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Discussion Starter · #1 ·
For those of you looking to squeeze every last pony out of your VR, I highly recommend cleaning up your TB like I did. Starting with that old EC article on Velocitys old OBD1 TB's I narrowed down the shaft by 150 thou, counter sunk the screws, enlarged the opening, and blended the ramps. In all it took about 10 hours of work with most of that hand polishing.
I started by indicating the TB on the mill so that the shaft was parallel. Using a 1/4" 4 flute end mill @700 rpm I took 5 thou cuts out of the shaft (obviously held open) until I had taken out 75 thou per side. Set your dials on each side of the table so that you stop at the same place each time. Then I threw it under the drill press and counter sunk the holes so that the M4 flat screws would sit flush to the shaft.
Next was the time consuming part. I carefully knocked the edge off of each ramp with a half round finger file being very careful not to remove any material from the ramps themselves. I then got the Dremel out and with various bits blended the ramps into the body so that the transition was smooth. Again, I did not alter the ramps in any way. Using the Dremel still with sanding rolls I enlarged the opening on the intake side and blended that into the body as well. I also removed the outter flange so that my Samco coupling would seal tighter to the entire TB.
Finally, I spent 4 hours sanding the inside of the TB with some 220 grit emery cloth until it was all blended and smooth with a slightly rough texture. Cleaned it with ethanol, put some permanent strength locktite on the screws and got ready for the test.
Using a bunch of Jeep freaks who had never worked on a VR before, we conducted a little test to eliminate placebo effect. We had 3 TB's, the stock clean one on the car, a gunked up stock one, and the modified masterpiece. Two of us would work on the Jeep out back while the other guys installed one of the TB's without telling us which one was in to eliminate bias. A dyno would have given actual numbers but not how responsive the engine felt, so we decided this was better, and cheaper.
We did this all afternoon and the results were good. The stock clean TB felt normal, the gunked up one felt sluggish, and the modified unit was extremely responsive and pulled harder, longer. There were no bucking issues and part throttle driving felt crisp and clean.
I'm not sure what shape the plate itself should have, so I left it alone for now. If anyone understands airflow and has any ideas, please chime in.
I'd be willing to do this for the right price if anyone else wants one, or wants more details on how to do it themselves.


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Modified by AGRESIVE at 8:18 AM 5-30-2004
 

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Discussion Starter · #6 ·
Re: (Atl_GTi)

Increasing the bore of the TB or removing the ramps is what causes the bucking issues with the OBD2. The partial throttle maps in the ECU can't deal with the extra airflow. At WOT mine allows more more air without effecting the airflow at partial throttle. Blending the ramps smoothed the airflow which is what makes it more responsive.
 

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Re: (AGRESIVE)

ohhh ohhh im very interested. please write up a detailed how to. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif
 

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Discussion Starter · #8 ·
Re: (Atl_GTi)

I think I pretty much covered the how to, if you have any specific questions I'd be happy to answer them.
Some close ups of the ramps to show the blending.

 

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Re: (AGRESIVE)

I have an OBD1 throttle body, and that looks absolutely fabolous compared to my garage porting. I had to be careful not to remove too much material on one ramp or it would've went through to the other side. Man that looks so nice, I'd be interested in sending you one as well.
 

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Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (AGRESIVE)

It's all in the details...you've got some good ideas. If you get some dyno runs that show improvement, I may be interested.
 

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Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (FatSean)

looks very nice. ive got one like that but it is undrivable to say the least.i couldnt even use it for wot drag racing. instant cel too.looking a little closer i think my ramps might be a little smaller than yours. ill try another one. http://****************.com/smile/emthup.gif


Modified by race-shop joe at 2:20 PM 5-20-2004
 

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Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (AGRESIVE)

Looks good, glad to see people tinkering with the OBD2 TB and doing away with some old VR6 "myths"... seems to be alot of that going on these days.

