Griff /Chim Plenum chamber sizes

[schimg]

Perhaps this is an obvious one, but can anyone tell me if plenum chamber sizes vary depending on the size of the engine they are fitted to(4.0,4.3,4.5 or 5.0L)?

i.e. Is there any difference in the diameter of a 4.3 throttle body in comparison to a 5.0L?

And what is involved in creating a larger throttle body and butterfly i.e. larger than the standard 5.0L jobbie??


Thanks

Steve . G.

[GreenV8S]

You really want to talk to ACT about this, but as far as I understand it the standard throttle bodies are the same (65mm) on all engines. However, ACT do offer various upgrades.

[schimg]

GreenV8S,

Thanks for this, yes it may be worth talking to one of the "known" entities .

Having checked the dimensions on the one off mine this would appear to be the case 65mm internal dimension and around 74mm external, I was hoping that someone off here had been down this route, and would know the tolerances for machining it out etc.

Steve.G.

[350matt]

you can bore out the standard plenum to allow a 70.0mm Ø butterfly, larger than this (72's were fitted to the SEAC and the like)and you need to sleeve the outside Ø.
Alternativly go for the ACT double or triple set-up?

Matt

[schimg]

Matt,

Thanks for this will give me a starting point, looks like the 70mm option at this stage, just need to get hold of a trumpet base next...

Thanks

Steve. G.

[2 sheds]

A bit late at usual
All V8 TVRs from 1990 onwards use standard 65mm throttle , basically all used the same plenum.
The alloy plenum can be easily modified we normally fit 71mm butterfly ,the largest we did was 74mm but the wall thickness starts to get too thin.
Just a point though, enlarging the single throttle size will only make a small power difference if any (about 2-3 bhp on a 500) but does increase throttle response, the limiting factor with these plenums is the throttle position and shape in relation to the trumpets.
Tim

[19560]

2 sheds said:

All V8 TVRs from 1990 onwards use standard 65mm throttle , basically all used the same plenum. The alloy plenum can be easily modified we normally fit 71mm butterfly ,the largest we did was 74mm but the wall thickness starts to get too thin. Just a point though, enlarging the single throttle size will only make a small power difference if any (about 2-3 bhp on a 500) but does increase throttle response.Tim

As I understand it that's Tim being fairly modest again. If you need a larger throttle body then Tim can do virtually any dia in carbon fibre and offer a slightly increased plenum chamber.

[2 sheds]

I used to produce a 78mm single throttle carbon, now superseded by the multi-throttle plenums.

[schimg]

Tim,

Can relate to your delay in response....

Thanks for this, I understand that the increase in BHP will be minimal, I am looking to improve throttle response and look further down the line for when I change cam etc..

The other thing that I am toying with is removing the trumpets and machining the trumpet base to get some flow then fitting the thermal plate.

What are your thoughts here?

Oh my car is a 4.3

Thanks again

Steve G.

[2 sheds]

schimg said:

Tim, Can relate to your delay in response.... Thanks for this, I understand that the increase in BHP will be minimal, I am looking to improve throttle response and look further down the line for when I change cam etc.. The other thing that I am toying with is removing the trumpets and machining the trumpet base to get some flow then fitting the thermal plate. What are your thoughts here? Oh my car is a 4.3 Thanks again Steve G.

For trumpets you have 2 options 1: remove intake manifold fully port to 45mm and fit 45mm alloy trumpets. or 2: fit superflare carbon trumpets which retain the standard bore size of the intake but produce higher gas speed to compensate, probably not quite as effective as option 1 but close and obviously much cheaper.
I think you'd be suprised how much benefit you get from these trumpet mods.
I wouldn't run without trumpets otherwise you'll loose some of the low-mid range torque.

Plenum enlarging will give you better throttle resonse.

Thermal plate is a good idea, i have heard some negative comments from engine builders but IMO can't do any harm.

Tim

[schimg]

Tim,

It would sound like the mods that I am thinking about doing make some sense then.

Thanks for the information and your opinions.

I am looking to increase throttle response so this should do the trick, these super flare trumpets sound interesting, I do not want to be loosing any torque as that is what these engines are all about IMHO.


Thanks.

Steve. G.