carsnwomen91

Thats cause headers are much more work but it doesn't sound great with unequal y :'( Up to the op with his budget, goals and tech kills

op, as for the vi check at what rpm your 2nd gear comes in at at full throttle, then et the vafc2 100rpm under that rpm. imo it would make an auto dek real nice... Vias always open at wot

NmexMAX

iTrader: (22)

This is exactly what it is.

Re: the VIAS, rule of thumb back when was to dyno it with it completely open, and completely closed, and overlay them and use that as a guide as to when it was optimal to switch it over.

And for clarification, the DEK VIAS is just like the MEVI, just inverted, so there aren't actual longer and shorter runners, still uses the same dynamic supercharging principle.

The only VQ taht I know that has actual longer and shorter runners is the one found in the VQ40 Pathfinder, maybe even the Pathy 3.5's, either way, the DEK inverted MEVI is still superior to both the MEVI and the 02-08 VIAS.

2kMaxim

So i have 1/2 of the org saying ypipe will be big gains and sound good with the stock muffler...then others saying it wont sound good and not worth it if no full headers...hrm.

Grand_hustle17

iTrader: (22)

I have headers with test pipe and stoc catback n muffler.... don't do it, rasp city... I at wait to change mines now lol... again, screw the Ypipe, grab a OBX header system and take the better gains better sound... straight pipes are overrated n ricey in most cases... more noise and little to no additional power gain... unless u are getting rid of oem cat

2kMaxim

Right now i have the v8 grumble off the line. Ive read y pipe makes this go away (frown). If i get the ypipe basically everything will be straight except the stock muffler putting a cork on the drone. So theres no chance of y pipe making it sound even meaner? Im not getting headers, so its ypipe...or skip to safc or vafc and see what i can gain from that big tuning.

Rods03Max619

iTrader: (5)

Do you still have the Pre-cats in place, if so I think it will mess up your AFR readings if you do get a SAFC2 and try and Tune it, pretty much OBX headers, and SAFC2=Win...

2kMaxim

Pre cats wont mess up my readings..lol As you can see from my dyno the readings are loud n clear. Im running rich!

Grand_hustle17

iTrader: (22)

V8 rumble?... Aint never heard a max pull that off before... Id love to hear it.......

Im sure a equal length cattman y can help sound... But for the same price as a obx header... Mmmmm lol...

My afr dips to 10.7 lol, if only my finances was as rich lmmfao

NmexMAX

iTrader: (22)

Maybe for the DEK, but I gained some hp with a test pipe on my 03.

And for rasp control, use what I did as a resonator.

Unless you have comparative data like I do, I wouldn't be so sure, as you can see with my AFR's before and after cat-delete, even pre-cat.

dwapenyi

iTrader: (3)

If I was in your shoes I would consider getting rid of the test pipe, put back the cat, and add the Y pipe.

Once you do that, you would get gains and sound would still be good.

AND you can safc or vafc later and still get even more gains.

Your OEM Y pipe is really holding you back.

Interesting graphs.....its like the ECU can't account for the lower back pressure of the test pipe, like it assumes a certain amount from the cat.

NmexMAX

iTrader: (22)

I don't think our ECU's are that smart.

I think the cat itself affects the reading, as in if I had a WB before the cat, and after the cat, the graphs would look the way they do in that graph.


Also, irrelevant or not, it's a good topic for discussion this is my dyno comparing a test pipe and removal of the Helmholtz as the only "mods".

2kMaxim

Are you supercharged or something? What the deuce...lol. Can that even still be considered relevant? FI is a whole 'nother ballgame.

Worst case scenario I can get a Ypipe.....put it on....with the stock muffler it might be a tiny bit raspy but itll be muffled well. If its really heinous, Ill get a cat and throw in on there instead of the test pipe.

NmexMAX

iTrader: (22)

That's why I said relevant or not, it's a VQ35, hence the relevance statement. I myself have hated on test pipes, and VQ30's with headers, but in the past few years, I've come around and have become a solid believer in both for the VQ30 and 35.

