Larger Weber Airbox in a Plus 2

[stugilmour]

Hoping to draw together information on airbox fitment in the Plus 2. Any replies appreciated. Pictures, dimensions, and fitting success or hassles welcome.

I have included some options I have looked at below. Have also got a bunch of help from other List members that have installed aftermarket airboxes, but so far only Elan experience. Although I have fairly specific

I need an airbox for my new Weber Tall Block project. I want to go airbox and a nose mounted filter to reduce intake noise. I would prefer an aftermarket style airbox with full width to number four cylinder rather than the stock taper shape. I have none of the stock parts as my Stromberg engine used an ITG flat foam filter, and the donor engine was without intake hardware.

My particular car is a Federal Plus 2, LHD, Spyder frame, hood bulge. I have read a bunch of great threads on different airbox configurations. Most fitment issues seem to relate to early Elans; haven't found Plus 2 experience.

The best candidate I have found is the Tony Thompson Racing kit. QED said they get their offering from TTR. I am waiting for a few measurements, which I will post.

http://qedmotorsport.co.uk/qed-shop/lot ... ith-filter

http://shop.tonythompsonracing.co.uk/tt ... -249-p.asp

The Tony Thompson Kit includes the remote air filter, trunking, Weber backplate and Constant width airbox cover. Not sure yet for exact dimensions, but believe it is approximately 15" long at the backplate, 4" wide, and 4 5/8" deep.

The QED kit, which is sourced from TTR and assumed identical. This shows the backplate. Note the vertical offset is expected to raise the airbox centre line about 3/4" higher than the Weber carb inlet centre line.

Some of the alternatives I have looked at.....

Ray at RD Enterprises has this stock style setup

http://rdent.com

The RD Enterprises Weber backplate. Appears to include an arm to assist with the throttle cable connection. This one is 14 7/8" long and 4 5/8" high. The offset places the top of the airbox 3" above the carb inlet centre line.

img_0367.jpg (23.1 KiB) Viewed 6009 times

This is the airbox Ray offers. When mounted on the Weber backplate it tapers from 4" wide to 2 3/4" wide at the firewall end.

img_0369.jpg (12.79 KiB) Viewed 6009 times

Burton Power has some Pipercross options. Check out page 75 of their current catalog for the detailed callup numbers Although Pipercross is probably better known for foam style filters mounted directly on the carb inlets, they offer a promising airbox option that attaches to their Weber backplate. The same backplate is used for the Lotus TC, BDA, and Ford Crossflow.

https://view.publitas.com/burtonpower/2 ... es/page/75

Burton Power supplied Pipercross KK600 carburettor base plate: 2xDCOE - Ford X/Flow & BDA. Note the horizontal offset that moves the mounted airbox or filter forward. This is potentially problematic for the Plus 2 as the front filter mounting tab will likely foul the bonnet. The fitment could possibly be mitigated by installling the backplate upside down, but a blank plate would have to be custom cut. I did see an archived thread that an Elan owner successfully fit this backplate by bending the front tab to a horizontal position. I believe he was using a Pipercross foam filter, which I think have a metal frame. I don't think this approach would work with the airbox attachment.

The Burton Power supplied Pipercross air box with intake pipe & filter. 75mm RH inlet (when viewed from front of carbs). I understand this can be set up using an included small conical filter in the airbox horn, or attaching a suitable filter to the included trunking. The airbox is 22 4/4" long (with the air horn), and approx. 7 1/2" high including the top and bottom filter mounting tabs. I think this exceeds the practical room available in the Plus 2, but would be interesting to see if anyone tried.

Pipercross airbox dimensions for reference. Note the front mounting tab is located fairly far down the curved portion of the backplate, which will assist with bonnet clearance. This is better than the ITG filter I used with my Stromberg head, but I think it would be touch and go in a Plus 2. Any experience out there?

img_0372.gif (11.15 KiB) Viewed 6009 times

Later this week I am going to be talking with Sean at Spyder about some other stuff. I understand they have an airbox they use, not sure if it is one of the commonly available ones or something of their own? I didn't find anything on the web site.


Sorry for the length. Hopefully saves others some typing!

Does anyone have experience with these or other aftermarket airboxes or filters in the Plus 2? Would be great to get some anicdotes, experience, pictures, dimensions, yarns, etc.

Stu

[jono]

Stu,

I made my own by extending the existing one - seems to work really well and was satisfying to do.

I had a Cliveyboy filter in nose type intake kit fitted but when at the rolling road it was running really rich at high rpm. We tried no filter hose and the issue disappeared so I have fitted a K&N cone filter direct to the air box - a little noisier but not significantly so and the engine seems to rev much better.

