Hey you turbo geeks! Help us dumbasses understand the limits of the the Evo 6.5 TME turbo. Using this compressor map, what is the most this compressor can efficiently boost on an Evo at 7000 rpms for maximum power? What does it say in general? Also, please explain the x and y axis....

 

The Y-axis is the pressure ratio. The X-axis is going to be the metric equivalent to CFM I believe.

 

This site has a wealth of info
http://www.stealth316.com
although its for the V6 2.9l engine with a little math the numbers can be calculated for the 4g63

 

Now that I think about it, I believe the X-axis is a mass flow rate (kg/sec)

 

keep in mind that efficiency is going to be a bit less important with that phat AMS intercooler - at least as far as boost/intake temps go.

turbo longevity on the other hand ... intuition tells me that these alky guys running 28psi on the stock (non-TME) turbo are going to be the first to find that out.

 

Great info. Keep it coming. I wish I was good enough with photoshop and my calculator. Are there any guys out there that wear pocket protectors and carry around there HP calculator that would want to modify the graph like this one with the 2.9 liter engine?

 

Im no expert, but by the looks of it, the absolute MAX psi for that turbo looks to be about 32psi before the turbo starts to fall apart (spin itself to death). I believe that a pressure ratio of 2.0=14.7 psi....so 3.0=29.4 psi. CFM is CFM, I dont know how that relates to engine RPM.

IMO, the more CFM, the more potential to make power. For example: If you are boosting 28psi but your CFM is ~350 as opposed to boosting 24psi w/CFM of 520......shouldnt you make more power @ 24psi??? Im not an expert, this is just what I think.

INFO: http://bimmerforums.com/forum/showthread.php?t=258035

http://www.stealth316.com/2-turbotemp.htm

http://forums.nasioc.com/forums/show...ressor+map+rpm

 

The graph with the boost -rpm points is made for one bank of the V6 ~ 1.5 liters. On our 2.0 engine @7.5k rpm/20 psi(~2.38 pressure ratio) we are at the right edge of the 65% island very close to 600cfm. But as rpm increases VE decreases and to maintain boost the turbo has to work harder to keep up.

 

Smoggy, try this link: (cough) ... delete (cough) already posted by drew...

l8r)

 

Hmm, so if I'm assuming a 90%VE on a cammed 2 liter 4g63, then am I correct in getting?:

21psi @ 7000rpm = ~540cfm
22psi @ 7000rpm = ~556cfm
23psi @ 7000rpm = ~571cfm
24psi @ 7000rpm = ~586cfm
25psi @ 7000rpm = ~601cfm
26psi @ 7000rpm = ~616cfm
27psi @ 7000rpm = ~631cfm
28psi @ 7000rpm = ~646cfm
29psi @ 7000rpm = ~661cfm
30psi @ 7000rpm = ~676cfm

Given this list, I'd say that that 24psi at 7000rpms is really the max. I suppose you could push it, but you rapidly end up getting into diminishing efficiency.

However, if I'm reading the compressor map correctly (and doing the math right), then the real concern isn't so much the boost at high rpms, it's the boost at low rpms. Lemme 'splain .... with our Evo's it is common to see the boost taper off at high rpms, so if you're hitting, say 28psi and tapering off to around 24psi by 7000rpm, then at 7000rpm you're ok. The problem is that usually you'll hit max boost anywhere from 3000-3500rpm. So if you look at the values of the lower end (3000) you get (assuming 90%VE):

21psi @ 3000rpm = ~231cfm
22psi @ 3000rpm = ~238cfm
23psi @ 3000rpm = ~245cfm
24psi @ 3000rpm = ~252cfm
25psi @ 3000rpm = ~259cfm
26psi @ 3000rpm = ~266cfm
27psi @ 3000rpm = ~273cfm
28psi @ 3000rpm = ~280cfm
29psi @ 3000rpm = ~287cfm
30psi @ 3000rpm = ~294cfm

Anything past 25psi at this point is off the chart, even 25psi is just barely on the last efficiency "island". So, IMO, I'd say that boosting past 25psi just doesn't make much sense for this turbo (unless you just want to make it glow ). If you're getting max boost by 3000rpms, I'd prolly shoot for 25psi, tapering off to maybe 23psi by 7000rpm. If your max boost hits later, you could try one or two more psi, but not all that much more.

l8r)

 

Seems correcto mundo! iirc the left side is called the surge line, the turbo gets ahead of itself. I see 24~25 psi @3500 rpm in 5th cause my stock boost solenoid wont allow more even at 100% dc.

 

Yep, forgot to mention the surge line ... don't wanna get too near that, or very bad things start happening to your turbo.

NEways, after I found the article on the bimmerforums, I decided to expand the spreadsheet originally posted (see the attached file). Some things I've updated:

- It now lists RPM incremented in units of 500
- You can enter VE and PSI for each RPM bracket
- Comes pre-populated with boost levels on a stock '03/'04 Evo
- and it generates a graph for you ... bling bling...

Enjoy!!

BTW: Does anyone know the VE for the 4G63 in our Evos? (cammed and uncammed if ya got it)

Edit: attachment removed ... corrected spreadsheet is posted later in this thread.

l8r)

 

Awesome man!

 

Thanks Ludikraut!

 

My junk can't hold. Even at 100% with the silver pill in line, I taper to 17psi by fuel cut.