twin throttle manifolds

[part_time_hero]

hey just wondering if anyone has had any use, or problems with these manifolds that are selling on ebay, they are modified dual 60mm throttle body manifolds, look similar to the come racing ones, i am doing cam, head work and looking to upgrade the manifold and these seem to be a cheap alternative to the come racing ones, if anyone can help me that would be tops, thanks
HSV Holden V8 manifold VN VP VR VS SENATOR CLUBSPORT (eBay item 250768502184 end time 14-Feb-11 20:47:46 AEDST) : Cars, Bikes, Boats

[Darren_L]

they appear to be well made & very reasonably priced.
I haven't heard of any test results from them, but the basic concept seems to be good.
My only reservation/concern would be the small volume plenum chamber and also no mention as to whether the throttles are progressively linked or not.

[locolatino]

try looking at mace engineering site. or just give them a buzz! hope it helps!
i know they have some information on bored out throttle boddies. it might help! or just call them!

[Reaper]

Runner lengths and dias are all wrong. I looked at doing a banana chop job myself but there is no way of getting the runners right unless you scalp the manifold at the bottom flange height (ie clear off all runners and machine counter sunk bores) and press fitting new runners/trumpets at the propper height to make it work. What you have there is an expensive way of achieving not much better than std bananas.

Reaper

[Darren_L]

I picked up 30rwhp with the Trickshift manifold which is also basically a cut down banana manifold - although it does have a larger volume plenum than the one above

[T-rex]

Do you happen to know what the optimum RPM range on the Trickshift is?

[FstStig]

I would be abit questionable about buying from somewhere with the location "A happy place called Victoria"

Only joking.

They look like a nice manifold. Although could be a backyard job. Anything on ebay is always questionable.

[soop]

Runner lengths and dias are all wrong. I looked at doing a banana chop job myself but there is no way of getting the runners right unless you scalp the manifold at the bottom flange height (ie clear off all runners and machine counter sunk bores) and press fitting new runners/trumpets at the propper height to make it work. What you have there is an expensive way of achieving not much better than std bananas.

Reaper

This.
That manifold in the OP, is going to flow worse then a standard bannana manifold. The manifold has tuned length runners to suit the stroke of the 5ltr. This to avoid resonace in the manifold. If you cut the top off it, you're halving the intake runner length and opening up a plenum for reverberation to really hurt the intake flow. You'll loose bottom end torque due to the short runners and loose top end due to the reverberation.
There is a good reason proper twin throt manifolds cost allot of money, if they could just cut the top off the stock job and get awesome results they would.

[wez84]

I have always liked the Torque power manifold and a 1000cfm 4 barrel style throttle body set up.

[soop]

Yep, the TP + 1000cfm setup is a really good choice!

[DEE SS]

Who makes good twin throttle body setups with out breaking the bank too much? I also saw this manifold setup and was considering it, Im making 520hp in a 5.0L on 6psi, What HP range are the bannanas good for ? I dont like the look of the come manifold plenum and have heard mixed opinions about them, i have seen some really nice ones in the street commodore magazines but they all seem to be custom jobs.

[VrWagz1]

DEE SS, if your running boost then alot of the theory behind runner legnth goes out the window. You could quite easily run the OP manifold. If your boosting then the shorter the runner the better really. Running that manifold on a stock na motor would be pointless.

[DEE SS]

I am not familiar with runner length theory could you explain it more to me? Is there any other good twin throttle setups apart from the vn group a ss, as i have looked every where and cant seem to find a complete setup, i come across manifolds with out plenum and it looks like the manifolds suit carby not efi, why is it better with shorter runner on supercharged, sorry for all the questions. the only thing i dont like about the manifold that was for sale on ebay was it isnt progressively linked which if im correct the vn group a ss set up is.

[delcowizzid]

search through greenfoams threads he was building something just like this after he simmed it up on the PC with engine analyzer pro

[DEE SS]

Ah cool what was he building? what kind of power did he get and out of what?

[VrWagz1]

I will try to dig up the info i had been reading about it, but in a basic nutshell ill focus on the Helmholtz resonance effect. The inlet manifold is the reason you have a peak tourque range(but its to do with your cam aswell, the two work in tandem) Basically when the valve slams shut a pressure wave is formed in the runner due to the high velocity of the airflow in the runner suddenly stopping and creating a high pressure point at the valve. This high pressure point tries to equalise out, but due to its high speed nature it oscillates up and down the runner. The idea is that you re-open the valve when the pressure wave bounces back up the runner and is close to the valve again. The pressure then at the valve will be greater then atmospheric pressure and as such the air tends to "Burst" into the cylinder chamber when the valve is next opened(reaserch volumetric efficiency in manifolds), this sort of act like a micro turbo charger feeding positive air pressure. This is all caculated in the factory in the engine design stage. The strength and speed of the wave will be determined with some simple mechanical maths, and the wave whereabouts is simply some speed equasions in relation to runner diameter and length. The factory designates the runner legnth to catch this pressure wave at a certain point so that the cam opens the valve at the right point. One thing they cant do is make this pressure wave dynamic to the engine speed, that is "it is the speed that it is". So the pressure wave is only caught properly at a particular RPM, such as about 3500-4000rpm on the 5ltr i think, which is maxium tourque. As you go above this point power becomes difficult to generate(which any stock 5ltr owner will tell you)
If you chop the mainifold up then you simply throw out all this work and theres a fair chance your gonna catch the pressure wave in the wrong direction and loses alot of power. If you change the Cam then you risk opening the valve to early/late and missing this wave and basically have a negative affect on the engine. So really the runner legnth of the manifold needs to be optimized to suit the cam and at the level you want maximum tourque, usually anwhere from 20-100mm adjustment. Same in reverse, if you adjust the runner legnth then you need to adjust you cam to suit. If you whack a gas axe through the middle of the manifold and cut off 2/3rds of the total runner legnth, then you can see how stoopid that is
Somthing like that anyway, someone with a bit of smarts might correct me on this a bit.

Also it should be moderatly clear by now as to why with turbos and supercharges all this theory goes out the window. So basically with them, the shorter the runner the easier it is to just pump bucket loads of positive pressure into the chambers.

[DEE SS]

thanks for the info mate, so do you think the manifold for sale in the link at the top of this screen would work ?

[soop]

Only if you go everywhere at redline.
Intake runners are too short.

[VrWagz1]

For a naturally aspirated engine, it would be terrible. Like soop said. If you red line everywhere you may see somthing, but even that would be highly questionable and i would think even then it would be no!. They are just litterally too short. There are heaps of these manifolds booting about and the only reason they are built like that is because its easy to "chop" them there. There is no mechanical raschinal behind it.
It is diffucult to modify a banana manifold, thats why the redesigned 3rd party units are completely different designs and expensive. If they could just do a cut and chop on the stock units, they would.

The only thing these manifolds are perfect for is, forced induction. They are the perfect design for that.