|07-26-2004 06:01 AM|
Nick T had no trouble. Some people have had trouble though, but there is no proof either way yet.
Your engine will do everything possible to protect itself, so it should be "safe" either way.
Also, the biggest risk is running lean at high RPM, and the stock T7 system runs very rich, so there is plenty of room for error.
|07-25-2004 03:19 PM|
so basically on my t7 car if i were to get a downpipe to compliment my sport exhaust and intake. i may not have any trouble?
or another question is whether or not i can use a stage 1 ecu with al these mods?
|07-25-2004 01:08 PM|
Very interesting. Saab patented the concept of Direct Ignition and Ion Sensing using the spark plugs in cooperation with Mecel AB back in 1985. Great stuff.
Linkoping University in Sweden is doing a lot of the current reasearch. In fact I have a dissertation which contains formulas and techniques for extrapolating the MBT.
Also the last part of the trace and the tace peak level contain simple information about combustion peak rate, and EGT. It's very good stuff!
|07-25-2004 01:06 PM|
Here is another good write up explaining many of the principles we are discussing...for whoever is interested
|07-25-2004 12:51 PM|
found this online...pretty interesting stuff
|07-25-2004 12:03 PM|
Generally a higher FPR is a "bandaid fix" as it really doesn't flow much more fuel, and it can sometimes put too much strain on the injectors. But it's better than accidentally running lean.
And yes you would NOT want to force the MAF sensor to give just one reading. I've always been an advocate of adding more sensors. Disabling one of them means there is that much less the ECU has control over. Granted there are occasions where you cannot control the ECU, so you bypass it out of desperation. But idealy you just want to gain control over the ECU, and then give the ECU as many sensors as it can handle (within reason) so that it is that much better informed of the conditions in the engine.
Interestingly, Nick Taliafferro has the following mods and does not have any serious issues whether using stock or modified software:
Upgrade Turbo > 18t compressor + clipped turbine + larger exh house
Intercooler > Race aluminum
3" Complee exhaust one muffler race cat
Open air intake feeding Large bore turbo intake pipe.
So the exact cause of the downward adaptation must not be a consistant trigger. Sometimes it happens sometimes not. Still looking into things further.
As for T7 though. As much as T5 fans tend to diss it, it's a very adaptive engine management system, and in the right hands can be very powerful. The fact that it uses both MAF and MAP gives it a huge advantage over T5 when programmed properly.
Being able to measure a putative value for intake air gives it the ability to "learn" modifications, even if the factory software doesn't always take advatage of that ability.
It also has the processing speed and capacity to be programmed to do neat things with Ionization traces. It could theoretically be programmed to measure EGT, Rapid Burn Angle, and a number of other things using the Ionization Gap Sensor. Of course that's all in theory, but the point is that it has the processing power to be able to do it if someone could work out the programming.
Very good stuff.
|07-25-2004 11:01 AM|
I don't believe there are any changes in the injectors (at least none are listed) unless you start getting up into serious power levels. I would think the stock FPR simply doesnt provide enough pressure to supply the amount of fuel needed to make a stoich mixture if the boost is upped a large amount.
|07-25-2004 10:25 AM|
this is an excellent thread, i am learning quite a bit from here.
if an exhaust would make the car run leaner, how would bsr stage 1/2 software compensate there... Stage 1 is just a filter where stage 2 is filter/ exhaust. Now if Nordic and Hirsch are adding FPR then r they changing the injectors or keeping the stock ones on?
In the turbo cars i have modded in the past with maf sensors, there has always been a way to lock the voltage on the maf so it can only make one reading. The problem on T7 cars comes with the Map sensor... now we would have to lock that as well but to what values.?
|07-25-2004 09:40 AM|
I might be straying off topic here, but how does a performance ECU compensate fuel supply for the changes in timing and boost? Does it simply know more fuel needs to be added due to the increase in flow over the MAF? Does the MAP come into play the same way as with stock programming where it is used during rapid load changes or when discrepencies exist? Are new MAP values introduced with the software so there are no longer discrepencies between the two values when the stage's designated hardware is in place? If the program is a stage 1/2 program which is the same software (at least in BSR's case...not sure about the other tuners) designed to operate with or without an exhaust, it would seem there would have to be discrepencies with one of the two applications as there can only be one VE expected by the ECU yet there are 2 different VE values with or without an exhaust. I also find it interesting that Nordic and Maptun use uprated FPRs in B235R applications over 280hp while BSR, SQR and Hirsch do not. Hirsch uses a larger intercooler and turbo inlet pipe (but oddly the stock exhaust) perhaps using cooler intake temps, better VE and less aggressive tuning to control knock while creating more power. BSR and SQR do not make any intake changes or any changes to the FPR. Perhaps because of this the BSR or SQR software are more likely to create knock due to high intake temps and a lack of adequate fuel supply. Boll did say Nordic was regarded as the most reliable tuner in Sweden and we know Hirsh has a proven reputation. ERP also stated when he had his ECU custom tuned by SQR, the boost was brought down to make a smoother power band while still keeping the target power levels intact. I am guessing this was done because VE improving mods were already in place and the higher boost levels were not necessary to reach the target power levels.
