Ok, everyone knows my setup so dont have to go over it, right now my manifold is simply a VIAS delete (non SSIM). Lately I have been thinking about our manifolds nonstop, and how they might be providing uneven flow since more than 2 people have reported higher compression at rear bank, so I got myself a second Wideband.

Conditions:
10psi-11psi, no methanol/water, timing near stock only taking away -4 so about 18-20deg(from 4k to 6k)

Conclusion:
Both banks have completely different AFR and as far off as more than 1.5points. The interesting thing is below aprox 5300rpm the rear(firewall) bank is much leaner, however above the 5300rpm the front bank starts to lean out. By the looks of the log the front bank has a way smoother and more linear AFR curve, almost perfect line however the rear bank is really unstable.

Check out the picture below of a screenshot.
In the Logworks screen, where it shows 5 seconds, disregard that huge spike, AFR went rich I had to let off because it was boggin and down in the 8-9afr (both banks) and then get back on the gas.

 

Well, the EU does allow you to add/pull fuel on a cylinder by cylinder basis...

 

Correct(already made adjustment, just havent relogged), and thats why I invested in the second wideband. I am just showing the discovery since I dont think it has ever been shown.

 

What is that due to, anyways? Fuel rail design?

 

I dont think its fuel rail, My fuel rail is from an 04, so basically its one entrance that splits into both sides, so pretty even. It has to be the manifold, im pretty confident it is.

 

There you go, thinking again... great job with dual A/F meters... When I do compression checks, the UIM is off the engine - and I think most people do it that way - so the UIM is not a factor here. But - there does seem to be a difference in pressures from the front bank to the rear bank, from several people - including me when I compression-checked my engine (no UIM) before installation. I figured that there were so many new things that I didn't know what it meant. Still don't..

Does a stock 2002-200x Maxima show the same difference in compression readings? Do only the 3.5s installed with 3.0 timing gears have this problem?

 

Thanks man.

Well the people that I know have done compression test have done it without manifold (specially since theres no other way with the 3.5 manifold blocking the rear). Also, very interesting that you mention the 3.5/3.0timing stuff because I was wondering "what if its the spacers!?" But then I thought, well if the spacers werent made properly then the issue would be on both banks, since both sets are identical. I am willing to bet, its the manifold causing this.

 

definitely an intake manifold related issue. what is your IM setup?

 

stock nongutted 3.5 fwd manifold with vias delete. and spacers.

 

I agree -that could be the reason for unequal A/F readings - didn't you have a SSIM manifold to start with? Testing with both manifolds could be revealing. But, compression tests are a different issue - and there are many reasons for funky readings. I vote for you testing both types of UIMs.

How did you install two A/F probes?

 

Yeah I was thinking about testing the SSIM, but the griding job inside is really crappy, not smooth at all. so I have to invest more time in making it smooth.

Just removed the narrowband o2 sensors and put the wideband sensors in there (on each leg of the ypipe)

 

I think the ssim will help but not much. What I want to see is what the a/f looks with the vias installed and closed.

Question, what a/f was the car tuned for when you did the test

 

Well it was tuned for high 10s low 11s(with a single WB at the collector). Which is a good thing I did that because if I was tuning for say low or mid 12's. that means the banks individually would have gone into the 13-14 range.

Yeah, I am def going to setup the vias, do doubt about that.

 

Nice work!

 

Damn that sucks, atleast the em allows you to tune each bank so you can fix the problem

Hopefully the 00VI doesn't have this problem

 

so are you saying that you think the compression difference from the front and rear banks is because your intake manifold?

 

streetzlegend did you pull of the top of the manifold and do the comp test like we talked about ?
If so this is not looking good .This is odd that this will happen on a V6 i will look into this and see what come's out of the bag .
If it is the manifold hit me up and we will see what we can come up with to fix this
Mack

 

My theory is that there is carbon build up in the rear bank, caused by the uneven distribution of air/afr. So yeah.

 

Yeah with our manifold the only way to do a comp test is to remove it. So yeah thats what i did.

It has to be the manifold, i am going to test out the vias when i get one to see how it compares.

