On the X (and maybe other Evos as well, but I've never had one before) the wastegate boost reference is on the discharge tubing bolted to the compressor scroll. Has anyone, other than me, tried referencing the wastegate, using the factory system, from the intake manifold?

I tried it today and it *feels* a little quicker, but it's pretty hard to tell, and I haven't datalogged it yet, so I have no idea if it's *actually* making a difference. Basically there should be less pressure available at the intake manifold to actuate the wastegate due to the pressure drop across the intercooler and piping system, causing boost to potentially come in earlier, and possibly even make an extra psi or so.

No, it's not as effective as a boost controller, but it's only about $8 in parts to re-reference the wastegate. I'm curious if anyone has any emperical data from a dyno.

 

got any pics on how you did it? What are the parts required?

 

I just put a T into the bypass valve line that originates from the intake manifold, removed the vacuum line for the wastegate reference from the turbo discharge outlet tube, and then ran some vacuum line from the "T" to the factory tubing leading to the wastegate. Then just cap the port on the discharge tube so there are no leaks, and it's basically done. I used one T, one line size adapter, like 6 inches of vacuum tube, a rubber vacuum port cap, and like seven zip ties.

I can take some pics tomorrow.

edit - Also, make sure you don't accidentally bypass what I assume is a bleed orifice in the factory wastegate line. If you do, boost will probably drop.

 

make sure that there is still a bleed pill somewhere in the line running to the wastegate or you'll only have wastegate srping pressure to hold boost, which is only like 10 psi. Oh, and what did you do with the boost control solenoids? I'm guessing that you capped the boost lines that run to the turbo/wastegate?

 

Yeah, I think we typed the same thing at the same time.

 

The only thing that I worry about is that there are temperature compensation tables in the ecu tht control how the solenoids operate in different temperatures, like cold weather for instance, to prevent the spiking associated with the reduced temps/denser air. If you run an MBC or do whatyou have done, then you are possibly missing out on a good safety feature. Plus, with ecu tuning you can actually manipulate the wastegate duty cycle mapping to alter how the solenoids work, creating a flatter taper than is possible with a mechanical setup. Just my .02

 

Do you know for an absolute fact that there are temp compensation tables in the ECU to control the solenoids? I pretty much doubt that there are. If you said compensation tables for atmospheric pressure and temp in relation to ignition timing and fuel control, then I would agree. What you said is speculation at best, and will only be understood once the Ecutek dealers all review thier software with a great depth of detail.

Also, modifying a PWM signal to a solenoid bleed control has no effect on keeping boost higher at high RPMs. I read the entire discussion over on the boost control tuning thread. Once the turbo is unable to maintain airflow at high RPM, the boost control solenoids can just open completely allowing the maximum pressure to bleed off from the wastegate, and the boost will still not increase because the turbo just can't push any more air through the system. Once that happens the turbo just keeps spinning faster to try to increase pressure, air velocity in the impeller goes supersonic, it chokes, and then the turbo is pretty much done.

Boost pressure is a measure of the ratio of mass flow to volume flow. Basically divide mass flow of the air (lb/min, kg/sec, etc) by the volumetric flow (CFM, CC/sec, meter^3/sec, etc) and that give you density. Density when corrected for temperature ang humidity directly correlates to pressure. As RPM increases, volume flow always increases. Mass flow only increases until the turbo is providing it's maximum, and once the maximum is reached it is effectively a constant. In this system, density is a calculation of a constant divided by a number which is always increasing, and therefore after maximum mass flow turbo output is acheived, density is always decreasing so long as RPM keeps increasing. If density is decreasing, so is pressure. The fanciest PWM contoller in the world won't make a turbo flow more.

 

Here are some pics. Sorry for the crappy shots, I forgot to take them before it got dark.

 

As an update, I drove the car around most of the day today, and it feels like boost is coming in faster. However, it may just be that I haven't driven it in a week, and my Nissan Frontier is sooo slooooow, that pretty much anything feels fast in comparison.

