measuring boost psi with torque app on 07 bluetec
11-11-2011, 12:10 AM
#1
MBWorld Fanatic!
Thread Starter
measuring boost psi with torque app on 07 bluetec
It's my understanding that my Turbo maxes out at 29 psi according to the specs. The torque app for android (which reads information in real time via an obd2 Bluetooth transceiver) has only showed me a Max of 23 psi under heavy accerleration. Is this normal, or should I be looking into why the Turbo is not achieving it's rated 29 psi max?
11-11-2011, 03:02 AM
#2
Super Member
My personal preference is a gauge connected directly to the intake manifold. The software may have an "interpretation" program that is not as accurate translating kPa to psi. Any way to calibrate the program on a known source?
Also, the 29psi may be a design max, say towing a heavy trailer uphill in Denver (high altitude), and your testing may not trigger the load map in the ECU to let the waste gate push the compressor to that level.
Also, the 29psi may be a design max, say towing a heavy trailer uphill in Denver (high altitude), and your testing may not trigger the load map in the ECU to let the waste gate push the compressor to that level.
11-14-2011, 07:43 PM
#4
Newbie
Join Date: Nov 2011
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
E320 CDI
That poor tiny little turbo would be screaming at 200,000rpm by the engine's middle RPM range if it were actually making 29psi of boost!
14.5psi is far more realistic given how small the turbo is and how little power the engine makes.
14.5psi is far more realistic given how small the turbo is and how little power the engine makes.
11-15-2011, 01:34 AM
#5
Super Member
The turbo is actually sized to perfection, and is capable of much more with the VNT technology. MB has it detuned to meet emission standards etc. It happily pulls these heavy vehicles and their tow load 150K miles and beyond without failures and the lag is virtually non existent. Don't let the visual appearance of the compressor housing fool you. It's the trim of the compressor that matters more. Also I'm curious why you say these engine makes "little power". 220+ HP from a single turbo 3.0 V6 diesel is little? I remember when the Nissan 300ZX with a twin turbo 3.0 V6 GAS motor was a marvel with 300 HP. And that was a GAS motor. Give an example of what 3.0 or so diesel motor makes significantly more power. The new Dodge Ram with a Cummings motor more than twice the CDI size (6.7L) only makes 350 HP. And the 2012 Blue Tec with the redesigned engines are now up to 240, just 110 HP shy of the huge 6.7L Ram.
OP: From what I remember when last I researched the boost levels from the Mercedes workshop manual, it's set around 25PSI, so your setup may be pretty close. Would love to hear the results if you can compare it to a mechanical gauge. By the way, here is a published magazine article that puts it at around 30PSI as you first mentioned.
OP: From what I remember when last I researched the boost levels from the Mercedes workshop manual, it's set around 25PSI, so your setup may be pretty close. Would love to hear the results if you can compare it to a mechanical gauge. By the way, here is a published magazine article that puts it at around 30PSI as you first mentioned.
Last edited by dgiturbo; 11-15-2011 at 01:39 AM.
11-15-2011, 07:31 AM
#6
Banned
Join Date: Nov 2011
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
1982 300D VNT, 1980 240D 3.0T
VNT only helps it spool up quicker. It has nothing to do with how much boost the turbo can produce. The trim means nothing, the inducer diameter limits how much air the compressor can flow (The volume of air it can suck in before the air's velocity nears the speed of sound). 220hp IS very small. VW makes 170hp from 2.0L which is 85hp/L and BMW makes 88hp/L while MB's V6 makes only 73hp/L. Go to the sprinter and its a paltry 62hp/L.
Nissan's 300ZX is an antique to today's technology. Natural V6's today make that much power. Nissan's current base 3.6L V6 makes 331hp. So why can that non-turbo V6 make 331hp while your CDI needs "29psi of boost" to make just 220hp?
"Give an example of what 3.0 or so diesel motor makes significantly more power."
BMW for one (335d). Second, look to Finland where people make 400+hp with Mercedes' old IDI I-6 with just a turbo, intercooler and injection pump change. BTW, the Finns make that much power out of the antique engines with less than 30psi of boost.
"The new Dodge Ram with a Cummings motor more than twice the CDI size (6.7L) only makes 350 HP."
First, its Cummins. Don't make a fool of yourself saying it with a "g".
