there are quite a few companies offering bored throttle bodies for the mitsi 3000GT engine in the good ol us of a .

this equates to a 9.4% increase in opening area . .

68mm appears to be about the size that there are no issues with breakthrough the casting, and able to get a perfect seal on the butterfly .. . .. .

does anyone know the following:

who does this accuraely in Oz? (CNC or 4-jaw chuck?)

any issues with throtle closure?

any issues with change in air-fule ratio?

idle quality, and throttle response - ie can the ecu handle the increase in airflow?

rgds

simon

I think a more viable option is dual throttlebodys. It would be a mission but it would offer real performance not just the feel of more torque because the TB lets in more air than normal at the same TB position, and 200% CFM is better than 108%CFM

whats a twin TB worth though?

']whats a twin TB worth though?
A lot.

It's my understanding you will need a piggyback ecu as well to run them. At least for the RPW ones. Not sure if Cthulhu is runnibng a Piggyback in his car with his setup but. Might bean idea to pm him about it.

A lot.

It's my understanding you will need a piggyback ecu as well to run them. At least for the RPW ones. Not sure if Cthulhu is runnibng a Piggyback in his car with his setup but. Might bean idea to pm him about it.
Yeah, it's a Haltech Interceptor.

Yeah, it's a Haltech Interceptor.
There you go. Cheers Redav.

i thguht u needed full aftermarket computer to run the 2 MAFs?

you wouldnt run dual MAF sensors, a single MAP sensor as the primary load signal would be best, or if you could make both throttle bodys draw from a similar source a MAF sensor could be used.

the reason i was thinking 68mm single TB, is that the std ecu should be able to cope with the increased airflow, and factory nicities like cruise control would still work .. . . and it would still look factory!

unless the engine has well ported heads, or bigger cams - airflow requirments are not that high . .. .

any ideas on anyone out there with a CNC . .. . . . .

rgds

simon

Correct me if I'm wrong - but you're asking wether anyone in Aus is machining the factory 6g72/4 Throttle bodies out to 68mm??

To my knowledge, no one is doing this commercially presently. I know RPW did in the past but stopped because of the difficulty in making them, I also know of another member who tested the feasibility of doing it, and he also stopped after making only 1 unit.

How similar are the magna T/B's to 3000GT ones?? If they are a direct swap - then I recommend contacting the companies in the states that do this and enquire about getting a batch - I'm sure more than a few members would be interested.

the tb's have actually been successfuly bored out to 71.2 mm

wait a few months i know a few memebrs have got some stuff in the works

iv spent about 15 hour's on my t/b and iv got mine out to about 69mm, its still not finished, my idle is at 1200rpm, the smallest gap between the butterfly and the housing make's a huge diffrence with the idle, its not sticking though witch is good

PM EZ Boy about it. He's got the TB's in production.

70mm is pushing it with what's left,

Swapping out of a 3000gt may be difficult as their engine is around the other way to 3rd gens.

the tb's have actually been successfuly bored out to 71.2 mm

wait a few months i know a few memebrs have got some stuff in the works

you cant get 71.2mm out of a throttle body no matter what. reached about 70mm on mine before going through a wall. also you need to leave 1-1.5mm lip on the tb to allow it to seal 100%. so max you can effectively go is around 68.5-69mm

you wouldnt run dual MAF sensors, a single MAP sensor as the primary load signal would be best, or if you could make both throttle bodys draw from a similar source a MAF sensor could be used.
The problem with running a MAP sensor as your load signal is that you need to switch to a full replacement ECU rather than a piggy back.

Over the next two months I'm going to be trying out running each one of my two throttles through an independent air filter, where throttle one draws through the MAF and throttle two doesn't. There's no particular reason why that won't work - but it'll mean some extensive remapping of the load signal.

Oh, FWIW, my twin throttle arrangement should preserve cruise control. I say should because in order for everything to fit back together, one of the brakets needed to be refabricated. This has been done, but with my living 1800km away from Street Torque, it hasn't been fitted up yet :D

It was one of the design goals though. I like my cruise.

We need to know - Is the 3000GT throttle body larger than the Magna - before confusing the issue with talk of boring.

I'm having another go at boring a flogged out unit I acquired from a bashful AMC member. We've done some hard research (my cousin is a mechanical engineer) and are confident we can achieve a low idling, highly responsive TB.

The perfect solution is multiple tbs, sure. But for those people wanting to avoid unwanted attention from their insurance companies etc, the stock look with a little extra zest is quite adequate.

We must remember that everyone on a car forum has great aspirations for their car. If you've got a "P" on your car you can forget about most of those aspirations for a few years.

you cant get 71.2mm out of a throttle body no matter what. reached about 70mm on mine before going through a wall. also you need to leave 1-1.5mm lip on the tb to allow it to seal 100%. so max you can effectively go is around 68.5-69mm


nah 71mm is possible but is the absolute limit

The 3000gt uses the same throttle body as the TR/TS model magnas which is a stock 60mm unit - I am not sure how they are getting them out to 68mm but it is a possibility, normally you can get them out to 65mm quite easily.

