What is an INTAKE really worth when you are TUNED?
Dec 29, 2008, 12:02 PM
#79
(quote from sti2evox:
So, ecuflash does not have maf scaling, but the AP does? What about ecutek? I have seen the tables in ecuflash, and it's definitely capable of tuning the A/F ratios, so what's the difference between this and maf scaling? Are there two different aspects of tuning the A/F ratios? Also, I agree that when using an intake or drop in filter that part of the gain is from decreasing pumping losses, but they all seem to show leaner a/f ratios as well. If the maf sees more airflow, then isn't the ecu programmed to add fuel to maintain the A/F ratios as per the maf scaling tables or whatever takes care of that? I'm confused why the A/F ratios are leaned out in spite of this. Do you have any insight into this?"
ECUflash does have MAF scaling for the EVO 8-9's. I personally have not seen anyone tune the car using it without also using the AFR tables to further adjust the fuel. I could be wrong but the maps I have seen from various tuners do not use the MAF scaling to solely adjust AFR's.
The ECU doesn't adjust AFR's at WOT, WOT is in open loop and the ECU doesn't use 02 feedback in open loop, only in closed loop. This is also the case on cold start, the ECU doesn't use the 02 sensor on initial start up, it runs off a pre-determined map. This is why much of what TTP and I are trying to explain is important. The MAF does add more fuel in closed loop, that is why you see people talk about the STFT, LTFT's. If the tune is way off from a MAF that isn't calibrated correctly or the injectors are too large the car will throw a CEL for the being too rich/lean or a variety of other codes. The car will add/subtract fuel in closed loop based on the 02 feedback but if the amount of feedback is more than the allowable difference you get the CEL.
So, ecuflash does not have maf scaling, but the AP does? What about ecutek? I have seen the tables in ecuflash, and it's definitely capable of tuning the A/F ratios, so what's the difference between this and maf scaling? Are there two different aspects of tuning the A/F ratios? Also, I agree that when using an intake or drop in filter that part of the gain is from decreasing pumping losses, but they all seem to show leaner a/f ratios as well. If the maf sees more airflow, then isn't the ecu programmed to add fuel to maintain the A/F ratios as per the maf scaling tables or whatever takes care of that? I'm confused why the A/F ratios are leaned out in spite of this. Do you have any insight into this?"
ECUflash does have MAF scaling for the EVO 8-9's. I personally have not seen anyone tune the car using it without also using the AFR tables to further adjust the fuel. I could be wrong but the maps I have seen from various tuners do not use the MAF scaling to solely adjust AFR's.
The ECU doesn't adjust AFR's at WOT, WOT is in open loop and the ECU doesn't use 02 feedback in open loop, only in closed loop. This is also the case on cold start, the ECU doesn't use the 02 sensor on initial start up, it runs off a pre-determined map. This is why much of what TTP and I are trying to explain is important. The MAF does add more fuel in closed loop, that is why you see people talk about the STFT, LTFT's. If the tune is way off from a MAF that isn't calibrated correctly or the injectors are too large the car will throw a CEL for the being too rich/lean or a variety of other codes. The car will add/subtract fuel in closed loop based on the 02 feedback but if the amount of feedback is more than the allowable difference you get the CEL.
You need to have a 2D MAF voltage vs. load table and an AFR table (in load vs. RPM).
Reason why…
This is all hypothetical and the numbers are no where near realistic.
Example 1a.
Lets say on a stock car, in the 2D table at a 3V of MAF voltage you have 200g/s of air going by the MAF. So now in your AFR table at 4000RPM and 200g/s you have 11:1 AFR inputted there. Everything is great, car runs well no problem.
Example 1b.
Now lets put a larger diameter MAF housing on the car. No other changes.
We still have the same amount of air going into the motor as with the stock housing but because of this larger diameter housing, our MAF voltage is now 2.5V, which is 150g/s. Go back to the AFR table and at 4000RPM and 150g/s we have 12:1 AFR inputted there. All of the sudden we are now running lean at peak torque…things go boom then.
Example 1c.
Lets leave the larger diameter MAF housing on the car. But let’s go into the 2D table and adjust our MAF calibrations for the larger MAF housing. We now know that at 2.5V of MAF voltage, our airflow is really 200g/s, not 150g/s. So we bump that number up to 200g/s. Now when the ECU sees 2.5V at 4000RPM, it goes to the 4000RPM/200g/s load site in the AFR table, which is 11:1 AFR and all is good again.
