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upgrading throttle body from 75mm to 80mm

This is a discussion on upgrading throttle body from 75mm to 80mm within the External Engine forums, part of the LSx Technical Help Section category; I'm thinking about reaming out the TB opening on my FAST 78 intake manifold to 80mm and upgrade my 75mm ...

  1. #1
    Member qwik219d9's Avatar
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    upgrading throttle body from 75mm to 80mm

    I'm thinking about reaming out the TB opening on my FAST 78 intake manifold to 80mm and upgrade my 75mm TB to 80mm TB.

    ?1.will I gain any power? if yes approxity how much?

    ?2.will I lose any low end power then gain higher up power?

    ?3.will I need to upgrade my stock 75mm MAF also, to ZO6 type 85mm MAF to see benefits of the 80mm TB?

    ?4. will I also need to upgrade the 75mm air lid to 85mm?


    car is 99 WS6 A4,346CI street/stripe cam,LTs, ported 75mm throttle body
    and ported (for stock heads) FAST 78. small TC

    Thanks
    cam-LTs-FAST78-Susp.-Rims

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    Member MachWon's Avatar
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    Quote Originally Posted by qwik219d9 View Post
    I'm thinking about reaming out the TB opening on my FAST 78 intake manifold to 80mm and upgrade my 75mm TB to 80mm TB.

    ?1.will I gain any power? if yes approxity how much?

    ?2.will I lose any low end power then gain higher up power?

    ?3.will I need to upgrade my stock 75mm MAF also, to ZO6 type 85mm MAF to see benefits of the 80mm TB?

    ?4. will I also need to upgrade the 75mm air lid to 85mm?


    car is 99 WS6 A4,346CI street/stripe cam,LTs, ported 75mm throttle body
    and ported (for stock heads) FAST 78. small TC

    Thanks
    1. yes, I would be suprised if you saw anything more than 5hp
    2. doubt you would lose any low end
    3. you don't HAVE to upgrade your MAF but a restriction is a restriction and you would benefit from a larger MAF, that would probably net you more power than making your tb 2mm larger than it is now but of course both combined would be even better
    4." "

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    Member qwik219d9's Avatar
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    silver
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    autoban

    looks like I leave the current stuff alone, thanks for feedback.

    BTW are you hauling ass on the German autoban?

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    Senior Member TransAm11973's Avatar
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    yea you wont see much of a gain, unless you are going to go way bigger on the TB and change the intake manifold as well, I would just look into getting your stock TB ported and polished. I had mine done by mark shaner, he did a great job

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    Member qwik219d9's Avatar
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    silver
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    tb

    yes that was my 2nd mod after the air lid a ported & polished stock 75mm TB.

    they claim 8 RWHP, my observations where quicker throttle response especially on roll on's.

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    Throttle bodies are one of THE biggest waste of money mods EVER. Seriously guys do your research on what job they actually perform. Bigger TBs are good for serious hp motors, high rpm and FI.

    Ask yourself this. If bigger is better why isn't there a 1000mm throttle body? Guess what happens with a 1000 mm throtle body? When you crack the throttle open slightly guess how much air you are letting in? probably a hell of a lot more than a stocker at wot so imagine now what the throttle response would be like??

    \felt like saying that.

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    Senior Member TransAm11973's Avatar
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    Quote Originally Posted by 5abivt View Post
    Throttle bodies are one of THE biggest waste of money mods EVER. Seriously guys do your research on what job they actually perform. Bigger TBs are good for serious hp motors, high rpm and FI.

    Ask yourself this. If bigger is better why isn't there a 1000mm throttle body? Guess what happens with a 1000 mm throtle body? When you crack the throttle open slightly guess how much air you are letting in? probably a hell of a lot more than a stocker at wot so imagine now what the throttle response would be like??

    \felt like saying that.
    yes i see where you are going with this....... lets not forget that everything is based off of a ratio, and that size also helps to determine ratio,....and with size comes more weight......now do you really want to be driving around with an elephant under your hood?? I am thinking that maybe you are the one who needs to do a bit of research....

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    Member qwik219d9's Avatar
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    silver
    99 ws6

    85mm tb

    OK guy's clam down. I was testing the feedback on the 80mm ream out.

    the other option I have is ream out the FAST 78 to 85mm.

    now this makes alot more sense to me to add a 85mm ZO6 MAF & 85mm air lid
    to a reamed out 85mm FAST 78 TB zero bottleneck.

    what's the sense in a larger ( like a a 90mm FAST intake) botttlenecked down to a 85mm MAF (besides I bougth the 78 mainly because I have a 346ci, and have been told the 90mm is mainly for larger than 346ci).

    seam to me 85tb 85MAF &85 air lid would be optimal on a 346ci.


    thoughts and comments are welcome
    Last edited by qwik219d9; 11-23-2009 at 05:48 PM.

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    Member joedude02's Avatar
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    i'm with you on this same theory. after headers, i"ll be doing exactly this, regardless of anyone else's opinion.

