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Old 05-03-2004, 07:41 PM   #1
ride5000
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Default highest MAF sensor voltage w/stock turbo/ic

... pretty much like the subject line says.

right now my max observed is 4.3v.

i wish i could read the voltage with more accuracy, but i'm taking readings with a utec and it seems to only log to the nearest tenth of a volt.

i'm curious as to how well others' engines are breathing. in fact i find the maf sensor voltage a pretty decent indicator of engine performance.

ken
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Old 05-03-2004, 08:22 PM   #2
MustGoFast
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seems pretty high for the stock turbo.. I don't recall if mine gets that high w/ the vf34 holding about 17.5 at redline.. although I know it makes a helluva lot more power than the stocker ever did.
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Old 05-03-2004, 08:46 PM   #3
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Have you ever dynoed the car? I thought high MAF voltages on lower powered cars were signs of a boost leak..
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Old 05-03-2004, 09:36 PM   #4
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That's the highest unmodded voltage I see: 4.3


I'm concerned, cuz when I throw on an 18g, it doesn't seem like I've got much headroom: .3v

Might be time for a bigMAF.
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Old 05-03-2004, 09:38 PM   #5
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I've only hit 4.1

That is without a turboback, just an uppipe and silicone hoses.

4.2 - 4.3 sounds possible, but it would pretty much be the max, I'd think.

Was this with race fuel? because on 91 octane I'm at over 95% IDC... which is really wide open... at the peak of my 4.1v area.
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Old 05-03-2004, 11:49 PM   #6
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i see an uncorrected 4.2/4.3 often with high idc's, stage2+uppipe untuned car
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Old 05-04-2004, 06:40 AM   #7
ride5000
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let me clarify... i don't see 4.3 regularly. most of the time the peak is at 4.2v. i know i do not have a boost leak, and i know that i do run very rich on the txs stage 2.5 base map from wrx hackers.

i have done some work to my throttle body (butterfly, shaft, bore) and ic elbows, i've got samcos, a velocity stack from the airbox to the fenderwell, k&n, and a fully catless tbe. boost pressure is set to about 17.5 with an mbc and it tapers itself..

my inj. DC do get up there.. def. >95% much of the time. every once in a great while i get a ---.- in the utec log, which i have understood to mean static, but it doesn't happen often. i know i am certainly on the rich side of safe. someday i'll pick up a tuna, but not yet.

i'll be watching that maf voltage as it gets hotter out.. it should go down as the air gets less dense. with an ic sprayer it should increase, as it would with a bigger/better ic. i plan to impliment water injection someday too, and that will be interesting to observe.

i am wondering if the MAF sensor voltage as picked up by the utec has already been IAT corrected?

ken
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Old 05-04-2004, 08:14 AM   #8
Zackbo
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I'm runnin' the stock turbo at 17 psi. My IDC's are in the low 50's, courtesy of the injector hack mod. I usually shift by 6200 rpm though, since the stock snail is runnin' out of breath by then. But I do see 4.3 regularly @ 6k rpm. I also have a hacked Injen CAI. It must not be leaning me out too much.
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Old 03-13-2005, 05:58 PM   #9
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I wanted to bump this and see if anybody else has stock turbo readings. I wonder if 4.4v is obtainable.

I get 4.3v on pretty much every pull, any gear except 1st.

I know my injectors are maxed , that will be taken care of when the weather warms up a little. I have a v7 sti fpr that Im hoping is one of the ones that already has its pressure bumped up. I dont want to mod my own fpr because Ill be modding my injectors and putting on my vf22 soon enough, and the modded injectors should be plenty. I usually just drive around in stock mode for now.

mods= catless tbe, gutted uppipe, headers, v7 tmic, walbro, utec/tuner
nothing ported or polished.

I just realized the title of the post is stock ic too, oh well....

