Quick question(s) on STFT

[WildHorse]

Little guessing game. One is the stock tune. The other is tuned. Same cylinder picked at random. Which is which, and thoughts on both.

Sponsored

 

[shogun32]

unless you chopped the throttle - sudden power off at high load/rpm trying to read them is pointless.

 

[WildHorse]

unless you chopped the throttle - sudden power off at high load/rpm trying to read them is pointless.

Why's that ?

 

[WildHorse]

What are your LTFTs at when your STFT are 12-14%

LONGFT1
4.688%
LONGFT2
5.469%

Then the log 2 mins later

LONGFT1
1.563%
LONGFT2
1.562%

 

[shogun32]

Why's that ?

any 'evidence' gets erased/contaminated as soon as you roll out of the gas, idle, drive. You suddenly stop the spark firing, coast to a stop and pull the plugs right then and there.

 

[WildHorse]

any 'evidence' gets erased/contaminated as soon as you roll out of the gas, idle, drive. You suddenly stop the spark firing, coast to a stop and pull the plugs right then and there.

Ok well, the tuned plug is the left, stock tune left.

 

[shogun32]

Ok well, the tuned plug is the left, stock tune left.

that's a neat trick.

 

[WildHorse]

that's a neat trick.

oh haha. Plug on the left is with the custom tune, plug on the right is with the stock tune. Sorry for not being specific.

 

[K4fxd]

You suddenly stop the spark firing, coast to a stop and pull the plugs right then and there.

That's why you see people stopped at the end of a drag strip with their hood up. reading plugs.

Looking at your plugs the one on the left looks to be leaner than the right.

 

[GregO]

Plug on the left is with the custom tune, plug on the right is with the stock tune.

I’m going into the deep end of the pool here so hold tight.
Fine wire electrode plugs are most accurately read by closely examining the silver color transition into black.
The General rule is only 1/3 of the fine wire electrode should be silver towards the tip while the last 2/3rd’s is blackish.
I know the old school way of reading the color of the insulator and surrounding area but unleaded oxygenated pump fuels have changed that game.

 

[K4fxd]

I know the old school way

Thats me, old school.

Blowing that pic up looking at the electrode the left is good right is rich?

 

[GregO]

Blowing that pic up looking at the electrode the left is good right is rich?

Yup
NGK’s Iridum IX’s have a bit longer electrode that would be even more telling.

https://engineering.fandom.com/wiki/Reading_spark_plugs_for_racing

 

[WildHorse]

My tuner has me chasing a vacuum leaks. Told him there is none. I suggested high STFT cause I changed the intake manifold. Even the injectors look great.

 

[WildHorse]

Everything back together. Smoked tested. Same as before. No leaks. Anybody have STFT comparison between the stock 15-17 and 18 manifold while still using the stock 15-17 injectors ?

 

[K4fxd]

I've got a comparison of the stock 17 manifold and a gt350 manifold.

No change using the stock 17 CAI and 17 TB.

Sponsored