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Wo ist die Rennstrecke?
 
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Quote:
Originally Posted by gogomobil View Post
I like to rev it to redline and if it blows, it blows.
My boost is not excessively high with 0,9-0,95bar and 965 intercooler.
AFRs are spot on.
These engines are very solid and you should be able to drive WOT all day long on the Autobahn without speedlimit, thats what they are made for (I live in germany).

Regarding the turbo, I like the off/on power delivery of the 7006, and this turbo also doesnt loose its punch @ higher rpms. If I wanted my car to feel like a big displacement N/A engine, I would have bought a Garrett or a HFS.
Then by all means, rev your autobahn butt off....

Old 04-02-2009, 05:06 PM
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Originally Posted by JBL930 View Post
I'm told any AFR sensor should be fitted after the turbo but before the muffler, back pressure will give bogus readings in front of the turbo, not sure if this is to do with the wastegate? 3 or 4" after the turbo is supposed to be optimal, and always at a 12 O'Clock position, as if it is fitted at the bottom (6 O'Clock position) it will get fouled up
I mounted my sensor after the muff but as close to it as possible due to room constraints elsewhere. So it's about 8 inches upstream from the end of the tailpipe. The only risk is perhaps a lean reading at idle due to outside air creeping in through the tailpipe. But once past idle there's enough exhaust gas velocity to prevent any "ambient" air from reaching the sensor. Works just fine.
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Old 04-02-2009, 05:10 PM
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The AFR readings before or after the turbo are exactly the same (the dyno AFR sensor goes right into the tailpipe, my AFR sensor is before the turbo, readouts are the same), I guess the only good reason to mount the sensor after the turbo is if the sensor fails no debris can harm the turbo. If the sensor is mounted after the turbo, nothing can be damaged.
Old 04-03-2009, 02:42 AM
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Quote:
Originally Posted by gogomobil View Post
my AFR sensor is before the turbo
This will indeed affect the readings. It is not recommended. EGT's are 200 deg. lower after the turbo and backpressure before the turbo can reach 2 bar in certain cases.

Even too close to turbo is not good. Folowing excerpts are written by Klaus, who developed Innovate LM1 WBO2 logger and has great knowledge about WBO2 sensors:

Quote:
4" from the turbo is certainly too hot. Bosch specs 500 deg C max bung temperature. Shortly behind a turbo you will exceed that temperature. The heat-sink will reduce the bung temperatures.
Regular O2 sensors are designed to be heated by exhaust gases and are very robustly build in regards to temperatures. Pump-cell type widebands like the Bosch and the NTK require tight control over their temperatures, otherwise they just read wrong. That's why they can't be used like NB sensors.
With the HBX-1 the temperatures are reduced because it moves the sensor further away from the bung and cools it. The NTK sensor is less sensitive to heat at the bung and does not create errors when overheating, but the readings WILL be wrong. And it WILL be destroyed over time by excessive sensor housing temperatures that these sensors are not designed for.

All pump cell sensor pump oxygen ions from the outside air into the measurement cell (rich gas condition). Excessive housing temp not only causes problems with the internal connections of the sensor, but also causes the reference gas (air) in the housing to be of excessively low density. That changes the readings because these sensors are sensitive to that.
...and his answer to one customer who wanted to mount his sensors before the turbo, on individual runners:
Quote:
This question has come up before a few times. The pressure pre-turbo is often 2-3 times the boost pressure. This will cause errors. The way to do individ. cylinder measurement on a turbo engine is a little more complicated than n/a, but doable. You need to fab an aluminum block with holes in them into which the sensors thread in (holes not all the way through). Then feed each sensor hole with a piece of steel brake-line from each header/port with a restrictor of about 1mm in the feed. The used gas from each sensor hole is then fed back into the exhaust system with further brake lines after the turbo. The sensors don't need much gas. If you keep the feed lines short, the response is fairly good. And the bypassed gas through the feed lines is too small for the turbo to notice.
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Last edited by beepbeep; 04-03-2009 at 03:16 AM..
Old 04-03-2009, 02:50 AM
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Quote:
Originally Posted by mark houghton View Post
I mounted my sensor after the muff but as close to it as possible due to room constraints elsewhere. So it's about 8 inches upstream from the end of the tailpipe. The only risk is perhaps a lean reading at idle due to outside air creeping in through the tailpipe. But once past idle there's enough exhaust gas velocity to prevent any "ambient" air from reaching the sensor. Works just fine.

