So does a backbox delete rob power?

Hi Guys its Ross from Infinity-Exhausts. Very interesting to see the supposed loss of power from the Z4 with back box delete. Couple of questions really as obviously we don't want to sell products that create a power loss.

Firstly was the car Rolling roaded before the back box delete, and then afterwards? and if its was it on the same rollers?or because the M3 was there it was automatically assumed that if the back box was put back on the Z4 it would gain the power back? Obviously cars loose power over time but also a car does not always have the correct Power stated from manufacturers. So this specific Z4 could have already had power losses before the delete was done. What other mods did this car have? Some induction kits will loose power also. Yes N/A cars need back pressure but we figured the centre silencer and cats would be more than enough.

Please note that back box delete is a cheap and simple way of providing more noise, its not to increase performance. We do excellent full custom stainless systems from just £450 that will give you decent performance gains along with the sound and tips of your choice. Or we can simply build a smaller stainless back box with the sound and tips of your choice for £220. All our price's include fitting, Vat and lifetime warranty. We also offer 10% discount on full systems for forum users.

This is not to advertise our company but to show that when we hear these things that we try and sort them out with our customers. Fifal dropped us an email to let us know of the power loss figures on here. We are very grateful for the work we have received on this forum and wouldn't want any of you to think we are taking advantage of any of you. We have a rolling road next door to us so its likely that next time we have a back box delete on a Z4 we will do a before an after run and let you guys know the results.

We hope for future custom from the forum and would like to apologise for any problems caused, We would like to think we are one of the best system makers in the country and when ever we hear things like this we like to try and get in contact and understand the situation.

Thanks for your time
Ross Parker
 
There has been a few butt dyno reports that suggest power loss. I would say that my butt dyno feels like its lost a little off mid range. Initial pull feels good and so does top end. Just sometimes feels like the noise is blowing away the power a little.

Lets face it, its a cheap and cheerful (if you like the noise) mod. It makes the car sound a lot more meaningful and fruity. I personally like the sound and the cracks, pops and bangs it makes. Pop in a fresh tank of Vpower fuel when the engines warm and you can get it pop/bang pretty loud at times.

The loss of back pressure on a N/A engine is highly possible. Something a remap could probably sort but with the cost of that you might as well purchase a proper exhaust set up.

Ill be changing my exhaust in coming months so ill see what my butt dynos saying then and report back
 
I will try my best next time there is a Z4 in for any work to do a before and after dyno run and let you know the results. I love the sound the straight pipe make but then im only 25 :)
 
NathanZ4C said:
There has been a few butt dyno reports that suggest power loss. I would say that my butt dyno feels like its lost a little off mid range. Initial pull feels good and so does top end. Just sometimes feels like the noise is blowing away the power a little.

Lets face it, its a cheap and cheerful (if you like the noise) mod. It makes the car sound a lot more meaningful and fruity. I personally like the sound and the cracks, pops and bangs it makes. Pop in a fresh tank of Vpower fuel when the engines warm and you can get it pop/bang pretty loud at times.

The loss of back pressure on a N/A engine is highly possible. Something a remap could probably sort but with the cost of that you might as well purchase a proper exhaust set up.

Ill be changing my exhaust in coming months so ill see what my butt dynos saying then and report back
Click to expand...

Hi, do you have any videos of the exhaust note that you could share with us?

I'd love to hear the sound it makes as I'm interested in getting this done.

Many thanks!
 
Beetlegav said:
I've got a small video of mine

Click to expand...

OMFG!!!!

THAT SOUNDS INSANE!!! :o

Is that JUST a muffler/backbox delete or have you done anything else to your exhaust system?

And was that POPS AND BANGS I just heard????? :evil:

I would love to see more videos of your car! :thumbsup:

Do you have the M54 3.0i pre-facelift Z4 or si?

Cheers for sharing that with us! :thumbsup:
 
Yeah just backbox delete on the 3.0i m54 b30 engine.
It's so much more brutal than It sounds in the video :lol:
 
Also, back pressure is not a good thing. You want the pressure to be lower on the exhaust side, so that all of the "used" air is evacuated from the cylinder after it has fired. If there isn't much of a pressure differential, that used exhaust air won't be inclined to leave the cylinder after combustion, and thus fresh air won't replace it. If you can only exacuate 80% of the used air, your engine might as well be 20% smaller. The more of the used air you can push out of the cylinder after combustion, the more fresh air can come in on the intake stroke. "Back pressure" pushes back against the air trying to leave the cylinder.

