[twinfan]

hi ventura

your work on this link http://www.triumphrat.net/twins-technical-talk/103145-modded-scram-dyno-results.html

looks great...if you still want to do any tests try aluminium velocity stacks on the original airbox...just throw out those rubber parts and close the rest with silicone or any rubberplate

because of the step in the stock rubberparts there is no good airflow and it causes interferences...throw out the difference plate between head and intakes and use 70mm long velocity stacks


look...here´s a pic on stock airbox but with fcr´s...scroll down and click on third and fourth pic:

http://www.classicbike-raisch.de/html/motor_vergaser.html



you will have to dremel a little bit on the diameter at the box to make them fit...but stock rubberparts will refit so that there are no gaps

there are two versions...50mm for the thrux and bonnie for better reving and torque at high revs...70mm for the scram because of more torque at low revs...i can go get them for you if you don´t find in UK

cheers


twinfan

 

[Ventura]

looks great...if you still want to do any tests try aluminium velocity stacks on the original airbox...just throw out those rubber parts and close the rest with silicone or any rubberplate

http://www.classicbike-raisch.de/html/motor_vergaser.html

Many thanks Twinfan for the info and the link.

What a great website!!
I just wish my understanding of German was better!!
But in the universal language of biking it mostly seems self explanitory.
I think!!?

You have a PM.


V.

 

[Gob-ny-geay]

hi ventura

looks great...if you still want to do any tests try aluminium velocity stacks on the original airbox...just throw out those rubber parts and close the rest with silicone or any rubberpla...
twinfan

Twinfan,

Very nice post. I enjoy this "out of the box" (or is it "in" the box) thinking.
I have done the exact same thing with Velocity Stacks, with excellent SOTP results. Sorry Ventura, no Dyno graph.

my source was www.Velocity-Of-Sound.com USD$29.00 ea. 54mm O.D. X 70mm long. Took ten days delivery, Australia to Illinois.

Slight difference - I fit mine INSIDE the rubber vibration isolators/connectors. The 54mm O.D. velocitystack slides into the rubber piece nice and tight, and yes, you need to "round" out the oval opening in the airbox to fit.


I also cut out the opposite end of the K&N replacement filter, added a 1/4" thick neoprene gasket, and then cut outan opemnong at the opposite end of the stock airbox. That done, it's a dual opening airbox (JohnyC originated this, and also tried the 790 Cam).

The airbox interior, after removing the snorkle and flow divertor, has TONS of plastic shelves, brackets, ribs, etc., that can ALL be removed safely, without compromising the strength, or integrity of the box.

All that done, the results are extremely satisfying. Very good pull from a standing start, and the noticable increased "roar" heard from inside the box tells me "something" is going on".

Total cost? My labor is always free, and the time spent (one full Saturday) was very enjoyable. Other than that, say $10 for dremel tool bits, and $68.00 for the two stack.

I have tons of photos on the airbox interior work, installation of the stacks, and other mods done to the much maligned airbox. Anyone interested just PM me.
Priceless.

More posts and threads like this Twinfan and Ventura, great stuff.

 

[twinfan]

???

how did you make it fit inside the stock rubberpart between airbox and carb? i tried it out first (because of 100% stock look) but i didn´t get it


i do like on the link i put in the last post...put some from the inside and a black rubberplate somme mm thick fixed with black silicone from outside to make it tight against water...with the sidepanels on nobody sees


cheers


twinfan

 

[Gob-ny-geay]

???

how did you make it fit inside the stock rubberpart between airbox and carb? i tried it out first (because of 100% stock look) but i didn´t get it

twinfan

I will PM you with photos tomorrow - I'm not at home today, travelling.

It's easy. If you look at the pictures of the Velocity stacks at Velocity-of-Sound.com, you will notice that they have full, radiussed over Bellmouth entries.

This entrance/bellmouth width on the 54mm stacks is just a little too wide, so you need to cut off about 4mm from each side, which isn't much, and still leaves plenty of radius.

Then trim off 10mm from the total length (fine tooth hacksaw and file/sandpaper works great).

Push the stack into the rubber piece, leaving about 20mm exposed. The first "cut-in" square of the airbox inside the opening determines how deep into the box you can go, and acts as a stop. Now although the Stack is a very tight fit in the rubber, it cannot slide forward or back, and is locked in solid. I put a few dabs of RTV Black silicone on just for further safety.

As you noted, the "oval" openings need to be filed out to slightly oversized round with a rat-tail file, which is very easy.

My next move is to design and fabricate much improved "intake" pipes, on both ends,to fit under the sidecovers, but be rigid palstic, not rubber like the snorkle, and non-restrictive to airflow. Thus far, I haven't had any issues with the two ends open, so no hurry. A few others have previously noted airflow problems with the single opening/snorkle removed while riding in severe wind, but it seems like a minority. It may depend on where you live(?).
Some areas are much windier than others, especially flat open plains, etc.

Anyway, I'll send you some digitals tomorrow early AM. Both approaches look like they work fine, obviously you are pleased with yours, just wanted to provide a possible alternate method.

Thanks.

 

[agro]

my source was www.Velocity-Of-Sound.com USD$29.00 ea. 54mm O.D. X 70mm long. Took ten days delivery, Australia to Illinois.

The airbox interior, after removing the snorkle and flow divertor, has TONS of plastic shelves, brackets, ribs, etc., that can ALL be removed safely, without compromising the strength, or integrity of the box.

G'day, have gutted airbox of all the plastic, but use the aussie unifilter replacement element, which has a foam endplate, not solid like the k&n and usa unifilter.

I am interested in your velocity stack mods, could you please post the stack part number that you purchased.

