his car has the "ED" TIP mod and therefore throws no boost codes ... whether it will recognize 18 -19 psi as too much just by the MAP sensor sensing it then we'll have to see [cleaned up a little ]
The throttle inlet pressure (TIP) sensor is used by the PCM to judge and adjust boost response via the factory boost control solenoid. If I remember correctly its solenoid also switches it to atmospheric to measure barometric pressure (sea level, high elevation, etc.). The manifold absolute pressure (MAP) sensor is what the PCM uses to calculate the amount of air going into the engine and determine when you're going into "overboost". But if you clamp or limit the output and not the TIP sensor the PCM should be seeing it as excessive pressure at the throttle and try to alter boost (if the factory boost control is still used) or take other measures to protect the engine. I mostly ran my car with Stage 2 so I never played around with tricking the PCM input from that sensor.
Hehehe..
I get to KINDA correct Blackbird...
Map/Tip sensors are not calculating the AMOUNT (volume) of air going into the engine... They are calculating the PRESSURE of air going into the engine.
Thats your two big differences between the MAP sensor and the MAF sensor (used on other cars). One measures pressure... 1psi, 2psi, 3psi etc.. The other measures flow or volume of air...
TJ
__________________
In Memory of Steven "Nightshade" Lorenz
May you rest in peace.
6/11/1987-4/4/2006
The manifold absolute pressure (MAP) sensor is what the PCM uses to calculate the amount of air going into the engine and determine when you're going into "overboost".
Hehehe..
I get to KINDA correct Blackbird...
Map/Tip sensors are not calculating the AMOUNT (volume) of air going into the engine... They are calculating the PRESSURE of air going into the engine.
Thats your two big differences between the MAP sensor and the MAF sensor (used on other cars). One measures pressure... 1psi, 2psi, 3psi etc.. The other measures flow or volume of air...
TJ
Maybe "kind-of" if you read it wrong, but not really.
Key word = calculate, not measure
But the MAP sensor is used in part to "measure" the amount of air going into the engine via the PCM. The PCM does that by measuringpressure and then calculating the mass of air from that.
I'd say it's more of a clarification for someone who has minimal knowledge of how the MAP sensor works.
And since it was brought up, the SRT-4 does use a speed-density system where it uses the manifold absolute pressure (MAP) sensor to measure pressure at the intake manifold and use that in calculations that include rpm and other sensor data like the intake air temp sensor (IAT) along with the known engine volume to determine the amount of air in the combustion chamber and therefore calculate the fueling requirements.
The mass air flow (MAF) sensor used on other engines can actually directly measure the amount of air physically entering the engine. Inside the most common MAF sensors are a sensing element comprised of a heated wire or film surface. As more air crosses the wire/surface it starts to cool them down, but due to design of the heated element the resistance of the wire/surface also decreases allowing more current to flow and keep it at the same temperature. You can then measure that amount of current being used to hold a constant temperature. I also believe some may now use a sensing circuit to directly measure the wire/surface temp and the internal controller adjusts current to keep it at a constant temperature.
In either case the control circuit in the MAF then uses that current required to keep it at the same temperature to determine airflow (since it cools down proportionate to airflow) in conjunction with an IAT that helps the PCM determine the amount of air (since the density of air changes with temperature). The MAF sensor then outputs a signal to the PCM telling it how much air is coming in. On a scan tool, with the GM's for example, you can usually watch this calculated value as grams/sec of air.
The MAF sensor can be placed anywhere with smooth airflow (not near intake pipe bends, etc) in the intake tract between the air filter and throttle body. Some turbocharged cars use them before the compressor's inlet and others use them in-between the turbo outlet and throttle body. In any case a MAF car like the WRX from the factory can't use an external BOV that vents to atmopshere because the MAF sensor would think there's more air flowing in when it vents. Also more trivia was when GM was first doing development work to add fuel injection to their 2.8L OHV V6 they used both MAP and MAF. For example the Citation/Celebrity got a MAF setup and the Fiero got a MAP system. If there were long-term emission problems with either system they could have switched to using one system exclusively.