Code:
5065 +12.1 4.2  85  70    00   W/B  +16.8   91.3 +21.0  -3.0 390.00 4.0  10.59
 5257 +14.3 4.2  93  70    00   W/B  +17.0   91.5 +21.0  -3.0 400.00 4.0  10.80
 5282 +14.7 4.2 101  70    00   W/B  +18.8   94.1 +21.0  -3.4 445.00 4.0  10.89
 5455 +14.7 4.2 101  70    00   W/B  +18.9   97.4 +21.0  -3.2 445.00 4.1  10.87
 5402 +14.7 4.2 101  70    00   W/B  +19.6   97.7 +21.0  -3.4 445.00 4.1  10.80
 5546 +14.9 4.2 102  80    00   W/B  +20.8   97.3 +21.0  -3.7 445.00 4.0  10.78
 5574 +14.7 4.2 101  70    00   W/B  +20.9   96.2 +21.0  -3.6 445.00 4.1  10.78
 5717 +14.5 4.3 101  70    00   W/B  +21.5   99.9 +21.0  -3.7 445.00 4.1  10.71
 5797 +13.7 4.3 101  70    00   W/B  +22.7   99.2 +21.0  -3.7 445.00 4.1  10.62
 5797 +13.5 4.3 101  70    00   W/B  +23.0   97.7 +21.2  -3.8 475.00 4.1  10.62
 5889 +14.1 4.3 101  70    00   W/B  +23.6  ---.- +22.0  -3.8 475.00 4.1  10.65
 5899 +14.3 4.2 101  80    00   W/B  +24.5   92.7 +22.0  -4.5 475.00 4.1  10.64
 6038 +14.1 4.3 101  70    00   W/B  +24.0   96.7 +22.0  -3.9 475.00 4.1  10.78
 6127 +14.1 4.2 101  70    00   W/B  +24.3   97.5 +22.0  -3.9 475.00 4.1  10.81
 6138 +13.9 4.3 101  70    00   W/B  +24.3   99.5 +22.0  -4.1 475.00 4.1  10.73
 6313 +13.5 4.3 101  70    00   W/B  +27.7   99.3 +22.0  -4.1 475.00 4.1  10.73
 6385 +13.9 4.3 101  70    00   W/B  +28.0   96.7 +22.0  -4.2 475.00 4.1  10.74
 6385 +13.9 4.3 101  70    00   W/B  +28.3   99.1 +22.0  -4.3 475.00 4.1  10.80
 6485 +13.5 4.3 101  70    00   W/B  +28.1   96.6 +22.0  -4.4 475.00 4.1  10.78
 6574 +13.9 4.3 101  70    00   W/B  +28.8   94.5 +22.2  -4.4 475.00 4.1  10.76
 6626 +13.9 4.3 101  70    00   W/B  +28.5   97.3 +22.4  -4.4 475.00 4.1  10.81
 6680 +13.9 4.3 101  70    00   W/B  +28.5  ---.- +22.5  -4.4 475.00 4.1  10.81
 6706 +13.9 4.3 101  70    00   W/B  +28.7   98.1 +22.6  -4.4 475.00 4.1  10.76
 6734 +13.7 4.3 101  70    00   W/B  +29.0   98.2 +22.7  -4.4 475.00 4.1  10.71
 6734 +13.5 4.3 101  70    00   W/B  +29.1   99.1 +22.8  -4.3 475.00 4.1  10.68

Last edited by santofontana; 03-13-2005 at 06:05 PM.
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Old 03-13-2005, 08:34 PM   #10
AZScoobie
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If any part of the intake system is changed then you guys cant compare voltage numbers. Thats the problem here... Any intake is going to cause less of a reading in my experience. Removing the black box also changes readings. So if you are going to compare list your intake mods.

Another thing to consider is the density of the air. Its very possible to read say 4.3 volts at 13 psi but then in another part of the country 4.3 takes 17 psi. Altitude really effects this so keep that in mind. Typical ranges for stock turbos are 4.1 to 4.4 volts. I have pushed them up to 4.4 to 4.5 on race fuel but thats not common. VF30 cars typicaly run 4.5 to 4.7 volts if tuned correctly.

My GT30R on the 2.0 would run 4.9 at 20 psi past 6000 rpm.

Our GT35R kit runs 5.0 volts past 5000 rpm at 17-18 psi.

Our GT35R kit with Bigmaf runs 5.0 volts from 5500 rpm up at 23 psi or higher. Which is nearly 60lbs of air.

Dave, Yes an intake leak can cause higher readings. Its typical for most BOV's to leak at least some air. If they do the compressor works harder pressurizing the system and is actualy flowing more air as you are venting that air out the leak. Its easier for the air to run out of the leak than it is to go into the engine.

We use a 3 inch pipe with a cap on it with an air hose fitting. We attach that to the intake pipe after the air box and compress the intake tract up to 15-20 psi. I was really shocked to find out how many cars have leaks. Our shop car with the t04R turbo used an HKS valve. That valve leaked badly at 5 psi. That car made well over 400whp on 91 octane at 18 psi with a valve that leaked like crazy. We went to a Tial 50mm Bov now and will retune the car this week.

P.S. Santo, That timing map needs work...

Cya

Clark
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Old 03-13-2005, 08:45 PM   #11
santofontana
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Well my intake is stock with a fram paper air filter.

addressing this;

Quote:
P.S. Santo, That timing map needs work...
Care to shed some light Im kind of a slave to shift knock. I messed with the timing today and I guess I went a little overboard on the top end. I put 20s in my 0% column too, maybe thats all I needed to do. I will try and add some timing back in on top if thats what you are referring to.
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Old 03-14-2005, 08:00 AM   #12
ride5000
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santo, i've been hitting 4.4v once in a while since it's been colder. see http://forums.nasioc.com/forums/showthread.php?t=672274 .

i really can't wait to get my exhaust manifolds off and clean them up. i wish the tgv delete was easier 'cuz that's on the list too.

ken
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Old 03-14-2005, 05:23 PM   #13
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Quote:
Originally Posted by santofontana
Well my intake is stock with a fram paper air filter.

addressing this;



Care to shed some light Im kind of a slave to shift knock. I messed with the timing today and I guess I went a little overboard on the top end. I put 20s in my 0% column too, maybe thats all I needed to do. I will try and add some timing back in on top if thats what you are referring to.

You are most likely getting rich misfire and not knock. Your timing should be in the 23-27 range up top fading back to 15-17 in the trq peak. AFR might have to be lowered a half point. In the 0 column you can probably run 25-30 degrees. The Utecs res is not fine enough so you will be forced to jump in 4-4 degree steps by the 30 column or so. This should help bottom end drasticaly.

C
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