IPD plenum on stock 997TT installed=slight boost loss?
#18
06-01-2013, 09:50 AM
It's been a couple of years since I last logged anything. Perhaps that function is no longer available in the newer versions. In any event, I don't think the stock tune is keeping up with the bigger hardware. He should get a tune that delivers more fuel. Just my opinion.
#20
06-01-2013, 12:30 PM
You don't need a different tune for a plenum upgrade. I'm not an expert in Bosch Motronic, but I'll try to explain why.
The 997 Turbo Motronic DME/ECU runs based on a calculated load value, which takes into account RPM, MAF, boost, coolant temp, oil temp, intake air temp, etc. Someone on here probably knows exactly, but there are literally hundreds of things that can potentially affect the load calculation.
The mass airflow sensor (MAF) measures the mass of the air passing through it, which is important because we're dealing with a car that can produce a wide range of pressures both negative (vacuum) and positive (boost). Just measuring the volume of the air is insufficient, we need to know the mass of the air entering the engine. I'm not sure exactly what unit they are measuring in, but typically it is something like grams of air per revolution of the engine. Once this 'magic' load value is determined it knows how much fuel to inject into the cylinders, and it is monitoring in real-time on the exhaust side with dual wideband o2 sensors so it always knows the Air/Fuel ratio. The fuel trims correct for things like the type of fuel (Gasoline, 10% Ethanol, etc) or other slight variances it sees from the target AF ratio.
So what happens when you put your foot to the floor? The DME has a target parameter range for wide open throttle and attempts to hit it. Depending on the specific density altitude (pressure, temperature, humidity, etc) your boost may vary a little in order to hit that target. From what I've seen the boost gauge on the dash is an approximation, it does not actually read the true boost value.
This is all great, but why do you not need a retune for the plenum? The system is measuring air coming in, hitting the targets it wants to hit, and measuring the air coming out to make sure it is within parameters. If that isn't happening correctly, it will set trims (such as fuel trim) in order to get there. If things are too far outside of the parameters for it to adjust to them (or things look unsafe) it will put the car in limp mode and/or throw a code to let you know something is wrong. For something as innocuous as an intake plenum in the middle of the system it isn't really going to have that much effect. Maybe you could say some of the throttle curves need to be tweaked as it may change airflow characteristics around the throttle body - but that is *really* reaching for a reason and would affect general drivability, not wide open throttle performance.
What you *really* get out of a flash tune for these cars is changing the parameters. Increased boost targets, leaner air/fuel (lambda) targets, more ignition timing advance, etc. There really isn't as much magic in it as people on this forum tend to believe, but it is not trivial to open the system up to connect to it, download the tables, modify them, and upload it back to the DME. That's where the difficulty lies, and why there are only a few places that can do it (i.e. GIAC, Softronic). Of course once you get to a certain point, you may flow more air than the MAF sensor can accurately read. Or some tuners disconnect the MAF sensor entirely and run based on engine speed & intake air pressure (speed/density) but that's a whole other topic of discussion
.
The short version of this is, wait until you get an exhaust before you flash the car, or talk to the tuner and make sure that there is enough adjustment range in the calibration to account for either scenario.
The 997 Turbo Motronic DME/ECU runs based on a calculated load value, which takes into account RPM, MAF, boost, coolant temp, oil temp, intake air temp, etc. Someone on here probably knows exactly, but there are literally hundreds of things that can potentially affect the load calculation.
The mass airflow sensor (MAF) measures the mass of the air passing through it, which is important because we're dealing with a car that can produce a wide range of pressures both negative (vacuum) and positive (boost). Just measuring the volume of the air is insufficient, we need to know the mass of the air entering the engine. I'm not sure exactly what unit they are measuring in, but typically it is something like grams of air per revolution of the engine. Once this 'magic' load value is determined it knows how much fuel to inject into the cylinders, and it is monitoring in real-time on the exhaust side with dual wideband o2 sensors so it always knows the Air/Fuel ratio. The fuel trims correct for things like the type of fuel (Gasoline, 10% Ethanol, etc) or other slight variances it sees from the target AF ratio.
