DIY_EFI Digest Thursday, 6 June 1996 Volume 01 : Number 158 In this issue: Re: Forced induction on a 2.5 Liter 4 cylinder. Transient Acceleration Sams books on engines and controls Re: Forced induction on a 2.5 Liter 4 cylinder. How about no MAF or MAP? Re: MAF vs MAP Re: Re: MAF vs MAP Re: no MAF or MAP? See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "Josh Karnes" Date: Wed, 5 Jun 1996 17:21:36 +0000 Subject: Re: Forced induction on a 2.5 Liter 4 cylinder. > 1. Bigger motor - My only option in Oregon is the 4.0 6 Cyl. > Our emissions laws don't allow the transplant of any motor into any > vehicle that it did not come in as an option if the Chassis was > manufactured after 1981. BUMMER> And the 4.0 6 cylinder gets in the > low teens for mileage on a good day. Well, my mom's Cherokee with this engine and a 5 speed (2WD) gets about 20-22 regularly in a mix of city annd highway driving. That's with 190 hp, I tell you that Jeep with the 5 speed will smoke about 95% of all cars on the road. I have beaten Mustang GTs in it. It may even run with my Z. I think this engine may be the way to go for you. This is a great engine. > > 4. Super charger - Instant throttle response, Complicated due > to the mechanical installation to drive it. If installed with a > bypass it could have very smooth transition characteristics from > low to high power levels. This may also be a good option, I don't know. I think the 4.0 HO 6cyl would be your best bet if you can get one. The mpg with a supercharger on a 2.5L four is not going to beat the big 6 by much, if any, and the 4.0 will certainly last longer than a blown 4 banger. I think it would be interesting, for sure, but probably not the best option IMHO. Good luck, anyway, and let me know what you come up with :) A supercharger on my BMW might be just what the Dr. ordered :) Later- _____________________________________________________________________________ Josh Karnes joshk@xxx.com Renaissance Man http://www.tanisys.com/~joshk/home.htm Tanisys Technology http://www.tanisys.com Austin, Texas '78 BMW 530i | '72 Datsun 240Z | IZCC #308 _____________________________________________________________________________ *** opinions expressed herein are MINE, ALL MINE!! *** ------------------------------ From: pfenske@xxx.ca (peter paul fenske) Date: Wed, 05 Jun 1996 14:50:00 -0700 Subject: Transient Acceleration >Hi Folks >To take a lesson from the Good Folks at Mr Good wrench transient >enrichment can be handled in a multifaceted way. These folks use both >tps delta and map delta to enrich the fuel mix. This is done in two >ways. Low deltas are handled by adding to the base pulse a amount in >a lookup table corresponding to delta value of tps. High deltas add more >to base pulse as well as a corresponding amount due to Map delta. >Acceleration is also done outside of base pulse with assynchronous >pulses. These happen earlier and at a higher rate than base pulse. >This tends to take some of the computer lag out of the acceleration >reaction. >Just my two cents: peter >Ps I post the sams books on engine control and I have a book on controls >for dummies in a little. ------------------------------ From: pfenske@xxx.ca (peter paul fenske) Date: Wed, 05 Jun 1996 15:03:34 -0700 Subject: Sams books on engines and controls >A good book on Fuel Injection I found was Understanding >Automotive Electronics by William B. Ribbens by Sams. ISN 0-672- >27358-6, LCCN 91-78139 >For those people who really didn't pass controls in University >a good book on controls is Understanding Automation Systems >by Neil M. Schmitt and Robert F. Farwell. by Sams. >ISBN 0-672-27014-5 LCCN 84-51472. These are rather simple books >For the guys that really earned their degrees SAE has many >papers out on FI but concentrate on the early 1980s as the >later stuff is too hairy. >Well have fun guys: peter ------------------------------ From: Frank F Parker Date: Wed, 5 Jun 1996 22:11:41 -0400 (EDT) Subject: Re: Forced induction on a 2.5 Liter 4 cylinder. > David, > > I don't know if this info will be helpful or relevant to you, but I did want > to make you aware that there are other types of superchargers than the > Rootes blower design that may have characteristics more in keeping with your > objective. > > I'm not an engineer, and I drive a Miata. I supercharged it last August with > a Whipple Autorotor Lysholm compressor. The engine is a MAP multiport EFI, > and the pulley that came with the SC gives me up to 8 psi of boost. My 1.6L > engine is 117 bhp stock. Haven't done any testing, but I'm quite sure I have > 50+ more horses. If you don't want that much horsepower, you can install a > bigger pulley, or just don't mash the accelerator as hard. The response is > instantaneous, and very smooth; you can drive it normally with no boost, or > more aggressively with any amount of boost, and the boost comes in at very > low rpms. > > The system has no bypass at all other than the idle air bypass whose inlet > was relocated during installation. As for being complicated, I installed it > myself over a weekend. The "kit" was from Bell Engineering Group, Inc (BEGI) > of San Antonio, TX, and it came with intercooler, custom tubing, assorted > castings for remounting and relocating throttle body and airflow meter, a > boost-controlled fuel pressure regulator, a piggy-back high pressure fuel > pump, and an MSD ignition retarder which I have since replaced with a J&S > knock sensor so I can run whatever octane and timing settings I want. Price > of the kit was about $2500 at the time, and depending on your enginuity > (sp?) in making things fit together, you could probably obtain the same > components and put it together for considerably less. > > This is Miata-specific, but BEGI's web site has some interesting info about > their induction kits. > The address is http://www.tristero.com/sa/business/bell/index.html. > > > Doug Gubbins > Apogee Systems, L&H Technologies > Charlotte NC > > "There's always another bug..." > The Whipple