Open ITBs "Velocity Stack " and the PCV system

[liam821]

liam821 Thankyou for the help! I'm in the middle of manual swapping my M3 so I'd like to do the velocity stack conversion while everything is already apart. So just to make sure I'm understanding correctly, I could install the velocity stacks and run in Alpha-N with external IAT without damaging the car? Just to get it up and running in the meantime before I get a tune in the near future.

I would literally only drive it from where you did the work straight to your tuner. I wouldn't drive around on Alpha-N without tuning, since the whole point of alpha-n is to use a set fuel table in the DME - it has no way of measuring airflow.

Personally, I'd never do it and would stick to using a MAP sensor with a MSS54HP ecu.

[MHoffmannM3]

liam821 Sounds good. Thankyou very much for the help!

[ivo2456]

Hey liam821 , thank you for the comprehensive guide.
It's been very useful in my research in preparation for putting velocity stacks on my car.
May I ask how you cut out the trumpets from the airbox?
I can't find any info on that online

[liam821]

Hey liam821 , thank you for the comprehensive guide.
It's been very useful in my research in preparation for putting velocity stacks on my car.
May I ask how you cut out the trumpets from the airbox?
I can't find any info on that online

They're a pain to remove. For the earlier boxes pre 10/2004 with the yellow trumpets, I was able to unscrew the backing on each trumpet and then pound them with a mallet and they popped out. They're just glued in. If they don't want to come loose you'll have to use a sawzaw/cutting tool of some sort. Basically, just destroy the box while being careful not to mess up the trumpets.

[9kracing]

I'm convinced there's a ton of power to be made by changing the ITBs, but I don't feel like being the guinea pig... especially since I'm supercharged.

I'm not sure using factory trumpets will be the move unfortunately. As far as I can tell, the factory ITBs are 52mm... which is pretty small for a motor of this size. I'd like to see some big throttle bodies with a properly tuned trumpet.

It goes to show you what happens when you use properly sized, well constructed, high quality ITB's. Most people think you can just throw a set of ITb's on a car and it'll make power. In this case, proper size and design is everything.

https://honda-tech.com/forums/all-motor-naturally-aspirated-44/profunction-kinsler-present-epic-all-motor-bseries-manifold-testing-2841539/

[liam821]

I've also printed a set of the adapter that yot've designed, although I put the ///M logo in the middle 😀
I know you used PETG for yours and I've used it for mine, but how did yours hold up in the long run?

ha! You're welcome. PETG has been holding up great. I have many thousands of miles on them now. PETG has a temperature rating of around 80C degrees, which is hotter than the intake manifold gets. ABS would be better but it's toxic to print and harder to print without warping and really only good for another 20c.

I've never tried nylon or some of the fancy carbon nylons they now have available. But those might even be a better material to use.

I'm convinced there's a ton of power to be made by changing the ITBs, but I don't feel like being the guinea pig... especially since I'm supercharged.

I'm not sure using factory trumpets will be the move unfortunately. As far as I can tell, the factory ITBs are 52mm... which is pretty small for a motor of this size. I'd like to see some big throttle bodies with a properly tuned trumpet.

https://honda-tech.com/forums/all-mo...sting-2841539/

Very interesting. I'd love to 3d model a bunch of different-sized trumpets and test back-to-back on the dyno. I'd imagine you're correct and a lot of power is to be found in tailoring the trumpet to the setup. Especially with larger cams that breathe more at high rpms. And yeah, we'd might need a larger throttle body setup. Does anybody have a set of Dinan ITBs lying around I could borrow? . Still might be interesting to see what different sized trumpets do to the powerband.

A good buddy of mine is getting a dyno (at least I hope!) and I'm sure he'd let me borrow it for a day. If it happens I'll be sure to make a post about it.

[digger]

I'm convinced there's a ton of power to be made by changing the ITBs, but I don't feel like being the guinea pig... especially since I'm supercharged.

I'm not sure using factory trumpets will be the move unfortunately. As far as I can tell, the factory ITBs are 52mm... which is pretty small for a motor of this size. I'd like to see some big throttle bodies with a properly tuned trumpet.

https://honda-tech.com/forums/all-mo...sting-2841539/

People have tested bigger throttles and there doesn’t seem to be tons of gains, some builds could show some incremental gains.

The factory throttles are 50mm and unless you address the most restrictive part ie Inlet valve and ports you’re fixing in on the wrong area. 2x35mm valves are equivalent to 43mm with 88% throats

You could optimise trumpet length to bias induction wave tuning towards top end power at expense of some midrange but that’s for race only imo. The starting point is pretty good already it’s not a crappy m54/52 inlet system

with FI treat inlet as a engine equivalent to no boost I.e with 600whp at 1bar is 300whp NA so Inlet tuning is not massively different as boost is density not velocity