A 3.4 DOHC Build then... F40 Turbo (Page 7/57) darkhorizon MAR 02, 01:45 PM quote Originally posted by 3.1 88FieroGT: Very nice work you are doing... Just out of curiosity why didn't you run an divorced waste gate (meaning open to atmosphere)? Emission? noise and better boost control are my reasonings for it. Might be trading in some exhaust flow potential, but meh. 3.1 88FieroGT MAR 02, 02:48 PM I love the sound of my dump. How does it help with boost control asking cause i'm curious. Fierobsessed MAR 02, 08:08 PM I chose to run the dump into the exhaust for three reasons. I don't like to breathe exhaust fumes, a dumping wastegate could be viewed as an exhaust bypass by a keen eyed emissions inspector. And I kinda want this car to be moderately quiet, and not totally obnoxious on power either. Really there was no great reason to do an atmospheric dump, other then a lower back pressure when the wastegate is open. As for the old exhaust, the jury is still out on it, I had planned on re using the muffler and tail pipes, but I'm starting to waiver on the idea of doing that, it is a complete almost all stainless 3.4 dohc exhaust system... Including the crossover... Joseph Upson MAR 03, 07:53 AM quote Originally posted by 3.1 88FieroGT: I love the sound of my dump. How does it help with boost control asking cause i'm curious. Open dump is best for all out performance since redirecting exhaust back into the mainstream disrupts flow as well as potentially affects boost, good and bad depending on what you're trying to accomplish, but ultimately the noise level would be the determinant for me. I've run both and currently run open dump just behind the inboard cv joint and because of the length and size of the dump pipe, it makes the sound heard when blowing over the opening of a jug when it opens. The location of his wastegate would very likely allow fumes to roll back into the car if it were open dump, unless the dump pipe was unusually long and exiting near the back of the car. One thing for sure, if you don't have enough exhaust flow it will not matter much. darkhorizon MAR 03, 01:24 PM quote Originally posted by 3.1 88FieroGT: I love the sound of my dump. How does it help with boost control asking cause i'm curious. Physics of the main exhaust flow leaving the turbo and a proper angle of the dump tube will effectively suck exhaust out of the wastegate. Joseph Upson MAR 03, 01:40 PM quote Originally posted by darkhorizon: Physics of the main exhaust flow leaving the turbo and a proper angle of the dump tube will effectively suck exhaust out of the wastegate. I don't know dark, I don't have access to Maximum boost at the moment for all the specifics but I'd expect the velocity of the dump exhaust to be higher than the main exhaust leaving the turbo and likely to serve as the source of instead of being subject to any scavenging. The transition into the main will have an effect for sure depending on its arrangment. DaytonTD MAR 03, 02:10 PM Gorgeous work your doing, keep it up! 3.1 88FieroGT MAR 03, 07:02 PM quote Originally posted by darkhorizon: Physics of the main exhaust flow leaving the turbo and a proper angle of the dump tube will effectively suck exhaust out of the wastegate. Still really don't see what that has to do with the Waste gate opening and closing in turn controlling boost... Either way i'd rather have as little back pressure as possible and being a younger guy my loud exhaust system doesn't bother me. Fierobsessed MAR 04, 04:34 AM quote Originally posted by 3.1 88FieroGT: Still really don't see what that has to do with the Waste gate opening and closing in turn controlling boost... It doesn't. I'm sure he means that with the lack of back pressure in the exhaust for the dump gives it more capacity to flow out the necessary gasses to keep the turbo's speed under control. This is true when you are running your wastegate on the ragged edge and you need that extra flow of an external dump. But to that, the arguement can be made that if your exhaust adds enough back pressure to your wastegate to cause boost creep, it also adds it to the pressure at the outlet of the turbo, and that decreases boost. But if you're running into those kind of issues, your exhaust system is FAR too restrictive to begin with. That's why I'm contemplating a different muffler at the moment. I did some asking around and word on the street is that although my old Flowmaybe 80 series crossflow sounds great, it does NOT flow, and that I need to look into straight through, bullet style mufflers. My goals aren't too lofty. Over 400, under 500. The turbo can do 600. But honestly, the engine is pretty much stock, so I think doubling the 210 from the factory, and then some is reasonable. I only plan on studding the heads down, possibly the bottom end too. On another topic of interest at the moment. Clutch selection! I've done quite a bit of research lately. But no matter where I turn, the waters get muddy. It seems that the clutch I want might not exist, or is so rediculously expensive that I would never consider using it. The good news is that the F40 transmission has a common spline count and diameter, and a very common disk diameter too. Cars that have a 1" 23 spline shaft, and around a 240mm disc... a bunch of Fords, pickups, explorers, probes and focuses Most Mazda's even including RX cars a buttload of Porsche's if not all of them. Mitsubishi's, especially the lancer evo cars So there is no shortage of potential disc sources, and plenty of high power applications. I really want a low inertia disc. I absolutely LOVED my clutchnet Kevlar sprung disc that was in the car with the Getrag, but it was WAY to heavy. I could tell that the synchros were struggling with every shift, and with the high RPM 3.4 DOHC, it was taking its toll. After 30,000 miles with the 3.4 DOHC, this is what came out, note the minimal dust. unbelieveably, this is what the pressure plate surface looked like! You can see that the original machining is fully intact. The flywheel looked the same, and there was virtually no wear of the clutch material itself. It also held quite well, only once it broke in. very little dust in the bellhousing and on the pressure plate too! So for the most part I was VERY pleased with this clutch disc, and I plan on installing it on my 3800/F23 with a stiffer pressure plate. But that's a story for another thread. I really took an interest in the Porsche disc's They so clearly have minimal inertia. However, I don't like the idea of using an undampened clutch disc. They can beat a transmission, or drive line to death. Every engine crankshaft pulse needs to be absorbed at the clutch, using a dual mass flywheel works, or a dampened disc. I plan on making a custom flywheel, using a SPEC high clamp pressure plate. But what disc??? Anyone have any ideas? sleevePAPA MAR 04, 04:48 AM I have the clutchnet 6 puc disc and found that it performs very well, with minimum chatter. its the sprung hub though. thats about as aggressive as Id want to go to keep it streetable.