Secondary cats deleted - Dragy tested

Cal1415

Lurker
Dec 25, 2016
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Recently had my secondary cats replaced with 2.5" resonators and did some before and after tests with Dragy. Tests were done on exactly the same piece of road, same tune and boost. It was the same Shell v-power 99 Ron pump fuel (93 octane US). The only difference was the secondary cats removed to make the comparison as accurate as possible. I already have VRSF downpipes so was unsure if the gains would be worth it.

2006 E92 335i Auto - Full Weight
Stock turbos
JB4 + Race BEF Map 1 (15 psi)
XHP stage 3
FBO
Stage 1 LPFP

Tests done were 100-200km/h.
With secondary cats: 9.28 and 9.31
Secondary cats removed: 8.94 and 8.96

An improvement of 0.34 seconds. I'll get my car on a dyno soon to confirm.

I have just switched over to E50 and ran 7.72 and will be at the drag strip next week with 170kg (370lbs) removed, so will be able to get a 100-200 comparison.

Calum
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SlowE93

Lieutenant
Jul 2, 2017
776
308
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E93
Recently had my secondary cats replaced with 2.5" resonators and did some before and after tests with Dragy. Tests were done on exactly the same piece of road, same tune and boost. It was the same Shell v-power 99 Ron pump fuel (93 octane US). The only difference was the secondary cats removed to make the comparison as accurate as possible. I already have VRSF downpipes so was unsure if the gains would be worth it.

2006 E92 335i Auto - Full Weight
Stock turbos
JB4 + Race BEF Map 1 (15 psi)
XHP stage 3
FBO
Stage 1 LPFP

Tests done were 100-200km/h.
With secondary cats: 9.28 and 9.31
Secondary cats removed: 8.94 and 8.96

An improvement of 0.34 seconds. I'll get my car on a dyno soon to confirm.

I have just switched over to E50 and ran 7.72 and will be at the drag strip next week with 170kg (370lbs) removed, so will be able to get a 100-200 comparison.

Calum
View attachment 40969View attachment 40970View attachment 40971
Nice.....its possible, but also possible that it was cooler one day vs the other. Tail wind vs head wind. Shifting done at same exact rpm etc.
Also possible, cats were already getting clogged up or breaking apart internally.
Either way, enjoy the faster times 👍🏽
BTW, Dragy also shows a different slope for both runs....
 

Cal1415

Lurker
Dec 25, 2016
18
23
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Nice.....its possible, but also possible that it was cooler one day vs the other. Tail wind vs head wind. Shifting done at same exact rpm etc.
Also possible, cats were already getting clogged up or breaking apart internally.
Either way, enjoy the faster times 👍🏽
BTW, Dragy also shows a different slope for both runs....
The DA was 163m higher on the quicker run although 3 degrees cooler.
Wind speeds and direction I'm unsure of exactly.
Max rpm was used in xhp to shift at 5900rpm in 3rd gear on all tests.
The cats look visually ok with no signs of damage.
The slope is different due to the shorter distance used but you can see it's the same road.

I just wanted to share some real world results, the power gain is probably 10whp as to be expected. It certainly makes the stock turbos feel better at higher revs.
 

SlowE93

Lieutenant
Jul 2, 2017
776
308
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Ride
E93
The DA was 163m higher on the quicker run although 3 degrees cooler.
Wind speeds and direction I'm unsure of exactly.
Max rpm was used in xhp to shift at 5900rpm in 3rd gear on all tests.
The cats look visually ok with no signs of damage.
The slope is different due to the shorter distance used but you can see it's the same road.

I just wanted to share some real world results, the power gain is probably 10whp as to be expected. It certainly makes the stock turbos feel better at higher revs.
Yeah, dont get me wrong. Was just sayn theres variables. I ditched those long ago as well. Timing corrections I was having were almost non existent after pulling them off....then they came back 🤣🤣🤣
 

Cal1415

Lurker
Dec 25, 2016
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Yeah, dont get me wrong. Was just sayn theres variables. I ditched those long ago as well. Timing corrections I was having were almost non existent after pulling them off....then they came back 🤣🤣🤣
You made some valid points and it's difficult to eliminate all variables. The only downside I'm getting now is the smoke when the oil gets to operating temperature. Quite embarrassing actually... So I'm going to change the valve cover, vcg and upgrade the pcv valve and hope that fixes it. Do you have any idea why your timing corrections came back?
 

SlowE93

Lieutenant
Jul 2, 2017
776
308
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Ride
E93
You made some valid points and it's difficult to eliminate all variables. The only downside I'm getting now is the smoke when the oil gets to operating temperature. Quite embarrassing actually... So I'm going to change the valve cover, vcg and upgrade the pcv valve and hope that fixes it. Do you have any idea why your timing corrections came back?
They come and go. From what I have seen, mostly weather dependent. I see them more in cold weather vs warm weather.
 

Jern54

Corporal
Oct 18, 2019
143
71
0
Netherlands
Ride
E91 N54 335i
Nice info! I'm also about to replace the sec cats for a vibrant 1792 or maybe just a open pipe. Did you do anything to the center muffler?
 

Cal1415

Lurker
Dec 25, 2016
18
23
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Nice info! I'm also about to replace the sec cats for a vibrant 1792 or maybe just a open pipe. Did you do anything to the center muffler?
Hi Jeremy, the resonators I used were only €40 for the pair and they sound great. On the E92 there isn't a center muffler but my exhaust is otherwise stock. You might experience some drone with straight pipe so resonators are a safe bet if you're not looking to increase noise levels.
 
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typedRew

Sergeant
Feb 25, 2019
404
213
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2009 335i xDrive
Thanks, I forgot to add that I had max rpm set in xhp to shift at 5900rpm in 3rd gear which is important to keep the results more accurate.
on my stock turbo setup i would have xhp shift 5900 and let 4th run out through the 1/4 mile or for 100-200
 
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Jern54

Corporal
Oct 18, 2019
143
71
0
Netherlands
Ride
E91 N54 335i
Yeah, atm i have cut out valves to bypass the rear muffler and it drones quite a lot. I think I will start to empty the center muffler on my E91 and delete the sec cats. If its too much with the valves closed I will install some resonators.
 
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