410 SBC with FAST computer

[mimgq2]

Ok what am I missing. My car idles fine at 850 RPM when it is first started. The car runs strong and the A/F tables are showing the numbers are what I want during normal driving and when I get on it. 12.7 - 13.6. Now after I get on it and put to car at Idle I notice my cat converter is glowing a mild red and I can not get it to cool until the car is turned off and restarted. The A/F at idle is 14.6-15.2. What can cause this? Is it to much A/E? Not enough decay? I pulled the plugs and 7 are clean one has a sign of a mild rich condition. What is the best way to tune A/E.

Set is

410 SBC with AFR heads. TPIS mini-ram, headers, roller cam, 11:1 CR.

Frank

 

[Chyke]

Your condition can be caused by several things. Too rich, which it doesn't seem to be, to much retard ?? or way to lean. Are you running in N alpha or speed density(WBO2?). How is your target AF table set up. There is no reason for your car to run any other way than it should if everything is tuned appropriately. Warmed up at idle look at your AF table, where is your curser floating? What is your AF ratio? do you show any O2 correction? What are your correction factors. Look at your VE base table, where is the cursor floating? You should look for around 13.5 to 1 at idle. With zero correction. Put the car in 1st/drive what ever and what does your AF say now?, do not give it any gas. Did you data log a drive and look at the data. What are your base ignition numbers like in your table? Everything affects everything else and needs to be correct. For now leave your decay where it was preset, Good Luck

 

[Chuck Leeper]

Idle AF vs Hot converter

Two things come to mind seeing these numbers:
1. The idle AF at 14.6 to over 15 is WAAAY too lean. I'm surprized the engine idles at all, especially at 800 rpm.
2. The high temps in the cat are a sure death sentence for the cat. I see that in so called "warranty returns" at RANDOM TECH. frequently. Overheating the cat WILL melt the wash off the brick and plug it up.. in short order!! If it's a pellet type converter, the pellets will melt and stick together in a wad.

You don't say what the timing at idle is.. could be part of the problem too.
Is the engine idling in open or closed loop??
AE table is not in the calcs when idling.

 

[Chyke]

Chuck, I completely agree. My intent is to urge people to know there way around and why they are changing settings, not just fix one problem. He also indicated some challenges after a drive. Just want him to tie it all together.

 

[mimgq2]

Base Lined

Here is what I have-

Compression test all cylinders 200lbs (exactly)
Sparkplug gap .041
Base timing 6° BTC
Fuel Pressure 40lbs on #30 injectors

The car runs fine. When I come off a hard run the converter may look a mild red then be ok after some time.

I notice at night (blackout) the car spark plug wire glow in areas that touch metal. (Is this normal or are my wires leaking)

If I shut the car off then back on the converter is red, until I take a ride. This I think would be start up enrichment.

 

[bobc455]

My thoughts:

I'm surprised you can idle so lean. I would have guessed you should be more like 13.5 - 13.8 / 1. If the engine really likes it there (which would surprise me, but every car is different), then fine- in theory you should go as close to 14.7/1 as you can without the engine running funny (surging, etc.) or getting too hot.

I'm surprised your WOT works well so lean- I would have guessed with that setup you'd be more like 11.5 - 12.0 /1, especially with 11:1 CR and a roller cam (which I assume is fairly big). You are using race fuel, right?

I also wonder if your injectors are too small- don't know for sure what HP you're making, but I would suspect you need more injector. If you record (log) a WOT run, what is your injector duty cycle at high RPM? If you're over 85% (which I bet you are), then you need more fuel (assuming you have adequate fuel pump). Also, is your VE table fairly close or are you getting a lot of O2 correction?

Glowing red spark plug wires?!?!? That don't sound right! If your wires are bad, typically you'd see little lightning bolts zapping around in there, they shouldn't be glowing red! Do you need bigger wires with less resistance? Even if you have big wires in good condition, then get them away from the hot metal (or insulate them)- a hot wire will have more resistance than a cold wire.

I don't think A/E will affect anything, this is only for transient conditions and won't overheat stuff instantaneously like what you're describing. Startup settings also aren't gonna heat you up either. Something is amiss with your steady-state conditions (like timing or A/F ratio when running). AE really just keeps you from bogging when you hit the throttle.

What is your WOT timing? Do you have a knock sensor? How big is your cam? What RPM do you bring the motor to (shift point)?

I bet you will get a lot more HP if you make it a bit richer, I put money on you running too lean.

I am also surprised that you run a 0.041" gap- if the car runs okay then fine, but I would think that a gap that far open would blow out the spark.

-Bob Cunningham
bobc@gnttype.org

 

[mimgq2]

Ok- The wires are glowing blue when they come near metal. I am going to re-route, trim and shield them.

You do have a good point and I think it may be the issue. I had a gap of .045, cat glowed more. then just went to .041 and I am doing better. The cat temp appears to be better. I am now going to down to .035. I think the spark may be blowing out at idle and my be dumping some unburned fuel.

the motor is pratically brand new. I just started it in the past few weeks. I just used WOT tonight and found I am running at 95%. As a result I am on the lean side ~13.4 and want to go to 12.5.

 

[bobc455]

95% means you are running out of fuel- I bet in this case that you need bigger injectors, however don't overlook the possibility that your fuel pump may be undersized or may not be performing to it's rated capacity (I've had the latter problem many, many times!!!).

If you posted the other info (cam size, etc.) and a guess at HP, we could calculate the injector size you need- I bet you need at LEAST 36#, and probably 42# or even 50#.

It sounds to me like if you get this straightened out, your motor will produce a LOT more HP than it does now! (Hopefully without stuff glowing red, either).

One other note. I don't think the big plug gap will hurt you at idle- only at WOT. I don't think plug gap will help this situation now, but I think the problem would surface once you start making the HP that I think you're capable of (in the form of a top-end miss or something).

-Bob Cunningham
bobc@gnttype.org