maddmatt02

ok, I was going over the "selecting what size turbo" thread.

and I was doing fine at first.

2254(F23A1) = 137.5CID
at 85% VE thats 219.8 CFM

I was thinking about 12lbs of boost which gives me a pressure ratio of 1.82:1

now, the temp rise has me stuck.
heres a quote from that thread. and I have two questions, 1.) when he assumes an inlet temp of 75 degrees, this is to the turbo right? so since its around mid 90's at its highest here in the summer, id use the worst case scenario of 95?

2.)how does this math work. "535 (24.7 ÷ 14.7)0.283 = 620 °R"

24.7/14.7=1.68 and ive always been taught to do whats in the parenthesis first(at least I think so. lol), so thats how I started. then multiplied by .283 and then by 535. and I do not come up with 620. then I thought about how 5(10/1) would be (50/5)(not sure if distributive property works when its multiplication and division in the parenthesis) but when I distribute the 5 and get 50/5, I get 10, which is what 10/1 was in the parenthesis. so the number outside the parenthesis is pointless in this case and obvioulsy isnt the way to go.

and until I can figure out how to make this guys math right, no point in doing it with my numbers because I dont know how to do the formula.


T2 = T1 (P2 ÷ P1)0.283

(i deleted some of the calculations used to get here)

The formula will now look like this:

T2 = 535 (24.7 ÷ 14.7)0.283 = 620 °R


anyways, I am thinking of boosting my 01 accord ex coupe. I will be running a OBD1(not sure what ecu, but since its basically all customizable, does it matter what ecu it is as long as its an OBD1 VTEC ECU?) conversion and S300, so tunings not a problem. I am going to make my own manifold, downpipe, probably charge pipes as well. and will be running a FMIC.

I have a IHI RHB5 and from what Ive read the internal WG is set at 8lbs. found a rebuild kit on ebay for it for 70 bucks. is this turbo good for anymore if I disabled the internal and ran an external?

with a good tune is 12lbs safe for a 100% stock block? is more safe?

txdohczc

if thats the turbo from a ford probe then if i were you i would get a new one that would be way to small for that car you would hit full boost by 2,500rpm and run it out of breath by 6,000rpm. also hondata sucks just use crome its free and its better. seems like you got along way to go before you understand what it is going to take to turbo that car. either way you need a bigger turbo

maddmatt02

why does hondata suck? by the time I upgrade to chrome pro, and get the necessary software/cables to datalog and upload new tunes, Im in the 500's again?

I am not going to get it perfect out on the back roads sure, but I can get it damn close before I take it to the dyno so I dont have to pay them all day at 80+/hr to tune my car.

and I was trying to find out if this turbo was enough on my own, but couldnt get past that calculation. and still cant.

and you are right, I do need to learn a few things before I boost this car. but in reality, you have no idea what I know or dont know. and there is noone who knows it all, thats why Im trying to learn what I dont.

I have done auto to manual swaps, D to B swaps, rebuilt B series, rebuilt A/C VW's, built engine harnesses, swapped vehicle harnesses, fabricated exhaust systems, etc...

I know it doesnt really relate to FI, point is, I can pretty much learn to do, and then do, what I want to.

if someone can just help me out with this formula, I can go on quietly doing this by myself.

txdohczc

by looking at these two questions i can tell you dont know enough.
your trying to learn and thats cool but part of learning is listening to what people have as an answer to your question. why disable the internal w/g when you can easily get 12psi from a boost controller? and if you are going to spend 500 on tuning kit then just go with crome pro its better than ant hondata system. and yes 12lbs should be safe with a good tune and premium gas

maddmatt02

well, isnt external wastegate better anyways because it can be of any size, and doesnt need to try and fit inside the turbo housing, therefore it is much better at moderating boost levels.

and I know it isnt really the boost pressure that determines the safe level, it is the combustion pressure(power) created in the cylinder that there is a "safe" level of. but almost nowhere do people refer to it as this, most people just say "yeah, a B18b can handle xx pounds of boost but a B18C1 can only handle x pounds. they dont refer to volume of air at that pressure.

see, Im not a complete idiot. lol

Id still like to know what steps will make 535 (24.7 ÷ 14.7)0.283 = 620
because I cant find a way to solve that equation and get that solution, and until I do, that page will be of no help to me to find the right size turbo.

and I guess I took it wrong, only things i gathered basically was "hondata sucks" "get a bigger turbo" and "you have no idea what youre talking about and have a long ways to go before you do".

reading it again, I can see that it probably wasnt meant like this, maybe its that time of the month...

txdohczc

its not psi that ruins engines its detonation and horsepower.the b18b will be able to handle more psi because because of lower compression ratio compared to the b18c the higher compression ratio has more heat in it which would cause detonation. the reason why i say stick with an internal wastegate is becuase its seems to me your doing a low budget build with a small turbo at low boost pressures so there is no need to go with an external. it would be a waste of money and just more ---- to have to do for a not really any pay off. and to answer that whole calculations question i really have no idea to be honest

maddmatt02

damnit, everytime I try and make myself sound smart, I fail I guess. lol.

I know detonation is a very harmful occurance inside the engine, but it isnt what limits the safe point of the block, sure, you have to have a good tune with no detonation for it to be safe though. and I know higher compression can cause more heat and lead to easier detonation, just like too much advance can cause detonation.

and I know the differences between the b/C/C1/C5 (well, not them every difference, but where they come from and the hp/tq/cr's etc. for the most part)

alright, internal it is then, I figured it would be easier, just not sure if the ext. would be better. guess not for my build.

what turbos would you think of off the top of your head?

thanks for the help by the way.

txdohczc

if you want a cheap oem turbo get the turbo from an rx-7 turbo 2. those are a good size and ~$100 then all you need is to get an adapter for it to fit a t3 manifold