I've heard from several people on these boards that there are a number of mods that will hurt your power. Which ones will and which ones won't?

I'll list the ones that I have heard mentioned (I'm not the one making these claims though....so don't flame me).

1)Plenum: I'm heard changing the plenum can hurt your power.
2)CAI: A popular mod, but now many people are knocking it big time.
3)Test Pipes: I've heard these can REALLY hurt your power.......I'm willing to believe this one more than the two listed above. Our G35's need back pressure.
4)Some have claimed the Pop Charger will cause you to lose power. Some claim you gain.

Any others? Anyone wish to debate these? Do you have dynos to prove/disprove any of the above?

 

Theres a reason its called an upgrade. Only rumor and somewhat proven dyno is from the Injen CAI (which I have) gives like 4 to the wheels and looses tq. Oh Well, I dont race so I could care less. Why would test pipes loose hp? It weighs less than the stock cats...no resonator/filters....The pop charger is the best in my opo.

 

From what I've heard, the test pipes really only work well when you are using FI. Typically, the lack of back pressure (after removing the cats) causes you to lose power.

Again, this is what I was told.

 

it isn't as simple as "this mod makes you lose, this one makes you gain"

In general breathing mods tend to deliver power at the high end of the rev range.
Some poor choices may lose some at the low end. A CAI can often be a misleading name and change. Many of the most popular CAI's actual suck in hot engine air from the engine compartment. As the intake temp rises, the engine ECU will back off timing and such to protect the engine.

So it is about some understanding and choices.

It is like in the old days, I used to laugh my *** off at the high school kids that would take a mustang for example, and stick on a big exhaust, a huge carb, and hood scoop... but had no understanding of tuning, jetting the carb, etc.

 

Some mods may work better than others. A long tube CAI may not work well with the Crawford plenum, so even though each mod might give a few HP, together, they may not be great.

Plus, if a certain mod throws your A/F off, then you may end up losing power. DaveO and I were discussing this the other day, as I'm getting ready to finally install my Gruppe-S y-pipe in conjuction with a japtrix B pipe and extension, portmatching and polishing what I can.

 

That's very true, I had a K&N CAI and Kinetix Plenum, but after installing the stock intake with K&N drop in, I actually noticed an increase in exhaust sound and low end torque.

So basically, what most of the people have been saying is true, for a NA engine, most mods will increase HP or torque at some point in the power band. But whether or not it really increases your overall performance, is subjective and varies depending on your application and situation.

So, go for it! :-) Get everything you can!

 

If you guys saw the OEM cats you would chit! I would get some high flows.

 

G352NV,

Now THAT is the mod that I have heard makes a real difference. Instead of using the test pipes, going with the high flow cats makes a bigger difference because it keeps the required back pressure for the car while eliminating the bottleneck in the exhaust system.

I'm thinking about getting the Crawford cats for my car here in the next 1-2 months, while keeping the stock exhaust system (most likely going to a Borla system down the road).

 

Back pressure is not a good thing, no matter which way you look at it. Exhaust velocity is what is key to making good power. The goal of a good exhaust system should be to minimize restrictions, keep the exhaust gases hot, and to keep the exhaust gases flowing at a high rate. Adding too large of piping to your exhaust can kill power because the exhaust flow in the lower to mid range rpms becomes turbulent in the pipes and cools. The exhaust velocity is killed therefore the motor looses power and feels lethargic. Not until the upper rpms does the power come alive, but it's too late because in a race, the car spend more of it's time accelerating in the midrange rpms, not upper rpms. Bigger piping is not always better. Also, many NA cars make more power using a stepped exhaust system which starts with larger piping near the motor and steps down to fractionly smaller piping towards the exit point. The stepping helps keep the exhaust velocity up. It cracks me up when people put overly large piping on these 3.5 liter motors. The Chevy 350 275-285hp LT1 V8 used from 92-97 in F-body did completely fine with 3" piping. For those that don't know, F-bodies (ie Camaro/Firebird) do not have true dual exhausts. They're a single pipe exhaust. Stock is 2.7" and ideal for a NA mods is 3". If a 275-380hp V8 can make do with a 3" exhaust, why does a 260-300hp 3.5 liter V6 need anything more than 2.6" piping?

Forced induced motors are the only motors I know of that can take advantage of really large piping because they move massive amounts of air.

As for CAIs on the Gs, what's the point? The stock intake can already move more air than the motor can suck in, the stock intake gets fresh ambient air, and the stock intake is in a natural pressure zone of the car. Why would you want to change it?

I'm certain test pipes do make power, however I don't think the power is has much as some would like to believe. Test pipes add a lot of noise which can easily fool the senses into thinking you're going a lot faster than you really are. The cats serve as a great noice suppression device. Remove those and all of sudden the exhaust gets raspy and the VQ's exhaust noise has a strange metallic ping at certain rpms thanks to the firing order of the motor.

 

So Dave what do you recommend? I was planning on doing the Crawford Plenum, High Flow cats, and a Fuji Exhaust with gruppe Y pipe, grounding gear and a Z tube. If any of these are a waste, I want to know, as getting a solid answer has proven difficult.

 

I've had stock cats, high flow cats and now test pipes. To be honest the gain you get from high flow cats to test pipes is so minimal that it is worth it to just get high flow cats just for the noise. My test pipes along with the nismo exhaust is obnoxiously loud.

I wont say there is a strong gain with test pipes, it just feels like the power doesn't taper off on the top end.

 

Grounding gear???you have a 6mt...

 

yeah - I actually took my Stillen cat back off today - I just couldn't take it anymore.
The noise was too much.

I drove the car a bit after, and frankly i don't notice any diff between the stillen and stock exhaust powerwise. I will see what I think since I am driving to Vegas and laughlin tomorrow. Frankly for the 6 - 9RWHP the exhaust may have been worth... it wasn't worth the noise.

Damn I felt so much better driving it with the stock exhaust.

I kept the high flow cats of course.

A note to those thinking about exhasuts systems, and particularly the Stillen.
After only maybe 3 or 4k miles... the slipjoints used to assemble the section wre completely frozen - I actually had to cut pipe to remove the exhaust (a little insult to injury)

 

I agree with DaveB, the stock intake is doing a good job, it is pulling air from the area just after the grill. I've noticed also an opening, in the plastic cover infront of the Power Duct, that directs air to the Power Duct area. It looks like much thought has gone into the stock design.

My only mod on my 2005 G35 AT Coupe is a Nismo air element, which I've noticed an improvement after installing. This filter has half the number of fins (wrinkles) compared to stock and is made of different ( I guess better) material. It cost me about $100.

 

If you have fewer pleats you are cutting your surface area down sharply....either your are going to clog up sooner or you aren't filtering as well. You can't have both with less surface area, unless you meant to say the Nismo has twice as many as the stock.