heres the deal, iv been working with Tony Duncan,
former pres of street and performance (i think the
pres part is correct) on getting the formula tuned. i work at comp so this makes things easy for me that F.A.S.T. and S&P is next door.
we almost have it nailed as driveability is pretty good
and the SOTP feel is in the very likeable range.i have
2 issues im dealing with that will pretty much seal
the deal.
1 being when im at decell and then i acell i get a
kick. its not a smooth tansition.
2 when i acell sorta on the firm side and sometimes on
the firm side i get knock. id say around 3-6 counts
pending the outside temp. the warmer it is the more
likely it is to knock. i dont get any when i WOT but
that has been on the fat side a tad but that i think
will be easy to get nailed. most of the cruz is at or
pretty close to 128.i think its gotten up to 132 at
times and then as low as 118.
what areas should i look at to nail this down?we have
pulled timing and he has mesed with the coolant tables
some as well. the reason its taking so long is we make
runs with the TECH1 at lunch and then he makes chip
changes then i run the chip for a few days then make
another TECH1 run to see where we stand. being hes the
only tuning guy hes busy and has his head full of
stuff. if there were more time we would make good use
of it and nail it down.
bveing that we are close to being done were trying to
set up a time to run emulator. id like to do this on a
warmer day so tuning out the knock in hotter temps
will be easier as i mentiond thats when most of my
knock occurs.

 

Take a look at this Richard.


DECEL FUEL CUTOFF – Decel fuel cuttoff means exactly that. When you take your foot off the gas pedal going downhill or decelerating quickly, the ECM will cut off the fuel entirely. The difference between this term and the next one, DECEL FUEL ENLEANMENT, is that some fuel is allowed to reach the engine during DECEL Enleanment. As to when one or the other occurs, I don't know. I do know that on my TPI system, I noticed a lunge from the engine right around 1500 RPM, so I think this is where the DECEL fuel enleanment takes over from the DECEL FUEL CUTOFF. The lunge was significant and could easily cause you to run into the something if you weren't expecting it. I also believe a speed sensor is required for these two modes to operate period. So this is another reason to have a speed sensor.

DECEL FUEL ENLEANMENT – See Decel Fuel Cutoff above.



See you Saturday.

 

Not quite - to clarify - Decel Fuel Enleanment is basically the opposite of Acceleration Enrichment. It is only used during the time that the throttle is CLOSING - not closed. It is a reduction in the normally calculated Pulse Width which serves to keep the actual A/F close to 14.7 even though the PW is much less than the Steady State PW for that load and RPM. When the throttle is closing, the load decreases, and air pressure in the manifold reduces. This strips a lot of the wet wall film from the intake manifold, and also the fuel calculation is a little bit lagging, both making the cylinder charge rich. The DE compensates for this by leaning out the normal injections. It is a very short term enleanment, on the order of throttle closing duration + a smidge.

DFCO exiting (meaning fuel is turning back ON) is what you feel with that lunge at 1500 RPM. A way to smooth that out is to reduce the low load spark advance at that RPM, and in that general RPM - or just live with it (some systems will allow some enrichment just as the fuel turns back on to compensate for the dry walls, otherwise closed loop can sometimes see lots of lean and overshoot rich when compensating, causing other minor issues).

To the original post-er. I'd probably try to add some to the Acceleration Enrichment to make that jerkiness go away, and the knock counts might also go away. Take a few degrees of timing out of the low load (and whatever RPM you frequently exit cutoff) to also help smooth it out a little. But honestly - i'd probably ignore the few knock counts, and just focus on the drivability to a point that is satisfactory to you.

 

the "kick" i get happens anytime i accell and its like a shift kit in an automatic. its too much to deal with and makes it hard for smooth driving.
as for the knock , i cant ignor it, its VERY audiable. i know im losing quite a bit of HP because of this. when we tune im ither too rich or too lean. i can tell when its too rich because of the smell, i lose gas milage, and i can DEFINANTLY tell a difference in the way it runs. iv had about 4 people tune on it and right now its better than it has been but still not right. im getting extreamly frustrated.

