Whoo Hoo! I have my bored out tb's. They came out great Rob. There sure was a whole lot of material for you to open up. The mouth of unported tb was 57mm, actually it was closer to 57.5mm, but I just rounded it down to 57mm. I told Rob to open it up as big as he safely could, and he did not disappoint. The NEW opening is 62mm and tapers down to the previously discussed 57mm with a nice smooth transition. Yeah buddy, that's what I'm talking about.
Installed the tb's today. The opening came out very nice, as did the throttle plate and shaft. Would you just look at all that ROOM! Image Unavailable, Please Login Image Unavailable, Please Login
The rear of the tb still had a little bit of a lip from the factory tapper. From the throttle plate all the way back it's a nice 57mm opening, with that little tapper, which is fine because it "helps" smooth the transition from the 57mm bored to the 58mm opening on the plenum. The little lip is about 57.6-ish/mm. Image Unavailable, Please Login
Only thing I had to do was make a half turn adjustment to the throttle stop screw. I didn't want the throttle plate stopping on the inner walls of the tb, because I don't want it to wear a groove in the walls. You can see the tiny bit of space between the screw and arm of the tb. Like I said, I did a half turn adjustment of the screw until it touched the arm, and then played with the throttle to make sure it was stopping on the screw. Image Unavailable, Please Login
I mentioned before that I found some other restrictions in the intake track. The first are the screens on the mafs. Even though the opening on the mafs is roughly 65mm the inner diameter of the metal ring the screen is attached to, is only 60mm. So I pulled the screens of the front and back of the mafs. To do this you simply: Hook the retaining clip and pull it out. Then .. Turn the MAFS over and the screen should just drop out. If it doesn't you can hook the metal ring attached to the screen and pull it out. But it should just drop out. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Here is the mafs with out the screen. Ah, that's better. The opening is better but, I mic'd the inside diameter of the hole where the sensor stuff is located, and it came in at 62.5mm. So by removing the screen's I get got rid of a 2mm obstruction in the path of the air. I know the screens help "smooth" out the air flow, but the metal ring the screen is attached to is messing up the air flow. Both on the front and back of the mafs. If you look closely you can make out the very thin sensor wire. Image Unavailable, Please Login
The other bottle neck is the feed tube from the mafs to the tb. The first pic is the opening from the mass air flow sensor. I couldn't get the calipers of my mic in far enough, but just by eyeballing it, the opening is around 60mm mafs side. Then the next pic you can see the opening at the throttle body. That came in at 55mm on the inner opening. You can also see the nipple for the oil vapor recovery tube sticking right in the path of the air flow. I pulled that out, so that the tip was flush with the id of the tube, before I installed it. Next thing I have to figure out is how to get bigger tubes, with the proper bends, nipples for the iacv and oil vapor lines, to replace the stock tubes. Image Unavailable, Please Login Image Unavailable, Please Login
I installed everything, fired it up on the first shot, and it idled just fine. After letting the Motronic's go through the warm parameters the idle settled right at 1000/rpm. Nice work Rob. Then I took it out for a test spin. I can say that I noticed the throttle response is better. From a dead stop I don't have to push the peddle as much to get it going. On the highway it seems to like the bigger tb's. Seems a bit more crisp. As luck would have it I encountered one of the new M3 coupes. I know those cars are no joke, so I wanted to see how my newly ported tb's would perform, coupled with my other mods. They did not disappoint. To my pleasant surprise I was able to keep up with the M3. I don't know how hard he was on it, but let's just say we weren't going slow. It's a good thing when the engine can breath better, and I'm pleased with my ported tb's.
Nice work! I have been running without the sceens all summer with no issues. I know that some folks cut off the cooling fins inside the MAF to provide better air flow.
cool Ernie....seat of the pants is what it really boils down to....i've done tons of car mods in past that several didn't appear to have any substancial affect, ut they were just a piece of the plan, and the fun is in doing the work DIY looks like the directional fins inside the MAFs are a seperate molding, might be removable with some disassembly? a dremel should do the trick to remove/smooth out the ring-land of the MAF screens....at the minimum it would remove a boundary layer ring forming and reducing ID of smooth flow IMO scrooge on man, scrooge on! LOL
Yeah ..... I've heard about cutting out the cooling fins, but I don't think I'm gonna fool with those. I need to figure out what to do with the connecting tubes first.
Looking good you guys. Ernie, I forgot to mention that my MAF screens have been out for a couple of years now.
I knew you had yours out, I just never messed with mine because I didn't feel like it. What surprised me was the i.d. of the maf is only 62.5mm, and the i.d. of the metal ring for the screen only being 60mm. I thought it would have been closer to 64-65mm. Plus all the sensor stuff inside makes the inner volume even less. The next bottleneck we need to deal with is the connecting tubes from the mafs to the tb's.
Just got back from a short drive. Encountered a STI on my outing and did a quick little run with him. To my surprise I was not left for dead, and was able to keep up with it. Though I did miss a shift and he pulled a car length on me when I did. Those Subies are some quick ass little cars, and out right terrors with mods. Anyway, I'm glad my old girl is able to breath better now.
Ernie, New you have really done it. Your talk about airboxes, throttlebody's and plenums got me thinking. So bad, i can't sleep at night... ( remeber I've got limited technical knowledge). Our F348 has a 3,4liter V8 engine, so every rotation 3,4 liter is replaced. It is of course a 4 stroke motor (1 down=suck, 2 up=compress, 3 egnite=down, 4 up=Flush) so every 2 rotations it sucks in 3,4 liters of air . In my simple understanding that is at idle ( say 1.000rpm) 1.700 liters of air a minute! What? That's enough to suck in road debriss and small pet's ! At full throttle that would be 14.450 liters every freacking minute! Forget about the heavy gearbox, the suction created by the airflow alone would propell my car at the speed of light! Why don't we have an airbox at the size of a truck, with tubing the size of schoolbusses and a throttlebody as big as a garagedoor? Obviously I've missed the boat somewhere... Can you set me straight? Remeber I use pain-medication and, beeing the holidays and all, a light abuse of alcohol has taken place. Oh and nurse, I am ready for my medicine now... Regards, Ben.
Dayum Ernie. Why do you have to go racing with a subi for? Not only is it pointless, you missed a shift and now he's got bragging rights to "beating a mean looking Ferrari fresh with a ported intake." Sheesh, as if we 348 owners don't even have enought disrespect to worry about.
Because the factory designed them too small. But keep in mind that back in 1989 when the 348 was first introduced 300hp was a lot of power. In my limited Stooge understanding all an engine is, is a pump that converts explosive energy into torque. Each cylinder has a certain "ideal" power potential based on the volume in each cylinder, as you have figured out. The more efficient you make the process, the more you are able to reach the natural power potential of the cylinder. In short, the more fuel/air you can pump into the cylinders, the bigger the bang of the internal explosion, and the more exhaust you pump out, the more power it will make. The speed at which you are able to do this will determin how fast it makes the power. Think of it like filling a bucket with water. But when filling the bucket you can only have the water turned on for :01 second. The bigger the garden hose the more water you can get in the bucket. Then fill it up with a fire hose, it will get MUCH more water. However the bucket can still only hold a certain amount. Does that make a little more sense? There are all sorts of very complicated mathematical formulas that can explain this in detail. But that would be better left to the math experts to explain.
