Eisen7

I've discovered my car will buck or stutter at about 1900rpm at low load. It's not noticeable in higher gears when the car has plenty of momentum, but at low speeds in 1st and 2nd gear (e.g. in the carpark, or crawling along in traffic), the car can get a real 'hop' up and you look like a goose

Just wondering the best way to get rid of it? Just add more fuel in those cells?

Attached is a log of the issue. It's a bit hard to see where it's happening, but it's from around log ID 50 almost to the end of the log (1800-1900rpm).

EvoScanDataLog_2011.06.hopping.zip

kronik5383

iTrader: (1)

how much does your tps read at idle?? i had that problem eariler, turns out my tps was set too low, it was at 9.4% at idle, raised it to 14.1% and that worked perfect

utripin

It could be that your spark advance is to low. If your timing is to low in part throttle regions, the result can be a bucking sensation as the engine misfires. Do you have larger then stock cams? Larger camshafts increase the natural EGR of the engine and require more spark advance to compensate for the cooler combustion temps.

utripin

Run as much timing advance as possible (up to MBT) results in higher overall engine efficiency, more torque, and crisper throttle response.

Eisen7

See attached timing map from around the area where the bucking occurs. Reckon I should bump those 19's up a little?

And yes, sorry I should have said I have HKS 272 cams.

utripin

Horrible pic, can't see the rpm, load areas. I'm on my phone.

tscompusa2

iTrader: (22)

Eisen I have no idea what you're doing but that is not the timing i had in that area on your timing map.. change the upper left to a block of the same numbers.. from 10 to whatever load you idle at and then bring it down to the rpm you idle at as well.. why is it random numbers in that area?

tscompusa2

iTrader: (22)

click on it, it makes it bigger. nm guess the phone cant do it.

Eisen7

Hehe, no this was my doing Tom I did it after reading this tip from Boosted Tuning when I was getting some stalling issues with the A/C on after we upgraded to Tephra v7 (96530706).

https://www.evolutionm.net/forums/8619162-post54.html

That tip seemed to fix the A/C stalling issues for me - that's why my map looks like that. My idle is really good - I'm just trying to sort out this stuttering at about 1900rpm and 20-30 load.

tscompusa2

iTrader: (22)

ok np.. but really low rolls? have you checked your throttle cable etc? make sure its not getting hung up anywhere.. throttle response on a maf car is very important to avoid the hesitation stuff.

i used to have hesitation, but i dont anymore.. it could also be the injectors themselves being not very good.

but i dont have any RPM drop with ac on in my car and i didnt have to touch timing like you did.. so i think you patched an existing problem.

is this occurring with ac off as well? the studder? when is the last time you cleaned your maf? possibly you should try rescaling the maf also? what is the AFR doing when this occurs?

Eisen7

I tensioned the throttle cable and adjusted the TPS within the last 6 months when we were trying to get EvoScan to log 100% TPS correctly (it used to log 99.X% at WOT). MAF is clean.

The stuttering occurrs with A/C on or off. I put it down to the 272 cams. The car has always done it since the cams went in years ago - even when I was running a PowerFC ECU.

Do you think upping the timing or fuel in the highlighted cells will help? I am sure others with bigger cams than the (mild) HKS 272's don't have these issues pottering about carparks and crawling in traffic?

I'll look at upping those 19's and see if that helps - maybe the stutter comes from the jump from 19-32 as the ECU moves between those cells?

tscompusa2

iTrader: (22)

that sounds bad.. you dont tension the throttle cable on these cars or any 4g63 to the point it puts load on the throttle plate itself.. that must always remain tight but never putting a pull/load on the cable itself to the point it moves the plate. the throttle body has a biss screw for that very reason to let air in and the iac is there to assist in throttle control so the car does not dip/stall, etc.

i told you to undo the tps and turn it ever so slightly when logging with evoscan since its a coil system.. as it turns it puts pressure on the coil and it will adjust the TPS %.

When I had HKS 272 and stock block mine jerked also, but i cant blame the cams on it.. because my setup i have now did it.. but now it no longer does it after dialing in the proper injector pulse widths etc..

no i highly doubt that area is causing it.. that is how the evos come stock.

more timing isnt the answer.. to much will make the car perform like crap. theres a fine line there.. thats why im saying what you did was a patch and not a real fix.

if you want to stop idle from dropping it is between the idle screw and the idle air controller.. those 2 parts are the only thing responsible for controlling idle as it drops down, granted the timing map isnt abnormally jacked up.

you can experiment tho and post back your findings.. your car does take a lot of timing.. 7*+ more then the average evo does, so its very well possible it may need more timing.. just experiment and report back your findings.. but if you really did fix your TPS with tensioning the throttle cable via the plate on the intake manifold that is not good.. undo that and do it with the TPS.

Eisen7

The cable isn't tight enough that it's pulling the plate or anything. I did undo the TPS and turned it so that we got 100% TPS when at WOT.

I've also run EvoScan in SAS mode and adjusted the biss screw. That part is all fine I think. The car idles really well now with A/C on or off, it's just this other issue.

I was also thinking that because my car is a freak for timing, perhaps it needs a bit more in those cells.

Anyway, will have a play around and post back.

tscompusa2

iTrader: (22)

ok you did do it right then.. the way you said it sounded weird.. but i understand now. up the timing in those load cells and let me know what happens. or email me logs and ill help u pin point it.

utripin

I thought your problem was in higher load area's.