Thread: Went 3" Exhaust, Lost hp...

bigger is not always better when it comes to headers.. there is usually a choke for a reason. my header chokes down to 2.25 then out to 3in. if it were not the for the choke i would loose a ton of power.

the runner lengths and chokes all have to work together..

So true. Much thought wasnt put into the choke.

I should be getting a 4-2-1 that chokes to 2.5" then to 3"

Funny enough, I normally record 1/4 times with my Apexi RSM at 15.2 - 15.3 with the 60mm cat back.

Since I went 3" and saw the loss of power I retard the timing to about 10-12* from 15*. Was practising my lanuch and recorded 1 run using the Apexi RSM. 14.37 sec. Must be the extra torque

Peace

Here are the graphs for you to scrutinize:

whats what?? is this after tuning a little with your custom stuff or is this with the new header or??

From the first post in the thread, I'm assuming that the 173WHP run is the before run with 60mm exhaust, and the 163WHP run is the after run with 3" exhaust and modified header secondary piping.

The first thing that jumps out at me is that you are probably activating your cams later than you should. I get a real smooth power curve activating SR16VE cams at 4400 intake and 4700 RPM exhaust. You need to switch to the high cams sooner to keep the low cams from tailing off.

Second, in the "before" run (173WHP) something is happening at 7100 RPM to cause the power to drop off. It could be that one of your cams is switching back to the low cam, but there is something major happening to cause this drop in power. This problem only got worse later (after you put in the new exhaust) and I'm wondering whether both of your cams are switching over during these runs. Note that after the major power drop on the "before" run, the curves track roughly together for all 3 runs, potentially indicating a common problem.

I'd recommend that you do some checking on the reliability of your cam activation. If you think all is good, then go to the dyno and make some runs on your low cams, and with the high cams coming on separately (one at a time) to see if you can duplicate these latest runs and isolate your problem.

Also, double check fuel pressure at high RPM to make sure that your fuel pump is up to the task. I had some high RPM fade in power with a marginal stock fuel pump, but nothing as dramatic as this -- this looks like cams not activating to me.

Good luck finding your problem.

Bill

exhaust leak somewhere? put timing to 15

Presently I cant activate separately as I am using a VTEC controller.

The cams are activating ok though.

Will look into he fuel pump.

Peace

It looks like your VVL shuts down after 7100k or am I seeing things?

Well based on the look of the graphs the question of fuel came up.

Well did a wideband test on car and I AFR is at 12.8-13.2 for most of the bad at WOT.

That's fine as far as I am concerned.

Happy I did it, since it was the 1st one I did since going Calum Basic.

Will take some time soon, go back on the dyno and play around with dizzy timing, vvl points etc, especially since I have not dynoed after removing the stock primaries with long 2" secondaries and putting on the modded SSAC.

Peace