2kMaxim

Is that an NA one? Stout...

NmexMAX

iTrader: (22)

Fairly normal for today's bolt on VQ35's, but the point is that the testpipe does yield results.

2kMaxim

Oh I'm quite sure it does...I think its probably evident from my dyno as well. Which is why if I can bear it sound wise.....ypipe added and leaving the rest of my setup the way it is should give me a significant nudge in HP. Honestly my car sounds bone stock on the highway. It does not sound bone stock at cold idle...or in the lower rpms. Its very gurgly....i love it personally. WOT its also obvious ive got something going on. So if the ypipe only gives it a slight raise in overall noise it should not be a big deal at all. If its INSANE and changes the whole thing...thats another story

On a side note I think people have been getting something confused. Obviously headers are superior for most power gains, but some people have been saying the unequal ypipe will sound rice. According to the small amount of research Ive done on some other car types, the "unequal" Ypipes should actually cancel out a little rasp. Especially in the case of the cali one that retains 1 precat. The two banks firing will be a little separated noise wise so I think they would likely produce less DRONE characteristics. Ive read its more likely that equal headers in a straight through exhaust will be the droney candidate.

NmexMAX

iTrader: (22)

Never had any drone with my 03 with straight pipe and headers and stock catback. Same with my VQ30 with Stillen 1st gen and aftermarket chambered muffler. But when I went with the WSP Y for my VQ30, sounded like a tractor with an awful drone.

2kMaxim

Lol...well that's certainly not what I want. I think for now given that my car has a lot of miles and I don't want to mess with emissions (more than putting a cat back on once a year) I'll buy a used SAFC or VAFC and see what the numbers are once its tuned. Im already happy with it as is...and with another few horses, Im guessing mid 180's whp and breaking the 200wtrq mark I might be a-ok with it. Spend the ypipe money on a RSB Maybe a grounding kit for the tranny....

dwapenyi

iTrader: (3)

When you did your research, did you take note of which brands had a tendency to be raspy? Stillen, Warpspeed, Cattamn?

carsnwomen91

^^ doesn't matter unequal with tp sound bleh.

put The cat back on and get a y. Or get the y with a high flow cat (warpspeed sells as a package). It wont be raspy since you'd have a cat and a resonated cat back. Take a look and listen to my video in the other thread you made... It doesnt sound raspy but still prefer a sound with equal y. Plus It would sound better on yours up top since you have an 00vi stock.

NmexMAX

iTrader: (22)

As with any other car, mods typically add peak hp vs torque. Since I began modding my Maxima, I've only added about 30ft/lbs peak, but added almost 50 hp peak. And tehre comes a point where torque nearly stays the same.

My last comparison, I gained 10hp, and less than 3 ft/lbs, peak. Even though that was the only peak, I gained nearly 20ft pounds in a different part of the range.

Not to mention, I've added a whole lotta area under there not including peak.

dwapenyi

iTrader: (3)

And that's whats it allllll about right there

2kMaxim

Mine seems to be opposite. Im wondering if its because i still have the precats in. Looks like ive gained 20+ torque over stock....

I dont have a resonated cat back....i have mandel bent mid pipes and test pipe.

NmexMAX

iTrader: (22)

That torque thing will change, it's just the nature of the game. I used to make more torque than hp, then, the number slowly and proportionally proportionally reversed itself.
My dynos in order.

211/218
233/230
242/238
247/243
257/245

2kMaxim

Wonder what the safc will do. Its on deck. Got a good quote from my shop....for install/tune. Now I need a good used one.

NmexMAX

iTrader: (22)

This is what mine does consistently, as this is only one of my sessions.

Best & worst:



All runs of that session:

dwapenyi

iTrader: (3)

I think you also need a wideband O2 sensor.

NmexMAX

iTrader: (22)

If it's a shop with a dyno, I'd assume they have one.

Back when, a lot of people would just go to the dyno and tune using the shops WB.

More recently, seems as if people are going with larger MAF's, so common sense says to get an on board wb to monitor.

