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Discussion Starter #1
I had planned on using a gsr tb I have for my boosted z6, whp goal of 300-400. I'm been consdering getting a 68-70mm tb instead. What effect will such a large tb have on daily driving?


Thanks.
 

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\/Your Mom Was Here\/
Vibe GT
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4,833 Posts
Make sure all the piping going to it is that size as well or it won't matter. A bigger TB will usually give some gains at higher RPM but at a loss for low end torque.

Do you have a performance intake manifold? Skunk2/OBX/Blox...
 

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Formally D_Tuned
97 civic HX
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I don't think I would go as big as a 70 for a street car, especially with a heavy pressure plate and firm clutch. I've driven a few cars setup with way more crap than they needed to make adequate power on the street and they just were a pain to drive slow.
 

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1999 EJ8
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1,188 Posts
Excuse me but WHAT?
Lmao.

As the 'Beave explained to me, having a large throttle body like a 68mm or 70mm is just far too big for those goals. It becomes an "on/off" switch, stupid response for a DD.

Stupid, as in horrible.
 

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You can get a 66mm or 70mm from skunk2 for like 130 shipped for the delta series

I bought the 70mm myself and haven't gotten it on the car yet, I'm going to be coupling that with the edelbrock intake mani with ported to 70mm inlet....but I have more of a drag car that I drive on the street and retained the interior for comfort....I'm willing.to give up a lil drivability to gain a bit of the upper rpms....I wanted my stock sleeves to be my limiting factor with no other bottlenecks

But I'm deffinatly in for more info
 

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()*#$(*$
93 Legend L Coupe.
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11,404 Posts
Lmao.

As the 'Beave explained to me, having a large throttle body like a 68mm or 70mm is just far too big for those goals. It becomes an "on/off" switch, stupid response for a DD.

Stupid, as in horrible.
No, I just want to know how the )(#$$# a larger throttle body supposedly makes a clutch engage easier.

Turbocharged can use larger TBs than NA engines, without much detriment at all. I still think 70mm is overkill unless you have a sleeved engine, but hey, rock on. Mid 60's is a good spot for most street driven turbo cars.
 

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Premium Member
89 CRX Si
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1,041 Posts
You want the air/fuel mixture to retain as much velocity as possible on it's way into the cylinders. The cylinders move a finite amount of air. If the passage through which the mixture travels on it's way to the cylinders is too big, the velocity will decrease and the amount of mixture that makes it into the cylinder (and pushes out the spent gasses) will be less meaning you will make less power.

Small changes to the diameter of the passage have large effects on the volume (and therefore potentially the velocity).

On a forced induction motor you can get away with a large TB and intake because the mixture is pressurized, but on a n/a setup you are depending upon the vacuum created by the pistons to draw the air/fuel mixture into the cylinders.
 

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No, I just want to know how the )(#$$# a larger throttle body supposedly makes a clutch engage easier.

Turbocharged can use larger TBs than NA engines, without much detriment at all. I still think 70mm is overkill unless you have a sleeved engine, but hey, rock on. Mid 60's is a good spot for most street driven turbo cars.
i have a 7lbs flywheel, so it takes more throttle so the motor doesnt stall when engaging the clutch in first gear, having a bigger tb gives more throttle response making it easier to engage first from a stop. make sense?
 

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()*#$(*$
93 Legend L Coupe.
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11,404 Posts
Oh . . . my . . . )(#*$!

Clutch engagement is a function of pressure plate stiffness, the step depth of the flywheel, thickeness of the clutch plate, coefficient of friction of the clutch material(s) for the flywheel and pressure plate combo, the lever ratio of the activation system, the "stretchiness" or compressiveness of the activation system and a few other )(#$($# factors. AND THE )(#*$()*#$ THROTTLE BODY SIZE HAS NOTHING TO DO WITH CLUTCH ENGAGEMENT.

Clutch engagement is an entirely separate issue from stalling the car since you can't balance the throttle opening with engaging the clutch.

A larger throttle body only "feels" faster because it lets in more air for the same angular opening. It's the SAME )(#*$(*#$ thing as pushing the throttle open faster. if you can't handle that, then you just plain old suck at driving.

For the record, my CRX has an 8lb. flywheel. And a stock throttle body. And a turbo. And a clutch that will make girly-men fill their diapers. )(#*$)(*#$

And you, repusnam55, you pusillanimous pissant of a turd, stop trying to instigate backyard, hokey grade school idiocy.
 

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Oh . . . my . . . )(#*$!

Clutch engagement is a function of pressure plate stiffness, the step depth of the flywheel, thickeness of the clutch plate, coefficient of friction of the clutch material(s) for the flywheel and pressure plate combo, the lever ratio of the activation system, the "stretchiness" or compressiveness of the activation system and a few other )(#$($# factors. AND THE )(#*$()*#$ THROTTLE BODY SIZE HAS NOTHING TO DO WITH CLUTCH ENGAGEMENT.

Clutch engagement is an entirely separate issue from stalling the car since you can't balance the throttle opening with engaging the clutch.

A larger throttle body only "feels" faster because it lets in more air for the same angular opening. It's the SAME )(#*$(*#$ thing as pushing the throttle open faster. if you can't handle that, then you just plain old suck at driving.

For the record, my CRX has an 8lb. flywheel. And a stock throttle body. And a turbo. And a clutch that will make girly-men fill their diapers. )(#*$)(*#$

And you, repusnam55, you pusillanimous pissant of a turd, stop trying to instigate backyard, hokey grade school idiocy.
so your saying that you never noticed that it took more throttle to not stall the car when engaging when you first got your 8lbs flywheel right?
 
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