3.2 Throttle Body Question

[drola]

my track car has developed a vacuum leak on the butterfly shaft of the throttle body. behind the springs.
is this something that can be repaired or am I better off just finding another one?
Is it worth having the tb enlarged while I'm at it? if so who can do this type of mod?

[wjdunham]

Steve Wong can do the widening mod, his web site has all the details. You send him yours and get a new one back. Given your wear issues it might be a no-brainier.
Bill

[HaroldMHedge]

I would speak with Steve Wong at SWChips. He offers throttle body enlargement as well a chip to take advantage of the enlarged throttle body.

Enlarged Throttle Body Conversion

Edit wjdunham posted first

[scarceller]

Other decent source for TB repair Maxbore.com throttle body boring service and repair very reasonable rates.

[mepstein]

Originally Posted by scarceller

Other decent source for TB repair Maxbore.com throttle body boring service and repair very reasonable rates.

Great price. I'm going to send him a 3.2 TB.

[Techno Duck]

I resealed mine using a generic viton o-ring kit. Its not too difficult to take apart, you just need some snap ring pliers.

I rebuilt a few 944 and 951 throttle bodies years ago using a kit from Arnnworx.. The 911 throttle body is exactly the same procedure wise. A good quality o-ring kit is kind of expensive... but honestly its probably less than $10 in parts to do. Unfortunately i don't know the sizes exactly that i used.

[danco_]

I sent in my throttle body to Steve Wong for enlarging on a stock 3.2 for no reason other than I thought it would be cool.

I had my mechanic slap it on and WOW, there was noticeable improvement in both throttle response and torque.


I mentioned this before, but I can best describe the new feeling as a if I had engaged a "sport button". The car pulls harder, quicker (or so it would seem), and more grunt down low.

I should also note that there was absolutely nothing wrong with the TB before I sent it in. It was one of those "while I'm in there" type of things. I do not regret it for a second.


I would think that the difference in a 3.4L build would be more significant.

GL

[cabmandone]

If you open up the TB wouldn't you need to remap the chip or risk running lean?

[stlrj]

Originally Posted by cabmando

If you open up the TB wouldn't you need to remap the chip or risk running lean?

No

[cabmandone]

It would seem to me that it would have to. A stock tune has to be based on fuel airflow and spark at a given throttle position and at WOT it would seem to me that it would use maximum airflow which has now been increased due to a more open throttle body.
What am i missing? It's not like these engines have the same intricate sensors that the newer engines do.
Hopefully Sal will chime in.

[Quicksilver]

Originally Posted by cabmando

If you open up the TB wouldn't you need to remap the chip or risk running lean?

The throttle body doesn't effect the mixture. That is controlled by the AFM. The only possible way the mixture could be affected is if it made the engine move more air than the injectors and the map in the DME could deal with. That isn't going to happen because the throttle body isn't the big restriction in the system.

[cabmandone]

Are you suggesting then that boring the TB has no real benefit? I'm just trying to figure this all out because I was considering boring my TB for what I have seen to be some performance gain through my search.

I'm going to PM Sal and get his take on it.

[scarceller]

During smoke testing it's normal for slight amount of smoke to seep past the throttle blade shaft. I'm not sure how much play you have on that shaft? If you can not notice the play with your hand trying to wobble the shaft in the housing I would not worry about this.

Intake restrictions in order of priority:
- The AFM is the first source of restriction and will have a pressure drop across it at hi-RPMs WOT above 5800RPMs.
- The throttle body is the next restriction and needs to be enlarged as much as possible in larger displacement builds like 3.4L or greater or a 3.2L that has been modified to increase airflow via cam changes and head porting. But for the money enlarging the TB is a good idea.

Other thing to check is the the throttle actually goes wide open with gas pedal at the floor, you'd be amazed how many cars do not. Check this!

[scarceller]

Not so, the AFM simply sees airflow and the DME matches fuel to that air flow. So even if you increase airflow at a given RPM WOT by 5-8% the DME will simply see more air flow from the AFM signal and command more pulse time from the injectors. Now if you increase airflow a lot like well over 10% you will max out the AFM signal and after the AFM pegs the mixture will start going lean. The stock AFM is good for around 12,000 grams/minute, plenty for the stock 3.2L at hi-RPMs.

