Wait! so you removed the cats, but didn't advance the timing? i thought you were having it dyno tuned? if you were just removing the cats without advancing the timing, then there is your problem...

wait, what? sue someone for selling things legal to make because they CAN be used illegally? Let's get together and sue wrigley while we're at it.

But I agree with your main point... I can understand why the car would not make more power.. the headers are restricting the hell out of the engine already... so a small amount of exhaust moving at very high speeds aren't affected at all by the cats because there isn't enough of it moving at one time.

If you look at my signature, you'll see that I already have headers on the car

The cats were removed, then the car was driven around to let the car adjust, then it was dynoed again. The ECU's ignition mapping was not changed.

We spoke with Kleeman before we got started. My ECU is currently tuned for the mods I have minus the cat removal. I was originally going to switch over to a custom Kleeman ECU flash because they can remove the CE light for no cat, and also to get a better tuned map. Once we saw that the spacers were enough to prevent the CE light from coming on, we spoke with Kleeman again, and they said that I wouldn't really gain anything by switching to their ECU. My AFR is still on target.

The primaries are going back on today or tomorrow. I'm going to leave the secondaries off for a while, and make sure that the car is behaving, then do another 93 octane pull. After that, I'm gonna fill up on 100, drive around for a while, then do yet another pull to see if that makes any difference

then one of two things is happening with kleeman:

1. either they don't really have complete control over the timing and fuel in the ecu...

2. or they don't really know what they are doing or are not willing to go through the process of actually taking the time to get it right...

it is common practice among tuners that are experienced to advance the timing about 4 degrees as a starting point when removing cats, then working from there...

Are you sure??



That's really interesting though.

Well I'm not sure. I personally didn't speak with Kleeman. I had several conversations with Powerchip, and after speaking with them, I will never buy any of their products again. The rep that I spoke with didn't seem to know the basics of engine managment. My shop spoke with powerchip after I did and go the same impression. My shop then spoke with Kleeman a couple times, and at least they were able to help me (The original conversations were about removing the CE light for no cats).

Hey since your going to be doing all these dyno's why don't you test out some different air filters, so we can see the difference k&n vs. stock. Maybe get some greens or BMC's which are suppost to be better then k&n to see if they really are. You could also do a run without filters to see how much gain there is.

Call RENNtech. I'm sure they will be a lot more helpful.

1FASTC32, another thing that should be noted is that most people that remove secondary or primary+secondary cats do NOT get a custom tuned ECU after doing it. People add headers and don't touch the ECU and still see large gains, so I was hoping to see some gains from the more free flowing exhaust. I did this experiment just to see if removing the cats was an easy way to gain power.

If this data is correct, it would also suggest that putting a larger/more free flowing exhaust on the vehicle would not produce more power (which has pretty much been accepted by everyone).

My ECU has the stage 2 map, so I'm sure that the ignition is already advanced beyond stock. I agree with you that it could probably be advanced more, and I would see bigger gains after doing that.

Kleeman was able to provide all the info and have the ability to do everything I needed. I'm sure RENNtech could too

I already did the stock vs green vs k&n by my seat of pants, and didn't notice any difference. Unfortunately I don't have the filters anymore, and I'm not gonna lay down the $$ to disprove the green is better than k&n myth

Where are you getting this 45hp number from? Is this an up in the air 'ohhhh, you'll gain abouuuuut, lets saaay, 45hp' guess? That kind of talk isn't worth anything. Do you realize what a huge gain 45 hp is? Just by switching my current headers and no cat system to the special Kleeman headers and advancing the timeing on pump gas I'll gain 45 up!? Don't spread such nonsense

If you still have the stock ones you could still do the dyno with stock vs. k&n vs. no filters.

To get more benefit from removing primary converters you would need to make a long tube header. In the end stock exhaust port and cam timing is the ultimate limitation of how much of a restriction the converter will be.

How power did you put down on the dyno?

interesting...thanks for the info

That makes sense. So it seems like even with stage 2, the exhaust is not a restriction. Looks like you have to port the head before the exhaust becomes a significant part of the power equation.


It put down 312whp. Before eveyone jumps on how low of a number that is, the pulls were done on a Dyno Dynamics dyno, which output significantly lower numbers than a Dynojet. Yes, I will be doing a pull on a Dynojet so that I have a number to compare with others.

EDIT: The 312whp was with all 4 cats on

On Dynojet you will be close to 350 RWHP, which you where you should be with your mods.

Heads and cams are the next step. There is really no other way on the 91 gas. More boost will only hurt the car.

Now this is an interesting quote:

http://www.amgpower.com/community/viewtopic.php?t=2076

axsaltc32
AMG Enthusiast

"ALso, re: Kleemann, cory did mention evosport headers but says he isn't convinced with posted gains as oem down pipes are used which are pretty small."

I know the evosport header make power, according to the dyno sheets, but the the down pipes may be limiting some also?

If the down pipes are a limiting factor, before geting to the cat, then removing the cat does not help much. In the S4, the downpipe/cat upgrade improves flow a lot.

why would they post something that they can't back up? Vadim, can you shed any light on this subject? anyone else have the evoport headers? this is what i am planning on getting mainly because the cost is astronomical on any of the other companies...

interesting thread.

here's my experience.

in an effort to produce more exhaust noise as rpm feedback for my track driving I decided to "vent" the stock exhaust. i got to 16mm bolts/nuts from home depot. the bolts were cut short so that when threaded into nut they were fully enclosed. i then had the nuts welded into the outside of piping of stock exhaust on the bend before the muffler. intent was to remove the bolts at track hence allowing unmuffled gas/sound to escape. the nuts do not protrude into the exhaust piping so there is no reduction in flow through system.

results.

yes louder (actually nice) but not loud enough to overcome wind noise at speed. still; i am able to hear rpms when cornering.

power! yes more power. with the full thermo insulated sl55 intake there is a definite increase in midrange power. the gain seem synergistic vs intake/ exhaust. seat of pants 15-20hp??

my plan is to insert 4 more bolts into exhaust making it evem less restrictive. this is almost like a supertrapp system.

i guess the inference here is that the stock exhaust is restrictive. maybe the cats do flow well but this is the choking point???.

I would not recommend venting the exhust in this manner for everyday driving as hot gas will be percolating upwards around the rear of car (gas tank). not an issue at 120 mph tho!

I just picked up the car. The primary cats are back on, but the secondaries are still off. Just as a reminder, the car sounded AWFUL with all the cats off. The car sounds so much better now, but it still sounds a little like a riced out Civic under some WOT conditions. I'm probably going to put the secondaries back on, but I want my car back for now

this is what i am worried about...i don't want the car to be loud at all, i have been down that road with other cars and i enjoy the fact that i can drive this car everyday and not worry about it being too loud or annoying the crap out of me...i guess i want my cake and eat it too, but that is why i bought an AMG...