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I am taking the car to an 80's porsche specialist, so they should have all the gauges and test gear. He is going to weld some extra boses in the manifolds to take wide band Lambda sensor for testing on the dyno.

I am still thinking it is a fuelling problem as by all acount the 69EZ seem to be pretty reliable and the vac/boost lines seem to be in good order. I have a question mark over the WUR and valve, the cold idle and start up seem pretty irregular and the revs do hang.

Any luck it's a rattle not det however I suspect it is, it's best to dyno it and be sure! Cheaper than a broken motor. It will certain give me some idea of what increase over 320bhp with the mods.

A point about the O2 sensor, I understood it was an improvement over the 930 system richening the mixture under full throttle, why would I want to remove it?

Thanks for all your input Guys
Old 11-04-2009, 05:53 AM
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The car is being dyno'd with an 80's posche specialist he has got the correct test gauges and equipment. He is going to get 2 boses welded in to the headers to fit wide band lambdas, also we will be able to check ignition timing under load. You never know it may just be a rattle, I think it is probably not though so a dyno test is a good idea. I will also get to know how much of an increase over 320hp the mild mods have gained.

I am still thinking there is a fuelling issue leaning out from 4.5k (when the noise starts) and I am unsure about the WUR and valve, the car hangs on revs and has intermitent idle speed.

A point about the O2 sensor, I understood it was an improvement over the 930 system richening the fuelling on full throttle by lowering the fuel pressure, why would I want to remove it?

Thanks again for all your input guys
Old 11-04-2009, 07:49 AM
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I am taking it to 80's Porsche specialist who are going to weld 2 additional lambda boses in the headers for wide band before the dyno, they have all the gauges etc too...

I thought the O2 sensor was an improvement over the 930 system to enrichen the mixture under full throttle, why would I want to remove it?

I still have a question mark over the WUR and valve, erratic idle speed and revs hanging....
Old 11-05-2009, 12:00 AM
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Sorry for all the blurb I had problem submitting the reply, apparently I was using a word that the system didn't like!!! Now there's 3 replies.
I'll keep you posted after the dyno next week.

Thanks Ben
Old 11-05-2009, 10:00 PM
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Quote:
Originally Posted by Ben V View Post
The car is being dyno'd with an 80's posche specialist he has got the correct test gauges and equipment. He is going to get 2 boses welded in to the headers to fit wide band lambdas
An "80's Porsche specialist" should know that WBO2 sensor shouldn't be used before the turbo but fitted after the turbo. High EGT and backpressure make WBO2 sensor fail or display wrong readings if mounted in the headers.


Quote:
Originally Posted by Ben V View Post
A point about the O2 sensor, I understood it was an improvement over the 930 system richening the fuelling on full throttle by lowering the fuel pressure, why would I want to remove it?

Thanks again for all your input guys
Narrow band OEM sensor does nothing to enrich the mixture on boost. It's disconnected during boost phase and cannot detect anything else besides if mixture is bellow or over lambda 1.0. It's only ised on idle and part load and modulates the frequency valve in order to keep mixture at lambda 1.0 so that catalyst can work.
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Last edited by beepbeep; 11-06-2009 at 02:58 AM..
Old 11-06-2009, 02:53 AM
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When it comes to fitment of lambda, I am sure they know what they are talking about, although you did cause me to consider your comments. The original sensor was fitted before the turbo in the factory exhaust (with my new exhaust it is after), if heat was a problem in this area and the sensor couldn't deal with it Porsche would have had a problem from new! The purpose of 2 sensor is to diagnose both banks individually, there could be a fuelling issue on 1 bank alone. I was looking at a gt2 race car yesterday which had sensor bungs in the headers as it was running the eqivailent to zork tubes I guess there isn't the space after the turbos.

Your lambda comments I am still unsure, although reading up on it, it does appear to play a signicant part in accel enrichment it even ups it's pulse cycle after the 66degree throttle switch. Agreed it cannot signifcantly improve fuelling but by the looks of things it will
improve throttle response by increasing the fuelling by reducing the fuel pressure with the frequency valve.

Thanks

Ben
Old 11-06-2009, 09:47 PM
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As I mentioned before, the original sensor isn't WBO2 sensor. Narrow band just flips from 0.3V to 1.4V around lambda 1.0 and is completely different design. Electronics will modulate control pressure in order to oscillate around this lambda signal threshold on part throttle and they will ignore it on full throttle. Once full throttle switch is on, CIS "mechanics" decide how much fuel goes into cylinders. You will never find a turbocharged car with narrow bands lambda sensor that runs closed loop at full throttle. Not a single one.

Bosch LSU 4.2 (wideband sensor which they will probably use) should not be mounted on turbo/pressure side. And should not be mounted with bung pointing downwards.

http://www.innovatemotorsports.com/support/manual/LM1_Manual.pdf

Quote:
On TURBO CHARGED vehicles:
Bung: Install the bung downstream from the turbo before the catalytic
converter. The high exhaust pressure before the turbo interferes with
the lambda measurement and the high exhaust temperatures
encountered there can damage the sensor.
http://wbo2.com/lsu/

Quote:
# Sensors should be placed so they are not overheated (gas temp not above 750 C, nor cooled beyond the ability of the heater to maintain their working temperature (~10 Watts).
# All pump cell wideband sensors are pressure sensitive. They should not be placed where the working gas pressure is much above or below atmospheric pressure, otherwise different calibration curves must be used for best accuracy.
Good luck with your car. I won't bother you with more posts.

kind regards,
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Last edited by beepbeep; 11-07-2009 at 02:09 AM..
Old 11-07-2009, 01:42 AM
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It would be interesting to set CO as fat as possible but not so fat that the Lambda system can not pull it back its goal AFR. Then with accel we would get our accel fuel and some additional up top.

Many run without the O2 plugged in so the Lambda dose not mess with the AFR's and then if running more boost, set the CO at idle around 3-3.5%.

For what it is worth the C2 Turbo dose have accel fuel provided by the Lambda system but only for a very short while when cold. The O2 however dose not have anything to do with this function. It would be interesting to make a simple system to trigger this when additional fuel is needed using an rpm or smart switch of some type. I believe that all that has to happen is ground one lead going to the enrichment module.

One of the weaknesses of a CIS system it is subject to un-equal fuel flows over time from age and contamination. Thus, one might think they are running 11.5AFR on boost but they could have a cylinder or two running 13/1 and the rest at 11.3 or something. It is good to do a fuel quantity test to ensure even fuel distribution.

When you go to the dyno, might also make sure you have a recent or new clean air cleaner. If they will allow you, you might try adjusting your AFR w the O2 unplugged to about 13.5 (max tq is at about 13.2 on a flat 6). Then plug the O2 back in and see if the motor pulls you back to the high 14's. If this works it should help with your off idle acceleration and fuel with the boost turned up.

Sorry, got carried away.

Last edited by 911st; 11-07-2009 at 06:08 AM..
Old 11-07-2009, 06:06 AM
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