So what happens when you put your foot to the floor? The DME has a target parameter range for wide open throttle and attempts to hit it. Depending on the specific density altitude (pressure, temperature, humidity, etc) your boost may vary a little in order to hit that target. From what I've seen the boost gauge on the dash is an approximation, it does not actually read the true boost value.
This is all great, but why do you not need a retune for the plenum? The system is measuring air coming in, hitting the targets it wants to hit, and measuring the air coming out to make sure it is within parameters. If that isn't happening correctly, it will set trims (such as fuel trim) in order to get there. If things are too far outside of the parameters for it to adjust to them (or things look unsafe) it will put the car in limp mode and/or throw a code to let you know something is wrong. For something as innocuous as an intake plenum in the middle of the system it isn't really going to have that much effect. Maybe you could say some of the throttle curves need to be tweaked as it may change airflow characteristics around the throttle body - but that is *really* reaching for a reason and would affect general drivability, not wide open throttle performance.
What you *really* get out of a flash tune for these cars is changing the parameters. Increased boost targets, leaner air/fuel (lambda) targets, more ignition timing advance, etc. There really isn't as much magic in it as people on this forum tend to believe, but it is not trivial to open the system up to connect to it, download the tables, modify them, and upload it back to the DME. That's where the difficulty lies, and why there are only a few places that can do it (i.e. GIAC, Softronic). Of course once you get to a certain point, you may flow more air than the MAF sensor can accurately read. Or some tuners disconnect the MAF sensor entirely and run based on engine speed & intake air pressure (speed/density) but that's a whole other topic of discussion
.The short version of this is, wait until you get an exhaust before you flash the car, or talk to the tuner and make sure that there is enough adjustment range in the calibration to account for either scenario.
Last edited by rix; 06-01-2013 at 12:34 PM. Reason: Silly grammar mistakes. Easiest way to separate signal from the noise on the internet? Ignore people who can't spell.
#21
06-01-2013, 12:59 PM
Registered User
Join Date: Aug 2004
Location: Long Island, NY
Age: 62
Posts: 6,379
Rep Power: 344 
#22
06-03-2013, 12:29 AM
There are target loads and then there are actual loads....If there are any leaks due to a faulty check valve or whatever, then I agree and all bets are off. If there are no leaks, however, then I believe that the larger TB/plenum with a stock tune is the culprit. When you suddenly mash on the pedal the air sees an instant increase in volume which leads to a pressure drop and reduction in mass flow. So it can have an opposite effect and act as a restriction at sudden WOT if there is not enough upstream pressure. Can a stock tune make up for this? I have my doubts. In any event, you should get a tune no matter what just because it will make you happier. 
#23
06-03-2013, 08:49 AM
Join Date: Jan 2013
Location: Atlanta
Posts: 170
Rep Power: 21
All very well and true. My plan was to get an exhaust before the tune. The IDP plenum was just because it was there. There isnt a huge reason to do a tune before I get the exhaust complete but that is an entire conversation in itself... I have to figure out which way to go there but it needs to be done either way and the tune will immediately follow.
So my only real question at this point is...what exactly does this check valve do??? I can only assume that its a one way valve of sorts. If I understand correctly, the hose that connects to it is a crankcase breather... which in my uneducated assumption, the check valve would bleed off extra manifold pressure (caused by positive vaccuum ie boost) as to not over pressurize the crankcase? Too much pressure in the crankcase would cause additional blow by on the piston rings and perhaps cause things like front and rear main seal leaks correct?
If all of that assuming is correct in fact, I see the issue that needs the check valve, but Im still missing why the *boost levels would be negatively affected. Boost is a calculation of manifold pressure... while all of the info in the 'short version' by RIX is well said, and true, the fact is that the volume is no more on the smaller IDP plenum. Diameter is the same as stock on the 74mm (obviously the 83mm doesnt apply to this rule) where its different is the "ramp" in the center that directs the flow after the throttle body. This should help the flow and scavenge less. Perhaps less lag, faster spool, and more midrange HP but the volume of the plenum if anything is less as a reult of the ramp.
The only thing that makes sense to me of why manifold pressure would possibly be less is that if the ECU is sensing the increase in crankcase pressure, maybe its compensating insome way as a result???
