PWM boost control and not holding boost?

justin · Post by **justin** » Wed Mar 18, 2009 9:21 pm

I'm having problems getting boost to hold using s300 boost control. When the car was tuned last Nov. it was holding boost just fine @ 20psi or whatever we set it to (10psi in 1st, 15psi in 2nd, 20psi rest of gears). Or atleast it did on the dyno pulls, didn't do many 3rd/4th gear pulls on the street til later. After a few weeks or so, I started hitting boost cut in 4th gear, then 3rd gear, so I adjusted the solenoid (MAC valve) duty cycle down some so I wouldn't hit boost cut. It worked ok for a little while but eventually I was hitting boost cut again and would have to re-adjust the solenoid duty cycle down.

I tried starting from the bottom up today and set the solenoid duty cycle really low, so all it would do is run off the wastegate (10.5psi spring). Which it did, and held boost right at 10psi. Then I gradually started increasing the solenoid duty cycle 'til I started getting more boost, which I did. I cannot seem to keep the boost at a set position however, it keeps on creeping. I can either spool the turbo real slow like WG is half open, or up the solenoid duty cycle a % or 2 and it will shoot straight to boost cut and not stop, like WG is not opening at all. I can't seem get a normal fast spool and have it hold a boost level without creeping up just shooting straight to boost cut.

Nothing has changed since we tuned it, other then that I have been daily driving it since then. I've checked my hoses and hardware, everything looks ok and I don't see any signs of exhaust leaks. Anything else I can check or do to test? I was thinking about adjusting the solenoid duty cycle % in half percents to make it finer, or maybe just use a set duty cycle for testing and not use the boost by gear. I am pretty sure my solenoid is working properly as it does regulate boost. I don't have an EBC to use for testing or anything so really want to find out why this is happening.

Setup is:
sohc vtec, built bottom end, stock head
ramhorn manifold, BW t3/t04e 50 trim, 3" full exhaust, Tial 38mm WG, TialQ bov
s300+PWM, 1000cc RC's, e85

Calibrations are attached from my original dyno tune, to what I am using now.

Hmm as I am about to post this I remember there being something with the Tial wastegates and e85. Anyone recall what this is? I think here is a certain type of seal you need, can't remember, I'll have to research that again.

Thx for any help,
Justin

Post by **Spunkster** » Thu Mar 19, 2009 9:36 am

All testing shoud be done with a fixed duty cycle. I don't have any information about seals and using E85.

b20luda · Post by **b20luda** » Sat Mar 21, 2009 9:55 am

read around hondatech and other forums, very few people get it to work properly, i tried mutiple valves different boost sources settings etc, never worked right for me, went to AVCR and worked fine, hondata installed the boost control stuff too

Post by **Hondata** » Sat Mar 21, 2009 8:26 pm

It is possible to get a very flat boost curve with the PWM control, but you need to understand what factors influence the wastegate.

Look at the duty to presssure table. 2% duty gives 5 lbs boost change - this is the problem.

How is the wastegate plumbed in? Describe exactly how the vacuum lines are run. What is the wastegate spring pressure?

justin · Post by **justin** » Sun Mar 22, 2009 5:46 pm

Ok, I tried some more testing with fixed duty cycle today. First I'll answer the questions:

wastegate spring: 10.5psi like original post says
vacuum source is on turbo compressor --> goes to a T fitting --> 1 off T goes to WG bottom port --> other off T goes to solenoid #1 port
WG top port --> goes to solenoid #2 port

Servion tuned this car last November, and we did the wastegate plumbing there, I drove to the dyno just on WG spring boost, no PWM turned on.

Today I could not get it to hold boost either. I got it to where it's kinda manageable, but it's not right. I either hit revlimiter or boost cut, whichever comes first. So for example, in 2nd gear I'll hit revlimiter before I hit boost cut, then 3rd gear makes it to revlimiter but never hits max boost and spools slow. I should see max boost at like 5200/5300rpm but it just gradually creeps up, like wastegate is partially open opening. Then 4th gear it just shoots straight to boost cut w/out stopping, I don't get it.

