Help - major discrepancy 'tween FAST w/band and dyno w/band

[Pro Stock John]

Facts: FAST bank/bank system, on an LS1

On the dyno, the FAST w/b is reading 3 full points richer than dyno w/b. At part throttle it is 2-2.5 full points richer than dyno w/b. We can tell that the FAST w/b is the one tthat is off.

Other FAST'd cars have been dynoed on the same dyno and the w'bs have been spot on...

Anyone seen this? I have an RMA to retun everything to Memphis for inspection but I am about to miss three track events now and if there was a fix that i can do I can maybe make an event or two...

PSJ

 

[86brick]

I hope you get this problem solved John...... I'm curious to see how your LS1 beast does!!!

Good luck and I'm sure Lance or Craig can help you

 

[Pro Stock John]

I"m sending it all back for inspection on Monday unless someone has seen this before and has any ideas.

I have dual exhaust and we had the FAST w/b and the dyno's w/b on the same side for the last half of the testing.

If the discrepancy was .5 or less I would not care but 3.0-2.0 is far too much.

The FAST itself was working just fine and the car idles beautifully... Lean in, turn the key and the car starts... 83 lb Siemens and all.

 

[96Z28SS]

I work at a dyno facility and I have seen this before. It was the Dynojet wb O2 sensor. Dynojet has changed their O2 sensor pump 3 times in the last 2 years. We have the latest dual pump.
We were having problems with the O2's.
With a new sensor and tube I have seen the FAST wb and the Dynojet wb be within .25 to .5 of each other.

I would ask if they have a new O2 sensor handy and to swap it out, also when was the last time the tube that goes in the tailpipe for the 02 replaced.

How did you come to the conclusion that the FAST system was wrong and the Dynojet was correct?
Was your car blowing a ton of smoke out the tail pipe being rich?

I don't know how easy it is for you to get back on the dyno but put the Dynojet wb O2 in a bung instead of the tail pipe. You should have an extra bung somewhere cause the fast has only one.

I wish I could help ya more but this is what I have seen.

Rob

 

[Pro Stock John]

Woostah in the hizzouse... I am from Quincy MA.

Umm, Intmd8 changed the filter and we all felt it worked fine. I can ask but the car ran rich when the dyno w/b said it was rich, the car responded better to the dyno's readings.

Frankly the fast w/b was off on a linear basis about 2-3 full points so I'd rather have it checked that guess at it.

Next time we will simultaneously compare but plugging in a $2200 Autronic W/B on the driver's side so we can get three readings.

 

[96Z28SS]

You in Quincy?? Or Chicago? If you were in MA right now I'd say "Why don't you stop by our shop then, we'll be there all day on Saturday.
And Quess what!! We have a F.A.S.T dealer right next door! Isn't that cool. "

Rob

 

[Pro Stock John]

Naw, I live heah now but I went to BC High and then came out here for college.

Turns out Intmd8 put another FAST car on the dyno and the FAST and dyno were the same.

So my FAST w/b is funky.

ZBass28 pointed out, could it be a VEGOS issue?

 

[Craig Smith]

I've gone over this before, and I still maintain that you shouldn't necessarily expect that sticking a piece of 20 foot copper pipe up the tailpipe and screwing in a WBO2 sensor in a bung in the collector are going to produce the same results. If I had a dime for every time I have heard this about the FAST vs. Dynojet O2, I'd probably have... well, over a dollar. Maybe two.

With no exceptions, every time we have done testing to see what's going on, everything checks out just right. At low engine speeds, there tends to be a lot of reversion in the exhaust, and this will easily cause the things you are seeing. I do not believe you have a problem. How do the two sensors compare under a load or at higher RPM? O2 sensors are going to have some amount of inaccuracy when you have big exhaust, big cam, and little exhaust flow with plenty of reversion to boot.

Off to the Outback for a steak and a beer.

 

[96Z28SS]

Craig,
I agree with you the Dynojet wb should be screwed into a bung for better accuracy. The copper pipe in the tail pipe doesn't always work especially on blower cars with lots of boost.

John don't you have some family to come back too, bring the car! j/k

Rob

 

[Pro Stock John]

(My cousin and uncle still live in Brookline but we are not that close)

The dynojet sampler and the FAST w/b were located very close to each other.

I think I am making sense, I am saying that:
-FAST ecu takes changes perfectly, works perfectly
-Car's ECU works fine
-Dyno was working fine, was subsequently tested with TWO other cars that have FAST and both were within .1 of the Dyno's w/b

So the FAST w/b is so far the only part that acted weird.

We had four people working on it for two hours so let's give people some credit here, two of them use FAST and all three of those guys make over 700rwhp.

Like I said, next time I have access to a $2220 Autronic w/b so I will compare all three readings.

I have a lot of resources.