Both sides have their advantages and disadvantages to the tuner. BTW I also own more than a few other cars that use MAF sensors so I'm a little familiar with their operation.
__________________
Eric H.
__________________ Need to contact me? I don't check PM's here so clicky.
We should retitle this thread to say "Blackbirds random but very intelligent conversation about cars and the SRT"..
We could then make it a question and answer session... Just like the insurance thread in the General Discussion section of the forums.
Hehehe.
And hey, the MAP SENSOR doesn't measure the volume of air going into the engine, the NGC calculates that based off the amount of pressure the sensor reports AND a table based off the amount of air the turbo can flow at given pressure.
Thats why ported and clipped stock turbo's are so neat... You can leave them setup on stock controlled boost lines, and the NGC has no idea you are FLOWING more air, because your pressure never increases.
And hey, the MAP SENSOR doesn't measure the volume of air going into the engine, the NGC calculates that based off the amount of pressure the sensor reports AND a table based off the amount of air the turbo can flow at given pressure.
Thats why ported and clipped stock turbo's are so neat... You can leave them setup on stock controlled boost lines, and the NGC has no idea you are FLOWING more air, because your pressure never increases.
Super close. Technically it could care less what turbo you have bolted to it. It's going to provide a certain response/output for certain inputs, and that response/output (timing and fuel) may be tailored for the stock turbo, but it doesn't directly look up somewhere in its programming a stored value of what the stock turbo flows. Instead it calculates it.
The NGC should just be using the the pressure, IAT, rpm's, and engine displacement along with factors like the pre-programmed volumetric efficiency. The intake air charge is a gas and things like density (mass/volume) are affected by pressure, volume, and temperature (since the gas itself molecularly isn't changing). So the PCM knows the temperature (IAT) and it knows pressure (MAP), so it can calculate volume. And if it knows volume and the mass of normal air (which is a constant), it can compute density. So it has ways to figure out just about anything it needs to. How it goes about this is currently unknown to the general public until it gets hacked and we can see the equations and tables it uses together. (And it shouldn't use table-only look-up and cell comparison like older cars, but some tables still should be there to use in equations and algorithms to calculate fueling and timing requirements under specific conditions.)
If you port and clip a stock turbo the compressor side isn't really changing and it's moving the same amount (mass) of air per shaft revolution. What has changed is the exhaust side. You've removed restriction which should increase volumetric efficiency. So you could think of the turbo trying to push air in but now the exhaust side is flowing better so exhaust gasses can get out to the tail pipe easier. If the exhaust gasses flow better the burned intake charge can flow out easier to take place of the exiting exhaust. Now if this slows down the turbine then the compressor would also correspondingly slow down (i.e. perceived lag/delayed boost) but also may not choke it up top and allow the compressor to pump more air though at higher rpm's
For the most part at higher boost levels on a stock turbo compared to the same boost on a bigger aftermarket turbo, the big turbo willl be more efficient at compressing the intake charge (efficient = cooler = denser = more oxygen molecules to burn) and the exhaust side will be more efficient so overall efficiency and power will increase.
There was another long thread where I was discussing this with someone else already. I'll just say that the NGC should be programmed to work with the stock turbo and work well within it's operational characteristics, but it doesn't have a "flow look-up table" and instead uses algorithms and known lookup characteristics from the other sensors to determine the amount of air (if my educated guess is correct). Also consider that if the computer sees characteristics like xx boost and yy IAT's and it may produce a output (fuel and spark) tailored to the stock turbo. So even with a big turbo at a certain boost pressure combined with other variables it may still dump a lot of fuel or do something with timing because it would be better for operation with the stock turbo.
I've got to be really careful when talking about this subject because it really should be broken down a lot further in-depth, and while trying to give a broad overview it's possible to skew the interpretation or not get a point or idea across correctly. I try though.
