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View Full Version : benefits of a bigger throttle body on S13



sr20xs
09-12-2004, 12:00 AM
I've done a search and nothing comes up so...what sort of benefits are people who've fitted bigger throttle bodies to their S13s getting? Which is the best one to go for - RB25, Infinity?

RDM_II
09-12-2004, 12:04 AM
None unless you're breaking over 400rwhp.

GlacierFreeze
09-12-2004, 01:12 AM
What motor?

Supposedly 300z guys use KA TB as an upgrade. Forgot where I read that.

Nikeboy355
09-12-2004, 01:28 AM
What motor?

Supposedly 300z guys use KA TB as an upgrade. Forgot where I read that.


you are referring to those who have S14SR throttle bodies I believe... the S14 SR is 50mm... the S13 is 60mm and the KA is 60mm... On my S14SR I am running an S13 throttle body and I noticed a huge increase in response... as for running a larger throttle body, there really is no reason to unless you are running a huge turbo and are strictly a drag car... the Q45 throttle bodies are gigantic at 90mm(I think there might be another size as well) and you can buy the flange online, weld it onto your intake manifold and go pick up some big hose clamps!...

_Def_
09-12-2004, 01:49 AM
The Z31 guys have a pretty small TB - so they use the KA TB as an upgrade.

Hugh
09-12-2004, 09:38 AM
S14 SR20DET throttle body swap here:

http://www.zeroyon.com/pics/installs/S14throttlebody/S14throttlebody.html


We noticed increased response as well. Why would they put on a smaller one and slow response? Thats retarded. Top end power didn't increase on this particular car, because it only made 363rwhp. However, the response made for a longer power band and faster car.

mattmartindrift
09-12-2004, 08:14 PM
S13 KA, and S14 ka have different throttle bodies also....I sat them side by side when swapping my last motor, definite size differences.

sr20xs
09-12-2004, 08:59 PM
i have an S13 sr20DET with the 60mm TB. So no-one with an S13 has gone for a bigger one? From what you're all saying re S14 to S13 swap benefits, sounds like it may be worth trying a bigger one on my S13 for increased response (stock now but mods soon). Latest Sub WRX is supposed to have a 90mm TB, older ones a 80mm.(is this the reason they go like crap down low?)

Kim_Jong_Il
09-12-2004, 09:03 PM
which one was bigger?

_Def_
09-12-2004, 09:27 PM
I've seen a Tomei kit to swap a 70mm N15 Pulsar TB to an SR. SPL Parts has it here:

http://www.splparts.com/Parts/SilviaShared/Engine/Tomei.asp

Scroll down to the bottom of the page.

Honestly though, for $300+ you're not going to really see any gains over a 60mm TB. It'd be one thing if our cars had a 45-50mm TB that was severely undersized, but 60mm is getting to the point of diminishing gains.

I can think of LOTS of places on a near stock SR that $300 would go much farther than with a larger TB.

Kouki14
09-13-2004, 01:32 AM
I have the infinity q45 90mm one on my sr

Hugh
09-13-2004, 07:16 AM
I can think of LOTS of places on a near stock SR that $300 would go much farther than with a larger TB.



Ditto.

The money is more wisely invested into other places. You can make gobs and gobs of power through the stock one... don't change it until you're making serious power.

sr20xs
09-13-2004, 08:53 PM
I have the infinity q45 90mm one on my sr



Is it as S13 or S14, and how does the performance compare?

Point taken re other mods first, however $300 is not alot of money if it significantly improves performance, and is a good basis for other mods, which is what I'm trying to find out here. (I will be doing exhaust etc soon.)

_Def_
09-13-2004, 09:29 PM
True $300 isn't a huge chunk of money, but when that's almost a third the cost of a blinging GT series turbo it puts it more into prespective.

0-1hp increase vs. 50-80hp increase


Hrmmmm... http://forums.freshalloy.com/images/graemlins/smile.gif


BTW - a 90mm throttle body is WAY too big for a 2.0L engine unless you're pushing over 450-500rwhp. There is such a thing as going too big with the thing. You'll basically increase restriction by creating alot of momentum changes in the flow. So while the throttle body is physically larger and can flow more air, when put in the system it'll actually cause a GREATER pressure drop. It's counter intuitive, but it makes sense when you think about going from a 2.25" pipe to a honking big 3.5" throttle body that has 2.4 times the area! The flow is basically going to be going quite fast, then almost stop compared to its previous speed through the TB, then pick speed back up in the plenum and runners. It takes energy to stop and accelerate all this air, and it comes in the form of a pressure drop as seen by the pistons/head ports.

