rob82

Have you looked at total seal rings? I haven't used them myself but by design they look good. I would like to know if they are used in heavily boosted applications or just your run of the mill chevy's - which seems to be their market...

D-metro is the most manicured ecu of the PFC line up... Where does the missfire occur? What plug gap? How old are the O2 sensors?

As has been said, you should only run one MAC valve(running two relies on the valves flowing and responding electrically the same) - unless of course your ECM is capable of twin boost control (sm4) and you can monitor exh back pressure side to side and balance the turbos that way... As for your questions 1. The minimum requested on time of the valve should not be less than the valve dead time, if fact I would stay a whole factor of 10 away from that. It's really irrelevant but start with around 20hz. What is of more importance when running a closed loop boost control is the feedback frequency. Depending upon you ecu's capability 30hz is a nice feedback rate. 2. What you really need to sort out is what the minimum boost your willing to run vs the maximum boost. For a single sided actuator I would not recommend running over twice the gate pressure unless you have a very competent boost controller. So if you want to run 30psi on high boost then the minimum act pressure I would run is 15psi to have the best of both worlds... 3. Everyone is going to have a different number here as it will depend on the car. 4. Yes rubber mount where possible they can vibrate a bit.

Sorry to be so vague but generally if you can see puffs of black smoke you could be experiencing fairly heavy knock - so if you've got a good set of ears you may pick it up. I believe what you are seeing is raw hydrocarbons(un/semi burnt fuel) exiting the chamber - which sounds weird as you've just thermally and physically shocked the chamber which you would think would give you a really good burn however most detonation occurs at the outer edges of the chamber where you may have a localized explosion rather than a progressive flame propagation from the spark plug... This may also be the reason that EGT's drop during det...

Not always - you often will see black smoke during detonation...

Not sure I really understand what the advantage is over a 3port - you may have to draw me a schematic.. If you connect port 3 of the Mac valve to the bottom side of the actuator and port 1 to the top of the actuator, when the solenoid is un energized port 1 is deadheaded, when energized port 3 is deadheaded, there's no path for the system to bleed off other than back to manifold through port 2. I've always toyed with the idea of having a small pressure vessel that picks up on boost pressure with a check valve to stop it bleeding back to the manifold and use that as my "pilot" supply to the Mac valve, this way you will have whatever boost pressure you run onto of the waste gate even when spooling....

Have you looked at exh back pressure pre turbine? That sounds like such a weird issue to get at low rpm. With a relatively small exh vs largish intake housing your more likely to see a linear increase in exh bp vs rpm. I've never come across the issue your experiencing in any turbo car. Slight over boosts are more likely due to poor electronic control, like PI integral windup... At the end of the day the difference between an internal waste gate vs external wastgeate when you are applying pressure either side of the valve is minimal if any... Whaaaa 5 port.... Does that mean you are using two spools? One open one close? Can't really see that making much difference mechanically, sure makes me think about how the control system will work tho...

That sounds like a weird issue, have you though about a dual port actuator like this: http://www.summitracing.com/parts/tnt-30326

Any reason you didn't put more boost in the mid range to pickup the torque? Looks like a pretty damn good combo just needs a bit more midrange boost... I would try that before changing the housing...I like internal waste gates as the usually extract air from the turbine at a power friendly angle. No reason they can't be controlled as well as an external gate with the actuator and tuning..

That's fairly true from what I've seen. Would you also believe that e85 is likely to put less strain on the ignition system than 98oct.

That's a big call - what make it so fancy?

Did you have a look at the new walbro 460lph. The specs I've seen says it will flow 5.6l/min @5bar and 13.5v compared to that of the 044 that flows 4.16l/hr @5bar and 13.5v it looks as though it would be great for e85. Can't see why this pump wouldn't be good enough for 500rwkw on pump or 350rwkw on e85.

I meant to say "1.8degrees retarded on the other cylinders". If the engine is not knock limited than generally you can get around the dodgy coils by advancing the timing past MBT to account for the slower coil discharge rate/coil voltage rise time.

Well it depends, if you have 1 good coil with 5 bad you could have real problems. Also where your peak power occurs will affect power loss. The higher the rev range the more retarded the ignition event becomes which means the greater the power loss becomes. Using the same figures as before at 7500rpm the ignition retard will be about 2.25deg. Dropping 2degrees on a knock limited rb25 could reduce power by 10-20rwkw quiet easily. You can test the coils response by scoping the coil high voltage side, kind of need to know what your looking at though.

Yes it is possible for a weak coil not to misfire but produce less power. Usually the discharge time increases on faulty coils. Normal inductive coil discharge time can be anywhere from 10-50us, I've personally seen twice the dicharge time in comparing a good coil vs bad, can't remember the discharge time but it was a ba coil. If you look at an engine at 6000rpm with a coil discharge time of 50us and a bad coil at 100us that means if you are knock limited on the good coil cylinder than you will be 0.05/10x 360 = 1.8degrees retarded on that cylinder.