I'm a senior mechanical engineering student at the ohio state university, and i have this presentation on the horizon. I choose to do a technical comparision of our car's 2 meathods of measureing airflow.

Does anyone know where I can get some fairly techincal details concerning their operations. Any websites, tech articles, anything?

Thanks a lot,

Andrew

 

Hey your one of those guys up the road huh? Well I am at Ohio University and I happen to be doing a presentation on how to modify a TPI Car so I happen to know something about this. I know you don't want just my word of mouth but I do know that TPIS Insiders Hints happens to devote 7 pages to this comparrison. I would Imagine sonce you are an engineering student this is all you would need to complete you assignment. I am also a Mechanical Engineering student. Are you involved with the fomula lightinging team at OSU? I am down here and we almost have our new system ready to go.

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86 Trans Am 355 TPI Rebuilt 700R4 with Corvette servo, modified valve body, and a B&M Torque Converter (2000 rpm stall w/ lock up), 87 350 block bored .30 with new crank, bearings, rings, and magnafluxed rods. Reworked 305 heads with 3-angle valve job. Added in the rebuild was an SLP TPI cam, BBK 58mm Throttle Body,SVO 24# injectors,MSD 6A, Hypertech Power Coil, 1.5 Crane roller tipped rocker arms, SLP Intake Runners and Port matching in upper intake including fully ported plenum, TPIS adjustable fuel pressure regulator @ 46psi, Hooker shorty style headers w/ Thermotech heat wrapping, Custom 3” exhaust with Flowmaster muffler and chrome quad tips, Hypertech Thermomaster Computer chip, K&N open element cone filter on modified MAF per TPIS specs, MSD Wires, removal of A/C hardware and a 1LE firewall cover installed. Also there has been a PST front suspension kit with Hotchkis strut tower brace
http://geocities.com/SunsetStrip/Garage/9548/kyle.html

Kills:
95 Talon TSI, 96 Probe GT, 91 T/A L98, 89 RS, 86 Mustang GT, 88 Mustang LX 5.0, 92 Thunderbird V8. couple or ricers that I think were Civics or Preludes not sure what year, 95 Celica GT-S, 94 Chevy 1/4 ton 350, one of those NASCAR F150's

 

The PROM burning guys might be able to give you the actual lookup tables for speed density..!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Thanks guys. I was thinking that the TPIS book had something, but I didn't know for sure. I might check out the PROM guys later.

Kyle, I did formula SAE last year. I've also been the VP of the sports car club here for ~2yrs.

I'm trying to kill two birds with one stone. I have 2 classes with presentations, and I'm going to cover this topic in both. One is an Internal Combustion Engine Class, and the other is System Measurements.

Thanks again, anything else online?

Andrew

 

Buy the 5th edition of "Understanding Automotive Electronics" by William B. Ribbens. It's about $24.00, and your university bookstore should be able to get it for you. Your ME professors will like the fact that you used a source by another PhD. The book is used in a vehicle control systems course taught here at UT. If the bookstore doesn't have it, try Barnes and Noble's website.

 

not to burst your bubble but dont map sensors measure pressure? and the maf measure airflow? so these 2 are not both measuring airflow, only maf is..
just my opinion. so you really cant compare them in the sense of measuring airflow,, you can though compare how they work differntly in tpi setups.

 

[This message has been edited by ron rizzotti (edited November 02, 2000).]

 

The ECM alters air/fuel ratio to accomodate varying load conditions detected by the MAP (change in pressure). It acts like a power valve or metering rod on a carb (or so I've read).

While true, MAP measures air VELOCITY, and MAF measures air FLOW, the ECM uses the respective data to determine how much fuel is appropriate. This difference in approach is what i'm going for. Maybe I should restate/clarify my project.

Anything else?

 

well maybe i mistated before.

MAF measures AMOUNT of air flowing into engine.

Speed Density systems measure air flow.


I'm not perfect. But that's why i'm doing the paper. This info is from the Camaro Performance Handbook.

 

Here, man, I'll give you a little (edited) section of the book I recommended so maybe it can help you more with what you are looking for.

Speed-Density Systems:

The intake air density, da, is determined using output from the manifold absolute pressure sensor p (MAP) and intake manifold air temperature Ti (IAT) using the following relationship, with the knowledge of the standard air conditions do (density), po and To:

da=do*(p/po)*(To/Ti)

Accordingly, the volume flow rate of air (Rv) and other gases into the engine is a function of the engine RPM, displacement D and volumetric efficiency nv, and is determined by the ECM as follows:

Rv=(RPM/60)*(D/2)*nv

Accounting for the volume flowrate of inert EGR (Regr) into the intake, the actual volume flowrate of air available for combustion (Ra) is determined as follows:

Ra=Rv-Regr

Finally, the mass flowrate of air into the engine (Rm) is readily found with the following relationship:

Rm=Ra*da

Then, the mass flowrate of fuel (Rfm) required for stoichiometric combustion can be determined:

Rfm=Rm/14.7

This method is dubbed the "speed-density" method as it makes use of the MAP and IAT sensor data to determine the density of the air, along with the rotational speed (RPM) of the engine.

Mass Airflow System:

The mass air flow (MAF) sensor makes use of a hot-wire anemometer to generate a continuous signal that varies nearly linearly with the true mass flow rate of fresh air charge, Rm. It is a way of directly and accurately measuring mass airflow.

Hope this helps!

 

That is just the kind of stuff I was looking for.

Thanks everybody!