I'm sure it does work fine, like you said the only possible issue being lean readings at idle. The "Optimal" place to fit is after the turbo but before the muffler, but if there is no room then after the muffler would have to do. The most important reading for you is cruise and on boost anyway, you are not using your sensor for the ECU as you are on CIS, it's purely for observation of AFR
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Old 04-03-2009, 02:50 AM
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Quote:
Originally Posted by gogomobil View Post
The AFR readings before or after the turbo are exactly the same (the dyno AFR sensor goes right into the tailpipe, my AFR sensor is before the turbo, readouts are the same), I guess the only good reason to mount the sensor after the turbo is if the sensor fails no debris can harm the turbo. If the sensor is mounted after the turbo, nothing can be damaged.
You're wrong mate, all the experts say to fit them after the turbo, back pressure issues cause wrong readings, i'm sure there are more reasons but this is the main one



EDIT: Cheers for the full explanation Goran
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Old 04-03-2009, 02:53 AM
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Here is the sensor position on a 993tt, looks about 4" or 5" after the turbo to me, are the innovate sensors a different type to these? I'm sure Porsche know what they are doing right?

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Old 04-03-2009, 03:10 AM
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EGT should be measured before the turbo. That's the point of EGT, to make sure it isn't too high to damage the turbo. It also gives indication about how hot heads will get.

AFR should be measured after the turbo. If too close, bung should be fitted with heat shield and cooler.
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Old 04-03-2009, 03:18 AM
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Quote:
Originally Posted by JBL930 View Post
I'm told any AFR sensor should be fitted after the turbo but before the muffler, back pressure will give bogus readings in front of the turbo, not sure if this is to do with the wastegate? 3 or 4" after the turbo is supposed to be optimal, and always at a 12 O'Clock position, as if it is fitted at the bottom (6 O'Clock position) it will get fouled up
Mine is about 4" after the turbo but at the 6 O'Clock position. Problem with anything else is making it fit. Not sure how it will foul if the gasses are constantly flowing although I will keep an eye open for it.

Quote:
Originally Posted by beepbeep View Post
EGT should be measured before the turbo. That's the point of EGT, to make sure it isn't too high to damage the turbo. It also gives indication about how hot heads will get.

AFR should be measured after the turbo. If too close, bung should be fitted with heat shield and cooler.
How and where can you fit the EGT before the turbo? Mine is mounted after the turbo and I see roughly 1000 degrees F when pushing the car can get hotter in warmer weather but 1150 max is what i have seen so far. How much might I be loosing with where it is placed? It is very close to the turbo. I didn't want to weld into the B&B since they have been on the car for a while. I have never had good luck with his products after they have been used for a while. They have a tendency to crack easily. I also have a sensor for I/C output temps.