So in a low HP application you're probably shooting yourself in the foot with a Q45 TB.

mechaniac
09-13-2004, 10:51 PM
you don't need to be making a crap load of power to take advantage of a larger throttle body, it will help in almost any application. (Not extremely large though) But if you do use a larger throttle body, make sure the manifold opening is matched, or it's redundant.

Jsquared
09-13-2004, 11:00 PM
True $300 isn't a huge chunk of money


I want a job that would allow me to say that http://forums.freshalloy.com/images/graemlins/tear.gif

_Def_
09-13-2004, 11:29 PM
I want a job that would allow me to say that http://forums.freshalloy.com/images/graemlins/tear.gif



hah - well, I won't say I'm exactly swimming in money(in fact I'm pretty broke) - yet totalling up what I've spent on my car in the past few months makes $300 seem pretty small sadly enough. http://forums.freshalloy.com/images/graemlins/tear.gif

I mean, it's like $2k almost to get a turbo/fuel/tuning setup for over 300rwhp. That's a huge chunk of dough no matter how you slice it, and makes the $300 look kinda small in comparison. Well, it's a relatively affordable way to waste money on something that gives you no power. http://forums.freshalloy.com/images/graemlins/grin.gif

Kookz
09-14-2004, 12:35 AM
(I will be doing exhaust etc soon.

If you haven't even done exhaust, put the TB idea out of mind, really.

sr20xs
09-14-2004, 03:01 AM
you don't need to be making a crap load of power to take advantage of a larger throttle body, it will help in almost any application. (Not extremely large though) But if you do use a larger throttle body, make sure the manifold opening is matched, or it's redundant.



Can you tell me more about your personal experiences with this on a 2 litre turbo? How big is too big?

I'm not discounting what others are saying and thanks for your opinions, it's just interesting that not everyone agrees and I'd like to know what personal experiences these opinions are based on. Too big slowing airflow too much makes sense, so are you saying 60mm is the perfect size for an SR20DET? I've seen a flow test in a magazine which found the std throttle on an S13 was a 6% restriction on the flow ability of the head, whereas an RB25 TB on the same head was a 3% restriction and a 75mm throttle was found to be a 1% restriction. The head had a mild port and polish. How much this would affect on-road performance I don't know.

Hugh
09-14-2004, 07:33 AM
True $300 isn't a huge chunk of money, but when that's almost a third the cost of a blinging GT series turbo it puts it more into prespective.

0-1hp increase vs. 50-80hp increase


Hrmmmm... http://forums.freshalloy.com/images/graemlins/smile.gif


BTW - a 90mm throttle body is WAY too big for a 2.0L engine unless you're pushing over 450-500rwhp. There is such a thing as going too big with the thing. You'll basically increase restriction by creating alot of momentum changes in the flow. So while the throttle body is physically larger and can flow more air, when put in the system it'll actually cause a GREATER pressure drop. It's counter intuitive, but it makes sense when you think about going from a 2.25" pipe to a honking big 3.5" throttle body that has 2.4 times the area! The flow is basically going to be going quite fast, then almost stop compared to its previous speed through the TB, then pick speed back up in the plenum and runners. It takes energy to stop and accelerate all this air, and it comes in the form of a pressure drop as seen by the pistons/head ports.

So in a low HP application you're probably shooting yourself in the foot with a Q45 TB.



If the piping and plenum all match the throttle body, then the intercooler is the only thing slowing the flow before the runners on the manifold.

I'm going to run intercooler piping that matches my Q45 TB. Mine is 85mm inner diameter.

_Def_
09-14-2004, 09:33 AM
If the piping and plenum all match the throttle body, then the intercooler is the only thing slowing the flow before the runners on the manifold.

I'm going to run intercooler piping that matches my Q45 TB. Mine is 85mm inner diameter.



Very true... but there really isn't a good reason to use a pipe that large. The pressure drop on say 2.5-2.75" ID pipes won't be that large given the max power you can make with an SR. I know you like to drag, so your idea isn't all that bad for your application. Yet I think if you did get something like a 70mm TB and corresponding IC piping then you'd see almost exactly the same power, and the engine might even be a little less "lazy."

I guess I should have clarified, I was more talking about someone with traditional 2.25" ID intercooler piping that suddenly goes to a big Q45 TB.

Hugh
09-14-2004, 06:17 PM
Well thats a given.

My friends with RX7's have been disproving theories about flow and velocity with extremely large intercooler piping. A few of them have 100mm pipes coming off the cold side of their intercoolers. It looks like they dug up a sewer pipe, polished it, and put it on their intake.

