# bigger throttle body pros/cons?



## bloo (Jan 31, 2002)

on a 1.8L 8V, g-grind, dual outlet manifold to tt downpipe, and close ratio trans, my car's zippy enuff, but has no top end. i like it, and mite as well keep it that way.. 
would a bigger TB from an A2 or audi 5K take away from torque? i hear that is adds hp and throttle response, but if its takes away from torque, it'd be like takin away from what my car does have, and kinda making it, well.. more mediocre. any thoughts?


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## Racer_X (Jul 14, 2002)

*Re: bigger throttle body pros/cons? (bloo)*

I've driven with stock throttle bodies, and with the Audi throttle bodies. I don't notice much difference in the mid range torque. It just seems to breath better on the top. 
Now, if you go with the Audi 4K/VW fox manifold, you'll lose a little bit of torque in the middle, but gain even more power at the top. If you have the trusty 4K gearbox, it's a blast everywhere except off the line.


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## bloo (Jan 31, 2002)

*Re: bigger throttle body pros/cons? (Racer_X)*

maybe ill give a larger TB a try.. but stick with the stock manifold. i dont wanna lose any mid, its nice to have a broad range of power, and not too peaky.. specially since its my daily city driver as well. breathe better at the top? my car's top is at 5500, then it just loses all its power.. if a bigger TB will give it a longer range without killin it off the start, sounds good to me http://****************.com/smile/emthup.gif


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## scirocco16v (May 17, 2000)

*Re: bigger throttle body pros/cons? (bloo)*

Do you have a thicker exhaust diameter? I see you said dual outlet manifold and tt downpipe....buit what about the rest? I have an Audi 5k TB on my scirocco( I also have a G grind and TT downpipe and 2" exhaust...oh...euro fuel distributor as well) but I wouldn't say it's the reason for added power(the tb)...supposedly it'll flow more air...and will in turn flow more fuel but from all I've read they tend to increase fuel consumption more than anything else. I wish I had before and after results to tell you of but I don't. I do know that you'll ned to port the intake manifold to make clearance for the larger butterfly valves...if you port it gradually vs. matched to the TB you should be able to hang on to more torque but you'll lose out at the high end.


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## bloo (Jan 31, 2002)

*Re: bigger throttle body pros/cons? (scirocco16v)*

thanks, i knew the intake would hafta be ported.. but ill consider not porting it fully to see what that does. my exhaust from the downpipe is 2 1/4", long glasspack in the middle, and a turbo muffler at the end so i dont get migraines on the highway. i had the exhaust guy clamp the turbo muffler on at the end so i could remove it and put in a straight pipe if i wanted, but he cinched down on the U clamp with an air wrench and the pipes are mated pretty good. i dont know how restrictive a turbo muffler is, but it was $20, cant be too much to it, and its gotta flow more then the stock cats and muffler did.


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## scirocco16v (May 17, 2000)

*Re: bigger throttle body pros/cons? (bloo)*

I'm thinking the 2 1/4 exhaust is hurting you in the torque dept. I'd be interested in your results of putting on a bigger TB. Pick Up and Audi 5k TB from a yard and tell me if you notice any difference.


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## ATS (Jan 19, 2002)

*Re: bigger throttle body pros/cons? (scirocco16v)*

The Audi5K (or Model 90) larger TB does not provide any HP reallyt, what it does is permit better acceleration (breathing of engine).
2" on an 8v is a good size any bigger than that then you are loosing backpressure and makes your top end feel weak


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## bloo (Jan 31, 2002)

*Re: bigger throttle body pros/cons? (ATS)*

quote:[HR][/HR]2" on an 8v is a good size any bigger than that then you are loosing backpressure and makes your top end feel weak[HR][/HR]​that's why i didn't go for 2 1/2".. i guess i just went a quarter inch too big.
i'll keep my eyes peeled in the junkyards for a TB. is a TB from an Audi 5K bigger then an A2 VW's?


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## KingOfFah (Sep 3, 2002)

*Re: bigger throttle body pros/cons? (bloo)*

bloo, get ahold of me on the server. i think i have a spare fox manifold and TB at my shop. might be a bit singed from the fire, but it was in my baja, so i think it's ok.


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## citat3962 (Oct 15, 2001)

*Re: bigger throttle body pros/cons? (ATS)*

quote:[HR][/HR]
2" on an 8v is a good size any bigger than that then you are loosing backpressure and makes your top end feel weak[HR][/HR]​For what it's worth I think this is wrong. If the 2.25 exhausts reduced topend why would EVERY exhaust maker for the A1 A2 8v cars sell a 2.25 and a 2.5. Nearly No one sells the 2 in anymore. Isn't that the same size as stock anyway?
Also the larger diameter exhaust...IF it was the wrong size it would reduce Low end torque not the top end. Like sucking water through a big PVC pipe as opposed to a straw. the larger pipe will allow air around the pulse at low overall flow (low RPM) creating he said low back pressure.....but at hi RPM you increase the exhaust production and there fore your Backpressure builds back up.
I read an article in European car that said, of the after market exhausts the TT 2.25 created the most torque increase and top end Hp. The 2 in exhausts offered little or nothing over stock and a Ghetto Buds muffler bent 2.5 incher made the most top end sacrificing only 1-3 lbs. ft on the bottom end.
I don't recommend the 2.5 I honestly think the 2.25 is the optimal til you go over 10Psi boosted or on a 280deg + Cam w/ a carb or ITBs and lots of porting...you'll still lose a little on the bottom but the top will make up for it due to the high flow mods youve already done.


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## scirocco16v (May 17, 2000)

*Re: bigger throttle body pros/cons? (citat3962)*

for 1, no a 2" is not stock....I have my 2 sciroccos right next to eachother. (77 and 79) the '79 has the tt 2" on it and it's considerably larger than the '77 which has the stock system on it. All I've read has indicated that 2" is excellent for my application...as i have a G grind with it.


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## lotus7 (Oct 30, 2001)

*Re: bigger throttle body pros/cons? (bloo)*

The 2 1/4" exhaust will improve your top end, but take away a little low end torque. The larger throttlebody will not be noticeable in itself, but will enhance any airflow improvements to the engine.
In order to take full advantage of your exhaust on your 1.8, you need headwork and more cam. 2" exhaust is really all that is needed for a 1.8L 8v.


[Modified by lotus7, 8:21 PM 9-6-2002]


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