Accufab 75mm> 70mm.

[Jbauer]

I've called Accufab up on 5 occasions, and so have my friends.
Accufab told me, and has emailed me that:
70mm are for Automatic transmissions, and cars with no exhaust mods.
I told them i had a KandN intake, x pipe, and catback and they 'highly recomend the 75mm throttle body'
Hopefully, this will dispell some myths around here. There phone number is on their website- hopefully they don't get flooded with calls because of this

 

[JimC]

According to accufab's website the 70 and 75 tb and plenum combo flow the same volume of air. With your mods I would assume almost no difference between the 70 and 75 tb. If you plan additional mods just get the 75mm tb.

 

[Jbauer]

Really wasn't asking for opinions, just stating some facts that i've gotten from the manufacturer. I understand, it's hard to move away from beliefs that certain forums have drilled into peoples heads, and i understand some people have bought 70mm, and the thought of changing bugs them-
I'm just posting the facts, and information i've gotten from the manufacturer- and what they say is 'information relating to the 2v 4.6 in my car"

 

[04GTMustang]

yea i would agree with JimC. id say they would flow the same for a bolt on car but if you are adding a power adder i would say go big or go home. might as well go big anyways. at least i did cause i got mine in a package and the 70 and 75mm were the same price so i figured what the hey might as well.

 

[Jbauer]

Basically, heres the exact qouote

Unless your running a BONE STOCK engine or an automatic transmission with factory ring/pinion, we recomend the 75mm TB"

I then asked what if i had simple bolt ons, like a KN, catback, and X pipe,
and i was told for any of those above mods installed, a 75mm TB would be recomended, if it was on a manual transmission. I don't understand why the transmission would matter, but thats the response i've had multiple times.

 

[CobraRed_96_GT]

Jbauer, not to be a dick - but those aren't facts at all. Regardless of if one costs more than the other or not, of course they are going to recommend their biggest one on a modded car, otherwise why did they produce it?
I trust people have have done tests and can show that you cant even utilize 75mm until you're boosted more than the company who relies on their customers assuming they need bigger throttle bodies and plenums.

Your TB+Plenum isn't the bottle neck in the intake anyways, so going to 70 or 75mm will have the same affect as going to a 120mm intake - you can only suck so much through a straw, regardless of how big the end of the straw is - the initial part your sucking through is still small.

 

[BurningRubber]

75mm wont hurt. Your engine will only take so much air in to begin with...

Port your heads, install some "correct" cams (not just an off the shelf "should work" grind), and open the exhaust fully and I bet you the 75mm will make a little more power than the 70mm.

Stock for stock it wont make a big difference. Hell, replacing just the stock throttle body with a larger one wont even make hardly a difference. The TB+Plenum doesnt offer large gains on a near stock car.

 

[CobraRed_96_GT]

75mm wont hurt. Your engine will only take so much air in to begin with...

Port your heads, install some "correct" cams (not just an off the shelf "should work" grind), and open the exhaust fully and I bet you the 75mm will make a little more power than the 70mm.

Stock for stock it wont make a big difference. Hell, replacing just the stock throttle body with a larger one wont even make hardly a difference. The TB+Plenum doesnt offer large gains on a near stock car.

True, even full bolt ons wont warrant a 75mm me thinks, bigger maybe yes - but without a better flowing intake manifold and heads the 75 wont show gains over the 70. With cams, ported heads, springs....ect - i could understand it.
But on a car with intake and exhaust a company who sells bigger TB and Plenums saying buying a bigger one is best, that what we call a conflict of interest!

 

[Winters98GT]

70mm tb did nothing for my ported headswap car at CXI in 2001. there was no such thing as an aftermarket plenum then, so maybe that helps. I think Ill always be a sceptic.

 

[BurningRubber]

True, even full bolt ons wont warrant a 75mm me thinks, bigger maybe yes - but without a better flowing intake manifold and heads the 75 wont show gains over the 70. With cams, ported heads, springs....ect - i could understand it.
But on a car with intake and exhaust a company who sells bigger TB and Plenums saying buying a bigger one is best, that what we call a conflict of interest!

Yep, lol. Companies will push their products hard. If the claims were all true id have a 400rwhp bolt on GT... Its left to us die hards that go and buy the parts, dyno our cars and see what cumulative or individual gains are made...

70mm tb did nothing for my ported headswap car at CXI in 2001. there was no such thing as an aftermarket plenum then, so maybe that helps. I think Ill always be a sceptic.

