Having problems with tune with 80 pound siemens using Gregs Dvd.

[mowton]

Ok, thanks!

However, I'm wondering why there's so huge difference between 60's and 80's in this particular table? (Short Pulse Adder)

I'm not yet ready to buy the argument that 80's are so huge, since Ford is using these in Cobrajet engines.

It's less about their size as more about their flow rate charateristics, especailly at very low duty cycles. Greg does a whole disertation on this but from this feeble brain comes the following.

Ford uses two slopes a Low and High slope to define the non-linear portion of the flow rate for their PCM's. GM doesn'r implement this technique, so Greg has developed the SPA values to be compatible with the GM PCM software.

Hope this helps

Ed M

[angrygoat]

My first question would be with your setup being FI, is your FPR manifold pressure referenced? This would help keep you IPW up at idle. I know you said you lowered the fuel pressure a little but it may not have been as low as if the FPR was connected to manifold pressure.

[ALB]

Yes have boost referenced adjustable reg.

[Torguemanagement]

Ok thanks Frost.

Has the problem been fixed ?

[ALB]

No not fixed. I have horrible bog every single time off idle and super sick of it. Hoping Frost or someone on here will share the secrets to getting these to work right and soon my patience is wearing out. I just keep looking at my 120 pound low impedence injectors and think throw those in the car . Heck with the harness clutter and already have the converter box mounted up in the car.

I am close to ordering some of those expensive 1000 or 2000cc high impedence injectors. But really want to hear from people that are running them first before put out that kind of money. I wish I could just run the 60s but would likey need to go to 100psi to be able to support my power levels. Looking at 1000rwhp this season as top level but 800rwhp for daily driving type of range.

[mowton]

Is the bog off-idle a lean condition? As I stated above, we tried these in a 2003 A4 Vette, big cam, procharged and had an off-idle tip-in bog as well. Also if you just touched the pedal and were llight load cruising you could feel a low level buck. The injectors were at about 2.5/2.7 ms or so if I remember. I was actually thinking about inputting some SPA in those area's to see if it would help. But the customer took the car back, said it was good enough....was getting impatient

One of the things I notice though is in the 2007 setup (also referenced above) I erroneously set the min pulse to .8 instead of the 1.1...don't know if that has anything to do with the great idle on that setup.

I don't have any answers, but feel your pain. The bog we had doesn't sound as bad as the one you are experiencing.

Ed M

[Mike@ADS]

Don't forget that the Cobra Jet also idles with about 30psi of fuel pressure, which helps out. The injectors are much smaller at that point than the 52-55psi (assuming vaccum regulator) that you are running.

[ALB]

Wanted to update this.
Frost was kind enough to send me some changes to my tune and the changes did get rid of the off idle stumble and can get the injectors to idle stoic maybe just slightly rich.
All would be wonderful but have idle surging and off idle light throttle surging.
I am not really seeing huge jumps on the tach more feeling it and hearing the exhaust note changing.
I am starting to wonder if its in the tune or something else in the car. I did find one bad plug wire and swapped it out.It helped some but not really on the surging. It was one of my nearly brand new GMPP red wires. It looks fine but you get a shock when you touch it.You don't from the other ones. Just put a stock one back in for now.

I guess might need further playing with those min pulsewidths or short term pulse adder to get rid or the surgings unless its timing thing.

Here is the current tune. I can take a log maybe next day or so weather has been horrible lately.

[Frost]

man you have been 'tuning' that car for like 2 years now! That also means that you know you should be posting a log of the incident

[ALB]

Messing around on the tune again. I know should have run log and will but mostly just messing for now. computer went dead before could save the log.

Things I tried so far today. First drove it and have no off idle bog but did have pretty bad surging at idle and off idle. Now my cam is pretty mellow 212/230/590/590 /121 and its in a 408 and had no notieable surge when ran the 60s.
All this is just since the 80s.
I turned off dfco.I turned off ltrims and I went to open loop. Set afr above 150 degrees coolant temp to 1.0. stoic.

I left timing as was in last tune but did tweak on the min pulse width and default pulse width. Set them to .699 under 1600 think it was. Left it like .896 above.
Didn't touch short term adder yet.
I then drove and idled car and played with vcm controls. I changed timing up and down. More timing just made it worse. Less timing maybe helped slightly. So this is still pointing to me to fueling issue and its the unstableness of the 80s that seems to be the problem.

I then played with afr trying 14.7 and 15.7 and then 13.7.. It still wasn't doing 13.7 maybe need to play with my ve for that but it did get rid of most of the surge and the wideband was reading more like 12.7 at 13.7 on the vcm controller.
This didn't seem to give any bog off idle and the surging while still there was less.

So guess could run full time open loop maybe. And set the idle rpm ranges to be like 12.5. This would hurt mileage I guess a bit but might be worth the trade off as hate surging.

I still plan to do more experimenting maybe today maybe next while and try to change values in the min pulse width and plan to play with short term adder some more as well.

I will try a bit longer to get these 80s to where they are making me happy.
If they still don't then out with the 80s and in with my 120 low impedance ones.

At least there seems to be ways around the terrible off idle bog of the 80s. And to repeat Gregs dvd data is pretty much useless for the 80s. For the 60s its fine. For the 80s not so fine.

