924Board.org

[morghen]

i've dropped the exhaust from the turbo to the back to drill a hole and weld a nut so i can install a lambda probe in the first bend after the turbo. Getting it down was not so much pain with propper tools and some lube spray for the turbo bolts, however one of the studs from the turbo needs replacement I'm going to get it welded this afternoon and then use a digital AFR to read the signal from the lambda probe.

All this to get rid of the glowing manifold(and fine tune the A/F ratio)....it glowes if i push the car and as soon as the engine gets hot it starts poping in the exhaust when i shift gears.

i'll post pictures as soon as its welded !
_________________
Supercharger and EFI kits
https://www.the924.com

[Raceboy]

Glowing manifold can be sign of too late ignition timing.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[morghen]

yea so it is....

i've installed a narrow band today and used a LED AFR to read the lambda....and guess what...its on the rich side in ANY condition...at idle...while accelerating...while brutaly accelerating.....the decel valve also works...when i lift the pedal it goes to lean and back to its safe "green" area...so its the advance thats been causing all this...now all i have to do is find out how to set the advance on a S2 turbo..
_________________
Supercharger and EFI kits
https://www.the924.com

[RC]

With a narrow band sensor the operating temperature is critical for an accurate output voltage and therefore AFR reading. A hotter sensor will also give a rich reading. Car manufacturers and engineers go to great length to calculate the sensor mounting point for the best compromise. Generally a 4 wire heated sensor placed further back in the exhaust system, before the cat, gives more consistent readings.

If indeed your CIS is running rich in conjunction with retarded (less advance than optimal) timing the result will be an excessively hot manifold. The unburnt fuel in the exhaust ignites also resulting in backfires during decell.

Sensor temp can be checked with an IR thermometer and output voltage with a DMM. I have a hard copy of a graph that shows how the temperature can have just as much influence on the reading as the AFR. This article explains it too.

http://autospeed.com/cms/A_0618/article.html

Wide band sensors/controllers regulate the heat for consistent AFR readings under most conditions.

[morghen]

i've got pictures and videos...i'll post them when i get home.


The lambda probe that i'm using has its own heating circuit but as explained in that article...for a correct and accurate reading the temp of the sensor should be regulated. However as a debuging system this theory should work:

While its temp is climbing the sensor sends different signals giving different A/F ratios and when it gets to an OPTIMAL temp there is a small period of time when the readings are correct and accurate. RIGHT?

Well if the system would measure so much off the real value it would mean that in that small period of time when the sensor is giving correct and accurate readings the AFR device will show dramatic variations in A/F and with some tests this would be noticeable even by naked eye.


I've looked for other applications and I've installed the pobe right after the turbine, on the outer radius on the first bend. I'll try to get some measurements of the temp of the sensor.
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Supercharger and EFI kits
https://www.the924.com

[morghen]

ok...with some delay...
i've placed the lamda probe right after the turbo.



here is a picture of the AFR device connected to the lambda probe.



and here is another eyecandy picture

_________________
Supercharger and EFI kits
https://www.the924.com

[Raceboy]

With narrow-band sensor your AFR's are still just aguess what concerns full throttle conditions.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[morghen]

thanks for the input. As a natural quality/defect i never trust anything...so i've already spoke to a guy who has a wideband and a data loging system and i'm going to do some tests in different driving styles and conditions to be more accurate on the AF ratio.

hey listen...if you ever go west for any reason...i'd be happy to meet you and pay for your stay here while you install VEMS on my car and ofcourse for the VEMS install and VEMS Have a nice evening man.
_________________
Supercharger and EFI kits
https://www.the924.com

[Raceboy]

Too bad I haven't had a chance to travel further than neighborhood countries for some time But if I do, I'll notify you
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[morghen]

So...the K27 is here. Thanks Etienne, i'll send you the rest of the money right away !!

I want to make a hybrid...use the K27 compressor and the K26 hot-side as the K27 compressor gives much more efficiency.


_________________
Supercharger and EFI kits
https://www.the924.com

[Raceboy]

What number is the hotside?
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche