You can type here any text you want

Quick question on closed loop feature on DFI gen 6

Welcome!

By registering with us, you'll be able to discuss, share and private message with other members of our community.

SignUp Now!

Markolc

New Member
Joined
Mar 19, 2002
Messages
25
I just got my motor running, and a decent base program on it. Now I really need to go through emmissions. I have a catalytic convertor on the car now, so that's a big plus. And I'm running the Lingenfelter 219 cam in an LT1 motor, so It's not an overly huge cam. Now, when the DFI is in closed loop, is it automatically shooting for a 14.7 A/F ratio? Or is it running off my base fuel map? Because if it's constantly adjusting for 14.7 stoich, I shouldn't have too much trouble getting my best shot at passing emmissioins then right? Just wanting to confirm...thanks.
 
yes, unfortunately thats how calmap works, it will try to get to 14.7:1 at WOT ... thats way too lean IMO.

Greg
 
VTEC is right. The DFI will correct the A/F ratio to 14.7 to 1.

Remember thought that the computer will do that up to whatever setting you have on the High Closed Loop Throttle setting. You may have to set it higher just for emissions sake and passing the test. Then you can go back and set it to where you had it before.

Hope this helps.
 
OK, I went through emmissions and I passed everything with flying colors, except HC (hydrocarbons). The limit is 144, and I was at 376. What can I do to lower that for the re-test? The emmissions test is on a dyno, and they take your car to 25mph on the roller, at which point my motor is in the 1750-2250 RPM range. Should I lower timing, add ethanol, run it in open loop a little leaned out? Any advice would be appreciated. Thank you.
 
Does Closed Loop control timing other than getting information from the ignition timing maps?
 
I am not sure if the DFI will control the EGR valve.

That may be the problem.
 
I'm not running an EGR, The cam has enough overlap where I don't need the EGR.
 
That young Skywalker is you failed. LOL!!!!

Sorry I could not resist.
 
we have the same setup in MA as you do there, i would try lowering your fuel pressure VERY VERY low,just so the car will barely run, i have passed 700+ turbo\supercharged cars this way

HTH

JS
 
Are you positive that all the part throttle areas of your fuel map are close enough that the system is actually achieving a 14.7:1 a/f ratio in closed loop? The control system has a limited range that it can correct for. When they run it on the dyno do they move the throttle up/down a bit? Maybe your accel enrichment is way off, giving you big, rich HC puffs. Maybe there are some cells in your map that are way rich that the system runs through during the test. Maybe you have some stumble areas where it misfires a bit?

The EGR would help for NOx, but would probably hurt the HC, not help it. There's an inverse relationship going on where you decrease one at the expense of the other and vice versa. NOx forms at high combustion temperatures, where more HC tends to get used up. So raise the temp and you help HC but now NOx goes through the roof. Lower the temp and NOx comes down, but now HC goes up. Food for thought.

I wonder if your cat was up to temp, in good health, etc?

TurboTR
 
Depending what ALL the values were, you might try to richen it up a tad, retard the timing a tad.

If CO was very low it might have had a lean misfire causing HC, if CO was close, and HC failed, you might try lowering timing 2-3* and leaning it some.

Can you give me CO, CO2, HC, NOx and O2? Maybe I can help you here.
 
My CO was .01 (very low), my NX was around 400 out of a possible 1000, and HC was 376 out of a possible 144. Those are the only values they test for. I'm already running about 8-10 degrees retarded than I should be running. I'm running L98 Timing on and LT1. Would a whole mess of dry gas help and unplugging an injector?
 
If you can fatten it some at the test operating area you will pass. HC isnt that far off, and Co is very low. I'd shoot for ~.2% CO (NJ cutpoint is somewhere around .5% so you have room. I know you're not in NJ, but NJ is like 2nd most strict in the US) and I bet $ that HC comes down under 170ppm. If youre at 14.7, try fattening it to 14.3 or so.

If you cant do that, try running it open loop and raise the FP a few psi
 
I am interested in the outcome of this discussion. I have two vehicles with various mods that have had trouble passing emissions testing in Texas. And now they have a whole new process which I have not been through. I am told that it involves a chassis dyno!

Butch
87' WE4
94 K5 Blazer with LT1 and DFI
 
I guess that I should contribute what little knowledge that I have.

I couldn't pass emissions with a MaxEffort Thumbwheel chip. I tried all kinds of "tricks" and couldn't even get close. I put the stock chip back in and passed without a Cat. I have been told that the MaxEffort was not intended to be able to pass emissions inspection. This is not a complaint... I LOVE MY MAXEFFORT!!!!!

I haven't even tried to get my 94' Blazer (with LT1 and DFI) to pass yet. I am in Chicago right now and even though my sticker is expired I haven't had any trouble with "the law". It has long tube headers with no Cat's and the biggest FlowMasters I could buy and it's still too loud (can't hardly order at a drive-thru). It will be getting a new exhaust system including Cat's before I even try to pass Texas emmisions. I am open for suggestions on this matter! Good Cat's and Mufflers for SBC???? I want it to sound like a Corvette or Camaro, I mean, it has the same engine?

Butch
87' WE4
94' K5 Blazer w/ LT1 and DFI
 
Is it alright to try and use dry gas (Methanol)? If so, how many bottles of it is safe to run in the tank?
 
I finally passed using dry gas and richening it up a little bit. Thanks for the help guys!
 
Back
Top