Ernie, The 80% duty cycle is the average estimate for normal operation. You know that during your driving you are going to be pushing the duty cycle up based on fuel demand or down. Racing applications really push the duty cycle. I have been told that we can move the duty cycle up a little without damage because we don't drive the cars at 10/10ths all the time as on a track. Besides, worst case is you burn out an injector and its like $25 to get another one from Oside. I want to know how far we can push these new injectors. Yes, I have a set too, but they are not installed. I find it very interesting that Tim's car showed the same results as yours. So that pretty much tells us the engine isn't getting enough fuel for the amount of air the plenum can deliver. That also tells me that the parts upstream of the plenum are capable of handling the increased capacity of your plenum. Same air delivery hoses, same air box, same MAFs, same interim tubes up to the TB's. Honestly, I don't think you are going to get the 2.7 chipped to where you need it. Stand alone ECU is the answer.
I too bought a set a few days ago. I couldn't turn down the price for them. I'm hoping that the stock 2.7 can adapt to a better designed injector.
80% or whatever rule of thumb is not because of concern for the injector. You can have the injectors commanded to 110% for a lifetime and the first thing that will suffer is the engine. Point is, if you tune it on a dyno at say 2000ft density altitude and you can meet target air fuel ratio but end up with injector duty cycle at 100%, at that very point in time and those conditions you really have no worries. Dyno run is at wide open throttle and to max rpm. No change in driving style will change max injector duty cycle. What will change it is ambient conditions. If you pull it off the dyno and on to the street where it's 30deg cooler and density altitude is -400ft, now the injectors that were 100% on the dyno will be commanded over that and the engine will run lean. This is the reason for max desired duty cycle. To give you enough overhead to deal with any ambient condition. As for the Motronic mapping, not sure how it compares to most of the stuff I deal with but most ecu's will have an injector flow rate table. (So, if upgrading injector size you simply alter injector flow rate rather than having to scale every fueling based table by that percent). If the tables are accessible the 2.7 Motronic is 100% capable of dealing with all of this. All it comes down to is accessibility and the willingness to invest the time.
Yeah for sure, I am thinking of building a pro stock style manifold out of oval tubing for shats and giggles. Would love to get a few dont do this to it This 348 is as simple as a ford small block.
Yes but the professor knows his math. He can get you close empirically and save you lots of time. The Smokey Yanick method works to...
Yep Uncle Smokey knew how to get it done. I'll order a few gallon jugs of epoxy putty to make my planes, grind them away and try another way
It's my feeling the open plenum has relieved a lot of the induction strain placed on the factory intake parts (mafs, connecting tubes, throttle bodies). Because the induction is now being distributed through both intake paths the upstream restrictions have much less affect on the breathing. However they are still a restriction that needs to be resolved. The easier time the engine has ingesting and expelling air, the easier it will be for it reach its full power potential.
So Ernie, Are you now at a point where you need to (1) find bigger injectors and (2) remap the ECU to control those injectors??? Tim...since you are in the ECU can you change the map injection cycles to fit new injectors? I'm almost scared to see what's next. I'm sensing twin turbos and intercoolers!
For absolute certain we are at the point that the ECUs MUST get remapped. The big unknown is how much room the stock injectors have before they are tapped out. But I already have a set of slightly bigger injectors, that do a far better job of atomizing fuel, ready to get installed on my 348. We just need to sit back and see what Tim can accomplish with the mapping on his car. Then see what it does on the dyno. The only things proven so far is that the SW intake manifold allows the engine to breathe much better. That the stock open loop ecu mapping does not supply the fuel the engine is now demanding. That this manifold bolted on to two different f119s causes the engines to run very lean at full throttle. Yup it needs tuning, fuel, and ignition timing. I'm waiting to find out exactly what the SW manifold is capable of before I proceed with further modifications. The key to finding out is in the tuning.
I had a 355 out yesterday The 348 has so much a better powerband for a street car. We must pay attention not to turn it into a 355 style motor
Now Ernie has more air in and the exaust is being taken away faster. do we need to think about a hotter coil and larger gaps on the spark plugs. More fuel and air needs more spark for a more efficent engine ?
Awesome guys. My retired engineering professor dad reminded me that flow velocity is also important and might be a major reason the F119 was dialed down. The drive-ability issues and fuel efficiency (Motronic really) were probably "settled for" at the low end and breathing was left on the table. Yes we don't want to turn this into a 355 but power on the big end will be worth it. My supercharged Miata loses some power and torque due to parasitic loss on the low end out of boost (less than the alternator haha). Also, my new 3 inch aluminum intake pipe allows more air but it's travelling slower out of boost so you see a torque and power loss on the low end there too. I can brake the tires free of course, but it's easier to keep traction on launch. That's probably all conservative throttle anyway Keep it coming. I want to see the new injectors and lower plenum.
Yes, but remember when the motor is running closed loop it usually has between 7% and 14% authority to trim the injectors based on the O2 sensor readings. So, you can run a larger injector (to a point) in closed loop (idle and usually below 4000 RPM and WOT) and the ECU will attempt to correct the A/F ratio back to what it was supposed to be to achieve best emissions. BTW, you could use a really dirty trick to change the flow rate, which would be a rising rate fuel pressure regulator (which is often seen on boosted motors). Since the fuel pressure is referenced to the ambient pressure, using a vacuum signal can accomplish the same goal, all you have to do is get the curve right. Bell Engineering in San Antonio, TX makes these and I believe that they may have one that would do exactly what you need without reprogramming the ECU. http://www.bellengineering.net/templates/BEGi_6_5/images/Manuals/FMU_Instructions.pdf Tell Mr. Bell, Mark P. sent you.... Yes, he's a friend of mine. You want part number 2023 Mark
New toys showed up today: Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Yes I'm aware of that. Never the less it is important to know. So thanks for bringing it up. I upped my fuel pressure. The early 348s (mine is a '90 D block) run 3bar fpr, the later 348s (G & H blocks I assume) run 3.8bar fpr. The little bit of extra fuel did help a tad with my torque, +1 peak tq & aprox +2 to +3tq midrange. The fpr upgrade is not a straight swap. You need to change the fuel lines, the fittings and the fpr are different. Here's the thread from my fpr upgrade. http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/457779-348-fuel-pressure-regulator-upgrade.html
I wanted to touch on this again. Back when I ported my throttle bodies I also examined the MAF versus the connecting tubing. That is the tube that connects to the back of the MAF and runs to the opening of the throttle body. The inner diameter of the MAF is 62mm. The inner diameter of the connecting tube, that connects to the MAF, is approximately 61mm. This picture is looking in from the inlet of the MAF through to the inlet of the connecting tube. You can see the difference in size, with the tube i.d. being smaller than the MAF. That smaller diameter is 1) a restriction, and 2) the lip can cause turbulence. Both are not good for air flow, and both restrict the breathing of the f119. Image Unavailable, Please Login
There are several tuners out there that remove the cooling fins within the MAF to improve air flow. It is documented in a book entitled "How to tune and Modify Bosch Fuel Injection". Also refer to this link: (How to cut the screens out of MAF? [Archive] - Page 2 - Corvette Forum : DigitalCorvettes.com Corvette Forums)
