power hungry

Just wondering what size wastegates are you guys running. I have a turbonetics racegate from a previous project but dont know if this will work well on a 20b. I think the wastegate is about a 48mm

patman

iTrader: (3)

should be fine

Turbo 3

iTrader: (3)

I have a GT60mm but yours should be fine with a 48mm.

94RHDFD

iTrader: (3)

I have a HKS 50mm racegate

power hungry

I guess I will give it a try. Hopefully all will be well.
Thanks

RETed

That's already wrong.
Stay away from those piece of ****, poor excuse for a wastegate...
I think the Racegate is a claimed 46mm.


-Ted

sillbeer

I have the sard type J 60mm.

-Destin

power hungry

I wasnt stating fact I was just guessing. I just looked it up and its 45mm so I will just use it for my domestic project and buy something else. Ive had it a couple years with no problems on my supra but maybe they are ****. hasnt failed me yet.

CCarlisi

It really depends on what the minimum amount of boost is that you want to run. Tial said their 44mm is too small to run under 10psi with a 102mm GT42R and seperately they told me their 44mm flows better than their 46mm.

RETed

I've seen literally dozens fail on turbo'd Hondas.

Be careful when you start comparing piston versus rotary engines in terms of exhaust output.
Your 600hp Supra makes about the same amount of exhaust gases as a 400hp rotary.
Your 900hp Supra makes about the same amount of exhaust gases as a 600hp rotary.

Do you run a single Turbonetics Racegate on a 900hp Supra?
That's about as equivalent to a mild 20B...


-Ted

patman

iTrader: (3)

Ted, are you trying to say that the BSFC of a supra is 2/3 that of a rx7?

the minute you show me a supra with a bsfc of .4, i'll be extremely damn impressed.

i wont argue with you about the quality of turbonetics, because i dont know, but a decent 45mm wastegate should be enough unless he wants to run less than 10psi.

RETed

It's a little more complicated than to base it solely on BSFC.
If it were solely based on BSFC, then I bet it would be WAY off.
The thread is based more on the production of exhaust gases than the power output (per unit gasoline consumed = BSFC); if we could calculate exhaust gas production and factor in engine efficiency, we would get a lot better numbers!

Those are my rough estimations on what my experience has taught me.


-Ted

patman

iTrader: (3)

where do these exhaust gasses come from?
for any open system, such as an engine, the sum of mass flow rates in equals the mass flow rate out. in other words, the massflow of fuel in + the massflow of air in = the massflow of exhaust out. assuming that both engines are running similar a/f ratios, the only way you can get more exhaust out for the same horsepower is by having a higher bsfc, hence more air and more fuel coming in.

i suppose it may have something to do with the blow-by on the rotary, so that there is more energy left in the gasses coming out, making it seem like there is more actual gas there

pat

calculon

iTrader: (29)

it's not mass flow that spins a turbo and creates pressure. . .one has to take into account the efficiency of the burn leading to the expansion of the gas. . .the egt (since P=nRT/V). . .really, the volumetric flow rate is a better measure since it speaks moredirectly to the exhaust gas velocity and the area over which the flow is distributed. . .mass flow includes a density term, which as i said, is affected by the egt, the engine efficiency, incoming afr, etc.

patman

iTrader: (3)

changes in density are negligible if the mach number is <1. volumtric flowrate is therefore directly proportional to mass flowrate.

the efficiency of the burn is directly related to bsfc, since an inefficient burn uses more fuel to make the same power, which is what i was talking about in the first place.

pat

calculon

iTrader: (29)

changes in density are negligible for Mach less than one absolutely, but only for a single fluid. . .in this case, it's more complex since we have a binary fluid mixture. . .air and fuel. . .

because it is a binary system, a much more complicated navier-stokes equation results, one with a transcendental solution. . .one based on the density of each of the incoming charge's density. . .with are both individually constant (or atleast close enough that it's a safe assumption) but the overall fuel density (grams fuel per volume of incoming charge rather than grams of fuel per volume of fuel) is changing dramatically and very rapidly.

to be perfectly honest, i don't have a huge amount of practical experience, just that book learnin, which i could very well be wrong about as well ( i've only taken 2 classes in fluid flow and mass transfer) . . .

at any rate, if anyone is quite confident in their opinion on the matter, trust them more than me, i'm just going off of what i've learned so far

RETed

Dynamics of the rotary engine is significantly different than a piston engine.
The rotary uses impact of it's distinct exhaust gas pulses to "push" the turbo - this is one of the more significant differences.
Also, if you try and plug in the (exhaust) port timing, it will almost not run on a piston motor.
There have been thread on turbine wheel design about taking advantage of the impact characteristic of it's exhaust gas flow rather than assuming it's a consistent flow of (exhaust) gases as with piston engines.
Like I said in the beginning, the dynamics is a lot more complicated than that; it's a lot more complex than punching in air + fuel in versus exhaust gas out.

All that stuff you guys posted gave me a heachache. :P

I would be slightly worried if we're stuck with an HKS Race 50mm, GT 50mm, GT 60mm, Tial 46mm - I use these wastegates on big power 13B's.
In fact, I had a $1300 Tial "Race" 55mm at one time just for my 20B project, but have since changed the project to triples.
38mm of wastegate per rotor is okay.
Extrapolate that to x3, and you see why even a 60mm is borderline.

You still need to calculate wastegate *path* efficiency, as this is one of the points that a LOT of people on here are clueless on, but that's a whole 'nother story...

I tend to "overkill" my wastegate sizing and go way bigger than necessary.
I've seen too many projects get killed due to too-small a wastegate.

You're welcome to try a smaller wastegate size.
I was just trying to offer my experience and opinion - nothing more, nothing less.
Please report back to us with your findings!


-Ted

power hungry

Interesting thought. I havent built my manifold yet so i will have to see if I have the room for a triple wastegate setup. hopefully that phase of the project will start at the beginning of the new year.

sillbeer

Ted is also tossing around the idea of running triple 2835's to match the 3 wastegates. I was looking through one of my old hyper-rev's and there is mention of a 20b fd with 3 2835's. I beleive it was somewhere in the neighbor hood of 900hp. I would have to go through it again and see what wastegate setup there running.

-Destin