Howard Coleman

iTrader: (6)

it appears that one of the best methods to size the turbine a/r and wheel is to measure the pressure between the exhaust port and turbine wheel and relate it to boost within the intake manifold.

i read an excellent article ( a year or so ago) re the subject in Turbo magazine but have not been able to find the issue. my turbo guy, Kevin Draper at Majestic Turbo, mentioned copper tubing, a pressure gauge and something about using an a/c dryer in between (??). obviously there is a heat dispersal issue w regard to the pressure gauge... maybe that is solved by using 8 feet of tubing so the gauge will be in the cockpit?

once able to measure... just what should the relationship be between the incoming ("boost") psi and outgoing exhaust pressure.

i would be very appreciative if anyone on the forum has info on the subject.

thanks,

howard coleman

Sesshoumaru

iTrader: (1)

1:1 is perfect or the most effecient..........

i think 1:2 is a good number for street vehicles.

basically try to get the ratio the lowest you can.

If someone else knows some more info about this i'd like to hear too.....i really don't konw much about this.

There are tons of factors that i haven't even begun to understand that effect that ratio.

edit-

that's a really cool idea of measureing the back pressure. Let us know if that works.

RETed

Easiest and cheapest method I've heard of is use an NPT to compression fitting adapter tapped into the turbo exhaust manifold.
A copper compression "washer" is required.
Use the longest copper pipe you can run from the compression fitting into the cockpit.
If you want to run a length into a a coiled bundle for isolation, you're welcome to do so.
Minimum length of copper pipe I've seen in a diagram was only about 24"; since the boost or pressure gauge "dead ends", it should be enough, but I prefer to use at least 3 to 4 feet of copper pipe for isolation.
All parts can be easily sourced from your local home improvement store (i.e. Home Depot, Lowe's, etc.).
Copper pipe to boost or pressure gauge is trivial.


-Ted

Bond

Hey howard, i think i remember that magazine it was a good article. Anyway ive been messin with backpressure readings for about 6months now so i can give you some results.
Sesshoumaru is correct in saying 1:1 is perfect even 1:2 but damn impossible if you ask me. Right now im seeing 1:5 on mine at 20 lbs intake pressure. It seems the more boost you run the worse that ratio gets. Done around 10lbs intake press my ratio goes to 1:4. The turbine wheel is the key here, keeping the wheel size close to the compressor size will result in good numbers. The a/r on the turbine will effect the backpressure slightly, but a mismatched turbine wheel will throw it off the chart. In my last test on my car, we removed the P trim turbine wheel and rpl with Q trim. I dropped 200 deg on my egt with out remapping anything, and that ratio was alot better. I dont recommend going to the Q trim, unless your above a 64mm compressor wheel it really wont benifit you. My two cents, Reted feel free to dissaprove.

Howard Coleman

iTrader: (6)

bond, JAMES bond,

thanks for your response. your data is extremely interesting. 200 degrees less egt! without remapping and a better ratio. the stuff dreams are made of.

just so i am clear... 1:4 @ 10psi means 14 psi backpressure w 10 psi boost.
1:5 @ 20 means 30 psi backpressure at 20 psi boost. am i correct?

i find your comments re the wheel size vs the turbine a/r interesting. you seem to indicate that the wheel size (vs the comp wheel) is more important than the turbine a/r housing as to backpressure. i just had a discussion w a friend who is recently retired from being a big factor in the used dairy equip business. as such he worked w centrifugal compressors much like turbos. it was his opinion that turbine wheel size should not be as important as the housing a/r. you sd w a 20beem to be on the opposite side of this point and you have actually done some hands on work. (btw, he does know rotaries... he has 2. a 95 fd w an rx6 that rips and a 95 fd w a 20b t 66 that is so clean it looks oem.)

when you switched to the Q trim what were the ratios at 10 and 20 psi versus the P trim?

what is your pressure measuring setup? copper tubing? how long, what diameter? do you eventually switch to nylon berfore your gauge? what gauge do you use? has it performed o k w regard to the heat?

i run two t04s and am getting so much boost at 2000 rpm that i think i might be able to go up on my hot side. they make 80 pounds per minute at 1 bar so i won't need to run high boost. i have 2000 miles of tuning on them at this point. i will be rigging 2 egts and 2 pressure guages when i refire in a week or two.

thanks for your info and congrats on doing something valuable and sharing it. 200 degrees less egt is a huge step forward.

howard coleman

SPOautos

The turbine wheel does make a huge diff in back pressure. I dont know if I would say it makes more difference than the a/r or not though. The way I see it is its more of a relationship thing, you need to have the right turbine wheel for the right compressor wheel and a/r. I've heard of people making crazy high hp with decent spool with Q trims and .84 housings. If you had a P trim in a .84 you'd choke your engine to death haha.

