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Old 11-26-2001, 04:26 PM   #1
jeffsnyder
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Question intake problems with WOT from a stop

i just installed my ralli-spec intake and modified it to work on a my98 2.5rs and it work fine i can feel a lot more pull it seems.

but i have one problem... when i go from a stop and floor it the car wants to stall out and just sits there heisitating,

and ideas whats causing this maybe i need a S-AFC or maybe the touqe chip will help. i was also thinking maybe because i still have stock exhasut on that its to much back pressure maybe. (waiting for cat-back and header)

any body with ideas or whats happing please help me

~JEff

PS its also an automatic
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Old 11-26-2001, 04:30 PM   #2
bouse1
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Did you reset the ECU after you installed the intake? You should try that. I don't think your exhaust is the problem. If you did reset it, then maybe there's a problem with your MAF. Good luck.
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Old 11-26-2001, 04:43 PM   #3
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I agree, sounds like an ECU thing. I use the ganzflow w/stock exhaust (cheapest mod to start) and have no problems.

good luck
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Old 11-26-2001, 04:55 PM   #4
jeffsnyder
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ohh sorry forgot to add that i did it twice this weekend....

when i installed to intake the first thing that i did for that i woundn't forget is that i disconnected the battery for the reset

and i also did it again because i had to disconnect my battery to put my headlights in also

~JEff
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Old 11-27-2001, 02:33 AM   #5
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Make sure all your clamps are tight.

jeremy
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Old 11-27-2001, 07:35 AM   #6
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i check over everything and its still the same

i was talking to my buddy about it and he said that it sounds like its getting too much air at one time and can't compansate for it. and whats its doing is the nock sensor is retarding the timming to compansate for the lack of fuel and its just too much for it.

he said that i should get a s-afc to control the mixture

what do u guys think

~JEff
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Old 11-27-2001, 08:44 AM   #7
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Need more data.
Get an A/F meter and tie it in there. That will give you an idea of what is happening and if you decide to tune it later will help out a lot.

Until then, keep using part-throttle so the ECU uses the O2 sensors to compensate as the WOT maps are not very good.
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Old 11-27-2001, 10:35 AM   #8
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Does that intake use the stock airbox? if not, you might be dealing with a moment of very low pressure when you first go WOT. This is an issue with some aftermarket intakes. Ganz and the such don't feel it, but most that require you to remove the stock airbox do. Cobb is just magic, so this doesn't happen with it. I rode in an RS with a Cobb intake and it was amazing.

But yeah... lack of airbox might be your issue. If rallispec does use the stock airbox, its probably an ECU or MAF issue.

-IggDawg
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Old 11-27-2001, 12:13 PM   #9
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any under hood j-tube style intake causes a split second of throttle lag when you stomp the gas...'tis the nature of the beast.
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Old 11-28-2001, 09:11 AM   #10
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I had a huge problem with my MY01 RS stumbling all over the place, unless I was under full throttle. It turned out to be the front O2 sensor. Since the ECU uses the O2 sensor for partial throttle, but goes to maps inside the ECU under full throttle, the O2 sensor malfunctioning throws the ECU off when the pedal isnt to the floor. If your car works well under Wide Open Throttle, but stumbles under partial throttle, that would be my guess.

Josh:monkey:
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Old 11-28-2001, 05:48 PM   #11
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I have a '99 RS Auto with Stromung Cat-back. At one time I had the J-Tube type intake but had a big loss of low end. Punch it and it would stumble then start to pick up. The top end was pretty good. Sure it was great once it got going but that little stumble was good for 1 - 2 seconds added to my 0-60. If I had a 5spd I probably would have kept it. And I don't brake torque at every stop light so I took it off and put the stock intake back on. No more stumble but a lot less top end.

Waiting for Compass Motorsports intake now.
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Old 11-28-2001, 06:02 PM   #12
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well i think the problem is what Racecarriot brough up... it just nature of the beast.

as for slowing down my 0-60 times i'll find this out on firday night at ATCO raceway.

so i guess i wait a few more day to find out what it did.

~JEff
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Old 11-29-2001, 10:07 AM   #13
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im noticing the same thing. i have a j-tube intake on my 95 2.2L right now and before it was on my mom's Legacy 2.5GT. on both cars its done it and i recall being told that when you remove the box before the manifold you are removing the small reserve that the engine needs for the brief second it takes to get enough air moving again when you stomp it like that. I noticed a loss of low end but the sound the intake makes under hard acceleration makes it worth it IMO.

