Would SLP MAF cause car to backfire.

[zstripper2k]

Recently installed SLP maf in replace if ported stock piece. Car is 2k z28. Car had backfire issues with last maf and though an slp would fix this. When driving twisties and holding in gear while decelerating will send a hugh backfire though the exhaust. Will not do it with normal driving. What is my next step. Should i go back to an unported stock piece?


Mods: LS6 intake, pacesetters with 3"ory to 3.5" dumped, msd wires with AC plugs and volant CAI.

[Cantalope Kid]

I would expect a little backfire when you let out the gas with a dumped y pipe with no cats and no exhaust. Especially after a WOT blast on decel... Junk that SLP MAF. It will give you nothing but problems. If you want to upgrade to something beyond stock get yourself an 85mm truck maf off Ebay with the 3 to 5 pigtail. Did you tune your VE table and MAF transfer fuction after adding the the headers to your car?

UPDATE: LOL I know you! You have a muffler all right... same as me.. a dynomax bullet (literally an open hole). Guessing you need some tuning work. I'll lend you all the hardware (MPVI PRO and FAST Wideband) you need and have some edumacation materials I think you'll be interested in as well.

[C5 2000]

The popping usually happens when DFCO is not coming on (unburnt fuel in the exhaust igniting).

[zstripper2k]

Ive heard of backfiring but i guess since its such a big pipe exiting b4 the rear axle it sound like a bomb when it goes off....Literally like a 150dB hit from a subwoofer!!!! You can feel it.... Also i have stock AC platinums and have been under the impression that these hold heat alot and can contribute to the backfire. Guess i need to crash course on the software. Reading is one this but actucally doing it is another.

[zstripper2k]

I would expect a little backfire when you let out the gas with a dumped y pipe with no cats and no exhaust. Especially after a WOT blast on decel... Junk that SLP MAF. It will give you nothing but problems. If you want to upgrade to something beyond stock get yourself an 85mm truck maf off Ebay with the 3 to 5 pigtail. Did you tune your VE table and MAF transfer fuction after adding the the headers to your car?

UPDATE: LOL I know you! You have a muffler all right... same as me.. a dynomax bullet (literally an open hole). Guessing you need some tuning work. I'll lend you all the hardware (MPVI PRO and FAST Wideband) you need and have some edumacation materials I think you'll be interested in as well.

Thanks Al. Ive been doing lots of reading on how to tune and different senarious and need seat time with the software. Just learned how to use the comparason function which i think might jump me into figuring out how to tune. Ive seem many people posting their tunes online and hopefully can find someone with the same mods and use their tune as a starting point. Anybody got the matrix brain load so i can skip the learning curve...

[Cantalope Kid]

Lets get together and get you a new set of NGK TR-55's put in. I'm usually free over the weekends and have plenty of tools to get the work done. About $15 total parts last time I checked. I also have an Quad tipped SLP Catback if your interested in taking that boom sound of yours out the back (I recommend leaving out the SLP LM1 muffler, raspy with headers) for $150.

[jimmyblue]

There is always a chance that the resistor broke / solder
joint was poor, which would leave you with a plain Delphi
MAF and pig rich. Soon you'd see a fuel system rich code
from that, though.

[zstripper2k]

Whats odd is my car has never thrown a code. When i did the ls6 intake, i disconnected the egr stuff. When i fired the car up never had an ses light. Same with headers but i did use o2 sims. I figured it would have definately come on with the egr connections just hanging out there. Maybe the bulb is burn out and i just can't see that its on.

Al, thanks for the voluntary assistance. What would those plugs need to be gapped at. Also aren't they under a different identifier than the TR55's. Heard that vatozone calls them something else.

The unfortunate, yet fortunate thing is my car made the same power as true duals with the custom y so plans will most likely be a panhard brace upgrade so i have enough room to take the 3.5" pipe all the way out the back and through maybe an ultraflow or borla muff and who knows, might get a cme valance with custom tip. Also a certain shop reamed me (no lube i might add) for the y-pipe so its hard to put that to pasture.

I guess that puts me in the market for a stock maf. Somebody probably has one laying around. Actually all i need is the stock ends.

Whats DFCO stand for?

[Duffster]

Josh, someone on CL today had a Spohn T/A package for a decent price here in town.

