ITB on a gtv6

[gtv6sv]

Hey guys,
Curious question, I've seen people put or recommend individual throttle bodies (ITB) on gtv6's and 75 v6's from motor bikes.
Would anyone be able to tell me the benefit of having them, power benfits, where to get them from and are they easy to mount?
Sorry for all the questions but advice would be helpful!!

[MD]

A throttle body is just that and it doesn't matter what it is from, car, bike, aircraft, speedboat-whatever. Making it fit and of an appropriate type and size for the application is the challenge. The benefits are the ability to individually tune the air requirements for each combustion chamber as opposed to providing an "averaged" supply via a plenum. Theoretically this would optimise the air/fuel ratio for each chamber thereby producing the best power output a naturally aspirated engine can do.

I have used motorcycle ITBs on my TS race car and they work well. No experience on a V6 application and it would be a much more complex process particularly when under bonnet room is limited above the valley.

You would need a clear objective why you would want to enter into this application.

[Mick A]

Jekyll & Hyde would be a good one to ask about this! He has done it to a V6.

[AikenDrum105]

Also gives much snappier throttle response having the butterflies on each intake  - a plenum with a single ITB at the end dampens things.

Dampening is not necessarily a bad thing  ;P     If you find the on/off throttle without feathering the clutch is breaking your neck you can usually dial in a little dampening in your aftermarket ecu...

Another way is to make sure your throttle linkages are giving you a good ratio of pedal travel to throttle opening..  the motorbike ITBs usually have a cam shaped throttle pulley for this reason - so the first third or half of throttle application opens more slowly.

waffling again - sorry

More importantly,  ITBs sound much more betterer ;P 


Cheers,

[LukeC]

In engines with large duration/overlap camshafts and a plenum, there is a phenomenon known as "Charge robbing". This happens at low air velocities in the inlet tracts: i.e. low engine speeds.

What is effectively happening is pressure waves travel back up the inlet tract at low engine speeds. With an engine that shares a plenum, these waves disrupt flow into the other cylinders. This will cause the engine characteristics to run in a less than ideal manner. This is one reason why V8s of old with large duration camshafts running carburettors on manifolds with a small plenum and short inlet tract runners "lump". The same engine with Webers, or ITBs will be idle far smoother at low revs.

The tendency to charge rob will continue up the rev range until the air velocity and pressure waves cease to interfere with the other cylinders. The longer the inlet runners and the larger volume of the plenum, the less affect the pressure waves will have on the other cylinders.

Not having a plenum as such and instead having ITBs will isolate these waves. So using ITBs will in effect increases low down flexibility and response, particularly at part throttle.

IMO, there would be very little to be gained with ITBs on a standard V6 apart from lovely noise. The throttle butterfly is plenty large enough for a standard or even warm engine. The biggest issue is the length of the tracts on the transaxle V6 cars... They are way too short!

Two possibilities to improve the inlet system of a V6 come to mind: One is to adapt a front drive V6 manifold into the car, to get longer tracts to improve torque. The other is to track down the inlet setup from a 2.0 V6 off an Alfa 90 (I think an Italy only model, that never came to Australia). They had ITBs as standard, with a non-Bosch injection system. Either mods would not be simple, but easier than using motorcycle ITBs.

I remember seeing on some post somewhere that someone had one of these engines here in Aus. The engine was trashed, but it had the ITBs.

The last carb twin cams, TS engines etc all had eccentric throttle pulleys for good off idle modulation.

[AikenDrum105]

That is a spectacular image Luke - awesome.

[jazig.k]

For those interested in a little development work, just think about how a 3D printer could make some interesting setups fairly easily... Plastic printing material that is stable at engine temps and with fuel is the problem...

[Duk]

Also gives much snappier throttle response having the butterflies on each intake  - a plenum with a single ITB at the end dampens things.

I don't think it makes them that snappy. https://www.youtube.com/watch?v=LUj02oQl3lk
Too much flywheel weight to be snappy.

If you want to get, eBay.
Easy to mount? Ahhhhhhhhhhh no. Lot's of fiddly custom made bits and pieces and the chances of having problems with sticky throttles or perhaps even having weird, inconsistent stiffness in parts of the accelerator pedal travel, a potential.
Not to mention idle speed control issues and reading a MAP sensor (BTW, REALLY would require a good quality programmable ECU or adapting a very tunable factory ECU.............)
I'd guess that while cool, they'd be rather pointless for a road car.

[AikenDrum105]

That vid shows a really nice looking setup !

I know what you mean about flywheel weight, but I think that's also struggling with bad off idle response for all the reasons above... you can hear it  when he snaps the throttles open.    they've got all the vacuum ports fed to a nice manifolds which is key,  but might have the map sensitivity down to smooth out the pulses... 

