So, long story---I have been doing general maintenance on the car to get the MPG up and have been fairly happy at a combined of 24 (60% highway/40% street) but as I just turned 70K I decided to replace the O2 sensors. The last one, drivers side after cat just would not come out. PB blaster and a long breaker bar got it out, along with the boss on the Y pipe. Doh!

So I pulled the stock Y out and tack welded the boss back on. I went ahead and grabbed a generic Y pipe off of Ebay to mess with (2 1/2" in, 3" out) and noticed just how close it is to the stock pipe. Got some 2 1/2" polished stainless pipe (Amazon RULES), some O2 standoff pipes, and flanges. Got most of the welding done today (use TIG for stainless) and I hope to finish, as long as it does not rain, tomorrow. The stock pipe necks down to 1 1/2" right after the cat and then in other places as well. Really weird design but I assume for noise abatement.

For anyone that wants to attempt this: the flanges off of the primary cats (on the exhaust manifolds) are weird, 2 3/8" opening with center to center bolt spacing of 4 5/8". I found some that will work but not in stainless on Amazon. Finally found some stainless at a custom exhaust shop.

Don't know how much louder it will be but I really don't care at this point as I am going for better flow and can deal with noise reduction later on (running Megan mid pipe back right now).

Should be fun and I'll keep you guys informed. I should be into it for about $350. Could have been done cheaper at an exhaust shop probably but I wanted stainless and secondary cat delete for when the car sees the track. Most shops will not touch anything with cats in California and besides, I like to do everything myself. I've already got replacement cats that will bolt in (similar to the M35) for street use (just need to weld the up pipe and O2 flanges on).

What up Dean!! So no cats..? is that right?? Damn, that car is going to FLOW!!! I'd love to hear the exhaust, too....it will sound like a beast

BTW, are you in Woodland Hills?? If so, you should stop by Fast Intentions and talk to Tony about any exhaust questions...he's knowledgeable...I was gonna have a full custom set up done by him, but it's hard for me to find time and make the trip up there from Long Beach....

But it sounds like you got the skills to weld, so you are saving a boat load of $$$...

keep us posted

thanks man,
Anthony....

hows emissions in california?? and does a check engine light come on? if it doesnt im def gonna do this ASAP!!!!! lol

Combined 24! im at 16.x combined and once I qualify for my paid BMW I'm probably going to jump on the E92 M3. So for a few more months I'm still interested in improving my MPG. What have you done to hit 24mpg?

CPJ LB wrote:What up Dean!! So no cats..? is that right?? Damn, that car is going to FLOW!!! I'd love to hear the exhaust, too....it will sound like a beast

BTW, are you in Woodland Hills?? If so, you should stop by Fast Intentions and talk to Tony about any exhaust questions...he's knowledgeable...I was gonna have a full custom set up done by him, but it's hard for me to find time and make the trip up there from Long Beach....

But it sounds like you got the skills to weld, so you are saving a boat load of $$$...

keep us posted

thanks man,
Anthony....

Hey Anthony, yep, the "option" of no secondary cats. I know Fast Intentions---haven't met Tony personally though. Will have to check them out. Primary cats (on the manifolds) will still be there regardless. To be honest, the stock cats (4 on the M45) probably do not flow that bad. 2 1/2" in and out but the Y pipe, all the changes in diameter especially on the bends, have to significantly reduce upper RPM flow. If you come up to the valley let me know and we'll hook up. I may have to go down to Irvine in the next two weeks--I'll let you know.

hows emissions in california?? and does a check engine light come on? if it doesnt im def gonna do this ASAP!!!!! lol

Cal is rough on emissions. There should not be a check engine light because the O2 sensors are before the main cat and after the main cat. There is no O2 sensor after the secondary cat (in the Y pipe)

Combined 24! im at 16.x combined and once I qualify for my paid BMW I'm probably going to jump on the E92 M3. So for a few more months I'm still interested in improving my MPG. What have you done to hit 24mpg?

All the usual maintenance, tires at 35psi static, irridium plugs (one range cooler), 0W30 mobile 1, throttle body coolant bypass, CAI, car is lowered, all under panels are in place, made sure all the body gaps were uniform and weatherstripping in place--pretty much anything to reduce drag. If I don't hop on the freeway and just poke around town it falls to 19~20mpg. Pretty much anything you can do to limit the throttle angle needed to maintain speed helps. The further you press on the accel pedal the lower ignition advance you get. I can cruise on flat land at 75 just barely touching the throttle and the computer shows 38~39mpg.

I got my custom made y-pipe done a few weeks ago on my M45:

http://www.iscenem.com/forum/threads/55 ... king-power

Any pics of the final product and how's the sound?
You went the better route, probably. Keeping the stock cats would have made my life a lot easier.

The next thing we need to do is get some headers done but the space is REALLY tight in the M.

custom y-pipe while still running the oem cats sounds a bit louder but it's a low sound (hot a high pitch). Sorry at this time I have no pics of the new y-pipe.

only sound clip I have for now:

http://www.youtube.com/watch?v=KcwZbidpXzI

The good thing about keeping the oem cats is passing state inspection, no rasp, no bad smell & no lights on the dash (cel).

