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Car Forum / Saab Cars / November 2004Manual Boost Control Valve Kick --why?
Hello, in my 1999 9-3, I have replaced the ecu with an abbott performance as well as install aftermarket blow-off valve, waste gate and a manual boost control. When I set the boost control valve a little higher, ie. when the boost valve goes all the way to the end of the red area of the gauge, the car kicks, and the boost starts over again. I have turned it down before though so it doesn't kick at all, but I do loose considerable mid-range boost. Does this have anything to do possibly with my fuel pump? Is my fuel pump possibly not able to keep up with the amount of boost? If so where can I get a faster pumping fuel pump for times when I want higher boost? Thanks Alex > Hello, in my 1999 9-3, I have replaced the ecu with an abbott > performance as well as install aftermarket blow-off valve, waste gate > and a manual boost control. A MBC, morons boost control, is a bad idea. It disturbs the system so much that the Trionic ECU is unable to properly control and protect the engine. > When I set the boost control valve a little > higher, ie. when the boost valve goes all the way to the end of the red > area of the gauge, the car kicks, and the boost starts over again. This is the Trionic systems last attempt to protect the engine. It shuts of fuel delivery by closing the fuel injectors and shutting off the fuel pump. Before this brutal step the ECU tried to lower the boost, but the pressure leak caused by the MBC prevented if from opening the waste gate. > I > have turned it down before though so it doesn't kick at all, but I do > loose considerable mid-range boost. Saabs with Trionic systems should be tuned by software changes, not by introducing leaks that disturbs the control algorithms in the Trionic ECU. If you need more boost you have to get new software for the Trionic ECU and perhaps some new hardware like larger fuel injectors (you can't get more power just by adding more air), turbo, exhaust system, etc.  SignatureG?ran Larsson http://www.mitt-eget.com/saab/ All I can say is I trust this guy a little more: moron 1) http://saabnet.com/tsn/bb/9-3/index.html?bID=84683 2) http://mpperformance.com/smbc.htm > All I can say is I trust this guy a little more: moron Who specifically are you calling a moron? You provide no context for your namecalling. If it's who I think it is, it's an odd way to get a group to like you by calling one of the most distinguished and respected participants a moron. > 1) http://saabnet.com/tsn/bb/9-3/index.html?bID=84683 > 2) http://mpperformance.com/smbc.htm OK, well, enjoy using a toggle switch manually to try to think smarter than a T7 engine management system. After all, what would Saab know about controlling how the engine performs, right? Sorry for calling this guy a moron, but I don't understand why Gary has to use such a demeaning attitude, as well as act so closed off to an idea. Immediately calling me a moron for applying this modification that does wonders. I have spoken to my technician about the MBC, which he has done to his own cars, and encouraged me to do to my own, t5 by the way. > Sorry for calling this guy a moron, but I don't understand why Gary has > to use such a demeaning attitude, as well as act so closed off to an > idea. Please include context when you reply, not everyone's newsreader threads the same way you do. I'm not sure who Gary is, either. Maybe you're seeing posts I'm not? I certainly didn't see the word "moron" from anyone but you. > Immediately calling me a moron for applying this modification > that does wonders. If you're hitting your car's overboost "let's cut off the fuel system before the engine blows up for unsafe load condition reasons" limit, you're doing something to it, but I wouldn't call it "wonderful". > I have spoken to my technician about the MBC, which > he has done to his own cars, and encouraged me to do to my own, t5 by > the way. Right, it makes sense that the person working for the company selling it would say it's a great idea. Do you go to a barber to ask if you need a haircut, or do you ask someone who doesn't have money to gain depending on what answer they give? I mean, knock yourself out and all that with your manual switch, but if you think that you're safely getting power out of your engine, and that you can do this better with an MBC than an engine management system can do, and can do it safer for the engine, go right ahead. However, just the fact that you had to ask what was happening when you hit fuel cutoff shows that you don't understand the system even on a trivial level, let alone to the level needed to decide if it's a valid and safe technique or not. Dave "Not expecting this exchange to anywhere useful or interesting" Hinz I'm going to avoid the flame war here by not quoting anyone... Back to the thread: If you have an Abbott CPU upgrade then get rid of the MBC. It's one or the other. You wasted all the Abbott money when you put in the MBC. REMOVE IT TODAY. The Abbott solution is a much better idea as it retains normal ECU control and protection. If you want more boost than you get from the Abbott then you need to do some serious learning about performance tuning first. No exceptions. Second, I don't personally feel that an MBC is the end of the world. HOWEVER, and that's a big HOWEVER, it should be adjusted so that you never, ever reach fuel (overboost) cut off. That's what you are hitting now. Even with an MBC adjusted properly you loose any knock detection/protection. Other than that, I don't see that there is a heck of a lot of actual _danger_ to a properly set MBC without an ECU upgrade but I'll certainly listen to other opinions on the subject. Bob > I'm going to avoid the flame war here by not quoting anyone... Likewise :) Well said Bob. As a general matter, increasing the power of a car beyond the specification of the manufacturer is at the owner's risk. The main points of failure due to increasing power on turbo cars in general are cracked pistons; and on SAABs, the gearbox. Using an MBC and losing knock protection is a risk. So is using an ECU. I know of at least one classic 900 that uses the hallowed APC system simply for knock sensing and therefore if the LED flashes, the driver knows something is amiss with his MBC setup. He can use that information to re-tune the system. I also know of at least one classic 99T that uses APC to increase power "safely" above and beyond the 140? BHP that the 99T was set to as standard. There's a moral in both of those tales somewhere. Certainly the NG900 and the 9000 tuners seem to champion MBCs for power increases - perhaps the DI setup was not that advanced, but