eng92

iTrader: (3)

I am looking for some 3.5 WOT airflow data in 2-6.5K RPM range.

I did a couple of pulls with the stock Z IM installed and compared the airflow vs the VQ35 with stock intake (functioning VIAS) and my VQ30 numbers from last year. Intake temperatures were within a couple of degrees of one another.



The data was all recorded on an Auterra OBD-II scanner.

Surprisingly the measured airflow for the 3.0 was on par with the 3.5 up to about 4.5K.
I figure that either I have too much restriction in my exhaust (stock muffler and cat) or that the VE of the 3.5 really blows below 4.5K.

PM me if you have any data I can use for comparison.

The driving impression with the Z IM is reflected in the curves above. There is a definite loss of midrange punch but the rev limiter comes quicker once you hit 5.5K. It is also interesting that the airflow even with the Z IM stopped increasing after 5.8K (5.5K for the stock 02 max IM)

hightuner

iTrader: (1)

great post

You always have very interesting thread

I guess its the exhaust too

virgilio7

i'll try to datalog with the auterra. my car is not running right and the maf could be one of the reasons.

DandyMax

iTrader: (7)

Would be interesting to compare with a 3L with 00VI as well... I will have some data to add in a couple weeks I hope. Might also be doing some TB comparisons.

Should also get some data from Jime to compare modded Z manifold and no VTC/VTC etc.

Is your Z mani the rev-up version? I suspect using the Maxima ECU vs the Z ECU will have an effect too...

Also, what gear were your runs done in?

eng92

iTrader: (3)

Jime is going to get some data if it ever stops raining.

My im/collector are from an 05 Z, but it is the non-rev-up version.

The only effect on airflow that the ecu would have would be in regards to vtc operation. I have a couple of runs I did last week with the vtcs unplugged that I can add to the graph for comparison.

Is there a lot of scatter in your EU maf voltage data? I find I have to use a 20-point moving average regression just to get a smooth curve through the points. Regression curves through consecutive runs match up perfectly so I do not think it is electrical interference. I also ran a piece of shielded cable and that didn't make a difference. I have a brand new spare maf that I may try.

I always run in 3rd. 2nd is too short for the sampling rate through the OBD-II port. 4th takes too long to run out to redline on the stretch of road I use. There is also always the possibility of deer or other forest creatures running across the road in front of me.

DandyMax

iTrader: (7)

I figured it wasn't the rev up... would be interesting to see one of them also.

I'd like to see the VTC difference yes please...

Yeah I don't think it's the wiring on the car, the lines seem to be shielded well enough. Scoping the cam and crank signals early on in the EU development process I realized the shielding was adequate. The regression was on the above data through the Auterra? Or did you mean on the EU data. I'd have to check my EU data logs to refresh my memory on what the MAF voltage was like. What magnitude of variance were you finding?

Ok thanks just wanted to confirm.

eng92

iTrader: (3)

Here is another colorful one.

All the data was collected using my EU (20 ms sample rate). I made 4 runs within a 10 minute period (2 with the VTC solenoids unplugged and 2 with them connected)

The blue dots are the raw MAF voltage data for one of the runs The solid blue line is the regression curve through this data. The other three data sets exhibit similar scatter so I left them off for clarity.

The timing data for similar runs is virtually identical. The "VTC-less" runs enjoyed more timing in the low to mid rpms due to the reduced air flow.



If anyone has an airflow vs voltage calibration for the 5th gen MAF, let me know. I will put a crude one together using my OBD-II airflow data.

IceY2K1

iTrader: (3)

Are you using the drive-by-wire?

eng92

iTrader: (3)

Affirmative.

Are you thinking throttle plate closing?

That might partially explain the limit on the maximum airflow in the upper rev range, but it certainly would not account for the minimal difference in airflows that I am measuring between a 3.0 and 3.5 below 4.5K.

IceY2K1

iTrader: (3)

Yes, and I agree that's not the only issue.

Just a guess, but I believe you need TS to flash your ECU with Z/G VTC maps to fully take advantage of the 350Z IM. Also, SR20DEN has mentioned his theory that the FWD VQ35s were torque limited for traction, so that may help the 2500-4500rpm range.

nismology

iTrader: (8)

Can somebody please explain to me how two motors can have similar volumetric efficiency's in the mid-range but be seperated by about 50 lb-ft of torque in their stock forms?