I've also been thinking about setting up a boost gauge of some type to read back pressure. Here are a few things I've been wondering about. The farther the boost gauge is from the exhaust manifold the more the exhaust is going to cool, is this going to alter the pressure readings? I was thinking about usings some metal tubing that can handle high temps like inconel or something but make it very short (a foot or so) and use some type of pressure gauge that accepts a npt fitting and can handle the high heat....but I havent found one. There is a air craft supply place that I'm going to look at sometime next week, I'm pretty sure they have some that work with NPT but I dont know about the temp range they accept.

Anyway, sounds like a good project Howard, keep us all updated on your findings

Stephen

glemmers

Hi Howard, we meet at the MRR; Glenn with the CYM.

Static pressure measurements are temperature independent, so you can run as much line as you like to dissipate heat, it doesn't matter.

How's the custom twin setup going? Did you get your motor back yet?

As to your wheel size quesiton, if the compressor wheel is significantly larger than the turbine wheel, the compressor will have a larger moment of inertia than the turbine. The turbine being smaller, will also have a smaller "lever" arm for the exhaust gases to react against the wheel. The reduced impingment radius on the turbine reduces the power transmitted from the exhaust gases into the turbine, resulting in lower comressor/turbine operating speeds. Thus to get the same boost levels out of the compressor (aka, increased speeds), more energy most be disipated in the turbine. Flow is fixed, so the only variable that can be increased is turbine inlet pressure, or exhaust backpressure.

Hope this helps,

Glenn

Wargasm

I have heard from a reputable and well known tuner that 1:1 is the target ratio.

If you think about it, it makes perfect sense... the car is basically a big air pump. Two things are going on... the turbo is pushing air in at X pressure... and then as it tries to leave the engine, the engine is trying to push the air through the turbo. If the pressure in the exhaust manifold is also X... you've got a balanced system.

I would -guess- that in practice, most street cars are probably not at this "ideal" ratio... but that's usually ok because factors like boost response come into play for street driving. If you have a little more pressure in the exhaust manifold (say 20 psi in the manifold and 15 in the intake), that means that at lower flow rates (spool up time), you will have more oomph to spin the turbo. True, at higher RPM and higher flow, you will start to choke things up, but this might be fine for a street car where you want to balance low flow and high flow performance. I'm pretty sure that for a car that is operating in the top of the powerband most of the time, you would want to be as close to 1:1 as you can get.

Anyhow, that's my opinion....

Any dynos of the setup Howard?

Bond

Howard, my 1:5 ratio is on a Q trim .84 a/r T66. I was using a .96 on the Q trim but it wasnt coming on soon enough. Now with a proper tune, i may switch back to the .96 and probably come down a point in the ratio.

The pressure measuring setup is just as reted explained. I have a 1/8 tape in the manifold with a 1/8 copper line running inside the car. I believe it came from jegs, and its labeled for like a mechanical oil gauge.

Back to this pressure thing, thats correct howard at 20psi intake i have 30psi backpressure on the Q trim setup being a 1.5 ratio. I originallly had the P trim on this turbo and the gauge only goes to 35psi and it maxed it out. Seriously i would stay away from the Q unless your compressor wheel is larger than 64mm or so. The Q wheel is much heavier than the P and it takes alot to get it going, example: idle mines barely moving. The only reason im spending so much time on this issue is to prolong the life of my engine by reducing heat and pressure, by chosing correctly matched turbos. Its hard to find a turbo builder whos still interested in these issues rather than the dollar.

suganuma

Bond, what is making you choose 64mm as such a decision point?

suganuma

I'm guessing that it has to do with the sizing of the P trim wheel...

This has been posted before but I thought that it would be relevant to the discussion concerning compressor and turbine wheel sizing ratios.

MODEL-TRIM--------- INDUCER-----MAJOR--------INLET SIZE

T3-----35-------------35.46---------60.12----------59.69
T3-----40-------------37.69---------60.12----------59.69/76.20
T3-----45-------------40.51---------60.12----------59.69/76.20
T3-----50-------------42.52---------60.12----------59.69/76.20
T3-----55-------------44.70---------60.12----------59.69/76.20
T3-----60-------------46.48---------60.12----------59.69/76.20
T3-----SUPER60------48.26--------60.12----------59.69/76.20

TO4 S--------------48.36---------69.85---------69.85
TO4 SUPER-S-----48.36---------76.20---------69.85
TO4 T5/6-----------51.61---------69.85---------69.85
TO4 V--------------55.37---------69.85---------69.85
TO4 SUPER-V------55.37---------76.20---------69.85
TO4 H--------------58.37---------69.85---------69.85
TO4 SUPER-H------58.37---------76.20---------69.85
TO4 60-1 HI-FI----59.03---------76.20---------69.85
TO4 60-1-----------59.03---------76.20---------101.60
TO4 62-1-----------62.00---------76.20---------101.60

