3rd Gen GK Specific Fit Engine Modifications, Motor Swaps, ECU Tuning Sub-Forum Threads discussing engine mods/swaps/tuning for the third generation GK Honda Fit.

Larger Throttle Body Modification - Maxbore

  #1  
Old 10-05-2014, 10:22 PM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Larger Throttle Body Modification - Maxbore

I removed the throttle body. I'm not a mechanic. Just a regular guy like most of you. After removing the intake itself, it's as only a matter of four bolts and unplugging some sensor that was attached to it. You'd also have to remove two coolant hoses from it but I have already done a coolant by-pass modification so it was not needed.


Here is what the intake manifold opening looks like. I measured its diameter at 2.155" (54.74mm) from top to bottom. Measures about 2" across.. It is not perfectly round though. Top to bottom is widest. Weird!



I then measured the throttle body inlet diameter. It measured at 2.172" (55.18mm)



Measuring the throttle body outlet diameter, I came up with 1.966" (49.94mm)



I put the throttle body on a scale and weighed it. This way we can gauge how much metal/weight has been removed. It weighed in at 2 lbs 1.6oz (953g)



It is all packaged up and will be overnighted to Maxbore tomorrow. George of Maxbore has been notified.



This is all I have for now. Will report back the new measurements and weight when I get it back.

And of course my disclaimer as always: I don't recommend anyone do this. I'm just showing you what I'm doing and reporting back my findings.




Please disregard this info below. Using it as a reference point from another thread I read on here.
Originally Posted by DOHCtor View Post
A 64 mm Throttle body would definitely be too big for a 1.5l engine... I used to mod many Neons in the past and i can say for sure than swapping a 49mm Mtx Tb for an 52mm ATX Tb on a neon gives more or less 6 to 10Whp depending on mods...

found this on the web a long time ago... sorry, it's from a neon forum but it should apply on all engines!!


Gary Howell wrote:

"49mm TB flows 252 cfm
52mm TB flows 283 cfm
55mm TB flows 317 cfm
60mm TB flows 377 cfm

At 8200 RPM (Max RPM of a DOHC Neon with AF\X-Race V1 PCM) a 122 cubic inch engine will need 290 cfm at 100% volumetric effiency, using the formula ((Max RPM/2)*Displacement)/1728. Rule of thumb is to go 10% over because a naturally aspirated engine can go above 100% volumetric efficiency because of cam overlap, header design, etc. Go above that and you kill low end because of reduced velocity, go below that you starve the engine for air at top end. 110% is volumetric efficiency is 319 cfm."

Hope this helps!!

Marko!!
Myxal Math ~~> {(6500/2) X 92}/1728 = 173cfm
10% over = 190.3 cfm

Originally Posted by DOHCtor View Post
I removed the throttle from my fit yesterday and actually the inlet seems to be 55mm tapering down to a 50mm butterfly... More then enough for a 1500cc engine reving to a maximum of 6500Rpm IMO... plus, they didn't left a lot of meat on the intake plenum to remove in case you would be putting a bigger T\B so i doubt it would gain power at all but just be a major PITA... as far as throttle response is your prime concern, i would buy a throttle controller instead and do the throttle halfshaft mod to gain some airflow at the upper revs...

The first hindrance to airflow in the fit motor is the stock airbox with it's laughable 44.5mm opening and 10 million resonator chambers... no wonder you gain as much power with a simple CAI or SRI!!

Marko!!
 

Last edited by Myxalplyx; 10-07-2014 at 06:50 AM.
  #2  
Old 10-09-2014, 12:56 AM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Spoon

While I wait, wanted to read up on what some manufactures are doing with the throttle body. Spoon has developed one --> Large Bore Spoon Throttle Body

It's in Japanese but the best I could do is this -->
I started the release of FIT3 GK5 for Venturi Big Throttle body.
The speed of the new FIT, which is DOHC direct 噴化 is well proven in the race anymore, the engine output up pick-up and further improve
I've developed for the purpose.
To 60mm from genuine 57mm, butterfly diameter and large diameter to 52mm from 50mm, intake caliber inhalation resistance in a comprehensive manner
The We improved charging efficiency by reducing.
Please experience the improved fuel economy in town use, power-ups and high response in circuit racing.
*
■ Product name: [, GK6, RU1 / 2/3/4 inch GK5 RS MT CVT] FIT3, VEZEL for Venturi Big Throttle Body
(Normal trade less)
Item Number: 16400-GK5-020
Price: 78,000 yen (excluding tax)
Classification: E
■ Product name: [, GK6, RU1 / 2/3/4 inch GK5 RS MT CVT] FIT3, VEZEL for Venturi Big Throttle Body
(With normal trade-in)
Item Number: 16400-GK5-021 [NTS]
Price: 38,000 yen (excluding tax)
Classification: S
Please see the philosophy page the following detailed description of the throttle body.
製品開発の哲* PHILOSOPHY
Learn more normal trade system for [NTS].