Thanks again for the discussion...hopefully it is not growing tiresome to you. If it is just let me know...it's all good. I have a lot more to learn than you so I am very eager to try and figure as much of this out as possible. I don't want to be that guy that says "ohhhh this stuff will give me lots of power" but not have a true understanding of how or why.
|07-25-2004 12:33 AM|
Still not exactly sure on what's going on with it, but I think it may run lean enough during spool up to cause knock, which will cause the timing to be pulled back, and fuel to be richened up.
If knock occurs during spool up due to an unusually lean mixture the ECU will think it cannot run as much boost pressure as it realy can. So the knock system will limit the boost more than it would normally need to.
Only a possiblity, but that's kind of the gist of what I'm thinking at the moment.
|07-24-2004 07:40 AM|
|xaamottomaax||The downward adaptation sounds as if it is an overcompensation of fuel in order to create a rich fuel mixture so knock will not occur while the MAF sensor is "catching up" to the MAP sensor or while there is a discrepency between MAP and MAF readings. Is this accurate?|
|07-23-2004 01:43 PM|
Firstly the WIS is not explicit in exactly what defines a "rapid load change" ... so even if there is a discrepency between the MAF and MAP, it may only use the MAP for a correction factor when the throttle angle is a certain percent, or the load request (pedal potentiometer) changes at a certain rate.
Secondly, adding fuel actually causes a DROP in power. That's part of where the downward adaptation comes into play.
On Nick T's car the 18% airmass correction between MAP and MAF readings tells me that the ECU may be using the difference between the two values when cruising and applying it at full throttle. That should theoreticaly FIX the problem, except that the change in VE at part throttle may not apply to full throttle, and different RPM bands.
Coincidentally though, Nick T does not seem to have any downward adaption. It's possible (though not likely) that the downward adaption was "fixed" after the '99 model year. (Nick has a 2000 I believe)
Still a number of things that are uncertain, but I still can't see where Tionic's theory fits into any of this, and I am trying to. The O2 sensor's readings shouldn't be affected by modifications to anything but the fuel system, and the O2 sensor itself. Oh well.
You're on the right track with the idea that the MAP sensor may be getting used all the time instead of MAF. Even if I think it may have some other factor to determine when it's used, I was suspicious of that as well.
|07-23-2004 11:04 AM|
|xaamottomaax||It seems from reading the excerpt from WIS that the MAP sensor value is only used for the fuel quantity calculation when there is a discrepency between the MAP and MAF sensors. All other times the MAF sensor is strictly responsible for fuel calculations. If this is the case, adding an exhaust would cause a constant discrepency therefore involving the MAP sensor in the calculation at all times. If the MAP sensor is then being used to calculate fuel quantity at all times due to the change in VE and the sensor discrepency that insues, wouldnt the change in VE be accompanied by more fuel to compensate for the extra air coming into the engine, therefore increasing power above stock levels? What causes the downward adaptation? Is it a fuel cut? Is it opening of the wastegate? Is it closing off the throttle body? What is the engine doing to adapt down when logic tells us the MAP sensor reading should be over riding the MAF sensor reading and the engine should be providing more fuel to compensate for the extra air in the engine not accounted for by the MAF sensor (and providing MORE power over stock)?|
|07-22-2004 10:21 PM|
Noooo no. What I mean is that in order for the engine to calculate what amount of fuel to put in, it needs to know how much air soooo ...
When you first open the throttle, the air goes from throttle to intake ports quickly, but the Mass AirFlow sensor doesn't read anything YET because it sits very far away from the throttle.
That would cause it to run lean for a second until the MAF sensor "caught up" ... so they use a MAP sensor which is connected straight to the manifold to correct the value that the MAF sensor is reading. The value is then expressed as milligrams/combust and then used for fuelling. The reverse happens when you quickly let off the throttle.
Now you go and put an exhaust on it, and the VE changes. So the calculated value the MAP reads and uses to correct the MAF is no longer correct. That means the correction in milligrams/combust under quick load changes in inaccurate.
The engine may also continue correcting until the values are the same (or within a certain tolerance). If the values never approach eachother again due to modified exhaust it may not stop correcting. Or it may take a long time, or some other problem.
When two sensors designed to measure/calculate the same thing read very differently bad things tend to happen.
Sorry if I sound like I'm repeating myself.
|07-22-2004 07:22 PM|
|07-22-2004 06:38 PM|
It wouldn't lower it much, but you're right it probably would lower the EGT a little, as long as it does not run lean.
