Manual Boost Controller

[carlotus]

Gentlemen,

I recently purchased a Turbosmart Manual Boost Controller
from TopEnd Performance. Could someone give me some
advice/guidance on how to fit this.

I have heard that it is not too difficult, but I want to make
sure I know what I am doing first before attempting to install.

TIA

Regards,

Carl

[steve matthews]

Carl how are the breaks doing
You will need them more with this devise.
Steve

[theelanman]

mmmmmmm.........
MBC.....
personally I wouldnt...Id go down the everest chip route.......but its your choice.......and if youve already bought it.....
its all about the fuel cut off.....with the MBC..if I read it right... you have the oportunity to blow the turbo

[carlotus]

Steve,

The brakes are terrible. I am working on getting a front brake kit for the car.

Carl

[GeoffSmith]

Carl, many people have removed MBCs (that includes me) where they were previously fitted and used a Mountain chip instead. You will need an FCD as well as the MBC if you are setting much higher boost - you might want to read Q&A #7 however, as you will be overriding some of the ECU inbuilt safety features.

[tigerdog]

Hi Carl,

MBCs all work the same way, by altering the amount of pressure applied to the wastegate diaphragm/spring. If you look at the turbo/wastegate connection, there's a rubber tube running from the boost side of the compressor to a diaphragm attached to a rod that opens the wastegate. A spring holds the wastegate closed until the pressure fed from the compresser to the diaphragm overcomes the spring and opens the wastegate. If this was the only connection, on the Elan the pressure overcomes the spring and opens the wastegate at about 5 PSI.

If the tube breaks and no pressure hits the diaphragm, the wastegate doesn't open and boost goes through the roof. That's why the Elan has a fuel cutoff at .95 bar (about 13.7 PSI at sea level, 11.7 in Denver).

So how does the Elan boost over this? The stock electronic boost control introduces a leak into the pipe and bleeds off the pressure. This delays the opening of the wastegate. The amount of leak (and thus the amount of boost) is controlled by the boost solenoid valve, that funny round thing at the back of the base of the air cleaner trash can. There's a tube from the boost circuit to the BSV, and another tube to the air cleaner (so the pressure has somewhere nice to go), The BSV is electronically controlled so the amount of leak can be carefully managed by the ECU computer. When the car is cold or at a fault, the BSV stays closed and the wastegate opens early, so little boost. When everything is working normally, the BSV opens (more or less, depending on RPM and throttle position) so boost rises in a predictable way. That's one of the reasons the Elan's stock turbo power delivery is so consistent. The Mountain chips are carefully developed to change the opening of the BSV, allowing more leak and thus higher boost pressures, yet still maintaining all the safety bits that prevent boost if something goes amiss.

In the diagram below, you can see two connections on the compressor: one feeds a little short hose to the wastegate diaphragm. The other goes to the "controlled leak" known as the BSV.



But I digress... you wanted to know how to install an MBC.

First thing to understand is, the MBC takes the place of the BSV. Therefore, begin by disconnecting the electrical connection to the BSV. This will leave it permanently closed. If you drive the car like this, you'll find you never get above 5 PSI.

Next, you insert the MBC into the boost circuit. There are a couple of different types of MBCs. One type introduces its own"controlled leak" into the wastegate boost circuit (sometimes referred to as a "bleed" type controller.) If this is the kind you have, you could place it right next to the BSV. Disconnect the rubber hoses from the BSV and connect them to the MBC, making sure to follow any orientation instructions that came with the MBC. The TurboXS standard controller is an example of this type of MBC. With this type of controller, start with the bleed valve all the way closed, then open it in increments until you get the max pressure you want.

The other common type uses a mechanical ball/spring to keep boost pressure off the diaphragm until first overcomes the spring tension. This type must be inserted into the "small hose" circuit and orientation is critical: pressure from the turbo must first Push against the ball/spring inside the valve, then once it's overcome the spring pressure, flow through the valve to the diaphragm. To adjust this type, start with zero tension on the spring (usually the adjustment screw is backed all the way out) and make sure the ball spring opens. You should see behavior just like with the BSV unplugged. Slowly tighten the adjuster and increase spring pressure on the ball, a little at a time, until you reach your desired max pressure.

A third type is similar to the basic ball/spring and includes a ball/spring plus a variable restriction in the boost path. In this type, the ball/spring introduces a spike in boost pressure; once the spring is overcome, steady state pressure is regulated by a restriction in the path between the compressor and the wastegate. Like a simple ball/spring, start with the least restriction then slowly ease the adjuster in until you reach the desired boost.

