(T) DIY Bespoke/Custom MJet Induction kit

Quick query, before i take everything apart to measure.

Does anyone have the outer diameter of the MAF and Turbo Inlet? Bit rainy so not fancying going outdoor to find out.

Looking on alfa owner they are saying that the inlet is 50mm OD on the GT1749MV.

Planning on building some sort of cheap custom induction, nothing fancy I think and purely for the noise.

OK so thanks to Adam (adamcot) who's lent me his standard airbox gear. I've now got the measurements and have ordered the parts I need.

Diagram below for anyone else who may like to try, including sizes parts and prices.


Parts from Auto Performance Silicone Hoses http://www.auto-performance.co.uk/ - Silver is Alloy, Blue is Silicone, Black is a standard part of the system and I have a lovely pink turbo.

Filter arrived today ahead of the rest of the bits (Love Royal Mail Muchly) sadly it was silver not gold, so me being me popped it onto the MAF but not before taking some before airmass readings.


Sounds totally amazing if a little loud (Linz hates the sound) but hopefully that will quieten when the pipework arrives and I can redirect the filter into some nice cold air down in the bumper.

Graph shows a significant increase with the cone onto the MAF and that on average there is almost a 13% increase in airflow.

Some of the After data points are all over the place as I think i became a little lead footed due to the sound, but all of the outliers are filtered out of the final stats below.



Sorry for being all scientifical but if I'm doing it then I'm proving its worthwhile.

I'll update this over the weekend once pipework is in place (Assuming it arrives) and maybe some stats from a GSR too. Which undoubtably will be better as the insides of it are 100% smooth and its not been designed by me

Good science sir

The pig is placing the AFM without killing the AFM and/or the rear of the head light.

Make sure you place it all correctly before cutting the hoses bits etc or it will get very expensive. And I do know how painful it can get.

Thanks Peter , measure twice, measure again? Cut.

Wrong.!!!!

Measure twice, put first bend in place, measure again, close eyes and cut and don't scream when wromng. lol.

Then add next piece etc.

Although it doesn't look it, it is quite tight.

Try positioning the AFM first and do not go for the first option. Take a good look before you start.

Rather shave off bit by bit and have lots of patience. It will be the cheapest way to do it.

Start from the filter end and work backwards? or do you mean get the AFM into a position where its safe and the wire reaches then work away from it in both directions?

The two 45 degree angle's to get over the chassis leg are going to be a bitch I think.

The whole thing is a bitch on the m-jet.

Start with positioning the AFM because it is the most vulnerable part. You need to make provisions that it doesnot hit any other part under hard acceleration (bear in mind that engine mounts get weaker) and that no oil from breather or turbo can flow against airflow direction when engine is switched off, which could do damage the AFM.

BTW, welcome to the headaches of air intake design.

And this is only the beginning of the problem.

Haha, thanks I'm sure ill let you know how I get on. Assuming royal mail ever deliver the rest of the parts!!!

You'll know when I've failed too when you get an order for a GSR

haha i love you for this thread, deffinately having a go myself!

So today I decided to remake the after graph as yesterday due to lead foot whooshy noise syndrome the readings were all over the place.

I also worked out why as the scan tool im using can only poll the ECU for a value at a time, and only a certain amount of times per second.

What's been done today is a smooth acceleration up to 3000 rpm over 30 seconds, back down,up and down again.

The result is a much cleaner more accurate curve with even more gains shown.





Heres what its currently looking like under my bonnet, and hopefully that filter will fit down into the bumper somehow.

so is that currently just a cone filter on the standard induction hosing then?

Yep, as Royal mail were given 3 boxes, only 1 has so far turned up!!! I couldn't resist not poping it on for a bit as I'm probably only doing a few short drives over the weekend.

I noticed yesterday when we went to the park near where i work (30 mins each way) that once it started to get hot hot under the bonnet then acceleration became difficult.

Intake temp readings when I got home were 10/15 degrees more than normal as its just sucking up warm air from the top of the engine bay.

Ahhh.... I see! Prob just an aftermarket pannel filter for me then

Me again Royal Mail still failed to deliver my parts so I'm hoping they turn up soon.

I did however manage to get some airflow readings from a GSR on adamcot's car as he was over my way for the weekend.

Before I post the graph, and just to set things straight you need to remember these facts;

-> Adams filter has now done 20k and looking at punto_matts over a simmilar distance will now likely be covered in mud, dust etc etc.
-> My intake is currently far longer than the GSR so Turbo spool up though faster than standard will not be anywhere near as good as the GSR.
-> My intake is also high in the engine bay so after a long drive means air temp is 20C higher than with the GSR and due to the lack of insulation from the plastic airbox is ever so slightly higher than with the standard airbox.
-> The path to the turbo taken by the remainder of the standard system is also not as free flowing as the GSR or the intake I will have at the end of all this messing.
-> The recording method to assess MAF airflow and RPM is not 100% accurate due to the refresh rate of both sensors and the amount of reads per second that can be performed over ODB2.

All that said, the below shows the GSR outperforming my new Intake by a few percent and way outperforming the standard setup with what appears to be an emphasis toward an even higher airflow further up the RPM range.



I think this can also be seen clearly in Adams before and after GSR graphs from the Red Dot rollers below, where an increase in Torque is seen getting progressively more as RPM rises and continuing longer.