Hoooper

engine size??

nismology

iTrader: (8)

Not really. VE takes the engine displacement into account already.


I realize that a longer stroke automatically raises torque since the connecting rod has more leverage on the crank but what else could it be? I know the 3.5 has less valvetrain losses and less reciprocating mass but could that account for the huge torque discrepancy? Less internal friction?

Hoooper

although the volumetric efficiency takes engine size into account, i still think thats it. you mean the VE as expressed by a percent right?

eng92

iTrader: (3)

Actually I have not even quantified the VE yet. Just airflow. Because of the larger displacement, the VE I am seeing on my 3.5 is considerably lower than what I previously estimated for my 3.0.
Here are some VE curves that I came up with based on air flow, air density, engine displacement and rpm.
Take this data with a grain of salt though as the whole point of this thread is to find what kind of numbers other people are seeing because I think mine are severely lacking.




To answer your question, remember that torque is a product of piston area, stroke and effective mean combustion pressure. The 3.5 is already out in front of the 3.0 by about 17% based solely on its larger geometry.

The combustion pressure portion is obviosly affected by airflow but the tuning (AFR & timing) also plays a large role. You really cannot estimate torque by comparing VE between engines of different displacements.

Don't get me wrong though. I am very impressed with the low/midrange torque that my 3.5 has. At WOT in 2nd, the front wheels break loose at around 4K when the VIAS opens. I cannot go WOT in 1st gear at any rpm without breaking traction. I am not complaining. It is just the numbers I am seeing do not make sense to me.

nismology

iTrader: (8)

Well according to the first post the 3.5 isn't moving that much more air in the mid-range yet it's making much more torque. If it came down to engine size, the 3.5 should be moving more air for a given barometric pressure because of the increased displacement. I was always led to believe that VE and engine torque are directly related. These findings can mean two things...either the graphs are flawed somehow (not apples to apples comparison) or that the 3.5 making more low-end and mid-range torque has absolutely nothing to do with swallowing more air, which i find terribly hard to believe.

nismology

iTrader: (8)

Part of the reason that i was confused was because the the stock 4G ECU has more timing advance in the mid-range than the 2k2 ECU.
That makes sense. I keep forgetting that VE is a percentage.

nismology

iTrader: (8)

I guess the heart of my confusion is not being able to understand how or why the 3.5 isn't swallowing that much more air than a USIM 3.0 up until past 5000 RPM.

eng92

iTrader: (3)

Exactly my dilemma. Hence this thread. I did not want to start pulling things apart before I see what other 3.5s are getting.

I am tempted to bring my Auterra down to the local Nissan dealer and take some test drives

6spd_Hayes

iTrader: (3)

Here is a comparison point for you (if you can use it). I took data the last time I was at the track (1/8th mile) All of these runs are at WOT, but in second gear. The data was taken by an UpRev Cipher DDS. Unfortunatley I only have 4k up to redline (or where I shifted). I will try to get some 3rd gear runs from 1k up thru 6600 sometime soon for you to have a comparison to. I will also attach a link of where you can download the excel spreadsheet and chart.



Here is the link to the Excel Data:

http://hsvracing.com/upload/6spd_Hay...20vs%20rpm.xls

eng92

iTrader: (3)

6spd_Hayes - Thank you for the data. You do not need to get any more.

Your peak airflow at redline is no higher than mine so that tells me that there is nothing unusual going on with my vehicle.

I added your data from run 2 to the graph and changed the scales for clarity.



Anybody with scanners that have friends with 350Z or g35s; please feel free to contribute.

6spd_Hayes

iTrader: (3)

I will add a little addendum to my data, I believe I have a MAF that is going south. (going south meaning I think I have an excessive buildup of oil on the heated filament, causing the MAF to be hyper-sensative, therefore dumping excess fuel). (Again, just a theory I am working on). My car has been running excessively rich for about 7 months.

eng92, I will see what I can do about getting the data you are looking for from a stock Z33. My Cipher DDS can get that data from most any newer Nissan.

eng92

iTrader: (3)

That would be great if you could do that. If the conditions are available when the data is taken, I could use that info as well.
I can then present it all as volumetric efficiencies vs rpm and reduce the effect of the environmental conditions on the results.

