I don't see how a bleed hole in the control line to the wastegate will reduce a boost spike. Bleeding control pressure only increases boost. The purpose must be to relieve residual pressure when boost goes down.

 

Wow, for the first time In my life I agree with you. I've overboosted with the accuboost so I'm not sure what they mean by "overboost" protection. The only thing I can think of is if it fails is that it would cause an underboost situation instead overboost.

Many moons ago I ran an LBE with the CV deleted and without the bleed hole the residual pressure in the WG line made turo response between gears terrible. I would have to give it 5 seconds or so before the line pressure bled off enough to allow the WG to close.

 

Thomas, you are right, that is the purpose of the small hole in the mbc. No other reason. I guess you can argue that it will "dampen" the signal going to the wastegate and by doing that cut down on spikes, but I doubt it. You will have to run a higher spring pressure when you have the bleed hole. I dont like the design, but as of now I dont have any other ideas of letting off pressure in between shifts. It would be interesting to experiment with different hole sizes and compare how it effects boost in the next gear.

There is a lot of questionable information in this thread. For one, there is no such thing as runnning a mbc in dual port mode, to do this you would need a solenoid, controlled by a boost pressure switch, and this would make the setup fall under the "electronic" category.

Also, a car is going to overboost with EBC just as easily if the line to the normal wastegate port breaks. In fact, it will do it even faster than a single port wastegate will, not that this amount of time will make any difference.

If you do not know what you are talking about, PLEASE do not imply that you do, that is how accidents happen.

 

I just installed a Greddy Profec B spec 2 and found it to work really well. It has a feature that allows you to show peak boost achieved during the last period of acceleration (good to check for boost spikes) as well as a feature that sounds an alarm if a predetermined boost level is exceeded. You can also set it to automatically drop the boost back to a safe level if this ever happens.
If a boost spike is detected, you can adjust the EBC to change the way in which it opens the wastegate to avoid boost spikes.
Well worth it for $300 - especially since I was looking at the cost of replacing (another) failed stock cycling valve and with the EBC, I could just eliminate it from the circuit.

 

sorry, i hadn't really thought about it that much, but i was paraphrasing what i'd read in one of the other threads:

https://rennlist.com/forums/showthre...highlight=hole

now that i think about it, with the help of Danno, it doesn't really make sense i guess . he seems to have had the same experience as Jeremy:

https://rennlist.com/forums/showthre...lbe+bleed+hole

 

maybe I got bad advice in that thread, but I haven't read anything to dispute it. Remember, I am using a factory wastegate. When I upgrade to a tial I'm going for EBC, no doubt. I think EBC will really let a dual port wastegate's advantages show up!

BTW, I made the modifications mentioned in the thread, I am running around 17psi now that it's cold (16 to 16.5 when it's warmer) and I get full boost at 2900 in 5th with an approximate 0.5psi spike.

 

If I am wrong, can someone please correct me as to why the hell Lindsey says that it is a MANUAL boost controller and it can be run in DUAL port mode. I guess I have been misled again.

 

Derek, for the money and piece of mind, a EBC is a good investment. Even with one of the Greddy units, you get a good amount of functionality, especially since you dont have a gauge to tell you how much boost you are running if over 1 bar! You also wont have to worry about ambient temps raising your boost levels, which can be significant in cold weather!

 

Ummm you get less boost when its colder? Did I read that right?

 

All I see on Lindsey's sight is that a MBC can be used with a dual port wastegate. This is true, but it is pointless, since you will only be using one port.

 

woops, meant warmer. Fixed it now.

 

UGH, they told me it had a dual port mode, as in it runs in dual port mode, as in it is a dual port controller, as in i am confused.

 

If you guys by a “boost spike” mean a brief temporary boost peak above the intended (steady state) maximum, then it would be wise to look into the diameter (and length) of the control line from the banjo bolt to the wastegate (through the boost controller). The smaller (and longer) the line, the longer time it takes to pressurize the chamber on top of the wastegate (= open the WG).

 

Yup, again, I do not recommend using vacuum lines for the boost-control function.

 

Just don't let it become a habit.