Try doing a search on boost spike.
Its really not good to experiment with 26psi on low octane fuel.
For the most part porting your o2 will take care of that problem.

 

my joe p mbc spiked bad, as much as 5psi sometimes. i have since made a simple hardware store bleeder valve, no spring or ball bearing or any of that stuff. just a regular valve. i get absolutely no spike, no creep, and it cost $4. oh and my boost doesn't come up any slower than with the joe p. mbc...in other words, get rid of it.

marshall
streetdynamics.com

 

marshall, would you mind posting the plans to that , or a link to the plans?

 

well, there really aren't any plans to it, it's as simple as possible. it's a brass adjustable valve with a hose barb on one end, the other end goes to atmosphere. it's T'd in the line between the compressor outlet port and the wastegate actuator.

here's a picture of it: www.streetdynamics.com/members/marshall/talon/CAI/PA300091.JPG

marshall

 

boost controllor

what if you just took the spring out of the boost controllor and tighten the valve down more

 

First for the person that replied about porting the O2 I have the S20G which has a special O2 housing which is custom stainless steel and its bigger than the stock one. I had a ported EVO housing and still spiked. Porting the O2 only helps with Boost creep. I'll try the idea since I always though it was the JoePMBC that did not work. Would you happen to have a part number or anyhting I can go by when I go to Home Depot to get it? Thanks for the reply.

 

Mine spikes as well (JoeP). Actually, boost is all over the place with mine. Spikes in some gears, underboosts in others.

I'm actually thinking about going back to the stock BCS for now.

I posted about it and did some research and arrived at the conclusion that it was because of the small t25, but seeing your experience makes me wonder now.

I'd seriously consider a Profec B if I thought I could get better results but I'm not 100% convinced it's a MBC issue, I might have tsomething else going on.

 

I use a mbc that I bought off the DSMTrader, and I get no spike. I was getting spike with the mbc I was using, so I got this one. It works perfectly. I got it for $20, and I still have the guys e-mail address if you want it.

 

Yeah give me his e-mail I'll try a new one out.

 

ahhh, boost creep. just get an extenal wastegate thats all

 

ive never been able to stop my boost creep, i always thought it was becuase of my 3" tb no cat exshaust and too small of a o2 housing/wastegate. i am going to try this out tomorrow, if it works, marshall,you will be my new dsm hero.

 

I have a turboXS mbc and it creeps 2-4 psi as well. Thing pisses me off to know end. I have been told Dejon tool makes a nice unit, I may give that a try.

 

Ok. the guy I got mine from is a guy named Phillip Robertson, and his email is philip485@hotmail.com . Got it for $20, and I get no spike. That one that Denjon tools makes is kikass because you can set 3 different boost levels (one for first, one for second, and one for 3rd - 5th), but its kinda pricey for my current budget. I will eventually upgrade to it, but got lots of other stuff I want to spend my cash on first. Also, it does no good for AWD cars. Just for FWD since we are traction limited.

 

We are not talkin about boost creep. Boost creep and a boost spike are different. Boost spikes seem to be caused by the boost controllers instead of it being something else that can be controlled if you know how like boost creep.

 

"Proceed..........on your way to oblivion" - Unicron

This was from Transformers the Movie. The voice of Unicron was Orson Wells who died shortly after the film released, it was his last movie. This movie is a classic if you were ever into The Transformers. Your quote brings back memorys

 

I've had an Extreme mbc for over 5 years on my car and I've maybe seen 1 psi of boost spike and it holds boost very rock solid.

 

Humph, I have a joe p with no problems. I get a 1 psi spike when tapping off the BOV line. If I tap off the turbo elbow, I don't get any noticable spike, but full boost happens slightly later. SO, tapping off the BOV line, I get 10psi by 2800 rpm's, and 15psi by 3000rpm's.

I've noticed that the joe p doesen't like to be set at low boost levels such as 10psi. I think it was "tuned" more for 15psi. Anyhow, I don't know why you guys are talking about this on dsmtalk when joe will be glad to help you out via his personal e-mail. He sends every customer of his his e-mail link, and he'll be very nice and respond quickly.

 

I run 15 - 16 psi, T'd off the BOV line with no spike.

 

I built my own MBC and I have never gotten any boost spike over 1psi. I search and copied a couple of designs for a MBC and instead of using a spring and ball bearing, i used a spring and rivit design for it to block out air, I will try to post pics of everything taken apart because I have 4 extra ones at my house.

 

Spike can be caused by not a large enough volume of air flowing through the MBC lines and the MBC himself, and by hoses that are too long. First, check to make sure that all the hose connections are tight (once I found one of mine was so loose I could turn the hose). Second, try to relocate the MBC so that the hoses are as short as possible (for me that means it goes by the MAF or the thermostat). Next, replace those hoses with bigger ones (I like 6mm). If these two things do not help enough, try this:

If you follow the hose that comes from the PCV valve, you will see it has a nipple on the manifold. I have re-rouded my PCV valve (it's a good idea, see the procedure here: http://www.dsmtalk.com/forums/showthread.php?threadid=55057 ), so I had that nipple plugged off. All I did was un-tee the BOV line, and hooked the MBC up to the manifold. The nipple of the PCV hose is huge, and if you have ever looked at the actual hole for the BOV line it's rather small.

With this done, you have a seperate source line for the MBC and BOV, and you will see much less or no spike.



Creep is a totally different subject, which myself and others have proven can be fixed by porting the WASTEGATE EXIT AREA. You need to make it easier for the gasses to flow out, so you opne up the bottom of the WG area and the part that it mates with on the O2. Simply porting the O2 won't do anything for you.

 

I must say, that is some of the best info I have read on solving boost spikes I also have my PVC re-routed and the manifold nipple pluged. What size hose are you using for that setup? Should I use silicone or standard tubing? The reason I ask is cuz silcone hoses seem soft and may not be ridged enough to give the MBC an good press signal.
Why didn't I think of doing this

 

-Next, replace those hoses with bigger ones (I like 6mm). If these two things do not help enough, try this:

-if you have ever looked at the actual hole for the BOV line it's rather small.

THe BOV signal off my 90' is like 3/8", the same as the hoses supplied with a Joe P. MBC. At 15psi, their is no spike. Just keep those lines short.

I tried tapping my MBC off my PCV system, but I got a horrible boost oscillation.

 

Well.. I am still having problems with boost spikes I tryed something diff today wich seemed to help. I took the PVC line on the mani and T'ed it together with the bov line on the mani as well. Now I have double the signal, no more pressure or vac, just more air. Is this wise to do? I don't see how I could be messing anything up. The bov still gets it air signal just like before, just from 2 of the same source off the mani. I am still getting 2-4 psi spikes though Maybe it's time to change the MBC.

 

Both of them are seeing the same pressure since they are on the intake manifold.

 

Well after cutting down the size of the hose, getting larger diameter hose, trying different locations I still get real bad boost spike. After some more searching I saw a guy say he had it real bad until he did a leak check and fixed his boost leaks. I also started noticing that it will only do it on 3rd gear since that is when I am tuning I do 3rd gear pulls. On 4th and 5th it will hold whatever I have it set for. Could it be that due to my open exhaust there is too much pressure on 3rd gear due to the higher load causing the WG to open up lowring boost?