Yeah, hopefully! I'm not convinced about the length making a difference to resonance. When one of yours slipped on the Mk2 centre )( pipe I made, I adjusted it and couldn't really tell. What also happened then was that when it slipped, it exposed the gap at the clamp slot on one side, making a leak... maybe that affected it. I think this is more like it. It certainly resonates less with the centre pipe on anyway.... what the hell, I'll post the pic of my pipe. I'm not a site sponsor though, and this pipe is not for sale. Be careful to measure the tail pipe protrusion when cold... as it moves a great deal when hot/mid cycle, so it could be easy to get confused measurements. I'll measure stephens car and post the current cold extension tomorrow. Image Unavailable, Please Login
yeah yeah, Relax, it's quite high on my to do list..... maybe you should call all those you're trying to queue jump to save me the time and hassle....?? You can shout drinks at the HSS xmas party.....!
It's ok, Carl is doing the frisking, that should keep numbers under control. Thanks anyway! By the way, customs don't have the cat pipes yet, it was something else I got a message for. Haven't heard about them yet.
Ok, now you guys are really cranking. Sorry to hear about the clutch - any thoughts on replacement? Going to custom fab the flywheel too? Lightened flywheel - I'm not sure if I'd necessarily do something as whole lot lighter. chatter and a considerably faster throttle response aren't something I think the car necessarily needs. A little, sure, but if you end up with a 6lb flywheel, it'll be noisy as ****. Sorry to go backwards on a few issues, but 1) QS is making test pipes? REALLY? Are they doing to do a middle-ground hyperflow setup too that should technically pass smog? Also - what are you going to do about the computer and the O2 sensors? How will you remap them so that the motronic ecus and thermocoupler ecus dont go *****ing and throw the car into limp mode? 2) On your center pipe, Phil, is appears that both tubes touch. Are they separate air channels per bank or do they cross inside? 3) Differnece in length with heat - everyone keeps telling me this, but I've measured them cold and hot, and they seem to stick out too far in both cases. Cold, my tips stick out about 1.5-2" further than others. I'll take detailed measurements when I get back. Thanks for taking some of yours (pictures are super-helpful). With respect to resonance; yes, having the clamp gap exposed will cause HUGE resonance. A small hole (small enough to maybe fit a toothpick) will still cause massive problems. You'll prolly also get a slow down light. I know first-hand on this one. Also, what's the name of the book Stephen? As you've obviously gathered, I don't know sh|t, so any knowledge is good. As I gather, the cross-pipe design is better than the separate tubes for scavenging. What do you think the effect would be of not having crossed-pipes? I feel like you've already done a whole lot of what I'm going to try. Only you've got way cooler tools! --Dan PS: Stephen like I've told you all along, you've got WAY too much time. Keep it up!
Not going to go radical on the flywheel. Just significantly lighten the std one and beef up the std clutch pressure plate and centre plate. Not really interested in half way cats, in or out is the only way. I've got a contact claiming good things for 550. eg std car gains 60Nm torque and 25bhp, also removes CE light and change rpm limit if desired. Yes, my pipes are cross over inside. Look closely to observe careful mis alignment of in/out pipes. Probably giving away too much here, but it's way better than parallel split or straight line "X" pipe. Parallel pipes are ok, but the scavenge effect makes a big change. Any exhaust leaks AFTER the cats have no effect on "slow down" or anything else. To remove the slow down is simple, just short/bridge the input to the thermocouple control unit. CE is harder and I haven't done it yet, but I've been categorically promised by my supplier that Motronic 5.2 is doable with re-map software etc. Image Unavailable, Please Login
I assumed you only meant to go with straight runs in the center section, rather than an x-pipe. The older 275's have straight runs from headers to exhaust tips ... never meeting or crossing over to the other side. This is what gives the older V-12's their unique sound. Would be interesting to see what a straight run would do for the 550. I also have no interest in removing the cats .... Regarding the stebro ..... it does "join" in the center. The stock 550 center muffler also joins ... it's basically one muffler with two inlets and two outlets. BTW, my Stebro fit perfectly. Tubi does make a very similar product to the stebro .... only real difference is $ 2,200 for the tubi verses $ 580 for the stebro. Both of these do intersect at some point to allow crossflow ...... I'll assume the tubi is polished .... but who sees this hidden by the under tray. I can't comment on the benefits of crossflow, verses a straight run ......... but regarding back pressure ...... this doesn't seem to be an issue for those who build the highest horsepower motors around .... top fuel dragsters ... I also question exhaust tip location having any effect on exhaust sound. I really doubt this ... unless of course, your tips ended inside the rear opening on the bumper.
Regarding backpressure... whether it's written in books or not, an engine with no exhaust backpressure will have less torque than the same engine with reasonable backpressure. It may make good power, but torque is what we all feel and use everyday. Backpressure is our friend, we just need to use it right. as an extreme example of this.... go and drive a 2 stroke Go kart or M/cycle with the exhaust missing and see how flat it is until peak rpm, when it'll take off like a rocket.
The advantage of the extra cost for the Tubi x pipe isn't that anyone will see it, but rather that it is SS and won't rust. The welds on the stebro were so bad it looked like they dripped candle wax on it. The flange didn't fit and I had to have it modified, costing extra $$$ "you get what you pay for" has a ring of truth to it at a certain point.
Sorry Phil, you are confusing exhaust resonance and back pressure. There is a point where experience and theory overlap and this is it. Backpressure is not your friend. As a point of reference I have spent much time researching two stroke expansion chamber design for a 250CC GP bike I own and raced in the ARRC. It has different barrels and chambers designed for different tracks. While we're at it, since when is the centre section YOUR design?? I'm the one who pulled the exhausts apart, found the restrictions etc a year before we even met,then told you what I wanted! Sheesh, some people...
