Throttle body questions

[skyla]

Hi,

I have a R33 GTS25, currently it has K & N airfilter, extractors, and a 2.5" exhaust system. Currently I'm looking into enlarging the factory throttle body.

I'm haven't managed to find any one that has done it to there GTS25.

Have any of you guys/girls experimented with enlarging the throttle body?

Anyone know what sort of gains you could expect to get with a bigger throttle body?

Would enlarging the throttle body be likely to cause any problems?

Thanks in advance

[nismoman18]

if u enlarge the throttle body u should also enlarge everything else from filter back to suit it. making it bigger allows more air flow and most likely leaner mixture (more KW) the airflow meter will adjust timing etc. prolly to its best cos of the good airflow. Try it man, lots of V8's and V6's usually do that as an upgrade. however im thinking 6 throttle bodies

[Nismodified]

larger everything mite change the "volumetric efficiency", i think thats what its called.

In other terms, you mite find that you lose a bit or lower end torque, but gain more top end, pending on the changes you make.

Though i would LOVE to see 6 throttle barrels of the side of an RB25DE !

[NA_R33]

there is a place in melbourne i believe from melbourne, back in the day when i had my vl, that had an exchange program for like 300 hundred bucks for a bigger throttle body and they claimed it gave 30% more power, dont know if it fits ours or is relevant, but there are plenty of places that would be able to enlarge ours and make a new butterfly.

[skyla]

Thanks for the info guys,

I like the idea of multiple throttle bodies, but unfortunatly my pockets aren't that deep, and I've heard that they are difficult to tune, but if done properly can give you large gains.

So it would be a worth while mod to do.

Any body know what the T/B can be bored out to?

[Warpspeed]

Just ask yourself one question.

If a slightly larger throttle body is going to give you a 30% power increase, why did Nissan decide to fit a smaller throttle body to deliberately restrict power by so much?

[skyla]

Good point,

but I think the claim of a 30% gain is more likely to be on a multiple T/B set up, Can't imagine single enlarged T/B giving any where near that.

[Warpspeed]

Multiple throttle bodies only give you better throttle response, not more power. If you think about it, when the throttle is fully open it does not really matter where it is located. At full throttle all you want is a big open hole for the air to pour through.

It is true that any decent racing engine has multiple throttle bodies as close to the valves as possible, but they are not there for power. Actually the reverse is true. Multiple throttle bodies can never be larger than the intake runner size, but a single throttle body can be as large as you want to make it.

If all you want is maximum steady state dyno horsepower, a single large throttle body is the way to go. In Japan The fastest drag racers all chuck the multi throttle bodies, and fit a single large throttle body on their GTRs for that very reason.

But suppose you wanted to drive a formula one car around a wet race track on the absolute limit of adhesion. A single throttle body would be undrivable.

Ever hear those things revving the engine in the pits? The rate the RPM rises and falls is unreal. No formula one driver would ever want to hear about a sluggish big horsepower single throttle body engine.

Now some guys like the sound that six open trumpets make at full throttle, and that is another thing entirely. You only have to figure out a way to run it with a MAP sensor instead of an airflow meter. And how the lack of an aircleaner is going to quickly destroy your engine.

But if you want to spend a few thousand to get that great induction sound, and do not really care about the minimal extra power gain, or reduced engine life, then go to it.

[skyla]

Thanks, so I guess what people have told me in the past was not quite the truth.

Any way Multiple throttle bodies are out of the question for me, I have to be careful what I do, for insurance reason.

I have had a quote for getting my T/B enlarged for around $500, so basicaly I am wanting to know if it would be a worth while modification to make or would I be wasting my hard earned $?

[NA_R33]

it was only for a single throttle body, and it was for a VL from memory i think there was a dyno sheet with it that backed it up but it was at least a year ago so my memory may have faded a bit.

[skyla]

NA-R33,

Do you know if the 30% gain on the VL was just an enlarged T/B or was the intake plenum enlarged as well?

[Sledge]

I wouldn't recomend upgrading the throttle body untill you've at least fitted a larger lift/duration cam and had some port work done. All of which will will yield better power gains for the money spent. Only once you reach the limits of the factory throttle body should you think about changing it, any earlier and sluggish response and erratic behaviour will result.

Like Warpspeed said, multiples are only usefull for hard tuned engines that need very controlled thottle positions. And they cost a bucket, try $2500 for an RB,SR or L-series 6 version.

[NA_R33]

http://www.commsport.com.au/prod152.htm

thats it from commsport sorry i was going from memory its not 30 percent power gain but still conciderable, max before was 129rwhp and with the TB its 153rwhp

[skyla]

Thanks dude:)

[NA_R33]

no prbs