Will PM you for pics re; airbox mods and velocity stack mods..........maybe you can post them for other members?

Cheers..............Agro

 

[Gob-ny-geay]

Here's a few. Velocity Stack Part # is VS50_70, which refers to the 50mm ID X 70 MM length. Aluminum (or aluminium to you Aussies) is 2mm thick, therefore the ID at the funnel is 54mm, which conveniently fits tightly inside the rubber connector.

I'll send 5 more picks in about 15 minutes, as 5 pics is the limit / post.

 

[Gob-ny-geay]

Here's 5 more. In this series, note the amount of "stuff" removed from the interior. If you are familiar with the stock box, you will see how much has been trimmed out.

Hope this inspires others to continue with the trials.

I've got about 50 more pics, so if you need more detail, let me know. Bike runs beautiful. Thanks.

 

[Gob-ny-geay]

Just for reference, here are pics of Air Cleaner Housing BEFORE modifications, and lastly, a pic of the ported and polished intake manifold. If you remove this carb to Cylinder head set-up, the rubber isolator, aluminum manifold, and phenolic spacer all have differing I.D.'s, and the aluminum has casting flash, ridges, etc. An hour or so spent with a Dremel cleans all this up nicely. Tip: Reassemble the three components, and screw a hex nut on the original bolt. Now take a Dremel with a flap wheel sander - 220 grit to start, and match all the I'D's while smoothing out the ridges and bumps. Have Fun!

 

[PieMan]

If there is any movement with the three components on the bolt, get the right size heatshrink and put some on the bolt to pad it out and to keep the components exactly in place.

Any smoothing after the carbs and before the valves should be 80 grit at most, to keep the petrol from globing and help with atomisation.

Gob, all that dremel work cleaning up the airbox, you've done a great job, but have you noticed any increased air flow?

 

[Gob-ny-geay]

Excellent point Pieman. My next experiment is with adding a second set of phenolic spacers for an additional 3/8" (9mm) plenum length. I'll look at bead blasting the interiors at that time. By the way, what a rip-off. $15.00 each for the spacers, and $7.00 each for the O-rings. Oh well, whatcha gonna do? Should be here next Monday.

To your question about airflow - note that I'va also had a 5-angle valve cut done, and a total "baffleectomy - as inspired by the guys at bonnevilleamerica.com (Propforward - i trust this is OK?). The trick is to cut a 1 1/4" Holesaw in half and weld either end to opposite ends of an 18" long 1" pipe. This way, you can get WAY down inside, and each quick drilling removes a 1 1/4" metal plug. Do this about 8 times, and the entire interior baffles are removed, instead of "swiss-cheesing". I can see very clearly through to the opposite end.

I currently run 42 pilots and 130 mains, 2.5 turns out on the air bleeds, no shims. I use a CO wand and Gas-a-just, left over from my MGB tuning days. Sorry, no Dyno graphs. Actually, you guys are wearing me down regarding the dyno stuff. I've made 3 calls thus far, and in my area (within 100 mile radius), no one does Triumph's, or rejets. A hex on Harley Dealers, who have dyno's but turn their noses up at Triumph's. These are EFI guys. I'll keep trying, but I can tell you that the bike runs fantastic, starts immediately on choke in very cold weather (+10 degrees F), and I currently average around 52 MPG. I'm happy with it, which is what it's all about... right?

 

[propforward]

I'm happy with it, which is what it's all about... right?

Darn straight!

This is impressive work, and I am now thinking that before going any further on my own bike, it would make sense to clean up the intake ports as you have done.

Hmm. I do believe I suddenly have a project lined up for next weekend!

 

[PieMan]

I currently run 42 pilots and 130 mains, 2.5 turns out on the air bleeds, no shims.

So Gob, have I got this right? After doing the velocity stacks, cleaning up the inside of the airbox and opening up the other end of the airbox you are running 130 mains.

 

[blight]

Great post... I must say I have thought about doing this on my Thruxton. I have had lots of bikes over the years including doing all the wrenching on 'em.

My old CB750K four came with 4 OEM rubber stacks that were a slip fit into the airbox. Nice design, with the 736cc engine making 67hp at the crank at 8000 rpm...hmmm, similar rating the modern 865cc Triumph! Few people knew it, but the original CB750 was a torquey engine, being under-square, that is the stroke was longer than the bore size! You didn't have to zing it to redline to make good power. I still love riding this 36 year old bike even today.

Also, my 1991 Honda VFR750 came with 4 beautiful spun aluminum velocity stacks in a cool nested V pattern inside the airbox. Below are a couple of pics to illustrate how they looked on these bikes.

I noticed a little rubber rot on the airbox rubbers on my Thrux, and started thinking about a similar velocity stack into the airbox idea a few weeks ago.

Thanks for a great thread and the excellent pics!!

Cheers,
BLIGHT

 

[Gob-ny-geay]

Blight - such kind words! As you know, this Velocity Stack stuff is nothing new, nor is the Stacks in the airbox idea new, so I'm hesitant to take any credit. Racers around here have been doing this for many, many years.

My intent has always been to raise the VE to the highest level, and any gains experienced in doing so will be efficiency, economy, smoother running, etc. If I happen to get more power, well so be it, that's fine too.

I probably do need a dyno and A/F sorting, as I've had 125's, now trying 130's and I still have excess "blueing" of the pipes, but as you can see good fuel economy as well. That tells me I'm most likely at the lean end, but she does run super nice.

The NARK's are great, no arguement there, but I thought it would be interesting to try something different, as I'm inclined to do. If ya' like it, great, if not, that's OK too. Whatever floats yer boat!

Nod's to Ventura and JohnyC for inspiration, but also to the numerous nay-sayers as well, to keep us sane!