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Discussion Starter #1
I just thought I would share some information I have been researching on my car lately. I have a wideband (from Flat4). After talking to Larry/hotrod about oakos.com website and the little vacuum test they did on a AEM intake I decided to see what my intake tract was seeing in terms of vacuum.

*Intake silencer hack with the rubber mold into the air box removed with a stock paper filter -> 77mm of mercury vacuum measured by my AVC-R pressure sensor. A/F was about 10.7:1 at redline on a 80F day. For reference the last time I measured the a/f was on ~45F night in the spring and my A/F was around 10.3-10.4:1 at redline.

NOTES: This was with the 18G wastegate line unplugged since the AVC-R won't boost anything past wastegate pressure if you hook up the pressure sensor to see vacuum I guess [heh]. So this is about 15psi at redline and 77mm of vacuum at redline.

*APS CAI put into the car -> vacuum dropped to about 69mm of mercury so a gain of about 8 mm of mercury or 1/3" of mercury vacuum. A/F dropped to about 10.6:1.

NOTES: I gained what I expected to in terms of less vacuum and the only thing I can think of in why the a/f got richer was since there was less vacuum at the turbo inlet it could flow more air = higher load to the ECU = give me more fuel for the increase in air flow. For reference as well I tested how much less vacuum was present with the stock air box and no filter and it was about 67mm at redline. So the APS CAI has almost as little restriction as no air filter in the stock box.

Next up will be the Perrin turbo inlet tube and the SAMCO S tube (replaces the accordian piece from the air box to the turbo inlet tube). I am hoping with the APS CAI and the silicon tubing to the turbo I can drop the vacuum that the turbo sees from 3" to about 2" or better.

For reference based on my calculations if I was at 6000ft asl and at redline there was 3" of vacuum being presented to the turbo to work with at the inlet the turbo would effectively be operating at an altitude of 6000ft (atmospheric pressure) + 3000 (vacuum effect) = 9000ft asl. So when I was calculating my turbo needs to get 17psi to redline with a PR of about 2.5 I think it was fairly accurate. But in reality the turbo is operating at a PR of about 2.8-2.9 to get even 15psi to redline :(.

Hope to figure it out soon and will everyone know the results.
 

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Do you already have the samco S? If not I got one that I will not be using, it is red. I asked for the turbo inlet tube and got that one, I still need to reorder my inlet tube after over 2 years.
MCL
 

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For reference as well I tested how much less vacuum was present with the stock air box and no filter...
Brave, brave soul. :) Thanks for the info, Dave. I'm interested to hear how the 'S' tube & inlet mods work out.

-p
 

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Discussion Starter #5
Dizzy said:
Brave, brave soul. :) Thanks for the info, Dave. I'm interested to hear how the 'S' tube & inlet mods work out.

-p
Well it was just for like one 3rd gear pull ;). THen I pulled over and put the air filter back in [heh].

UPDATE: It seems that the APS "65mm" CAI doesn't agree with my ECU. I have a few therioes about what might be wrong but I am getting P0171 (bank 1 lean). Now this is just the ECU being upset becuase I have put on the wideband I know exactly what the a/f is and it is not lean still very rich under WOT (10.5ish:1). But this is a CEL that comes on at hwy light cruise conditions.

My main theory is that I also have a resisitor/CEL fix for having not cats and I think this is at the edge of making the ECU that the car is running lean and the CAI might just be pushing it over its limit but I will have to try a couple of things to test that theory. I would MUCH rather live with the good old P0420 code than a system to lean though...

More to come...

WickedRydaX - Thanks for the offer but I really want to keep things as black and low key as possible though.
 

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I would bet that the ECU is confused by the voltage it is seeing from the MAF. It is trying to meter according to the airflow it "thinks" it sees. It is actually getting more air than it beleives it is due to the offset in voltage the CAI causes. Here is a good link to a good explanation of what I am trying to "think"... http://www.ecutek.com/tuning/induction/

My VF22 only holds about 12 psi to redline. Sometimes more on chilly nights. But it starts dying off at around 5800 rpms. I don't mind for now, but I think that we all may be needing to look for a larger alternative in the future.

The later the boost (torque) with equal pressure (all things being equal) means higher HP. STi heads or not. We are all seeing HP drop as redline approaches. The cool part is that the torque can remain the same in this equation, saving drivelines.
 

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Discussion Starter #7
WRX Harvey said:
I would bet that the ECU is confused by the voltage it is seeing from the MAF. It is trying to meter according to the airflow it "thinks" it sees. It is actually getting more air than it beleives it is due to the offset in voltage the CAI causes. Here is a good link to a good explanation of what I am trying to "think"... http://www.ecutek.com/tuning/induction/
That could very well be. The ironic thing is I ggot the 65mm CAI which is the same diameter around the MAF sensor as stock. I remember when I put on the AEM CAI on my 02 WRX I never had any issues and I know that it was a larger diameter than 65mm around the MAF section.

I checked the MAF sensor last night and there was some residue on the temparutre diode and one of the hotwires so I sprayed/misted some 91% rubbing alchahol on it and see how that works.
 
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