Based on the picture I posted would you recommend a heat shield?
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Old 04-03-2009, 05:40 AM
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Originally Posted by Cobalt View Post
Mine is about 4" after the turbo but at the 6 O'Clock position. Problem with anything else is making it fit. Not sure how it will foul if the gasses are constantly flowing although I will keep an eye open for it.
It gets fouled up when the car is at rest, condensation and dirty deposits etc. It will work just fine in the position it's in, but it will more than likely foul up a lot quicker
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Old 04-03-2009, 05:55 AM
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Originally Posted by JBL930 View Post
It gets fouled up when the car is at rest, condensation and dirty deposits etc. It will work just fine in the position it's in, but it will more than likely foul up a lot quicker
So for th e1-2k miles a year I drive it i should be fine for a while.
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Old 04-03-2009, 06:13 AM
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Quote:
Originally Posted by Cobalt View Post
How and where can you fit the EGT before the turbo? Mine is mounted after the turbo and I see roughly 1000 degrees F when pushing the car can get hotter in warmer weather but 1150 max is what i have seen so far. How much might I be loosing with where it is placed? It is very close to the turbo. I didn't want to weld into the B&B since they have been on the car for a while. I have never had good luck with his products after they have been used for a while. They have a tendency to crack easily. I also have a sensor for I/C output temps.

Based on the picture I posted would you recommend a heat shield?

Turbo lives of pressure differential fore/after the turbine. As gas temperature will vary depending on pressure (PV=nRT) EGT's after the turbo will be lower, depending on backpressure before the turbo. Thus, they will err southwards more and more the higher the boost (and thus backpressure) is.

Most optimal spot to sample EGT in my opinion is just prior entering the turbo. In this case, it would be in the middle of "Y"-collector.

But EGT's are "high end" and many people just tune on AFR's only and it works well. My other car (SAAB Turbo) has EGT's approaching 1700F (!) by design, due to small turbo. Exhaust is cast in Nickel-Iron alloy though.

Regarding your WBO2 being to close, I believe you are quite Ok as there is lot's of airflow beneath the engine and aircooled engines (with their long headers) have rather low EGT's. LSU 4.2 sensor can be operated up to 1300 deg. F EGT. As your EGT probe (situated just prior the sensor gues up to 1150 you are probably fine. But a little heatsink might be a good idea. you can find different designs here:


http://www.tuner-deals.com/-p-42.html?zenid=8002a2dbb299483e26c9cc6007687825

and here:
http://www.innovatemotorsports.com/xcart/product.php?productid=16148&cat=250&page=1

WBO2 sensor pointing downwards might last a shorter time if pipe collects condensation. YMMW.

Regards,
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Old 04-03-2009, 06:13 AM
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Originally Posted by beepbeep View Post
Turbo lives of pressure differential fore/after the turbine. As gas temperature will vary depending on pressure (PV=nRT) EGT's after the turbo will be lower, depending on backpressure before the turbo. Thus, they will err southwards more and more the higher the boost (and thus backpressure) is.

Most optimal spot to sample EGT in my opinion is just prior entering the turbo. In this case, it would be in the middle of "Y"-collector.

But EGT's are "high end" and many people just tune on AFR's only and it works well. My other car (SAAB Turbo) has EGT's approaching 1700F (!) by design, due to small turbo. Exhaust is cast in Nickel-Iron alloy though.

Regarding your WBO2 being to close, I believe you are quite Ok as there is lot's of airflow beneath the engine and aircooled engines (with their long headers) have rather low EGT's. LSU 4.2 sensor can be operated up to 1300 deg. F EGT. As your EGT probe (situated just prior the sensor gues up to 1150 you are probably fine. But a little heatsink might be a good idea. you can find different designs here:


http://www.tuner-deals.com/-p-42.html?zenid=8002a2dbb299483e26c9cc6007687825

and here:
http://www.innovatemotorsports.com/xcart/product.php?productid=16148&cat=250&page=1

WBO2 sensor pointing downwards might last a shorter time if pipe collects condensation. YMMW.

Regards,
Thanks good info.
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Old 04-03-2009, 06:18 AM
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Pressure and temp absolutely mess up the LSU4.x readings. Check out this info:
http://www.wbo2.com/lsu/lsu4.htm


What you see is if the exhaust is under pressure, the lambda readings can be off by 15-20%- however, by my calculations (using the given formula on the web page and the excel spread sheet) , a 2 Bar pressure @ 12.5AFR, would trick the meter to read only to read about 0.4AFR lower (12.1). 3Bar would offset the AFR by 0.5 (or 12.0) - therefore the pressure doesnt make alot of difference.

