Mike00FRC

iTrader: (1)

Got the SVO 42#s in and running fine at idle. IFR was scaled stock * 183%. Anyway, at idle and under throttle, the Ltrims are great... right around -1 to 0%, however under deceleration (zero throttle), the LTrims climb to right around +18% and gradually fall.

Does this sound like an injector offset issue or could it be that my BOV is not working properly and is not bleeding off boost fast enough, after coming out of the throttle (including light throttle).

jimmyblue

iTrader: (11)

More like a "what do I calculate, when I have
squat for airflow and high RPM?" issue. I'd say
fuggedaboudit.

An injector imbalance will not cause a total
LTFT error, rather, the car will run poorly
with a nominally-good LTFT (7 cylinders rich,
one lean, average OK, nobody happy).

I would try for LTFT a little more negative, like
-5%, just for some "fuel margin" and tip-in
reserve. But that's just personal notion.

red ws6 99

Does not sound like an issue at all. If you are at WOT and suddenly close the throttle blade you afr ratio is going to go way lean. I get 20:1 afr (probably worse but wideband only reads to 20) when you are on it big time then suddenly close the throttle. This happens because you go from a high load to essentially no load.

If you had an injector offset problem you would probably only see it at idle. If you blip the throttle from idle and let off the afr will drop drastically say 12-13:1 because you essentially get puddling.

Gary

Brain Drain dx

I'm running most of Mike00FRC's LS1 edit file (IFR x 200%)and am having the same problem. I would not say forgetoutit because I am getting major bucking off the throttle. If I accellerate to 2000 then let off the bucking begins about 1500 and ltft's go to 20. Here is my log
200 175
cell 0: -0.78 0.00
cell 1: 4.69 3.91 5.47 3.12
cell 2: 16.41 16.41 -3.91 -6.25
cell 3: 0.00 -1.56 -5.47 -6.25
cell 4: 0.00 0.00 -1.56 -3.91
cell 5: -1.56 -1.56 -1.56 -3.91
cell 6: -2.34 -6.25 -1.56 -3.91
cell 7: -2.34 -2.34 -1.56 -3.91
cell 8: -2.34 -2.34 -3.91 -2.34
cell 9: -5.47 -3.91 -3.91 -2.34
cell 10: -6.25 -5.47 -3.91 -2.34
cell 11: -4.69 -2.34 -4.69 -5.47
cell 12: -0.00 -0.78 no
cell 13: -4.69 -3.91 no
cell 14: -4.69 -3.91 -4.69 -5.47
cell 15: -6.25 -5.47 -9.37 -8.59
cell 16: no data no
cell 17: no data no
cell 18: no data no
cell 19: -0.78 -1.56 -6.25 -5.47
cell 20: 0.00 0.00 -1.56 -1.56
cell 21: 19.53 19.53 10.16 7.81
cell 22: -4.69 -3.91 -3.12 -3.91
cell 23: no data no
cell 24: no data no
Does someone know what these numbers mean and where to correct them?

Mike00FRC

iTrader: (1)

Brain Drain,

I'm also getting some bucking at light throttle around 2000rpms, but now I'm starting to think that it may just be an inherant problem with having a SC. Under the conditions that I'm getting the bucking, I'm wondering if its right near a neutral boost condition... sort of a zero boost/zero vacuum. Could this cause sort of a flutter in the BOV, where it doesnt want to stay in either the open or closed position?

Also, I ended up re-flashing it with a lower IFR percentage. Went from the 183% to 172%. With the 183 I was a little too lean and started getting some positive LTerms at WOT after letting the PCM learn a bit.

Let me know how it goes at MCR

Brain Drain dx

I tried 175% first to get a -10% ltft
then 180% for -9%
then 200% for -1
and 210% for +1
these are for cruising at about 62mph - 18-20% TPC
what are your ltft at cruising?

Just got off the phone with MC Racing - their race car blew up and they are too busy repairing it to get me in for another week and a half. They did say however they the bucking will not occur in a properly tuned car.

Mike00FRC

iTrader: (1)

If I remember correctly, I was getting anywhere from -3.x to +.08 at cruise. With the reflash at 172%, I'm going to put one or two hundred miles on it and record some normal driving.

I need to do some more checking on the bucking. Once my gauges get here things should be a little easier.