It'll be interesting to see how mine compare to this one when it gets back. BTW: The 78,000 yen equals to about $723. At least from what I typed in.
 
  #3  
Old 10-09-2014, 02:23 PM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Update 10/9/14

The throttle body has just arrived at my house. Kudos to Maxbore Jorge for doing what he said he was going to do. I sent this out overnight on Monday, Maxbore received it Tuesday. The bore took place Tues/Wed and he stated he would ship it out on Wed and here it is. Excellent!

The package arrived in the same box I sent it out in. It was wrapped up neatly inside this plastic.



So I weighed the throttle body. It came out to 2.05lbs (930g).
.05lbs (23g) weight reduction from metal removal.



Measured the inlet diameter. It came out to be 2.33" (59.24mm)
Inlet diameter was increased by .16" (4.06mm)



Measured the outlet diameter. It came out to be 2.095" (53.21mm)
Outlet diameter was increased by 0.13" (3.27mm)


I'm off to install it. I will not report butt dyno hp/tq impressions. That is subjective because naturally I want to feel an improvement. I'll let my 60ft times and 1/4 mile time and trap speeds tell the tale.

Please excuse any typos above. I'll correct later.
 
  #4  
Old 10-09-2014, 02:44 PM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Installed

Re-installation was a breeze. Just hand tighten the four bolts that held it on and tighten them snugly. Below is a pic of it installed on my homemade PRM cold-air intake. I started it up and it runs fine.



I did not disconnect the battery when I sent the throttle body out. There is no ECU reset. This is simply disconnecting the throttle body, getting it bored out and reconnecting. This way, there is no excuse that the computer was fresh with a fresh start, relearning, etc. If there is an improvement, it was simply from bolting this piece on.

Please keep in mind that my fastest time is [email protected] My average is 15.8 and 87mph. I KNOW if I drop down to lower 15.7's or trap into the 89mph range, this is an improvement. I have almost 40 dragstrip runs so far and temps ranged from 66F to 87F. I've never been able to dip down into the low 15.7s or hit an 89mph trap speed. From what I figured on using 1/4 mile calculators, I'm gonna need an extra 5hp to make it happen.
 

Last edited by Myxalplyx; 10-10-2014 at 05:41 PM.
  #5  
Old 10-09-2014, 05:36 PM
Member
Join Date: Aug 2012
Location: NYC
Posts: 419
This is some nice documented work!!
 
  #6  
Old 10-09-2014, 11:02 PM
Member
5 Year Member
iTrader: (1)
Join Date: Dec 2011
Location: San Diego, CA
Posts: 1,035
Whens the test run?
 
  #7  
Old 10-10-2014, 02:07 AM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Originally Posted by Rollerboots666 View Post
Whens the test run?
Ran tonight! Did 8 runs! I'll only talk about the first five runs though because I did something during the sixth runs and....let's just say things got ugly.

Anyways...here's the breakdown.
[email protected] (Maxbore Throttle Body)
[email protected] (Maxbore Throttle Body)
[email protected] (Maxbore Throttle Body)

[email protected] (Maxbore Throttle Body/Civic Maf Sensor Housing with 2.25" & 2.5" inserts to reduce diameter)
[email protected] (Maxbore Throttle Body/Civic Maf Sensor Housing with 2.25" & 2.5" inserts to reduce diameter

You don't want to know about my next 3 runs because I was trying to bring up my air/fuel ratios from 12.0:1 from these 4 runs I did. I removed the 2.25" insert in the Civic Maf sensor housing and left the 2.5" one in. Air/Fuel ratios went up to 14.0:1 (Yay) but my ignition timing dropped down to 6-8 during wide open throttle (vs 10-12). This KILLED my remaining 3 runs down to 16.3's.

So...what does all this mean? My main focus is on the first three runs because they are a direct comparison of my previous runs, without the 'data noise' from me testing the civic maf sensor. Remember, different dynos give different info? Well....some 1/4 mile tracks you will run faster than others. Englishtown Raceway is my slowest, Atco Raceway next then Cecil County Dragway is my fastest. My sig time is a Cecil County. So.....what have I been running at Atco before?