It also only revvs to 3500rpm and it produces more than twice the torque. Also, they can get upwards of 500hp with only a tuner.
"And the 2012 Blue Tec with the redesigned engines are now up to 240"
Thats still less than what BMW has had a available for the last 2 years.
"here is a published magazine article that puts it at around 30PSI as you first mentioned."
Again, thats absolute pressure. Gauge pressure is 14.7psi lower.
Nissan's 300ZX is an antique to today's technology. Natural V6's today make that much power. Nissan's current base 3.6L V6 makes 331hp. So why can that non-turbo V6 make 331hp while your CDI needs "29psi of boost" to make just 220hp?
"Give an example of what 3.0 or so diesel motor makes significantly more power."
BMW for one (335d). Second, look to Finland where people make 400+hp with Mercedes' old IDI I-6 with just a turbo, intercooler and injection pump change. BTW, the Finns make that much power out of the antique engines with less than 30psi of boost.
"The new Dodge Ram with a Cummings motor more than twice the CDI size (6.7L) only makes 350 HP."
First, its Cummins. Don't make a fool of yourself saying it with a "g".
It also only revvs to 3500rpm and it produces more than twice the torque. Also, they can get upwards of 500hp with only a tuner.
"And the 2012 Blue Tec with the redesigned engines are now up to 240"
Thats still less than what BMW has had a available for the last 2 years.
"here is a published magazine article that puts it at around 30PSI as you first mentioned."
Again, thats absolute pressure. Gauge pressure is 14.7psi lower.
Last edited by Backup; 11-15-2011 at 07:39 AM.
11-15-2011, 07:50 AM
#7
Banned
Join Date: Nov 2011
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts
1982 300D VNT, 1980 240D 3.0T
Turbo 101
Need more proof you're wrong? Okay!
Here is a map of your turbo, the GTB2056Vk. The red dots are your engine at sea level with 30psi of boost from 1600rpm to 3800rpm. As you can see, 30psi is only possible from 2000-3000rpm and 3000-3800rpm it must drop like a stone to prevent the compressor wheel from exploding from overspeeding. To make 30psi at the engine's advertized 3800rpm peak horespower the turbo would have to be spinning over 400,000rpm. To make the engine's advertized torque plateau from 1600-2500rpm the turbo would be in the very damaging surge range from 1600-2000rpm.
As you go up in altitude that RPM range where its capable of 30psi shrinks drastically due to the higher pressure ratio required.
Though I think by now you'll have skipped to the end of the post and reply with something like "Nuh uh, you're wrong because you are somebody I don't like!"
Now, the green lines show the actual boost pressure of 15psi. As you can see, from 1600rpm to 3800rpm the compressor is entirely within the map and in efficient ranges. From 2000-3000rpm the airflow and pressure are exactly in the compressor's most efficient range of 78%.
NONE of Garrett's compressors are capable of making 30psi of boost from 1600-3800rpm. The ones that can flow enough air at 30psi and 3800rpm (GT3571V and larger) are deep into surge at lower RPMs. NONE of Garrett's turbos can produce the 3.06 required pressure ratio down to 1600rpm, the GTB2056VK is the smallest capable of such a pressure ratio!
If you go look at your scan gauge with the engine at idle it will show around 14.7psi. That is atmospheric pressure. Even a belt driven supercharger isn't capable of making 14.7psi of boost with an engine at idle.
So, now you know the difference between absolute pressure and gauge pressure, mkay?
The only possible way you can prove me wrong is to hook up a mechanical gauge to the intake manifold and video it next to the tachometer as you accelerate at full power across the RPM range.
Here is a map of your turbo, the GTB2056Vk. The red dots are your engine at sea level with 30psi of boost from 1600rpm to 3800rpm. As you can see, 30psi is only possible from 2000-3000rpm and 3000-3800rpm it must drop like a stone to prevent the compressor wheel from exploding from overspeeding. To make 30psi at the engine's advertized 3800rpm peak horespower the turbo would have to be spinning over 400,000rpm. To make the engine's advertized torque plateau from 1600-2500rpm the turbo would be in the very damaging surge range from 1600-2000rpm.
As you go up in altitude that RPM range where its capable of 30psi shrinks drastically due to the higher pressure ratio required.