Jim
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Old 11-29-2001, 12:11 PM   #14
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i'm gonna say it once again...

if you don't want to lose low end, DON'T REMOVE THE AIRBOX!

put the stock system back on, take out the silencer, and put in a K&N or amsoil flat panel...sure you only gain maybe 1/2 the top end hp you would from a real intake, but you retain your low speed torque, and still get that nice roar at WOT.

i'm guessing you could get a section of tubing with fewer bends in it to run from the airbox to the throttle body instead of the stock black plastic one, and that may free up an extra hp or two.

plus, all it's going to cost you is the price of a new filter, and maybe 2 hours of your time.

-adam-
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Old 11-30-2001, 12:11 AM   #15
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Actually, if you tune it right, the only low end you will lose will be stuff under 1500 rpm. Think of it as a mild for of "turbo lag" without the turbo.
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Old 11-30-2001, 12:45 AM   #16
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Dude! I have the EXACT same problem, and guess what, it's my MAF Sensor!

I'm getting i new one... and not under warranty anymore either

I failed to note if you had a 99 and older (MAF) or a 00 and newer (MAP) cause then it's something else... but if got a MAF, look into that Sensor!

man, stupid fragile sensors on the 99!

-Gagan
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Old 11-30-2001, 07:50 AM   #17
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nahh i don't think its the sensor because when i put the stock air box back on it didn't do it....

and i have a 98

~JEff
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Old 11-30-2001, 05:06 PM   #18
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A couple of guys hit the nail on the head. The loss of power is dude to the lack of a reservoir of high pressure air to fill the intake manifold. Picture it. You are an engine sitting comfortably at idle. Then the butterfly on the Throttle body swings open creating a large change in pressure. On the engine side of the TB you have a vacuum trying to pull every last bit of air to fill its intake runners up in order to fill those cylinders. Now on the intake side of the TB you have this smooth pipe leading to the fender. It stands to reason that the slower a fluid moves the higher the pressure. Take for instance a water hose with a nozzle on the end. Stand on the hose and squeeze the nozzle, your feet will compress the hose a little. Close the nozzle and presto the water picks you up. Why should you care about this? Because the faster moving air through an intake tube us at a much lower pressure than the stagnant air in the stock air box. This means that the increased pressure the air box provides can respond quicker to rapid TB changes to provide the intake with the air it needs, where the smooth intake tube will take some time to "catch up" when the first initial TB input is processed and the tubes limited reserve is use up.

My advice is put the stock air box back on and use a smoother tube to replace the black plastic plumbing to the stock air box. In other words, get a Ganz type intake. You cant make one better for less than Larry does. Its one of the best engineered intakes out there. Its probably THE best intake for street use as a daily driver because it uses sound engineering principals that build upon the correct design already installed by Subaru from the factory. Any loss of low end is unacceptable in a street driven car. A Ganz will not cause you to loose any low end at all, while giving you a nice pull on the top end. The peak HP will not be as much as say a COBB or a Rallispec, but the 2-3 HP you may get for a few hundred RPM you will get them, is insignificant. Drivability is what is important.

Hope this helps.

SCRAPPYDO
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Old 11-30-2001, 06:54 PM   #19
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Hey Stephen - what could you possibly know about this, you're just an engineer after all

Oh...hope you can make it to the pub tonite with us.
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Old 12-02-2001, 03:00 AM   #20
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Thanks guys, I do sell two levels of GanzFlow intakes for a 1997-1998 that retain the air plenum, as well as for the 1999.

1) Just a cone filter with MAF adapter and bracket which retains the stock air plenum and the stock intake tubing, with only one version needed for 1997-1999, seen at www.ImprezaRS.com/product2.htm#filtermaf

2) An upgraded version that replaces the stock tubing between the MAf and plenum with a straight piece, including a vacuum nipple for the idle control line on phase I motors and another vesion for phase II motors, seen at www.ImprezaRS.com/shoppingcart.htm .

Both work well, the second one more so than the first. Someday I'll find the $175-$250 to dyno a stock and modified car, but for now it seems to do very well butt dyno wise.

Larry
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Old 12-02-2001, 08:06 AM   #21
SuBart
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It's normal (i think), same thing happens to me. I suppose it's just to much air for the engine at low rpm's
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Old 12-03-2001, 04:18 PM   #22
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SUBART,

Its the exact opposite. Its not enough air at low RPM. The small intake pipe does not have the reservoir needed to feed large changes in low rpm adequately.

SCRAPPYDO
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