You are correct as the USA F40 is designed and tuned for muffler and converter. When opening the exhaust, you must also open the engine. The way you do this is to modify and tune the cam timing along with a slight ecu upgrade. You must also make sure everything else is working in good shape like the injectors that are prone to clogging and the throttle plates must be adjusted properly. After that, you can adjust the Wastegate. Really brings it to life.... Best regards, Jim P.S. Dave@Scuderia Rampante did a upgrade on the fusebox for one of our cars. Very noticable diffrence in how the car performs. he did a great job and we are going to do our other cars.
F40 wastegate spring "adjuster" is a fine tuning mechanism, will not change boost dramatically. The wastegate spring rate is 41 lb/in. Spring free length is 3.70inch. Height at coil bind is 1.08in. Installed height stock is 2.68in. Valve stroke is 1.0in. Diameter of wastegate diaphragm is 90mm, approx. area is 9.86in^2. Therefore stock Force to open wastegate is about 42lbf and Force at full open is about 83lbf. More later...
Overspeeding the turbos and resultant failure; we blew a couple before our 'fix' of bigger turbos (Turbonetics helped me with selection). The turbo failure was the axial bearing, breaking the shaft and sending the turbine into the exhaust (lots of smoke too!).
Great info... Most of the time we found that did not really need to adjust wastegate to get more power. we mostly find worn componets like the wastegate control valves that fail, the crank sensors age and don`t perform as well as they should, leaky or clogged injectors, cam sensor that degrade, etc..... lot of power to be found just replaceing worn items. Regards, Jim
there was a specific-a crucial boudary limit-quantity of material for the machinist(thats me) to cut out of the wastegate housing so as NOT to exceed an approximate dyno value of 650/675 HP. The danger in exceeding this amount was a high degree of proability that when a shift was blow-and blown they are.... frequently, in the REAL world-it would help to save the gears in the transaxle-specifically the transmission. At 650-675, the threshold limit, is at the limit of security...it was KNOWN that much higher was just asking for trouble, after all, the Factory knew this... the 750HP+ F40-LM had the "double truck", doggie, straight cut gears... the stereet gears' teeth just sheer off like potato chips at this level...at 800+HP(F40-GTE etc), they had to go all the way to "X-Trac" gearboxes.... To aid in signal modulation- of pulse surges-in the duty cyle which drives the gate, is "hogged out" by 100%(this is a small dis to begin with, so 100% is alot in the real world) That said.... in 1990 all sorts of F-40s were reputed to have had turbo failures-this was a "problem" in 1990 cars-or so was the perception and scuttlebut....especially in LA, but CA as a whole... the truth was something different... a new, after market product had made its way to market, and was showing up all over the place here in CA-the TUBI exhaust-and "test" pipes.... Cars were roasting turbos... pretty regular, with nobody the wiser-including FNA... as soon as test pipes went on, the loss of back pressure wreaked havoc with loss of backpressure BALANCE-which was engineerred into the fuel maops in ECUs-there were engines jammed through warranty, i was told, based on spectacular turbo disintegration....nobody in management had bothered to ask anybody in the field to connect the dots...it went back to italy-then the edict came down that: ANY muffler change was grounds to void warranty.... ARB got involved, said cat back was ok and tough titty to Ferari if motors had a problem...fix the problem... magically, the racing guys started to leak some criticality sizing limits to a chosen group of dealers and well healed owners with monstrer collections.... the temp over boost/over spooling thing was discovered by FNA here in Monmtery, CA I have been told(the mech was in the car with FNA rep playing with cardboard panels!) The machine shop mod had the benefit of stopping the problem on a system that was so sensitive merely removing the muffler caused a problem-the law of unintended comnsequence allowed for full cat removal tuning to now be available at a known level of higher boos-a boost level well within breakage boudaries of the drivelines weakest link. I will tell yoiu that most guys get rubber knees in these cars-at 675HP....I get rubber knees... and I no longer drive these on the street, the brakes are NOT good enough to stop the car now-so when does it all stop? Just buy an LM....and be done with it...
Expanding... Manifold pressure to fully open the wastegate: Force on diaphragm = Pressure in manifold * Area of diaphragm, or P(m) = F(d)/ A(d) 83lbf/ 9.86in^2 = 8.4 lb/in^2 manifold pressure
The stock F40 wastegate modification to allow proper operation and drivability with low restriction exhaust is to decrease the initial wastegate spring force (valve closed) by removing material from the spring seat. Remove 0.53" (about 13.5mm) to increase the wastegate spring installed height to 3.21" (81.5mm). So this mod changed initial force required to crack open the wastegate of 42lbf to 20lbf and force required to fully open the wastegate from 83lbf to only 61lbf. Best, Rob
I've had to do similar mods to 996/997TTs when fitting big turbos, freeflow exhaust. Had to get the bleed off much earlier to prevent the electronics safeguards kicking in. I agree with the other post, who needs a 800+HP Porsche for the street? Beef up the clutch, beef up the trans (still eggshells), driveshafts, etc., etc.. I love the stock F40 and it's quirks, a driver's car!
well...someone has finally said that the emporer is not wearing any clothes! I would like to have done so... years ago, but it would have angered too many others in the modify and repair/maintenance arena-as well as opened the avenue of potential zealous litigants... should not ALL the mods are/be done-or are not done properly, resulting in a blown engine, or just plain poor running.... ...thus resulting in a lawsuit of the: "but you said in F-Chat: blah, blay blah, that if you do: yadda yadda yadd, it will be great! and I'll have the Bob *****in' F-40!" No Thanks.... You have more gumption than i, but i'm glad someone's stones are big enough to say the dimensions out loud! bravo..and grazi...