Looking at the y-pipe you have and removing the oem cats all you need is to make 2 test pipes which will fill the missing space that you'll have.

DeanM45 wrote:The next thing we need to do is get some headers done but the space is REALLY tight in the M.

+1

Group buy anyone?

Also if you get an uprev reflash/tune you can turn off the CEL from deleting the rear cats, its very common with 350z/G35's and titans

06M4.5 wrote:custom y-pipe while still running the oem cats sounds a bit louder but it's a low sound (hot a high pitch). Sorry at this time I have no pics of the new y-pipe.

only sound clip I have for now:

http://www.youtube.com/watch?v=KcwZbidpXzI

The good thing about keeping the oem cats is no rasp, no bad smell & no lights on the dash (cel).

Looking at the y-pipe you have and removing the oem cats all you need is to make 2 test pipes which will fill the missing space that you'll have.

Sounds good. There will not be a CEL with the rear cat delete -- the ECU does not know if they are there or not. The 35 folks delete their primary cats which is the reason for the CEL and the bad smell. This should not occur on the M45 because the primary cats are still in place.

Correct on the test pipes. I'm going to finish welding them up at lunch.

you'll still get that nasty smell by removing the rear cats, even more if removing the primary cats on the M45

and keep in mind that the M45 needs to have some kind of back pressure in order not to lose it's lower end torq. unlike the 350z or G35's that can run straight pipes from the headers back and still produce around 300hp to the rear wheels (have you smelled one lately??).

06M4.5 wrote:you'll still get that nasty smell by removing the rear cats, even more if removing the primary cats on the M45

and keep in mind that the M45 needs to have some kind of back pressure in order not to lose it's lower end torq. unlike the 350z or G35's that can run straight pipes from the headers back and still produce around 300hp to the rear wheels (have you smelled one lately??).

As long as you keep the primaries in place the rasp/smell shouldn't be bad at all, and there will still be plenty of back pressure. You will definitely need a tune to take advantage of it all though.

The only 350z that can get close to 300 at the wheels are the newer ones with the HR motor, no VQ35DE is getting there on a reasonable dyno.

My last car was a 570whp built TT G35, I know a bit about these things

correct, 350z V6 HR motors

DeanM45 wrote: There will not be a CEL with the rear cat delete -- the ECU does not know if they are there or not. The 35 folks delete their primary cats which is the reason for the CEL and the bad smell. This should not occur on the M45 because the primary cats are still in place.

Deleting the rear cats influences how the primary cats function, and can throw a check engine light. Remove that extra bottleneck and the exhaust is going to flow better and faster through the primaries, which the sensor can detect as an abnormality and throw the code. The CEL doesn't mean that its not running right, just that the sensor detected something outside of its preprogrammed parameters. I've seen it many times on titans with modified B-pipes.

06M4.5 wrote:correct, 350z V6 HR motors

The vast majority of them, and EVERY G35 coupe ever built have the DE.

seymore4 wrote:

DeanM45 wrote: There will not be a CEL with the rear cat delete -- the ECU does not know if they are there or not. The 35 folks delete their primary cats which is the reason for the CEL and the bad smell. This should not occur on the M45 because the primary cats are still in place.

Deleting the rear cats influences how the primary cats function, and can throw a check engine light. Remove that extra bottleneck and the exhaust is going to flow better and faster through the primaries, which the sensor can detect as an abnormality and throw the code. The CEL doesn't mean that its not running right, just that the sensor detected something outside of its preprogrammed parameters. I've seen it many times on titans with modified B-pipes.

Yep, experienced that on the Lexus as well hence the reason for the "standoff" O2 bung on the test pipe. We'll see if it throws a code in a few hours.

UpRev or Motec is in the near future. I just "won" a spare harness should I decide to go Motec but UpRev looks much more appealing in my old age, LOL.

whats funny to me is that on the same dyno a HR V6 can produce more power than the M45 V8

maybe if someone would convert to a 6-speed man. trans on a M45 will we ever see 300hp to the rear wheels

DeanM45 wrote: UpRev or Motec is in the near future. I just "won" a spare harness should I decide to go Motec but UpRev looks much more appealing in my old age, LOL.

Absolutely no reason to go with a motec unless you're making a full out race car... Uprev is more than capable of handling everything you need it to and more. Plus with the motec you'll lose a lot of the functionality/ safeguards of the factory ECU, one of the reasons its the best tuning option for (most) 03+ nissan's % infiniti's

Shoot me a PM if you have any specific questions about it

06M4.5 wrote:whats funny to me is that on the same dyno a HR V6 can produce more power than the M45 V8
maybe if someone would convert to a 6-speed man. trans on a M45 will we ever see 300hp to the rear wheels

Its not all about maximum HP... our V8's produce waaaay more TQ than they do, and that's what scoots you back in the seat. HP is just an extrapolation of TQ at a certain RPM, and a number on a piece of paper. We win the TQ game hands down. But you can rev an HR out to 7800 all day long, so it will make more HP.

seymore4 wrote:

DeanM45 wrote: UpRev or Motec is in the near future. I just "won" a spare harness should I decide to go Motec but UpRev looks much more appealing in my old age, LOL.

