Are you referring to it leaking under idle, or under boost?
Most bypass valves are open at idle, the crappy plastic ones leak under boost if you are pushing more than around 6 psi. Even when leaking they let you run good boost pressure, but they are constantly feeding hotter than ambient air back to the intake reducing efficiency of the system as a whole.
Or in my case, VTA, just throwing away boost. BEGI claims these MITSUBISHI ones (steel canisters) don't leak like the Bosch ones, which is why I went with one. How much boost do you recon they will hold?
I used my compressor regulated down to 10 psi to pop the wastegate, and it was not exactly working properly, but it was coming open. But my regulator is not set up for such low pressures, so I was not 100% convinced the small problem I found caused the high boost pressures. I did another test run and was still hitting the boost limit. I figured with the 10 psi worth of springs in there I was getting a bit of overshoot and hitting my boost cut that was set to 180 on load (around 11.6 psi) boost gauge and megasquirt logs were showing it getting close to 12 psi.
So just for piece of mind I swapped out the springs in there for a 8.7 psi spring. Also, set the overboost protection a little higher at 190 (around 13 psi).
With the 8.7 psi spring in the Tial you can see where the wastegate is full open by 9 psi, but boost creeps up from there to about 11.5 and then drops down a bit at high RPM, but never lower than 10 psi.
So, it looks like with the BEGi S6 and the spud you can't really run less than 11.5 psi! Since that was right around my target, I can live with it... but I would rather have the option of running low boost or high boost rather than what I have now with medium boost and up.
Also, this effects spool up pretty bad, if I could run an 11.6 psi spring combo in the wastegate, it would not open until it reached that pressure. As is, the wastegate starts to open early, and is full open by 8.7 psi, and pressure rise slows down dramatically as it creeps up to 11.5 psi. When I had the 10.3 psi spring combo in there I was hitting 11.5 psi by 3800 RPM.... but that may have been with the wastegate sticking shut... still, 11.5 psi by 3800 RPM doesn't sound bad compared to 11.0 psi by 4500.
PS: Thinking of trying the 10.3 psi spring combo again... but I am not sure if it will make the creep worse having a higher initial boost level before the wastegate opens up.
Well, at first I thought I was having stuttering due to over-fueling under boost (was running in the 9.0:1 range at first) but as I have leaned it out over the last couple days, the stuttering hasn't gone away. I concluded that I was having spark blow out with the Fab9 COP system. I know they have had issues with their COP and AIDS on supercharged cars, but I didn't realize it effected megasquirt cars as well. I confirmed the issue by swapping back to the stock coils, and the stuttering is 100% gone.
I will be giving Fab9 a call in the AM to see about arranging for replacement of my igniter with their new style igniter.
Now I just need to resolve my boost issues. I am thinking of going back to the light spring in the wastegate and using a MBC to raise it up to my desired boost pressure... swapping back to the 10.3 psi spring setup resulted in me hitting my 12.9 psi boost limit. I don't want to raise the boost limit to see if this is just a spike (and how high it would spike) on stock rods... Now I just need to see if I have an old MBC laying around from my last turbo car. Hell, I know I have one... just have no idea where it is!
Yeah, didn't seem that bad naturally aspirated, but 1st gear is 100% useless for acceleration now, even starting in 2nd I get some good wheel spin.
Here is my turbo spool data for my BEGi S6 kit GT2860 turbo with Tial 38mm external wastegate with 8.7 psi spring. Full 3" catless exhaust is causing boost creep up to 11.5 to 12.0 psi even with the 8.7 psi spring in the wastegate.
Started runs from 1500 RPM up to a hair over 7000 in 4th gear on a 6 speed with 4.3 rear gear.
2000 1.5 psi
2500 2.7 psi
3000 4.5 psi
3500 7.5 psi Wastegate is cracking open here with the 8.7 psi spring.
4000 10.0 psi
4500 10.8 psi
5000 11.2 psi
5500 11.7 psi
6000 11.3 psi
6500 10.6 psi
7000 11.2 psi
I am wondering if with a manual boost controller I can improve spool up without making the boost creep worse.
Talked to Fab9, they will be sending me the new style igniter for the COP, and talked to BEGi, they will be sending a new heat shield, some fittings, and a dummy MAF pipe to extend the intake pipe so I can use the cold air box.
sounds soooo much better.
love how it sounds now.
also LOVE that you take so many vids. keep up the great work.
when I was running my 3076 the difference between onset with mbc vs just wg can was drastic. it would come on super lazy and smooth, vs with mbc it would "hit" really fast.
definitely try the mbc, or ebc if you have one
I agree, it sounds a hell of a lot better with the turbo in place than it did without. Sort of wish I had the cell phone mount higher on the windshield, but oh well
I have a boost control solenoid on it's way, but I have never used one with a stand alone ECU before... I know all about using a MBC... just need to see if I have one sitting around my shop that I forgot about. I don't really want to purchase a new one when I am going to be using the boost solenoid if I can get it to work well with the MS3. In reality, for "steady" boost control I would prefer a reliable MBC, the boost solenoid is more for experimenting with rising boost as RPM's rise past the torque peak... so if I can't find the MBC in my shop I will end up ordering one.
I went ahead and did a virtual dyno run with some of my data logs... but I did have the windows open when I made the logs, not sure how much that affects them...
I will do another virtual dyno, after installing a MBC to correct my slow as molasses spool up. After I have everything tuned to my satisfaction I will go to my local dynojet to see how it compares to the virtual dyno.
PS: Any virtual dyno experts here? I was able to look at my boost and A/F ratio, but not able to add them to the HP and Torque graph. How do you do that?
Yeah, just make sure to put the name in as it appears on the log exactly, as it will look for that specific column and wont find it if its even one letter off.
Run looks solid man. 10ish psi right? Looks like you're at the limit of your stock internals already and you're just getting started lol
Around 10ish at the top end, 11.5ish in the mid range. My spool up data is taken from this run, so you can see there.
Yeah, I am looking for 225ish wheel torque as a max, and it looks like I am really close to that. Just need to put in the MBC (if I can find it) to fix the spool up and give me a crap load more low end power.
that boost dip is really weird. everything else looks good, esp with only 1 smoothing
I figured out the boost dip when I was supercharged. On a supercharged car, the positive displacement blower supplies the same amount of air per revolution no matter how much resistance to flow the head provides. The more efficiently the head can flow the air, the lower the pressure drops, then at RPM's where the head becomes more restrictive the pressure rises.
When the wastegate if full open, and the turbo is supplying all the air it can for the amount of exhaust flow it has, the boost varies inversely to the efficiency of the engine. If my wastegate was not full open, the wastegate would vary it's position and maintain a set pressure.
In other words, where the engine is able to take in more CFM, the pressure drops, and then as RPM's rise to where the head doesn't flow as efficiently pressure rises again.
You ever order something, and pay extra shipping cost so it will show up before the weekend... then you notice there has been no status update on the order... Called these ******* up, and they are waiting for it to come in from the factory!
If you offer rapid shipping on parts that you do not keep in stock you drop ship the part directly from the manufacturer to the customer. You don't wait for slow crate once a week delivery to your shop, put it on the shelf, wait a couple days, take it off the shelf and box it up, then ship it out the next day as a 2nd day UPS delivery!!!
So, I don't have a MBC this weekend. Anyone know of a speed shop within 2 hours driving distance of Terre Haute, IN that carries high quality MBC's?