jrogers

I thought I should do a follow up to my previous post on a manual boost control I had installed a while ago. After driving with this in for a month or so, dialing it up, down, etc. I was not real happy with the overall performance of the motor, and I wasn't really associating the problem with this control. The boost came on where it always had, down around 3000 RPM, but seemed slower building. Also, if I got up to 1 bar of boost I was getting a cutout at high RPM, like it was my overboost limiter cutting out, even though it was set to 1.3 bar.

I pulled out the overboost sensor to check it had not drifted in calibration. Sure enough, it was right at 1.3 bar. Next I pulled out the 'Joe P MBC' and the .7 bar spring, and put back in the .9 bar spring. -- What a difference! I am getting a much quicker spool to 1 bar, and no more cutout. If someone else would like to try this, I will send it to you, since I won't be putting this back in my car. A nice concept, but it doesn't seem to work well in practice, at least in my case.

A930Rocket

I was thinking of the manual boost control, as it would be simple compard to an Apexi, etc. and hard to go wrong with. Now you have me thinking otherwise...

rickc

I did a great deal of research before settling on a manual boost controller, and have been quite pleased with the reliability. I went with the dual TurboXS unit, and its functioned flawlessly, although not cheap in comparison to some of the other manual units. This particular unit has two settings (low/high) via a toggle switch in the cabin . Its a little hard to dial in initially since you must adjust it manually at the controller, but you know it's working unlike some of the electronic units that rely on stepping motors or senders. I am also using a digital boost gauge to monitor and adjust settings, and to record peak boost. I did have to go back to the stock wastegate spring and remove the 1 bar spring to make the system work at the lowest setting.
Rick
'78 930

A930Rocket

rickc,

Who make the TurboXS? Any links, info, etc?

Brent 930

TurboXS makes it, you can find them at turboxs.com. I have there high performance controller but now using the Greddy Profec-B. It's not bad and very easy to hook up and use. BUT, there is a design issue when you modify from stock. What I mean is the tube size of the inlet connector is very small(the intention is to help reduce spool time) but will cause serious over boost. So I had to drill it out to tube size and re adjust it. Plus it's not as consistent as the EBC and will lag spool up just a little more. You get what you pay for most of the time.

rickc

This is an age old debate. Whats more reliable...mechanical or electrical. There are differences between the single and dual stage mechanical units, especially TurboXS. Brent is right concerning the "you get what you pay for thing". I like the ease of installation with the electronic boost controllers, and the good units are generally very quick to spool up. I had also heard long term reliability issues with some of the stepper motors and sending units, so I went the mechanical direction. I am curious to hear others weigh in.
Rick
'78 903

A930Rocket

I had an APEXi AVC-R, but sold it, as it would take an electrical engineer to install it and set it up properly. It wasn't really made for the mid 80's 930's I think. A simpler EBC is better.

Brent, I see you made it to The Rennlist from the 911 Turbo Club. I think you'll see there is a lot to offer here.

Jim

Brent 930

Yeah, the APEXi is better used for an EFI setup where there are more electronics to tap into and monitor.

Thanks Jim, there is alot of info here and your motto is cool.