Ferrarifixer, I am not clear on the crossover or X-pipe that you show in the picture. Is it something that you made or is it available commercially available? also could you expound on the differences in sound from stock and did you leave the butterflies in the back boxes untouched?
You say you got me, I say you didn't. I'm hard to convince that theory overrules experience, as I have too much of one and plenty of the other! I'll stick to my experience that has shown me backpressure helps torque and open helps power. Gary.... The system in the photo is my own (developed in conjunction with Stephens requirements!.) I have the jig. It's not brain surgery though, and any number of similar solutions will have comparable results. On stephens car I also made a parallell twin pipe, with just a window to the two pipes, rather than a proper siamese or )(. I'm sure the drivability differences were hard to distinguish until demanding maximum torque, but for me the noise of the siamese scavenge system is SO much sweeter at all times.... you hear all 12 cylinders at once, rather than two sixes. The photo shows the pipe when fitted. After several track days it now looks great, with a lovely blueness and even heat dissipation signs.
Phil I'll post the formulae for header/exhaust design later, along with the book name for Dan. I'm sure you've probably seen them before. BTW you don't want backpressure, you want max velocity, with minimum restriciton for peak torque.
Scientists get things wrong. Formulae don't always work. A formulae that works here may not work there. Which area of human evolution would you like mega examples from...??! Publication of a book does not settle an opinion as fact... hell, I could write a book! I could put 12 pipes straight up out your bonnet if you like.........
Ah Phil It is all just applied mathematics. Rather than relying on one text, or opninion, I find it more useful to understand the theory and draw my own conclusions from its application. Perhaps the fact that I studies applied mathematics at university helps. Some good resources I have used. Motorcycle Tuning Four-stroke by John Robinson Four Stroke Performance Tuning by A.Graham Bell The Racing Motorcycle - A technical guide for constructors by John Bradley 21st Century Performance by Julian Edgar. Interestingly the formulae for header and exhaust design is consistent between authors... I wonder why? On one racing bike alone, I have close to 200 runs on Phil Taintons dyno(you may have heard of him, he runs the factorys Suzuki superbike team in Aust), personally developing a street Ducati 999 that succesfully competed against factory race bikes in the Aust Superbike Championships. I actually qualifed mid field at Eastern Creek, with performance the equal of the NF Imports factory supported Ducati. Not bad for a middle aged old fart.... So you see, my experience is born out of a bit more than books. As to your example of straight pipes, this would not take full advantage of the suction wave of a properly designed header. Also altering the length and diameter of the pipes will effect the torque peak of the motor. Once again, nothing to do with backpressure. Yes, you can use backpressure to alter the characteristics of the motor, but this is not a substitute for a properly engineered system. Now, I know you know these principals, so why are you arguing to the contrary? Phil, you couldn't possibly have been wrong could you?
Thank you... "you can use backpressure to alter the characteristics of the motor"... so without backpressure, then what.... there's only so much mapping and induction efficiency to play with. Would you rather have larger exhaust porting and valve area than inlet to help you in your quest for no back pressure? During my mere 4 full time college years I had teachers bursting with theory that struggled to gap spark plugs. If we all run our vehicles using torque converters with CVT gearboxes at one constant engine rpm, then exhaust backpressure would be unnecessary. (hmmm.. top fueler maybe?) However, we need to run quietly and cleanly at 1000rpm idle and powerfully at 7000rpm ++.... so the engine needs a wide band of flexibility. Here is where theory is a useful tool, but experience makes the development efficient.... The (only) Mk3 system is great is it not?? (In fact Mk1 was bloody good too remember). So... when do you want the 12 rocket launchers out the bonnet then......? And should I flip the heads round to reverse the inlet/exhaust while I'm at it?????
Just curious. Its my understanding that the later 575s do not have a center muffler. With this in mind how did the factory design this section of the exhaust and is design applicapable to the 550?
Just got my car back from ferrarifixer tonight. New race clutch and Quicksilver cat replacement pipes. Phil can chip in, but he said there were some issues with positioning of the O2 sensors that required "modification" to get them to fit, so if anyone else is interested it may be worth getting Phil to use mine to make a jig and get others made up that are a better fit. Funnily enough, not check engine light (yet). However we are doing an ECU upgrade which includes the CEL bypass for the rear O2 sensors. The performance improvement is immediately noticeable from 3K onwards. In third and fourth gears, the car revs so quickly from 6K onwards it is impossible to not hit the rev limiter. It is also pulling hard right into the limiter, so I really need an extra 500-750 rpm now. I was hoping for an increase of around 30hp but it feels WAY more than that. I will get the car on the dyno, hopefully Monday for some quantifiable results. I am also having the ECU upgraded with increased rev limit and optimised fueling (the car runs far too rich for max power as standard). I'll have another dyno done after that to see exactly what the improvement is. Meanwhile I am going to go for a late night run with my Race Technology DL1 data logger tonight and compare roll on times and hp figures. Final plans are for custom ceramic coated headers and gas flowed intake manifolds and machined throttled bodies. I am fairly confident now of well over 600hp without opening the motor.
Dont forget your flywheel is now 6lbs lighter than it was, and the centre plate is 2lbs too... so 8lb total rotational weight saved... it's easy to say the exhaust did this or that... but I reckon the flywheel makes a big difference too. Removing the cats also saved 12kg, and the centre section is also 12kg lighter than the std section. FYI
The flywheel/clutch help marginally in the lower gears, but doesn't help acceleration from 100-150mph, which is what I am testing. I know this from testing my race bike on a Dynojet dyno, with carbon clutch, lightweight flywheel and carbon fibre rims.
I'll warn you now i'll be doing a freeway run after midnight. You'll probably be able to hear it from your house.