I was also thinking to lower fuel pressure way way down to get them to behave but this will defeat the purpose of running the 80s in my car. I need the bigger injectors.

If you don't need them then for sure stick with 60s much much easier to dial in properly.

[robbyredneck]

why is your short pulse adder more of a short pulse subtractor?
and do you have this ?
http://www.fordracingparts.com/parts...-9593-lu80.pdf

[ALB]

Negative short term adder is one way to get them leaner at idle. And not sure what that other data is good for. This is in an ls1 where we run 58psi fuel pressure. I could drop fuel pressure way down to say 43 or 38 but that would defeat the whole purpose of running these. I need the size to run my hp goals. I can get them to idle stoic and to not bog off idle. If can get the car to stop surging at idle and off idle then will be happy camper with them.

[robbyredneck]

i think the short pulse adder is for defining the knee in the non linear part of the injecter flow characteristics .below the linear breakpoint of the flow rate adding gradually creates a c shape and gradually subtracting creates a comma shape. regardless of what pulsewidth is requested this just defines shape. just my take. ford chart says min repeatable pulsewidth is .599 at 39.15 psi. i know you say you need all the injector you can get but fiddling with pressure may give you what you need. i want to see this resolved as it is one of the most interesting threads ive seen to date. good luck ALB i'm subscribed.

[ALB]

Bit of update again. I am having some luck now with the car. I am running it open loop sd. I have idle set to 14.7 for target but its idling mid 13s or so.I havent touched ve yet to correct it. The interesting part is the surging seems gone at the 13.5 afr at idle.
I think the 80s just can't really lean down enough to go stoic and be rock steady at least I couldnt' get them to do it. But running them a bit richer seems to stabilize them.

I can live with maybe a bit worse fuel economy to have no surging. Besides you don't build a 1000 hp car to worry about every little bit of mph.

I am not sure if going to stay open loop or not but really not sure I like the short term and long term mucking with my fueling. The old cars managed to run pretty good without all this computer control.

[Frost]

.. I have idle set to 14.7 for target but its idling mid 13s or so.I havent touched ve yet to correct it. .....

I think the 80s just can't really lean down enough to go stoic and be rock steady at least I couldnt' get them to do it. ...

Some inner conflict here?

[general23cmp]

Can you post your latest tune? I also have Greg's DVD and am building a twin turbo 408. Our specs look similar and I had planned on using the 80's. Sounds like I'm in for a tuning nightmare.

[talldude68]

I had a problem with my car when I first started tuning it. It would surge at idle,low rpm, as well as cruising. Put a AFR guage in it. Set it to open loop and it was running 12.8 AFR. in open loop there was no surging. Once I put it back into closed loop it would surge. The difference in AFR the car was running and the 14.7 commanded caused it to surge. Got the AFR in line in open loop, and no more surge when in closed loop.

So in open loop running rich AFR and not fighting closed loop AFR will get rid of the surge. Not a fix in any way, just a reason why in open loop you are not getting surge. I'm sure if it is far off in the AFR, even in open loop, will cause a surge.

[Firehawk853]

Lots of good info in this thread, pretty much confirmed my own experience / thoughts on these 80lb injectors as well.

My problem is I understand the theory of what I want them to do, just not sure how to make them do it.

So on the short pulse adder, we are taking value out? Or adding? But in what range should I be looking at to focus on idle?
I assume we can do this while keeping the fuel pressure at 55psi unreferenced.

[ALB]

I have been running my car open loop no ltrims or strims for past few weeks. My idle afr is around 13.5 haven't even bothered to lean it out. My base pressure is at 58psi line off.
I have boost referenced reg.
Idle is good and no surging at idle or off ,no bogging.I realize might be losing some mileage but didn't built a 1000 plus hp car to worry about a mpg or two.
I may try to lean it out and then turn on closed loop again but really can't see why would bother. My car seems to like openloop full time.
The basic theory is quite simple. The 80s have trouble running stoic at idle at 58psi.
You could lower base pressure way the heck down to maybe 30psi and maybe they would idle better but that defeats the purpose of running the 80s.I need the base to be 58psi or even higher for my power levels.
So this open loop workaround can be a permanent fix as far as I am concerned ,unless decide to run my 120 low impedence injectors . Just hate the extra harness ,the add on box isn't too bad.

[Frost]

I have been running my car open loop no ltrims or strims for past few weeks. My idle afr is around 13.5 haven't even bothered to lean it out. My base pressure is at 58psi line off.
I have boost referenced reg.
Idle is good and no surging at idle or off ,no bogging.I realize might be losing some mileage but didn't built a 1000 plus hp car to worry about a mpg or two.
I may try to lean it out and then turn on closed loop again but really can't see why would bother. My car seems to like openloop full time.
The basic theory is quite simple. The 80s have trouble running stoic at idle at 58psi.
You could lower base pressure way the heck down to maybe 30psi and maybe they would idle better but that defeats the purpose of running the 80s.I need the base to be 58psi or even higher for my power levels.
So this open loop workaround can be a permanent fix as far as I am concerned ,unless decide to run my 120 low impedence injectors . Just hate the extra harness ,the add on box isn't too bad.

Play guinea pig for us a bit...

Post your current tune up when you get a chance; have something to try.