 

Well, I never said that increasing wastegate duty cycle mapping will allow the turbo to flow more than it could otherwise and create some magic enhanced efficiency. You have to keep in mind that when the boost starts bleeding off it doesn't always indicate that the turbo can't flow anymore, it could be something as simple as the wastegate spring being too soft. And wastegate duty cycle mapping can most certainly increase the level of boost that the turbo holds as rpms rise. Once the efficiency rating of the turbo is maxed out it will taper and have to drop no matter what, but the rate of taper isn't always an efficiency issue and can certainly be altered and better controlled through ecu tuning than a mechanical setup can offer.

As far as the speculation about the temperature compensation tables controlling the solenoids is concerned, how do you think that manufacturers prevent uncontrollable spiking of the boost in cold weather? Using temperature compensation tables for the ignition timing and fuel trims have no effect on boost. They do have to be balanced with the level of boost, as in pulling timing when boost is increased and enriching the fuel mixture to prevent detonation, etc., but that doesn't have any effect on how much boost the turbo actually produces. So, I would say that it is more lilely than not that the ecu does have wastegate duty cycle compensation tables that are temp based. Either way, like you said the ecutek software will reveal quite a bit about the ecu and we will know more then. In the meantime if you don't agree with what I've said then fine, I was only trying to help and offered a suggestion based on what I would have done. Do what you want.

 

As an update to my initial question, here is what I've found. The numbers are somewhat vague because they came verbally from my wife, as she was sitting in the pass seat with a boost gauge in one hand, and a wideband in the other hand, reading them off at random, while I went through first to fourth gears. Not very scientific, I understand.

I have been driving the car with the re-referenced wategate for about a week now. It's got about 800 miles on it at this point.

With the wastegate referenced to the bypass valve line coming off the intake manifold, the boost gauge shows peak boost of about 23-24 psi at around 3500 RPM. Boost drops from 24-ish psi to around 15-16 psi at 7000 RPM. The power transition during gear shifts is a little jerky. Basically when I shift the bypass will open, I let out the clutch and push down the gas pedal, and the car kind of noses over before it takes off again. Basically I think this system is letting the bypass valve stay open longer (or something) keeping boost from coming on immediately post shift. This doesn't seem to happen at all with boost referenced to the turbo discharge.

With the wastegate referenced to the turbo discharge outlet, the boost gauge shows about 20-21 psi at around 3500 RPM. The boost drops to about 14-15 psi at 7000 RPM.

The car "feels" faster with the factory wastegate referencing setup, mostly because of the boost delay post shift.

Wideband data for both setups are nearly identical. AF drops to about 10:1 somewhere just before peak boost, and fluctuates between the high 9.x:1 and 10.x:1 ratios through 7000 RPM. I can't correlate the AFR datalogs to engine RPM yet since I don't have a ciircuit to log coil on plug data to get engine speed on my LM1. This is the circuit that I'm working on as soon as the pressure port adapter allowing measurement of exhaust backpressure is done.

 

^Noize said that with ecu tuning this "bog" between shifts went away completely. I had suspected the same thing that you did at first, but I think the problem just lies in the over rich fueling issue. Hooray for ecutek!

 

I had my car reflashed this morning. It feels a bit quicker but I don't know for sure yet. The bog also seems to be gone today, but, it also seemed to be gone last night while I was driving it with the factory boost reference. I need to drive it more to understand if it's still there.

What I definately DO know from the 40 miles I drove it from the dealer to the office, is that post reflash it no longer runs 14.x:1 AFRs with cruise control on the highway. It's now running high 15.x:1 to mid 16.x:1's with the cruise control on (70-75 mph). Also under power, it seems to have leaned out a little, but I haven't really logged any significant WOT runs yet on the wideband. Whoever said thier car was getting better gas mileage post reflash was probably right.

It feels cleaner at high RPM, but time and the wideband will tell for sure.

I'm going to try re-re-referencing the wastegate to a different port on the manifold, towards the back of the plenum, opposite the TB. I suspect it may help with the bypass valve issue. I haven't read Noize's post where he talks about it.