In the OP's case, I'd say it's not necessary. It would only give him the opportunity to street tune so it's closer to being "dialed in" and might mean less runs/time/$$$ on the dyno. A WB is just another expense, and if he's going to spend the minimum of 200+$, then, I'd say that's better spent towards headers.

Also, like the domino effect, if he does decide to get a WB, might as well look into larger MAF's, etc.

2kMaxim

Lol. Im almost fully decided on my plan. I just spent a couple hours at my new favorite exhaust shop getting the previous lazy exhaust shops work redone. This guy basically customized my b pipe hangers, and made a custom section of exhaust pipe so my stock muffler mates perfectly and sits nicely tucked up under the bumper like it should. Before, the other shop just slapped on a connector and some welds and it was pointed down in the back like a donkey ****. Bothered the heck outta me. Did all this new stuff for $85. Also the guy who runs the place said as long as my computer passes the emissions test he will turn a blind eye to the test pipe. So this means I dont have to touch squat! So my plan is to leave everything the way it is and tune with safc. If my Ypipe/bank 1 precat goes eventually and throws a code..only THEN will I worry about replacing with warpspeed or new stock one from Walker or whatever. Im happy though because my car soundwise is one of the better more stealthy setups ive heard of any on youtube. One day I will post some clips

BTW: It looks like your tune is very conservative near the top....I get why the tuner does it that way but it seems like you could be closer to 14:1 and get a few more ponies.

MoncefA33

iTrader: (6)

Aggressive AFR isn't necessarily good for power. One guy on here has tuned his car @ 12:1, 13:1, and 14:1 and the power gains were basically zero.

My experience with tuning VQs leads me to think they like more fuel, my DEK made most power @ 12.6-12.8 AFR. My VQ35 will probably do the same.

2kMaxim

Well that would actually be the best of both worlds.....then you have a nice super safe a/r and still get some power....

Grand_hustle17

iTrader: (22)

yup

NmexMAX

iTrader: (22)

I am the "tuner", which means I look at the AFR graph and adjust the SAFCII after. Check my threads for +/- on the SAFC and other analyses such as power:AFR ratio, etc.

My best power wasn't the leanest, though I went quite lean to see if it made a difference it didn't, lost 2whp. Also, I've seen a VQ30 tuned at 13.8 put down a LOT of power, but my VQ35 doesn't like it that lean, I've seen on 2 occasions lost power after 13.5.

My car doesn't like mid or high 12's, it likes 13,0-13.5. They're all different, see what best first yours.

I've tried the high RPM lean, didn't seem to like it.




This AFR resulted in this hp curve:

2kMaxim

Do you think its more likely my DE-K will like it around 13.8ish?

Rods03Max619

iTrader: (5)

Let the guy who is going to Tune your car figure that out, since it may and it may not...

MoncefA33

iTrader: (6)

You should PM me about that VQ30 @13.8 I wanna see it.

Your car's AFR preferences could be due to the fact your SAFC is adding timing as you lean it out, so what you're seeing is a balance between AFR and indirect timing advance creating a best power situation.

2kmaxim if you use an AFC I would start at 13.0 and go from there.

carsnwomen91

Its weird how lean you can go without knockin under load on the 3.0, I'm set to 13.5 5-6.5k rpm but 2.5-3k needs to be 12.5 or else I get a hint of knock.


op I thoughy you had an srs cat back... Either way good news about your exhaust mechanic :-D now u can enjoy a y pipe guilt free

2kMaxim

I wonder if I have to worry about my 2 degree timing advance now. Or maybe it will just work itself out in the air/fuel tune. SAFC's usually have a knock sensor that gets hooked up, so I guess my tuner can just stop adjusting if there starts to be knock.

MoncefA33

iTrader: (6)

SAFC will not read the VQ30 knock sensor, and no you do not need to worry about knock when you add 2 degrees of timing with an AFR in the 13s.

2kMaxim

Well I have a flat 2 degree advance already...im saying if the SAFC as a biproduct bumps it up 3 more etc...lol