Minor changes to air flow will not need much done in a stock 3.2L, boring the throttle body is very mild change at most it may help increase air flow at 6200RPM and above by no more than 1-2%, that's nothing. The stock AFM and DME will handle this without issue.

My MAF setup uses a wide open 80mm tube and the MAF is good for 22,000g/min! will even support mild 8PSI boost.

Originally Posted by cabmando

It would seem to me that it would have to. A stock tune has to be based on fuel airflow and spark at a given throttle position and at WOT it would seem to me that it would use maximum airflow which has now been increased due to a more open throttle body.
What am i missing? It's not like these engines have the same intricate sensors that the newer engines do.
Hopefully Sal will chime in.

[scarceller]

If you want to know if you have a restriction in the intake find this out the old school way. Simply plumb up a real good vacuum gauge and pull a WOT pull, have a passenger monitor the intake vacuum above 6000RPMs. If it's not near 0PSI you have a pressure drop and a restriction. Real good dyno tuners monitor intake vacuum with a transducer and graph it against the RPM during the pull. I have seen 3.4L builds at sea level and cold ambient temps (below 50F) show as much as -1.5PSI at 6500RPMs, that's 1.5PSI of free boost left on the table! Be smart here, do not assume, it's easy to test and check. Better yet find a dyno shop with a dyno operator that knows what they are doing and have a pulls done monitoring both exhaust pressure and intake vacuum.

But the 3.2L at sea level and 32F temp will likely never exceed -1.0 PSI at WOT hi-rpm. The goal is to achieve 0PSI in the intake at WOT across the entire RPM range, but getting numbers from 0.0 to -0.8PSI are typical and most engine builders and tuners don't worry much till they see more that -1.0PSI in the intake at WOT.

That 3.4L that showed -1.5PSI was then moved to my MAF setup and air cleaner and the number dropped down below less than 0.7PSI

If you are already well below -1.0PSI then boring and porting won't help much.

[cabmandone]

It doesn't look to me like boring a good functioning TB on an otherwise stock 3.2 with only exhaust modification is a good investment. That's what I was looking for. Thanks for your input Sal! Always appreciated.

[Steve W]

Originally Posted by danco_

I sent in my throttle body to Steve Wong for enlarging on a stock 3.2 for no reason other than I thought it would be cool.

I had my mechanic slap it on and WOW, there was noticeable improvement in both throttle response and torque.


I mentioned this before, but I can best describe the new feeling as a if I had engaged a "sport button". The car pulls harder, quicker (or so it would seem), and more grunt down low.

I should also note that there was absolutely nothing wrong with the TB before I sent it in. It was one of those "while I'm in there" type of things. I do not regret it for a second.


I would think that the difference in a 3.4L build would be more significant.

GL

+1 on what Danco described. On my totally completely stock 86 3.2, with just the installation of the larger bored throttle body was like hitting a big sport button. Stronger torque and throttle response everywhere, even more torque down at low rpm from right off the line. You can believe it or not. This was on my car that was already well dyno chip tuned and in good health, so it's not like there was something wrong with the car before the TB was installed. Below is the car on a Dynojet before the installation of the throttle body, with the stock exhaust and catalytic converter and muffler, engine all stock, still with the original stock TB, only a ported MSDS cone air filter:



I have not redyno'd the car since the installation of the throttle body, maybe later when I have a chance. Note the above is a SAE corrected Dynojet dyno chart. Be sure when doing dyno comparisons that you are looking at SAE corrected charts, what all racing sanctions require. STD correction (or Standard) is not the norm and will exaggerate the power numbers (unless that's what your tuner wants), such as the same dyno run above, but shown in STD correction below:

[KTL]

Originally Posted by Techno Duck

I resealed mine using a generic viton o-ring kit. Its not too difficult to take apart, you just need some snap ring pliers.

I rebuilt a few 944 and 951 throttle bodies years ago using a kit from Arnnworx.. The 911 throttle body is exactly the same procedure wise. A good quality o-ring kit is kind of expensive... but honestly its probably less than $10 in parts to do. Unfortunately i don't know the sizes exactly that i used.

Thanks for mentioning this. I went to Arnnworx's site and found there's a handful of different TB rebuilt kits Bruce offers. We gotta find out the details of his kits vs. the 911 throttle body so we can use the kit for our needs!

Throttle Body Reseal kits for Porsche