This thread is in response to a request from Y2KSE.

As many of you already know, I am in the process of partly changing my car from CA emissions to Federal emissions. I am NOT doing a complete conversion, but just enough to get by and also get the increase in HP.

Here's a summary. I am changing the front-side (aka left-side) exhaust manifold from the CA spec to Fed spec. This will allow me to bolt up a Fed spec y-pipe to both manifolds (the rear one is the same on CA and Fed models). I have already relocated the two downstream O2 sensors to after the main cat (similar to the one downstream sensor on the Fed model). You can see pics and descriptions on my web-site of this mod. I will finish the project and post an update here, as soon as I can get a Fed y-pipe (anyone want to make a donation of $400 to the Phil Barnhart Y-Pipe Foundation???)

You can reach this site directly by clicking on the following link:

www.desertpearlmax.homestead.com/O2_Sensor.html

 

VERY NICE!!!

 

How much power do you expect to gain from doing this?

 

I don't know, but the less restrictions the better so that's good for us.

 

What if the increase comes out to 2 HP? Seems like much work not knowing what's at the end of the rainbow. Of course, I can ask questions such as these because I have a Fed spec.

 

If you look at this mod in two parts we can figure it out. First is the standard y-pipe, which people have been saying gives around 10-20hp depending on other mods and whether you install the whole y-pipe (ie both pieces versus one piece in the case of the Stillen pipe).

Then I am also hoping to recover the decrease in output found in the CA emissions models. This is more of a low end response (ie peak torque) benefit and doesn't yield an increase in peak HP. You can see the dyno plots posted by MadMax2k at:

http://homestead.juno.com/madmax2k/f...ynooct2000.jpg

They clearly show the CA emissions losing about 10ft-lbs of torque up until about 5k rpm when compared with the Fed emissions cars.

So, basically I'm hoping to gain around 15hp in peak HP and about 15-20 ft-lbs in peak torque. I think I'd actually wet my pants if it turned out this good though!

 

Right, but that is with a y-pipe. Are you planning on breaking even with a direct conversion? I'm just curious. Since you have your manifold off, why don't you whip some headers real quick.

 

The dyno plots above will show what I'm hoping to gain from just the manifold swap/front precat removal.

As far as the headers go, I'm already having a hard time scrounging up enough $$$ for the y-pipe, much less custom headers!!! My wife and new baby have put a severe restriction on the Car Modding Fund.

 

I don't remember the exact numbers, but 4th gens with y pipes put out more to the wheels than 5th gens with y pipes (I'm talking about Cali spec).

 

Don't forget WITH the CALI-FED conversion the exhaust pressure will be balanced, which is another PLUS. The other option is to leave one precat which "could" lead to long term problems.

This should also be faster than waiting for Cattman to redesign their CALI spec Y-pipes to eliminate BOTH precats.



Paul, please keep me posted on part #'s and TOTAL parts cost. Maybe, you could borrow Zachs FED Y-pipe to make sure everything works before you invest in a FED spec Y, which may not work. A lot of work, but may be worth it. Can't wait to see the difference at the track. Let me know when and where.

 

That's an excellent suggestion, IceY2K1. As Desert Pearl indicates on his web site, he hasn't actually been able to replace the CA exhaust manifold with the Federal exhaust manifold yet because the Federal manifold won't bolt up to the CA pre-cat. So we still don't know how the ECM will behave once the front pre-cat has been eliminated.

 

I agree too. This has really been the only potential problem with this mod. Simply moving the O2 sensors shouldn't have caused any problems especially with the precats still installed. The real question is what will happen when the precats are removed (ie will the main cat be able to satisfy the CA ECU?). Hopefully the answer to this question is YES and everyone lives happily-ever-after.

 

Where can you find the exahust manifold and how much is it? Thanks...