unit as sold by Keanne-Bell and Bell Engineering is the best supercharger. Gets boost lower and uses less HP. Tests done @ Ford show that Eaton, Paxton etc for 8psi on 4.6L motor used 70 hp to make boost while the Whipple used 35hp. Bell's kits are very well thought out. Frank Parker 93 Civic EX vtec custom turbo 89 S-10, 5.7L v-8 with DFI/TFS etc > ------------------------------ From: Mike Klopfer Date: Wed, 5 Jun 1996 22:35:01 -0500 (CDT) Subject: How about no MAF or MAP? Tony Bryant writes: >The solution I have used is to solve two simultaneous equations >to find the air flow: > >AirFlow = M.A.Pressure * VE(RPM) * RPM { Just like in a MAP system } > >& > >AirFlow = CriticalFlow(Throttle Pos) * compressible gas > function(M.A.Pressure) > Since I don't understand some of the terminology used I'm guessing that these are the equations for airflow out of and into the manifold respectively. The following is a piece of a posting a did in the distant past. I'm not sure if its very clear or along the lines of what your looking for but if so it would be easy for me to get a hold of the paper and post the equations. My copy doesn't have the last digit of the SAE article number but it should be locatable given the title and partial number. >constants. The following is my understanding of models given in the paper >SAE 93085? "Transient A/F Ratio Errors in Conventional SI Engine Control". >This is largely derived from the >ideal gas law n= PV/(rT). Where V is the volume of the cylinder, P is the >pressure in the cylinder, n is the number of moles of air?, T is the air >temperature and ... >In the paper SAE 93085? cited above the authors include a volumetric >efficiency term in this equation. >This term is of the form > > ve(rpm, P)= c1 + c2 * rpm + c3 * rpm * rpm + c4 * P > >This leads to the following formula > > injSt= (k1 * P * ve(rpm, P) / T) + k2 eqn 1 > >This article also suggests that the air pressure sensor is slow. So perhaps >an injector width versus throttle angle >and rpm map might respond to transients faster than an injector width versus >manifold pressure and rpm map. This article also has some equations relating >mass flow into the manifold to throttle angle and ambient pressure. By >using these one should be able to derive injSt as a function of throttle angle, >manifold temperature and ambient pressure. There equation is of the form: > > M'= C1 * b1(a) * b2(P, P_0) + C2 eqn 2 > >Where b1 is the area of the throttle opening at angle a and b2 is some >nonlinear function of P and P_0 the ambient air pressure. M' is the time >derivative of the mass of air flowing into the manifold. Using equation 1 to >determine the mass flow into the cylinder, and the fact that at >steady state the flow into the cylinder equals the flow into the manifold >one should be able to obtain the constants C1 and C2 by measuring the >manifold pressure for a couple of values of throttle angle. ------------------------------ From: Darrell Norquay Date: Wed, 5 Jun 96 21:56 PDT Subject: Re: MAF vs MAP At 11:16 AM 6/5/96 -0400, you wrote: >As for acceleration enrichment, we've entered a new arena. Now >we're discussing A/F ratio control, not measurement of inducted >air. If the approach is to add additional fuel, without trying >to measure air then calculate the amount of fuel (based on >measured air and desired A/F ratio), then why add a MAP sensor? >The throttle position sensor is already there. Am I missing a >benefit of MAP-based enrichment over throttle-based enrichment? >Anthony Tsakiris Ah, but you forget - throttle position does not have a direct relationship to engine load. You can have different manifold pressures with the same throttle position under varying engine loads. Thus, the MAP would be giving valuable information that the TPS could not. This may or may not have a drastic effect on mixture demands, but I'm betting that it would sure affect driveability and fuel consumption. This may explain why some MAF based systems have MAP sensors. An additional benefit that I want to point out for the use of MAP sensors in MAF-based systems is for ignition advance calculations. This would need to be modified for engine loading as well, which a MAF alone could not. Knock sensors could be used in place of the MAP for this, however. I guess it all depends on which one is cheaper for the OEMs. >(Should I still be adding these definitions. I recall a past discussion.) Why not? TPS - Throttle Position Sensor regards dn ------------------------------ From: Darrell Norquay Date: Wed, 5 Jun 96 21:56 PDT Subject: Re: At 09:28 AM 6/5/96 -0700, you wrote: >goal. The trick is I want to do a bypassed turbo or Super charger >with a demand clutch to shift it in and out of the system. I'm leaning >toward the mechanical blower because in my 4x4 throttle response is an >issue. Holy Mad Max, Batman... dn ------------------------------ From: arthurok@xxx.com (ARTHUR OKUN ) Date: Wed, 5 Jun 1996 22:58:27 -0700 Subject: Re: MAF vs MAP i think you could use manifold pressure and rpm to calculate throttle position .???? ------------------------------ From: pfenske@xxx.ca (peter paul fenske) Date: Wed, 05 Jun 1996 23:57:54 -0700 Subject: Re: no MAF or MAP? >My pet project at the moment, is a EFI (& Elec. Ign.) system for >I've decided therefore to use a throttle position vs. engine speed >calculation. > >Hi Folks >System you are referring too is know a N alpha >Saw a SAE writeup a while ago. Will dig it up if you want. >Most practical version is Holley Projection. >Uses tps, start switch, rpm and temp compensation. >Fairly simple analog system with base pulse modified by tps >position with temp correction. Need rpm for base fueling. >Could build it with a few op amps, comparators a Pulse Width >modulator, injector driver, and divider for ignition. >Transient by delta on tps. >Still digital nicer. >Well GL: peter ------------------------------ End of DIY_EFI Digest V1 #158 ***************************** 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".