Though I think by now you'll have skipped to the end of the post and reply with something like "Nuh uh, you're wrong because you are somebody I don't like!"
Now, the green lines show the actual boost pressure of 15psi. As you can see, from 1600rpm to 3800rpm the compressor is entirely within the map and in efficient ranges. From 2000-3000rpm the airflow and pressure are exactly in the compressor's most efficient range of 78%.
NONE of Garrett's compressors are capable of making 30psi of boost from 1600-3800rpm. The ones that can flow enough air at 30psi and 3800rpm (GT3571V and larger) are deep into surge at lower RPMs. NONE of Garrett's turbos can produce the 3.06 required pressure ratio down to 1600rpm, the GTB2056VK is the smallest capable of such a pressure ratio!
If you go look at your scan gauge with the engine at idle it will show around 14.7psi. That is atmospheric pressure. Even a belt driven supercharger isn't capable of making 14.7psi of boost with an engine at idle.
So, now you know the difference between absolute pressure and gauge pressure, mkay?
The only possible way you can prove me wrong is to hook up a mechanical gauge to the intake manifold and video it next to the tachometer as you accelerate at full power across the RPM range.
Last edited by Backup; 11-15-2011 at 08:13 AM.
Trending Topics
11-15-2011, 10:40 PM
#8
Super Member
Backup, first, I like everyone, and love chats about turbos. Never met you on the forum before, but by the way you answered and referenced the other posts, I guess you use a few user names?
No worries. Also, sorry about my typo with Cummins. Great company and I actually owned a 2500 Ram diesel before buying my ML. Typos can happen.
Next, gauge manufactures know that our planet is pressurized to 14.7, so when they make gauges, they set the indicator to read 0 PSI at atmospheric pressure, so the user doesn't have to subtract anything. Therefore anything shown on the gauge is the actual source pressure. Do you do that math also when you put air in your tires?
Now why spend so much time trying to show me I'm wrong? Seriously, a surge map? DubVBenz just wanted to know why he wasn't getting the 29LBS of boost that Mercedes states in their tech manual at Strartekinfo.com. So is Mercedes wrong also? The vehicles are out there and running fine worldwide. I have one and it gets up and goes when my right foot hammers down.
Anyways, if you must test my expertise with turbos, here goes. I will even use your surge map if OK with you.
First formula you need is to find CFM: CFM = (L x RPM x VE x Pr)/5660
L is liters. 3.0 OK with you? And a diesel Volumetric efficiency of 90% still OK? And can we say that the engine should be at full boost by say 2200RPM since it redlines around 4000? (Most tuners like to see full boost by half the RPM range.)
Next calculate the Pressure ratio (PR) (14.7+29PSI of boost)/14.7 which gives a PR of 2.972. So plugging these values into the CFM formula gives a CFM of 311.90 or divide by 14.27 to convert to your charts lb/min reference of 21.85lbs/min.
Now check this out, the airflow of 21.85 (x axis) intersects 2.97 (y axis) at the 74% efficiency island trace. WOW!! Excellent job Mercedes. 74% efficient at 29Lbs of boost shows the turbo is PERFECT!!! Not overheating the air it is compressing, not in the surge area and full boost comfortably where most people need it. I am not even going to bother with the several other errors in your post. Entertaining reading though.
Oh, few more things, the BMW 335D uses 2 turbos to make 25 more HP than Mercedes in the 3.0 class. That's a "significant" example? Oh, and does the non turbo Nissan V6 make 455 pounds of torque? Guess that's what the 29LBS of boost is for. And if compressor trim is not important, why does the surge map you posted and almost all I have seen/studied label the compressor trim level for each turbo?
Tell you what, get a hold of Mercedes engineers and tell them that there are way off base in their turbo sizing, and the 3.0 CDI/Bluetec motors can't make the power they claim or should be manufactured to make 400+HP.
Or how about just offering some insight as to the OP's low boost question?
No worries. Also, sorry about my typo with Cummins. Great company and I actually owned a 2500 Ram diesel before buying my ML. Typos can happen.
Next, gauge manufactures know that our planet is pressurized to 14.7, so when they make gauges, they set the indicator to read 0 PSI at atmospheric pressure, so the user doesn't have to subtract anything. Therefore anything shown on the gauge is the actual source pressure. Do you do that math also when you put air in your tires?