TO4E 40-------------47.50---------74.93---------76.20
TO4E 46-------------50.87---------74.93---------69.85/76.20
TO4E 50-------------53.90---------101.60--------69.85
TO4E 54-------------55.12---------74.93---------69.85/76.20
TO4E 57-------------56.64---------74.93---------69.85/76.20
TO4E 60-------------58.17---------74.93---------76.20/101.60

T-SERIES TS04------58.42----------83.92---------101.60
T-SERIES T-61------- 60.96---------89.92---------101.60
T-SERIES T-64-------63.25---------93.22---------101.60
T-SERIES T-66------- 65.53---------91.03---------101.60
T-SERIES T-70------- 69.09---------97.79---------101.60
T-SERIES T-72------- 72.14---------102.36--------101.60
T-SERIES T-76------- 76.71---------102.36--------101.60


MODEL--------TRIM----------EXDUCER-----MAJOR

T3-------------72-------------48.72---------58.90
T3-------------STAGE II------53.90---------65.00
T3-------------STAGE III-----56.62---------65.00
T3-------------STAGE V------61.95---------71.07
T4-------------N--------------52.60---------74.22
T4-------------O--------------58.32---------74.22
T4-------------P--------------64.62---------74.22
T4-------------Q--------------68.40---------79.02

Wargasm

Bond, a question...

If I have a P trim, 1.00 A/R... and I think it might be choking up top somewhat... would it be better to go to a Q trim 1.00 or just swap that 1.00 to a 1.15 and keep the P?

Dyno here if you want to see it (14 psi):

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/anyone-else-thinking-about-getting-new-groundzero-lim-368171/

maxcooper

The ratios are getting reported in a manner that I find confusing.

1:5 with 10 psi boost would lead me to believe you are seeing 50 psi (since 1:5 = 10:50) of backpressure, which can't be right.

Let's adopt a convention for this thread:

backpressure : boost, and normalize to 1 for boost

So, if you get 15 psi of backpressure while running 10 psi of boost, your ratio is 1.5:1.

In Maximum Boost, there is a recommendation for ratios no larger than 2.5:1, though that seems like a "go higher than this and you are crazy" kind of limit.

-Max

pluto

I have personally seen 4.5:1 ratio in a boosted car. The Titan supra is running 120-130psi of back pressure while running 35psi of boost. Everybody thinks that its impossible and that the car would choke but at the sametime, they're one of the fastest street tire car in US. go figure?

Before anybody goes any further, I wanted to make sure everybody is on the same page. There's a difference between measuring at equalibrum pressure and spool up pressure. You can easily get 3:1 or 4:1 while spooling up but once everything gets stabilize, you want to run as close to 1:1 as possible for optimium flow/performance.

modrx7

iTrader: (1)

I was always under the impression that you wanted the least backpressure when running a turbo application... but that is after the turbo, so ... I am confused.

Howard Coleman

iTrader: (6)

steve,

thanks for your helpful comments. i talked to cam worth last week and he observed that intial spool generally produces a multiple of the ratio achieved at constant max boost. exactly as you said... what does the optimally turbo-sized 13 b show as a ratio at max constant boost? it is interesting that there is apparently a time lag as to throughput between the turbine and compressor. i will be logging backpressure and egts.

bond,

have you observed a regressive ratio as you travel thru spool to max boost? if so what were the ratios.

howard coleman

fdracer

bond your numbering convention for your ratios is incorrect and is confusing everyone. 15psi of backpressure for 10 psi of boost is 1.5:1 not 5:1.

classicauto

iTrader: (3)

Bringing this back from the dead:

I've found a couple good threads like this with info on installing EMP/EBP gauges/senders..........but none that expand on what people used *exactly* and how it works or held up over time.

Howard, or anyone running these metrics, please post some info on what I should attach to the end of my coppper tubing Any senders work better then others? ones to stray away from, optimal location to tap into (on a divided tubular stainless mani. ) optimal length of tube etc.....

gusfd3s

Im using copper tubing about 3 feet (stainless is better though), then a teflon hose to this sender (100psi 0-5v sender): http://www.innovatemotorsports.com/x...cat=265&page=1

philiptompkins

iTrader: (4)

LOL, that reminded me of most everything on my car.

classicauto

iTrader: (3)

Thanks for the link!

How's the sender holding up? are you using it with a guage, or just logging the volatge?

If you're logging the voltage, what are the ranges? I know some have a small error range...ex: 0.1v = error'd out 0.2v=0psi Or at the top: 5v = error 4.99=100psi
Or is the scale right from 0-5?

