Forgive me for what I am about to do but I find the technical part of this thread interesting and want to test my understanding of how inlet air tube diameters might effect engine performance. I do not claim that what I’m about to say is absolutely right, it is just how I understand the computer control of the engine works. And yes I know it may be more complicated than this but I’m trying to deal with just the controls that may be affected by an under or over sized CAI pipe. I’m hoping someone with real tuning experience may correct me where I’m wrong or explain it in fewer words. So here goes…….
The ECU AFR control scheme is predictive and is based primarily on the MAF and IAT sensors; the O2 and knock sensors cause the ECU to reactively ‘trim’ the AFR.
With properly calibrated and functioning MAF and IAT sensors a relatively accurate measure of the actual mass of air entering the engine is measured.
On a predictive or proactive basis, with a ‘known’ airflow entering the engine the ECU commands the fuel injectors to provide a ‘known’ mass of fuel to enter the engine to achieve a predetermined AFR.
On a predictive or proactive basis the AFR may also be ‘trimmed’ based on the input of other sensors, i.e. TPS, MAP, water temp, others?
On a reactive basis the AFR may be ‘trimmed’ based on the input of other engine sensors, i.e., O2, knock, others?
An air inlet tube diameter larger or smaller than designed and using the stock MAF will throw off the calibration of the MAF signal to the ECU.
A smaller than standard air inlet tube diameter will cause the MAF to indicate the airflow entering the engine is greater than the actual airflow.
The ECU reads, through the MAF, that the mass of air entering the cylinders is greater than it actually is.
The ECU commands a fuel mass greater than is required to achieve a targeted AFR for the mass of air it believes is entering the cylinders.
The ECU will therefore cause the AFR to become richer than calibrated.
Rich AFRs are less prone to knock, may allow timing to be advanced, or not retarded and improve the power at a given rpm and load.
The O2 sensor may read rich and attempt to trim the AFR to lean out the AFR.
If there is not enough tolerance in the trim levels and other sensor readings the ECU may not be able to achieve a targeted AFR and could throw a code.
A larger than standard air inlet tube diameter will cause the MAF to indicate the airflow entering the engine is less than the actual airflow.
The ECU reads, through the MAF, that the mass of air entering the cylinders is less than it actually is.
The ECU will therefore cause the AFR to become leaner than calibrated.
Lean AFRs are more prone to knock, may cause timing to be retarded, reducing power at a given engine rpm and load.
The O2 sensor may read lean and attempt to trim the AFR to richen the AFR.
If there is not enough tolerance in the trim levels and other sensor readings the ECU may not be able to achieve a targeted AFR and could throw a code.
Is this correct and are you trowing that code as well
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Every available Option including On*Star
2.5" Stubby Black Antenna
Lil' Chromies
Solstice License Plate Frame (not really a mod)
Norms Fenders
Holes in front bumper from plate bracket (custom)
Solo Hi Flow Cat/ 3in dual exhaust
Kappa Intake
Forgive me for what I am about to do but I find the technical part of this thread interesting and want to test my understanding of how inlet air tube diameters might effect engine performance....
You're pretty much bang on, the ecu can adjust to the miscalculated airflow readings, but until what point? Eventually you'll hit a point where the ecm cant adjust any further.
Im not gonna stop at intake and exhaust mods, an ecu tune should yield some huge gains and the last thing i want is the maf sensor reading the wrong amount of air and screwing everything up.
Quote:
Originally Posted by MTS
I'm not throwing codes, just falling into limp mode.
I have the stock air box w/ a K&N, but I cut the front of it open to allow for more air to flow in.
Isnt it that boost controller you're using causing that limp mode, or did you stop using it?
Before modifying my stock filter to get all of its air through the front cowl/grille I took off the bottom section of the airbox & taped the air filter on.I ran it like that for a week with no problems. No problems with ram air through the grille either. I'm still using a stock filter.
What you see is normal, the 85% TPS is a relative number because the TPS limits out at approximately 4.5 volts, not 5 volts. If you look at commanded TPS you will seee 100%. In other words, 83-85% is WOT.
