1dirtyZ

iTrader: (1)

ok , so i relocate my maf to before the blower and WOW! it drives great , no hesetation at throttle tip in and now ltrims are predictable.

my problem now is the car stalls every now and then , just like it stumbles all the way down to 300 rpm and picks up ( sometimes it just dies).
it also always shuts off after WOT ( just like you turned the ign. off) unless you blip the gas.

what could be causing this? it never did this with the maf after the blower. do i need a bigger t-body hole?? the idle is set at 725 right now, should i raise it? the car is an m-6 by the way.

Black LS1 T/A

I see a trend here.

For example, if I trounce it, run it up to the top of first, then let all the way off, as it comes back to idle, it either stumbles or may even cut off, if I never give it gas.

Is the purge valve now confused?

I don't know what's going on.

Maybe JAS can shed some light on this issue for us.

LS1Bird

My car does that exact thing! It idles great when I start it, but has to catch itself from stalling after I've been in the throttle. It will usually dip to 400 rpms or so and then right itself. But sometimes it just dies...

Edit - my MAF is in the ATI suggested place, right between the plenum and the TB...

Mike M

<small>[ December 25, 2002, 09:05 AM: Message edited by: LS1Bird ]</small>

02BlackWS6

Is this only a problem with the ATI kits? I'm looking real hard at ATI's 7# kit. But I don't want to deal with headaches with surging and stalling. That's why I stepped down to a smaller cam.

JAS

725 in an M6 car? Isn't it 800rpm idle stock?

Raise it to 850rpm and see what happens.

Who tuned your car for the original ATI install that you are running?

cdk4219

Isnt the purge valve releasing air that already has been read fram the MAF? If so the MAf is telling the ECM that there is quite a bit of air flow, hence the stalling.Why are you getting hesitation problems with the blow through set up?I am not familiar with ATI's purge valva, but if it is similiar to an HKS or other aftermarket BOV's then ytou might be sucking air through it at idle causing your erratic running conditions.

<small>[ December 25, 2002, 03:05 PM: Message edited by: cdk4219 ]</small>

1dirtyZ

iTrader: (1)

well itried raising the idle to 800 rpms, it was slightly better , but it still died after a wot run.

cdk 4219 i was thinking the same thing, but it seems to work soo well.

right now i'm thinking of rescaling the maf table at idle , making it read more air just at idle , or if that doesn't work, less air at idle. i'll see how that goes.

1dirtyZ

iTrader: (1)

well i just came back from my latest theory test, i tried to scale the maf 15% either way at idle alone. result : still dies.

this leades me to my next theory!
relocate the maf farther away from the filter. right now the filter is sitting right on the maf.
i'm going to try to put the maf halfway between the blower inlet hat and the cone filter.

no just out of curiosity, could every one reading this thread and has the maf relocated to pre-blower state where exactly is their maf and if they are stalling / surging?

thanks

02BlackWS6

Mike,
If i put the screen back in my MAF should i install it before the TB or before the blower? Nah, my cam isn't big. Only a 216/220 cam. I think at this point i'll only run 5#'s cause i wont have the money to beef up the trans, so i'll run the lower boost. Do you think i'll have any trouble with the belt slipping at 5#'s? I wouldn't mind upgrading to GWP's 8-rib setup just to be sure. Thanks for your help Mike.

1dirtyZ

iTrader: (1)

yeah i know it's kinda low, i'm just in love with the lope!! ( i seems my car is talking to me!! <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> )

i'll raise the idle to 800 and see what happenes.
as for the tunning , it's done by yours truely! and a wideband dyno offcourse. ( seems to be getting decent numbers, right mike <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> )

<small>[ December 25, 2002, 12:01 PM: Message edited by: 1dirtyZ ]</small>

Got_UR_#

might be because you relocated the maf.

Black LS1 T/A

I don't like a high idle, either. Switching the MAF actually makes it where it can idle lower without stalling out. But, I will raise it if I have to. I dropped it back to 750 when warm. I had it at 800.

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 02BlackWS6:
<strong>Is this only a problem with the ATI kits? I'm looking real hard at ATI's 7# kit. But I don't want to deal with headaches with surging and stalling. That's why I stepped down to a smaller cam.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Don't worry about it.

We are experimenting with a non-ATI-normal setup.
As long as you ahve the stock, screened MAF in there, you should not get a surge, unless your cam is big.

My cam is VERY high lift and duration. I think, so is 1DirtyZ's.

JAS

You guys kill me. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

You put in HUGE cams and you drop the idle BELOW stock. Most NA huge cam guys are idling at 1000RPM+ and you are trying to idle at 725rpm when a stock cam needs 800rpm. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />

Try locating the MAF as FAR away from the surge valve inlet into the blower hat as possible.

1dirtyz - If you are messing with the MAF tables, you are way on your own buddy.

GOT_UR_# - Vortechs run a pull through setup direct from Vortech.

