J35 Throttle Body on K24Z7

PASCIAK

PASCIAK

Well-Known Member
358
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AZ9thSi #001
Vehicle Model
Si
Body Style
FB6
I've tried the search function and not able to find anything internally. Went externally, only finding stuff for 8thgen civic with J35 TB installed.

Anybody here ever install the J35 throttle body on our cars, K24Z7. I'm under the assumption its a direct bolt on. just curious if there are any special directions for this bolt on item?

If anyone has installed this or has experience with it on our motors specifically please chime in!!!
 
vit's posted about throttle bodies before -
VitViper said:
People forget the one magic rule: diminishing returns. You can only squeeze so much power out of a naturally aspirated motor, this instance a 2.4L. Once you reach that threshold nothing you do will gain amazing amounts of power or any power at all -- that being said, no one has really done any conclusive TB testing. If someone wants to send me some various TB's to test on a 9th gen (I'll send them back, I promise ;)), I have a local 9th gen I can arrange something with. I'll even do it on a "real" dyno to make naysayers happy.

Something to keep in mind about Skunk2's comparisons: none of the graphs posted are of an internally stock K20 or K24. Why? Because anything larger than a 65mm nets zero hp on a fully bolted K series (K20 going from stock 60mm to 65mm TB gains about 2-3hp). I suspect on the K24 going from 65->70 is maybe 2-3hp as well.

The graphs on Skunk2's site show gains -- but look at the finer details. 11.5 C/R K20A2 (stock K20A2 is NOT 11.5 c/r). Or it's a higher C/R K24, or it's one of the two with a set of Skunk2 cams. And yes, I will tell you for a fact a larger than stock TB will make power when you have a set of Stage 2 cams in the car.
Click to expand...
 
I have the ZDX throttle body paired with an RBC. So, I needed an adapter for it to fit. Also required relocating the sensor from the throttle body to the RBC. Other than that it is a straight forward install.

I believe there could be a learning issue, but I didn't have any issues.
 
After doing some research i noticed the J35 TB is bigger then ours stock, but slighly smaller then the J37. how ever J35 tb can be had for less then 50 bucks. Im happy to purchase one and if needed get it bored out by Maxbore to compete with the J37 just not pay the price for a J37 TB. I was hoping to find some guys who've used or installed the J35 TB. from my understanding its the same as the K24z TB except just bigger, so it should be a straight forward bolt on, and since its slightly smaller then the J37 the relearning process for the ecu shouldnt be as harsh.. just want some more insight on this hopefully @Stealth @VitViper
 
I remember vits test on the RBC also included a throttle body and he said it really didn't make a difference

From vits article

"Now I really have no idea how TB swaps got so popular on bolt on motors. The simple fact is this — items like throttle bodies, injectors (yes I’m looking at the guys claiming RDX injectors are necessary with an RBC IM swap), etc, are nothing more than SUPPORTING modifications, and ONLY benefit you when the motor has a flow requirement that is now surpassed by the items on the car. To say the stock 9th gen throttle body is a restriction on a bolt on 9th is simply a JOKE. The following comparison demonstrates as much. For the marginal gains (1hp) that is had up top with the TB, as much if not more is lost in the mid/low end.

But so and so put a TB on and it pulls so hard…. sorry, please schedule an appointment to have the butt dyno re-calibrated."
 
So the factory throttle body is sufficient for the 230/240whp people are making today N/A. My only concern is if the stock throttle body is sufficient for making power low,mid and top end. why are people upgrading to an RBC when you have to get through the factory throttle body first?! I'm assuming then the power numbers everyone is hitting can be obtained with the factory TB, and manifold with the exception of 2-3 peak horsepower from the RBC. Am i right, or totally going the wrong direction with this?
 
And you sacrifice a decent amount of torque in the low to mid range for those extra ponies.

People jumped on the RBC initially because of the added power that it was capable of. We didn't know about the tradeoff back then.

Current line of thought is only do the RBC if you plan to go the turbo route. Otherwise, stay with the stock manifold for NA.

Of course, if we ever get decent cams, new tests will need to be ran between the two.
 
You also have to look at the dyno graph. And really pay attention to the torque curve. Not horsepower. Why? Because horsepower is not a measurement, it's a calculation. The formula is (RPM x TQ) /5252. What that means is that HP can be increased 2 ways, add TQ or RPM. If you look at the curve TQ starts dropping after around 6k rpms, however the rpms are still sufficient to carry the HP need up even though your actual power output is dropping. In theory the RBC manifold is just not dropping as much and also people with the manifold tend to up the Rev limiter. Sometimes to 7900 or 8k. That's why you see these people having "peak" power of around 230 HP, but in reality it's not really any faster of a car.

One example, examine the k20 vs k24 debate. 8k redline vs 7k redline, yet around the same HP rating. Because the k24 has more tq (and therefore is just plain more powerful). So let's even the playing field. Set both to a redline of 7k, k20 is now only putting out 160-170 factory rated HP compared to the k24. Rev both to 8k. K20 rating is 197 HP. The k24 would put out around 230.

Another good example. If I threw 2 baseballs at your face which would hurt worse. A 20lb ball going 5 mph? Or a 1 lb ball going 100 mph. Same concept.
 
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