 

Knock "counts" are VERY different than Audible knock. If it's audible, it's a problem, and should be fixed, like you want.

I'm guessing you have either A) Not enough Acceleration Enrichment, and/or B) Problem with the knock sensing / calibration not aggressive enough and/or C) Simply too much timing in the main spark advance table, and the knock code isn't quick enough to pull enough timing out.

Has anyone fiddled with any of the above? That's where I'd be looking. The jerkiness is probably related to the knock or vise versa. The lack of AE can cause knock, and knock retard can feel like a lack of AE/jerkiness.

Try one first - overcompensate AE on one chip to see if it makes the jerk go away, or at least change. If still knocking, it's probably too much spark advance. If you remove lots of timing in the problem area, and it still has the jerk (but no knock), add AE. Go back and forth a few times.
Use a wideband at any cost - before you frag your pistons / hurt your head from banging it on the wall too much.

 

91GTA is following this and we will be meeting sat to work on a few things.
i'v had Tony Duncan of street and performance doing the tuning over the past year and its always been close but not quite. being hes the tuning guy at comp i figgured it would be easy enought to go overthere and get things tuned.
like i said hes gotten it close or what i feel is close but being hes head of teh harness div and soing stuff with F.A.S.T. which is in the same dept his hands are quite full. he did say he wishes he had more time as he likes tuning and esp on TPI stuff.
Red should we start fresh with the stock chip or continue with what Tony has done so far?

 

BTW, in most cases it runs obnoxious when its fairly cool/cold outside but when its warmer, anything above 45' it starts to detonate and gets worse the warmer it is outside.
knocks to the point i dont wanna think about driving it much less look at the car .

 

It sounds to me like this car is a manual? If so you'll probally need to finesse the DFCO settings a bit..

You can watch DFCO cut the fuel injectors on decel with your datalogging software.. Just watch fuel PW let off the gas a bit in the problem area and then slowly touch it again. That transistion from pretty much off to on is what your feeling.. I've actually had this problem on a buddy of mines totally stock 93 LT1 hwere it was just a bit to much for that particular car.

As far as the knock .. Are you getting knock counts, actual retard, or audible knock?

If you have a datalogging cable and can take a datamaster datalog and send it to me I'll be glad to tell you specifically where you can pull timing out to make this go away. I've got a pretty neat excel worksheet I use that plots consistant big changes in knock counts (not knock retard) so that you can see the source and specific area of the knock....

I'd be happy to share it with anyone whose interested.. I made it for myself so it would probally take a bit of looking at to figure out how to use it.

 

DING DING DING, give that man a C-gar!!! thats one thing i forgot to mention about my car is its a stick.
on the knock, when we hooked up the TECH1 i would see knock and i can also hear audiable knock. as mentioned me and 91GTA are getting together sat and seeing whats going on.
to give an idea about the motor its a .30 305, mild ported heads, heads were shaved .8 (they needed to be) .20 head gasket , 480/480 210/220 112 LSA. im at 10.41 compression which would explain why im having so much knock. im running a set of SVO 19 lb injectors worked by Rich at crusin. my base timing is at 6'.
now with that combo the only time i can lite the tires (not that i need to) is when its fairly cool outside but when the outside temp is up the car dsosent feel like whats actually under the hood. im hoping we find some stuff thats been overlooked and we can bring out that HP that (i hope) is hiding.

 

Tuning with a Tech 1 is really not the way to go.... at least I have found

Its better to capture some quality data.. come home with it and review to see what happens as a whole instead of at an instance.

I'd reccomend a cheapo cable and a few logs with your favorite logging software.

 

Roost. Well be hooking up my 2 Tran interface and using Tunerpro RT.



I keep the laptop screen closed when logging to save battery and keep me from rear ending someone.

 

Hey now. Can i give it a try?