Got_UR_#

oh

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 02BlackWS6:
<strong>Mike,
If i put the screen back in my MAF should i install it before the TB or before the blower? Nah, my cam isn't big. Only a 216/220 cam. I think at this point i'll only run 5#'s cause i wont have the money to beef up the trans, so i'll run the lower boost. Do you think i'll have any trouble with the belt slipping at 5#'s? I wouldn't mind upgrading to GWP's 8-rib setup just to be sure. Thanks for your help Mike.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">My 2cents about a screened/descreened MAF plus a bonus on the GMAF:

I have in my possession three MAF's:

1. Stock with screen
2. Stock without screen and (basically) ported
3. Granetelli MAF

I've tried the Granetelli MAF and the Stock De-screened MAF AND the GMAF Ends with the stock MAF sensor. Conclusion:

The screen in the MAF levels out the velocity of the air flowing thru the MAF at idle, thereby smoothing the surging at idle. It's probably not an issue with an N/A car, but the blower is pushing quite a stiff flow of air thru the MAF and throttle-body at idle. Everytime there was a slight surge (I guess from the load of the compressor), the surge was excacerbated by a pendulum-like effect of the MAF trying to chase the fluctuating air velocity at idle.

With the GMAF or stock de-screened MAF at idle, it would actually cut off at some dips in idle. The problem was barely noticeable with the screened MAF.

The GMAF is an added, unnecessary inconvenience with the FI, unless you get it recalibrated for FI, if that is possible.

In the quarter, for three out of three runs, the GMAF consistently netted me SLOWER E/T (1 to 2 tenths) than the stock, screened MAF.

The GMAF gave me about 1 to 2 tenths in the 8th mile (before the Supercharger), so it is a good unit...

Draw-thru or Blow-thru?

I am assuming I can run my descreened MAF with it before the SC, since the before/pull-thru position makes it idle smoother.

Belt Slippage

I don't think you will have much problem with the 4.10" pulley slipping. I didn't. But I've hears some suspect they still have some slippage. I would not spend the extra money in an 8-rib when I only plan on 5 PSI, unless for some reason I were only getting, say, 3 PSI... and felt belt slippage was the problem.

BTW... I think GWP sees some merit with Mike Morgan's larger 6-rib crank pulley and may be testing it out soon.

On the face of it, if it truly has no discernible slip, it would be, by far, the cheapest and simplest route to go.

Hope all that verbage helps. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JAS:
<strong>You guys kill me. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

You put in HUGE cams and you drop the idle BELOW stock. Most NA huge cam guys are idling at 1000RPM+ and you are trying to idle at 725rpm when a stock cam needs 800rpm. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">JAS, the 422 is a bit different than such a huge cam in a stock motor.

That being said, I was idling at 800 before, with no stumble. The only change I made was the MAF position swap, and I get the stumble... actually it cut off.

I lowered the RPMs to 750 when I saw it definitely idle more smoothly, and it was rock solid. STILL, coming off WOT, it stumbled though it didn't cut off). It's not that the idle is too low.. if so, it would cut off going into gear or stopping at lights and such.

Something is going on that when you get off WOT, it wants to shut down. Remember that box we talked about? <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> Just consider SOMETHING else could be going on. The idle speed is too easy an explanation, or may just cover up something else that is going on. Could that at least be considered before chalking it up to idle speed?

Thanks for your input, man.

Black LS1 T/A

Here is an old post I dug up by Jason@GWP.

I hope my old buddy doesn't mind me diggin up some of his comments on the board:
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
Having a different MAF (bigger) doesn't really have much to do with the calculation for efficiency of the blower. For the majority of these systems the maf is on the outlet of the blower and more importantly on the outlet of the intercooler.

And here is my point, for an intercooler to function proparly you need to have a psi drop to get heat transfer. This is what effects eff. of the blower. Too small intercooler leads to a high psi build up before the I/C, and as you make psi you make extreme heat, the more heat at a given psi the less efficient your blower is.

Now to see how little your MAF has to do with the system, take a psi reading before and after the meter, I can assure you you will not see a difference.

It's a whole different story though for those of you trying to relocate the meter to the front of the blower. That will have an effect on the blower because your bottle-necking the inlet, big to small to big, you lose inlet psi which has a multipule effect on the outlet psi.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I separated Jason's post into paragraphs, so I could follow his points.

So, with that in the mix, and trying to understand all his logic, without benefit of his feedback (are you still out there, Jason?) what does this info add to the equation?

02BlackWS6

Mike,
I could be wrong but, it sounds like he's saying that our small stock MAF's is a restriction when we install it before the blower. Then that drop of volume is multiplied out the other end of the blower resulting in less psi(boost). So maybe going to a calibrated 85mm MAF before the blower will solve that issue. It could be why LS1 Motorsports uses a 85mm MAF and installs it before the turbo. If or when i get my kit i'll try the stock MAF with the screen in the stock location and see what happens. Thanks Mike.

Den

<small>[ December 26, 2002, 09:28 AM: Message edited by: 02BlackWS6 ]</small>

1dirtyZ

iTrader: (1)

02blackws6, just like Black LS1 T/A said i don't think you'll have belt slippage problems, but make sure to use alot of belt dressing.

jas, i am a man of many needs, and one of them is a low lopey idle <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> . j/k. i had the car idle that low with the maf in the stock location with now surging or dying problems.

the maf is located as far away from the surge valve as possible, it's on the end of the accordion tube and has the filter sitting right on it.

right now i want to test the theory that goes " the maf is too close to the filter which is causing turblence, thus it must be located farther away from the filter" , so i'll try to relocate my maf a bit farther than the filter.

Black LS1 T/A, i'm thinking the same thing 02BlackWS6 was about the bigger maf. but if i do go with that route i'll have to retune the car for the bigger maf .

i think i'll post a new thread or poll to see who has this problem and where are their mafs located.

editing maf tables at idle : boldly going where no F/I'er has boldly gone before! ( that lasted a good 15 min! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> )