ITB single air inlet - Engines Forum - Peugeot 306 GTi-6 & Rallye Owners Club

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Subject: ITB single air inlet

demondriverdan

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Post #1

This sounds crazy, and it is, but the championship I'm hoping to race in is requiring that there be a single point of air coming in to the engine so they can fit a restrictor plate.

My new engine is running ITBs so I'm going to have to find a way to make some sort of plenum to feed them from a single point. It is bloody stupid but I really dont' want to lose the bodies as I spent ages building this engine up and would be a waste of money to not use them now.

Any ideas on plenums I could use or a good design I could copy?

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Posted 21st Dec 2015 at 10:59

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phillipm

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Post #2

You're going to have to check the regulations for what you can actually have behind the restrictor - sometimes there are very specific sizes and lengths between that and the throttle body. However, if it's all free, then there's going to be 2 basic rules to a restricted plenum:

1) Make sure your trumpets stand clear of the plenum wall, at least half an inch, more would be better.
2) Make the volume of the plenum as large as you physically can. You get a good gulp of unrestricted air every time you open the throttle then.... Wink

You'll want at least 4 litres of volume, much more would be better.

What restrictor do you have to run, is it one they fit or one you can make yourself and they check? You can flow a lot more air through a properly designed restrictor than just a flat plate with a hole in...

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Posted 21st Dec 2015 at 11:13

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demondriverdan

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Post #3

Lots of that hasn't been decided yet! I'm pushing to get more info but from what you're saying it sounds solvable? I know I'll have to get the map tweaked, just have to accept that.

I wonder if it's worth getting a low rad to give me more space near the inlets to build a big plenum?

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Posted 21st Dec 2015 at 11:15

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phillipm

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Post #4

I would stick as much as you physically can in, even if it means running the intake backwards and drawing in from the rear of the bonnet by the windscreen, because you might find you want the length in the intake pipe to get a nicely shaped restrictor in (even if they're using a bolt in plate, nothing to stop you shaping the inlet before and after it Razz

)

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Posted 21st Dec 2015 at 11:18

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demondriverdan

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Post #5

Completely agree Smile

Sounds like it'll be an interesting design. Once I get more regs I'll update this thread to see if anyone has a good design. This isn't my area of expertise!

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Posted 21st Dec 2015 at 11:20

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phillipm

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Post #6

Yeah, restricted plenums are quite a different ball game to what you'd run normally. The mapping can be a little more tricky too as your tip in effects need to last much longer to compensate for the plenum pressure getting pulled down slower when you have a larger volume. You can fudge it just mapping the fuel but obviously then it changes with the gear you're in as the revs climb faster, so make sure your mapper runs in more than one gear on the dyno.

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Posted 21st Dec 2015 at 11:25

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demondriverdan

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Post #7

I got quite p**sy with the organiser when they introduced the rule, more money to spend!

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Posted 21st Dec 2015 at 11:23

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phillipm

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Post #8

More restrictions always ends up requiring more money tbfh. People never believe me when I say that, but consider ours is one of the cheapest sports going to get into and has no engine regs at all....run what you can shoehorn in.

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Posted 21st Dec 2015 at 11:27

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demondriverdan

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Post #9

I'm not sure where to put the air filter in the plenum setup either. Right next to the restrictor or use some sort of panel like the maxis

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Posted 21st Dec 2015 at 11:28

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phillipm

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Post #10

Behind the restrictor unless you can run a big panel with little pressure drop - you want as much pressure upstream as you can get. The denser the air at the venturi the more air you can flow even when it's choked.

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Posted 21st Dec 2015 at 11:39

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welshpug!

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Post #11

what size restrictor?

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Posted 21st Dec 2015 at 13:15

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demondriverdan

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Post #12

No idea. All that's been announced is that all cars (N/A and FI) will have to run a restrictor where the size will vary depending on class.

There's a lot of unknowns at the moment which is a bit of a ballache. Considering the car currently only has brake and clutch pedals and a brake servo, I have lots of other things to get on with first Smile

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Posted 21st Dec 2015 at 13:20

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phillipm

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Post #13

Does that mean the forced induction cars will be running in your class wth a restrictor? If so you're fooked

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Posted 21st Dec 2015 at 13:50

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demondriverdan

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Post #14

Yup although they'll have a different size restrictor to me (I hope!). Currently they're all limited to 34mm I think. All FI cars have to run a 25kg ballast as well

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Posted 21st Dec 2015 at 13:52

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welshpug!

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Post #15

think I'd be going elsewhere!

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Posted 21st Dec 2015 at 14:47

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demondriverdan

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Post #16

I went up against the FI cars with this year and did well enough, don't see it changing much next year. If there is a big issue with the regs then they'll make adjustments

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Posted 21st Dec 2015 at 14:55

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phillipm

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Post #17

With a 34mm restrictor they're going to stomp all over the N/A cars the minute someone builds one right, they'll be able to push ~340bhp and ~450lbft with a 2 litre.

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Posted 21st Dec 2015 at 17:31

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demondriverdan

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Post #18

It's also a power to weight series as well so although they could have that much power, they'd be too powerful. The 34mm restrictor is the standard MSA one, not something specific for the championship.

What would be a better thing to do is to get a map that puts you at your peak power as early as possible and stays there. That way you're running at the top of the class for most of the rev range rather than me who peaks.

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Posted 21st Dec 2015 at 17:34

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phillipm

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Post #19

That is exactly what they would do, hence the 450lbft+ of torque, they'd be near full power by 3.5krpm.

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Posted 21st Dec 2015 at 23:15

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daveyboy

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Post #20

Time for a turbo.

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Posted 22nd Dec 2015 at 10:08

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demondriverdan

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Post #21

I haven't even driven the ITB engine yet!

Low boost might have been a better option but when I built the engine aftermarket supercharging wasn't allowed. If it doesn't go well then fine, it'll still sound good just be slow Smile

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Posted 22nd Dec 2015 at 10:14

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Twangy

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Post #22

need to find out what size restrictor you have to run first , and then design airbox , or decide on other route to go

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Posted 22nd Dec 2015 at 14:21

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welshpug!

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Post #23

I'd go to a different series tbh, unless they see sense and class n-a differently to boosted, and not restricted.

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Posted 22nd Dec 2015 at 14:35

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