 

That would indeed be a wonderful result, Desert Pearl. But don't be disappointed if the outcome turns out to be NO instead. Consider it logically. The function of the aft front O2 sensor (the one you moved) is to measure the amount of emissions reduction that occurs across the front pre-cat when the engine is cold and before the main cat fires up. Theoretically, moving that sensor behind the main cat won't help because the main cat doesn't fire up right away. So given that the odds are definitely not in your favor, keeping your outlay to a minimum would be a very wise thing to do.

BTW, here's a wild and crazy idea in case your experiment fails to produce the desired results. Remove the aft front O2 sensor from behind the main cat, plug the hole, and just let the sensor dangle in the open air. If the function of that sensor is to measure the reduction in emissions when the engine is cold, it may be satisfied to find no emissions at all.

 

I would definitely try this before scrapping the whole project, but if the downstream O2 sensors work like the first set of O2 sensors, this won't work because they expect to see varying voltage around some nominal setting. I am checking our finances right now. Maybe I can go talk to Cattman sometime soon.

 

Talk to Cattman Paul or call him. I have his home phone number incase you can't get a response. Last time I met with him, he wanted a Cali spec 5th gen to use for a prototype Y-pipe that would eliminate BOTH precats.

He said you would get the Y-pipe, it installed, and if you want a few free dyno runs to produce numbers for advertising. All this for just the cost of materials(~$200-250) and probably 3-trips to the shop for a few hours of work.

 

question

why not just wait for headers, cattman is developing right?

 

I talked to him about 4 wks. ago and he didn't say anything about working on headers. Those would be nice, but PRICEY.

 

This is exactly why I'm not jacking with the first two O2 sensors. Those are the only ones that are used to tell the ECU whether the car is running rich or lean. I believe your last statement is true regarding the downstream O2 sensors only looking for a difference between their readings and the first O2 sensors. The only question I have is whether my main cat will provide enough of a difference when the car is cold to keep the check engine light from going on.

It would be nice if Cattman can offer a solution to our CA emissions delima, but I think I will see my project through to completion. I am planning on ordering a Stillen 2-piece y-pipe tomorrow.

 

Normally I'd recommend the Cattman Y-pipe over the Stillen, but in your case the Stillen Y-pipe is definitely the better alternative. Because of its 2-piece design, the Stillen Y-pipe will be functional regardless of the outcome of your experiment.

Good luck, and keep us posted.

 

Yes, please keep us posted on this.

 

how much more could it be than ordering a ypipe/exhaust manifold combo?? plus you get better flow if they actually do make the headers

 

I had the same thought. Even if my experiment doesn't turn out, I can still use the main piece of the Stillen y-pipe and do an install like Y2KevSE. I ordered it today. Stillen said I should get it by next Tuesday!

My wife is going out of town next Thursday, so I'm hoping to do the install then. The only problem is if I do that, I won't be able to get pre dyno numbers... only post numbers. I could just install the underdrive pulley on Thursday and dyno it then, before doing the y-pipe/manifold install and then just post y-pipe numbers whenever I can get back to the dyno shop. What do you guys think? I am anxious to complete the project because we've been talking about it for soooo long, but I would really like to quantify the results as best as I can since I'm the first to do this mod.


Pmp-n8a, I got my manifold used for $50 delivered to my door. The Stillen y-pipe was $360 delivered. I bet you can't get a custom header/y-pipe combo for even twice that amount!

 

whoa...50?...i thought it would be a bit more than that....actually try alot more..

 

Speaking selfishly, I'd like you to do the install at your first available opportunity. (Now for a little peer pressure.) I mean, when's the next time your wife's going out of town? You don't really want to make us hang on THAT long, do you? (How am I doing guys? )

 

She will be out of town from Thursday until the following Tuesday. I am taking off of work on Thursday to take her to the airport and head back home to do some work on the car and take it to the dyno shop. I am thinking, maybe I just do the pulley then and get pre dyno numbers. Then I will have all weekend free to work on the y-pipe/manifold install, not that I expect it to take that long, but you never know. So, either way, I will have the install done by early week-after-next.

Have any of you guys ever removed your front exhaust manifold for any reason? It looks pretty tight. I am thinking about removing my radiator (very easy) to get some more space. I believe I can remove the manifold/front precat unit from the top side if I have the radiator out.