The throttle plate shaft and screws reminds me of the old Velocity/Vdubz OBD1 TB's.
Bill
 

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Discussion Starter · #13 ·
Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (race-shop joe)

Quote, originally posted by race-shop joe »
looks very nice. ive got one like that but it is undrivable to say the least.i couldnt even use it for wot drag racing. instant cel too.looking a little closer i think my ramps might be a little smaller than yours. ill try another one. http://****************.com/smile/emthup.gif
Modified by race-shop joe at 2:20 PM 5-20-2004

Yeah, like Sean said, it's all in the details. It's very easy to remove too much material in there and get carried away with the blending. I was extremely careful not to remove any material from the top of the ramps and only blend the machining line at the bottom. If you look around the edge of the plate you can see that there is a gap of only 10 thou when closed, and near the end of the ramp it increases to only 16 thou.
The surface finish is important too in that it isn't polished smooth, hence the scratch lines from the emery cloth. 10 hours is a lot of time for such a little part, but well worth it in the end.


Modified by AGRESIVE at 3:12 PM 5-20-2004
 

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Discussion Starter · #14 ·
Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (billyVR6)

Quote, originally posted by billyVR6 »
Looks good, glad to see people tinkering with the OBD2 TB and doing away with some old VR6 "myths"... seems to be alot of that going on these days.

The throttle plate shaft and screws reminds me of the old Velocity/Vdubz OBD1 TB's.
Bill

That's where I got the idea from, the September '99 issue of European Car where Jeff said that because the shaft was laser welded on both ends it wasn't worth the minimal gains. Milling that shaft down is not easy though. Next time I'm only going to go 70 thou on each side to leave a little more meat in there, the holes get awfully close to the edge when counter sinking the screw heads.
Damn myths just won't die sometimes.
 

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Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (AGRESIVE)

Hey aggresive how does the rough finish make a difference? Does it help with airturbulence in some way? Great job by the way, any interest in playing with a OBDI throttle body?
 

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Discussion Starter · #16 ·
Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (MySunRoofWorks)

Sure, I'm interested in helping anyone get the most out of their VR.
Got this off the GTI-VR6 list this week and think it explains things well.
Quote »
I don't know if anyone has thought about this but some texture inside the manifold might be more beneficial. Referring back to the reason golf balls are dimpled, drag due to airflow separation or "induced" drag (think turbulence rising off the surface especially around curves in the plumbing) steals much more energy than parasitic drag (think friction between the air and manifold surface). The roughness may be designed into the interior wall to create what are called boundary layer turbulence which form a low pressure area, which therefore helps to "suck" the flowing air into it's correct path. The ideal may be smoother than stock but I doubt F1 cars intake manifolds have a mirror finish.
 

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Re: More VR6 machine shop fun with OBD2 VR6 Throttle Body (need_a_VR6)

nice. if youre interested. id ship out mine to have you do some work. pay you handsomely


i bought an xtra TB last summer and messed with it some. blended both ramps as best i could. I think i took a little too much off....initial throttle response was great...but when u go WOT while rolling......it hesitated a bit. Stock TB worked much better. id also be interested in some type of dyno comparing an aftermarket TB, Stock, and a DIY ported one
 

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Re: (AGRESIVE)

Quote, originally posted by AGRESIVE »
Increasing the bore of the TB or removing the ramps is what causes the bucking issues with the OBD2. The partial throttle maps in the ECU can't deal with the extra airflow. At WOT mine allows more more air without effecting the airflow at partial throttle. Blending the ramps smoothed the airflow which is what makes it more responsive.


If you want some software help let me know....
maybe some 'sweat equity' trade?
(I would need a TB for 'testing'
)
I got 42# inj. to run perfect part throttle, adding the TB
shouldn't be a show stopper. http://****************.com/smile/emthup.gif
Jeffrey Atwood
 

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Discussion Starter · #20 ·
Re: (Jefnes3)

All IM's replied to.
I'm going to need some TB's to be used as cores if anyone has some in perfect shape kicking around and for sale at a reasonable price. Let's get these VR's as strong as possible to whup on all those 1.8 T's and honda's.



Modified by AGRESIVE at 8:22 PM 5-20-2004
 
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