Lotus Elan

Air box Elan S4 with weber

PostPost by: syrius » Wed Nov 02, 2011 6:52 am

Hi All

When I install the standart air box in my Elan S4 , my engine dont run properly . :cry:
I would like to exchange by a bigger air box .Have you somes epxeriences about this modification?
I found the tony thompson racing air box but the cost is 265 ?

thanks in advance for your help

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PostPost by: rgh0 » Wed Nov 02, 2011 9:51 am

The engine should run fine with the standard airbox - you have something else wrong or has been changed if it does not. Do you still have the original trumpets or have longer ones been fitted?

The standard airbox costs a couple of horsepower in a race engine as it limits flow a little to the rear intake which is why TTR offers a deeper airbox but the effect is to small to worry about on a road engine.

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PostPost by: syrius » Wed Nov 02, 2011 10:03 am

the trumpets is more longer and the cylinder head is an original for strombergs , but modified to adapt the Webers
that's means I have less distance between air box and internal wing.
The engine is modified by "Kampena motor " in USA .

Some body have a picture of T T air box installed ?

regards
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PostPost by: rgh0 » Wed Nov 02, 2011 10:51 am

syrius wrote:the trumpets is more longer and the cylinder head is an original for strombergs , but modified to adapt the Webers
that's means I have less distance between air box and internal wing.
The engine is modified by "Kampena motor " in USA .

Some body have a picture of T T air box installed ?

regards
Serge


I presume from what you say is you have the bolt on intake manifold conversion done by Omnitech to convert Stromberg heads to Weber heads. The length of this manifold is identical to the orginal cast in place weber head manifold. If you have longer trumpets than standard then the engine will not run properly with the standard airbox as the clearance between the trumpets and the airbox cover will be to small.

The larger TTR airbox should fit just between the carbs and the engine bay wall but you should not need it if you revert to the standard trumpets

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PostPost by: ericbushby » Wed Nov 02, 2011 11:22 am

Hello Rohan
As a side issue do you know the length of the original trumpets as I intend to fit an original type air box to my S3 with webers. It has K an N filters at the moment but many things have been changed before my time and I am trying to improve and correct as I work on it.
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PostPost by: ardee_selby » Wed Nov 02, 2011 11:30 am

rgh0 wrote:The standard airbox costs a couple of horsepower in a race engine as it limits flow a little to the rear intake cheers Rohan


As bought my S3 (with rounded / tapered airbox) had a shorter trumpet installed on the rear intake, presumably to offset restricted flow. But what else would it have done?

Cheers - Richard
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PostPost by: elansprint71 » Wed Nov 02, 2011 2:35 pm

From the photo it looks like the trumpets fitted to Serge's car are the type where the flared end "turns back on itself" (if that makes any sense), from what I've read in carburation theory books these give a better airflow than the more usual trumpet type. However, these will be a problem inside the standard airbox if they are too long.

Burton Power in the UK stock several different lengths of trumpet.

http://www.burtonpower.com/catalogsearch/result/index/?p=2&q=weber+trumpet
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PostPost by: syrius » Wed Nov 02, 2011 4:18 pm

Trumpets leng = 60 mm
I think ist too long when I install the original air box .

2 ways :
1/ exchange the trumpet by shorter
2/ exchange air box by TTR version

May be the fisrt one is less expensive , but I need to modify somethink on Weber ?

Thanks for your help

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PostPost by: ardee_selby » Wed Nov 02, 2011 7:17 pm

syrius wrote:Trumpets leng = 60 mm
I think ist too long when I install the original air box .

2 ways :
1/ exchange the trumpet by shorter
2/ exchange air box by TTR version

May be the fisrt one is less expensive , but I need to modify somethink on Weber ?

Thanks for your help

Serge


Serge,

If it were mine I would revert to some shorter trumpets (of the same type) as suggested by Rohan. WRT Weber modifications...in theory if they increased air flow there would be weakening effect on mixture (or vice versa), which might suggest some jet changes...but doubt it would be necessary.