I think T5 and above SAABs should go the ECU route, rather than MBC - the ECUs are doing too much to negate their functionality with an MBC. It's like taking a microwave oven and lighting a fire underneath it :) The Abbott tuning equipment is of a very high standard (and so it should be for the price!!!) and I know that the stage upgrades are sold as kits - you get an ECU chip, but ECU setups of a certain power upwards are sold with exhaust upgrades and air intake upgrades. Likewise, the Speedparts kits. If the car in question has an Abbott upgrade in place, ditch the MBC!!! Simple. NG900s and early 9-3s do benefit from an improved intercooler and that in itself will give a good power boost. Oh, as for hitting the fuel cut off switch ... Well, erm ... (Looks both ways) ... that's the first thing classic 900 tuners bypass :P >As a general matter, increasing the power of a car beyond the specification >of the manufacturer is at the owner's risk. The main points of failure due >to increasing power on turbo cars in general are cracked pistons; and on >SAABs, the gearbox. I agree. However, I think the Saab motor ha shown it's ability to take a couple more pounds of boost than the ECU provides. The stock 185hp NG900 was 11lbs, I think a properly tuned MBC pushes it to 14 and then you hit fuel cut off. Certainly if you push it to 22lbs you are in the danger zone but Saab themselves now push the motors at least a bit with their own upgrades and just general HP increases. It's also worth noting that a *properly tuned* MBC tends to give you boost faster (particularly in 1st & 2nd gear) and _holds_ that boost at higher levels longer - but does not typically _increase_ the boost level itself very much. However, your point about the gearbox is well taken. The 230HP Viggen has gearbox issues. Lastly, the same gearbox & other wear/abuse issues are present with an ECU upgrade too... and the ECU's often boost even higher. >Certainly the NG900 and the 9000 tuners seem to champion MBCs for power >increases - perhaps the DI setup was not that advanced, but I think T5 and >above SAABs should go the ECU route, rather than MBC - the ECUs are doing >too much to negate their functionality with an MBC. It's like taking a >microwave oven and lighting a fire underneath it :) The ECU is always preferred, but at least 15x the cost too. >The Abbott tuning equipment is of a very high standard (and so it should be >for the price!!!) and I know that the stage upgrades are sold as kits - you [quoted text clipped - 3 lines] >NG900s and early 9-3s do benefit from an improved intercooler and that in >itself will give a good power boost. The kit is a good idea... but at least Abbott will sell you just an ECU. That's not really a good thing. >Oh, as for hitting the fuel cut off switch ... >Well, erm ... (Looks both ways) ... that's the first thing classic 900 >tuners bypass :P Yeah, I've heard :-) I think it's actually a nice feature in an NG900 in that even if you mess up the MBC setup, the ECU stops you from doing something _really_ stupid. Of course, it's worth noting that some ECU tuners not only reprogram the boost curve but also raise the cut off to allow higher boost... again the ECU upgrade can actually cause more significant wear issues. With the MBC at least you know you are not exceeding the stock limit Saab engineers dialed in for max boost. Bob > I have spoken to my technician about the MBC, which > he has done to his own cars, and encouraged me to do to my own, t5 by > the way. I bet he has ... Saw you coming, didn't he? I'm pretty certain that most "performance tuning" sites that sell MBCs also state that taking the engine beyond the manufacturer's specification is at your own risk. SAAB has a long history of engine protecting devices that go back a long way before even fuel injection was computer moderated. The APC system as used on the classic 900 as far back as 1982 fell out of favour with the so-called SAAB performance crown and "manual boost" looked to be the way forward. There has been quite an exodus back to APC recently, since a number of breakthroughs in understanding (erm, reverse engineering) the box have filtered through. I'm astounded by how effective SAAB APC is and marvel at the more modern engine management systems. How will you sense engine knock? How will your car be able to adjust to knock? You're affecting how the wastegate opens. When your car tells the wastegate to open, you want it to open. Rather than preventing it from opening, why don't you invest the time to understand how the car asks it to open. Then, you affect how the car does that for more power ... Safe power. Have you looked into BSR or Hirsch Performance plug-in power upgrades? Okay, they cost a lot more than a few quid/bucks for an MBC, but your engine and gearbox will remain intact. If you just want a few cheap thrills, then Turbosmart make an electronically activated MBC. You can have your standard setup and flick a switch for MBC. Just be aware that the cheap option *will* cost you in the long term (or even in the short term). The MBC route is still a little, erm, Medieval :) Paul 1989 900 Turbo S http://saab.go.dyndns.org/ > All I can say is I trust this guy a little more: moron Who is this guy "moron" that you trust? > 1) http://saabnet.com/tsn/bb/9-3/index.html?bID=84683 A link to an Saabnet-article by the most adamant MBC-prophet is not helping you. Be very suspicious about any information posted on Saabnet. Believing that a a simple leaking valve can control the turbo pressure better than the 32-bit processor in a Trionic box is stupid. The author of this article believes that it is possible to adjust his MBC valve to regulate the turbo pressure to sit just below the fuel cut-off limit and still keep the engine protected. At the same time the MBC will eliminate all problems with how the Trionic system handles the turbo. All this using only a small spring loaded valve. Believable? > 2) http://mpperformance.com/smbc.htm They are not going to tell you that their simple, but expensive, leaking valve is bad for your engine. You are free to use as many MBC-valves as you like, but they are still not good for the engine . Boosting to the end of the red sector is too much boost for a stock engine. SignatureG?ran Larsson http://www.mitt-eget.com/saab/ <They are not going to tell you that their simple, but expensive, leaking valve is bad for your engine.> <You are free to use as many MBC-valves as you like, but they are still not good for the engine .> Maybe wire them to a floor mounted dip switch & sideline the redundant electronics to power automatic cup holders &/or a really big dashtop boost gauge ...? Cheers |
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