Answer to making 745i run with chip. (archive)

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The way the hose to the waste gate works is it is taking boost (positive manifold pressure) from the compressor side of the turbo and blowing it in the waste gate valve "lifting" it up the waste gate causing boost to be bled off as boost increases. This is done through the solenoid that hangs off your air cleaner. The solenoid serves 2 purposes. 1, it is controlled by the motronic to open at 6 psi swithcing the positive pressure to "hold open" the waste gate at that point. 2, if the knock sensors detect a knock, it will switch and blow open at any level even below 6 psi. If the hose is unpluged, you no longer have the positive pressure blowing open your valve limiting your boost, but only the actual force of the total boost pressure (which is about 12 psi limited by the spring pressure in the waste gate) (the tuamo waste gate is the same but allows you to tighten up the spring pressure to make even more boost) When the equal boost to the spring pressure is achieved, this will "pop off" the waste gate holding boost to the max level as a constant, not making it progressivle less like the solenoid. If you do not have the chip, you will find unpluging the hose totally usless as your car will shut down before or at 10PSI before 3000 RPMS (83-85) as your current software in your motronic has this safety feature at 10PSI should your solenoid fail or your local mechanic forget to plug it of the hose in. If you have the chip, the motronic will not shut down but will work the solenoid just the same, when the hose is unplugged, the factory waste gate will allow you to have 10-12 PSI of boost constantly once the turbo is spooled up, your car will pick up 1.5 sec in the 1/4 mile and close 10 10MPH not to mention going 150MPH. You will have a 300+HP car with even more torque that will impress the heck out of you. The down side is, you have NO knock sensor protection as the solenoid valve is controlled to "blow open" the waste gate as soon as a knock is detected and it is of course unplugged at this point. This is where you eliminate the chance for detonation with better/alternative fuels. You can buy race gas and mix it with pump gas. I buy phillips B32 108 leaded and I mix 2gal race gas to 10gal pump 93 gas and this will insure you do not detonate and your car will run good at this level. Your factory fuel system is sufficiant at this point as long as it is to spec. You should have roughly 33PSI at idle vaccum, and should go up to around 53 at 10-12 PSI. If you do not have this you could lean your car out and destroy it just like detonation. The factory fuel pressure regulator is very simple. It is not computer controlled and is 100% mechanical. All it does is cause a "block off" to the return side of the fuel system. The more boost it sees, the more blocking off it does therefore raising the fuel pressure to the injectors. The factory fuel pressure regulator is enough for this chip and unpluged hose up to 12PSI, but if you are going to modify your waste gate, you will need to go to an aftermarket regulator that will "block off" even more to raise your fuel pressure up to match the higher boost generated by the tighter spring in the waste gate. At this point you can go nuts and create 500HP if you dare, but I dont think it will last too long.... Where I have mine seems to be a good place as the car is plenty strong, has 355HP to the wheels, will break the tires loose at 50MPH but it should not "self destruct" as the power levels are within the tolerances of the hardware (trans-rear end, etc) . The glory with this entire set up is, you can put this chip in your car... It will not do a thing until you unplug that hose, then you will get you 300HP. So you can go add a little good fuel, unplug your hose and have fun, then simply plug it back in, run cheap gas and your car is back to normal all for the price of this chip..... If you want more, cut your waste gate open, put a washer and a screw to force down the spring as an adjuster, weld it back, add a boost gauge to your car so you can adjust the boost to where you want and aftermarket fuel pressure regulator and the skys the limit as long as you are willing to take chances and have a good set of tools and have a line on spare parts as these cars are pretty rare.

Boost pressure pushing against the spring is what opens the waste gate, dumps part of the exhaust and keeps the turbo from making more boost. I have upluged hoses on turbos before but when you do that the wastegate wont open and the turbo will make ass much boost as it can. If this is whats hapening in the 745 senario then 10psi is all the turbo can make, which I dont beleive is the case. Also, if this was the case, installing a stiffer spring(or compresing the original one) would not change the max boost.

Basically, if you unplug the hose from the wastegate what is controling the boost to only 10 psi????

Yes its NO PROBLEM to unplug the waste gate hose... hows a 260000 mile car running the hose unpluged since it had 80K.... if thats not proof enough for the doubters... you'll just have to find out on your own. Thats the car that made me get into the 745 as I have never seen a car running that hard for so long without tearing up... This is not magic... is basic engine managment... I agree that unpluging the waste gate hose sounds wrong and on my car I have a spring adjustment on the WG but that is ONLY to give it more than 10-12psi that the factory waste gate will blow open and the adjustable will allow you to go more... thats IT. As a test... just go unplug your hose... dont worry you wont hurt your car... watch what happens... your car will go like heck for a few secs then it will shut down.... you just reached 10PSI... thats what this chip eliminates. I am not trying to debate or tell someone somthing wrong... If being a mechanic-shop owner that works on Callaway twin turbos, ZR1s, 928's, Porshe turbos, and many other far more eloborate cars than a little 3.5 with a single turbo does not give me just a little credibility in what I am telling you... then just take it as you may... I am talking from what I have done and would not steer anyone wrong on purpose. In response to tuamo, I believe this is the same chip Tuamo sells but I have never seen one directly from tuamo, I was asked to put it in an 81 for a guy I met locally who had it for a while and contacted me to work on his car... it of course will not work in an 81, so heres one for sale. We basically did not need a chip for his car and it now has a little over 300HP. I traded this chip for a couple of parts I had for it and was keeping it for another 745 I wanted to buy but that did not go through.

And Jens.... if you put the modified WG on your car before you put this chip... it will fall on its face everytime you drive it leaving you to think you have other problems... Factory plugs with .35 gap are pulling 355HP on a dyno out of mine without problems. If you lived in dallas, I would give you a ride and you would not be a sceptic at that point... You can run the "upgraded plugs" but they are nothing special and bosch plugs are much better...

If I had a daily driver 745 I would do this chip, unplug the hose and live with the 300+HP as if you get into the adjustable waste gate, you are more prone to experiment and possibly blow up your car.. The factory one will open everytime at 12PSI or a little less and if you have good gas in your car you will never have a problem and should be able to go way over 200K in your car with this done.

I would like that,
but I would need to install the upgrade,
plugs and waste gate first.

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