jeff spahn

I have a fine tuning question to throw out there and leave for posterity if there is an answer.

I have recently put in a VCB Engineering Supercharger kit.

The install requires 36# injectors for the stage one kit.

After using the Sharktuner and Sharkplotter software I have my AFR pretty nice and close to 14.7 all the time at idle and appropriately enriching as you put the coals to it.

What I do have is a "surge" at steady state throttle driving. It's like hitting a rev limiter very, very softly as you are driving around and not changing the throttle position.

Are there specific modifications I can make say to the injectors, timing, pulse width, etc to eliminate this surge. It wasn't there with the stock injectors and as we move up the injector sizing on the Sharktuner from 19# to 36#, it worsens each step of the way. 19# setting on the Sharktuner can't be used with the 36# injectors because the system won't provide enough fuel to properly enrich the mixture at high RPM/load situations.

Victor is coming down in two weeks when Sean is here to see what he can see but I'd like to get ideas to use and then we can post them here and save it for posterity.

I do have to say the fun factor on my car has really increased with the extra power. I am not flooring it all the time by any means but just to have a little extra "go" sure is nice!https://rennlist.com/forums/graemlins/burnout.gif

killav

Hey Jeff, one of the things that helped mine run smoother at cruise was manually averaging the four cells or five cells around where the surge was happening, then re-shark plotting.

So if you have say:

27 87
66 33

I would manually go into those cells and change them to:

57 57
50 50

It really helps to have somebody next to you so they can put their finger right where the cursor is, highlight those cells, then manually enter what you figure out as the average....good luck!

John Speake

Under steady state conditions, smallish throttle openings (low loads) you should be running closed loop.

So something is definitely off tune..... suggest you use the data looging to find out what is going on under the fault condition. Log A/F, rpm, load and O2 adjust.

Have you tuned with the Sharkplotter in forced open loop ?

jeff spahn

John. I can't speak for certain about that. I will this weekend just to be sure.

Lizard928

Jeff,
Post a screenshot of your fuel map, and ignition maps being used.

victor25

Jeff
I attached your last map as I last knew it. If you haven't changed anything, it looks pretty good. Send me a couple data logs and I will plot them to see if anything shows up.
I did notice that you have no negative numbers at all, usually I see some in there along the top

victor25

Jeff when you drive home tonight, see if the it falls off at like 2600rpm, then surges back on at 2800rpms. Watch the tack a little and see if you feel the surge at a particular rpm.

jeff spahn

I'll record maps on the way to the office tomorrow. Log the data and then post the pics. I am a total Sharktuner Newbie and Jim Coremann has really helped me along with Victor. I just want to get this perfect. It is very close right now.

Lizard928

Victor,
That image you have posted is a very very poor tune, I would even say, dangerous.

jcorenman

Fixing this will require finding the cause...

What means "surge", exactly? That implies an acceleration, versus a "stumble" which would be a brief cut-out or deceleration. Is it a repeated acceleration/deceleration, like what happens sometimes at very low RPM's? Or a stumble, like a quick deceleration and then a recovery? That would be more like a rev-limiter.

It is certainly possible to have inappropriate values in either fuel or ignition maps, that will cause a stumble (or possibly a surge) as changing RPM or load passes through those cells. This can set up a repeated surging with constant throttle... If RPM's drop into the next cell with perhaps more advance, then RPM's will increase into a cell with less advance, which drops RPM's again, etc. And similarly with fuel, if particular cells are very rich or very lean. You see this with big cell-to-cell changes.

A video screen-capture of Sharktuner's fuel-monitor page, when it is doing this, would be very helpful. "Snagit" ver 11 can do this and a free trial is available (no affiliation, just a happy user). Alternately log some data with Sharktuner (include EZK also) and post it up.

Something is changing when it is doing this, without knowing what then it is just guessing game.

SeanR

I saw that and thought "Whoachit".

Rob Edwards

Yeah, that map is fine as long as you never exceed 3300 rpm and partial throttle.....

+1 on Jim's recommendation on using Snagit to record some datalogging sessions, then post them to Youtube and link them here. I have done a bunch of this in the past when Jim was helping with my Alpha N installation in the GTS.

Snagit: Free 30 day trial, I actually ponied up for it since it's incredibly useful. Found a 50% off coupon somewhere online.

http://discover.techsmith.com/snagit...FeU5Qgod9W4ADw


Here's an example:

GregBBRD

Victor:

Does this have a SuperMaf installed, so that the correction numbers don't get into the lower portion of the map....or is this map only a cruise map, without any full throttle?

While I don't understand how Colin can say this map is dangerous, without knowing injector sizes, fuel pressures, boost, throttle position, etc....it is interesting that none of the lower cells, that I normally see "filled" with my naturally aspirated engines, are "changed". It also appears that the higher rpm fuel correction numbers are all the same....like they were manually altered.

victor25

Don't be fooled by the zeros... he is running a good fuel ratio at WOT. Around 12.0 in the 324 to 516 maf numbers without adding or removing fuel. So I would say that is pretty good. And the other areas of low maf and high rpm he has never driven in so those are base number at the moment

GregBBRD

After Sharktuning, did you remember to turn the O2 sensor back on? Obviously, when tuning, you want the O2 sensor "off", but it is common for people to forget to turn it back on. The result is that the vehicle will still be running in open loop, without any correction from the O2 sensor.