 

[Otto J]

My expierience on a dynojet showed these results. My car on a tune of 11.6 to 1 across the board showed 12.5 on the dynojet. THe EGTS were around 1710. I then richened MY a/f to 11.0 to 1 and the dynojet showed 11.8 to 1 and my EGTS were around 1580. BUT he kicker here is the 60 or so horsepower i picked up by setting MY a/f to 11.0 to1. Now i dont know whose is right but i going by my egt and horspower output. SO i have told anyone i know dont always go by " everyone tunes for around 11-8 to 1 or so" because that might not be right for your particular car. and location of the O2 sensor.
Otto

 

[Pro Stock John]

Had a very good dialogue with the FAST folks, I went the ECU and w/b sensor back and they did an extremely thorough job of checking everything.

We're going to swap the jumper harness just to see what happens, and do some more testing.

Could be reversion too.

How much could reversion affect a car at 1500-2000 rpms? And at idle?

 

[monte_383]

You have your WB plumbed before the turbo or after? and how close is it to the turbo? Some folks have been having trouble with the sensor being too close to the turbo and getting erratic readings on account of the heat. Others that have it before the turbo have said they don't respond well due to the extra exhaust pressure. Some of the vendors reccomend placing the sensor downstream of the turbo 12-18" so the heater functions properly and the sensor doesn't "overheat". Dunno if that helps, just sharing what I've read. HTH's -Chuck

 

[Pro Stock John]

Thanks for the input... I have a LS6 9:1 motor with a Vortech YS Trim centrifrugal supercharger, so I am running LS1 headers.


My FAST w/b is screwed into my passenger side 02 bung, where my stock o2's would have been.

Here is a link to pictures of my setup:
http://www.ls1tech.com/threads/show...92808&page=0&view=collapsed&sb=5&o=31&fpart=1

 

[Chuck Leeper]

IDEA??

Here's a bit of info and an idea from the folks at Innovate O2 tech site....
High-temperature applications update

The Bosch LSU4.2 wide-band O2 sensor (shipped as part of the LM-1 kit) is rated to operate at an exhaust gas temperature of < 1300 degrees (F), and a sensor housing temperature of < 900 degrees (measured at the bung) for maximum accuracy and control. When either of these operating temperature ranges is exceeded, the sensor can no longer be accurately controlled. Further, operating at or over these temperatures for any length of time can significantly reduce the lifetime of the sensor. The LM-1 is designed to display an error message under these conditions (currently 08- Sensor Timing Error) rather than provide inaccurate readings. For some turbo vehicles, rotary engines, and other setups, this error message can be encountered with annoying frequency. Some tips to avoiding the sensor timing error:

1) Move your sensor bung as far downstream as possible. Right before the cat, or 2-3 feet from the end of the tailpipe are good locations. 6” from the turbo is generally not an optimal location.
2) Some users have had great luck with a self-fabricated simple heat-sink fin. This works because it assists in cooling the sensor body. Take a 4-5” square piece of copper (optimal) or aluminum, and punch/drill a hole just big enough to fit over the threads of the O2 sensor. Bend it so that there are two “wings on either side of the sensor. Mount the heat fin between the sensor and the sensor washer.

 

[Reginald West]

Chuck thats some good info.I posted here a fews weeks ago about the temp these wide bands were designed to operate at but I did not get any feed back.I called fast because I suspected that my 1900 degree exhaust gas temp was causing the wide band to jump from 11.5 to 9.5 in a 50 rpm range. The reply that I got from them was that it was designed to work at those temps. I still have my doubts. You don't happen to have a picture of one of those heat-sink fin's your talking about do you?


REG

 

[Chuck Leeper]

Sensor temps

Reg, 2 good sites here.
www.innovate.com. They have a tech newsletter they e-mail you. It's free, and could be of help. I have no pics, but they may.

Also, here's some info on WB sensor use. It's from the Aussie site that makes the DIY kits.
It's called www.techedge.com
Here's what they say:

Wideband Sensor Positioning
The wideband sensor must be carefully placed in order to prevent damage to the sensor itself and to maximise accuracy. Also, if you use the sensor's output directly (via the simulated narrowband output) to drive your ECU then you should be doubly careful. Please follow all of these "rules" :

The sensor should always be placed on the engine side of a catalytic converter, unless you are testing the effectiveness of the convertor itself.
The gas temperature to the sensor should never exceed 850 degrees C (about 1560 degrees Fahrenheit).
The sensor should never be run without power to the WB unit (a hot sensor burns off carbon residues)
Always have the long axis of the sensor perpendicular to the gas flow (stops sensor clogging)
Position the sensor vertically or at most between 10 o'clock to the 2 o'clock position (this avoids cracking the internal ceramic structure should moisture condense internally)
We don't recommend using a short sections of exhaust pipe shoved up your tailpipe. A specially welded additional bung is the best mounting strategy.
The sensor reads the partial pressure of gases in the exhaust and infers the AFR, rather than by measuring some magical AFR directly. This may be an issue on forced induction, and in particular, on turbo-charged engines.

AFRs will indicate richer than they are, causing you to run leaner than you think.
Lean AFR's will be richer (or less lean) than indicted.
A solution is to ensure you locate your sensor away from the turbo, and certainly on the exhaust (low pressure) side of the turbo rather than the engine side.


HTH, back to cussin at my HEMI!!

 

[Reginald West]

Thanks Chuck I will check out the 2 sites.

REG