Well this does not seem correct. Reason I say this is I have a datalog saved from IBDRINKEN's GXP from after the exhaust was put on. We were seeing 100% TPS (not commanded TPS either). Now we are not, and the car feels weak (I think my cavalier might beat it, or run with it). His car did throw a TPS code P0121, so I'm thinking he has a bad TPS. Waiting to see if the code comes back.
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John Higgins
2001 Z24 5 spd
14.8 1/4 all motor
Well this does not seem correct. Reason I say this is I have a datalog saved from IBDRINKEN's GXP from after the exhaust was put on. We were seeing 100% TPS (not commanded TPS either). Now we are not, and the car feels weak (I think my cavalier might beat it, or run with it). His car did throw a TPS code P0121, so I'm thinking he has a bad TPS. Waiting to see if the code comes back.
It cannot show 100% true TP, the GM voltage is approximately 4.2 volts at WOT. Therefore, WOT is shown at approximately 80-85%. Commanded TP will show 100%. I would assume that if you log both you will see the reason for the limp mode, commanded will be 100%, however, the actual will some number far less than 80%.
It cannot show 100% true TP, the GM voltage is approximately 4.2 volts at WOT. Therefore, WOT is shown at approximately 80-85%. Commanded TP will show 100%. I would assume that if you log both you will see the reason for the limp mode, commanded will be 100%, however, the actual will some number far less than 80%.
I'm not sure how many times I have to say this. I have, I did. I have a log showing 100% TPS. I also have logs not showing 100% TPS. It just so happens the car throws a TPS code once the car started not showing 100% TPS. hmmmm.
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John Higgins
2001 Z24 5 spd
14.8 1/4 all motor
I'm not sure how many times I have to say this. I have, I did. I have a log showing 100% TPS. I also have logs not showing 100% TPS. It just so happens the car throws a TPS code once the car started not showing 100% TPS. hmmmm.
Don't get excited, there are three different TP fields - it is impossible for the relative TP to read 100% because the max voltage never approaches 5 volts.
Brian im not saying your out to rip anyone off, you guys are just re-selling the product. My beef is with fujita. I really hope theres going to be some people from gm at the gm tuner bash this Saturday, if there will be i'll explain this to them and record it. It is a flaw and fujita should of known this. The diameter of the area where the maf sits should never be touched.
Theres a chance i might be able to Dyno the stock, fujita and dejon intake, assuming no one buys the fujita first from ebay, i'll keep it for a bit longer and then head to the dyno.
Shabby:
Did you ever get the chance to dyno the different intakes?
As for myself, I agree the Fujita may not be as good as the stock airfilter/box set up.
I have a Beltronic G meter that has the capability of measuring HP. I have tested HP with both the Fujita and the stock airfilter/box and under all test conditions the stock airfilter and box put out about 5 more HP. I have run the test several times under several different temp, humidity and altitude conditions and the average gain with the stock set up is around 5 HP. Or said another way, with the Fujita, the engine produces around 5 HP less.
When I notified Kappasphere, I got no response. Brian can produce all the charts he wants, the proof of the matter is, the Fujita on my car is producing around 5 HP less than the stock airbox and filter.
The only reason I keep the Fujita on the car is for appearance since I show the car almost every week-end during the car show season.
Frank I
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07 Black GXP
Current Mods:
Leather, Suede and Embroidered Interior by JPM
SOLO Performance Mach Exhaust
SOLO High-Flow CAT
Hahn Intercooler
Westers Tune
Fijita Intake
Dashhawk
Beltronic G-Meter
Painted Calipers
Custom Painted Engine Cover, Intercooler Pipes and Fuse Box
Future:
DEI Cry 02 System for air & fuel cooling
Slotted & Drilled Rotors
Wide Body Kit if I can ever find one that I like
I purchased the Fujita CAI when it was first available in early 2007. I do like the looks and some of the sounds, but I really do not see/feel much of a performance (maybe 5 hp?), or MPG increase ... at least not enough to pay the $300+ I paid. I am going back to stock (w/ a K&N) for a while and see if I miss the CAI. When or if I eventually get the ECN Tune, then I will most likely put the CAI back on to max the HP potential. Until then, I am going to paint the OEM box to help it look a little better. JMHO
Steve
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2007 Aggressive GXP (Manual) loaded minus On* and Smoker's Pkg (Born 11/10/2006 and picked up on 11/22/2006) SOLD 10/17/2008
JMHO