There's a lot that goes into exhaust design. The most critical aspects are emissions equipment and the parts closest to the engine. Emissions equipment (catalytic converters) pose restriction to flow, and increase back pressure. The parts closest to the engine are important because they make the largest difference in how the air leaves the cylinders, when the air is hottest and traveling fastest. Further on down the line, it doesn't matter quite as much. A muffer is at the very end of the exhaust, which is why performance effects are marginal with any sort of muffler swap. It's all about sound at that point. Headers on the other hand offer huge performance benefits, due to the proximity to the engine and alteration of emissions equipment. That's why I would never cheap out on headers, but a muffler swap/delete is all personal preference for the noise you want the car to make.

So to summarize, if you want to do this mod, have at it. You won't lose power.
 
Beetlegav said:
Yeah just backbox delete on the 3.0i m54 b30 engine.
It's so much more brutal than It sounds in the video :lol:
Click to expand...

I could hear it before i could see it :P it did sound beefy tho , was quite impressed 8) unlike my neighbours :P
 
mr wilks said:
Beetlegav said:
Yeah just backbox delete on the 3.0i m54 b30 engine.
It's so much more brutal than It sounds in the video :lol:
Click to expand...

I could hear it before i could see it :P it did sound beefy tho , was quite impressed 8) unlike my neighbours :P
Click to expand...


Haha I piss my neighbours off actually, one on a completely different street tracked me down n threatened to call the police on me :lol:
All because I woke her poorly son at 4 in the afternoon! Could understand if it was at midnight! (I stick my car in 5th at night and idle down my street)
I just told her to ask politely or I'll purposely drop a cog everytime I go past her house :D

They hated my beetle too and that was standard :lol:
 
Beetlegav said:
mr wilks said:
Beetlegav said:
Yeah just backbox delete on the 3.0i m54 b30 engine.
It's so much more brutal than It sounds in the video :lol:
Click to expand...

I could hear it before i could see it :P it did sound beefy tho , was quite impressed 8) unlike my neighbours :P
Click to expand...


Haha I piss my neighbours off actually, one on a completely different street tracked me down n threatened to call the police on me :lol:
All because I woke her poorly son at 4 in the afternoon! Could understand if it was at midnight! (I stick my car in 5th at night and idle down my street)
I just told her to ask politely or I'll purposely drop a cog everytime I go past her house :D

They hated my beetle too and that was standard :lol:
Click to expand...


I've been in that situation in my 20's with a full race set up 1293 cooper s (late 60's) I suppose now I'm old I can understand why it got up their noses! I probably woke the whole neighbourhood up. :D

Good fun at the time tho! :thumbsup:
 
I have to agree about the muffler delete not losing much if any noticeable power. From the manifold down to the tips nothing is OEM on my 350z. When I first got my 350z it was basically straight piped and it seemed fine not in the least bit slow compared to Other 350z I have drove. i know what a stock 350z, a straight piped 350, and a highly modded 350z feels like and straight piped compared to a stock 350z is practically the same thing. So unless your racing your zed it isn't really a big deal for day to day use, aside from maybe a little drop in mpg.
 
Pokeybritches a very good summary. This is why I was very surprised to hear about power loss from back box delete. Its likely that said cars were down on power on the rollers due to age and mileage, and that possibly they didn't even hit quoted figures out of the factory anyway. Whats more important than back pressure in a system is velocity, how the gas flows through, this why OEM baffled silencer system are so restricive. As a general rule we run 2.5" bore on anything from 200bhp - 300bhp, anything above 300bhp should run 3" unless of course its a twin pipe system. There are obviously exceptions. For example we have seen gains on a 1.6 Vtec civic of 10bhp from just converting the downpipe back to 2.5", and also the 2.0 EP3 Type R gains of around 15bhp.
 
I have another theory on my loss of power too, I think they might have rollered it in the wrong gear.
If an e36 and an e46 made claimed power and gained yet I didn't. I think mine was done in the wrong gear.
 
Beetlegav said:
I have another theory on my loss of power too, I think they might have rollered it in the wrong gear.
If an e36 and an e46 made claimed power and gained yet I didn't. I think mine was done in the wrong gear.
Click to expand...

What gear did they use beetlegav?
 
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