I intend to make up a alloy box/shield to cut out some of the engine bay heat so that the cone pulls in cooler air but not got around to it yet. In the meantime it seems to work well.

Jon

[jono]

Stu.. a bit of related discussion here

lotus-twincam-f39/filters-trunking-and-remote-filter-t36863-15.html

Jon

[stugilmour]

Thanks for the experience and link Jon. I have taken the liberty of re-posting your excellent picture of your final setup with the body and bonnet in place.

A picture of Jon's setup from the linked thread. Shows the clearance above the airbox very well. Very tidy K&N installation with no issue passing the trunking through the radiator mount area.

Do you have a K&N filter P/N call-up to hand? As you are running a modified stock airbox, can you confirm the nominal trunking diameter? I expect it is 3 1/2" or 90 mm, but that is just based on the description in Ray's reproduction offering shown above.

Another general question that would help a lot. Does anyone know the resulting vertical difference between the carb inlet centre lines on the Weber / Dellorto and the Stromberg heads? At a wild assed guess my SU's on a Federal Stromberg head were about 1" higher than an Omnitech head converted to Weber fitment. This was just from looking at the two engines on John McCoy's loading dock; I shoulda measured them when I had the chance! Rohan has posted before that the Omnitech Weber heads retain the same dimensions as a stock Lotus head; heaven knows if my SU's differ materially from Strombergs.

For reference, here are a few pictures of my ITG / SU setup. I think it uses the ITG JC40 filter and backplate for small Twin carb setups. I sourced mine from Ray at RD, and he still stocks them. He mentioned he has Weber backplates, but I did not enquire if the carb inlet centre line is angled downward toward the front.

Stu's Plus 2 Federal with SU's installed on a Stromberg head. The ITG pancake style filter uses a custom cut ITG blank backplate. The backplate was inverted to move the ~1" filter mounting tabs to the bottom edge of the filter. The ITG backplate differs from the Pipercross shown above as it only has three tabs on what is supposed to be the top side. I originally cut the backplate intending to install it right side up, but the front tab fouled the bonnet. Now being aware of the issue I could have done a better job of it, and maybe fitted it right side up. The clearance to the fender is pretty good though as the tabs clear OK.

Another view of Stu's SU setup. May be able to see minor rubbing of the front of the ITG filter, which indicates how tight the bonnet clearance is on the Federal Stromberg head. Unfortunately the picture angle is a bit high to provide a clear comparison to Jon's Weber head shown above.

I think this is the ITG filter I used. They seem to come in two thicknesses. Note the filter mounting tabs are higher on the curved portion of the backplate than the similar Pipercross backplate shown in the earlier post.

This link to an ITG site mentions the Lotus requires a bonnet bulge and seems to indicate it is installed angled. I assume this means the custom cut backplate angles the front of the filter downward.

http://itgairfilters.com/uploaded/pdf/1 ... 6-jc40.pdf

Stu

[stugilmour]

This post outlines another supplier I looked at, Kelvedon. They seem to offer two products.

This link is to a kit with large fabricated aluminum air box, trunking, filter, and clamps

The Kelvedon Lightweight Aluminium Cold Air Box Kit, P/N RACEAB01KIT.

http://www.kelsport.net/parts/product_d ... ctionID=66

I don't have dimensions on this one yet, but appears slightly wider than the TTR / QED offering. A similar vertical offset should clear the Plus 2 fender. I can't see from the product picture how the box is opened or how many bolts it has.

They also offer a setup that looks closer to stock. Not definitive because of the angle the picture is taken, but this looks very similar to the stock reproduction piece offered by RD Enterprises. Anyone used this one? It it a tapered airbox?

http://www.kelsport.net/parts/product_d ... ctionID=66

http://www.kelsport.net/parts/product_d ... ctionID=66

Kelvedon Weber backplate. P/N RACEABBP. Has arm for the carb linkage and the nipple for the cam cover vent. Similar vertical offset to raise the airbox height.

The Kelvedon airbox that fits the Weber backplate above. P/N RACEABC. Has a stock look. I can't tell if it has a taper front to back.

This is another picture of The RD Enterprises Weber backplate. The size of the vent ports and backplate dimples look similar to the Kelvedon backplate.

img_0381.jpg (27.23 KiB) Viewed 5926 times

Stu

[Davidb]

More discussion here:
lotus-twincam-f39/full-depth-air-box-cover-t37276.html

Unfortunately Dave is not responding to my emails--anyone know if he is still making these?

