Tuning a 93 3.4 Firebird

[tkoforpresident]

i just put it up in case you should want/need it, and i know other people out there will use it as well.

i really don't want to count the number of ADS/ADX that mark has put on the TP downloads page that were made by me....

lol, someone will definitely find use for it.

[60dgrzbelow0]

In fact, the reason why went with John's radical camshaft on the second build, was because my 260H was not loping at ALL. Try to figure that one out because I couldn't and I spent weeks asking around as to what exactly made a camshaft that was supposed to lope "note lope at all".

I was poking around after you raised the question of "Disappearing Lope" and found this interesting formula on a Chevy V8 site forum on how to calculate what the lope might be and define its extremes based of the overlap of the Intake and Exhaust cycles between cylinders. Since their focus was on eight cylinder engines, I'm not certain the numbers would work on a V6 engine though, so the calculation factors might need some tweaking to apply for our engines.

Intake Duration + Exhaust Duration, divided by 4, - Lobe Separation Angle x 2

I suspect that the two most significant factors in the reduction of Lope are: (1) The ECM/PCM is doing its dead level best to smooth things out based on low RPM sensor readings and (2) The mere fact of having two less cylinders would reduce the "lumpiness" behavior of the cam at idle.

[bszopi]

I would suspect you need to replace the 4 with a 3 in that calculation.

[60dgrzbelow0]

I would suspect you need to replace the 4 with a 3 in that calculation.

I was thinking the same thing... But imagined I might be wrong only because of our engines being "4" Strokers. But it makes sense now... and it might be interesting to see a chart on how that "lumpy" behavior comes and goes, depending upon the cam designs moving up and down the RPM scale and at what point in these shifts for various throttle responses are when they go from being "lumpy" to glass smooth. I wonder where Buffalo, NY is on the altitude scale from sea level...you know...would the PCM calculate in atmospheric pressure in all of this, too?

[60dgrzbelow0]

By the way Brad... Back in the 70s-80s..."BK" time (Before Kids)...I had three Mustangs at the same time: (1) 1964.5 (With a Falcon Dashboard!!!! and that "Pre-289-302 Era" 260 CID Engine; (2) 1967 Completely Restored, Powder Blue with a Sweet 302 CID Motor (3) 1968 (NOT the Fastback "Steve McQueen-Bullitt Version) with an Inline 6 Cyl. Engine. So when I see your Ford/Chevy Hybrid Images.... it brings back a lot of memories...

[60dgrzbelow0]

This will be MAX (at Idle)...after he solves all these Tune and "Lope" Issues...

[tkoforpresident]

lol Bob...

while we are on the subject and having nothing more to add to that of tuning for a little bit at least, i wouldn't mind getting into this mystery.

First off, I can think of about 5 youtube vidoes of people running the 260H in their 3.4's and having a good amount of lope at idle. If i was at a computer where i could listen to audio i would post some up (i will do it later).

I emailed Comp Cams when my cam wasn't loping and this is the response i got:

"sorry your cam isn't loping, it would appear you need a bigger/lopier camshaft for your application"

that^ infuriated me.

let's look at the options here on why it wouldn't lope possibly:

1. I installed the camshaft wrong

Ok, maybe if the car wasn't running right after the install i would have some doubt, but the car ran PERFECT, no misfiring, no stalling, nothing wrong at all except the lack of lope.

2. My modifications afffected the amount of lope.

I can see this... because at the time i had heads that were ported by John, and ported upper and lower intakes but besides that my modifications were the EXACT same as zahn aka funkz (some of you may know him). And his cam loped like a beast. I will try to find his vide and post that up as well.

I don't even really know how much a set of ported heads/intakes would affect cam lope, and to be quite honest i still don't know what else (besides the cam itself) affects cam lope.

3. A vaccum leak was causing no loping.

- When i tore down the engine a second time i found the intake valley vaccum hose cracked (slightly) at the cap where it fits onto the plenum. Was this affecting my engine? The engine was idling perfectly at 1,000 rpms at idle and i didn't see any signs of a vaccum leak prior to taking the engine apart. But i've been told that if vacuum is messed up it will affect a camshaft's lope.

4. Wrong camshaft

Pullling at straws, but maybe Comp sent the wrong camshaft in their kit to me. I still have the cam and lifters so it wouldn't be impossible to measure.

keep in mind! no matter what was causing the camshaft NOT to lope before, John's Camshaft IS loping. So that needs to be kept in mind during the thought process.

[robertisaar]

2 things:

does this current cam have the SFI reluctor on it?

vacuum not causing lope: IDK, if i pull the brake booster hose off of the monte or GP, then start it, they lope almost as much as the Elky (which has somewhere near 300 duration, not sure if it's at .05 or adv, but it's MEAN, no torque below 4K), and they are both dead stock....

[tkoforpresident]

yes, i believe it does have the camshaft sensor that is necessary for SFI.

But once i switch over to the new pcm it will become batch fire anyways right?

[bszopi]

If its a standard Comp 260 grind, then it most likely do NOT have the SFI trigger on it. In which case, it could be causing all kinds of havoc for the stock ECM which is trying to figure out when its supposed to be firing the injectors bases on the trigger.

[tkoforpresident]

If its a standard Comp 260 grind, then it most likely do NOT have the SFI trigger on it. In which case, it could be causing all kinds of havoc for the stock ECM which is trying to figure out when its supposed to be firing the injectors bases on the trigger.

the comp 260H comes with the magnet tab for sfi. i know that for a fact.

[robertisaar]

that puts out my theory....

the 1.5 ECM will attempt to run in SFI even without a cam signal and will cause all sorts of issues... figured the injectors might have been firing completely out of phase...

but yes, it will be batch fire... not like it's an issue or anything...

[tkoforpresident]

haha well i had no clue either. But good news, the new cam is fabulous but it just needs to be tuned for. I'm willing to stop guessing about why i got no lope out of a lopey cam and start looking towards the future.

[tkoforpresident]

The tune I sent you is a stock 3.4 OBD1.5 that was converted to OBD1. Magnaflow cat back was all

Did you disable the speed limiter?

[robertisaar]

5 second fix, even if he didn't...