 

hey des...how much are you looking at for this installation??

 

Keep one thing in mind, Desert Pearl. You may end up generating a Check Engine Light if your experiment fails. You may also put your ECM into limp mode. In either event, you'll need to have enough time to reinstall all your stock exhaust equipment, relocate your O2 sensors to their original positions, and get your car into your dealer to flush the error code. How long will that take? And how will you explain it to your wife?

(PS: Hope I didn't rain on your parade, Desert Pearl. )

 

http://forums.maxima.org/showthread.php?threadid=33942

If it's true, it may be possible to simply gut the front pre-cat, relocate the O2 sensors as Desert Pearl has done, and continue to use the stock CA front exhaust manifold.

Just a thought.

 

Free. I'm doing it in my garage. Doesn't look too hard. I'd much rather be removing the front exhaust manifold than the rear one!!! The rest of the install is easy.



Everyone's a critic!

I am remaining pretty optimistic on this mod... I think it'll work as I planned. Also, I doubt the ECU will go into limp mode for emissions related items, such as secondary O2 sensor readings.

 

I thought about gutting my front pre-cat. A local muffler shop said they could cut a hole in the pre-cat remove the contents and then weld the hole closed for $140. Is this the only way? It's better to make sure this entire experiment works because a new pre-cat is $500!

 

The material inside a cat is pretty brittle. I have used a hammer and a long 1/2" drive extension to knock out the material before. With the wide snout we have on one side of the front precat, the "honeycomb" material should come out rather easily.

BTW, if you ever need parts for your car, check out car-parts.com. They are a search engine for used auto parts places (ie scrap yards). That's where I got my Fed spec exh manifold for $37.50 + shipping. Dealerships wanted $150 or so for a new one.

 

We're all waiting for you, Desert Pearl. I, for one, appreciate you being the guinea pig. BTW, dyno results before and after this specific mod would be great! Besides the balance of exhaust flow issue, power results would be nice to know.

 

I should be able to do that. I got my underdrive pulley installed today. So, the plan is...

1. Receive Stillen y-pipe on Tuesday.
2. Leave work early on Tuesday to dyno the car before installing the y-pipe/manifold (providing Pro Dyno can fit me in then).
3. Take wife to airport Thursday morning.
4. Install y-pipe & manifold by Thursday early afternoon (taking vacation from work).
5. Take car to Pro Dyno Thursday late afternoon to get post numbers (once again, providing they can fit me in).
6. Post results on Thursday night.
7. Go to Firebird Raceway Friday night to try it out at the strip.
8. Post more numbers late Friday night.

This sounds really busy... hopefully I can do it as planned. This schedule should be okay for Y2KSE too, because it leaves me free from Saturday to Tuesday night when the wife comes back into town). That should be plenty of time to get the check engine light, limp mode, return to stock, take to dealership stuff resolved as he predicts.

 

Believe me, Desert Pearl, I'd much prefer that the install, the results and your timing all work out perfectly. My sincere best wishes are with you. And if your experiment doesn't work out, you won't get any "I told you so's" from me!

 

Let me know on Friday if your going to make it to Firebird. I'll try and meet you there.

 

Just wanted to let you know that I wasn't trying to be a smart-a$$. It's just that it seems as though you were always the one to bring me back down to reality on this issue. I do realize that everyone on this board is wishing me luck, because many of us will potentially gain from my experiment... although looking back on it now, it has been a lot of extra work probably for only a few extra HP. At least I enjoy working on my Max.

 

That's all that really matters I guess....Regardless if you gain a lot of power or not, you have learned a lot about your Max and enjoy working on it Plus, provided us all with a lot of good info.....

 

Thank you, UMD_MaxSE. I couldn't have said it better myself!

 

Hey Desert Pearl. I noticed on your website that the federal front exhaust manifold does not have an O2 sensor nut. Our present O2 sensor before the pre-cat is in our present manifold. Where are you going to put this sensor once you do the swap? Are you going to relocate this one also?