eag36

Back to the topic of reading turbo maps for your car and how everyone finds that you can run bigger turbo's then you're supposed too... I have an idea which i have yet to turn into an excel spreadsheet... but i may someday. All the programs i've found to calculate what your car will 'flow' for air, isn't taking in to consideration that it is a forced induction motor. The calculations take the engine displacement (say 2.0L) and then divide by 2, multiply my rpms, (change into different units and mulitply by efficiency, but i'm trying to not go into great detail here) And you have your air flowrate which you can then plot on a turbo chart right?

Well the first thing that i'm just thinking of now is that when your exhaust is leaving its now 700-1000 C which makes it much less dense so it is actually has a higher volumetric flowrate ( i'm not sure if the turbo map compensates for that)

But what im pretty sure the turbo map doesn't compensate for is the fact that when the turbo is actually on the car and you are reaching boost... you no longer have a 2.0L engine. say you're at 7.4 psi of boost... you now have a 3.0L engine. 14.7psi and you now have a 4.0L engine. So say you're at 5k rpms with 14 psi of boost... you can no longer say you have a 2.0L engine. Since you are running 2 atmospheres of pressure in your engine, you must now calculate your turbo plot as if you had a 4.0L motor. So the turbo plots aren't actually a straight line at all but in fact you are increasing your effective displacement which will make the turbo plot a curve which is why you can run these big turbo's on the smaller engines.

I'm gonna try to make an excel spreadsheet for this so we can test my theory that this is a more accurate way to match a turbo to a motor.

Let me hear what you think about this.

*Boostwerks*

Turbo maps arn't neccisarily supposed to predict how a "turbo will do", but more of a guide to help select the right turbo for your particular application.

When I look at a compressor map, I basically just see that at a certain pressure differential, this is how much airflow this turbo is going to support. Based on my spool, and overall HP requirements, I can select a turbo that fits roughly with my needs. However, how the turbo will actually respond on the car, will be decided more from actual experience. Theres just too many variables.

turncoat

Ha, you've solved it!!! Congrats, now go apply to Garrett or Borg Warner as VP of Engineering.

Maybe it would be a good idea to read up a little before you apply, though. Just prep for your interview, ya know.

http://www.turbobygarrett.com/....html

p.s. maps are posted in lb/hr and thus temperature would already be compensated for (for the purposes of your first observation, anyway).

pps. Did figure out what the pressure ratio (y-axis) is yet? That might help you with your second observation.

SOHC_MShue

I think you need to brush up on the math again . When you calculate the engine's airflow you also need to multiply it by the desired PR.

TheShodan

iTrader: (14)

Bryson's got a VERY good point about the experience needed about using a compressor map in relation to sizing the correct turbo. Even with all the "math" of sizing these correctly, you're only looking at half the story. It's like trying to determine how big a cube is, and you can only see one side that looks like a square. You're not considering the Actual engine itself (bore and stroke are not enough) as well as the turbine efficiency of the application used.

b16hybridsol

its usually all just round abouts utill you get the turbo on the car and get all your real numbers

eag36

Mother F.....

all this time i thought the Air Flow on the lower axis was what your engine was flowing into the turbine... not what the compressor was flowing into the engine.

I thought you figured out what your engine was flowing for air flow, and it told you what pressure ratio it could support.

And now to defend myself (no harm or ill tempor meant )

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">I think you need to brush up on the math again . When you calculate the engine's airflow you also need to multiply it by the desired PR. </TD></TR></TABLE>
Now that I know how to read the compressor maps there is no need calculate the engine's airflow... so no brush up needed.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turncoat &raquo;</TD></TR><TR><TD CLASS="quote">Ha, you've solved it!!! Congrats, now go apply to Garrett or Borg Warner as VP of Engineering.

Maybe it would be a good idea to read up a little before you apply, though. Just prep for your interview, ya know.

http://www.turbobygarrett.com/....html

p.s. maps are posted in lb/hr and thus temperature would already be compensated for (for the purposes of your first observation, anyway).

pps. Did figure out what the pressure ratio (y-axis) is yet? That might help you with your second observation.</TD></TR></TABLE>

To your first comment.... thanks for the sarchasm
To your link... thanks, that was actually very helpful (no sarchasm)
To your next comment, as it is plotted on the compressor map... yes you're right, since it's in lb/hr it doesn't matter... but if it was as i was thinking (wrongly) before then it would have mattered, because hotter gas means less dense and would have meant quicker spool time... but this no longer matters.
To your last comment... This was the one part of the turbo map that I was reading correctly before and am not quite sure what you mean by this would help with my second observation....

To everyone else... thanks for the replies, and bursting my bubble...

Just kidding, i'm much happier now that i know how to read those maps correctly. But I know I read instructions on how to read these maps from different online sources and even downloaded an excell program to plot them which was wrong.

I guess what i was trying to do would have been reading a turbine wheel/housing map, not a compressor map. That is why i was trying to factor in the temperature of the exhaust gasses and what boost the engine was running.

Do they make turbine maps??? I have a feeling that is where a lot of the quicker or slower spool times come from.

turncoat

Yeah, sorry, I re-read my earlier post and think I owe you a apology for being an ***.

The Garrett link I posted above is pretty clear as you found out. Bet more than 90% of the people on FI don't know how to read or plot a map - this should be <U>required reading</U>.

turncoat

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eag36 &raquo;</TD></TR><TR><TD CLASS="quote">
Do they make turbine maps??? I have a feeling that is where a lot of the quicker or slower spool times come from.</TD></TR></TABLE>

Say like this...?

http://www.turbobygarrett.com/...14568

However, figuring out your flow through your turbine is a bit more of a guess than for the compressor.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eag36 &raquo;</TD></TR><TR><TD CLASS="quote">But I know I read instructions on how to read these maps from different online sources and even downloaded an excell program to plot them which was wrong.</TD></TR></TABLE>

Search for turbocalc-v1.xls. I can send you a copy if you can't find it.

eag36

don't worry about the sarcasm, you weren't trying to be an *** but everything sounds different typed out. At least you provided relavent info after and it wasn't just sarcasm like some people post. But i would love it if you sent me a copy of that turbo calc program. My e-mail is EricDC2@gmail.com

Thanks

turncoat

better yet, found a link to it.

No, I was being an ***, I gotta learn when to shut up.

http://web.tampabay.rr.com/ent...c.xls

eag36

thanks for the link