I recently installed a new header and downpipe. i have noticed nice gains on the top end, mostly on the freeway. but on the lower end(street racing) i noticed a big loss of power. is this normal? what mods can i do to counteract this? and dont say turbo, cause i would if i could. thanks for your help

 

Loss of back pressure causes low end loss of power. You need to open up the intake to gain some back. You can also get the RRM ECU upgrade to gain more low end back.

 

open up the intake with what? throttle body? i have cai. would 2 1/4 piping from the catback help at all?

 

The more you open up exhaust the more you'll loose the low end. Stick with the header/test pipe combo and muffler(axle back). Then get the TB to unblock that restriction and allow more air for more power on both high and low ends. Then get the ecu as this will get your timing and fuel curves into shape for what you have. You'll find you'll be better than before down low and even better on the high end! Also that Injen has been proven to be one of the worst CAI's. Basically because it puts MAS in middle of pipe. You should get a CAI which puts MAS down by filter/air entry... as at that point air is cooler/denser and the MAS/ECU will see this and give you better fuel/timing based on this. Should also see better throttle response. I recommend the AEM... may be able to find one from board member. Save you some $$$!

 

Most people are reinstalling the 2nd cat to give that backpressure back. Backpressure is our friend. I'm still running my stock downpipe and exhaust (except for the cats are removed).
TB replacement is another option. Check with RPW- they have LOTS of TB options. With the tiny opening in the MAS and the small TB, even having a CAI or SRI will only help so much.
Those grounding kits that several people are installing/making themselves can be really helpful with reducing the lag in TB response (the "flat spots"), which will make it feel like more low end power. ECU flash or a piggyback will help some, and the piggyback can be a fun toy if you kinda know what you're doing (or know someone who knows). Fuel Pressure regulators are supposed to help with the low-end lag, too, since they get more fuel to the engine faster (or something like that ).
Lots of options. Good luck.

 

i have cai, header, d pipe, 2nd cat, stock piping, muffler.

so TB, Ground Kit, FPR should help? and of course the ecu.

 

Back pressure or bottleneck is not your friend. Constant flow is the way to go.

The header design affects its power too. 4-2-1 works on low to mid range while a bit on top. The 4-1 sacrifices low end to explode more power in the middle to top range. Example: I have never seen a 4-2-1 design for an ITR. What's the use of TQ for them? Every one designed a 4-1 for an ITR.

A larger TB isn't exactly your friend. The bigger it is, the more you sacrifice on the low end for more gains on the top end.

Another example is the Q45 TB (70 - 100mm, no one on the net can get their story right on its size). They have jerry-rigged it to Silvias, Skylines, 300z's, and even the H&A boys. They're sure not doing it for TQ. They'res acrificing low end power for huge gains on the top end.

 

4-1 headers are designed primarily to preserve back pressure between the engine and down pipe. thats why some are "equal length" and im pretty sure that opening up the intake is gonna help with hp and torque in the lower end and hp in the higher end. back pressure is needed if you want any chance of having torque in the lower end. which is why having the resonator still in the exhaust system puts that 1 3/4 or whatever size it is choke on the exhaust that saves all the seals in the valvetrain. when the pressure in the exhaust system drops below 14.7 psi, say, when you shift gears, a vaccuum is created and cold air from the atmosphere is forced into your exhaust. if and when this cold air reaches the seals in the valve train, it cause them to contract from being so hot due to exhaust gasses. when you put the throttle back down, the pressure increases again, and hot exhaust flows through the manifold, heating the seals back up. think about how many times you shift, thats a lot of extra wear on the valvetrain.

 

That's what I'm saying, thanks gaijin. This boy NEEDS! backpressure to get those low end torque numbers up. Torque gets you going, HP keeps you going.

He's already doing the "constant flow" thing and he doesn't like it. More of the same and he'll hate it. Artemis pulls through the entire powerband specifically because I've kept a balance between open flow and backpressure. Other cars that I've been in with just open flow aren't nearly as much fun to drive and feel like crap coming off of a line.

EDIT: to clarify, I'm talking about the backpressure, not the valvetrain wear issues. That's something new to consider!

 

I reinstalled my 2nd cat to gain back some low end with my setup and it helped a ton. I never really felt any loss in low end, though, with the RPW header/downpipe.

Good thing the website is down right now , but their header primary piping is three times longer than any other header system for the Lancer. When installing I had to bring it from the bottom of the car up cuz the primary piping feeds all the way down toward the undercarraige, compared to stopping where the stock downpipe is. I didn't even feel much of a loss in low end with my testpipe on; the biggest reason for installing the 2nd cat was to eliminate the farting noise.

 

before i bought my rrm headers i had testpipe cai 2.25 cat back straight through muffler. when i put my headers on it sucked, low end power was gone felt like a civic i did gain alot of top end power and ****ing loud as hell. called rrm rob told me to put the 2nd cat back in problem solved. if i go to the drag strip i will put my test pipe back in to get a little more top end power.

 

First of all... How much did you gain/loss all through your powerband? Or are you going by the seat-of-the-pants dyno? Without any quantitative, it is really hard to analyze the situation for you accurately. But to answer your question, yes, a loss of low end power is to be expected as you open up your exhaust system. The scavanging effect gets destroyed more as you open up the exhaust system sooner and slow down flow velocity.

The way I see it is, if you are looking to improve your car's performance, top end power is the way to go. (without being too extreme about it) You can always try and keep your RPM up during a launch by careful controlling your clutch release. I've been able to launch my old GTi VR6 at above 4kRPM and I've had a number of successful 6k launches with my friends' GSRs and ITRs. The key is to learn the car and its new found characteristics. Oh by the way all of the launches mentioned above were done on regular street tires V-rated radials and Z-rated radials.

To gain your low end back, you are going to sacrafice top end again, unless you refine your fuel mapping and ignition timing via ECU tuning. By messing with the exhaust and intake, the gain you see will be minimal and chances are you will lose one thing or the other. Fuel pressure regulator is not going to help your low end, you are not having a fuel problem.

 

<---Freeflow here and I have noticed no loss in low torque, my car goes like a bastard! I think you all are paranoid and have told yourself way too many times that you need backpresure.

Cold air hitting the valvetrain? Are you kidding me? How long does it take you to shift 5 mins? The vaccume would have to be insane to suck up 12 ft of pipe and hit the valves between shifts. I dont think so.

 

If you want back pressure/bottleneck, try grafting a mirage exhaust of 1.5 inches. The G93 guys have been plagued using shared parts off the G15.

The next Q is probably . . . the 2 1/4 exhaust may be a tad big for constant flow rate. Has anyone tried 2 inch piping? A few of the G93 guys have done so and have success w/ constant velocity of pressure. Of course, we have a tad smaller displacement, and the 2 1/4 piping does affect us more.

 

Personally, I rather have constant flow rather than bottleneck/back pressure. One of the reason for the cause of flatspots in the powerband, whether rich or lean condition, because the ecu is trying to compensate for the A/F ratio to the exhaust system, especially OBD2 systems.