Backed my timing off - lots more driveable

[GRGT1994]

Just thought I'd post this for all the folks that have done an HCI swap recently (or doing soon).

Ever since I did my build up this summer (see sig), I have had a pretty rough idle, bucking from 1,000 to 2,000, and the idle/surge/die. I tried playing around with timing and the IAC, TPS, etc. etc. That helped a little. But on the timing, I started at 10 degrees advance, and went up. I went that direction mostly because AFM suggested my B-31 cam would probably perform best at 14 to 16 degrees.

Well I finally got curious enough to see what dialing the timing back down a bit might do. I started by dropping back down to 8 degrees. Wow. The idle was much improved, and the engine ran smoother and sounded tons better. Plus the bucking was toned down. Then I dropped down to 6 degrees. This seems to be my sweet spot. Now there is NO bucking, and the engine sound musical. Mmmmm long tube headers .....

Anyway, I was curious to see what that might do to the power I'm getting out of it. Seat of the pants feel is not quite so brutal, but that might be just because the engine is running so much more smoothly. So I fired up the Gtech. Before this last round of tweeking, the best 0 to 60 I ran was 5.6 seconds. On my first try now, I banged out a 5.1 with a crappy launch. LOL. I can't remember what my other stats were, but I think they all showed similar improvements.

Needless to say, I am quite happy with the way its running now (just need to reset my lower intake - another story). So keep that in mind for anyone working on tuning. It never hurts (I guess) to try moving in the opposite direction (a bit) from where you think you should be going.

 

[95GTV8]

that's very interesting i need to set my timing soon, and i'll remember that.

 

[Methodical]

That's interesting because I recently discovered the same thing while tuning my car. I tune my car using the TwEECer and I had my global spark adder set to 4, which gave me 14* timing. Global spark adder is the same as turning the distributor to 14*. Idle was good but I always think I can get it better. At that time in the tuning process, I began tackling the spark tables. I noticed the spark tables timing is high at low loads - up to 43* So with the added 4* I was getting upward of 47*. Later I found, via research, that cars need lots of timing down low to help idle. I decided to see what effect putting global spark adder back to 0 - thus putting initial timing back to 10*. Immediately, the idle was better. From that point forward, I've only adjusted timing for Part throttle and WOT using the Base Spark table and leaving the low end of the table for idle to stock settings. Currently I have timing set to 36* from 2500 rpms up in the upper loads of the Spark Base table and everything seems fine. Have you've tried 10* - factory setting - for your test. Glad someone else sees what I've see.

By the way, what is GTech. Peace

 

[HISSIN50]

That is a great to hear that it is running better for ya.

You bring up a good point that I am sure you know - there is a point where one can advance timing too far and reduce power output, but before the onset of detonation. No real need to run on the ragged edge of detonation - not that you were at all, but others do.

That is a nice 0-60 time.

 

[final5-0]

I don't find your improved drivability results from less spark surprising at all.

Yes, I can assure you, wot power was given up for the newly found improved drivability.

As Methodical talked about, he has found the same kinds of things with his combo.

Rule of thumb only info follows as each combo can be different.

Most peeps I've seen on the tuning boards and I've talked to about this topic say they, like me, have found this general kind of thing.

Spark table adjustment is ........

upped in high load rows for wot power
lowered in low & mid load rows for help with the ping thing, bucking, surging, or drivability stuff.

If you don't have access to the pcm then you just play with dizzy, and fuel grade choice for best compromise of all driving conditions.

Grady

 

[GRGT1994]

Looking back on it, I think my timing was way too high at 14 to 16 degrees initial timing. I say that because now I am pretty certain that I had some significant detonation at that level. Being pretty green as a shade-tree wrench, I really didn't know what I was listening for with engine knock. Now that it's gone, and it run so much better, I am convinced that the ticking or clicking (not quite as high pitched as those words imply) that I heard at WOT - especially in 3rd gear - was knock/detonation.

Methodical: Thanks for the insights. You are clearly way over my head with the spark tables etc. I think this winter I will get a tuner (prolly PMS), and start reading up on higher level tuning. Oh and a Gtech is a small radar detector sized device that is driven by precise accelerometers that measures acceleration and engine power output. Search for some other threads on it here and you willl find a bunch. It will even give you a simulated dyno graph, so you could really use one of these with a TwEECer or PMS pretty effectively to tune for WOT power.

Grady: In my case, since I was so over timed (detonation) I don't think I gave up any WOT power. The Gtech confirms, and actually indicates a big improvement. My task next spring, after getting the PMS, will be to learn up on tuning and really dial it in.

I'm planing to use the search and come back to you guys and others to really learn about the higher level stuff (spark tables, fuel curves, etc, etc etc) over this mod season (Michigan winter).

:SNSign: :Teh-Win:

 

[final5-0]

Grady: In my case, since I was so over timed (detonation) I don't think I gave up any WOT power. The Gtech confirms, and actually indicates a big improvement. My task next spring, after getting the PMS, will be to learn up on tuning and really dial it in.

I'm planing to use the search and come back to you guys and others to really learn about the higher level stuff (spark tables, fuel curves, etc, etc etc) over this mod season (Michigan winter).

:SNSign: :Teh-Win:

Luke ... Luke ... Your slipping over to the Dark Side of Self Tuning

I've really had a lot of fun making that little Silver Box reveal its secrets to me.

Not doubting your word here

but

I find it hard to believe you have your dizzy at 6 and you did not notice a loss of get up and go

btw, the PMS looks like the easier way to self tune from all the stuff I've seen about it on this forum.

Hey user friendly is good!

I guess for me ...... There is enough geek in me to not even consider doing without all the hard data you get from Datalogging so I'll stay with the older, manually manipulate the pcm values your self technology

Grady

 

[Pokageek]

Awesome thread. This was going to be my next concern as well.

 

[CManT1914]

Hmmmm.......... *runs out to stang to change timing, realizes doesn't have laptop with him* I'll have to try this later. Glad to hear your stang is running a bit better!

 

[Methodical]

Oh and a Gtech is a small radar detector sized device that is driven by precise accelerometers that measures acceleration and engine power output. Search for some other threads on it here and you willl find a bunch. It will even give you a simulated dyno graph, so you could really use one of these with a TwEECer or PMS pretty effectively to tune for WOT power.
:SNSign: :Teh-Win:

Cool. I will do a search and check it out. Peace