Stock DP ... how much HP loss?

[Ronin135]

I've modded my car with AFE Mach II exhaust, JB4, BMW intake, VRSF charge pipe. Awaiting FMIC... my question is the DP. Emissions around here bite, in Colorado. If I leave the stock DP in what type MAP would I run, I currently run MAP5, can I run MAP 2? Also what amount of HP would I loose?

[iminhell1]

I'd go with not much.

I've run close to the same times stock/tune and FBO/better tune. The only thing that changed was trap speeds, gained 10+MPH FBO.

[drwillb]

The gain is in spool time vs hp gains.

[iminhell1]

Originally Posted by drwillb

The gain is in spool time vs hp gains.

I wouldn't say that.
I didn't notice any change in spool. If I dig back in logs I think they'll say similar.

The gain is in the lower DC at high boost, high RPM. It saves the turbos from overspinning and destroying themselves.
Most are really confused how mine have lived so long over 20PSI and half their life at 25+ (That's 100,000 miles total).
It's because I've kept DC in check. With the inlets and the DP's it's been easy to make them breath and last.

But it hasn't gained me any measurable better track times reliably.
On the street that's a different story. It's been much quicker. Surprised quite a few.

[Ronin135]

I’m sorry what’s DC?

[ShocknAwe]

Dutycycle.

I'd say once you go beyond standard FBO it probably doesn't matter much what DP is used. You could also look into a 200cpi high flow cat for DP piping and use the same in the mid. Might be enough to pass your local emissions.

[Just Apex It]

Originally Posted by ShocknAwe

I'd say once you go beyond standard FBO it probably doesn't matter much what DP is used. You could also look into a 200cpi high flow cat for DP piping and use the same in the mid. Might be enough to pass your local emissions.

This would be your best bet. Since you're N55, just do a high flow catted downpipe and swap the N55 midpipes for N54 midpipes (which have secondary cats) and you should be golden hopefully.

[Ronin135]

Originally Posted by Just Apex It

This would be your best bet. Since you're N55, just do a high flow catted downpipe and swap the N55 midpipes for N54 midpipes (which have secondary cats) and you should be golden hopefully.

Thanks that might be a good option.

[SD_N55]

I passed California emissions with a Wagner catted down pipe on my n55. As the DP has gotten more miles it started to throw a CEL(40k?+). Last year I put an O2 sensor spacer On and flashed(mhd) back to stock and was able to pass. That was the first year I had to get it smog’d so we’ll see if I pass next month. Regarding power I have no idea as it was one of my first mods. Hopefully this is helpful.

[Mark Aubele]

Originally Posted by iminhell1

I'd go with not much.

I've run close to the same times stock/tune and FBO/better tune. The only thing that changed was trap speeds, gained 10+MPH FBO.

The 10mph trap speed change indicates a huge hp gain. ET doesn't necessarily correlate to hp, trap speed does.

[iminhell1]

Originally Posted by Mark Aubele

The 10mph trap speed change indicates a huge hp gain. ET doesn't necessarily correlate to hp, trap speed does.

I know. Thing is though speed alone doesn't win.
For the short run stuff, not much benefit. For the 1/2 mile or longer you'll see a big change.
It's one of those situations where the person needs to build to a goal and not just haphazardly throw parts at it just because they have the money to do it.

[Mark Aubele]

Originally Posted by iminhell1

I know. Thing is though speed alone doesn't win.
For the short run stuff, not much benefit. For the 1/2 mile or longer you'll see a big change.
It's one of those situations where the person needs to build to a goal and not just haphazardly throw parts at it just because they have the money to do it.

If you picked up 10mph in the quarter and didn't pick up at least 1 second in ET, there are issues in you getting the power down, whether it be a car, traction, or driver issue. So yes, it would be a massive benefit for short run stuff.

[Jeff@TopGearSolutions]

10 MPH in the quarter-mile is huge and there is just no way downpipes alone will do that. Other factors definitely factor into that time difference for sure. Any seasons drag racer will verify. In fact, no way. They are about a ~20WHP gain for most catless downpipes. Aside from the gain, the reduce backpressure, lower EGT's and reduce WGDC.

[Mark Aubele]

Originally Posted by Jeff@TopGearSolutions

10 MPH in the quarter-mile is huge and there is just no way downpipes alone will do that. Other factors definitely factor into that time difference for sure. Any seasons drag racer will verify. In fact, no way. They are about a ~20WHP gain for most catless downpipes. Aside from the gain, the reduce backpressure, lower EGT's and reduce WGDC.

I think he gained 10mph with FBO/tune/DP together.