We were able to get the magna units as people know out to 70mm but there was always the issue with the offset butterfly having a vacuem issue of holding open at idle with higher idle speeds and especially on deceleration.

Good news is though we are near final testing on our aftermarket throttle body / manifold combo's and if this last test works - we will be able to provide 80,90 and 100mm throttle body options for stock ecu systems (Although a big 80mm or larger will more than likely need some ecu retuning to compensate for the large gulp of air that it will get).

Testing it on monday on my car but if it all works - we have solved the ifnal piece of the puzzle and will then start manafacturing the appropiate flanges to adapt onto our manifolds. Can't wait cause this is just what the magna vehicles needed.

And for those interested - have already started work on the new 380 throttle bodies - and there is definitly some fun going to be happening there. Bought one a week ago and have already finalised the boring of them out to a whopping 70mm. Side effect - they won't go backwards across to the TE - TL range due to there inbuilt fly by wire / tps control.

Now we just have to get hold of the 380, fit it up and see how it goes. But that belongs in another forum another day.

Good news is though we are near final testing on our aftermarket throttle body / manifold combo's and if this last test works - we will be able to provide 80,90 and 100mm throttle body options for stock ecu systems (Although a big 80mm or larger will more than likely need some ecu retuning to compensate for the large gulp of air that it will get).
Just wondering, is the same bolt pattern used for these TB's and the stock TB for fitment to the stock plenum or your larger one?

or if you could make both throttle bodys draw from a similar source a MAF sensor could be used.


Thats what i would do. Bit of ducting and you'd be right.

No the new throttle bodies will be using a different flange plate pattern. For those with our exisiting manifold packages, we will do a swap out with a manifold with the appropioate flange plate on it if they decide to upgrade to one of our newer throttle body packages.

i was thinking about a bored single TB, as the ecu should be able to cope without modifications, and other factory nicities should still work (like cruise control), and it shouldnt cost a fortune. . . . .

also, unless it has a huffrer on it, the airflow demands are not that high. . . . .so a twin may be over the top.

any ideas on whom has a cnc and wants to give it a go???

rgds

simon

has anyone thought about seeing if it would be worth importing a few from the USA as a group buy ????????

rgds

simon

Ok, found the limit of the TB we were boring - was a pube over 70 before the bottom water jacket poked thru to say "Hi!". 68mm is looking quite safe using our milling technique. Will be having another go over Christmas break to get one done an idling under 1K.

Interesting to see how Stonesour goes with his. The bore size is effected by your bore angle too. Some drag boys told us the magic number. We learnt a LOT that day.

Ok, found the limit of the TB we were boring - was a pube over 70 before the bottom water jacket poked thru to say "Hi!". 68mm is looking quite safe using our milling technique. Will be having another go over Christmas break to get one done an idling under 1K.

Interesting to see how Stonesour goes with his. The bore size is effected by your bore angle too. Some drag boys told us the magic number. We learnt a LOT that day.

I will agree with you there cos when i did my 2 oversized TB's i tried different ways and i also found sum TB's to be slightly thicker in there wall thickness, hence why i was able to get mine out to the size i have it at but there bugger all left before it would break thru (xrays proved that)

NOTE: i used a CNC machining centre to enlarge mine

What did the CNC time set you back?? We're made an adjustable boring bar and mounting platform to get inside the rear lip and start taking off metal around the butterfly circumference and surrounds.

Hows the idle on your 68's? What performance results did you get from the OS work? Fuel econ?

What did the CNC time set you back?? We're made an adjustable boring bar and mounting platform to get inside the rear lip and start taking off metal around the butterfly circumference and surrounds.

Hows the idle on your 68's? What performance results did you get from the OS work? Fuel econ?

CNC time didnt cost me anything as i did it after work hours.
Ive got one at 70mm and the other just over that size. I found using the machining centre was easier and better than using our normal 3 axis CNC lathes.

My idle is good (my car has to idle higher due to the cams anyway) as for power wise i havnt dynod the car since before i did the TB's but there is definate increase in top end pull from 5000-7200rpm.
I mainly did them as 1: a trial to see max size and 2: so i had one for my new rebuild that im currently doing

Fuel economy hasnt changed at all since the fitment of my oversize TB.

Hey jason have you thought of doing a couple more TB,s for us to buy.

Hey jason have you thought of doing a couple more TB,s for us to buy.
No, he hasn't. He has enough people asking for stuff.

No, he hasn't. He has enough people asking for stuff.

CAn you bore me a throtle body then Redav? lol

CAn you bore me a throtle body then Redav? lol
:cool:

Only if you supply the dental floss. It might take some time too :bowrofl:

The post-oversizing review has been completed on the TB we busted thru on. We can get 70mm with caution, 68.5-69 safely. We will try another 'donor' TB this weekend or boxing day now that we know the bore-line we have to avoid :D :dancin: