Lol. The guy was very cool about it. I know it's "pointless" but I was curious to see if my mods were doing anything. After our quick little burst he said "that's nice". So even though I missed a shift I was right with him up till then. I asked how much he was boosting and think he's said something like 320 to the wheels. Wicked little cars those Subies are. Besides the Subies guys know their cars are mean little bastards, especially the STI's, they beat up on all sorts of cars. I was happy to be able to just keep up with it.
You don't need to them matched to the plenum because, the opening on the plenum is 58mm and the largest the tbs can get ported is 57mm through the center. You'll see when you pull yours off.
Little update. Had the opportunity to test my ported tb's on another car that had stock tb's. We did a couple of before and after pulls on the dyno, and my taper ported tb's were good for an additional +4/hp to the hubs. Again, GREAT WORK Rob! I'm still of the opinion that we can get another 1-2/hp out of these, because the tube from the MAF to the TB necks down. That tube is another bottle neck we need to get rid of. I'll post up some pics later so you can see what I'm talking about.
1000/2 (breathing rotations per minute) * 3.4 litres = 1,700 litres per minute, but only if the engine is 100% efficient at breathing. A diesel (i.e. unthrottled) engine would be consuming this much air. However, the throttle plate in the system lowers the amount of air being consumed to about 10% of the above computation: or 170 lpm. I could moderate this even more by adding in the 70% volumetric efficiency at idle,... but why bother. 1 liter of air at STP weighs 1.29 grams, 170 liters per minute weights 219.3 grams per minute. At full throttle and 7000 RPMs (abut 85% volumetric efficiency) 14,450 litres per minute * .85 * 1.29 gr/litre = 15,844 gr/minute = 16 Kg/m of air. This requires 1.11 Kg/m of gasoline (14.2:1 stochiometric mixture) per minute or about 1.46 litres per minute, so your 17 gallon tank would run out in 64 miinutes. I can get 77 minutes on 17 gallons in my F355 on a race track, so we are in the right ball park. One can get a certain amount of power with overly large air intake systems. One can get a little more power (15%-odd) with a carefully tuned intake system. These carefully tuned intake systems are invariably smaller than a schoolbus and certainly larger than the air cleaner on a 57 Chevy.
Since I had the tb's and the mafs off, I wanted to see how they mated up. The opening of the maf is 65mm, and the tb fits right inside it. You would think that the maf opening is 65mm all the way through, but it's not. Once I had the tb inside the opening, on the front of the maf, I opened the throttle plate to see how the transition was. Even though the opening of the maf can fit the tb inside, the maf is only 62mm through the center, where the hot wire is located. Rob's porting at the front of the tb is just a tiiiny bit bigger than the centerof the maf. That is a good thing in my opinion, because that means there is no restriction when compairing the tb to the size of the maf. Image Unavailable, Please Login Image Unavailable, Please Login
The next thing I did was compare the exit side of the maf to the inlet side of the tube. You can see that the inlet side of the tube is just a hair smaller than the exit of the maf. Even though the inlet on the tube has a bit of a radius to it, it's still smaller. That is not good in my opinion, because it can cause turbulence of the incoming air, and slow it down. Then we also has the issue of the cooling fins, on the top of the maf (you can see them better in my previous post), right smack in the way of the incoming air. More stuff to hinder the velocity. I'm still on the fence of whether or not to cut those out. Are they REALLY necessary. I'm not so sure they are, so I'm leaning towards cutting them out. Image Unavailable, Please Login
Now here is where our next bottle neck is. I connected the exit end of the tube to the inlet side of the tb. The tube shrinks down BIG TIME! On the stock stock tb it doesn't matter all that much, because the stock tb is only 54mm at the throttle plate tappers out to 57mm. But on my ported tb's that is a VERY noticeable difference. You can see how much smaller that lip is. Because of that lip, and the sharp edge at the end of it, it creates a toroidal vortice which slows down the air = not good for making power. So the next thing that needs to get tackled is that throttle body tubing. We need to have one that is a clean 62mm from the exit of the maf to the inlet of the tb. Oh yeah one more thing. A larger tb tube will ONLY work of your tb's are ported the way Rob ported mine. Because of you try to put a bigger tube on an unported stock tb you will actually LOSE power, due to the bigg hole hitting the lip of the smaller hole of the stock tb. So again, a larger tube will only work on a ported tb. I think a 62mm tube will really let the ported tb perform better, and be good for another 1-3/hp at the hubs. Image Unavailable, Please Login
I was extremely alarmed reading through this thread. I would just like to explain a few things; Throttle bodies are not Venturi valves. The different internal diameters are mainly due to manufacturing easy or packaging. Don't ever bore a throttle out. There has been a lot of calibration work between the OEM and Tier 1 to size the bore appropriately. Increasing the size has the following issues; 1) Increases the Airflow vs Throttle angle (TPS voltage). This is known as flow progression and will affect calibration if not flip codes due to confused MAP and Lambda sensors 2) Requires a new shaft or heavily modify the existing. Hard to control leakage if you don't get it right since a lot air passes between the blade and shaft (a lot in respect to minimum controllable air at idle). 3) Requires a new blade with the correct edge angle. Angles vary and so do the tolerances. Modern blades are 4-8 degrees and +/- 0.005mm of the OD. If the angle or diameter are incorrect, there is risk of excessive leakage or worse, a stuck throttle. 4) Reseting the blade to the correct angle at idle. Too low and it will stick, too high it will leak excessively. All that is gained is a reduction in the top end (WOT) pressure drop which increases the Effective Area BUT, it is more often than not that the restriction (choke or max pressure drop) is at the valves and seldom at the throttle. PS. Cleaning the throttle is also not recommended although many garages and mechanics practice this. The deposits (carbon, PCV etc) are a free and effortless way to reducing leakage.
Too late, Been there done that, glad I did it, wouldn't hesitate to do it again, and recommend others do the same. That has no affect on our 348's as they do NOT use a map sensor, but DO use mass air flow sensors. The Lambda sensors (aka O2 sensors) only relay what they read in the exhaust stream back to the ECUs. The ECUs are self adaptive, and also "learn" as you drive. My car has had no problems running, nor adjusting to the extra air. Rob did an awesome job on my TBs. He used the stock throttle shafts, and did modify them per my request. The throttle bodies on our 348's control the idle air via a screw on the side on the tb. Also the ECUs control the idle speed via the idle air control valves, which completely bypass the throttle bodies and fee directly into the plenum. Besides, Rob tested the close flow of my ported TBs, and they were within with 0.1/cfm of the uprooted TBs, and actually where a tiny bit tighter. Rob also made me a new "blade"/throttle plate, and if I'm not mistaken put a 7° angle on it. As far as it getting "stuck" I took care of that by adjusting the throttle stop o my TBs. Again, took care of that by adjusting the throttle stops No reduction in my top end at all. Matter of fact my ported TBs are good for an additional +4/hp to the hubs, as verified by doing before and after dyno pulls. Now the intake valves are a completely different thread altogether. Welcome to FerrariChat, but please, next time read the entire thread before you decide to "enlighten" us. Rob is a VERY skilled professional machinist, and knows what he is doing, and did an OUTSTANDING job porting my throttle bodies. Only question is, who's next.
Thanks Ernie! You are the only Ferrari customer so far but I still do a set a week on average for the Z guys, they love them. Rob
I can't believe that no one else from the Brotherhood, has man'd up and sent you their tb's to get ported? Cummon you big chickens!
Rob, A little OT but do you know anything about the reverse of porting making restrictor plates and how that effects things?
A lot of cars depend on a bit of leakage to run right. First thing I do for a car that won't idle. Often a shot of carb cleaner does the trick.
I have not had personal experience but no doubt a gradual reduction to the regulation size is better for flow than a "disc" shoved into the airstream. It's the same minimum opening but in a gradual reduction the air won't hit a wall and be forced to turn sharply to make it through. Rob
Hi Ernie, I did read them and read them thoroughly. BTW, I was referring to PRESSURE DROP reduction at top end. Less Pressure drop means more flow. A double negative and I apologies for the confusion PS. What did you do about interface between the throttle outlet and manifold? Their diameters are usually within 0.5mm of one another with the positional tolerance making up the difference. An abrupt change in diameters (unlike the transitional you originally had in the bore) will certainly add the Pressure drop you are trying to remove. Additionally, I have to add that Rob certainly does great work. The part looks amazing. Anyway, I'll just give you some background into my comments. I have designed, developed, tested and manufactured throttle bodies for the past 16 years, both mechanical and electronic (ETC, ETB) for Ford, Chrysler, GM, Volvo/Penta, Holden, Daewoo, Nissan, Isuzu, Mercedes, and yes, Ferrari. I have worked in three continents, hold 11 patents (all throttle body related) and currently developing 5 electronic throttle bodies for the global market. I have throughout my career been asked the same question and have always answered it the same way. We spend millions of $'s testing materials, tolerances and airflow.....especially airflow. In fact I have amongst the best throttle body flow benches in the world (150 HP, 15 sonic nozzles, 0.5% max. error) commissioned out of Colorado. I also have a Superflow 1020 for quick readings. The "flow progression" curves we develop jointly with the OEM are set and agreed to regardless of their presumed inefficiencies. The important point is that they are calibrated this way and must be maintained this way throughout production. Any "tampering" (and please don't take it negatively) is unintended and not always positive from a systems perspective. Remember, by increasing the diameter, you are adjusting the entire curve and not just the top end. If you are achieving the same "minimum controllable" airflow (otherwise and mistakenly known as "idle airflow") with a larger blade, it's likely that your gap has been reduced and you risk contact during thermal contraction. Not a good thing. If you have solved this problem already, then good for you because we spend lots of $$ trying to do the same. Ferrari pays a lot of attention to performance. More so than quality. In fact they asked for minimal DV testing but luckily for them, they practically receive the same throttle body as Mercedes, GM or Chrysler who demand extensive testing. Anyway, keep doing what you're doing if it means sucking the few HP's you're searching for. It's just not what I would do or recommend doing.
The very back of the throttle body, the part that mates to the plenum, is 0.5 mm larger than the ported straight section. The opening on the plenum is actually 58.5mm. I also had the back side of the tb openings, on the plenum top, radiused so that there was a gradual transition into the plenum. Rather than the sharp angle on the stock opening. No toroidal vortices feeding the plenum. So from the opening of my tb's to the back side of the plenum inlet it goes: 62mm (actually 62.5 at the veeeeerrry edge) throttle body opening, Down to 57mm at the throttle plate, with a very nice smooth taper. Thank you very much Rob. , 57mm from the throttle plate to aaaaaaalmost the back of the throttle body, 57.5mm at the very outer edge of the back of the tb, 58.5mm plenum opening, to the radiused inlet to the plenum. I know you're probably pulling your hair out now. Since this is how you make your living, and have FAR more experience at this than I do, I'm just a Stooge looking for more power, what do you recommend? I am thoroughly convinced the 348 is choked off big time, and needs more air. I have a few other ideas I'd like to bounce off you if you don't mind.
No probs Ernie. Honestly, I'm not a gear head in that regard. It's like the old proverb "a cobblers son goes bare foot".....or something like that. I'm more interested in the science, engineering and thermodynamics of the system. Just as interesting to me is designing in the robustness and manufacturability of such components. With the latest Electronic Throttle Bodies, they can seriously be described as swiss watches dragged through gravel due to their complexity, precision and toughness. Unbelievable pieces of equipment and the way they are integrated into the entire Engine Management System is nothing short of remarkable. In fact some modern systems can fully open and close the throttle in less than 0.15 seconds while you're driving just to check functionality. The driver of course does not notice this because spark and fuel is adjust simultaneously. Incredible stuff. On the F360, the ETC's were such a drain on the ECU that they adopted a master-slave control strategy. In essence, these systems are extremely complex and finicky. I would not mess with them, not in a Ferrari but if you would like to run your ideas by me, please do. I'll be more than happy to help you where I can.
Great. Oh and by the way, the throttle bodies on the 348 are old school. They open via a cable, and close via a spring. No fancy schmancy fly-by-wire tb's on our cars. All mechanical. Ok here goes. Our 348's have dual plenums. They are run as two separate 4 cylinders. I have seen a 348 with a custom single plenum. When that single plenum was tested on the engine without running any boost, it made more power than the stock engine. However the plenum was designed for a boosted (turbo) application. So in a pressurized environment the volume inside that particular plenum would be fine, because it could help reduce the turbulence. But on a naturally aspirated application it could be too big. So...... Do you have access to, and would it be possible, to test different plenums designs in CFD to find what would be the optimum plenum top shape, before I drop the money to get one made? I'm curious to see how the single plenum spreads the air across the runners for 8 cylinders, as opposed to only 4 cylinders. How the single top will flow with the dual throttle bodies mounted on the sides (as they are on the stock tops) vs mounted at the rear, or ends of the plenum. Is that something you can help with?
Mechanical throttles indeed. Also, check the linkage between the cable and shaft. The purpose of this is to introduce a type of progression to your throttling. Another way is to use a curved cam that the cable wraps around (snail cam) or actually machining in a profiled bore (Progressive bore or S-bore). Check out some modern GM engines and see how complex the machining is inside the bore. I bet even Rob would be impressed. Not many machines in the world have the capability to do this. I use Chirons. Now on the plenum. Plenums are typically 1-1.5 x engine capacity in regard to volume. You have 2 plenums but they are actually connected through that little butterfly valve you see through the center. The valve opens depending on the engine RPM (Variable Intake Manifold) changing the volume in order to flatten out the torque curve. It relies on the principle of Helmholtz resonance. http://en.wikipedia.org/wiki/Helmholtz_resonance Low RPM, Long runners High RPM short runners This is the main reason race engines/motorcycles have multi throttle arrangements. So if you restrict your volume to one size, you risk adjusting your Torque curve which in turn affects your Power curve (P=T x Angular velocity or RPM). You may see improved top end Power but I bet you will compromise low and mid range output. The best software I have used was GT Power on the 2.6L High Feature V6 Turbo engine used on the Saab Aero but that was 8 years ago. http://www.gtisoft.com/ This software allowed us to balance the runners (GM spec. is 10%, we met 5% Runner to Runner) by efficiently placing air deflectors to meet this target. Something that you may need to do to ensure adequate balance. Pay close attention to this. You don't want to continuously run too lean or rich in your cylinders. Also for a PFI (Plenum Fuel Injection) engine, you want some level of turbulence for adequate fuel mixing. Another important fact and against popular belief, rough manifolds run just as well as smooth (boundary layer effect). Now back to your request. We contract this out. I can get a quote for you but I'll tell you now, it's at least $200/hour. Do you have 3D models? If not, I can help you there, just get me the dimensions and rough geometry. How many iterations do you want to perform? Hope this helps.
