I just finished installing test pipes at Dyno-Comp in Scottsdale, AZ. First off, my impressions are...

1. Good power gains. Definitely noticable.
2. Slightly louder than stock, especially under full throttle.
3. Some raspiness between 3k-4k at half throttle or more.

Install was fairly straight forward. All you need is a 22mm wrench for the O2 sensor and a 14mm socket/wrench for the other bolts. I loosened the upper outside bolt (hardest one to access) from the engine compartment with some long extensions on my ratchet. The passenger side was easy... the drivers side required the removal of the intake tube going from the MAS to the throttle body. My G35 also had a cross member that bolted both cats to the tranny. This was removed from my car as well.

These test pipes were purchased from lsdunique. I got the mild steel version and would strongly recommend spending the extra $30 or so to get the stainless version. The coating on the mild steel ones would rub off with very little (i.e. no) pressure. The build quality of these pipes was very good. Nice 3/8" flanges, good welds, nice bends, etc.

Now onto the real results. First off, here are the dyno results from my G35 Coupe 6-spd. The pre dyno run is shown also.



So, the gains in peak HP and torque were:
HP gain: 3.4whp
TQ gain: 4.4lb-ft

with a maximum gain of:
HP: 6.5whp @ 3950rpm
TQ: 8.6lb-ft @ 3950rpm

As you can see, my car lost a little bit down low (below 2800rpm), which can be explained by exhaust velocity. This is also the reason I went with the smaller diameter pipes (2.25" I think) made by lsdunique. The larger pipes (like 2.5") would have made this dip more pronounced.

Here are some wav files for your listening pleasure.

Stock: http://www.desertpearlmax.homestead.com/files/stock.wav

Test Pipes: http://www.desertpearlmax.homestead....les/NoCats.wav

 

Thank you for getting those dynos to go with your mod. Very informative.

And a great part, it sounds like! Definately like the new sound.

 

Good post, always nice to see someone dyno a mod. Gains are lower than I expected, though. Some people have been estimating 15 rwhp. Very interesting.

 

Yeah, no way 15 rwhp, someones smoking some crack I got a little over 6rwhp gain also.

 

My dyno with Mines test pipes has that same dip in torque below 2800 rpm's and comes above the baseline at the same point......must be a characteristic of cat removal.

 

I believe the 15hp numbers came from a writeup in HyperRev with some Mines straight pipes. I don't believe this was done on a US spec Z. I am also uncertain what mods had been done prior to the Mines pipes.

The gains are definitely noticable to the Butt Dyno. It feels like more than a few HP increase. Even with the so-so results, you should still consider the following:

By popular opinion, the best "bang for the buck" upgrade for our car is the Crawford Plenum. This reportedly gives 9whp peak with a max of 20whp at redline for a cost of $500. This mod gave 3.4whp peak with a max of 6.5whp for only $185. So, it gave about 1/3 the gain, but at only 1/3 of the cost. Sounds like the Crawford might have some competition for the best "bang for the buck" title.

 

I believe that with the installation of test pipes, the total cross-sectional area is increasing, thereby decreasing the velocity of the exhaust gasses. The directly effects the torque curve due to scavenging effects. By reducing the velocity, you are reducing the lowend torque and theoretically moving up the rpm of your peak torque. This is why the optimum pipe diameter is soooo important when designing headers.

Did you measure your Mines pipes during install? ZRed makes some that are 2.5". I suspect the low end with those would suffer even more than with the 2.25" pipes. Maybe someone can comment more on this...

 

Well, 6 rwhp doesn't make them that much better than the Random or Crawford high flow cats. And those ARE legal, lol.

 

Were these installed w/ stock exhaust?

 

Yes, these were done with the stock exhaust. My only mods thusfar are a K&N drop-in and Happies713 grounding kit.

I agree with you little_rod. These aren't giving any more than the Crawford or Random cats. The only differences are that those are street legal and they cost twice as much. Someone on this board made a comment on an earlier post (sorry I can't remember who) and I thought it was relevant here. His quote was something like ... "as soon as the government starts cracking down on busses and semis, then I'll start worrying about my cars emissions."

 

One thing people have to understand about Dyno's and VQ35 is that the #'s of the dyno never gonna reflect what your really putting on the wheels... for example w the Cat pipes the
avg. whp is 8-10 but when you race w another Z with cats you gonna see yourself 2 or more cars ahead... this is because the air that is sucking the filter on the dyno never gonna be the same that suck in the street,(when you go over 60 mph the air filter is getting it big time!) so if you have more air going in the engine(street) but w less restrictive way to go out you gonna see better results than on the dyno(special on top end speeds)... this is not a theory, this is a fact that I lived since I star modifying my Z. get my point?

 

Webcar: That is why 1/4 time slips are also good to see after a mod. Cheers!

 

I think these pipes complement an aftermarket exhaust better. I beleve the stock Y-pipe is the real bottleneck.

I'm guessing close to double the peak hp when test pipes are installed w/ a better catback.

 

Wow, sounds like my car when I took out the pre-muffler. That went right back in....

 

my mines pipes should be here anyday now
g356gear, do tehy come with gaskets and any screws ive been wondering that.

 

did u throw a code at all with the test pipes??? i have an 04' G35 and im going to order them.. but i dont know if the 04's will cel.

 

Thanks for the informative post and chart. As mentioned by several members, replacing the OEM catalytic converters is primarily a torque improvement, not a peak horsepower gain.

 

thank god I found this thread, I have been thinking about doing the same thing and I finally found a sound clip...damn the stock exhaust with test pipes sounds sick as hell!

 

Selling Everything Must Go Pm If Interested.

 

If you had plenum, cams, intake, exhaust --- the cats would be holding back more power

Even still the car sounds good and makes more power pretty much everywhere thats usable in racing

Nice clip too