1.0 This thread mentions trumpets, flow rates and work by Vizard.
elan-archive-f16/ram-pipes-t11508.html

2.0 I haven't got the book, but have dug out this (3 page) article:

http://dl.dropbox.com/u/45450049/RAMPIP ... of%203.jpg
http://dl.dropbox.com/u/45450049/RAMPIP ... of%203.jpg
http://dl.dropbox.com/u/45450049/RAMPIP ... of%203.jpg

If you look at the examples (charted on page 3) the flow rate comparison between a 3" & 1.5" are the same, so lengths may not be a major factor.

Hope it helps...

Salut - Richard
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PostPost by: StressCraxx » Thu Nov 03, 2011 4:58 am

Hello Serge,

Congratulations on your Kampena motor. Rich Kamp does very good work.

Yes, your trumpets are too long for a stock airbox. The stock length is about 44mm.

Were the trumpets and the wire mesh screens supplied from Kampena, or were they added later?

I tried the mesh screens many years ago, but they did not work well for me. I think the combination of mesh screens and long trumpets in the stock airbox may not work well for you.



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Dan wise
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PostPost by: syrius » Thu Nov 03, 2011 10:34 am

Hello All

I discussed by mail with Richard the boss of Kampena motors and I said that the length of the trumpet is optimised for this engine .
If I reduce the length , he is not shure that the engine get his maximum power .

I think its a better way to increase the air box volume ?
I'm waiting for an e mail in UK , for a person who made a large air box , I think its a cover with the same deep in all the cover lenght.

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PostPost by: prezoom » Thu Nov 03, 2011 4:26 pm

Years ago, we did some dyno testing on the distance from the end of the air horn to any flat surface in front the horn. This was done on 40mm carbs. The absolute minimum distance where there was no effect, was 1 1/2 inches. Anything further out did not diminish or increase the engine output. Screens caused huge problems.

Using ram air into the carbs from the front of the car also made a significant difference in performance. Our first rough tests were back to back, with ram air and then disconnecting the ram air, and taking the air from engine compartment. Using ram air, on the front straight at Willow Springs Raceway, the difference was an additional 600 rpm at the start finish line. Lap times were a tad better as well.

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PostPost by: syrius » Thu Nov 03, 2011 7:05 pm

Many thanks for all comments
I send an order for a big air box , I hope there are enought place between end of horn and air box cover .
I come back to you after testing .

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PostPost by: Esprit2 » Thu Nov 03, 2011 7:40 pm

prezoom wrote:Years ago, we did some dyno testing on the distance from the end of the air horn to any flat surface in front the horn. This was done on 40mm carbs. The absolute minimum distance where there was no effect, was 1 1/2 inches. Anything further out did not diminish or increase the engine output. Screens caused huge problems.
The Rule of Thumb I've always used is that the minimum distance from the end of the trumpet to any flat surface should be equal to the throat diameter... 40mm for a DCOE40. 1 1/2" is 38.1mm, or in the same ball park.

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PostPost by: Esprit2 » Thu Nov 03, 2011 8:09 pm

syrius wrote:I discussed by mail with Richard the boss of Kampena motors and I said that the length of the trumpet is optimised for this engine .
If I reduce the length , he is not shure that the engine get his maximum power.

I think its a better way to increase the air box volume?
The volume question really comes down to is there enough room for a larger airbox in your car. You need 38-40mm from the end of the air horns to the inside of the airbox. You can measure that now... is there room?

Tuning the length of the intake can optimize peak power output for one engine set-up. If you're going to desperately cling to every last fraction of a horsepower produced during the dyno run, then yes, the longer air horns Kampena provided may give you the best chance of preserving that power.

And yes, Kampena can't guarantee the optimum peak power he promised if a slightly shorter air horn is substituted.

But it's not a matter of the engine running "poorly" without that length of air horn. It may lose a small amount of peak power with a shorter air horn, but it can still run well. Worst case, you may have to slightly tweak the carb jetting, but no more than you would if you moved to a different altitude above sea level.

Any airbox will slightly restrict airflow and reduce horsepower a small amount. The fact that you're willing to run an airbox indicates you're willing to accept a small loss of peak power. Installing shorter air horns to fit with proper clearance inside that air box will cause another slight loss. Not really a big deal for a street car, but important to a serious racer.

Personally, given the high price of the larger airbox, I'd go with the shorter air horns first. It's a minimal cost & effort, and not a permanent, irreversible change if you don't like it later. At least you know the present airbox fits in your car without body modifications.

Good luck with whatever you decide to do.

Tim Engel
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