Power gain

[trj]

Hello boys and girls!
I have a stage one with bmc and catback milltek. The tuner (AK-tuning Sweden) states 690 HP with this setup. 680 without Milltek. I'm gonna loose the sek.cats today.

How is this decat gonna effect sound and power?

Is this setup good for stage two now, and how big is that gain?


Could't find any info on this specificly.

Cheers/Robert

[cammmy]

MRC said mine made 730bhp/1000nm with panel filters, secondary decat and a Milltek cat back. I can't compare stock sound as I haven't heard one but I like how mine is.

[IanH755]

Any power/torque difference from removing the secondary Cats is down to the quality of the mapping software for the engine/gearbox. The power (bhp/PS etc) will only have a fairly small effect (20-40hp), instead it is the torque which can get a big increase (100nm+) but only if the torque limits on the gearbox are removed as part of the gearbox mapping.

So for example, Stage 2 should get you around 700-730hp and about 1050nm whereas Stage 1 will usually get you 670-690hp and 950nm.

As for the noise, there is very little difference when the cats are removed, you get more noise difference from removing all 4 cats (primary and secondary) which really adds some "bang" to the gear change noise.

[trj]

Thank`s for your answers guys!

The result of the cat delete according to the noise was amazing! The bangs between gears are so loud now, and the noise over all are higher.
You almost can hear every piston stoke, really love it! When coldstart it`s on the limit for what you can stand if you are close to the car at behind.
It`s a non resonated milltek with home made straight pipes mounted in the mufflers. It´s a little bit higher noise on the highway but not disturbing.

Ian: AK tuning states 680 with there softwear and filters, and 690 with Milltek. So my power should be around 730 now, or what do you think??

Robert

[IanH755]

Ah, your non-res exhaust is "custom" then, so that straight pipe makes a big difference as there's effectively no sound deadening left in it. Mine is similar and I love the gear change "aggressive bangs" noise which is soooooo different compared to the stock exhaust softer "fart" sounds!

You can run a little bit more boost now you have the extra restriction of the secondary cats removed (depending on the rest of the exhaust having no more restrictions and the age of the turbos) which means it should be able to reach over 700hp by now.

Most UK mapped Stage 2 cars get around 730-ish on MRC's dyno but obviously different dynos will give different results, so as long as you see about 20-50hp higher (depending on your car) then your stage 1 map then I'd be happy, but just remember its the increase in torque which should be the big difference with a stage 2 car, more than the fairly small amount of extra HP.

[trj]

Sorry Ian, I get confused here.
So what you mean is that, I now have stage 1 with aproximately 700 HP, but if I do a remap I can reach 730?

Robert

[IanH755]

To clarify for you, and this is based on what MRC do -

A stage 1 map uses a set boost level and timing which makes a rough BHP figure. If you then change a part of the exhaust to make it less restrictive, without doing anything else, you won't see much (if any) difference in power as the boost/timing is still the same and, even though you have removed a restriction, it is changing boost/timing which makes the extra power/torque.

However once you have a less restrictive exhaust (where you are now), you can now change the map again to run more boost/timing which becomes a stage 2 map. This is a different map to a stage 1 map, with different boost/timing to make the extra power/torque now the exhaust is less restrictive.

So for example (made up figures) -

• Stage 1 = 670hp & 950nm (can't run any higher HP)

• Stage 1 + secondary cats removed = 670-680hp & 950nm (but now able to run higher HP if remapped)

• Stage 2 = 730hp & 1050nm (now mapped for more boost for higher HP)

Hope that helps.

[trj]

Very good, thank`s so much Ian!!