Induction & ITBs for Rover V8

[virgil]

Hello all. Looking to do some work on a TVR 500HC engine...new cam, new induction and after market EFI/Ingition

Looking to fabricate a less restrictive intake manifold with individual throttle bodies and plenum for feeding the engine 'cool' air piped from the front of the car. Not sure yet if short and near vertical stack (similar to existing manifold and trumpet base) or longer cross over with seperate plenums (similar to Cerbera AJP V8), but two main considerations with ITBs:

Air by pass for Idle Air Control - keep throttle butterfiles slightly open at idle, or incorporate a bypass valve with fully shut butterflies?

Vacuum for MAP and brake servo. 8 combiled pipes (V8 engine)

On OEM ITB installations I presume there is a 'collector' piped from the vacuum side of the ITBs for Vacuum for MAP and Brakes. Does anyone know what size the pipework is...I presume too small and reliable MAP signal is affected, too big and it must detract from the reason for using ITBs in the first place??

Cheers,

Virgil.

[Brummmie]

Just use one body for my brake servo, and balance them for idle, no bypass valve.

[virgil]

Brummmie said:

Just use one body for my brake servo, and balance them for idle, no bypass valve.

When you say ballance them, you mean the butterflies to each other so even vacuum across all 8, and just leave them open a crack to let 'some' air in at idle?

[Brummmie]

virgil said:

When you say ballance them, you mean the butterflies to each other so even vacuum across all 8, and just leave them open a crack to let 'some' air in at idle?

Yep, like a gnats cock, the slightest of turns sets them higher or lower, but then i have 8x 55mm chokes.

[virgil]

Brummmie said:

Yep, like a gnats cock, the slightest of turns sets them higher or lower, but then i have 8x 55mm chokes.

8x 55mm...blimey what heads are you running?...I was thinking more like 45mm.....

[EggsBenedict]

he's running an LS series engine. 45 or 48 would be OK. On TBs you can get away with a bigger bore than with a carb.

[virgil]

EggsBenedict said:

he's running an LS series engine. 45 or 48 would be OK. On TBs you can get away with a bigger bore than with a carb.

Ah, that makes more sense!!

[Pupp]

Not sure you'll get a MAP signal worth the name; not with anything like a decent cam in it anyway.

Be very interested to see what you come up with for the manifold...

[rev-erend]

Virgil - could I suggest you take a look at PH'er Eliot's Rover archive manifold site first..

http://www.mez.co.uk/ms12.html

My Wildcat TB's are on there too.. fyi 48mm.

[virgil]

rev-erend said:

Virgil - could I suggest you take a look at PH'er Eliot's Rover archive manifold site first..

http://www.mez.co.uk/ms12.html

My Wildcat TB's are on there too.. fyi 48mm.

Been there, seen it, and drooled...a lot.

Your TBs...what was the thinking between short and vertical as opposed to long and crossed over...I'm leaning toward midway crossover, keeping the airbox central rather than two seperate boxes over the rocker covers. Std 500 heads so no really high flow to drive up the rev range and go shorter inlet...

We'll see...

[rev-erend]

virgil said:

Been there, seen it, and drooled...a lot.

Your TBs...what was the thinking between short and vertical as opposed to long and crossed over...I'm leaning toward midway crossover, keeping the airbox central rather than two seperate boxes over the rocker covers. Std 500 heads so no really high flow to drive up the rev range and go shorter inlet...

We'll see...

It's not wildcats first go at TB's .. but the thinking is as straight as possible, whether they are too short I have no idea but they are really just for race cars, so I guess they spend more time at higher revs.

I've linked 4 10mm pipes to a billet collector for the brake servo feed and the fuel pressure regularor. No air bypass valve.

[Slow M]

http://www.wilsonmanifolds.com/products/throttle-b... too pricey for me.
I'll go with one of their elbows and a single large t.b. on my "conventional" (carb) manifold.

B

Edited by Slow M on Sunday 24th April 04:28

[Slow M]

rev-erend said:

...I've linked 4 10mm pipes to a billet collector for the brake servo feed and the fuel pressure regularor. No air bypass valve.

Where are the take offs for the four pipes? Did you experiment with where the best vacuum signal was to be found?
B.

[rev-erend]

No - they are beheath the throttle plates.. cant remember but about an inch. The TBs are straight so there is no issue with inside / outside of bend placement.

[plasticman]

Here is the before and after graph of my griff on throttle bodies on 14cux and no other mods .

[rev-erend]

Looks like 30bhp / 30 ft lbs improvement.

Pretty impressive.

Any photo's ?

[plasticman]

There is not much to see to be honest . The butterflies are housed inside the plenum base underneath the standard plenum top. The only difference is the throttle linkage now operating the two throttle rods instead of the butterfly in the plenum . It will go onto an emerald next and I will probably make a new plenum to suit . Then maybe a wilder cam !

[jr6yam]

Of course the big question is; did it get rid of the 'shunting'
(If you had any that is)
Seriously though, has it made any difference to the driveability?

John

[plasticman]

If that is the big question John , the answer is no .

[Brummmie]

I know mine is an LS, but still an engine, but it got rid of my shunting.
Its the reason i took the plunge, i didnt want to give up on camshaft, it also has improved my fuel consumption by around 20%, plus a bonus of around 35bhp peak, and around 90bhp at 7k!. Qtr terminal went from 129.9 mph to 133.42 with no other changes.

Expensive to trial for you though....

Edited by Brummmie on Thursday 12th May 08:02