Turbosmart seems to make both Bleed and restrictor/ball/spring valves, so you'd best check the instructions on the TurboSmart site. I took a quick glance at the "Boost Tee" instructions. It's clearly restrictor type with a ball/spring to cause boost to build more quickly at the expense of a spike before the wastegate opens. It goes in line between the compressor and the wastegate.

Having written this friggin' thesis, I'll gladly defer to some of the other folks on the board who do this for a living (Knox Motorsports, you know who you are) for corrections, additions and clarifications. I'll also agree with any and everyone who says a Mountain chip is the best way to make more boost. I'll also say Smaug wears a bleed-type MBC because the ECU doesn't know what to do with a non-stock MAP sensor so I'm not even following my own advise.

Finally, regardless of the type of MBC, remember you are removing ALL safeguards built into the stock system. If you ask for full boost on a cold engine, you'll get it. Full boost at part throttle, you got it if the turbo will go there. Engine knock due to boost? You better lift your foot because the ECU can't protect you. And if you try to go above .95 Bar, the car will cut the fuel whilst at full throttle and maximum boost; you will at best be thrown against your shoulder harness, at worst leave tooth marks in your airbag or forehead prints on your windshield.

I hope this helps.

[HJ2]

... Helps to scare... enough

[Aoki Magic Pants]

Carl, many people have removed MBCs (that includes me) where they were previously fitted and used a Mountain chip instead. You will need an FCD as well as the MBC if you are setting much higher boost - you might want to read Q&A #7 however, as you will be overriding some of the ECU inbuilt safety features.

My S2 had a MBC fitted when a purchased it. Although better than the stock boost, I've recently installed an Everest chip and couldn't be happier. No going back now.

[carlotus]

Tigerdog,

Wow! You certainly answered my question completely and in great detail I might add. Your excellent and highly informative explanation has certainly
given me pause. I think I will heed the warnings I received here and stick with a chip and forego the MBC

I want to thank everyone who chimed in, especially you. Tigerdog, I know you went to great lengths in your explanation and I appreciate all
your help.

I think will concentrate on getting my car to stop better with a brake kit before I worry about making it faster.

Regards,

Carl

[steve matthews]

Steve

[Ellie]

For the benefit of anyone reading this post - somewhat belated after this thread petered out - I agree with GeoffSmith ("overriding some of the ECU inbuilt safety features") and in particular Tigerdog who nailed it completely.
As a young mechanic I studied turbocharger systems [in response to very expensive engines comprehensively destroyed due to total turbocharger failure i.e. exploded compressor impellers]. This Lotus control fitted to these Elans is just fantastic.
As I read it, the Boost Control Frequency Valve ("the boost solenoid valve, that funny round thing at the back of the base of the air cleaner trash can") is the heart of it - responding to engine speed (revs) [read frequency], throttle position, intake air, turbo boost and other things via the ECU to deliver precisely the right boost pressure for every piston stroke. Try getting that out of a 'blow-off valve'.
Yes it's nice to get more power, but the 'legendary bullet-proof[ness]' of the Lotus/Isuzu engine is primarily down to this little valve, in my opinion, so altering it is not in the best interests of the vehicle's longevity as I see it. Chapman's philosophy was 'the right balance of weight and power to deliver consistent performance': a mantra not in its ascendency these days, it seems.
"I'd rather have a slower one that gets me there than a fast one that can't go the distance" (ask yer missus).
Now I've spent me 'two bob', I'll shut up yer honour!

[rip]

As I read it, the Boost Control Frequency Valve ("the boost solenoid valve, that funny round thing at the back of the base of the air cleaner trash can") is the heart of it - responding to engine speed (revs) [read frequency], throttle position, intake air, turbo boost and other things via the ECU to deliver precisely the right boost pressure for every piston stroke. Try getting that out of a 'blow-off valve'.

A blow-off valve does nothing of the sort. It opens when there is a pressure difference across the throttle plate to release excess pressure on the engine side of the turbo's compressor. This would otherwise build up very quickly when the throttle closes & the turbo is stil running, mainly during gear changes.
This back pressure would otherwise cause turbo stalling.

[tigerdog]

and in particular Tigerdog who nailed it completely.

awww, shucks, 'twern't nuthin...
The real genius is Alan, whose Mountain Chips have kept the smarts of the system, left in the safeguards and pushed the envelope in a knowing and intelligent manner. If you're going to mod, that's the way to do it IMO.