This one's a bit snappier - but by the look of it,  probably has a different flywheel and other goodies too 

You're right though - working with the map sensor and how those pulses are collected / damped etc is possibly the hardest part of putting these on.   The MS ecus (and others)  have an 'itb' mode which tries to address this by using MAP vs rpm for idle, off idle fuelling,  and then interpolates over to Throttle position vs RPM once you pass the area where MAP isn't granular any more.   Gives you back the sensitivity around the off idle area (once you get a pulse damping setup that works) 

Possibly a little more work than bolting a K&N intake on

Am I the only one that gets squeamish seeing unguarded cam pulleys ?   

[Duk]

Am I the only one that gets squeamish seeing unguarded cam pulleys ?   

I get a little squeamish. I get a lot more squeamish every time I'm reminded of how little belt wrap there is on the (car's) right hand cam sprocket................ 

[gtv6sv]

Wow so much knowledge on here, blows my mind! Thank you all!
I am about to start rebuilding and restoring my gtv6,  I'm currently in 3 minds, 1 Twin Turbo, 2 Supercharged and 3 the ITB method.
I want this car to be quite a quickish car however to be a proper build with reliability for regular weekend use.
I do love the sound of the ITB's, the look of them also drive me wild! However are they any good for a road car at all? Or are they more for a purpose built race car?
I have been thinking of doing a twin turbo set up like this,  let me know what you think in the attached pic.
I am quite inexperienced on the grand scheme of things, however i hope to make up for this in enthusiasm and gain knowledge through the club and forums alike.
I plan on my car on being a bit different to your standard gtv6 haha!

[gtv6sv]

Exposed belts always me make cringe!!!

[Duk]

Your photo is of a South African track car. And I'm 90% sure that it has a gearbox bolted directly to the back of the engine.......................
Something to keep in mind, is that the transaxles aren't the most robust of things. 

Things to keep in mind.
Turbos are wonderful, but cause massive heat retention in all of the exhaust side metal. Small and congested engine bays with turbos need extra attention to be able to deal with that heat.
And dealing with the heat will be an absolute must if you plan to have the car reliable, especially on the track.
Me and a workmate were remembering a story he told about an RX7 that caught fire out the front of his place, when the turbine housing's heat melted the brake or clutch's reservoir and brake fluid ran onto the turbine housing............ Who woulda thunk it that brake fluid would burn............... 
Notice the track car has some missing inner bodywork and roll cage tubes extend thru the firewall to deal with the reduced stiffness from removing the metal.
GarthW on GTV6.com has/had a very nicely done single turbo GTV6. Probably 1 of the best single turbs V6's I've seen done.

Superchargers have their own pros and cons. Not least of it will be noise.
But the actual installation requires accuracy and rigidity if the system (the belt drive) is to be reliable and durable. Most supercharger installations get very bulky very quickly, especially if you use a positive displacement supercharger like an Eaton.

I'm sure everyone has a love of ITB's in some way or another (they've nagged at me more than once). From what I've seen over the years, they do introduce a series of complications. Their bulk being one of them (less room under a GTV6's bonnet than there is under a 75's bonnet) and again, accuracy of the installation is required so that they are reliable and safe.
BMW used ITBs in the E30 and E36 M3s. And Nissan used them in the R32-R34 GTR and the Pulsar GTiR. But ultimately, most cars just don't use them............
A 600hp normally aspirated 4.5 litre V8 Ferrari 458 Speciale doesn't use them, for example.

As per anything that we do to our cars, a lot of it will come down to money, available equipment (money........  ), experience, understanding and money.
I'm not trying to put you off, but I am trying to keep it real.
I'd suggest doing, or have done for you, a good quality installation of a good quality programmable ECU and see how high the levels of enthusiasm are after that.

[gtv6sv]

Yes that is correct, and what a car it is!
Heat would be a problem, I would plan on making extra scoops on the bonnet if so for extra air flow.
I wouldn't be going for monstrous power, something just make it 'special'.
Would people recommend the single turbo perhaps? I must look into this!
If i had to go down the supercharger way, it would be through the greg gordon kit, if possible.  You are right about the whine of the supercharger, sometimes i love it, sometimes i don't.
Yes money is always the factor when it comes to cars haha! An ecu would be key here, what people recommend regarding ecu's?

[AikenDrum105]

I'd always thought that once you moved to any form of forced induction, the benefit of ITBs becomes significantly reduced - moving to one or two throttles making life much easier to manage plumbing and setup wise...

But happy to be re-educated on that one