Brain Drain dx

Heres my idea: Since we only get injector flow rate to play with then it must be the problem, I was watching my manifold pressure and I only get bucking when its between 5-9inHg. So I drove around and logged a bunch of data then speadsheeted it, converted to kpa then made a guess at where the flow rate should be. I need to run 200% at 40kpa because thats where my ltrims go slightly negative. I need less than x 175 at 10kpa because 175 still gives me +10 LTFTS. so I went something like
Kpa_-%_____X%
0___28_____172%
5___28_____172%
10__28_____172%
15__21_____179%
20__14_____186%
25__10.5___189.5%
30__7______193%
35__3.5____196.5%
40__0______200%
45__0______200%...
Ifrs are a little wacky but still within tolerances. Bucking is down. I think if I work on my curve a bit it will be better plus I still need lower values for 0 - 15 kpa
I still think someone somewhere had 42# injectors and know how to fix this problem...

NoGo

iTrader: (2)

The LTerms sounds like your bypass valve isn't 'passing' all of the boost back to your inlet..... not a big deal unless you decide to up your boost, then it could become a 'keep hose clamps on' problem.

The bucking is from improper tuning. My recommendation would be to try and richen up the car at the point in which you are getting the bucking. You can do this by kicking the car to WOT earlier, or playing with the VE tables.

Good Luck

Mike00FRC

iTrader: (1)

Thanks,

At 172 across the board, I'm still getting some positive LTerms in the part-load cells, although the average is negative. I'm going to try to step it down a few percent... probably to 168 and give it another go. I havent stated to tune the PE or VE tables yet. Once I get the IFRs nailed down, I'll work on that. Between the cam and sc, I'm still having some surging at idle and at 2000, in addition to the hot starts problem. One thing at a time.

Nogo,
Thanks for the info, but both Brain Drain and I are running a Bosch BOV which vents to the atmosphere. I plan to drop the VE 400-1200 to take care of the problems from the cam, but which way should I go in the 1500-2200 area? (EDITED) Got it, need to increase the VE tables in this area.

Thanks,

strokedls1

iTrader: (1)

Kevin- Which way do you multiply to richen or lean the fuel curve in the VE tables? Really appreciate you guys sharing info on the tuning...TIA -jason

Brain Drain dx

stock car 98' ltfts
Cell 0: no data
cell 1: error
cell 2: error
cell 3: no data
cell 4: error
cell 5: -7.81 -7.81
cell 6: -7.81 -9.37
cell 7: no data
cell 8: -0.78 +1.56
cell 9: -1.56 -2.34
cell10: -4.69 -5.47
cell11: -0.78 -0.78
cell12: no data
cell13: no data
cell14: -1.56 -1.56
cell15: no data
cell16: no data
cell17: no data
cell18: -5.47 -5.47
cell19: no data
cell20: -1.56 -1.56
cell21: -1.56 -1.56
cell22: -6.25 -6.25
cell23: no data
cell24: no data

avg -6.14 -6.36

Brain Drain dx

As far as I know the blow off valve stays open until manifold pressure get to no or low vaccuum(like wot or close there to) I havent even got close to that yet. But your saying maybe the valve isnt opening all the way and its messing with the airflow? My blow off valve vents to the atmosphere.

I'm not using Wot. The procedure for bucking is step on gas, say about 20% tps, let off gas when the revs hit 2000, as soon as the boost gauge bottoms out (about -17 to -19 psi) I get a light buck. then the rpms fall ... somewhere about 1500 rpms the car bucks lightly - ltft jump to +20 and continues to do so until 1000rpms. I have not tested below that rpm. The whole time I am not touching the throttle. The other way to reproduce this is to go cruise on the highway 62 mph About 1400 rpms. everytime I start going downhill the car bucks once or twice. Going level or uphill works fine...

I am dumping my %variable IFR tables for a straight one again... I'm guessing the problem lies elsewhere. It was worth a shot.

NoGo

iTrader: (2)

The Bypass valve was just a stab. If you both are running aftermarket bypasses, then most likely that isn't an issue.

As far as the bucking, here is something you could try to determine if it is a supercharger related problem. Just disconnect your supercharger discharge tube from the rest of the system (assuming you have a blow through MAF and not a suck through). Take the car for a quick spin (mind you won't be using an air filter for a few minutes) and see if you can get the car to buck. If the car bucks try logging MAP, MAF, Ignition Advance, KR, LTrim, and IPW. What you are looking for is an abrupt change or spike in either the MAP, MAF, Ignition Advance, or IPW during the bucking to point you in the right direction.

If your car doesn't buck with the hosing off, then you know it is a supercharger related problem. And if it is a supercharger related problem most likely it is messing with either the MAP sensor, or the MAF sensor. I would try logging these two perameters and check for spiking during the bucking to point you in the right direction.

Just a suggestion.

Good Luck.

Mike00FRC

iTrader: (1)

Got it. Thanks for your help Kevin, I'll give it a shot.

Mike