Also, if you use the F1 function on HPTuners, I think theres a definitions section in the help functions.

***EDIT*** and I've got a stock maf if you've got a case of Mt Dew. . .

[C5 2000]

DFCO (Decelaration Fuel Cutoff),When you decel make sure your Map reading is lower than the DFCO enable thresholds in the editor.

[Cantalope Kid]

Assumption here: Josh you have your own HP Tuners hardware too bud? Cool! Wish I would have known you were interested. Could have saved you alot of $'s and just loaned you mine for free. If not its available when your ready as well as the wideband. I'm always willing to help friends of the SAFBA. I admit you may not see me around much but thats to keep my arrogant intervention at a minimum. Yup thats me! Lol Anyhow...DFCO helps you save fuel. When you let out off the gas it cuts fuel to save gas...its a pain in the a$$ when trying to tune your car so its gets turned off momentarily. May not even be active on your car at all if its been previously tuned. Alot of shops leave it off on accident upon returning the car to the owner. C5_2000 has some great advice. You could always post a copy of your tune and a log with the scanner of the issue for us.

Be sure to ask that craigslist guy which part number Spohn Torque arm as they make a trans. mount and relocation bracket mount as well. There are (2) different reloaction brackets depending on the header setup you have. Don't give him more than $200 either. Though I'm german, I'm a craigslist jew. Thanks Duff!

Duff - Mt. Dew bartering...Lol

[Cantalope Kid]

DFCO from the instructions: Hp Tuners Editor > F1 key

Deceleration Fuel Cutoff (DFCO)
DFCO can be broken down into 5 main modes of operation.

Qualifications to consider fuel cutoff (Enable)
Spark threshold/ ramp down values and enable Qualification hysteresis values while getting to fuel cut point. (Entering)
Spark values while in fuel cutoff (In)
Qualifications to stay in fuel cutoff (Exit)
Spark ramp up values to exit fuel cutoff (Exiting)
On later vehicles, DFCO will progressively cut fuel to each cylinder rather than the simpler on/off used on earlier vehicles.

DFCO Qualification
DFCO must pass a series of enable tests to even be considered. If any of the tests are not passed, the DFCO process will not be started. (Fuel is still on)

Fuel Tab - DFCO Enable Normal Section:

Temp: Engine Coolant temperature must exceed this value.
Enable Speed vs. Baro: The vehicle speed must exceed this value.
RPM vs. Gear Entry: Engine RPM must exceed table value.
TPS vs. RPM: Throttle position must be below this table value.
Map vs. Baro Entry: Map must be below this table value.

Fuel Tab - DFCO Enable Clutch Transition Section: (Not used on all models)
These values over ride ANY of the DFCO Enable Normal Section qualifications (Enable, Entering, Exit) if recent clutch activity has been detected.

These values will remain active for a short time period before reverting back to the normal qualifications.

Temp: Engine Coolant temperature must exceed this value.
Speed: The vehicle speed must exceed this value.
RPM: Engine RPM must exceed table value.
TPS: Alternate VCM %Throttle position Change must be below this table value.
Map: Map must be below this table value.
TPS Hyst: Adds to Alternate VCM %Throttle position Change value.

DFCO Entry:
Enable tests passed, VCM selects spark threshold/ ramp down values and Enable Qualification hysteresis values while getting to fuel cut. (DFCO is considered active and Fuel is still on)

Spark Tab - DFCO Entry, Active, Exit Spark Section:

Entry Threshold vs. RPM: This is the degree spark advance that must be reached to turn the fuel off.
Entry Blending vs. RPM: This is the spark ramp out rate to reach the Entry Threshold vs. RPM spark value.
Spark is removed at a rate of 12.5msec at the Entry Blending multiplier value. If your current spark advance is 20 degrees @3000 rpm, your Entry threshold is 5 degrees, and your removal rate is 0.010, the VCM will remove .2 degrees (20 x 0.010) of spark every 12.5 milliseconds until the Entry Threshold of 5 degrees is reached.

Fuel Tab - DFCO Enable Normal Section:
Speed Hyst: Subtracts from Enable Speed vs. Baro table value.
RPM Hyst: Subtracts from RPM vs. Gear Entry table value.
TPS: Adds to TPS vs. RPM table value.
Map Hyst: Adds to Map vs. Baro table value.