So my only real question at this point is...what exactly does this check valve do??? I can only assume that its a one way valve of sorts. If I understand correctly, the hose that connects to it is a crankcase breather... which in my uneducated assumption, the check valve would bleed off extra manifold pressure (caused by positive vaccuum ie boost) as to not over pressurize the crankcase? Too much pressure in the crankcase would cause additional blow by on the piston rings and perhaps cause things like front and rear main seal leaks correct?
If all of that assuming is correct in fact, I see the issue that needs the check valve, but Im still missing why the *boost levels would be negatively affected. Boost is a calculation of manifold pressure... while all of the info in the 'short version' by RIX is well said, and true, the fact is that the volume is no more on the smaller IDP plenum. Diameter is the same as stock on the 74mm (obviously the 83mm doesnt apply to this rule) where its different is the "ramp" in the center that directs the flow after the throttle body. This should help the flow and scavenge less. Perhaps less lag, faster spool, and more midrange HP but the volume of the plenum if anything is less as a reult of the ramp.
The only thing that makes sense to me of why manifold pressure would possibly be less is that if the ECU is sensing the increase in crankcase pressure, maybe its compensating insome way as a result???
#24
06-03-2013, 08:51 AM
I do not have any tech data or times. In my curiosity I did make a call to IPD and talked to the guys there. They were very helpful and more than accommodating. He mentioned that it sounds like an issue with the check valve located on the back of the plenum. From the pics on his site, the one that was on there appeared to be older design and he did say that the have changed. IPD is kindly sending me a new one which he thinks should take care of the issue assuming that the rest of the install is correct. I wish there was a better way to check for boost leaks...
Kudos to IPD for great service and supporting their product. Even though this was purchased used they stepped up. Its likely a very inexpensive part, but regardless they are helping to make it right and that goes a long way in this world. Thanks Mike and Greg for your help
Kudos to IPD for great service and supporting their product. Even though this was purchased used they stepped up. Its likely a very inexpensive part, but regardless they are helping to make it right and that goes a long way in this world. Thanks Mike and Greg for your help
So have you received the new part yet ?
#25
06-03-2013, 09:05 AM
Join Date: Jan 2013
Location: Atlanta
Posts: 170
Rep Power: 21
Not yet, it was just friday that I spoke with them so I wouldnt expect it till today or perhaps tomorrow
#26
06-03-2013, 09:07 AM
I'm interested in your outcome as I might have the same problem.
#27
06-30-2013, 01:55 PM
Registered User
Join Date: Jul 2011
Location: Montreal, Quebec
Posts: 214
Rep Power: 25
Please update on this as I also noticed a boost loss on the boost gauge after installing my 74mm IPD Plenum and IPD High Flow Y-Pipe. However, I don't feel the car less powerful. My boost gauge shows 0.9 BAR in normal mode (I'm pretty sure I had 1 BAR before) and I get 1.1 BAR in sport mode (instead of 1.2 BAR before).
I really like this theory and also that OEM boost gauge is not 100% precise.
I really like this theory and also that OEM boost gauge is not 100% precise.
#28
06-30-2013, 05:05 PM
Join Date: Jan 2013
Location: Atlanta
Posts: 170
Rep Power: 21
Immediately after replacing the check valve it was much the same. 0.8-0.9 I didn't care to take it off a third time so just drove it for a while. Not sure if the computer needed to "re-map" itself so to speak... But after quite a few driving cycles it's better. It pegs 1 bar and 1.2 in sport every time. Often so under more load, like 4th at 60 and floor it. Seems like boost backs off over 4k rpm when more appropriately geared like say rollon power in 2nd at 25 kinda thing but that systems to be the norm in all the research I have done.
At the end, I'm not disappointed but I can't say that it's noticeable, or much of a particular improvement. Spooling speed seems the same to me. That money could have been better applied toward the exhaust and tune which would have been significant...but it's there now! And will stay.
At the end, I'm not disappointed but I can't say that it's noticeable, or much of a particular improvement. Spooling speed seems the same to me. That money could have been better applied toward the exhaust and tune which would have been significant...but it's there now! And will stay.
#29
02-24-2017, 01:24 PM
I have the 83mm plenum from IPD and I have a shot check valve too. I pressure tested the system and it was the only leak I found. Now the pressure is holding nice and steady.