And hey, the MAP SENSOR doesn't measure the volume of air going into the engine, the NGC calculates that based off the amount of pressure the sensor reports AND a table based off the amount of air the turbo can flow at given pressure.
Thats why ported and clipped stock turbo's are so neat... You can leave them setup on stock controlled boost lines, and the NGC has no idea you are FLOWING more air, because your pressure never increases.
Super close. Technically it could care less what turbo you have bolted to it. It's going to provide a certain response/output for certain inputs, and that response/output (timing and fuel) may be tailored for the stock turbo, but it doesn't directly look up somewhere in its programming a stored value of what the stock turbo flows. Instead it calculates it.
The NGC should just be using the the pressure, IAT, rpm's, and engine displacement along with factors like the pre-programmed volumetric efficiency. The intake air charge is a gas and things like density (mass/volume) are affected by pressure, volume, and temperature (since the gas itself molecularly isn't changing). So the PCM knows the temperature (IAT) and it knows pressure (MAP), so it can calculate volume. And if it knows volume and the mass of normal air (which is a constant), it can compute density. So it has ways to figure out just about anything it needs to. How it goes about this is currently unknown to the general public until it gets hacked and we can see the equations and tables it uses together. (And it shouldn't use table-only look-up and cell comparison like older cars, but some tables still should be there to use in equations and algorithms to calculate fueling and timing requirements under specific conditions.)
If you port and clip a stock turbo the compressor side isn't really changing and it's moving the same amount (mass) of air per shaft revolution. What has changed is the exhaust side. You've removed restriction which should increase volumetric efficiency. So you could think of the turbo trying to push air in but now the exhaust side is flowing better so exhaust gasses can get out to the tail pipe easier. If the exhaust gasses flow better the burned intake charge can flow out easier to take place of the exiting exhaust. Now if this slows down the turbine then the compressor would also correspondingly slow down (i.e. perceived lag/delayed boost) but also may not choke it up top and allow the compressor to pump more air though at higher rpm's
For the most part at higher boost levels on a stock turbo compared to the same boost on a bigger aftermarket turbo, the big turbo willl be more efficient at compressing the intake charge (efficient = cooler = denser = more oxygen molecules to burn) and the exhaust side will be more efficient so overall efficiency and power will increase.
There was another long thread where I was discussing this with someone else already. I'll just say that the NGC should be programmed to work with the stock turbo and work well within it's operational characteristics, but it doesn't have a "flow look-up table" and instead uses algorithms and known lookup characteristics from the other sensors to determine the amount of air (if my educated guess is correct). Also consider that if the computer sees characteristics like xx boost and yy IAT's and it may produce a output (fuel and spark) tailored to the stock turbo. So even with a big turbo at a certain boost pressure combined with other variables it may still dump a lot of fuel or do something with timing because it would be better for operation with the stock turbo.
I've got to be really careful when talking about this subject because it really should be broken down a lot further in-depth, and while trying to give a broad overview it's possible to skew the interpretation or not get a point or idea across correctly. I try though.
Actually former military electronics tech that recently got out after about nine and a half years and now work doing tech/IT support. And no, I'm not going to talk about computers now too. The ones with keyboards and not the ones in cars that is.
But if you're ever on a Unix/Linux workstation remember this "helpful" command: sudo rm -rf /
A password may be required.
BTW don't do it unless you really hate your workstation and all your stuff.
Don't know if the SRT does that but the Buick Gran National does. It's called wasted spark technology (At least some of the guys in the community call it that) It helps with emissions and it's easier to trigger one side of the coil at a time.
/OT
My experience:
S3R stock exhaust AGP direct fit FMIC.
DAB 2&3 just over 20PSI on the stock guage.
I see no "knock retard" and low to mid 30's timing wise. When i hit HOM i get up to about 6 on the knock retard and HOM shuts off in the middle of third. I get about 3 in second to redline.
