DIY_EFI Digest Tuesday, March 7 2000 Volume 05 : Number 088 In this issue: Re: Subaru TBI Re: ECT and voltage divider help? Re: Turbo speed sensor ever used ? Re: Turbo speed sensor ever used ? anti-lag Re: anti-lag List member virus alert Re: anti-lag Re: anti-lag See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Tue, 7 Mar 100 10:46:38 +0800 (WST) From: Bernd Felsche Subject: Re: Subaru TBI dzorde@xxx.com writes: >Just down the road from me, good to see some fellow West Aussies on the list. That makes four! >On a different note. I just picked up a Subaru TBI (centre point injection, >think its of a 1.8L import motor), the injector is a 1.6 ohm unit. Can someone >tell me if this has to be driven as P/H or whether it can be driven as saturated >(if so does it need a resistor ?) No resistor required. Injectors are normally driven by sinking current through them; no "ballast" required. The duty cycle of pulsing determines the flow. No fancy timing requirements. It's just a cheap way of implementing an electronically-controlled carburettor. ;-) >The plan is to fit this to my supercharged Fiat 850. You're a dangerous dude! :-) You may be better served with a multi-point injection system. The TBI system you're using is probably limited to delivering enough fuel for maybe 75kW. You deserve at least 100kW. If you drive them in parallel, it's no more complex to drive than the TBI (other than getting some sort of cam/crank position signal), but far more flexible than TBI. >Dan dzorde@xxx.com (Balcatta, WA) >>Adrian Broughton >>1990 Celica GT-Four, 1974 VW Kombi, 1967 Holden HR >>Fremantle, Western Australia >>Just up the road from me. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Tue, 7 Mar 100 10:49:35 +0800 (WST) From: Bernd Felsche Subject: Re: ECT and voltage divider help? Cudabob writes: >>So, my question is, how do I switch something based on this >>voltage? Basically, I want to monitor the voltage to the ECT >>sensor and when it drops to around .4 or .5 V I want to trigger an >>output (that eventually drives a relay). Then, while the output >>is triggered and the voltage >I must have missed something, aftermarket fan kits use a thermal >switch for control. Quick and easy, what's the objection, or reason >to design a circuit? 1. To learn how to do simple control tasks, 2. To remove the need to install a separate switch/sensor. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Mon, 06 Mar 2000 22:06:14 -0500 From: Seth Subject: Re: Turbo speed sensor ever used ? For really high output engines, you don't have to go with as mild a cam as you might think. Some Porsche turbo cams had durations in excess of 360 degrees. I have no idea what the powerband was like, and I can only assume they relied on a resonating/standing wave tuning to make this sort of cam timing work. But I bet it had a fair amount of overlap. - -Seth Bernd Felsche wrote: > > Espen Hilde writes: > > >> mmm - Interesting, I'd assumed air flow measurement and MAP would be > >> sufficient to determine volume of air entering the chamber. Are you > >> suggesting AFM doesn't give an accurate enough figure due to backpressure > >> at the turbo and that MAP in no way assists this - in the circumstance > >> where we have an AFM and MAP ? > > >The AFM dont know the backpressure and therefore the ecu cant predict > >the right advance....we are wanting to be right on the edge of detonating > >here....at a 700hp 2l turbo engine 0,5 degree wrong advance at max torque > >is 40 hp lost. > > The state of the turbo is defined by the operation of the engine. > In theory, the ECU should be able to work it out given sufficient > knowledge and the appropriate algorithm. > > If the *backpressure* is so critical, then you should arrange for > phasing the exhaust pressure pulses before the turbo so that the > exhaust still "scavenges" the combustion chamber as the valve > closes during overlap. > > A reduction in overlap may also be worth considering. You don't > really want internal exhaust gas recirculation if your sole quest if > for maximum power. > > >AFM and a MAP sensor on the exhaust could do the trick if the AFM is > >fast enough. > > Those sensors would not be fast enough and sufficiently resistant to > the 500+C temperatures in the exhaust. If you're getting 700bhp from > 2 litres, you're spinning at close to 10,000 rpm if not more. A > pressure sensor needs to pick up the peaks and throughs at the > exhaust valve to adapt the airflow. > > Similarly, to accurately measure the airflow, you need a fast > pressure measurement at the inlet as well. There are pulsations in > the airflow even with (turbo-)supercharging. Transducers will > typically not give you enough information at high speed. > > Pressure sensors take about a millisecond to respond to a pressure > change. So at 10,000 