Absolutely no reason to go with a motec unless you're making a full out race car... Uprev is more than capable of handling everything you need it to and more. Plus with the motec you'll lose a lot of the functionality/ safeguards of the factory ECU, one of the reasons its the best tuning option for (most) 03+ nissan's % infiniti's

Shoot me a PM if you have any specific questions about it

Yeah, I would only do it to learn about Nissan ECUs. Started with an Accel DFI system on my GN back in the day and have played with Motec, AEM and Haltech on the Supras and Lexus cars.

Took the car on about a 40 mile drive. No CEL. It is really not much louder at all and no drone on the freeway.
Throttle response it MUCH better and it climbs the RPM range much faster now. Started raining so I couldn't get on it too much (traction control keeps kicking in) and just spins the tires if I turn TC off. Soon as it dries out I'm gonna throw the old Gtech in and see what kind of difference there is.

Hey Dean,

Great job on your exhaust! I would love to check it out for myself, I live in Orange and work in Anaheim (Off Katella Ave. on the 5 fwy.) I've been looking into getting a custom exhaust so I can take it to get upreved. Let me know if I can check out your work if you're around where I am.

Thanks,

CL

Yeah, all of us SoCal people are going to have to get together at some point. I rarely see a M in the valley up to Santa Barbara.

Little update, I had to run up to Santa Barbara today and the car averaged an additional 2 MPG than normal. I have driven about 90% highway/20% city since finishing the pipe and the display is showing a flat 30mpg. That's only for 300 miles though (still have just over 1/4 tank) but pretty jazzed about that. The car does run LEAN when cruising, right around 14.5:1. At WOT it has dropped from (stock pipe) 13.2:1 to 14:1 so it IS moving quite a bit more air. I doubt the stock maps can be altered enough by the stock system to compensate so UpRev is soon down the road. I will have to pull the test pipes off again as the exhaust sits too low, about 1" lower than stock and is scraping. I attribute that to not paying attention when I was laying on the concrete tack welding the flanges on!

I'll probably do that next weekend as I just got my Transgo kit from Summit (only $230 right now) and will have the car up on stands for that anyway.

No noise increase, no weird sounds other than the notorious 2.5K - 3.5K rock rattle sound is GONE which confirms once again that the stock Y pipe has a piss poor design.

This is getting fun now.

DeanM45 wrote: I'll probably do that next weekend as I just got my Transgo kit from Summit (only $230 right now) and will have the car up on stands for that anyway.

I just ordered one today from summit too!

Yeah, it's a good deal and fairly easy. If you can change the trans fluid you can do the shift kit.

Seymore4, you'll probably know....can UpRev increase line pressure in the trans? I'd like to get a bit more when on the performance map. If not I'll probably throw in a thin washer on top of the main regulator piston.

DeanM45 wrote:can UpRev increase line pressure in the trans? I'd like to get a bit more when on the performance map. If not I'll probably throw in a thin washer on top of the main regulator piston.

yes you can. Titan guys call it the "line pressure mod". There's also a good deal of responsiveness to be gained by fixing the electronic throttle, it never even opens 100% in stock form.

Not to mention the fuel delivery... smh

Then there's the cool feature of map switching using the cruise control buttons and being able to have rev and speed limited valet and anti theft maps

Pulled off the cat replacement pipes today to shorten them up a bit to raise the exhaust (was scraping more than I liked). Everything is tucked up tight now. I didn't think to take pictures when I had it out, just wanted to get it done, but here are the pictures installed. Draining the trans right now to install the Transgo Shift Kit.

This is where the O2 sensor goes. Mounted with a standoff to prevent a CEL:





You can see here on the expansion joint where it was scraping a bit:


Yeah, I know they are dirty but I'll clean them up after I get done with the trans.

And thanks to Seymore4 UPREV has begun!

DeanM45 wrote:And thanks to Seymore4 UPREV has begun!

You're going to like it, I only played around with mine for about 15 minutes and it really woke up.

That electronic throttle control really sucks on the stock tune! Not to mention the AFR's

So when will you post up a sound clip?

mexillis wrote:So when will you post up a sound clip?

Soon.

Raining here right now and I just finished up the Transgo shift kit yesterday afternoon. It's messy and slippery out there, especially on the high throttle shifts.




Straight forward and easy but messy and USE A DRILL PRESS when drilling out the separator plate.

Once it dries out a bit and I put in the new UpRev map I'll take some sound clips. Again, it really sounds a lot like the stock Y with Megan exhaust. A little bit more rumble at idle but otherwise no increase in sound, just performance.

That looks