Howard Coleman

iTrader: (6)

i had totally forgotten about this thread yet it is on a very important subject for the rotary. i now have v close to a 1 to 1 w my boost and it pays off in low EGTs.

i used stainless steel brake line (doesn't conduct heat) and a zero to 100 FJO pressure sensor... o-5 volts thru my Datalogit..///////////////////////////////////

last september i did 23 4th gear 2000-8000+ dyno runs running my FJO HD AI. given the thread is currently focused on tuning i thought i would pass on some of my metrics.

RPM*K----------------6---------6.4----------6.8--------7.2---------------7.6---------8



F IAT after IC
before alcohol------95--------94------------94----------94--------------94---------94

F water temp-------185------------------------------------------------------------------

tps--------------------100%-----------------------------------------------------------------

boost-----------------19.5------20.9--------21.1----------21-------------20.5------19.8

fuel press------------57.8------59.6--------59.8----------61.5----------53.4---------61.2

injector duty
cycle-------------------57.3-------63.5-------69.3----------73.6--------73.7----------73.3

knock-------------------22.5------4.0----------7.0-----------15.0--------13.5----------6.3

IGL----------------------12.5-------12-----------13.5---------14.5---------15----------15.3

IGT-----------------------1.5---------1-----------2.5------------3.5---------4-------------4.3

AFR----------------------11.5------11.8---------11.7----------11.9------11.1----------11.3

pre turbo
EGT----------------------1532------1553------1577-------1574---------1532--------1551

EMP PSI
(exhaust manifold
backpressure)-----------20----------10---------23-----------23-----------24------------26


the run (#23) was the last of the session... 498 rwhp SAE.

i thought it would be interesting to share the above as the thread is currently focusing on EGTs and of course i am running a fairly similar amount of meth as Brian.... actually a touch more.

note my EGTs are stable at 1550 at 20 psi.

my EMP is the reason. 23 psi backpressure at 20 psi boost.

my 2 rotor drives two Stage Five turbine wheels w two 3 inch downpipes.

when comparing turbos i take the inducer and exducers and solve for their area, add them together and divide by 2.

hotside area:

GT35R 5.17 sq inches
P trim 5.89
Q trim 6.65
GT42 87 mm 7.95
my two Stage Fives 10.81

add the hotside discharge area to 13 sq inches of DP:


and you probably have the answer re backpressure.

i do believe at some point, even w perfect tuning, ANY setup will revert to a linear upward progression of EGTs. EGTs are primarily a function of CCP (combustion chamber pressure) which is a function of torque. heat and pressure are eventually going to get all of us. at 20 psi w my setup i am not there yet. my turbos should make 44 lbs (each) per minute at 27 psi which should be 630 rw. i need stiffer actuator springs and then we will have at it in March.

of course the question remains, what do you do when you get to the inevitable point where EGTs reach "too high." probably lots of METHANOL is the answer given it's approx 300 degrees worth of higher auto ignition protection as well as cooling and octane. probably back down on ignition as well.

this thread is quite valuable. Brian is doing some interesting things and today, w major ignition and fuel changes should prove as interesting as yesterday.

through it all the primary cause for excitement is alcohol.

consider that on an 80 degree day Brian boosted over 20 psi and had an IAT around 90 with no intercooler!!! you certainly can get along without your intercooler if you wish... for certain modes.

consider my IAT out of my intercooler at 20 psi with virtually no airflow (dyno) was 91 BEFORE my alcohol. my UIM was freezing to the touch after each run.

and consider EMP as one of the key limits to power output. you really can't run too much exhaust on a rotary.

hc

Carlos Iglesias

iTrader: (6)

Here's my VERY recent implementation. Stainless 3/16ths tubing and a stainless collector. The GT40R is a divided turbo manifold so the dual inputs into a collector (thanks Paul!) was required. The quasi-deadend nature of the collecter and certainly sensor plumbing should be able to handle the exhaust. The collector to sensor tubing is just -04 Starlite.







I suspect Howard and I have the same FJO pressure transducer, a 0.5 - 4.5v MAP sensor. All of other the pressure sensors in my application are also 0.5 - 4.5v.

My biggest concern is having the sensor downstream from the collect and possibility the condensation my accumulate. The easy answer with be an Omega snubber before the sensor.

With the M4 (and other ECU) I'm mapping RPM to the ratio of MAP/EMAP. Throttle position is NOT used nor required.

Obviously more to follow once I map out and dyno the new setup.

classicauto

iTrader: (3)

Carlos & howard thanks for the pics and info! Just what I was after.

For Carlos - a couple questions regarding your location(s)

For me, I'm running a similar manifold setup. Am I going to get different readings at certain locations in the manifold? I was thinking of tapping my tubing into waste gate runners (where they are collected) but would this location give me useful/useless readings vs. putting them closer to the engine? (like yours, in the primaries)

RXHEAVEN_WA

Here is a set up and a thread on same topic

http://www.ausrotary.com/viewtopic.p...st=0&sk=t&sd=a