Now why spend so much time trying to show me I'm wrong? Seriously, a surge map? DubVBenz just wanted to know why he wasn't getting the 29LBS of boost that Mercedes states in their tech manual at Strartekinfo.com. So is Mercedes wrong also? The vehicles are out there and running fine worldwide. I have one and it gets up and goes when my right foot hammers down.
Anyways, if you must test my expertise with turbos, here goes. I will even use your surge map if OK with you.
First formula you need is to find CFM: CFM = (L x RPM x VE x Pr)/5660
L is liters. 3.0 OK with you? And a diesel Volumetric efficiency of 90% still OK? And can we say that the engine should be at full boost by say 2200RPM since it redlines around 4000? (Most tuners like to see full boost by half the RPM range.)
Next calculate the Pressure ratio (PR) (14.7+29PSI of boost)/14.7 which gives a PR of 2.972. So plugging these values into the CFM formula gives a CFM of 311.90 or divide by 14.27 to convert to your charts lb/min reference of 21.85lbs/min.
Now check this out, the airflow of 21.85 (x axis) intersects 2.97 (y axis) at the 74% efficiency island trace. WOW!! Excellent job Mercedes. 74% efficient at 29Lbs of boost shows the turbo is PERFECT!!! Not overheating the air it is compressing, not in the surge area and full boost comfortably where most people need it. I am not even going to bother with the several other errors in your post. Entertaining reading though.
Oh, few more things, the BMW 335D uses 2 turbos to make 25 more HP than Mercedes in the 3.0 class. That's a "significant" example? Oh, and does the non turbo Nissan V6 make 455 pounds of torque? Guess that's what the 29LBS of boost is for. And if compressor trim is not important, why does the surge map you posted and almost all I have seen/studied label the compressor trim level for each turbo?
Tell you what, get a hold of Mercedes engineers and tell them that there are way off base in their turbo sizing, and the 3.0 CDI/Bluetec motors can't make the power they claim or should be manufactured to make 400+HP.
Or how about just offering some insight as to the OP's low boost question?
11-16-2011, 06:42 PM
#10
MBWorld Fanatic!
Thread Starter
Backup, first, I like everyone, and love chats about turbos. Never met you on the forum before, but by the way you answered and referenced the other posts, I guess you use a few user names?
No worries. Also, sorry about my typo with Cummins. Great company and I actually owned a 2500 Ram diesel before buying my ML. Typos can happen.
Next, gauge manufactures know that our planet is pressurized to 14.7, so when they make gauges, they set the indicator to read 0 PSI at atmospheric pressure, so the user doesn't have to subtract anything. Therefore anything shown on the gauge is the actual source pressure. Do you do that math also when you put air in your tires?
Now why spend so much time trying to show me I'm wrong? Seriously, a surge map? DubVBenz just wanted to know why he wasn't getting the 29LBS of boost that Mercedes states in their tech manual at Strartekinfo.com. So is Mercedes wrong also? The vehicles are out there and running fine worldwide. I have one and it gets up and goes when my right foot hammers down.
Anyways, if you must test my expertise with turbos, here goes. I will even use your surge map if OK with you.
First formula you need is to find CFM: CFM = (L x RPM x VE x Pr)/5660
L is liters. 3.0 OK with you? And a diesel Volumetric efficiency of 90% still OK? And can we say that the engine should be at full boost by say 2200RPM since it redlines around 4000? (Most tuners like to see full boost by half the RPM range.)
Next calculate the Pressure ratio (PR) (14.7+29PSI of boost)/14.7 which gives a PR of 2.972. So plugging these values into the CFM formula gives a CFM of 311.90 or divide by 14.27 to convert to your charts lb/min reference of 21.85lbs/min.
Now check this out, the airflow of 21.85 (x axis) intersects 2.97 (y axis) at the 74% efficiency island trace. WOW!! Excellent job Mercedes. 74% efficient at 29Lbs of boost shows the turbo is PERFECT!!! Not overheating the air it is compressing, not in the surge area and full boost comfortably where most people need it. I am not even going to bother with the several other errors in your post. Entertaining reading though.
