How do you read a compressor map?

[4sfed4]

Quote:

Originally posted by gasketmaster Turbos for all out race cars are kinda like torque converters.You can use the maps and calculations to help get you in the ballpark but you really won't know how it's going to work for you until you use it!

Unfortunately that true

All the calculations and planning can only at best be an educated guess. In the end, empirical testing is what will tell you what is really going on.

[glhsken]

Go KENTUCKY!!!"thumbs up

[turbodave/neon]

My buddy 4sfed4 wrote:

Quote:

Unfortunately that true All the calculations and planning can only at best be an educated guess. In the end, empirical testing is what will tell you what is really going on.

First, congrats to Larry on using the word "empirical" in a sentence!!!!

For the calculations part, sad but true. I hate to think how many times I have sat down and beat my brow against a spreadsheet. Got the parts and burned the spreadsheets after I get the "real world" results! My main flaw is that I over-engineer on the big stuff and underspend at the same time. DAYM THIS TD MENTALITY!!!!! Whew ranting is now done.

As for the 60-1 it works well on high output cars. But the lag is a big issue when I drive it on the street and at the eighth mile. The only issue I have with the smaller turbos is that they hit TOO hard. I do not like "0,0,0,1,2,28 psi". I can not get the car to handle that. It was the main factor why I bought the 60-1 hybrid. Those of you considering a 60-1 get the big shaft option! i can not stress to you how hard this big wheel is on the seals and bearing at 30 psi.

That and I like to make sick power with cars that never should have!

[4sfed4]

Quote:

Originally posted by turbodave/neon My buddy 4sfed4 wrote: First, congrats to Larry on using the word "empirical" in a sentence!!!!

Well thank you very much! I used to work for Applied Research in Miami (test lab) and that word was used all the time :big grin:

Basically, anything that is guided by actual experience and not theory alone is empirically derived.

Quote:

For the calculations part, sad but true. I hate to think how many times I have sat down and beat my brow against a spreadsheet. Got the parts and burned the spreadsheets after I get the "real world" results! My main flaw is that I over-engineer on the big stuff and underspend at the same time. DAYM THIS TD MENTALITY!!!!! Whew ranting is now done.

Underspend is my mentality to the extreme! I burn myself all the time with that when I am extra cheap.

Quote:

As for the 60-1 it works well on high output cars. But the lag is a big issue when I drive it on the street and at the eighth mile. The only issue I have with the smaller turbos is that they hit TOO hard. I do not like "0,0,0,1,2,28 psi". I can not get the car to handle that. It was the main factor why I bought the 60-1 hybrid. Those of you considering a 60-1 get the big shaft option! i can not stress to you how hard this big wheel is on the seals and bearing at 30 psi.

Your engine is probably too much for the 50 trim like weve been discussing. SO, you have to live the with the lag....heheheheehehehe :big grin:

Quote:

That and I like to make sick power with cars that never should have!

You need to get back to the dyno and see what thay baby is laying down. I think youd have the TurboDodge record....and on stock cast pistons to boot!

[turbodave/neon]

I agree Larry, I do need to go to the dyno and see what she lays down. But i don't know about the record though. A scosh over six hundred foot pounds at the crank at 22 psi and a 52 shot will put me in the ballpark, but not the record. I WILL try and walk up the boost a bit to say 26-28 psi on the cast pistons with the spray and that should get me into Diogo-ville! The issue as it has always been is..... how long will the pistons hold? I guess with my bonus I will build one of the spare engines up with the custom pistons that Cindy made for me and really lay the smack down.


I saw that the majority of the crowd here was talking about the 50 trim and decided to throw in my two cents worth when I heard 60-1! Albiet that my turbo is smoking (all Larry's fault"thumbs up ) an upgrade to a t61 wheel may be in order.Maybe bigger. Depends on the final compression ratio of the new engine. MORE MATH!!!! AAAAAAAAAUUUGH! And I may have to budget more than $64 for the rebuild. HRRRMMM may have to let this sit for awhile.....

[Frank]

Well now that I am back home, I was able to do some modifications to my spreadsheet....

1. Fixed some graphing bugs.
2. Added more of the GT Series turbo options.
3. Because of #2, I was able to graph the actual turbo I want to use. See below picture and note the crank HP data point!
4. Added a estimated crank horsepower based on airflow.
5. Made it available to the public.

Here is my compressor map matched with the 3.0L. I will be using the .63 a/r turbine housing.