[email protected] 9/9/14
[email protected] 9/9/14
[email protected] 9/9/14
[email protected] 9/9/14
[email protected] 8/28/14
[email protected] 8/28/14
[email protected] 8/28/14

You can see the pattern. Not going further back since I didn't make the 'Myxal Vacuum' PRM intake back then. I can't see any significant spikes in my hp/tq from the Android app. My 60ft time is about the same or slightly better. When I swapped my PRM intake at the track before, it bumped up the 1/4 mile time by 2mph (2.5mph only once). I have a lot more testing to do. But that would tell me that my previous runs would be in the 87mph range and the throttle body would probably bump the mph up by another 1mph.

The ONLY thing I can see that caught my eye on the Torque app is the maf sensor g/s finally tops out at 100g/s. I could not hit that before. It would always hit 96-97g/s. So this means more air is coming in but it is VERY brief. I'll see this happen right around 6400-6500rpm. The rpm on the CVT doesn't stay at 6500rpm like I'd like. It'll hover there then slowly come back down and as I go through the traps, it'll be at 6200rpm or so.

It's very important that I start using 92 octane from this point on. When I was looking at my 92 octane runs, my ignition advance was between 15-20 with no significant power loss anywhere. Some power spikes at high rpm. So...I let the tank go empty on the way home and filled it with 92.

Until next time...........

BTW: My B.S. theory around this is that the throttle body is adding somewhere around 4-5hp. I was fooling with calculators and they were showing me if I wanted to go up 1mph based on my current curb weight and previous 1/4 mile times, I needed to make another 5hp. This is just in my head though. I can't feel it. Feel free to do your own tests.
 

Last edited by Myxalplyx; 10-10-2014 at 02:25 AM.
  #8  
Old 10-10-2014, 10:47 PM
Member
5 Year Member
iTrader: (1)
Join Date: Dec 2011
Location: San Diego, CA
Posts: 1,035
Sorry my brain has had a long day haha so whats the final results all bullshit aside? Are you running the same track better then your previous runs? So you ran this with the new throttle bore and intake?

I'm just curious to see what you might have actually gained and might consider giving the TB bore a try. Not a bad bang for the buck if all works well.
 
  #9  
Old 10-11-2014, 01:54 AM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Originally Posted by Rollerboots666 View Post
Sorry my brain has had a long day haha so whats the final results all bullshit aside? Are you running the same track better then your previous runs? So you ran this with the new throttle bore and intake?

I'm just curious to see what you might have actually gained and might consider giving the TB bore a try. Not a bad bang for the buck if all works well.
It's hard to say. I didn't make the intake that I have on it now until 9/10 (According to my drag ticket notes). When I tested the PRM intake against stock, it ran 2-3mph faster. And 1.5 mph faster than a modified stock intake or filter on the maf sensor. This test was at Cecil County Raceway. Last time I previously ran at Atco was on 9/9. No notes that I had this intake installed.

So...I can still install the stock intake box on and do a few runs next time out and put back on the PRM intake. That's a pain!

So..I can not say for sure if it definitely gained any hp/torque. I can say none was lost and no change in driveability. I have to dig in some more to see how I was running while 'street tuning' before and after. I rather have a drag slip to tell you guys either way, no Android Torque Pro software.
 
  #10  
Old 06-26-2015, 09:37 PM
kylerwho's Avatar
spoon fed
5 Year Member
iTrader: (11)
Join Date: Apr 2008
Location: Seabattle, Washington
Posts: 5,234
so Im reading over all these older threads again about throttle body sizes, since I have a secret project cooking, and Im very curious. Have you tried moving the maf to connect right after the 180 degree silicone hose? In my mind that would seem to keep a more steady air reading without having any turbulence back lashing from the throttle plate.
 
  #11  
Old 06-26-2015, 09:59 PM
Myxalplyx's Avatar
Member
Thread Starter
Join Date: May 2014
Location: Delaware
Posts: 1,843
Originally Posted by kylerwho View Post
so Im reading over all these older threads again about throttle body sizes, since I have a secret project cooking, and Im very curious. Have you tried moving the maf to connect right after the 180 degree silicone hose? In my mind that would seem to keep a more steady air reading without having any turbulence back lashing from the throttle plate.
I have not!

I would've done it if I noticed any drivability issues. Your thoughts on this makes sense to me as well and I swear I read it about that somewhere. Since I didn't encounter any issues with how the car drove and I didn't see anything weird with the maf sensor g/s vs stock (Looked the same on how it operated, just more g/s over the same period of time), I decided not to move the maf sensor upstream.

You'll notice that AEM and Weapon R (You'll see when Weapon R comes out with it) does exactly what you speak of.

On another note, my latest intake is actually on a straight section now, with no bent piping connected to it. Still no drivability issues from turbulence at the throttle plate.
 

Last edited by Myxalplyx; 06-26-2015 at 10:10 PM.

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.