SR20DEN

iTrader: (7)

You can't use MAF signal to do a true comparison bewteen different intake manifold setups. ANY changes to the intake setup affects the MAF readings. To make this more accurate you have to log the A/F data and throw it in the mix. Then you would really need to make the A/F corrections and log what is being fed to the ECU. Or just do dyno comparisons of both setups with identically corrected A/F ratios.


Basically what I am trying to say is that our MAFs can't be trusted and they can be easily manipulated to display just about anything. I have personally seen 5-10% differences in readings just from different setups in front of the TB which doesn't mean 5-10% differences in power levels.

eng92

iTrader: (3)

Your point is well understood, but it is the maf voltage that primarily determines the engine tune (ipw, timing) in open loop operation. You can change your afr however you want but that is not going to affect the physical quantity of air entering the engine.

I guess I should have prefaced my thread by saying unconditioned maf data only.

The ecus maf voltage/airflow calibration is based on a specific velocity profile for the airstream passing it. Of course any devices placed upstream of the maf will introduce varying disturbances (including rotational components) to the flow profile. As one of the graphs above clearly shows, the maf voltage fluctuates wildly. The ecu must sample at a very high rate and perform some time averaging to come up with a realistic inlet airflow.

I am not trying to look for minor differences in metered airflow. I would have expected there to be a substantial difference between a 3.0 and a 3.5 engine throughout the rev range based solely on displacement.

Other than velocity profile, the next largest impactor of maf voltage will be air quality (ie temp and water content) Unless you are testing under lab controlled conditions, nobody really knows either of these that accurately. Underhood temperatures vary substantially depending on vehicle speed. The only time I have ever seen really consistent maf data during identical runs was when I was running a fender mounted air filter. I can post maf data for air inlet temps from -15C up to 40C and you will see what amounts to a constant vertical offset in the voltage throughout the rev range because of the density change.

I am not sure why you want to bring AFR into the mix. I only want to know how effective the engine is as an air pump. What you do to the air once you get it into the engine is more the subject for a tuning discussion.

Kevlo911

iTrader: (36)

More effective pump sucks in more air

SR20DEN

iTrader: (7)

Because I am trying to explain that the MAFs we have are not good measuring tools for the task you're trying to accomplish. They are easily fooled to THINK there is more or less air being pumped in where there could be no real difference at all.

eng92

iTrader: (3)

I fully understand your pov but it is the only tool that everyone has. There is no substitute for dyno numbers.

Again I am not looking for differences of a few percent, I am looking for something in the 15-20% range (on the order of the displacement difference between a 3.0 and 3.5)

If you can correct for temperature, our MAFs are more than capable of metering differences of that magnitude.

nismology

iTrader: (8)

I've been doing some thinking on this and the increase in combustion chamber volume can not possibly account for the torque increase that the 3.5 saw over the 3.0. IMO, the geometry of the motor itself account for most of it. I now understand what the graphs above are saying.

A motor might not necessarily have to have higher mass airflow overall to make more HP/TQ. My brother and i were discussing why exactly the 3.5 makes more torque than the 3.0 and it kinda dawned on me that a large portion of torque increase via larger displacement might be a product of the motor's geometry. All other things being equal, there are 3 ways to make more torque to my current understanding. Make a bigger explosion via more air and fuel, increase piston surface area so more work can be done with a given applied force (bore), or increase the connecting rod's leverage on the crank by lengthing the distance between the crank centerline and the rod bearing surface (stroke). This means that the VQ35 doesn't necessarily have to swallow more air at a given time to make more torque than the 3.0. This is not to say that the 3.5 is a less efficient pump than the 3.0, but it's relatively modest displacement increase might not allow it to swallow that much more air than the 3.0 at lower revs. As for why the 3.5 can swallow more air at higher RPM's is because maybe the improved breathing capacity of the 3.5 heads and the higher valve lift (and maybe duration?) allow it to swallow more air overall at higher revs.

