13bmaniac

iTrader: (5)

hello im running my t-78 at 14.8 psi and is generating 442hp n my street ported engine, but im thinking on turning the boost a litle bit so i can achieve the goal of 480 hp i have the suporting mods to do it such as good fuel 850cc 1600 dual walbros twin power etc, and here in my country the gas we have is 95 octane unleaded so i dont know if i will be safe to do it or will be a great risk to my engine.

thanks

dhahlen

iTrader: (5)

Its all about the tune.

I wouldn't push over 15psi on 91 octane, so you figure 95 octane and 18psi may be safe.

THen again.. it's all about the tune. Be careful, too much boost can cost you an engine.

A good safeguard is water injection or alcohol injection. I'm comfortable doing 21psi with methanol and 91 octane.

Boston94FD

Ok I have a funny question for you, how's your gas mileage?

rynberg

How is your octane rated? If that is 95 RON, that is the equivalent of 92 or so in the US. I think it would be unwise to run 18 psi on that gas. You are too close to the edge. Water injection might make it safer....but I would run better gas.

Turblown

iTrader: (12)

What does your ign curve look like, and what about your afr tune. I've personally ran much more than that on 91 octane here, w/o w/a injection however the adv was backed way off...

Nuvolari

iTrader: (4)

Mix some race gas, or try some octane boost. That will get you up a few octane points without the expense of running full race gas. But 18psi is pushing it on 91 octane

13bmaniac

iTrader: (5)

we dont considerer much here the gas mileage since filling the tank full with 95 unleaded gas cost me only 1.75$. is not big deal this is the only country that a gallon of water is more expensive than a gallon o fuel.
i dont know what tipe of gas is refering to the octane rated.
my tuning is very conservative refering the the afr ratios considering that is between the 12.5 and high 11 under boost.
i dont know what you mean with ignition curve ,im running the hks twin power with new plugs on the way but im considering upgrading completely my ignition set up(coils, msd boxes etc)
and yes i think i should buy a water methanol injection sistem.

charlies7

iTrader: (4)

i would think being conservative would be 10.5 under boost for the afr....

dhahlen

iTrader: (5)

i agree

13bmaniac

iTrader: (5)

well thats a thought to keep in mind whe the car is on the dyno thanks guys,but you think that even at those afr i can run safetely at those psi numbers?

thanks

rynberg

Jesus, you think 12.5 to high 11s is conservative under boost???? If you don't know anything about your timing...it's probably too advanced. Given your AFRs, your gas must really be 95 octane or you would have probably blown the motor by now.

BDC

It's not all about the tune guys as tuning can only address so much. The tuning, much like everything else, is one part of a much larger and more complex system that must be well designed and balanced. The thing that I tell people repeatedly is that no tune in the world can cover up or gloss over the use of bad fuel. In our cases with the RE, we are pushing too much on too inferior and too volatile of a fuel in our desire to make power (the use of pump gas). Sure, we may be able to run 15 or 17psi on pump fuel for short bursts or even for a few to several months, but we're so close to the edge that we're practically inviting disaster to occur. One little thing such as a raise in ambient temperature or a mishap of bad gas at the station can equal engine damage and a downed car. No amount of spark retard can compensate for using too "hot" of a fuel in a combustion chamber that is already potentially several hundred degrees hotter than a piston engine. 13bmaniac, I feel that 18psi is pushing it on 95 octane. It may work for awhile, but if it ever blows up, the cause will be autoignition of the fuel in the compression stroke due to chamber temps being too high.

Use the right gas, guys.

B

BDC

That's too rich. There's no reason to run in the 10's on any setup, even with pump gas. Stay in the 11's, stretch out the limits of the injector in the setup, and alleviate a bit more power in the process.

B

13bmaniac

iTrader: (5)

thats the same think my tuner told me theres no reason why to stay in the 10 afr well at least been around 11.8 for me works very fine if been racing the car now for almost 5 months at 15 psi, my car is not a daily drive i just used the car on weekends and just race it 1 time every 15 days or so do a few passes and go home again.
theres only one place that sell vp race gas and is to much expensive, i dont know if the airplane gas will do the trick because we can get it ,few people use in here the airplane gas as race gas and work fine but none of them in a rotary engine

GUITARJUNKIE28

yea, but the stock turbo isn't even in the same world as a t78. it's about airflow, NOT psi!

dubulup

Anyone care to explain how airflow would be different at the same measured PSI...obviously PSI is relavent, since we don't monitor airflow.

and please don't try to make a comparison about my shop air compressor moving 8cfm @ 90 psi. We are talking about at least 2.75" IC piping

GUITARJUNKIE28

why don't you just take a few classes at your local jc since you couldn't understand it when i explained it to you 3 times? you might learn something.

or maybe you could search the forum. the a-spec guy made a nice thread about how compressor size counts.

dubulup

Counts as far as moving the right amount of air at the right rpm...how else does it count?

3x you explained this to me must have me confused with someone else.

GUITARJUNKIE28

i help guys out every day.

when you didn't understand my answer, you jumped up on your high horse and said i didn't explain it right. what you could have said was you didn't understand, and can you pleas explain it a different way.

i would have said no problem bro, here's another way to lok at it...

instead, you're saying i'm dumb because i can't figure out a way to make you understand the concept. here's the answer: stop smoking pot, open a book.

matty

just about 450 @15psi...thats pretty good!

rarson

Seriously???

Compressor maps are 3-dimensional.

GUITARJUNKIE28

no, we calculate airflow by monitoring everything else.

http://scienceworld.wolfram.com/phys...ealGasLaw.html

to start your studies...

dhahlen

iTrader: (5)

oooooooh Dave.. I love it when you get all nerdy on me.

GUITARJUNKIE28

i told you i wasn't entirely uneducated--only underfunded to finish my education.

dubulup

my questions was about compressors...maybe I wasn't clear when I posted in this thread, I apologize for that. Two turbo chargers, same piping (intake/exhaust)...why will one move more air than the other at the same PSI rating? My thinking is, efficiency of charge (compressor) and exhaust backpressure (turbine)

Then I have GUITARHERO telling me an air compressor won't move as much air as a turbo...You're right man, that was a big help!! Thanks bro, its all clear now.

yes, I'm serious. Is it due to efficiency and backpressure, or something magical that will pop out at me by staring at a compressor map, as GUITARHERO suggested to me.

the 3rd dimension being efficiency...pretty much a given, if you are going to look at a map.


EXAMPLE from Sean @ A-spec
stock 13B at 15psi
1)Pressure ratio 2.0
2)VE(volumetric efficiency) 90%
3)Displacement 2.6

Once you know those things you can plot a point on the compressor map and see where you land simply by adding RPM into the equation.

Displacement x RPM x VE x PR / 5660 = CFM

2.6L x 8500RPM x 90%VE x 2.0PR /5660 = 702.82 CFM or 49.25 lb/min



clearly running 1 bar of boost as RPM increases you will pass just on top of the most efficient island



running 1 bar of boost you are mainly in the most efficient island...however, this turbo isn't even awake at this boost level.

only reason I believe the T70 "compressor wheel" will make more power at this boost level is a more efficient charge. And when you look the turbochargers as a whole, I'm sure the larger turbine housing relieves back pressure in the exhaust.