[IMG]http://www.***************/frank/gt30r.jpg[/IMG]


The link below is to my tech section that contains the spreadsheet for Garrett Turbo Sizing. (2MB file!!!!)
http://www.***************/tech.shtml

Frank

[DirectConnection]

Quote:

Originally posted by contraption22 An article in Hot Rod mag last month (which is fully available for free right now on hotrod.com) Recommends that you use a VE of 100% when doing these calculations. ...Next, you need to add boost into the equation. Turbo engineers use pressure ratio (the ratio of the total absolute pressure produced at the turbo outlet divided by atmospheric pressure) instead of an outright expression of boost pressure. Compressor pressure ratios corresponding to boost levels of 10 psi and 15 psi are 1.68 and 2.02, respectively; to find other pressure ratios:

They forgot to calculate the intercooler's pressure drop into the equation. Very important!
Larry...was it you on the FMML that did a test on the stock T-III intercooler backpressure readings? I *think* I remember you had like a 7 psi drop over 6k, correct?
BTW... this is a great thread even though I am a month late!

[DirectConnection]

Quote:

Originally posted by 4sfed4 As far as what is a "good" backpressure reading, I can only offer what I have measured on my car. With the stock trubo, I saw 43 psi backpressure for 13 psi boost. Thats terrible. But, thats also why the turbo would spool so fast. With the TO4E 50 / Stage 3 / 0.63, I saw about 24 psi backpressure with 14 psi boost. When I raised boost to 20 psi, backpressure was 42 psi.

The book on turbocharging I have mentions the pressure ratio of 1:1 on some cars. People have expressed concern over the use of overlap on turbo dodge engines with high boost. The theory is that with the high boost and overlap, the boost escapes via the exhaust, to the point of defeating the purpose the overlap was designed for in the 1st place. In this book by Hugh MacInnes (Turbochargers) he states that with a 1:1 pressure ratio and overlap, the scavenging results are exceptional. I forgot what his claims were %-wise, but it was astonishing!

[TheGinMill]

Quote:

Originally posted by DirectConnection The book on turbocharging I have mentions the pressure ratio of 1:1 on some cars.

Title of said book?

This thread answered so many of my questions, I have more, but figure Ill let this run its course a bit further, they will probably be answered.

"thumbs up "thumbs up to you guys, Thanks much,
Matt

[DirectConnection]

Title of the book...you missed it in my last post:big grin:
No problem though... it's called: TURBOCHARGERS and is written by Hugh MacInnes. HP Books and the ISBN # is: 0-89586-135-6
This book may be older than Corky Bell's book, but is more technical, and considered more accurate by most. I think this is the book that Gus often referred to.

[TheGinMill]

Ordered, thanks. Of course, had to get another copy of auto math as well, why not, right??

[DirectConnection]

Quote:

Originally posted by gin8122 Ordered, thanks. Of course, had to get another copy of auto math as well, why not, right??

Never hurts to learn!
My problem is that I have a bunch of books. I spend a couple nights reading and learning, then get burnt out and the book goes back on the shelf...until a year or so later. Then it all repeats itself

[theskeptic]

A quickie question: What housing would a T-61 compressor wheel fit into? A T04E or a T04S maybe?

I'm debating a new turbo, and the T-61 and T04E Super-50 looked good because I run higher PR's way up here in Santa Fe and they'll flow like a mutha...

-Dana

[4sfed4]

Quote:

Originally posted by DirectConnection Larry...was it you on the FMML that did a test on the stock T-III intercooler backpressure readings? I *think* I remember you had like a 7 psi drop over 6k, correct?

Yes...that was me.

Basically, what I found was that to get 13 psi in the intake, there was over 20 at the turbo outlet. I could get a boost spike as high as about 25 at low rpm (with pressure pre-IC being in the low 30's), but the pressure would drop as flow increased and the turbo couldnt keep up.

[DirectConnection]

Quote:

Originally posted by 4sfed4 Yes...that was me. Basically, what I found was that to get 13 psi in the intake, there was over 20 at the turbo outlet. I could get a boost spike as high as about 25 at low rpm (with pressure pre-IC being in the low 30's), but the pressure would drop as flow increased and the turbo couldnt keep up.

Ah... 7psi pressure drop on only 13psi. I assume this was tested at max rpm, too. What would you guesstimate the drop to be if you could maintain 25psi up to 6,500 rpms? 10+?

Something else to think about.... what would that pressure drop be at 13psi and the same stock cooler, yet with the turbo you have now? I know the cooler dictates the pressure drop through it's restrictions, but a much cooler outlet charge might flow differently. FMML had a big discussion years back about hot airflow (friction) vs cooler airflow, and/or the effect of how air flows... but ended up in an arguement