Loose boost on the top end
 

Hi guys!

Spec:
Civic 97'
JDM B18c-r(cometic headgasket, arp headstuds, super tech valvespring)
Full-race turbo kit(ramhorn, 3" dp, tial Wg 44mm, gtx2867 .82 a/r)

So, I have a strange problem. I had a hondata 3-port boost controller. With that I could easily tune it to have flat boost curve of 15psi. When I tried to bump it up I could get 20psi in the midrange, but in the topend I would loose boost. Sometimes I end up with Wg Spring pressure(4psi), or everything from 7-14psi. It's never consistent. I logged the pwn, and when I loose boost I discovered that the pwn goes from ~85% to 99%. So I was sure of that the boost controller went past its operating range.

I have know mounted hondata 4-port. The pwn is now on 75%, but same as before it just goes up to 99% in the topend(<7000rpm). It doesn't happen everytime. Sometimes it just "bleeds out" around 4-8psi.

Can a boost leak cause this kind of problem? Car is otherwise really strong and I can hit full boost around 4500rpm(20psi)
I'm running gearbased target boost in hondata.

Sorry for the poor English🙃

Engine bay
http://i769.photobucket.com/albums/x...ps0rzh03wi.jpg

Re: Loose boost on the top end
 

Your wastegate spring can't stabilize the increased boost pressure, regardless of what the solenoid is doing. You're going over 5x what the wastegate spring can handle, and it can't handle 5x the rate. It really can handle on average about less than half that, so about 15psi.

5psi of boost pressure is a lot to have as a change, although most people don't think it's that much. Most people that do this say that you can run BBG at 4psi and that's why they get it, but it doesn't help at the higher levels. You don't reach more than about 5psi or so in 1st gear anyway, due to the fact that the cams allow for so much vacuum to stay out of positive boost pressure.

Solution: increase your wastegate spring to a bit higher (at least 7psi) and readjust your PWM and solenoid so that the duty cycle is lower.

Re: Loose boost on the top end
 

Thanks for the replay. I have now ordered 0.4bar wg spring(running 0.25bar). Ill change it and see if that stabilize it.

Re: Loose boost on the top end
 

For 20psi , I recommend at minimum .47-.5bar. .4bar will still have issues.

Re: Loose boost on the top end
 

I see. I have already ordered it. I know I have a 0.5 bar spring, but I don't know where it is. I will try looking for it then. Thanks I again!

Re: Loose boost on the top end
 

No problem, and good luck. But, just a tidbit of advice: don't rush to order anything until you remember about which one to order.

@1:16pm EST - 7psi (.5bar) spring minimum suggested.

@1:29pm EST - you order the .4bar instead of searching for the .5bar you already possessed instead.

I know English isn't your first language, but.... wouldn't you agree, you rushed it a bit without reading thoroughly? ;)

Now, if you're still losing power after this, you need to check those vacuum leaks if any..

No judgment, not trying to make fun of you.. I'm just stating the obvious based upon a simple time stamp. You kinda walked into that one, there... :shrug:

Re: Loose boost on the top end
 

Hehe, you're right. I actually ordered it 7 hours ago 🙃

I have stored my car earlier at my parents home 400km away. So all of parts is there, and my brother who lives there couldn't find it. I'll be attending a trackday 30th July, and won't be visiting them before that. That's why I ordered the green(0.4bar) just in case I found the blue(0.5) spring when I will be visiting them after the Trackday.

I really appreciate the help.

I also thought it should be a leak, but why only over 16psi and only above 7000rpm? But yes, if the new spring doesn't help at all, I'll go over everything thoroughly.

Re: Loose boost on the top end
 

just run a 4 port

Re: Loose boost on the top end
 

I'm running 4-port boost controller have the exactly same issues.

Re: Loose boost on the top end
 

With the duty cycle and hertz inputs

YES.. Because it's is a mechanical issue..Not based upon frequency. 3 port or 5 port. It's not electronic..It's physics.

Re: Loose boost on the top end
 

hmm I was able to get 18 psi, out of a 5 psi spring havent tried pushing it beyond that

Re: Loose boost on the top end
 

Calm down. Im takin in as much info as i can from school and work. Some of us are vague on the boost control settings on hondatas boost control settings.

Loose boost on the top end
 

I'm not excited, so please don't overanalyze my written response here... but you're just "throwing" something out there without your reasoning behind it. Right or wrong, when you simply throw an idea out like you're in a crowded studio audience of a game show, you think anyone heard you? No..

This concept is beyond Hondata nonsense, it's actually standard electronic boost control methodology. No matter which system you use.

All I'm asking is you put a sentence or two about your logical reasoning behind it, or what you believe is the logic, that's all..It's all good, just put in some effort, man. :).. If you're brain fried, take a break, then come in with your idea..help the guy out...;)

Re: Loose boost on the top end
 

So tried today with 0.8bar spring, and I still have same issue. Could it be a boost leak? It does spool up and holds the boost around 2-3 second, and then it looses to 2psi.

Get a video of this, please. This could be one of several reasons.

Re: Loose boost on the top end
 

Ok, so went through all of the clamps and hose + I changed the o ring on my bov(it had a small damage). Seems like its working now. A lot of rain today, so I'm going to give it a new try when the sun comes again. No video since it worked today.

Re: Loose boost on the top end
 

In the places you are losing boost: increase that area on your boost table by the amount you are losing vs commanded. If it evens out to what you want, you're good to go. I lose about 4-6 psi on the higher rpms of 4th gear, I'm commanding 36psi but it tapers to 32. So in those areas mine is actually commanding like 50+ because my boost controller/spring setup is maxed out.

Give that a shot and see how it works.

Re: Loose boost on the top end
 

Yeah, that is basically what I have done before, but it did go from 18psi to 2 psi this time :p