DanielRicany

Hey guys I have a 1985 Corvette with a bunch of mods including a Miniram. I took it to my buddy and he put some kind of tool on it where he puts a probe against the ignition wires and it gives him some numbers. We were doing this because I had some misfire problems.

He said according to the numbers on the tool that bank 1 was running lean, and bank 2 was running rich.

What do I do about that?

Is that normal with the Miniram?

All the injectors were replaced about 6 months ago.

The tune is not done yet because I've been messing around trying to get it mechanically sound.

Kinda confused, it seems like everything is going wrong.

Thanks.

MrWillys

Bank 1 vs bank 2 are always equal unless there's a mechanical failure. Without knowing what test procedure was used it is only a guess. True duals could provide a false reading it one side was leaking air after the exhaust port, or it could be a myriad of other issues.

DanielRicany

He didn't test the exhaust gases, he tested the ignition wires for each cylinder. And I think something to do with different amounts of amperage or something he was able to say that one side was rich and one side was lean.

Tom400CFI

No way that a "probe against the ignition wires" can tell what the A/F ratio is. You can compare cylinder pressures....

I'd suggest re-running this test...this time using a WB-2 sensor or EGT sensors in each side.

DanielRicany

I think he used an ignition spark analyzer.

A few wires were reading 7 - 9 Kv, and there was a few that were reading like 1 - 2 Kv. What does that mean? Thanks!

Tom400CFI

There should be two reading; a peak called the "firing line", and a much lower line, called the "spark line".

The firing line shows how much voltage is required to get the jump the gap. The spark line shows how much voltage is required to maintain the spark.

Increased resistance, increases the voltage required to jump the gap. Increased resistance is created by:
*Plug gap
*compression/cylinder pressure
*resistor plugs/ wires
*Lean A/F ratio.


So...in your case, assuming you have all the same plugs (resistor), wires, and plug gaps, then it would seem that you have a discrepancy in cylinder pressure. It's possible that you have a lean condition but more precise testing is in order.

DanielRicany

Okay thanks. So the spark plugs are new, wires were put on about 6 months ago, so that leaves compression and AFR. I imagine that more compression would increase that voltage requirement?

So it appears that I might be lean on those cylinders then? How would I go about testing the AFR for each cylinder?

Tom400CFI

More compression, or cylinder pressure increases the resistance, and therefore, the voltage requirement to get the spark to jump.



Well...as I said above;
I'd suggest re-running this test...this time using a WB-2 sensor or EGT sensors in each side.

The other thing that you could do is run it at a constant load/speed/throttle position, cut it off clean, and pull over (safely), pull plugs and read them. Same as the old days.

Cliff Harris

I'm interested in this tool and how it works. Can you get a manufacturer and model number?

DanielRicany

I believe this is the tool http://www.gtc.ca/EN/TA100_EN.html

Tom400CFI

It basically performs (some of) the same functions as an old SUN engine analyzer. It uses an oscilloscope to show spark events.

383vett

I noticed with my miniram, the front cylinders, 1,2,3,4 run lean and the rear cylinders run rich. Anyone else notice this?

DanielRicany

When I had my Miniram off I noticed something strange too. Maybe not in the same context that you have experienced, but when I blew into the Miniram with an air hose, it came out the rear 4 ports more than the front 4. I guess because it's bouncing off the rear of the plenum but maybe it has a similar effect when on the car? Or the opposite effect.

But I did hear something about the front and rear being an imbalance.

bjankuski

I have seen this also but it could be an idle issue and not a WOT issue. If you had the time and patients you could run a WB in each cylinder and see what is actually happening at all throttle positions. If you look at GM's tuning for the LT1 intakes you will see they have individual cylinder trims for each cylinder up to 15% throttle and then it reverts back to the same amount of fuel for each cylinder.

BrianCunningham

I'd try swapping sensors left & right and see if it follows

could be a clog in the lin

DanielRicany

Well it appears to be a little lean on bank 1 where the Wideband O2 sensor is.

The tuning is not done yet but I was at like 43 PSI before I changed the heads, added 1.6 Roller rockers, and ported out the Miniram.

Now I am at 60 PSI, and the AFR gauge is a little lean at times.

Does that seem strange? Or could those new mods really add that much more air?

383vett

Good points. Thanks. Sorry to hijack Daniel