[teapain]

As the title suggests, I don't have any intention of running a hi-flo or catless setup. I've done it before and found the smells were too much for me and my passengers living in an urban environment. I'm also an old man, now.

My questions are:

1. What would be the most amount of power one can extract from the B58 without going the hi-flow/catless route? I'm currently running BM3 stage 1 and am happy with it...but that itch to squeeze a bit more is there but again, not ready to ditch the OEM cat.

2. If I were to upgrade to a TU pump, would I see any gains at all on BM3/MHD stage 1? I see both companies list different stage 1 figures for B58 Gen 1 and B58TU. ie, MHD claims up to 420hp on Gen 1 and 440hp on TU)

[Skyhigh]

Comment to intro - The (emissions-compliant) high-flow catted DPs are only marginally more smelly than stock and that's only during cold-start, not during normal operation. IMO that is the best compromise.

Question 1: There is no easy answer. Cat converters don't deal with power, they deal with exhaust gases. The amount of exhaust gas (gas-flow) depends on the fuel mixture. The fuel mixture (boost vs timings, etc) depends on the tune and your environment. Either way - what suffers most is not your DP but your turbo. So how much strain and thermal stress would you like to put on it? And do you think driving in Canada is the same as driving down in south Mexico? Cruising the same as tracking? As you see - no universal answer here. It all comes down to reducing a safety net.

2. No, you will not see any gains just from upgrading the HPFP, unless you go to Stage 2+ (Stage 2 HPFP as MHD call it) and you use high octane / ethanol blend. Your stock HPFP meets the demand of Stage 1 and Stage 2.

Conclusion - you can eventually gain a few more PS with a custom Stage 1 tune, especially if you increase your octane, but to have a meaningful increase above an OTS Stage 1, you need an upgraded DP. And trust me - the effect of it is noticeable and measurable even without a tune!

[teapain]

Originally Posted by Skyhigh

Comment to intro - The (emissions-compliant) high-flow catted DPs are only marginally more smelly than stock and that's only during cold-start, not during normal operation. IMO that is the best compromise.

Question 1: There is no easy answer. Cat converters don't deal with power, they deal with exhaust gases. The amount of exhaust gas (gas-flow) depends on the fuel mixture. The fuel mixture (boost vs timings, etc) depends on the tune and your environment. Either way - what suffers most is not your DP but your turbo. So how much strain and thermal stress would you like to put on it? And do you think driving in Canada is the same as driving down in south Mexico? Cruising the same as tracking? As you see - no universal answer here. It all comes down to reducing a safety net.

2. No, you will not see any gains just from upgrading the HPFP, unless you go to Stage 2+ (Stage 2 HPFP as MHD call it) and you use high octane / ethanol blend. Your stock HPFP meets the demand of Stage 1 and Stage 2.

Conclusion - you can eventually gain a few more PS with a custom Stage 1 tune, especially if you increase your octane, but to have a meaningful increase above an OTS Stage 1, you need an upgraded DP. And trust me - the effect of it is noticeable and measurable even without a tune!

Much appreciate the insights and thoughts. 👍Definite moved the needle just a tad bit closer to hi-flo cat.

[PeterWT]

Plus one for Skyhigh's comments. If decide to get a high flow cat, don't waste your time and money with a cheap one. Get a real cat, like the AA GESi 400 CPSI.

[G.Newt]

Upgrading the exhaust will introduce some smell. I was high flo and then catless and only smelled it slightly at a stop light. Never had any passengers complain. Running an E mix helps with the smell as well.

Worst comes to worst, you can always revert back to stock DP if the high flow catted is not to your liking and recoup some of your costs. The TU will allow you to run the HPFP E30 maps with ease.

[B58 parts]

As an old man, with passengers, I can say the CG precision catted is really nice. No smells.

I tried a catless one, lasted a week.

Stage 1 tune is good on stock downpipe, I was mostly content with stage 1 17psi. Stage 2+ still with the cat, hpfp, e85 is really spicy. I think you're at the point of changing the cat.

[Jnat]

So i recently went from high flow 200 cel to kittyless. My 2cents is there is very little difference from stock to high flow in regards to smell but there is a more significant difference from high flow to kittyless. It's totally personal opinion, i'm on the fence, i can deal with it but i'll have to monitor how passengers feel about it! Oops, on topic, stage 1 390-410 whp ish...