Yes, we're all drag racers as opposed to whatever else... but when you're going for big power, filling even 100mm piping is no problem. (as they've proven) My plan is to match the size of the Q45 on the cold side, and run most likely 70mm off the turbo. My last application was 70mm throughout with a 60mm stock TB. This time we're shooting for big numbers, though. http://forums.freshalloy.com/images/graemlins/wink.gif

Who cares about lag when you've got a two step?? Heh heh heh. This Z is gonna rip.

_Def_
09-15-2004, 07:24 AM
Yep, I don't know why people are concerned with velocity before the throttle body. It has no bearing on velocity in the runners. It does take time to pressurize the air between shifts though, so there are some negatives.

Shouldn't have much pressure drop, since you could flow enough air for a 15L diesel through those pipes. http://forums.freshalloy.com/images/graemlins/wink.gif

Enthalpy
09-15-2004, 07:31 AM
man. this stuff is so funny... we arent dealing with NA hondas here. you dont need to upgrade the TB. i have tuned several cars to over 500whp on the stock TB. unless you are looking to make more than that...dont bother.

TurboRotaryW_Pistons
09-15-2004, 10:01 AM
Hey Enthalpy, Would those cars you tuned to over 500whp made any additional horsepower by simply adding the bigger TB's?.... Just curious if they make any difference in numbers worth the swap.

-Alex B.

_Def_
09-15-2004, 11:00 AM
Another point - TB size, plenum volume and runner dimensions(length and cross sectional area = volume) all need to work together. From a quick eyeballing, it looks like the worse parts of this on a Redtop SR are the plenum and runner size. Notice the GReddy intake manifold goes to a larger plenum, while reducing the runner length to gain top end power.

The increased plenum volume does function similarly to a larger TB by giving each cylinder a bit more of a "buffer" before the pressure drops too low during each intake stroke.


So if you're really yearning to increase intake flow, go with something proven that actually IMPROVES your situation - get a better intake manifold. Heck, for less than $300 you can have one of the GReddy knockoffs shipped to your door off Ebay.

Hugh
09-15-2004, 11:32 AM
I went with the Greddy and the Q45 TB.

sr20xs
09-16-2004, 03:50 AM
I went with the Greddy and the Q45 TB.



Any before and after dyno graphs for the Greddy with Q45?

Hugh
09-16-2004, 06:58 AM
Haven't got it in a car yet, sorry. I'll be sure to report my findings, though.

lagvoid
09-17-2004, 11:00 AM
I'm curious to the actual gains/improvements on this upgrade too. I have two friends with highly modded sr's that have q45 TB's on them but never tested a before and after dyno. Can't wait to see what you create hugh.

Enthalpy
09-17-2004, 11:03 AM
I went with the Greddy and the Q45 TB.




hugh,

I have heard greddy makes an intake plenum that allows the Q45 TB to bolt right up. is this true?

Hugh
09-17-2004, 11:35 AM
I haven't seen it, but I wouldn't be too suprised.

I know they make one that has secondary injector holes already drilled into it... I bet that one would come with the Q45 flange on it.

Mine was prefabbed by a guy in mainland Japan, he was selling it and I was looking for a mani at that time... price was right, and it came with all the accesories, the TB and TPS for $500. I can't complain about that, really.

sillbeer
09-20-2004, 09:59 PM
When I ordered my Greddy Intake plenum I specifically asked if they make one with a flange to fit a q45 TB. The sells rep said no. Hey Hugh. I'm running a q45 TB on my car now with 100mm cold pipe and 70mm hot pipe. Seems to work pretty well. http://forums.freshalloy.com/images/graemlins/grin.gif

-Destin

Hugh
09-21-2004, 07:23 AM
You've also already reached my horsepower goal I thought... around 600?

white98s14
09-21-2004, 09:22 AM
looks like the S14 sr20de TB would be a could increase for us S14 sr20det guys..........does anyone know if someone can get these TB

Hugh
09-21-2004, 10:15 AM
I'll quote myself from above:



S14 SR20DET throttle body swap here:

http://www.zeroyon.com/pics/installs/S14throttlebody/S14throttlebody.html


We noticed increased response as well. Why would they put on a smaller one and slow response? Thats retarded. Top end power didn't increase on this particular car, because it only made 363rwhp. However, the response made for a longer power band and faster car.




Don't know any place that can get them for you...

sillbeer
09-21-2004, 02:00 PM
Yea, 587rwhp. That was at 1.25bar at 7k rpm's. Next time will be with 1600cc secondary's and some better tuning boosting 1.4bar. Should be close to 650. Hoping anyways.

-Destin

Hugh
09-21-2004, 04:06 PM
Yeah, I'm thinking of finding someone who can fit a 90mm outlet to my Apexi GT-Spec intercooler.