1M downpipes on a 135i

[cbl117]

Assuming you have a N54...can you swap the OEM 135i downpipes for 1M high flow downpipes and gain performance, no CEL and pass california emissions tests? In theory this seems like a good compromise if you can find a set used. I've read that guys who swap their stock 1M downpipes for catless see very little gains (8-12whp).

[Dackelone]

I think 8-12whp is nothing to sneeze at! DP's don't really help you unless your making over ~420 Hp. And even then I bet you loose a little on the low end under 2.5K rpms. When I installed my N55 mids on my SW flash tuned N54, I noticed a slight drop in low end torque. But at WOT they seemed to make more Hp. Well... lots of noise anyways.

[cbl117]

Originally Posted by Dackelone

I think 8-12whp is nothing to sneeze at! DP's don't really help you unless your making over ~420 Hp. And even then I bet you loose a little on the low end under 2.5K rpms. When I installed my N55 mids on my SW flash tuned N54, I noticed a slight drop in low end torque. But at WOT they seemed to make more Hp. Well... lots of noise anyways.

I agree 8-12whp is nothing to sneeze at. Thats why I'm asking my question above. From searching it appears that DPs are typically good for 20-30whp on 135i. If 1M owners see an 8-12whp increase by going to catless, then 135i owners should see a 8-12whp increase by switching to the 1M high flow DPs.

The switch to 1M DPs, I'm assuming, would keep the CEL away and allow you to pass emissions. This seems like a great compromise....so....I'm wondering why I don't see any discussions on this. Has someone tried this and has dyno results to show perfomance? Am I missing something?

[Dackelone]

You should talk to Harold at HP Autowerks. I think he was the first one to tell us about the 1M's higher flowing DP/cats. I bet he would know.

[cbl117]

Originally Posted by Dackelone

You should talk to Harold at HP Autowerks. I think he was the first one to tell us about the 1M's higher flowing DP/cats. I bet he would know.

Thanks Dack, you have a contact #?

Just throwing this out there for all the other addicts....if anyone is willing to donate their 1M DPs I would pay for pre/post dynos and installation costs and of course share the details with everyone.

[RW Carbon]

Hmm this is a really good question! I would imagine there are some differences in the computer though that account for different exhaust metering on the 1M.

[ilikebmxbikes]

I doubt the 1M downpipes alone will give you any measurable advantage or offer any tuning opportunities that are not present with the n54 ones.

[Dackelone]

Originally Posted by cbl117

Thanks Dack, you have a contact #?

Originally Posted by HP Autosport

..

http://www.hpashop.com/1M_c246.htm


Harold is also on the forums here too. I think his user name(is now): HP Autosport I just remember his shop is in Santa Barbra.

[mike@x-ph.com]

Originally Posted by cbl117

Assuming you have a N54...can you swap the OEM 135i downpipes for 1M high flow downpipes and gain performance, no CEL and pass california emissions tests? In theory this seems like a good compromise if you can find a set used. I've read that guys who swap their stock 1M downpipes for catless see very little gains (8-12whp).

If you can get one for really cheap or free and you do the swap yourself why not. But if its going to cost a lot of money i would not do it.

[ShocknAwe]

If I recall correctly the cats on the 135i N54 DPs are 600cpi, and the cats on the 1M N54 DPs are 200cpi. Pretty big difference.

I don't know how that compares with aftermarket high flow catted downpipes. I've always wondered about pairing 1M DPs with a catless yet resonated midpipe on the 135i. The issue would be price and availability. Those OEM DPs are in no way worth buying new, and I haven't seen anyone on the 1M side selling their take-offs.

[cbl117]

Originally Posted by ShocknAwe

If I recall correctly the cats on the 135i N54 DPs are 600cpi, and the cats on the 1M N54 DPs are 200cpi. Pretty big difference.

I don't know how that compares with aftermarket high flow catted downpipes. I've always wondered about pairing 1M DPs with a catless yet resonated midpipe on the 135i. The issue would be price and availability. Those OEM DPs are in no way worth buying new, and I haven't seen anyone on the 1M side selling their take-offs.

Thats good data. Seems like a worthy upgrade if the parts could be had for cheap. The setup you describe would be exactly what I'm going for: High flow catted DPs -> Catless & Resonated Midpipes - > Berk Street Axleback.

Not to sound like a broken record, but....anyone willing to donate/sell OEM 1M DPs cheaply? I'll be willing to front the dyno costs to compare for the forum.

[ShocknAwe]

Originally Posted by cbl117

Thats good data. Seems like a worthy upgrade if the parts could be had for cheap. The setup you describe would be exactly what I'm going for: High flow catted DPs -> Catless & Resonated Midpipes - > Berk Street Axleback.

Not to sound like a broken record, but....anyone willing to donate/sell OEM 1M DPs cheaply? I'll be willing to front the dyno costs to compare for the forum.

Might be better to post in the 1M forums and see if anyone has a set they don't want.