Enable Temp: ECT must be above this to enable DFCO.
Disable Temp: If ECT drops below this while DFCO is enabled, then DFCO will disable.
Enable RPM: RPM must be above this to enable DFCO.
Disable RPM: If RPM drops below this while DFCO is enabled, then DFCO will disable.
Enable Speed: Speed must be above this to enable DFCO.
Disable Speed: If Speed drops below this while DFCO is enabled, then DFCO will disable.
Enable Cylair: Cylair must be below this to enable DFCO.
Disable Cylair: If Cylair goes above this while DFCO is enabled, then DFCO will disable.
Enable TPS: TPS must be below this to enable DFCO.
Disable TPS: If TPS goes above this while DFCO is enabled, then DFCO will disable.

In DFCO:
All of the qualifications have been met, Spark Cut Threshold has been reached and the fuel has been turned off. VCM sets the spark advance and looks for a reason to exit DFCO.

Spark Tab - DFCO Entry, Active, Exit Spark Section:

Active Advance vs. RPM A: This is the degree of spark advance while the fuel is turned off.
Min TPS for Table A: TPS must exceed this value to use table A.
Active Advance vs. RPM B: This is the degree of spark advance while the fuel is turned off.
Max TPS for Table B: TPS must be under this value to use table B.

DFCO Entry Spark: Spark will ramp down to this value before DFCO enables.

Fuel Tab - DFCO Enable Normal Section:
Enable Speed vs. Baro: The vehicle speed must exceed this value.
RPM vs. Gear Exit: Engine RPM must exceed table value.
TPS vs. RPM: Throttle position must be below this table value.
Map vs. Baro Exit: Map must be below this table value.

Exiting DFCO:
VCM has found a reason to turn the fuel back on and start the spark exiting process.

Spark Tab - DFCO Entry, Active, Exit Spark Section:

Exit Blending vs. TPS: Spark is added at a rate of 12.5msec at the Exit Blending value. If your current spark advance (Main spark table, not Active Advance vs. RPM A/B) is 20 degrees @3000 rpm, and your add rate is 0.286, the VCM will add .286 degrees of spark every 12.5 milliseconds until the main spark table value is reached.
Exit Blending CT (Clutch Transition): This value over rides the Exit Blending vs. TPS table if clutch activity has been detected.
Stall RPM: This is the lower RPM limit for DFCO fuel cut.

DFCO Exit Spark: Spark will ramp up from this value when exiting DFCO.

[zstripper2k]

Josh, someone on CL today had a Spohn T/A package for a decent price here in town.

Also, if you use the F1 function on HPTuners, I think theres a definitions section in the help functions.

***EDIT*** and I've got a stock maf if you've got a case of Mt Dew. . .

Hell yea ill take the MAF. Gimme a shout on tha telly when you get a minute. Mt. Dewd to the rescue. On another note what MAF r u running? In reguards to the T/A relocation, i already have a UMI. What i am looking for is the panhard support relocation. It gives you alot more clearance over the rear axle when running true duals out the back so i need all the space I can get trying to make a 3.5" pipe clear. Thanks for looking though

[zstripper2k]

Thanks for the info Al, C52K, Duff, jimmy blue. Im like Jonny 5, "Need More Innn-put." Im gonna Mt. Dew-fiscate the stock MAF from duff and see it that helps with the back fire. Hopefully so and when i get to tuning it will make for an easier intro into the seemingly limitless world of HP TUNERS!!!!

[Duffster]

You've got my number.

[Duffster]

Working yet?

[RWTD]

Can I ask a simple question? Did you actually dial in the MAF transfer properly after putting in the SLP? Calculated Load is WAY off by just swapping in an SLP, and it requires some heavy recalibrating on the MAF transfer to get it perfect. When I say perfect, I don't mean raping the PE values either, I mean actually dialing in the transfer so that Commanded = Actual throughout the entire curve.

And, no, I wouldn't junk the SLP MAF. Sure, I don't recommend buying it over the factory GM 85mm piece, BUT once you calibrate the SLP MAF transfer in properly, you'll be totally fine.

Also aren't they under a different identifier than the TR55's. Heard that vatozone calls them something else.

TR5 Part #: 2238
TR55 Part #: 3951