This all makes sense in my head but after trying to type this answer out, I think I didn't do so well.
Reason why…
This is all hypothetical and the numbers are no where near realistic.
Example 1a.
Lets say on a stock car, in the 2D table at a 3V of MAF voltage you have 200g/s of air going by the MAF. So now in your AFR table at 4000RPM and 200g/s you have 11:1 AFR inputted there. Everything is great, car runs well no problem.
Example 1b.
Now lets put a larger diameter MAF housing on the car. No other changes.
We still have the same amount of air going into the motor as with the stock housing but because of this larger diameter housing, our MAF voltage is now 2.5V, which is 150g/s. Go back to the AFR table and at 4000RPM and 150g/s we have 12:1 AFR inputted there. All of the sudden we are now running lean at peak torque…things go boom then.
Example 1c.
Lets leave the larger diameter MAF housing on the car. But let’s go into the 2D table and adjust our MAF calibrations for the larger MAF housing. We now know that at 2.5V of MAF voltage, our airflow is really 200g/s, not 150g/s. So we bump that number up to 200g/s. Now when the ECU sees 2.5V at 4000RPM, it goes to the 4000RPM/200g/s load site in the AFR table, which is 11:1 AFR and all is good again.
This all makes sense in my head but after trying to type this answer out, I think I didn't do so well.
Dec 29, 2008, 04:35 PM
#83
True, but only when the turbo is really big. I think on a gt3076 or smaller, there wouldn't be much, if any, difference in power between the stock box with a drop in and an intake. Beyond that, I'd say that the stock box would become a restriction. Buschur said that the stock box is a good design and that it should be good up until about 500 whp, and as I said before, I read a test where an evo 8 at the 450 whp level didn't make any more power from an intake when compared to the stock box with a drop in. Unless you plan on going big, intakes are kind of a waste of money IMO.
Dec 29, 2008, 04:46 PM
#84
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This really isn't too difficult, but I test & tune various cars. When I create new maps I like to test them on my car first. Since most of the cars I tune have stock intakes, it makes my life easier to change my intake to stock.
Dec 29, 2008, 05:41 PM
#85
sti2evox, I didn't say the stock airbox was good and good for 500 whp, I feel the MAF sensor housing is good. I think that's what I said anyway. The stock airbox isn't as good as an open element filter for sure as we've tested back to back and putting our filter kit on for sure picks up power. Similar to TTP's test of taking the filter out of the stock air box.
Now, today I took a stock MAF housing off the shelf we had. I measured it. The ID of the stock MAF housing in it's smallest part is 2.8 inches and in it's largest end almost 3". Keep in mind people that the stock MAF housing is a perfectly smooth straight piece of plastic tubing, no ridges, no ripples, no bends. Just an almost polished finish inside that is 2.8" in it's smallest section. The MAF sensor itself is very small and protrudes into this housing. Also keep in mind that placing a 3" MAF pipe up to a GT35R with an open element filter on the end will easily flow enough for 600+ whp.
I will stand behind my decision to keep the stock MAF housing. I think changing it is retarded to be honest. No way in hell it's any type of restriction under 550 whp, no way.
slorice, you have a TON of experience with the Cobb software on the Subi's so thank you for the good explanation of how it works. Very good job.
Now, today I took a stock MAF housing off the shelf we had. I measured it. The ID of the stock MAF housing in it's smallest part is 2.8 inches and in it's largest end almost 3". Keep in mind people that the stock MAF housing is a perfectly smooth straight piece of plastic tubing, no ridges, no ripples, no bends. Just an almost polished finish inside that is 2.8" in it's smallest section. The MAF sensor itself is very small and protrudes into this housing. Also keep in mind that placing a 3" MAF pipe up to a GT35R with an open element filter on the end will easily flow enough for 600+ whp.
I will stand behind my decision to keep the stock MAF housing. I think changing it is retarded to be honest. No way in hell it's any type of restriction under 550 whp, no way.
slorice, you have a TON of experience with the Cobb software on the Subi's so thank you for the good explanation of how it works. Very good job.
Dec 29, 2008, 06:58 PM
#86
David, my bad. I misread your post about the maf pipe and thought you were talking about the box. 
