My take on a Mr.5 intake

pbondar

Sergeant
May 30, 2020
440
255
0
A few words and pictures on my version of what is known as the Mr.5 airbox modification for N54 engines as in the 35i/35is.

A bit of history for those not au fait with this matter…Mr.5 was a member of a US based E90 forum who proposed an alternative option for addressing the issue of limited airflow when a N54 engine is tuned.

Many folks went down the route of two dual cone intakes, each one sitting on the end of the disconnected turbo pipe inkers after the stock airbox was removed. The counter arguments to this are the much poorer filtration of the DCIs and the induction noise they create…In addition there were arguments about heat fade caused by sucking in hot air in the engine bay.

Mr.5 suggested retaining the stock airbox and filter but adding an additional air inlet post filters to the interior plenum chamber. Subsequently he and many others came up with various interpretations of this design.

Here’s my version made out of 50mm waste pipe fittings plus a Pipercross Viper aftermarket generic inlet / filter kit.

I’ve done a blended intake on the inside of the plenum chamber, most designs I’ve seen just terminate in a hole in the side of the plenum chamber.

In the end the flexible pipe and lovely aluminium inlet were redundant as there was not enough space to add those..

This is fitted to a RHD 35is..not sure if it would work on a LHD.

Off to the dyno next week to see what impacts it has.

Previous experiments on E89 air boxes showed a small improvement in power and torque ..on a N20..4 BHP in 300…on a N54 6 BHP in 400 and 10 BHP in 500 by removing the airbox lid and / or filter parts..never tried DCIs but the dyno guys rated the impact broadly similar to an unrestricted airbox ..ie no lid ..

One of the great unknowns with all these things is not just how restricted or not certain parts of the system are but how these things interact as a function of rpm and load..an area known as fluid dynamics..for mere mortals the only way is to suck it and see..I’ll report back on the dyno results…
 

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studio54

Specialist
Dec 20, 2021
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Nice, I always wanted to make my Mr5 intake too. Often looking locals ads for used airbox to make my own.

Looking forward your HP results next week.

Just one question, why did you keep the inner pipe section (like inside the airbox) ? doesn't it perturbate the airflow ?
 

pbondar

Sergeant
May 30, 2020
440
255
0
Nice, I always wanted to make my Mr5 intake too. Often looking locals ads for used airbox to make my own.

Looking forward your HP results next week.

Just one question, why did you keep the inner pipe section (like inside the airbox) ? doesn't it perturbate the airflow ?
The 90 degree turn in the inner plenum chamber is a hunch that blending the two air flows is better than allowing one to hit the other at right angles …every one has done it that way..thought I’d try an alternative..sadly I’ve glued the assembly together so short of taking the airbox off and sawing the 90 turn off I can’t do a back to back..let’s see what happens on Wednesday…
 

pbondar

Sergeant
May 30, 2020
440
255
0
How about a Y pipe in the plenum.

Flow hates 90deg turns
Due to the width of the inter plenum chamber the options were either a single 90 turn or a single 45 turn or just straight in..

I realise a fully blended flow would be great but using stock waste pipes my options are limited.

If I went from 50mm ID to 40mm ID it would offer more flexibility but then is 40mm with more tailoring rather than my 50mm 90 turn?

Lets see how it works…maybe revisit it again after dyno day..
 
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SlowE93

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Jul 2, 2017
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Just a plane ticket away !
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E93
A few words and pictures on my version of what is known as the Mr.5 airbox modification for N54 engines as in the 35i/35is.

A bit of history for those not au fait with this matter…Mr.5 was a member of a US based E90 forum who proposed an alternative option for addressing the issue of limited airflow when a N54 engine is tuned.

Many folks went down the route of two dual cone intakes, each one sitting on the end of the disconnected turbo pipe inkers after the stock airbox was removed. The counter arguments to this are the much poorer filtration of the DCIs and the induction noise they create…In addition there were arguments about heat fade caused by sucking in hot air in the engine bay.

Mr.5 suggested retaining the stock airbox and filter but adding an additional air inlet post filters to the interior plenum chamber. Subsequently he and many others came up with various interpretations of this design.

Here’s my version made out of 50mm waste pipe fittings plus a Pipercross Viper aftermarket generic inlet / filter kit.