An interesting note. After i've fallen hout of HOM the car shows .5 or maybe it's 5 for knock retard when i'm slowly rolling into the thorttle and it stays like that all the way through any gear i'm in. It's not till i turn HOM back on and off again manually that the knock retard number goes away completly.
*EDIT*
All of that HOM stuff was done on 93 just to see how it all worked and at what point HOM would stop.
Remember that just because you're rich doesn't mean you're safe from knock. You could be 9:1 AFR and still get knock.
And the SRT-4 does use wasted spark. They can use fewer, larger coils in the same space, it works just as well, and it saves money. You can guess which one is important to auto manufacturers.
Hot air intakes, excessive boost, excessive boost utilizing the stock intercooler, high ambient temps, and excessive timing due to over aggressive clamping will all lead to knock retard (more so in the upper rpm's) which reduces your peak horsepower, but not your peak torque output. Actually if you're getting an ass load of torque and a low horsepower output you are more than likely suffering from the knock retard syndrome.
Remember that just because you're rich doesn't mean you're safe from knock. You could be 9:1 AFR and still get knock.
And the SRT-4 does use wasted spark. They can use fewer, larger coils in the same space, it works just as well, and it saves money. You can guess which one is important to auto manufacturers.
Hehehe..
And the a/f ratio vs knock retard is so true... Im running right now a 10.2 at spike, and that tapers down to a 9.7 a/f wise.. I still see 6 degrees of knock retard.
Thats on piss 91 octane gas, 22psi of boost, and the stock fmic.
Hot air intakes, excessive boost, excessive boost utilizing the stock intercooler, high ambient temps, and excessive timing due to over aggressive clamping will all lead to knock retard (more so in the upper rpm's) which reduces your peak horsepower, but not your peak torque output. Actually if you're getting an ass load of torque and a low horsepower output you are more than likely suffering from the knock retard syndrome.
Hehehe.
I should post a graph of a dyno run in which I made 305ish peak wtq, and 210 peak whp.
my map clamp was only lettin the map see 11.9psi of boost at WOT....fuel psi was at 68....boost was 21-18 (3rd gear)....a/fs were in the 11s..in 4th it would dip to the 10.9s then back to 11s....
anyways according to the Aeroforce gauge...timing read 28* held there and peeked 29.5*....knock retard was still at 5.5-6.5 ....JUST LIKE ON PUMP GAS!!!
so i dunno whats up....although car pulled like a mother!!!...
__________________
srtkid - doin 40mph rolls in 2nd gear since 6/03 Mods 2.5L SRT-4
S0 DW S2 injectors
JE Pistons 8.5:1 (.040 ob)
Eagle Rods
Race Ported/Polished Rev Valved Head
BC Stage 3 cams
Fidanza CG
Race Ported Exhaust Manifold w/external wg
FM E1 with port/polish
DCR Oil Modifier
Walbro Fuel Pump, Fuel Return Kit, map clamp
CAI, QW FMIC, 60mm TB, 3"TBE w/cutout
Alot of great info on here, blackbird you are very knowledable guy. What branch were you in? I am in the AF and am fixing to seperate here in within the next year, 9 years is enough. I was wondering what the value on the knock part of the aeroforce meant. I have a 50 trim setup with all supporting mods (80/20 meth/water, emanage/e01, 3" catless tbe, 3" cai, cca fmic, rc 650's, fuel return/lorenzo fuel rail, and more) Tuned @ 22.2#'s of boost I would spike 2 on the knock and then it would fall to 0 (that was with meth/water coming on @ 5#'s and full by 10#'s),28-29 advanced timing, afr 11.6 up to 5500rpms and then falling to 11.4 till redline, 1150 degrees on the egt gauge. I was really pleased with the setup, I spun 3rd gear with DR's on a couple of times! My wastegate spring was to small and could not handle the load so I ordered a bigger spring and am going to retune it to the highest boost possible on pump gas and no more that 2 on the knock (22-23#'s, and mid 11's afr) and then fill her up with C16 and tune it the same way. I will be attending a norcal dyno day in two weeks we will see.
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