been trying too tune my 7747 with prominator in my 82 crossfire.-getting a surge and not sure what too change in tunerpro., or look at.--as driving you get feeling of e brake being applied on/off, and if you rev eng up in park you also get idle flare of about 400rpm, up and down.[doesnt seem too be AIS, MOTORS]---ANY suggestions would be great.

 

Make small changes, write notes about the results, look for trends.
Try adding a little fuel and see what happens.
If that doesn't cure it, try taking a little timing out.
You always want to *risk* going too rich, or retarded, rather then risk too lean or too much timing. Safe is always a good starting point <G>

 

thanks, -----i just raised my bpw setting too richen and seem too have little affect, on the surge. -also timing seem too not effect. ???----been chasing the tune forever here. going nuts. as example if i try too get blm in line it runs like poop.---and just so you know when i raised my BPW FROM 99 too 117 , the blm seem too not change, ?????? any suggestions anyone.----eng is a 355, stock stroke, stock 82 vett injectors, 20 psi fuel,-If my bpw caculations are right, i should run about 99bpw. ? am i right.

 

The first thing you need to do is balance your TBs. You may also have a vacuum leak somewhere. There are alot of IAC parameters that need tweaking. The first thing to do is capture data with WinALDL to see what your IAC counts are. From there you should be able to tweak them. There are posts on this forum that have good info on the IACs. Do a search and you will be able to find it.

 

thanks, ill recheck, the balance of the tbi, but had done that a year ago. and they havent been touched since.--also ill look for vacumm leak.--but didnt have the symptoms i have now untill i went prominator.-----Also is there a diff from the asdz bin i see here and the ASDU BIN ?? THAT ARE BOTH FOR automatic.

 

I don't know if there is any difference between the two bins. One thing to consider is the 7747 is for a single TB (two bores) that have a single IAC. Crossfires have two IACs. I have read debates as to the Crossfire setup will actually flow more air because of the two IACs. Another thing to look at is what map setting your motor idles at. If it is bouncing between two cells look at the spark and VE tables, make sure the setting is the same for both cells.

How much of a RPM swing do you get when the surging is happening?

 

Carl,

I have fought the surging issue in a Xfire for sometime. HAppened when I first pumped up the FP. For me its turned out to be a lean surge. Not sure if you are using EBL or not, but my surging would begin at idle particularly when motor was cold. Sometimes it would begin at idle or when I would stop to get gas and leave the motor running. I would aso experience a surge with a raised idle throttle and no load on the motor. Especially in the 1600-2000rm range. The motor is seesawing between cells that have enough of a difference in VE% so it starts to "swing". Adding fuel helped in the idle cells.
Also in the low kPa areas. You may want to look at the Proportinal Gains tables as well.

 

i get about a 400 too 450 rpm swing elk

 

Is that at idle? My no load raised idle would get to 1800rpm and then drop like a rock to 1400. I have also been stalking a light throttle decel stumble at the 1600-2000rpm level.

 

ok, i evened out my idle ve table at the map of 30 and 40.--still a little not stable but is ok.-------but reving up in gear too say 2000 rpm the surge is still there [about 400 rpm up/down]----will test drive and see if its there. -Also elk, on the AIS motors they read 0 at idle, and ill let ya know on test drive. Pretty sure it isnt the ais motors

 

You'll find you need to add more fuel in the 30/40 kPa range up through that 2000rpm range. Again, I suggest you read RBob's article on Proportional Gain/Integrator controls. A for the IAC step being 0 at idle, that's uually where mine are. With larger TBs and more cam overlap, you want as much of the airflow coming through the venturis and not bypassed via the IAC opening. My idle sits around 875-900rpm @ 45-47kPa with a 108LCA cam.

 

I decided too try too richen the map areas as stated for my surge. -figured a quick way too richen too see if it was lean surge, was too increase my BPW.---went from 107 too 117 bpw. had no affect on surge at all.??---seems i would of noticed some change in surge if all i needed too do was richen the low map.----just drove again and found surge comes in as soon as it goes into closed loop. ??? 02 seems fine, ??? ---any ideas guys where too look in tuner pro with my 7747 ecm, aS too what too adjust. ???? new here on tuning with my new prominator.---alot on tuning stuff i read is still very confusing.

 

Carl,

By changing a constant like BPW you kept everything the same just a bit richer. The surge is coming from the delta between one cell and the other.
Its the delta that needs to be minimized. If anything, you made the delta larger on an absolute basis. Personally, I keep the BPW as a constant. I don't use it to tune because it affects everything. Whatever it calcs' to is where it stays in my bin.

 

Dominnnic, and everyone.---im new too tuning but i see there is a few diff, proportional gain listed in tuner pro, with my 7747 ecm.-and wondered what one too adjust ??- and or any more info for newby

 

Dominic: my idle surges occasionally. manual trans. i can almost anticipate when it will happen. if i deaccelerate gradually and maintain a steady lower rpm it seems not to happen. if i blip throttle at stop sign it will occur. this is all CL with BLMs around 124-128 in those idle cells. yes the iac is causing the issue. the "proportional gains" need to be adjusted so as prevent IAC to not over react. i will address this when the prominator-EBL-tunerpro-rt is all functional. should have that in 10-20 days! now in OL(CL disabled) the idle is much better even though i believe i am in OL at idle and CL elsewhere past month. i am idleing at 21 deg A on timing. i might drop that to 15 deg aand give that a try. as a side note when coolant temp low and choke timed out car never surges(800-900 rpms). once it flips to CL at 160F the odds of surge are much greater. that tells me it does not surge on richer mixtures. also one could seat the iac and run without it as a test?
edit: the underlying fueling is fine(for me). when the rpms drop below the stall speed(for any reason) the opening of iac enleans the mixture too much as evidenced on WB and the corresponding enrichment brings idle down below commanded idle speed and the "stall saver" sees that and open the iac and cycle repeats. now my setup is differrent as i use a 7.4L TBI and the pindle may be larger? not sure. that may require baby steps in proportial gains?

 

Carl,

Let me first suggest you try Grumpy's method before playing with Prop Gains.
Try adding fuel to the idle cells and dropping some timing. The surge is due to a lean/rich condition. Get some tuning under your belt then play with the Prop Gain Offset for Idle. Add some to that.

Ronny,

I know exactly what you mean. Let me suggest that you wait for the EBL. I don't have that issue any longer. Its been "tuned" out along with the no load raised idle surge that carl is experiencing. Still playing with a "stutter" at trailing throttle and low MAP right in the 1700-2000rpm range, but even that has been significantly diminished. BTW, are you coming down for Bloomington Gold this weekend?

 

dominic,-i read the article you mentioned on the propor and see where they say under certain cases that the propor, gains - may be lowered as much as half. too get rid of surge on slight cruise. is that listed in tuner pro as prop gain[vs]slow 02 error, AND prop gain[vs]air flow.-??---i lower these and car is more responsive now.----but dont want too change something i shouldnt and get way off.

 

ok, i checked my low map/rpm timing for surge[they are same][even]---lowered timing across the board,[ 2 degrees] And had no effect on low load surge. ???-----then i tried raising my ve1 table at low map [richen] and it had no effect. i give up. --if i read ve1 graft its very messy after i raise low map ??? shouldnt you keep smooth ???-------with my ve1 low map raised too try and cure they are pushing very high in #s [ 80]---is that ok ???---have ve2 at low rpm taken out.-----------im getting no where

 

Quote: have ve2 at low rpm taken out.--------

leave a value in 0 rpm. i happen to have 28. you can zero out 400-2800. i left a value in those 400-2800 of 5 as was suggested.