ok, say you are making 20 psi boost, is your exhaust backpressure going to be higher or lower than 20 psi. how is turbo efficiency calculated? i would say that the efficiency range of a turbo is when the exhaust backpressure is less than or equal to turbo boost.?? is this true? how does a larger turbine housing affect the efficiency range of that turbo? seems to me that it would lower exhaust backpressure at any given boost pressure and make the efficiency range of a turbo a lower boost number...???? am i way off, or did i just not make any sense or does anyone know the answers to these questions???

 

Your getting there.
Keep reading.
Answer to 1st question: typically higher.

 

turbo efficiency and compressor efficiency are two different things... you match the turbo compressor to the given air mass you need to move (horsepower) and the pressure ratio required (boost) to shove that mass in your little engine...

you then match the turbine housing to driving style etc...

smaller turbine side = better bottom end response and better overall efficiency at lower boost levels, but exhaust pressure can go over boost pressure easier

larger turbine side = slower spool up, but better efficiency at higher boost levels as exhaust pressure will be closer to boost pressure.

 

ok. i want 45-50 psi boost from mid to high rpm's w-o causing too much damage to the turbo, what turbo would this be and how much lag do ya'll think it would have? is anyone runnin 45-50 with a single turbo out there that would like to share which turbo you have?? by the way, this site is bad-***, i thought nobody would even try to answer this one, thanks a million

 

Here are two threads that will answer most of your questions, I think

https://www.dieseltruckresource.com/...rive+pressures

https://www.dieseltruckresource.com/...threadid=54886

Second thread deals specifically with Drive Pressures on a KSB-1 turbo, which in this set up are very good for a single turbo....for more info on those turbos, go here... https://www.dieseltruckresource.com/...threadid=45038

Do a search and you will find other threads as well...but these will get you headed in the right direction..information wise!

Without specifics on your truck can't give you specific answers...please fill in Signature (CP....Personal Profile) so we can better help!

Good Luck

RJ

 

you're gonna need a big single to run 45-50psi efficiently... can't find the thread right now, but someone on TDR said his B1 dynoed best at like 42psi or something like that...

the problem w/ a single that would be efficient in the 50psi range is that it isn't going to be efficient down low and you're going to be in surge at light throttle... take something like the USB... it runs like a raped ape up top, but cruising down the highway w/ no load, it'll surge like crazy...

my advice? if you're looking for good drivability w/ decent EGT control, the semi-affordable route is a B1 or HX40 or the like, keep the boost in the low 40's, and put some water/methanol injection on it... if you want to have your cake and eat it to, go with twins...

there is no magic bullet single... you gotta weigh your parameters and pick your poison... my HX40 is a little laggy, but it was cheap (one of my parameters! LOL!), and it helped out BIG TIME in the EGT department compared to the 35-12!! only problem is I cranked up the fuel even more, and now the pyro climbs just as fast... so my next logical step is twins...

only problem then is, once the twins are on, I'll be lookin' for more fuel to get that pyro needle swingin' like it used to

 

When does the cycle end? I have my HX40 and 370's. Going to twins soon,,,or want to, I have an extra turbo waiting lol, lets put it that way,,,already sunk a good down payment on a new truck into this one, when do I get to stop spending money and be satisfied? lol does it ever happen?

 

ok, i really like the sound of a methanol-water inject, what exactly does it do for the engine though. and would it help any if it were before instead of after the intercooler? i will fill out my profile with what i got so far, the motors in the machine shop now but i will keep it updated.

 

the water pulls heat out of the charge... it takes that heat energy and turns to steam... as a byproduct, the pistons, valves, and chamber face are kept nice and clean from the steam cleaning!

the methanol is like adding fuel, but it ALSO furthur reduces EGT...

methanol DOES increase cylinder pressures... you might want to add a set of head studs to the mix... 40-45psi on a good single w/ water/alky should make some **** good numbers.

of course... 60-65psi w/ twins and water/alky injection will make better numbers

 

talking about cylinder pressure, i'm all for keeping that down. what can i do to help keep it down? i was thinking about thicker head gaskets to reduce the c-r down to 14.0-1. i know it will run because the big cummins 400's got the 14-1 compression. so why won't little cummins "400" run better with 14-1? and what is a good way to calculate c-r at home??

 

and another question, what turbo does my stock 94 have? i know it has a wastegate...? looks a little small for all that e.g. to be runnin through..! kinda like bein in a chili eatin contest and fartin through a straw. i'm not scurd of burying a pyrometer for a few seconds.... i want a LOT of fuel. i got plans of puttin some of dem huge freightliner air cleaners on both sides of my truck with the big mirrors to go with it.... see wut it looks like, and put some k-n's in them so i can have lots and lots of clean, cool air. and for exhaust, i plan on a 4" downpipe with 6" stacks all while keeping flow characteristics in mind so i got plenty of good flow. i want all kinds of guages on it to keep an eye on everything and for tuning purposes, then when i get her runnin right, i will take most of the guages off. i also got an idea to ut a 8-71 supercharger on it to see if that helps any. im just a crazy 18 year old redneck with a pretty good understanding of how the diesel works with a good torch and welder to carry out all my crazy ideas with. i havn't got injectors yet and can still opt for o-ringed head while its in the shop. its alredy gettin ported and polished 3-angle valve job.

 

Your turbo is a HX-35, all the 12Vs came with them

CRIS

 

if you're gonna have the head off to do a thicker gasket, o-ring the head, and you won't have to worry too much about cylinder pressure...

cylinder pressure = power to an extent...

just saying that the methanol will begin to burn before the diesel does, which "adds timing" the way nitrous or boost does in a gas application (obviously it doesn't truly add timing, but it increases cylinder pressure the way advanced timing does)

I've thought about feeding a roots blower w/ a turbo on one of our motors... if we had a V type engine, I might consider it a little more, but packaging would be tough, cost would be up there, and the twins just work so well

Forrest

 

i tried to put that 8-71 blower on my ford idi one time, i never got very far with it tho. turbo lag would be like not there, and turbo surge that you were talking about wouldn't hurt you as much because the blower would kinda muffle it i think.??? could be wrong tho. i saw a 871 detroit with a turbo one time, that was a CHINGONA turbo!! i mean i could throw rocks through that bad boy or use it for a mud pump!!lol oh, and can you lean out a diesel to where it gets hot like a gasser??? or is more air-less fuel = lower temps always? i mean like could i hook up a 800 cfm ingersoll rand up to the intake and give it just enough fuel to idle and it wouldn't get hot??

 

If you have the head off get it o-ringed what better timing. If you put those big filter cans and mirrors you better post picks just don't forget the airhorns ontop of cab.