See, now you're thinking.
A water sprayer on the OUTSIDE of the intercooler (like the EVO and STi) will make charge air temps cooler in warm weather, and that actually lowers EGT too.
Usually the EGT drops about the same level as the intake temp. 20 less degrees for intake, and 20 less for exhaust.
Not a big change, but just thought I'd tell ya.
|07-22-2004 06:26 PM|
|xaamottomaax||point well taken...and good explaination on the turbo's effort influencing backpressure. In my case where the exhaust system is maxed out and fighting to squeeze the extra boost of the stage 1 through the stock exhaust setup, the intake might be a nice benefit helping to lower EGT's by reducing back pressure...although not to the point of exhaust scavenging.|
|07-22-2004 06:10 PM|
"Also, I still do not understand if or how opening the intake to the turbo would change VE if the overall volume of the intake system after the MAF was not changed....after all, the amount of air entering the engine would not change as is the case with an exhaust where the amount of exhaust gas leaving the engine does change."
But, if it's easier for the turbo to pull air in, it doesn't have to work as hard, if it doesn't have to work as hard it reduces the backpressure by opening the wastegate. This reduces backpressure quite a bit and increases the exhaust scavenging ... more exhaust scavenging means more intake gasses getting into the engine even at the SAME boost pressure. (that's what happens when the VE changes)
So then it changes the VE ... just a lot LESS than an exhaust. It shouldn't be a problem, I ran a ghetto autozone airfilter on the dyno with my car, it adapted upwards with each run!
Things like air filters cause such a small change that it should not affect anything. I'm just saying to be careful!
Ionly want to make the point that any mod CAN cause problems, some don't.
|07-22-2004 05:36 PM|
"ive got a follow up question for that:
You were saying that the sensors are conflicting, and thus making alot of bolt on mods useless. If you upgrade your ECU software to say... stage 2 then add a bunch more bolt on mods will the ECU still do the same thing it does as stock and adjust the fuel/ air mix to produce the programed HP? or will it run lean?" Boxerchip
Unfortunately (or perhaps fortunately) most of the aftermarket sofware works in much the same fashion on a reprogrammed version of T7 as it does on stock T7. (At least to my knowledge.) Similarly with T5.
Any bolt on mod the ECU is not programmed for on any engine management system CAN cause problems. Usually it's no big deal, but sometimes it is.
As far as the sensors being in conflict, that's the best way I can explain T7 adapting DOWN. Even if the sensors are NOT in conflict it will not increase power very much. You will still get the same milligrams/combustion because of how T7 is designed, but you may reduce pumping losses slightly. (Which are unrelated, and affect mileage more than power.)
Trionic's theory was based off the O2 sensor giving bad feedback during a closed loop Multiplicative adaption window. But while those are common (30 seconds of every 5 minutes) they cannot occur during open loop.
And as even Mark E pointed out, in order for the ECU to make a multiplicative adaption it would need to first start to run a little leaner, or richer, than usual. And this should not happen because the Mass AirFlow sensor itself should still meter the fuel in exactly the same way, mods or not. So if it does not run too lean during a cruising closed loop multiplicative adaption window, it should not adapt badly.
Also, it only allows a 25% adaption before throwing a code.
Nick T is currently watching his modified stage 1 Viggen to see what sort of Multiplicative adaptions his vehicle registers. He's currently at 7% or so, but some adaption is normal.
Strangely, Tionic states that the MAP sensor is not used for anything but a backup. Nick T just got 18% as an "airmass correction" based on the MAP sensor data vs. the MAF sensor data. That means the ECU is "keeping track" of the difference between MAP data and MAF data. I would assume this is for more than just backup. Otherwise if there were a problem with the MAF sensor the MAP sensor would be totally useless as a "backup" because the airmass correction would possibly have corrupted the values stored in the ECU for the MAP system. No one ever makes a backup system dependant on the functionality of the main system. To do so is just bad engineering.
Anyhow ... we will see how things work out soon I hope. I don't mind being wrong at all. I just want it to make sense! For goodness sake then Navier-Stokes fluid dynamics equation is simpler than this! Even in Tripple Partial integral form.
|07-22-2004 05:32 PM|
Thanks for the "shape" explaination. In a 9-3 application where the filter often attaches directly to the MAF sensor, I can see where problems could arise. In the CAI setup designed for T7 9-3's and also in the intake for the 9-5 this would not be a problem as the air would have traveled up a tube mixing to uniformity prior to reaching the MAF sensor.
Also, I still do not understand if or how opening the intake to the turbo would change VE if the overall volume of the intake system after the MAF was not changed....after all, the amount of air entering the engine would not change as is the case with an exhaust where the amount of exhaust gas leaving the engine does change.
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