Airbox design and dimensions for 2.0 TC GC rally spec engine

Competition engines and ancillaries - general discussion
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Kerem1967
Posts: 39
Joined: December 26th, 2012, 9:08 pm
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Airbox design and dimensions for 2.0 TC GC rally spec engine

Post by Kerem1967 » October 25th, 2022, 2:37 pm

Dear Friends,

Do you happen to have this information, drawing or dimensions as mentioned in the subject since I need to make an airbox for IDFs fitted on the 2.0 TC rally spec GC engine in a Fiat 131 ?

Since Guy has always been saying that it is mandatory to use an airbox on his performance engines to supply ambient temp air…

Best regards
GC_90

Spider 1969
Posts: 159
Joined: September 22nd, 2013, 7:21 pm
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Re: Airbox design and dimensions for 2.0 TC GC rally spec engine

Post by Spider 1969 » December 6th, 2022, 9:20 pm

Hi Kerem,

Phil Bugee from Bits Of Italy can help you in this matter. he supplies an excellent design which I use. I've tested it on the dyno and it has no loss compared to no airbox at all. See below photos.

Kind regards,
Charles
Attachments
IMG_5737.jpg
IMG_5737.jpg (132.73 KiB) Viewed 527 times
airbox-010.JPG
airbox-010.JPG (104.47 KiB) Viewed 527 times
airbox-002.JPG
airbox-002.JPG (147.45 KiB) Viewed 527 times
airbox-003.JPG
airbox-003.JPG (113.34 KiB) Viewed 527 times
Last edited by Spider 1969 on January 24th, 2023, 11:26 am, edited 2 times in total.
GC_26

Kerem1967
Posts: 39
Joined: December 26th, 2012, 9:08 pm
Contact:

Re: Airbox design and dimensions for 2.0 TC GC rally spec engine

Post by Kerem1967 » January 15th, 2023, 11:17 am

Spider 1969 wrote:
December 6th, 2022, 9:20 pm
Hi Kerem,

Phil Bungee from Bits Of Italy can help you in this matter. he supplies an excellent design which I use. I've tested it on the dyno and it has no loss compared to no airbus at all. See below photos.

Kind regards,
Charles
Hi Charles,

First of all, I am sorry for my late response. Somehow, I am not getting reply notifications and sadly since the forum is very inactive I totally forgot logging in among the other things in the workshop.

As a matter of fact, I have found Bits of Italy at google search and send an email but unfortunately I didn’t receive a reply at that time.

His design seems nice but how much room do you have from trumpets to top cover of that airbox ? That distance seemed a bit tight.

Also, I was planning to use a throttle mechanism which will work from the valve cover like the original twin choke carburetor. I am not sure if this airbox may work with that arrangement but I can always modify the bottom/back plate to run the mechanism from the top.

I would be grateful if you could share some photos of your throttle mechanism.

Best regards

Kerem
GC_90

Spider 1969
Posts: 159
Joined: September 22nd, 2013, 7:21 pm
Contact:

Re: Airbox design and dimensions for 2.0 TC GC rally spec engine

Post by Spider 1969 » January 21st, 2023, 9:35 am

Hi Kerem,

I'm not frequently online these days so it's the same with me ;-)

1: inlet stacks/trumpets.
General rule of thumb is that one would need 25 around in all directions. They are 25 mm high. Can't remember the Internal height of the air box but I think it is around 50 to 60 mm. (On the road at the moment so can't check) I did test it on the dyno with and without air box and there was no difference so 25 mm works well.

2: Throttle linkage:

If you can find one I would use the standard rod linkage for twin IDF. I don't have acces to a diagram of the twin IDF linkage setup as I'm travelling at the moment. So first image shows the diagram with the standard linkage for the earlier models. Horizontal rod 13 is placed between a front bracket on the manifold and a bushing in the firewall.

This does not work for the twin set up. On the twin set up this rod is located between a front bracket on the manifold and a bracket on the steering box. See image 2 where you can see it protruding from the steering box (manifold not in place)

Later I converted my steering to rack and pinion. So I did not have the steering box (and bracket) anymore. I then located the rear end of the horizontal rod between the front bracket on the manifold and a home made bracket on the rear of the manifold. See image 3 as seen from below. Also image 4 as seen from above/front.

Hope this gives you some ideas. Please share you ideas. thoughts, questions etc.

Regards,

Charles
Attachments
IDF_Linkage-018.jpg
Daigram
IDF_Linkage-018.jpg (141.19 KiB) Viewed 242 times
IDF_Linkage-009.jpg
Standard IDF
IDF_Linkage-009.jpg (796.74 KiB) Viewed 242 times
IDF_Linkage-017.jpg
Bottom view modified
IDF_Linkage-017.jpg (564.38 KiB) Viewed 242 times
IDF_Linkage-016.jpg
Top/Front view modified
IDF_Linkage-016.jpg (707.71 KiB) Viewed 242 times
GC_26

Kerem1967
Posts: 39
Joined: December 26th, 2012, 9:08 pm
Contact:

Re: Airbox design and dimensions for 2.0 TC GC rally spec engine

Post by Kerem1967 » January 22nd, 2023, 10:13 am

Spider 1969 wrote:
January 21st, 2023, 9:35 am
Hi Kerem,

I'm not frequently online these days so it's the same with me ;-)

1: inlet stacks/trumpets.
General rule of thumb is that one would need 25 around in all directions. They are 25 mm high. Can't remember the Internal height of the air box but I think it is around 50 to 60 mm. (On the road at the moment so can't check) I did test it on the dyno with and without air box and there was no difference so 25 mm works well.

2: Throttle linkage:

If you can find one I would use the standard rod linkage for twin IDF. I don't have acces to a diagram of the twin IDF linkage setup as I'm travelling at the moment. So first image shows the diagram with the standard linkage for the earlier models. Horizontal rod 13 is placed between a front bracket on the manifold and a bushing in the firewall.

This does not work for the twin set up. On the twin set up this rod is located between a front bracket on the manifold and a bracket on the steering box. See image 2 where you can see it protruding from the steering box (manifold not in place)

Later I converted my steering to rack and pinion. So I did not have the steering box (and bracket) anymore. I then located the rear end of the horizontal rod between the front bracket on the manifold and a home made bracket on the rear of the manifold. See image 3 as seen from below. Also image 4 as seen from above/front.

Hope this gives you some ideas. Please share you ideas. thoughts, questions etc.

Regards,

Charles
Hi Charles,

Many thanks. You have been very helpful.

I will study what I can do when the 131 is back from painters and I start the installation. Meanwhile, I will try to contact bitsofitaly again.

Regards

Kerem
GC_90

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