Throttle body and intake manifold

[spetz]

Hi guys,

Is there a general consensus on the size of throttle body or any modifications to the intake manifold?

I have a Magna 65mm throttle body and I can see that the intake manifold has a bump that needs to be filed out.
Will a 70mm TB offer better results?

The engine has:
RPW extractors, hi flow cat, 2.5" mandrel exhaust
Ported/polished heads, match ported intake runners
Rebuilt/balanced + raised CR (heads were skimmed)
FPR and e-manage, CAI

Thanks

[Kustom]

viewtopic.php?f=1&t=22115&hilit=throttle+boring

[spetz]

Thanks Kustom I was just reading that but it doesn't seem like there is a definitive answer there?

[Kustom]

Did you read both pages? i thought the answer was fairly clear.

[spetz]

I read through all pages. But at no point was there a definitive answer as to which size is best etc.
Is 65mm ideal or will bigger yield better gains?
And personally looking at my 65mm throttle body and and intake manifold it, at least to my eye, does not look like welding is necessary to be able to expand the plenum to 65mm

[aza013]

I don't think any one has really done any testing on this.
So in away you will be the tester .

[spetz]

My results will not reflect upon anything though as I have no previous dyno figures

[phunkydude]

If it's gonna cost you 500+ to get it to 70mm, might as well go all out.
Fab a 6 pack individual throttle bodies.

Then your next mod would be 272 cams.
Gruk!..Grukkk!..Grukkkk..! Grukk! Grukkk!

[Shane001]

Remember to add bigger injectors first. Our puny 166cc injectors are perfectly tuned to the factory engine, they run in the high 90% at W.O.T.!

If u're gonna put more air in u need to be able to put more fuel in. U'll need bigger injectors.

PS: Ben can you fix the forum so W.O.T. without the dots doesn't autocorrect to what

[spetz]

Do they run at such high duty cycle?

The car isn't being driven yet and before it does get driven it will get tuned so I guess the tuner will tell me whether I need larger injectors or not.
Do any standard Mitsubishi injectors fit? I think there is a 210cc range and 240cc range which would probably be good for the 6A12 NA

[Shane001]

Mine log over 95% at full noise!

When sizing injectors you should aim for peak 80-85%. 240cc's should be OK for around 250hp at the flywheel.

Anyone know how much power we loose in our drivetrain? ie what this translates to at the wheels? At an assumed 80% loss this equals 200hp / 150kw at the wheels.

[spetz]

240cc are 50% larger than the stock ones so it seems they should be able to support more than just 250hp at the flywheel? I mean technically if stock power is 200hp, with 50% bigger injectors they should at the least be good for 300hp, right?

Personally I am hoping, and feel pretty confident, that I should crack the 150kw atw mark

[Shane001]

I'm just going off online injector sizing calculators.

[spetz]

Well according to a few online injector hp calculators our 166cc injectors should not produce more than around 150hp/110kw

[Shane001]

Yes, but at what duty cycle / fuel pressure. Bump the duty cycle up to 95% and you'll get close to the rated hp.

[Valandis91]

There's a lot more factors than just injectors size that determines how much power we should make...

[Shane001]

True, but you can only make as much power as the fuel you can pump into the cylinders. And no point putting more air in if you can't put more fuel in. More air/fuel = more power.

[spetz]

Do you know what injectors fit our motors?

[Shane001]

210 / 240 / 275 / 390

I've got a set of 390's I'll be selling soon, but these will be a bit big for NA.

I'm probably going to try a set of 275's for the racecar. Still researching though.

[spetz]

So all Mitsubishi injectors are interchangeable?
If memory serves me right, the 210cc were from the 4G93? 240cc were in the 6G72/4?