The plenum is a must IMO to even notice anything. The stock opening on the plenum is around (if not) the same size as the stock TB if my memory serves me right. Putting a huge TB on there with the plenum having a small opening negates any purpose of the larger TB. Id venture to guess that is a large part in why people started making aftermarket plenums.

I did feel A gain with my TB/plenum, granted it wasnt huge but on the top end the car did breath easier and pulled a little smoother for a little longer...

 

[Roos85]

I agree with all these other people that 75mm isnt going to make a difference unless your running a power adder... Anyone know what the stock MM is on it?

 

[SilverBullet00]

Stock is 65mm I think.

MD did a dyno test on these. The 70MM made slightly more power than the 75MM on a N/A car.

 

[Jbauer]

well im just saying- people here say "Accufab recomends 70, so i use that' and accufab this, and accufab that- well..here- i have your answer. Accufab said use the 75 for even slightly modified manual trans cars. Not the 70. They said they recomended 70 in their testing, for bone stock engines, with absolutley no modifications, with automatic transmissions. And i've got this answer from diffrent people there. even if 70mm was big enough, its only 5mm larger- sounds like a waste of money, its barley noticable in size.
Just saying- for what it's worth.
Didnt want a controversy.

 

[Mustang92]

I wouldn't trust a manufacturers word period. They are there to do one thing sell parts. They will always do whatever it takes to make their products look good. Just like that junk ignition box that was out 4 years ago that they showed dyno proof that picked up 15RWHP and in real world tests gained 1-2RWHP at best. Or those CAI kits that would give you 25RWHP but in reality picked up 2-4RWHP on a cold day.

If you think 75 is best then great but until someone takes a car with basic bolt ons and goes to a controlled environment and swaps out from stock to 70 and again to 75 and dyno's the differences then people aren't going to listen. Till then it's just claims just like the guys with a G-tech in the old days that were running "11's" with bolt ons but couldn't muster anything faster than a mid 13's at a real track.

Bill

 

[jstreet0204]

Really wasn't asking for opinions, just stating some facts that i've gotten from the manufacturer. I understand, it's hard to move away from beliefs that certain forums have drilled into peoples heads, and i understand some people have bought 70mm, and the thought of changing bugs them-
I'm just posting the facts, and information i've gotten from the manufacturer- and what they say is 'information relating to the 2v 4.6 in my car"

Sorry man, but you aren't stating facts. What you are stating is sales talk you got from a manufacturer. If you want facts here are a few.

Fact 1)The theoretical max air flow of a naturally aspirated 281 cubic inch motor at 6000 rpm is about 488 CFM running at a volumetric efficiency (VE) of 100%

Fact 2) At sea level and an atmospheric pressure of 30 inches, a 281 cubic inch motor running at 100% VE with a 9.2 compression ratio will make about 290 horsepower. So basically to break 100% VE on a naturally aspirated 2v you will need every bolt on plus heads and cams.


Fact 3) Accufabs published flow numbers.
http://www.accufabracing.com/Flow Data.htm
--Stock 65mm TB -------------------------------- 588 CFM
--70mm TB ---------------------------------------- 708 CFM
--Stock 65mm TB and stock plenum --------- 441 CFM
--70mm TB and stock plenum ----------------- 491 CFM
--75mm TB and stock plenum ------------------------ 488 CFM
--65mm TB and accufab plenum --------------------- 557 CFM
--70mm TB and accufab plenum --------------------- 628 CFM
--75mm TB and accufab plenum --------------------- 628 CFM

So you can draw your own conclusion from that.

Disclaimer* I am multi-tasking while typing this so I make no guarantee that my math is 100% accurate.

 

[Jbauer]

WEll- why go with 70mm instead of 75 if they flow the same? ..they cost about the same most places- and at most are 5 0r 10 bucks apart.
Im just saying- i believe bigger is better, and the tech support at accufab told me to use 75..thats all.

Pretty much- i posted this for all the guys who say 'well, i went 70mm because accufab told me- you people just cant follow directions, etc. etc.'
So the next guy searching this- will have this to go off of. about what accufab REALLY says.

 

[Winters98GT]

I wouldnt listen to what accufab says.

 

[myponyrocks]

70 and 75 will flow the same on a bolt on car, I forget the site but they did the dyno and air tests.

Meaning the 75 doesn't hurt anything it just doesn't help more than the 70 on a mild application.

Throw boost or something into the equation and if you bought the 75mm you're one step ahead of the guy that didn't.

 

[Jbauer]

Heeere we go
http://www.mustangforums.com/m_1080031/tm.htm

 

['03GTinFLA]

I loved my Accufab 75cm plenum before I replaced it with my KB. It was so shiny.