I’ve done a blended intake on the inside of the plenum chamber, most designs I’ve seen just terminate in a hole in the side of the plenum chamber.

In the end the flexible pipe and lovely aluminium inlet were redundant as there was not enough space to add those..

This is fitted to a RHD 35is..not sure if it would work on a LHD.

Off to the dyno next week to see what impacts it has.

Previous experiments on E89 air boxes showed a small improvement in power and torque ..on a N20..4 BHP in 300…on a N54 6 BHP in 400 and 10 BHP in 500 by removing the airbox lid and / or filter parts..never tried DCIs but the dyno guys rated the impact broadly similar to an unrestricted airbox ..ie no lid ..

One of the great unknowns with all these things is not just how restricted or not certain parts of the system are but how these things interact as a function of rpm and load..an area known as fluid dynamics..for mere mortals the only way is to suck it and see..I’ll report back on the dyno results…
I have been running similar to this for years. Zero issues
 

pbondar

Sergeant
May 30, 2020
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255
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So the results are in…

On the same tune V6…we made 472 BHP and 657nm with stock airbox and paper filter

With open airbox ie no filter but closed lid it made 501bhp and 681nm

With my Mr.5 waste pipe plumbing and Pipercross cone filter it made 526 BHP and 688 nm with paperfilter in main housing
 

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wheela

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Jun 4, 2021
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So mr5 made more than open air box with no filter??? If have thought mr5 would have landed somewhere between stock and the open airbox with no filter, do you think these results are correct?

Any thoughts for the great results? Maybe some beneficial resonant tuning effect at certain rpm's from the mr5 plumbing that isn't present with open air box🤷‍♂️
 

pbondar

Sergeant
May 30, 2020
440
255
0
So mr5 made more than open air box with no filter??? If have thought mr5 would have landed somewhere between stock and the open airbox with no filter, do you think these results are correct?

Any thoughts for the great results? Maybe some beneficial resonant tuning effect at certain rpm's from the mr5 plumbing that isn't present with open air box🤷‍♂️
Yup we were (or my dyno guy) surprised ..did over 20 runs today with various swaps ..filters, tuned ..same dyno I’ve used dozens of times so hard to see it as not bona fide…..

As previously discussed there’s more than just ‘holes’ to this…my hunch about blending the Mr.5 air inlet into the mouth of the turbo inlet pipes seems to have worked..

Definitely strange things happen mid range between the pipercross panel filter and the stock air filter with quite a bit more torque present there …saw the same effect with no filter in place in the airbox

Seat of the butt dyno also felt very strong when we were data logging the last tunes with the Mr.5 mod…previously on my private test strip a 3 rd gear pull was just about it before running out of room..now I can get a 4th gear pull in the same distance..
 

studio54

Specialist
Dec 20, 2021
69
31
0
Dyno results are impressive ! 👍

What do you mean by V6 tune? I guess it's a custom tune, not MHD V6 😀

The 90° turn inside the plenum chamber seems to be benefical finally.
And after watching your pictures again, it was probably a good idea too to point it to the rear inlet like you did. The rear inlet need probably more fresh air than the front inlet.
 

pbondar

Sergeant
May 30, 2020
440
255
0
Dyno results are impressive ! 👍

What do you mean by V6 tune? I guess it's a custom tune, not MHD V6 😀

The 90° turn inside the plenum chamber seems to be benefical finally.
And after watching your pictures again, it was probably a good idea too to point it to the rear inlet like you did. The rear inlet need probably more fresh air than the front inlet.
Yes V6 is our internal numbering methodology…confusingly we started at 0.1….V1 was the first possible candidate for use rather than testing..it just happened that V6 was the only one dyno’d in addition to data logging ..until today when we dyno’d v12 and v13+

in an ideal world you’d spend more time experimenting with angles/directions etc but I took an intuitive decision on it based on other fluid dynamics I’ve studied..it didn’t make sense to have two air flows hit each other head on..obviously the flow from the main filter is fixed..so to deflect the other flow ideally in a merge was logical..compounding this are standing waves and resonance effects which are very complicated to model..

As it is it surprised all…my tuner based on this suggested we could go for 600bhp but we decided for going to the take away on a Friday night it’s sufficient…
 

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