Hi all!

i´ve built a 396 a time ago, 195cc AFR Elim. heads, XFI 467cam (230/236@.050), single plane EFI, headers....

the tune is very good, i have near to 0 knock counts, Blm´s are 125 to 131, took a datalog of about 1 hour yesterday, everything seems to be in line.

now my question....under very light loads, the engine doesnt run quite smooth...lets say, i drive it at 50mph with 2000-2500 rpm, the engine seems to miss sometimes..no steady purr from the exhaust..

im comparison, we installled a 224/230 cam in a carbed 350 engine (that should nearly equal a 230/236 in a 396) and this engine run smooth

i also have a little hickup, when stepping very light on the throttle...thats the only case, i have this...

so, some here are running big small blocks, would you please chime in?

should i try to run open loop?

or is this just the nature of the beast?

thank you

 

You're experiencing "cam surge", which is not unusual. You need to work on the timing in the area(s) where you are experiencing it. Depending on severity, it can take some time to really dial it in. Worse case is to run open loop but with the cam you have I think it's really just a matter of patience.

 

Hi and thank you!

i experience this below 2500 rpm and very light throttle...i run up to 45° spark advance in these areas, that helped alot, but still didnt full cure the problem. maybe there are only small spots that have to be tuned...
should i add more spark?

mixture seems to be fine, plugs are nice tan in color..

that was the main thing, i have chosen this cam, tuneability...!

thanks again!

 

Not really the nature of the beast, you will need to work the tune more. Sometimes adding timing does not fix surges, but taking some away does. It also sounds like too much timing in the lower rpm range. I would ramp the timing more, in other words if idle is at 28*, ramp it to about 36*@ 1600, continue ramping to 45* by around 2200-2400.
When you are logging/tuning, go up slowly in the low rpm range. Put it in 1st gear and go up in rpm's slowly trying to stay in the same kpa range up to about 2k-2200 rpm. You will probably find some lean cells (kpa v.s.rpm), and will allow you to construct a better lower VE table.

 

I was going to suggest timing also. Just have to experiment. The 45 degree advance sounds about right. Do you tune with a laptop or do you have to burn chips? It makes it a lot easier if you can change things with a laptop. You might also be running lean at that point. Add a little fuel and see if that helps.

 

Hi all!

first, thank you for your replies...!

i have to burn chips, i also have an ostrich, but it doesnt work very good, because it seems to be very sensitive to electric noise.

i will try the first gear thing and ramp up, otherwise the tune seems to be fine, blm´s are good, but i think, you are all right, theres still some tuning left.

if anybody wants to take a look at my logfiles, or .bin files (which i would really appreciate), please let me know, would be happy to send them!

many greetings

Reinhold

 

hi all!

@mseven

i did, what you suggest me, and it seemed to help..problem is, driving and looking at the WbO2 is not so easy...

i found some lean spot when holding the to 2000 rpm in neutral, i have a Map of about 36kpa there, 43°SA, no knock, but...WbO2 shows AFR 16:1, datamaster shows BLM 115, Int. 124

the sound of the exhaust is a purring, and some popping, would say, about 1 short pop every 2 seconds..and i think, thats the same condition i experience under light load driving, except, the MAP is about 50 there...

at idle (850rpm, 55kpa Map) i run 26.7°SA, BLM are 133, Int 129, WbO2 shows AFR 13.5 :1
also, the smell of the exhaust is horrible....

@383vett

i get my ostrich to work, i have had to short the cable for the ecm to about the half, and now it works fine....so, i can emulate in real time..

i´m a bit lost at the moment, seems, i cannot get this damn thing running right....

greetings

 

Yes, care needs to be taken when driving and tuning. If it's an LC-1, LM-1 you can use the AUJP-4 hack which has an input for WB in the switches. On mine I can record the data with either the LM or in the new hack.
Other than for idle speeds, cold start, dead bands, etc., tuning in the garage above 1k will not give the desired result. When under load, 2k @ 35 kpa will be seen in decell, and is were decell en-leanment is set to start (stock is 37 kpa if I remember).
Even when going slow up the power band in gear about the lowest you will see is the 40kpa area starting roughly above 1800 rpm-2800rpm. You really need to get the data from driving and "seeing" the info as it is actually under load for those KPA ranges. Get the BLM solid first, then if there is a need to reduce fuel in decell (0%throttle), but the BLM is right under load, you can then adjust PW decay, or through the use of the other de-cell tables. For the most part, I can get the tune nailed by working the VE's (with very little to no add-ons), however this is very time consuming and patience is the key.