 

Making some progress, I am focusing on making corrections to the rear bank to match the front bank, since the rear is not very linear compared to the front. The car is feeling better and better. I took care of the low 3k rpm range, its pretty much even now, still need some work at high 5k rpm but not alot.






Here is a comparo between the before n after, notice how much closer the afr are,
already took away more fuel on the rear bank at high 5k but havent relogged.

 

TUNED!!!
Both curves are basically almost identical now overlapping eachother. Now just have to fix the misfire (a separate issue) and the car is 100% tuned!

 

so how does it feel

 

I'm just curious as to why Nissan had it setup like that. To have one bank run leaner under 5300 and then have them switch. It doesn't make sense.

Anyone have links to the CVTC maps posted a while back?

 

that's cause Nissan didn't design the motor to run without the vias and boosted

 

Feels good, the turbo feels like it even spools better.

 

I am sure if the 3.5 came turbo it would have had a different manifold design.

 

I forgot to ask - what make/model of A/F did you install for this project? and what are you logging this on?

Oh - never mind - I see that you use the EU to record both A/F probes.

 

They are innovative lc1 widebands, $150each. Using the Logworks program it comes with.

 

I keep forgetting your not N/A. oops..

 

+1. It would be VERY interesting to see how a 00VI distributes air between the banks.

You know that now this is going to start a whole new level of fine-tuning. This information here is applicable to both FI and NA setups.

Awesome work streetz! One more for South Florida Maximas

Correct

That we cannot be sure of until we actually test that IM setup (stock IM with functional VI) to really see the distribution of air with that setup.

I think streetz is going to test this very thing next some day soon (to reinstall and make functional the stock VI mechanism).

 

this is very interesting, not sure how the timing components of a 3.0 vs a 3.5 will cause an impact on diff comp numbers btwn banks. the diff in compression can be causiing the diff in afr's i would think. it would really be interesting to see a 00vi dual wb02 readings. when i have my new y pipe made( some time in the future lol) ill have extra bungs welded on each leg to take readings as well. it being an na car i wonder if the diff would be as great.

 

The only way the 3.0 timing equipement would cause different readings is if the cam adapter spec's were not excatly the same

I am going to pull a reading from but banks with the dek and if it has the same problem
If JWT can not resolve it I am going move to the dark side and get a em, LOL

 

Yeah, I am going to put on the VIAS, will be logging AFR to see where it leans out in comparison to my current non-VIAS, that will tell me at what RPM it actually flows more (No need for dyno when u can know by afr leaning out. )

 

Nah, i dont think this has to do with 3.5, 3.0 timing components. Another local dude, did a comp test on his SER altima and rear showed higher as well, basically stock motor. was only 10psi higher, but def a difference, im sure with higher miles it multiplies.

 

Keeping the SW alive son!

 

The max may be long gone, but the SW is still mighty strong

Let us know when you figure out the misfire, how you did it, and when you dyno!

 

OK dumb question for you streetzlegend.

Where are you placing both widebands exactly?
For those that cannot afford two, could you basically do one at a time somehow to do final tweaks?
Can your XD16 gauge read both, or do you do two gauges? I don't think the DL-32 is required and you just use your emanage/laptop etc?

I will admit that I am mainly interested in doing this on my VQ30DE if you are able to answer my questions for both your engine and mine.

 

They go in place of the primary o2 sensors on the y-pipe (we have no emissions in FL so who cares for the CEL ). He's using Innovate's software (Logworks) to see both a/fs on the laptop.

You CAN use the same gauge for them, but you'd have to rig a switch to change the signal, it wont be a live-show both at the same time thing. For that you'd need 2 gauges

 

did u do another compression test yet

 

the sensors on where the stock front o2's below, I basically removed the car's o2 and put the wideband. Initiallly I was going to just use one, put it on one leg of the ypipe, go for a drive, then swap to the other leg, and log again, to compare. but it would be a little head ache having to switch n stuff. I only have one gauge, its not xd16, its a regular 40dolla gauge from innovative, I just picked one of the banks to use as the gauge output.
Yeah I just use a laptop to log/tune, i dont tune by looking at the gauge (not really recommended unless ur going for a real rough tough and dont have laptop at hand.)