REW Sequential Dyno - very uncommon results

[dudemaaan]

Does the cosmo pump have good wiring? You're sure it's the filter clogged and not a sticking check valve or something right? You have a fuel filter sock on the pump right? Check to make sure it has the plastic things to keep it from collapsing on itself. I remember one guy's thread he was having trouble with fuel pressure dropping off, and it turned out the aftermarket sock he installed didn't have anything to prevent the sock from collapsing on itself, once he replaced it, his fuel pressure was back to normal.

Curious, where are you measuring back pressure for the twins? It's hitting 33 psi of back pressure at that point on the graph and it hasn't even peaked yet. That's pretty terrible.

The boost dropping off doesn't look like it's falling off a lot, maybe you need to adjust the solenoid gain, not sure what the motec has for adjusting boost, but most boost controllers need some kind of tweaking to keep it from creeping or falling. You could pressurize the intake system and check for leaks. I'm more inclined to think your engine is just breathing too well for the turbos, they can't supply the air that the engine wants. Based on the amount of power it's making at low boost pressures, it's requiring a lot of air. Twins usually start running out of breath around 14 psi or so, well you're using the same amount of air at 9 lbs of boost. You might just need larger compressors, just throwing it out there. It might be something else going on.

[TitaniumTT]

Originally Posted by BigIslandSevens

NIce numbers man! That thing should be a handfull when you stab it. Here is a link to a lab that tests fuels among other things.

http://www.intertek-cb.com/services/services.shtml

And a lab search engine I beleive

http://www.contractlaboratory.com/La...as_testing.cfm

Yeah, she definately gets up and scoots. Thanks for the links, gonna give them a call first thing Monday.

Originally Posted by dudemaaan

Does the cosmo pump have good wiring?

Yup, battery relocated to the bin, 25A breaker right there, 10ga wiring to the relay mounted on the shock tower and 14 ga to the pump itself.

Originally Posted by dudemaaan

You're sure it's the filter clogged and not a sticking check valve or something right?

Positive, after that last run we wheeled her forward, threw her on the lift and pulled the filter right there. We could barely blow threw it. Granted Dave and I are smokers but still. New filter went in and the L went from .8-.74. More flow/pressure = more fuel = rich etc etc.

Originally Posted by dudemaaan

You have a fuel filter sock on the pump right? Check to make sure it has the plastic things to keep it from collapsing on itself. I remember one guy's thread he was having trouble with fuel pressure dropping off, and it turned out the aftermarket sock he installed didn't have anything to prevent the sock from collapsing on itself, once he replaced it, his fuel pressure was back to normal.

Running the stock FC sock. Big square thing. Damn clean when it went in but I am going to check that, probably replace it as well. Whatever is clogging this up seems to have gotten a little finer as the 100 micron or so sock isn't getting clogged up but the 10 micron filter is. The ONLY thing left that hasn't been replaced or thouroughly cleaned are the lines themselves. I replaced them with -6 stainless lines. The last time I had the tank down I emptied a car of carb clean into the lines and then blasted 135psi of air through them. It took a dozen times or so to empty the can.

Originally Posted by dudemaaan

Curious, where are you measuring back pressure for the twins? It's hitting 33 psi of back pressure at that point on the graph and it hasn't even peaked yet. That's pretty terrible.

I'm measuring backpressure in the mani itself. Dead center between the two exhaust ports. We're seeing a max of 275 kpa which is 25psi. Where are you seeing 33psi?

Originally Posted by dudemaaan

The boost dropping off doesn't look like it's falling off a lot, maybe you need to adjust the solenoid gain, not sure what the motec has for adjusting boost, but most boost controllers need some kind of tweaking to keep it from creeping or falling.

The Motec has two ways of controlling boost. A PID function where you enter duty cylces into a Normal Position Table which the ECU looks at first then compares the Actual Boost to the Aim Boost and corrects the duty cylce accordingly. The PID needs the normal position table to be pretty accurate otherwise it hunts all over the place. I have a few logs where the Normal Position was close but the duty cycle would fluctuate between ~30 and 70% across the RPM range to hold boost.

While on the Dyno we were using just an open loop, we input the duty cycles that we want it to see and it does it. So we could easily reduce the duty cycle. We were at 33% before the fuel psi problem struck so there's a bunch more than we can take out. I MAY have to do a different actuator. I hear there is one that is about the same dimensions and has an adjustable spring, from the factory.

Originally Posted by dudemaaan

You could pressurize the intake system and check for leaks. I'm more inclined to think your engine is just breathing too well for the turbos, they can't supply the air that the engine wants. Based on the amount of power it's making at low boost pressures, it's requiring a lot of air. Twins usually start running out of breath around 14 psi or so, well you're using the same amount of air at 9 lbs of boost. You might just need larger compressors, just throwing it out there. It might be something else going on.

Thanks for all the help man, I really appreciate the insights. Having an engine that flows too well isn't exactely a bad problem to have. Of course then the question becomes do I just leave these turbo's alone where they are or do I do something crazy like a twin GT28 A-la Howard Coleman setup. They won't have the response of the sequentials unless I go all Mad Scientist with wastegates and tubing to make my own sequential system, but they will deliver the air for 400 RWHP..... decisions decisions.

I'm going to check all the valves and make sure they are not only fuctioning properly but are setup correctly in the software. Last night driving home I was checking Fuel PSI by making a few long runs up to 7500 while @ 0", I could hear a whooshing sound coming from the right side of the engine, at least I think it was, I'm thinking the Charge Relief Valve is pinned open, setup wrong, or the vac lines are wrong and that thing is just pinned open venting boost pressure. That would be a major leak to say the least. But like you pointed out, there is a TON of backpressure and not much boost. I know I've seen 15 psi higher in the band with less duty. So after I check that thing out I'm going to be pressurizing the entire system to see if there is anything else leaking.