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    Senior Member 00z28bubba's Avatar
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    Quote Originally Posted by qwik219d9 View Post
    OK guy's clam down. I was testing the feedback on the 80mm ream out.

    the other option I have is ream out the FAST 78 to 85mm.

    now this makes alot more sense to me to add a 85mm ZO6 MAF & 85mm air lid
    to a reamed out 85mm FAST 78 TB zero bottleneck.

    what's the sense in a larger ( like a a 90mm FAST intake) botttlenecked down to a 85mm MAF (besides I bougth the 78 mainly because I have a 346ci, and have been told the 90mm is mainly for larger than 346ci).

    seam to me 85tb 85MAF &85 air lid would be optimal on a 346ci.


    thoughts and comments are welcome
    90/92 combos will give you more performance but on the stock 346 it wont be a spectacular gain. when you break open the engine and start changing cams and heads is when the 90/92 combos give the desired performance. stock motor its more or less a waste unless you want every last hp or have plans of opening the motor.

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    I wasn't getting into an argument although the smileys i chose may say other wise !

    The throttle body is a control device that lets air into the engine. They are designed to be a certain size so that when you are wot they let in maximum volume for a given displacement and all that jazz(FI, High rpm etc). By going too large you are letting more air at the same throttle opening. thats it. thats why you feel more response at low speeds and part throttle. With a larger tb the last 10% of throttle probably do nothing at all.

    if you are cammed, stroked, FI'd or make some good power then I say do it. But personally this is like buying a Tornado and expecting 30 hp. I'd suggest to save the cash on a TB for anyone with a stock motor and do a cam, ported heads or headers etc etc.

    If usain bolts mouth opened 3mm larger would he go faster? No. Now if he had larger lungs, more powerful legs, more energy in his blood... thats a different story aint it. Hope that makes sense. Working with a few racing teams I've delved into restrictor plates alot etc with engineers. It's really cool stuff and amazing how they are advertised and are such a huge $$$ item.

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    Senior Member kool-aide's Avatar
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    I was thinking about posting the same question, 75mm vs. 80mm. I have been toying with the idea of a ported stock TB. Then I thought wait, if the butterfly is still 75mm, then what was the point of spending money. Why not buy a true 80mm TB? From some of the comments it almost sounds as if spending any money on upgrading the stock TB is not worthing it.

    I have read numerous posts about the stock MAF and how it works just fine. What is the stock MAF size? Is it 75mm or is it bigger? I'm just speaking out my butt on a pencil and paper theory here. Why go bigger on the TB if all of the parts in front are smaller? Isn't that a funnel, even if it is in reverse, won't you in theory still get a certain amount of fluid flowing? Even if everything was perfect through each transition, wouldn't you still have a bottle neck in your flow?

    You could spend that money on maintenance, sound system, fuzzy dice, what ever, right. I mean if so many people feel the stock MAF is doing a bang up job. I say match everything to the lowest common opening, MAF, TB, intake, Lid, whatever it may be, and spend your cash on gas to enjoy it, .

    That's just my evil scientist theory.

    I deal in software. A bottle neck is a bottle neck is a bottle neck in my world. You don't throw more RAM into a machine if your software sucks. You don't by faster processor if you can't load the data need to keep it humming along. There is always something slowing you down. You go for the area that can make real improvements when spending money. And that usually means you identify the bottle neck you can improve so you can then tackle the next one and so on.

    It's all about throughput in my world, but I also think an engine as a very similar pattern. How much in, what's the mixture, and how well can you push out the waste, lol...throughput. Just like crunching numbers in a spread sheet or exchanging data on a wire, .

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    Member qwik219d9's Avatar
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    85/85/85= optomam flow

    Quote Originally Posted by kool-aide View Post
    I was thinking about posting the same question, 75mm vs. 80mm. I have been toying with the idea of a ported stock TB. Then I thought wait, if the butterfly is still 75mm, then what was the point of spending money. Why not buy a true 80mm TB? From some of the comments it almost sounds as if spending any money on upgrading the stock TB is not worthing it.

    I have read numerous posts about the stock MAF and how it works just fine. What is the stock MAF size? Is it 75mm or is it bigger? I'm just speaking out my butt on a pencil and paper theory here. Why go bigger on the TB if all of the parts in front are smaller? Isn't that a funnel, even if it is in reverse, won't you in theory still get a certain amount of fluid flowing? Even if everything was perfect through each transition, wouldn't you still have a bottle neck in your flow?

    You could spend that money on maintenance, sound system, fuzzy dice, what ever, right. I mean if so many people feel the stock MAF is doing a bang up job. I say match everything to the lowest common opening, MAF, TB, intake, Lid, whatever it may be, and spend your cash on gas to enjoy it, .

    That's just my evil scientist theory.

    I deal in software. A bottle neck is a bottle neck is a bottle neck in my world. You don't throw more RAM into a machine if your software sucks. You don't by faster processor if you can't load the data need to keep it humming along. There is always something slowing you down. You go for the area that can make real improvements when spending money. And that usually means you identify the bottle neck you can improve so you can then tackle the next one and so on.

    It's all about throughput in my world, but I also think an engine as a very similar pattern. How much in, what's the mixture, and how well can you push out the waste, lol...throughput. Just like crunching numbers in a spread sheet or exchanging data on a wire, .
    stock MAF is 75 on F-bodys someone correct me if I wronge.

    if you're interested in a professionally ported TB I will let you have mine for a decent price however I will ask for a no refundable deposit.

    00z28bubba this is not a stock car as stated in the orginal post.

  14. #14
    Senior Member kool-aide's Avatar
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    thanks for the info on the MAF size.

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