Oh, few more things, the BMW 335D uses 2 turbos to make 25 more HP than Mercedes in the 3.0 class. That's a "significant" example? Oh, and does the non turbo Nissan V6 make 455 pounds of torque? Guess that's what the 29LBS of boost is for. And if compressor trim is not important, why does the surge map you posted and almost all I have seen/studied label the compressor trim level for each turbo?
Tell you what, get a hold of Mercedes engineers and tell them that there are way off base in their turbo sizing, and the 3.0 CDI/Bluetec motors can't make the power they claim or should be manufactured to make 400+HP.
Or how about just offering some insight as to the OP's low boost question?
No worries. Also, sorry about my typo with Cummins. Great company and I actually owned a 2500 Ram diesel before buying my ML. Typos can happen.
Next, gauge manufactures know that our planet is pressurized to 14.7, so when they make gauges, they set the indicator to read 0 PSI at atmospheric pressure, so the user doesn't have to subtract anything. Therefore anything shown on the gauge is the actual source pressure. Do you do that math also when you put air in your tires?
Now why spend so much time trying to show me I'm wrong? Seriously, a surge map? DubVBenz just wanted to know why he wasn't getting the 29LBS of boost that Mercedes states in their tech manual at Strartekinfo.com. So is Mercedes wrong also? The vehicles are out there and running fine worldwide. I have one and it gets up and goes when my right foot hammers down.
Anyways, if you must test my expertise with turbos, here goes. I will even use your surge map if OK with you.
First formula you need is to find CFM: CFM = (L x RPM x VE x Pr)/5660
L is liters. 3.0 OK with you? And a diesel Volumetric efficiency of 90% still OK? And can we say that the engine should be at full boost by say 2200RPM since it redlines around 4000? (Most tuners like to see full boost by half the RPM range.)
Next calculate the Pressure ratio (PR) (14.7+29PSI of boost)/14.7 which gives a PR of 2.972. So plugging these values into the CFM formula gives a CFM of 311.90 or divide by 14.27 to convert to your charts lb/min reference of 21.85lbs/min.
Now check this out, the airflow of 21.85 (x axis) intersects 2.97 (y axis) at the 74% efficiency island trace. WOW!! Excellent job Mercedes. 74% efficient at 29Lbs of boost shows the turbo is PERFECT!!! Not overheating the air it is compressing, not in the surge area and full boost comfortably where most people need it. I am not even going to bother with the several other errors in your post. Entertaining reading though.
Oh, few more things, the BMW 335D uses 2 turbos to make 25 more HP than Mercedes in the 3.0 class. That's a "significant" example? Oh, and does the non turbo Nissan V6 make 455 pounds of torque? Guess that's what the 29LBS of boost is for. And if compressor trim is not important, why does the surge map you posted and almost all I have seen/studied label the compressor trim level for each turbo?
Tell you what, get a hold of Mercedes engineers and tell them that there are way off base in their turbo sizing, and the 3.0 CDI/Bluetec motors can't make the power they claim or should be manufactured to make 400+HP.
Or how about just offering some insight as to the OP's low boost question?
11-16-2011, 08:44 PM
#11
Super Member
Any time. Also, thinking of buying an app like that for my iPhone. Never new they existed till you brought it up. Really neat idea. Still doing some research.
I think you see the vacuum display because we run diesels that don't use a "throttle" in the traditional sense so there is no vacuum at idle for the system to report, so it may be throwing a default reading.
I did however come across some info that indicated the reason you may be seeing a different boost readings is that the wireless system has a refresh rate that may "miss" the peak boost level and when it re samples, catches the readings that you are seeing. Sounds like a plausible explanation to me.
Later.
I think you see the vacuum display because we run diesels that don't use a "throttle" in the traditional sense so there is no vacuum at idle for the system to report, so it may be throwing a default reading.
I did however come across some info that indicated the reason you may be seeing a different boost readings is that the wireless system has a refresh rate that may "miss" the peak boost level and when it re samples, catches the readings that you are seeing. Sounds like a plausible explanation to me.
Later.
01-01-2012, 09:33 PM
#13
Member
Join Date: Jan 2010
Location: San Antonio, TX, USA
Posts: 86
Likes: 0
Received 0 Likes
on
0 Posts
98 E300
02-19-2012, 09:40 AM
#15
Modulated two stages only use two turbos part of the time. At low RPM its only the small turbo working, above 3000rpm the small turbo is disabled and the engine is a single turbo.