Although I will say this; I read a test a while back (I'll try and see if I can find the link) where an evo 8 at ~450 whp range didn't really make any more power on an intake compared to the stock box with a drop-in, but then again I don't remember if the inlet pipe from the maf housing running to the turbo had been modified or not (not sure if that would even make much of a difference).
This was also on a dyno jet, so the numbers would probably be closer to the 390-400 range on your dyno. When you tested going from the stock box with a drop-in to an intake, was it at those power levels or higher? What were the gains? I'd be curious to see how your results compared to this other test that I read. I keep flip flopping back and forth between going to an open element filter, but I don't like the idea of short rams sucking in hot engine bay air.
I know people have different views on this, and some say that it doesn't matter because the turbo is just going to super heat the incoming air anyway but I still say, "colder in, colder out." Any thoughts or advice?
Although I will say this; I read a test a while back (I'll try and see if I can find the link) where an evo 8 at ~450 whp range didn't really make any more power on an intake compared to the stock box with a drop-in, but then again I don't remember if the inlet pipe from the maf housing running to the turbo had been modified or not (not sure if that would even make much of a difference). This was also on a dyno jet, so the numbers would probably be closer to the 390-400 range on your dyno. When you tested going from the stock box with a drop-in to an intake, was it at those power levels or higher? What were the gains? I'd be curious to see how your results compared to this other test that I read. I keep flip flopping back and forth between going to an open element filter, but I don't like the idea of short rams sucking in hot engine bay air.
I know people have different views on this, and some say that it doesn't matter because the turbo is just going to super heat the incoming air anyway but I still say, "colder in, colder out." Any thoughts or advice?
Last edited by STi2EvoX; Dec 29, 2008 at 07:06 PM.
Dec 29, 2008, 08:28 PM
#87
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Correct....colder in, colder out. Ideal gas law proves that. I did some calculations a couple years ago with 70* and 100* air temps going into the turbo. The outlet temps were like 60* or 70* different! I'll see if I can hunt my notes down.
Yes, yes I do. It was a good learning experience on how NOT to go fast!
Last edited by SloRice; Dec 29, 2008 at 08:32 PM.
Dec 30, 2008, 12:50 AM
#88
Ahh, makes perfect sense. So in short, the reason that the intake or drop in leans out the mixture is because in spite of the maf seeing more air, the ecu doesn't add fuel in open loop mode, only closed loop. Such a simple answer, yet no one was able to answer it until now. Thanks.
STi2EvoX, your question is based on some tests that showed leaner AFR with an aftermarket panel filter. I personally don't remember seing those. I only remember tests that showed hp gains on the dyno. May be there were some that I havent' seen. Can you pease check?
Dec 30, 2008, 07:11 AM
#89
This is confusing. In open loop the ECU doesn't have the feedback from O2, but it does read MAF and adds fuel in accordance with the pre-determined map. So, more air passing through the MAF sensor should mean more fuel added. That's why you trick the ECU by expanding the MAF housing and not by just removing the filter.
STi2EvoX, your question is based on some tests that showed leaner AFR with an aftermarket panel filter. I personally don't remember seing those. I only remember tests that showed hp gains on the dyno. May be there were some that I havent' seen. Can you pease check?
STi2EvoX, your question is based on some tests that showed leaner AFR with an aftermarket panel filter. I personally don't remember seing those. I only remember tests that showed hp gains on the dyno. May be there were some that I havent' seen. Can you pease check?
Dec 30, 2008, 07:18 AM
#90
I ordered an AMS intake knowing that once I tune it will become a lot less beneficial, but a lot of people have it in their upgrade path for reasons. For instance, I do plan on running a 35r eventually, where this will be of great use. Also I am waiting on ECUflash right now, and therefore the intake is a great mod for the present since that could be a while. Also it is better looking and sounds better. I also have a hard time believing that it doesn't make power over the entire powerband, after being tuned i mean. It might be similar peak performance, but to not pick up any power anywhere, its tough to stomach. Regardless, I knew what I was getting into and for the time being its a cheap tune to lean out that crappy stock one.
Also its always been one of the first performance mods, so people probably just assume it's a natural thing, which would explain why so many people offer them. I still say it's worth it, assuming you plan to go over 400whp, which a lot of people plan to do, but fewer make it there.
Also its always been one of the first performance mods, so people probably just assume it's a natural thing, which would explain why so many people offer them. I still say it's worth it, assuming you plan to go over 400whp, which a lot of people plan to do, but fewer make it there.