The issue with the WB is a bit weird. What WB do you have?
Other considerations include;
Have you calibrated the 02 sensor first before starting your initial tuning ?
Exhaust leaks ?, if any (particularly near the 02) will skew the 02/AFR readings.
If you have been using the sensor w/out it giving data, and not letting it heat up all the way every time, they will crap out. When I am using mine it is a bit of PIA because of this reason. After making sure it is not an exhaust or 02 issue, and after tuning under load do not give the desired result, you might then need to change the upper threshold values.

I usually just do some initial testing and make sure I have Open loop (cold run, not wot) AFR under control. Then I look at the BLM (closed loop) and AFR for closed loop tuning. If I need to change the threshold values, I would do it then (starting with lower threshold, off ide etc.,) After lower VE tuning is pretty solid, I will work the upper VE (including threshold values). From there and knowing 128 is close to 14.7 or on it, I remove it and finish the CL tuning. Other things I do in the tune is to not allow "highway mode" (or, you should at least change values to a more reasonable target AFR instead of 15.5:1 in the lower kpa). When I am ready to tweak WOT re-install the WB/sensor.

 

Hi!

i have an LM-1, and i´m very close to purchase another for permanently install...the question is, should i use the simulated NbO2, or hardwire the it in the ECM..if so, is this the 0-5V lead?( just looked up, both leads can be programmed)

i know, its not ideal, but i didnt have so much time yesterday, im reald glad, that my ostrich works now, so at least, this becomes a bit easier.

i have an LM-1 and an Techedge WbO2, i like both, they work fine!
yes, O2 was calibrated, i have no exhaust leaks, and i always let it heat up before..i´m very careful on my equipment.

for BLM...i have in fact very good BLM´s around 128, but driveability isn´t.

so, you mean, first tuning in open loop...when this is correct, fine tuning in closed loop...
what do you mean with threshold values?
Highway mode is already disabled.

i have so much time and money in this d**n car...

you can take a look at my .bin if you want..

greetings
Reinhold

 

Hi, just my 2 cents after having tried to fight some imperfection of driveability on my Superrammed 396 c.i vette. (1990 Speed density)
I tuned the blm to near 128 on all areas.
I tuned the idle to let it idle, I ended removing values in the 55-60 kpa range and added more timing.
The tuned again to near 128 in part throttle with VEmaster.
After this I was not happy about the little surge under 2000 rpm.
I switched to Open loop WITHOUT TOUCHING the VE values, timing, deceleration routines... etc. I only swithched to OPEN LOOP
It runs beatifully...
I believe that the stock correction (CL) is not for bigger engines with custom bigger cams.
YES, it basically can do corrections in closed loop, but (I think) that are the small corrections that produces problems.

I have a Zt2 Zeitronix that works good, very good. I tuned the WOT and it runs perfect. At idle and in part throttle I'm at about 15,5 AFR.
It runs perfect.
My next step is to tune over 5600 (I'm switching to Singleplane..)

P.S. I removed also Knock routines.. (believe me much more better..).

P.P.S. Removing OL and Knock routines are only for experienced users..
--Do not try it if you have not the right experience.--
-Beppe-

 

Hi Beppe!

sounds very interesting!

so, youre running open loop all the time now, correct?

what are the detailed specs of your cam? it seems, that we have the same setup...

what you say about the CL correction, sounds logical..maybe thats the point, that the corrections are the culprit...

i will try this also, run in open loop....how did you make it run O/L all the time? did you set the temperature for C/L to 151°C?

thank you!

