know this! so I did some digging first haha
"15 psi is 15 psi no matter what size your turbo is. Some turbos (small ones) can produce 15 psi of pressure from 2.3k to 4k rpms where after 4k it starts to run out of its "efficiancy range" and than your just blowing really hot air(bad) and you haven't maxed out your engine. A big turbo will spool up and create 15psi of boost at say 4k all the way to red line, efficiantly(meaning not really hot air) or even 20 psi of boost because bigger turbos need more exhaust power to spin a bigger compressor. bigger compressor, bigger pump capaple of producing higher boost."

Taken from this discussion :
small turbo vs. big turbo. which makes more power? (2nd try) - RX7Club.com

flying_solo

iTrader: (1)

Lots of awesome stuff on RX7Club.com. I've learned enough to really screw up my FD

sixshooter

Compare these two compressor maps carefully. The concentric curves (ovals) delineate changes in efficiency, or the ability to move and compress air without turning the mechanical energy into heat. Higher efficiency means more power and less heat waste are created. Operationally, you ideally want to function in the middle island of greatest efficiency, but our engines are not constant speed so they trace a line through the graph during operation.

At a pressure ratio of 2, which is roughly 15 psi, the greatest efficiency that can be achieved by the 2554 is ~70% and most of that operational area is between 17 and 24 lbs/min of airflow. Remember, airflow is what makes horsepower because air mixed with fuel makes horses. Twice as much air equals twice as much fuel equals twice (roughly) as much power. If we look at the second map, it has a sizable island of 76% efficiency at the pressure ratio of 2 line, which is considerably higher efficiency. And it maintains 75% efficiency or greater at an airflow of around 23 to 32 lbs/minute of airflow, a much greater amount of air.

So we are seeing 25% more airflow at the same pressure with 7% greater efficiency. That is a win-win. It also means the air volume that is generated is cooler which is also beneficial to make more power in your engine. The same 2871 is capable of maintaining its 75%+ efficiency all the way up to ~39 lbs/min of airflow and do it at up to 26 psi. Maintaining efficiency as the pressure and flow gets higher is where the engineering really makes the difference.

Digging into the big versus little comparison, you can see that the 2554 at a PR of 2 (15psi) is hitting 24 lbs/min maxed out in the 70% efficiency range, but at the same efficiency level the 2871 can hit 24 lbs/min at a PR of 1.5 or about 7.5 psi -- Same airflow, same efficiency level, half the pressure.

So we have a bigger turbo at half the pressure making same horsepower. This is why guys who know a thing or two think other guys are idiots when they ask "How much boost you runnin'?" without knowing how large the turbo is. Knowing how much boost someone is running without knowing anything else literally tells you nothing.

Does this help at all?