In consideration of this, i am thinking that my differnece in readings between 'WO2 in tailpipe' and 'WO2 before turbo' may have been due to mixure of outside air when the WO2 was in tailpipe - not due to pressure from the turbo. In consideration of this, I found there are several types of LSU4 sensors and some would be more sensitive to pressure/temp due to the tip configuration. I was using a sensor that was more 'open' than others - this also could have been a factor. Never-the-less, all information i have found recommend that the WO2 sensors to be placed downstream of the turbo (before the CAT) and temperature considerations to be checked.

mike.
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Last edited by mic; 04-03-2009 at 07:40 AM..
Old 04-03-2009, 07:33 AM
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Pressure and temp absolutely mess up the LSU4.x readings. Check out this info:
http://www.wbo2.com/lsu/lsu4.htm


What you see is if the exhaust is under pressure, the lambda readings can be off by 15-20%- however, by my calculations (using the given formula on the web page and the excel spread sheet) , a 2 Bar pressure @ 12.5AFR, would trick the meter to read only to read about 0.4AFR lower (12.1). 3Bar would offset the AFR by 0.5 (or 12.0) - therefore the pressure doesnt make alot of difference.

mike.
I appreciate the info.

Although the magnaflow muffler I am using is nothing more than a can and has almost no back pressure AFAIK. Spool up is amazingly fast and hard compared to having the cat in place. I don't think this is much of an issue.
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Old 04-03-2009, 07:38 AM
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That's kind of odd since they sell a tail pipe WBO2 with a wire holder to stick in the tailpipe to adjust AFR. That is after the muff and turbo. The position for the probe can be either side of 12 o'clock by about two hours to accomadate any fitting problems. The main thing is to get the probe out of any moisture that usually forms at startup and runs out along the bottom of the pipe. I tried the four inches after the turbo but had overheating problems with my LM-1.
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Old 04-04-2009, 08:12 PM
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Maybe I am wrong but why did the dyno post-turbo AFR verify my pre-turbo AFRs?

My AFRs were measured during two dyno sessions last year, they just push the sensor inside the tailpipe. The measurements are the same like my AFR sensor (installed before turbo) is showing... Lambda 1 (14,7AFR) @ idle and low to mid 10s @ midrange WOT, leaning out to 12,0 up to redline. Both AFR sensors show the same readings before and after the turbo (I went to the dyno to verify this and to check hps).

However, I understand that it is best to have the AFR sensor after the turbo, because I am scared that when my sensor fails one day it might damage the turbo and engine. If it fails after the turbo, nothing will happen.

As soon as I receive my EGT sensor I will install it where the AFR sensor is located now, shortly before the turbo, and will place my Lambdasensor at the end of my catdelete pipe shortly before the stock muffler.
Old 04-05-2009, 06:51 AM
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The turbo and muffler used will affect sensor readings before/after turbo. Good setup will reduce backpressure.



You can see in this picture the EGT probe bung below the turbo mounting flange.
My mufflers have the AFR bung locatedd a very short distance from the turbo which is not optimal but necessary due to design constraints. A quality sensor is needed and the should not be left in full time. Tuning/testing only.

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Old 04-05-2009, 08:27 AM
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When I had my 930 I placed my EGT sensor at the left bank after the collector. I had GHL headers then. Ideally having it right after the exhaust valve at the shortest pipe (assuming you don't have equal length headers) is worst case. In any case I had to replace the EGT sensor once a year, but it was only $25. With AFR's between 11.5-12.5 depending on the weather the temps would never go above 1550 deg. F.

As for my wide band o2 I wanted something that would live on a daily basis and put it right after the muffler can. You need at 10" downstream. It wasn't going to last very long right before or after the turbo. I did numerous comparisions at the dyno and it was within .2 vs. a $2k wide band.

Old 04-05-2009, 09:09 AM
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