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Dyno testing

R

RootesRacer

Donation Time
SIVAllan said:
Regarding the O2 install, the dyno guys said they would do it but did not specify what type -- and this is totally new stuff to me.

Is a wideband O2 install somehow better than a (?) "normal-band" O2 install?
Click to expand...

Wideband O2 sensors allows accurate measurement of the air fuel mixture between the range of 11/1 rich up to being able to detect the % oxygen in the air you breath.

Narrowband O2 sensors only allow limited accuracy between 13.8/1 and 15.2/1.
When I had a narrowband (with LED display) on my alpine, I only used it to make sure it never got lean (greater than 14.7/1) since it has zero ability to detect actual running AFRs on a carburetted engines since they are almost always less (richer) than 14/1 AFR.

Are they adding a bung just for the test, or are you going to end up with an O2 meter in the car when you are done?

If you are going with a meter, dont bother with a narrowband its not worth the time or the money.

I have a wideband on my alpine right now and you wont believe how sensitive they can be for very small changes in running quality. That is there is often a big difference in the actual AFRs between 1/4 turn of the mixture screws, and dont get me going on how wonderful it is to know how far off you are on your main jetting.

Case in point, My twin 40 weber engine ran pretty good, I tuned it with the old narrowband setup, which is to say I tuned it so it was never lean.
I installed the wideband meter and discovered that the off idle mixtures went as rich as 11.1/1. I also discovered (while driving) that my "power" mixtures were 14.2/1. This means that the engine idled (set by smoothness) at 13.8, as soon as the throttle passed into the progression holes the mixture went into the 12s and 11s, then as the main circuit entered into play, the mixture leaned out to 14.2 (a bit leaner than you'd like under power).
Ideally the engine would idle where it does, run in the 14s in the light throttle and down to 13.0/1 at load.
This goes to show you that tuning blind by performance alone really doesnt work.
 
SIVAllan

SIVAllan

Gold Level Sponsor
RootesRacer said:
Wideband O2 sensors allows accurate measurement of the air fuel mixture between the range of 11/1 rich up to being able to detect the % oxygen in the air you breath.

Narrowband O2 sensors only allow limited accuracy between 13.8/1 and 15.2/1.
When I had a narrowband (with LED display) on my alpine, I only used it to make sure it never got lean (greater than 14.7/1) since it has zero ability to detect actual running AFRs on a carburetted engines since they are almost always less (richer) than 14/1 AFR.

Are they adding a bung just for the test, or are you going to end up with an O2 meter in the car when you are done?

If you are going with a meter, dont bother with a narrowband its not worth the time or the money.

I have a wideband on my alpine right now and you wont believe how sensitive they can be for very small changes in running quality. That is there is often a big difference in the actual AFRs between 1/4 turn of the mixture screws, and dont get me going on how wonderful it is to know how far off you are on your main jetting.

Case in point, My twin 40 weber engine ran pretty good, I tuned it with the old narrowband setup, which is to say I tuned it so it was never lean.
I installed the wideband meter and discovered that the off idle mixtures went as rich as 11.1/1. I also discovered (while driving) that my "power" mixtures were 14.2/1. This means that the engine idled (set by smoothness) at 13.8, as soon as the throttle passed into the progression holes the mixture went into the 12s and 11s, then as the main circuit entered into play, the mixture leaned out to 14.2 (a bit leaner than you'd like under power).
Ideally the engine would idle where it does, run in the 14s in the light throttle and down to 13.0/1 at load.
This goes to show you that tuning blind by performance alone really doesnt work.
Click to expand...

It is my understanding they are doing the minimum for testing and won't leave a meter in the car.

But I will ask.

After reading your note definately I will go the broadband route when I repeat this priocess with a header, dcoe's etc.
 
A

Armand4

Donation Time
The race shop where I had my car tested offers air-fuel ratio measurements either with a tailpipe "sniffer" or a welded-in lambda sensor, but I opted to forgo this because I didn't have any extra carburetor jets. I know that this was a foolish oversight, but the whole thing was fairly spur-of-the-moment, and I never got around to calling Pierce Manifolds.

Adding a few extra degrees of advance to the timing fattened the torque curve somewhat, but didn't change the ultimate power reading. When I cried "uncle" at 5000 RPM, the torque reading was starting to fall off, but it was still making 70 pound-feet of twist. So my 66 rear-wheel horsepower (uncorrected, but we were pretty close to standard temperature and pressure anyway) was limited somewhat by my worries about the bottom end. If I had the carb jetted more accurately, and I was to spin it all the way up to redline, I'm sure the old girl would put 70 pavement-shredding British horses to the ground. Still, 66 at the wheels is pretty good for a 1600, no?

More good news-- I scored a Series II overdrive transmission in a local Pick-'n'-Pull (really!) and the race shop owner, who has dealt with Laycock overdrives on everything from Austins to Volvos, says he can recreate the missing relays.
 
R

RootesRacer

Donation Time
SIVAllan said:
It is my understanding they are doing the minimum for testing and won't leave a meter in the car.

But I will ask.

After reading your note definately I will go the broadband route when I repeat this priocess with a header, dcoe's etc.
Click to expand...


Thats "wideband", not broadband.

For about $250 you can buy a wideband sensor, controller and meter.

I am pretty sure you can install the off the shelf AFR meter into the clock or ammeter dash (hole 52mm).

If you want to do this, be sure to tell the folks putting the bung in your exhaust to make it mount upwards at 10+ degrees per the bosch LSU4.2 sensor spec, that way you can count on having long life from the sensor you buy. Condensation kills these sensors and the angle allows it to drain. They should already know about this requirement if they regularly install wideband sensor for regular use.

Do this "wideband O2" and it will be the best $250 you will ever spend.
 
serIIalpine

serIIalpine

Donation Time
I bought an AEM setup on ebay and I've been very happy with it, I think it was 200 W/ shipping included. A friend welded the stainless bung into the Y pipe on my exhaust and I mounted the gauge in the left side hole in the dash.

I would recommend mounting the O2 sensor on the left of center to avoid interference with the clutch slave.

I've gotten a lot closer to ideal in my jetting although a fender bender last summer made jetting a lower priority.
 
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