I've attached all my datalogs, labeled with what duty cycle % I used for each log. For some reason when I set the duty cycle % to 33.5% the datalog only showed 33%? Do half percents work? Also, put in the latest calibration I'm using...you can see how different the duty cycle %'s I have to use now compared to when we tuned it.

Thx for the help.

Justin

justin · Post by **justin** » Sun Mar 22, 2009 5:48 pm

b20luda wrote:read around hondatech and other forums, very few people get it to work properly, i tried mutiple valves different boost sources settings etc, never worked right for me, went to AVCR and worked fine, hondata installed the boost control stuff too

Yea I had already done that and read a bunch of similar stuff. But we had pwm going ok on the dyno it seemed, and I trust servion knows what he is doing. I really don't want to blow a small wad on an EBC when I put in the extra money to get PWM boost control working. I mean I will if I have to, but this should work right, there is a problem somewhere.

Justin

Post by **Hondata** » Mon Mar 23, 2009 8:41 am

You will need to find the best location for the pressure source - the compressor outlet usually gives a lot of boost creep, especially if the intercooler is restrictive. Try using the intake manifold for the pressure source.

justin · Post by **justin** » Mon Mar 23, 2009 12:11 pm

Hondata wrote:You will need to find the best location for the pressure source - the compressor outlet usually gives a lot of boost creep, especially if the intercooler is restrictive. Try using the intake manifold for the pressure source.

Ok. I'll switch the WG vacuum source with my BoV then since bov has it's own source on the manifold.

Justin

justin · Post by **justin** » Sun Mar 29, 2009 4:47 pm

So I switched my vacuum's around. I setup the wastegate/solenoid vacuum just like the picture shows in the Smanager help. So vac' source is on intake manifold and T's to the WG bottom port and solenoid. It seems to be behaving better now but I still cannot get it just right.

I set my solenoid duty to 35% and it hit boost cut like before. Lowered it down to 33% and it held around 16-17psi I think it was. Upped it to 34% and hit boost cut again, which was set at 23psi. I tried 33.5% duty cycle and again it seemed to stay around 17-18psi or so, but build those last psi of boost late in the rev range. Hard to get a good grasp though from tuning this on the street, especially when I set it to 33.5% and it holds around 18psi but then bump it .5% to 34% and it goes to boost cut, 5psi more boost. But at least it seems to be better then before. I think with some fine tuning it will be good again, it is a real damn pain in the ass though, wish I had unlimited dyno time to do this on :/

Attached more datalogs from today if anyone cares...

Justin

Post by **Spunkster** » Mon Mar 30, 2009 10:13 am

If you got the solenoid from somewhere other than Hondata, it may be the source of the problem as it may be the wrong solenoid.

justin · Post by **justin** » Tue Mar 31, 2009 8:31 am

Spunkster wrote:If you got the solenoid from somewhere other than Hondata, it may be the source of the problem as it may be the wrong solenoid.

I suppose that could be it as I didn't get it from hondata, but I was assured it was the same solenoid. Is the software only compatible with hondata branded solenoids? What would make it the "wrong" solenoid?

Justin

Post by **Spunkster** » Tue Mar 31, 2009 9:34 am

Some solenoids may not have the ideal characteristics for this type of use. We know that the solenoids we sell work.

justin · Post by **justin** » Tue Mar 31, 2009 9:35 pm

Spunkster wrote:Some solenoids may not have the ideal characteristics for this type of use. We know that the solenoids we sell work.

Alright, well I ordered a "Hondata" solenoid from local dealer...see if it works after it gets here.

Justin

V-Spec race development · Tue Mar 31, 2009 10:21 pm

And let us know what happen and see if the problem goes away or not.

crucian · Post by **crucian** » Mon Apr 06, 2009 11:14 am

While you're at it, check for a boost leak in your vacuum lines to and from the wastegate. Check them very closely. Also check the diaphragm inside the wastegate to make sure it's not torn. I bought a new wastegate once for the same problem you're having not realizing that I could have saved a lot of money. I must say though, in my experience with the Hondata boost control I have seen boost creep while tuning other cars with it.