rpm, you get all of 6 samples per revolution - > not very accurate in identifying the pulsations. (vis Motorola > MPX5700 or MPX4250A) Those sensor need to be mounted remotely from > the engine - else they become soup - so you need to have a pressure > line to the ECU that introduces minimal delay. An oil-filled tube > would improve the response time - you still need to allow for the > speed of the wave propagation to determine precise phasing. > > >How the algorithm or map for backpressure vs .boost should work beets > >me....Ignition retard under accleration when backpressure is higher than > >steady state... > >Its complex...... > >Turbo speed VS. engine rpm wot table? > >A backpressure table of %influens on volumertric filling at wot? > >Use a valve on the exhaust pipe for adjusting backpressure under dyno > >runand fill the tables....a hard day work? > >Different engines responds different to backpressure at different rpms. > > Because of the dynamics of the flow as noted above. Having no > overlap would go a long way to solving the problem. > As you don't have a long exhaust tract, you lose out on taking > advantage of an "under-pressure" to help evacuate burnt gases from > the combustion chamber as you have a turbocharger sitting in the > way, a short distance downstream from the valve. > > If you had freedom in designing your cylinder head and > exhaust valves, I'd suggest that you have one exhaust valve > from each cylinder directed to the turbocharger, opening > first and a second (or third) valve opening later to a > turbo-bypass with the first closing slightly to prevent > return flow. That permits a degree of overlap on the second > exhaust with the possibility of useful scavenging. > > With say three camshafts, a variable timing of the second > exhaust camshaft and hence the valve timing will also > alter the boost pressure - the duration of the second > exhaust opening need only be (guessing here!) about 100 > degrees. The maximum duration would be determined by the > boost requirements and the limit of overlap. > > Also, the greater the advance on the second exhaust, the > greater the scavenging, but the lower the boost. Applying > traditional exhaust tuning techniques (resonance, etc) to > the bypass exhaust would mean more effective scavenging > during overlap as the bypass exhaust is only carrying a > portion of the full exhaust flow - between a quarter to a > third (again, guessing). > > >> I've alwayus wondered what the relationshiup is between boost and less > >> ignition advance - is it simply chamber filling, propensity to ping, or > >> some other presumably non-linear relationship ? > > >Exhaust backpressure is driving the exhaust temp to the roof..more residual > >hotexhaustgasses .more prone to detonation. > > The higher temperature will also contribute to detonation because > the exhaust side stays hot. That may be good for increasing boost, > but not so good if you have to lose power by retarding the ignition. > > If the static backpressure is too high and phasing the exhausts > doesn't contribute to better throughflow, then it may be necessary > to split the inlet and exhaust systems to equally-phased cylinder > groups, necessitating multiple turbo-chargers. > > -- > Real Name: Bernd Felsche > Email: nospam.bernie@xxx.au > http://www.perth.dialix.com.au/~bernie - Private HP > ---------------------------------------------------------------------------- > To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) > in the body of a message (not the subject) to majordomo@xxx.org - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Mon, 6 Mar 2000 20:02:51 -0800 From: "Chris Rhodin" Subject: Re: Turbo speed sensor ever used ? Has anyone ever tried using a microphone in the outlet of the compressor? I'd think you'd be able to sense the pulses off the blades that way. Callaway had a fast response turbo system that used a valve in front of the compressor and a bypass around it. The valve unloaded the compressor side of the turbo when the exhaust was low on energy. The system I know of used a bellcranks and such off the throttle cabel to sequence the throttles. It looked kinda Mickey Mouse but did reduce the lag. If you were to servo the turbo throttle to the turbo RPM i'd think you'd have a much better system. The Callaway used a one-way valve on the bypass, but an electronically controlled one would allow you to control surge by routing aiir back through the turbo. Chris Rhodin - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Mon, 6 Mar 2000 20:35:56 -0800 (PST) From: dennis Subject: anti-lag Boy, I seem to have really sparked something with my last question about anti-lag systems. Thanks to everyone for all of the input. My brain hurts now though:) Well, here goes again. Does anyone know if there is a formula