[stugilmour]

Another excellent thread Dave.

As the original eBay UK listing for Dave's great looking airbox will probably go away, I have posted some info from it here. Read the linked thread though, as it seems some guys have fit the box OK and some have not. Not clear if the product is presently available, but it looks perfect for the Plus 2, and I assume will fit the Weber backplate supplied by RD Enterprises or Kelvedon shown above. I believe the same backplate is available from SJ Sportscars, and perhaps Paul Matty based on the linked thread.

To fit Classic Elans using Weber or Dellorto carbs. This airbox is full depth along its entire length which gives the benefit of increased clearance for number three and four cylinder inlet trumpets which have marginal clearance to say the least. This gives number four cylinder a fighting chance to breathe properly as not only has it to cope with too little clearance but also the crankcase breather located next to it. This airbox is derived from the original Lotus airbox and does not look out of place under the bonnet of any classic Elan. It is supplied with a new fitting kit to ensure hassle free fitting. The interior of the airbox has an easy clean finish to prevent fuel and oil soaking into the GRP as happens on the original. It will fit all later models that use the square ended backplates. For more info you can call or text me on xxxxxxxxxxx

Very nice looking GRP airbox. Need to source a square cornered backplate separately. Held on with the three supplied bolts.

The inside of Dave's airbox. Shows the attachment bolts and the cleanable interior surface.

Stu

[stugilmour]

Another detail I came across looking at archived threads is sealing the airbox to the backplate. Without getting bogged down, there are several different airboxes and seals. This thread covers several ideas, ranging from a Toyota cork gasket to various split seal replacements...

lotus-carbs-f40/airbox-seal-t13389.html?sid=970330f80dd8ff887f5eb1cfb2e346f5A

Stu

[1owner69Elan]

I faced a similar issue when converting from a Stromberg to Weber head. I had no Weber compatible backplate or air box.

The TTR option was only suitable for Weber 45's as I was told several times by TTR themselves. They said they had no solution for 40's. I have purchased many, many parts from TTR but surprisingly they could not help on this. I kept trying to convince them to sell the air box to me and they insisted on not doing so.

I then obtained a stock backplate and S4/Sprint air box (square back) end. But, this configuration robbed 7 hp as measured on the dyno. Not enough volume.

I then had a non-restrictive large air box and backplate fabricated that is modeled on a 26r version. Shown below. It's coupled to a K&N filter in the nose.

[stugilmour]

Very nice!

Is it possible to get an airbox cover made by the supplier? If the supplier is on the forum, please PM me if you can supply.

Very interesting on the 45's vs 40's. Was that a while ago? Reason I ask is the current TTR listing says for either. One of the questions I submitted was whether I had to specify carb size in the order or whether it was a kind of "one size fits none" deal. Haven't heard back, and assuming they will reply when they have an example in stock so they can provide the measurements. All that said, could be that the rep I am communicating with is not aware of the carb size issue yet.

TTREA 001
AIR FILTER,PIPE,AIRBOX BACKPLATE & AIRBOX COVER,COMPLETE KIT FOR TWIN 40 & 45 WEBER (CARBURETTORS MAY NEED REJETTING ON DYNO/ROLLING ROAD TO OPTIMISE)

Stu

[1owner69Elan]

The TTR air box discussion was a year ago. The listing was the same indicating ok for 40's. But, as I said, they said not suitable. Stuart or Tony at TTR can confirm if the situation has changed.

[JimE]

Standard Lotus.

[Certified Lotus]

I don't know about a plus two, but in my "quest" to find a larger weber air box for my 64 Elan S1 I've collected almost every type if air box you can imagine. By the way, none of the larger air boxes fit an S1 as the front intake is at the wrong angle and fouls the lip of the bonnet so it wont close. I am in hope of a custom made one being built for me just for S1 model cars. Will know in another month.

In the mean time, here are the various air boxes, which are all for sale (although I will need to look up all my receipts to find out what I actually paid for them) Update 2/22/2017 the first airbox (QED) is sold.

[Certified Lotus]

Yes, there are more:

[ElanDNA]

I don't know about a plus two, but in my "quest" to find a larger weber air box for my 64 Elan S1 I've collected almost every type if air box you can imagine. By the way, none of the larger air boxes fit an S1 as the front intake is at the wrong angle and fouls the lip of the bonnet so it wont close. I am in hope of a custom made one being built for me just for S1 model cars. Will know in another month.

Hi
I had the same trouble. I make myself a box. As basis a jtg filter with 100mm internal height.