Throttle Body Overbore Teaser

[CandyRedRC46]

I just received a spare set of throttle bodies in the mail today. I am going to send them to maxbore.com Monday to be overbored, have the throttle shafts thinned and then filled with larger butterflies. I will be then port matching the boots to the throttle bodies and intake ports on the heads to the boots. Here's what we are starting with, I'll post up the new dimensions in a week or two when I get them back. I'm hopping for at least 42mm (as the entrances are already 40mm) but really anything over 36mm will be an improvement. (As the exits are only 32mm x 35mm)

[CandyRedRC46]

Ummmmm hmmm I need to look into this. Thanks for the heads up!

[Switchblade]

According to the member map there are at least 5 members in the Orlando area...

funny thing is CRRC, you don't show up on the map

Ummmmm hmmm I need to look into this. Thanks for the heads up!

You mostly use your mobile phone to reply ?

[CandyRedRC46]

Yup

[WackenSS]

Thinking of adding this to my list, but very curious about those Dyno numbers. Did you get it done?

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[CandyRedRC46]

I never dyno'd, being that my Rapid Bike Racing is auto tuning, but I did not notice a whole lot. I honestly haven't gone to the track since doing this, so I am not sure if trap speed went up either. I can tell you that there was no loss in low end torque and the powerband still feels great. I wouldn't be surprised if I picked up a few HP up top, but it was not anything dramatic, like I was hoping for, comparable to the Two Brother headers. At this stage in my build, I would say overbore throttle bodies aren't doing much, but I am sure they will shine later on with head work and cams (or on a force induction build). 

 

My offer still stands. If anyone wants to do a few pulls on a dyno, in the Orlando area, with a relatively stock VFR800, I will pay for your dyno pulls, so I can get a proper base line. (I am not going to pay for your tuning lol.)

[WackenSS]

I never dyno'd, being that my Rapid Bike Racing is auto tuning, but I did not notice a whole lot. I honestly haven't gone to the track since doing this, so I am not sure if trap speed went up either. I can tell you that there was no loss in low end torque and the powerband still feels great. I wouldn't be surprised if I picked up a few HP up top, but it was not anything dramatic, like I was hoping for, comparable to the Two Brother headers. At this stage in my build, I would say overbore throttle bodies aren't doing much, but I am sure they will shine later on with head work and cams (or on a force induction build). 
 
My offer still stands. If anyone wants to do a few pulls on a dyno, in the Orlando area, with a relatively stock VFR800, I will pay for your dyno pulls, so I can get a proper base line. (I am not going to pay for your tuning lol.)

Reason for asking is that i think i would rather start fiddling with the breathing on my supercharger engine than upping the pressure for now, and together with the "tyga" headers and some porting i would be making very good hp, for more $$ than just upping psi, but having a safer engine. And ofcourse rapidbike


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[CandyRedRC46]

Yeah thats a really good plan. I would try and source the cleanest set of used cylinder heads and throttle bodies that you can. Buy a new set of oem throttle boots and clamps. Send the throttle body and boots to maxbore. Send the injectors to precisionautoinjectors.com to be ultrasonic cleaned. When you get you throttlebodies and boots back, put the boots on the spare heads and mark the excess material with a marker. Then hold off until you get the race header. When you get the race header, put some paint on the flanges and press them on the exhaust ports, so you can see the excess material. Then take the cylinder heads to a known competent shop and instruct him to do a full port and polish and to remove all painted material. Also tell him that for anti reversion purposes, you would like to remove 0.5mm extra on the intake ports and leave 0.5mm of painted material on the exhaust ports.

 

Here is a great article on porting and anti reversion:

http://www.theoldone.com/articles/d16a_head/

Also you ideally do not want to remove material from the floor of the ports and should be removing from the roof.

I would normally add milling the heads, but thats a no go on both forced induction and gear driven cams. Definitely do check for run out to insure that they are not warped. This would be a good time to check valve clearances and maybe add new oem valve seals/guides/retainers if needed.

 

You might want to look into cam regrinds also. Being that you are forced induction, you don't really need much added duration or overlap, but I am sure some added lift would help in your goals.

[WackenSS]

Yeah thats a really good plan. I would try and source the cleanest set of used cylinder heads and throttle bodies that you can. Buy a new set of oem throttle boots and clamps. Send the throttle body and boots to maxbore. Send the injectors to precisionautoinjectors.com to be ultrasonic cleaned. When you get you throttlebodies and boots back, put the boots on the spare heads and mark the excess material with a marker. Then hold off until you get the race header. When you get the race header, put some paint on the flanges and press them on the exhaust ports, so you can see the excess material. Then take the cylinder heads to a known competent shop and instruct him to do a full port and polish and to remove all painted material. Also tell him that for anti reversion purposes, you would like to remove 0.5mm extra on the intake ports and leave 0.5mm of painted material on the exhaust ports.

 

Here is a great article on porting and anti reversion:

http://www.theoldone.com/articles/d16a_head/

Also you ideally do not want to remove material from the floor of the ports and should be removing from the roof.

I would normally add milling the heads, but thats a no go on both forced induction and gear driven cams. Definitely do check for run out to insure that they are not warped. This would be a good time to check valve clearances and maybe add new oem valve seals/guides/retainers if needed.

 

You might want to look into cam regrinds also. Being that you are forced induction, you don't really need much added duration or overlap, but I am sure some added lift would help in your goals.

Well lucky me then, as i bought a close to unused 98 vfr with severe frame breakage after only 18000km.

This engine will be my donor for all parts that is going to be modified.

All the details will have to come closer to actually doing it, and there will absolutely be questions emerging from this as there are plenty of unwalked ground on my part.

Awesome writeup of valuable info there mr. Candy

I was kind of hoping that sa1713 would finish the 5th generation modification thread before i start my own, but right now it can just as well be a race to the finish ?

Oh, and i need to finish rebuilding two pcs of aprilia sxv 550 engines first, at least once

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