More results from my 3500Z!

[Superdave]

Forgot about this till today...


Here is the breakdown of power VS the AFR measured at the tailpipe.

http://www.3500z.com/3500/Misc/Dynobreakdown.jpg

I know the AFR's are rich and it's quite possible that the spark timing is too far advanced at 36 degrees. I did get 1 knock count in that run and it did pull a little timing...


Here is a datalog from that run: http://www.3500z.com/3500/Misc/dyno2.csv

[PCGUY112887]

Humm question...

When your just cruising around, how steady does your wideband stay? Even though my fuel trims stay solid, the wideband reads anywhere from 14-15.5 while just cruising. When I accelerate off a stoplight, the wideband dips to 16 or 17 then straight back to 14-15.5 range.

Also on decel, say I run up to 80 and totally let off the gas, the wideband pegs at max lean till I slow down or till I hit the gas at all.

Is all of this normal?

[Superdave]

that's pretty much how mine is..

cruse bounces between 14.0 and 16.5, full decel pegs it out to all 9's when i let off at the strip and ride the gears down (my brakes suck). When i acel from a stoplight it actually goes into the 13's then once i reach a crusing speed it levels off.


my wideband is in the header crossover so it's only running off the front 3 cyls, it might not bounce around as band if it was reading all 6. I've thought about moving it to the Y pipe, but the thought of a $50 sensor down there is a little scary.. my car isn't exactly high off the ground.

[sprucegagt]

Humm question...

When your just cruising around, how steady does your wideband stay? Even though my fuel trims stay solid, the wideband reads anywhere from 14-15.5 while just cruising. When I accelerate off a stoplight, the wideband dips to 16 or 17 then straight back to 14-15.5 range.

Also on decel, say I run up to 80 and totally let off the gas, the wideband pegs at max lean till I slow down or till I hit the gas at all.

Is all of this normal?

During normal cruise conditions its common for your O2 to read anywhere between 14.1 - 15. The system is not perfect so it can't hold 14.7 all the time.

On acceleration you should see your wideband dip slightly richer to something in the high 13s. Since your getting 16 and 17 it sounds like your AE table needs some adjustment. Does your car bog or not have good throttle response?

I know for OBDII if you are over 50 MPH and decelerating then the fuel injectors will shut down to save fuel. That's why you see a big lean condition. Don't worry though, it's normal.

[1988GTU]

I know the AFR's are rich and it's quite possible that the spark timing is too far advanced at 36 degrees. I did get 1 knock count in that run and it did pull a little timing.

What octane rating are you using? You might be at the point that you can add more fuel without change or actually hurt performance (bog, poor fuel econ) , but if you decrease the fuel while bumping up the octane you might see better results.

[Superdave]

What octane rating are you using? You might be at the point that you can add more fuel without change or actually hurt performance (bog, poor fuel econ) , but if you decrease the fuel while bumping up the octane you might see better results.

91 (premium)


I'd like to put it on the dyno and back off the spark timing to around 28 degrees, then get the WOT fueling in order. then start bumping it up a degree at a time. Once i sell my other "toy" i should have the money to play on the dyno a little bit...

part throttle and cruse fueling is easy to fix, since i built it as a track setup i'm more worried about how it runs in PE mode than anything.

[1988GTU]

91 (premium).

That's premium?! LOL
94 over here is considered premium, but at $3.15+ a gallon it hurts.

[Superdave]

Some places do have 93 but they're hard to find anymore...

[rsisbetter]

great job dave!

[sprucegagt]

Some places do have 93 but they're hard to find anymore...

WOW. 93 is everywhere around here.

[IsaacHayes]

91 is higest we have here. And ALL the gas has 10% ethanol.

[ForcedFirebird]

91 is higest we have here. And ALL the gas has 10% ethanol.

But I thought ethanol helps resist detonation by having a higher octane rating than gas?

[IsaacHayes]

It raises octane rating, but you loose mpg. The 87/89 is the same price here because it's the same thing. 87 with 10% ethanol added raises octane to 89. The last station here that was ethanol free had to switch and now everyones cars that filled up there have had miss fires/etc because they didn't clean the water out of their tanks properly so now it absorbed all that water. Some stations even tell you don't fill up a full tank, just a little at a time so you can help them get rid of their bad gas that way.... > I got much better mileage on straight gas I would pay the extra for 89 non ethanol because a tank lasted so much longer and end up being cheaper. (I had to run 89 in summer or I got pinging and KR and power went out the window)

[ForcedFirebird]

It raises octane rating, but you loose mpg. The 87/89 is the same price here because it's the same thing. 87 with 10% ethanol added raises octane to 89. The last station here that was ethanol free had to switch and now everyones cars that filled up there have had miss fires/etc because they didn't clean the water out of their tanks properly so now it absorbed all that water. Some stations even tell you don't fill up a full tank, just a little at a time so you can help them get rid of their bad gas that way.... > I got much better mileage on straight gas I would pay the extra for 89 non ethanol because a tank lasted so much longer and end up being cheaper. (I had to run 89 in summer or I got pinging and KR and power went out the window)

You can add xylene or acetone to up octane. 3oz per 10 gal.

[34blazer]

yeah xylene has a octane rating of 117 i think, heres a link on mixing for octane.....http://gnttype.org/techarea/misc/octanebooster.html

http://gnttype.org/techarea/misc/Octanemix.html

http://gnttype.org/techarea/misc/octaneexplained.html