for figuring resonant pulse(ram) tuning in the intake manifold of a supercharged engine? What differences would there be when the manifold is under positive pressure? I'm trying to build an intake for a turbocharged 2.5l Chrysler engine and I can't decide on runner length or plennum volume. Formulas exist for figuring atmo engines, but not supercharged ones. And since this car already leaves the line with 9psi of boost off of the brake, these formulas don't do much good. I know that air temperature is part of the formulas for the N/A engines, but would there be any other variable in the equation resulting from the boost? TIA dennis _____________________________________________________________ AutoSpeed - The World's Best High Performance Online Magazine http://www.autospeed.com - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Mon, 6 Mar 2000 21:54:58 -0700 From: bearbvd@xxx.net (Greg Hermann) Subject: Re: anti-lag >Boy, I seem to have really sparked something with my last question about >anti-lag systems. Thanks to everyone for all of the input. My brain hurts >now though:) > >Well, here goes again. Does anyone know if there is a formula for figuring >resonant pulse(ram) tuning in the intake manifold of a supercharged >engine? What differences would there be when the manifold is under >positive pressure? The speed of sound (Mach 1) varies with the square root of the absolute temperature of a gas, NOT with its pressure. So--if it is NOT intercooled, you need somewhat longer runners to get the same effect. The pulses will be pretty well proportional to the density, thus stronger. You might also want somewhat larger runners--because the friction loss in a tube is also proportional to the density of the gas--but friction loss would be the same % pressure loss if boosted with the same size runners. Greg - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Tue, 7 Mar 2000 00:12:19 -0500 From: "Mike Pitts" Subject: List member virus alert I know, I hate these kinds of posts too, but this one is a real risk since it involves a fellow list member. I just received the worm from his e-mail program. Luckily, I had been warned about this beforehand. Here's a description of the virus/worm from Network Associates: http://vil.nai.com/vil/wm98500.asp The reason I am posting this here is because this virus spreads by e-mailing itself to everyone in the infected user's address book, which may very well include some other list members. Be prudent, never execute e-mail attachments unless you are certain they are safe. Regards, - -Mike - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Tue, 07 Mar 2000 01:22:40 PST From: "mike mager" Subject: Re: anti-lag Greetings! I'm curious, what sort of racing, and what peak boost? Mike >From: dennis >Reply-To: diy_efi@xxx.org >To: diy_efi@xxx.org >Subject: anti-lag >Date: Mon, 6 Mar 2000 20:35:56 -0800 (PST) > >Boy, I seem to have really sparked something with my last question about >anti-lag systems. Thanks to everyone for all of the input. My brain hurts >now though:) > >Well, here goes again. Does anyone know if there is a formula for figuring >resonant pulse(ram) tuning in the intake manifold of a supercharged engine? >What differences would there be when the manifold is under positive >pressure? > >I'm trying to build an intake for a turbocharged 2.5l Chrysler engine and I >can't decide on runner length or plennum volume. Formulas exist for >figuring atmo engines, but not supercharged ones. And since this car >already leaves the line with 9psi of boost off of the brake, these formulas >don't do much good. I know that air temperature is part of the formulas for >the N/A engines, but would there be any other variable in the equation >resulting from the boost? > >TIA > >dennis > >_____________________________________________________________ >AutoSpeed - The World's Best High Performance Online Magazine >http://www.autospeed.com >---------------------------------------------------------------------------- >To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the >quotes) >in the body of a message (not the subject) to majordomo@xxx.org > ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Tue, 7 Mar 2000 10:40:25 +0100 From: "Espen Hilde" Subject: Re: anti-lag Hi! I have seen setups with 2 trottles ,one in front of turbo and one after. The compressor spinns much easier in lower pressure. This was on a dirttrack rally car. I have tryed carb in front of turbo and the adjustability of the output of the engine was much better. After the trottle is open I think the wastegate should be controlled by TPS possition.Adjusting the boost by increasing trottle. Espen - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ End of DIY_EFI Digest V5 #88 **************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".