Blue Thunder Weber manifolds

[Urgefor]

I see that Blue Thunder has 3 different Weber manifolds for the FE listed in their catalog.  The standard cut F.E. IDA Weber manifold, angle cut F.E. IDA Weber manifold, and eight ( 8 ) venturi FE IDA fuel injection manifold. Due to lack of information in their catalog and my inability to obtain additional information about the f.i. version of the manifold, I'm making this post in hopes of getting some useful information to determine if it would be a good fit for my project. As always, any information is appreciated.

[Urgefor]

I believe I have found a picture of Blue Thunder's FE IDA FI manifold.  Assuming the picture is their actual product, I believe I am safe in making the assumption that the only difference between the FI and non-FI version is the addition of a vacuum plenum as shown in 351's version of the manifold.  If anyone is aware of any other difference between BT's FE FI and non-FI IDA manifolds, I'm all ears.

[e philpott]

Looks like a splash shield to me but I would be surprised if BT has anything available/in stock for FE

[blykins]

The EFI intake does have a common plenum for manifold vacuum. 

[Urgefor]

Looks like a splash shield to me but I would be surprised if BT has anything available/in stock for FE

I couldn't find a picture without the cover, but did watch a video for that 351 intake that showed it without the cover. It is a common plenum underneath.

The EFI intake does have a common plenum for manifold vacuum.

Thanks for the verification Brent.

I've searched through the dyno results section for any results using a similar setup.  Closest I found was a SOHC Jay did with a modified Hilborn intake.  Basically I was trying to determine if the common plenum has any notable effect on dyno results compared to one without.  Once again, I assume that answer is "nope".

[kcoffield]

With IR EFI, you're pretty much stuck with speed density control scheme, no MAF (mass air flow) unless you want to put those pretty stacks inside and air box. Manifold Absolute Pressure through common plenum with EFI is sensitive to both the communication port size to each runner and plenum size. There can be a bit of trial and error if not voodoo here as you're really using MAP as a predictor of engine load for corresponding enrichment schemes.

Interestingly, in carbureted IR systems, this scheme can dampen reversion pulses and help smooth out eratic idle and off idle transition problems.

Best,
Kelly

[Urgefor]

Using individual stacks, that makes sense.  The fun part comes in when considering that plenum/intake/head combos used on modern engines are basically a different approach to IR induction (from a certain point of view) Like putting the stacks inside an airbox only w/o the stacks. Some with plenums that fasten directly to the heads and others that use an upper plenum with a lower intake fastened to the head.  The end result potentially being like those shown in the pics but using the IR EFI intake as the lower manifold to test different plenum designs.

[kcoffield]

Using individual stacks, that makes sense.  The fun part comes in when considering that plenum/intake/head combos used on modern engines are basically a different approach to IR induction (from a certain point of view) Like putting the stacks inside an airbox only w/o the stacks. Some with plenums that fasten directly to the heads and others that use an upper plenum with a lower intake fastened to the head.  The end result potentially being like those shown in the pics but using the IR EFI intake as the lower manifold to test different plenum designs.

Comes down to terminology I suppose but true IR has an isolated runner with a dedicated throttle plate on each runner, and most times a velocity stack on top of that but open to the ambient and not connected to a plenum. Plenums can change the inlet condition to a stack or open runner.

Everything else like the induction system you show is just a common plenum intake. Now, there might be several pleums in the scheme, like a dual plane intake, but those dont have much applicability to EFI because the purpose of those schemes is just to provide a stronger booster signal to the carburetor most often eqipped with primary and secondary throttle plates to further strengthen that booster signal......no need for that in EFI.

Best,
Kelly