Single 90mm TB vs IDF Style Throttle Bodies

[Wejjy]

So, I have a set of 45mm IDF style throttle bodies for my turbo'd Type IV motor. They have the injectors low in the manifolds and were originally my only way forward. Ive designed the Plenum chambers for them but not fabbed them up yet...

During some late night whisky fuelled browsing I spotted this...



...and subsequently bought one.

I was just wondering what the pros and cons are of single vs multi setups.

Would one large Plenum with the 90mm TB work as well as 4 individuals with 2 plenums and a T-piece to the Turbo? One is a lot simpler thats all 😋

Thanks guys

[Erlend / bug66]

This would surely depend on plenum and intake design I guess?

Whats the plan with dual TBs?

[Wejjy]

The plenums Ive drawn up are based on the 2.5 x engine displacement theory roughly. The limitation being space, so they are about 2.6 litres each in volume and run with velocity stacks inside. They are flat bottomed cylinders in shape. The intake is 2.5" primary about 350mm long splitting into 2" to the tops of the two plenums.

The single TB I havent done any planning for so could start from scratch going off what you guys advise... depends on the pros and cons?

[Erlend / bug66]

The plenums Ive drawn up are based on the 2.5 x engine displacement theory roughly. The limitation being space, so they are about 2.6 litres each in volume and run with velocity stacks inside. They are flat bottomed cylinders in shape. The intake is 2.5" primary about 350mm long splitting into 2" to the tops of the two plenums.

The single TB I havent done any planning for so could start from scratch going off what you guys advise... depends on the pros and cons?

I dont think you need two runners into a plenum? Sound complicated. A single runners placed right would surely be better..

With a single TB, you can make a really smooth flowing intake. Going intercooler? With a single I would have made a big Y after the TB, gradually decreasing the pipe size down to the heads. 

[PPRMicke]

So, I have a set of 45mm IDF style throttle bodies for my turbo'd Type IV motor. They have the injectors low in the manifolds and were originally my only way forward. Ive designed the Plenum chambers for them but not fabbed them up yet...

During some late night whisky fuelled browsing I spotted this...



...and subsequently bought one.

I was just wondering what the pros and cons are of single vs multi setups.

Would one large Plenum with the 90mm TB work as well as 4 individuals with 2 plenums and a T-piece to the Turbo? One is a lot simpler thats all

Thanks guys

One can handle 700 + hp  (90 mm)

45mm IDF style throttle bodies   More an 800 hk  ( 45x4 = Area on the hole)
/// Micke

[richie]

If its a street engine then don't use the 90mm throttle body, I have been doing some tuning on one and its really hard to get the off idle & light throttle area tuned well as even a small throttle opening allows a big volume of air to flow and it makes it difficult to drive. I would choose something around 60-65mm single throttle body but not really knowing enough about your engine or set up to really be perfect

cheers Richie

[Erlend / bug66]

If its a street engine then don't use the 90mm throttle body, I have been doing some tuning on one and its really hard to get the off idle & light throttle area tuned well as even a small throttle opening allows a big volume of air to flow and it makes it difficult to drive. I would choose something around 60-65mm single throttle body but not really knowing enough about your engine or set up to really be perfect

cheers Richie

90mm single TB has a smaller area of throttle plates than 4x 45mm IDFs or equivalent. 

Given the same throttle input, the twin TBs should give the engine more air?

Or is it something I forget?


I've also heard that 1 TB is harder to tune, but don't really get why..



What about a progressive ramp up on the TB-plate?

[Wejjy]

Thanks for the replies guys, appreciate them.

Engine wise, I have a 2316cc (96x80) Type IV lump, with forged pistons, piston squirters installed in the case, Webcam 86b with 112 deg lobes, reworked heads (cant remember exact specs) but turbo friendly, 7.5 to 1 cr, charge cooler system, dry sump, and full DTA setup for the FI.

I was concerned about low end tuning as I ran a motorbike with a huge single TB and it was awful low down, so may go for the quads.

Its all going in this thing

So needs to be tractable and smooth.

Thanks again guys 👍🏼

[Erlend / bug66]

You have a lot more room than us beetle guys   

[Neil Davies]

You have a lot more room than us beetle guys   

And a few miles more climbing frame inside too!

[Wejjy]

Once I have the dry sump tank, swirl pot charge cooler liquid tank, and barrel charge cooler, its tight!

Hence the question about saving a little space 😆😃

[Wejjy]

You have a lot more room than us beetle guys   

And a few miles more climbing frame inside too!

Well spotted 😉

[Erlend / bug66]

Once I have the dry sump tank, swirl pot charge cooler liquid tank, and barrel charge cooler, its tight!

Hence the question about saving a little space 😆😃

Surely the car is big enough to place the tanks somewhere else?

Cool setup anyway!

[Wejjy]

I could put them inside but then it wouldnt look 'normal' and be a family friendly camper so its all got to fit in the engine bay. You would be surprised how little space there really is if you mount it all out of sight 😋