 

 

Reinhold,
Upper and lower thresholds control AFR changes. Raising the number will lower the target AFR. (which will also align blm to afr). One of the other things that come to mind is have you changed the cylinder volume (tables)?
What I was referring too in Open loop tuning was getting the target afr and start-up enrich corrected. Then I actually work closed loop tuning. VE master, or any short cut method will not give the desired results. It takes time, and building the tune methodically does work. Get the lower ve locked (below 1600) then work the upper. If you try driving like normal you will picking up lean or rich places in other KPA areas. Some will be previously "remembered'' as trim cells. It takes some critical looking to make sure it didn't shift into another trim cell as to correct it a higher or lower blm value trim cell (the ecm will do this). When this happens you may be chasing your tale, as you will then be trying to correct a value that occurred in a different rpm/kpa region.

Open loop tuning it can be done a number of ways (lowering coolant will work, deleting it in switches etc.). The latest AUJP 4 bin allows OL from idle to above and then can be commanded to close loop. This dodges drive ability issues with big duration/over lap cams. Yours should not be that bad, my cam has more duration than yours (236/242)and I have no problems keeping it closed loop with excellent drive ability. I do not delete the KS...ever. The current tune gives me above 4 cts at startup and sometimes 1 -2 while driving but with no timing retard. KS controls can be modded for quicker recovery etc. On the SD cars, richer can also trigger SK's.
Feel free to PM me If you want me to look it over and a log.

 

Hi mseven!

there are some values in the .bin for idle control..i already adjusted them..i hope you mean upper/lower zero ref slow at idle, fast 02 r/l threshold at idle, etc...

also, there are the tables upper/lower zero error ref. for slow o2 r/l vs map, and fast o2 r/l threshold vs map...

cylinder volume is adjusted correctly, rpm and map blm boundaries are set to my cam...

Thats waht i thought when looking for a cam, that my particular cam should give good performance, good tune- and driveability...but.....

i also run with knock sensor, and dont want to turn it off, have modded the KS control to recover faster from a knock.



thanks for your offer, i will contact you! can you send me your emailadress via PM?

Thank you

Reinhold

 

fwiw, i got my bog out of idle transition thru the hesitant first gear lower rpm zone.

and the intro of load via clutch engagement required less finessing, apparently the motor/tune increased torque at idle, compensating for the lost of momentum when i lost the DMF, since my reverse clutch engagement was smoother, my guess the ratio was lower.

no log yet but i can't hear knock events, and the idle calmed down and wants to show 7 on the tach, nice little rump when it idles slow, best of both worlds, rump/rough idle yet transition to forward motion from stationary is hesitation free... for now

the car screams and honestly it was just a lucky guess...

 

Hi corvette90,
I replied to your PM.
I want only to say that my CLOSED loop operations were good.
The only problem was that too many fine tuning was needed to make it perfect....
I haven't all this time. So I tried to have the best possible VE values and than I switched to Open Loop.
I found it very good . Then I adjusted a bit the inj. constant and the pressure with the adj. pressure regulator. to fine tune it some better..
It ended better than better.
What I want to say is that probably switching back to Closed loop will be fine also.
But... I like so much the OL.... it feels like a carburator where you have the control of ALL loads at ALL rpms..

P.S. My comp cams is a custom grind 230int 236 ext with 112 LSA small base circle

 

how does it feel? with FI that don't have control over all loads and rpm's

will OL pass smog?

 

Hi Beppe!

thank you for your reply!

i would say, i have tuned it pretty good, i have BLM´s between 125-131 most of the time, what disturbs me greatly is the "uncontrolled" feeling in certain rpm ranges..also, that WbO2 shows different AFR´s than the car´s NbO2...clearly, when you take a look at the NbO2´s resolution....

i think, my next try is to tune it in O/L with the WbO2, than try to switch to C/L, and see if it works..if not, back to O/L...

i don´t mind, if it takes time (and more time, and money) because, i already have so much of both in it, that it just makes no mire difference...i only want the car to run without the "uncontrolled" feeling (surging, chuckling, bucking...) at lower rpm/loads...

thank you!

 

NO surging, chuckling, bucking ..on my car in OL. (only under 1500 rpm in 4th gear OD)
Check your PMs the .bin is on the way..

-Beppe-

 

Hi Beppe!

thank you very much, i will do a close compare to my .bin, i ´ll let yo know, what i came up with!

greetings

Reinhold