Even if my theory is flawed, if you look at the graphs posted above it's clear that mass air flow and torque output are NOT directly related.

eng92

iTrader: (3)

Your theory is not flawed, I said exactly the same thing in not so many words back in post #15
The dek does injest more air than the de at higher revs. The piston/crank geometry of both engines is the same, therefore the only way for one to maintain torque at higher rpm is to have higher combustion pressures (ie. more air). This is of course assuming both engines have the same tuning. Although I would expect that the factory ignition timing in the upper revs would be lower on the dek than the de to prevent detonation due to the higher VE.

nismology

iTrader: (8)

My apologies. I was basically just explaining it to everyone else and kinda edumacating myself as i typed it.


What i'm saying is that the extra air that it is seeing at higher revs is air that was already in the IM but bounced off the closed intake valve, not new air, if that makes any sense.

eng92

iTrader: (3)

This is not a closed system we are dealing with here. The pressure wave created by the resonance effect does force more air into the cylinder (kind of like a passive supercharging effect) but the air has to come from somewhere in a steady fashion. The intake valve lift and duration are fixed so the only way to get more air through the open valve is to increase the flow velocity. In the case of the dek, the 00VI increases this velocity. Higher flow velocities mean lower static pressures (ie higher vacuum) and hence more air drawn in through the intake.

nismology

iTrader: (8)

Makes sense now.


OK. No more OT.

96sleeper

iTrader: (4)

I tried to take one data sample earlier, auterra is a little slow on a 4th gen hence the gaps in the measurements. Also, I couldn't start much lower since I was already on the interstate.

MAF...RPM
136...4800
147...5013
154...5225
163...5438
167...5650
180...5863
199...6038
208...6213
216...6400
217...6563
221...6700
223...6863


My car is not too good for comparison. 4th gen MAF and ECU, JWT knockoff cams, and similar intake manifold to 6spd_Hayes. Also, I have a SAFC-II which is tuned. I am removing quite a bit of fuel between below 5500rpm which is altering the numbers. Above that it is maybe 1-2% which would not affect it too much.

eng92

iTrader: (3)

Thanks for the data. As long as the MAF matches the ecu, the airflow data obtained is representative. However your AFC conditioning makes the data no good for a direct comparison.

If you are indeed performing minimal AF corrections above 5.5K, your cams and modified intake are doing a good of increasing airflow past that of the stock VQ35 (maxima) which ceases to increase above that rpm level.

Hey Jime, Did you get any numbers yet?

eng92

iTrader: (3)

Anybody had this done?

I talked with TS today and you have to move up to the F-Spec if you want any map (VTC, ignition or fuel) changed. The price difference is $150.

nismology

iTrader: (8)

I think it would be worthwhile. Since you are using the Z IM you should use the Z VTC maps to take advantage of the different intake length, volume, and resonance characteristics.

Jime

iTrader: (10)

I am emailing you a couple of files now.

BTW I installed a set of thermo insulated gaskets at the heads as well as the Aramid thermal isolating gasket from Motordyne that is installed between the lower plenum and intake manifold. Last night I did approx 8 runs from 0 to over 100 in about 40 mins then drove 2 miles back home. I measured the manifold temp it was 70 deg F and the timing chain cover was 140 deg F. The intake manifold was actually cool to the touch.

The hood does close with the 5/16" Motordyne spacer.

eng92

iTrader: (3)

Thanks for the data Jim. I will post the numbers up once I can convert all the airflow data to a common reference.

What MAF setup are you using? I remember you talking about mounting a 4g MAF in a larger tube but I don't know if that went anywhere. I have spare 4g and 5g MAFs here so I can set up a little bench flow tester to correlate their output voltages.

Also, What cams are you using?

Jime

iTrader: (10)

Stock MAF and JDM cams.

I'm still going to mount a 4g MAF in a 3.5 tube but just have to finish up some other stuff first. I'm like Dan I think he dropped off the face of the earth since he got his car out of storage.

BTW my manifold is touching the hood but not where yours is, mine is at side closest to the rad where those ribs are built up for decoration I think. I have shaved it down but its just touching with the 5/16" spacer.