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From: sweden
Car: Firebid Cab-92/1989 TTA
Engine: 383 HSR TPI
Transmission: TH700r4
Axle/Gears: 4.10
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Hi!
I have just taken a copy of this article,i was wounder if its possible to add 78HP just swap the heads.
Anders
Dyno 2000 Simulations for 350 Chevy Tuned Port Injection ( TPI )
-------------------------------------------------
Thankyou to Mark Muchinsky for allowing us to host his article here. Coming soon are dyno simulations for the GM L31 Vortech cast iron cylinder heads. In order to view the download (dyno simulations) you will need to have "Excel 97", or a later version of Excel on your computer.
-------------------------------------------------
The attached Excel 97 file was my summer project. In it you will find two workbooks. The first workbook contains specs on a number of mild to medium-large EFI compatible small block roller cams (I included the Comp Xtreme Energy series even though they are ground with LSAs of 110 degrees). The second contains the results of a whole bunch of Dyno 2000 simulations I ran.
The simulated engine was a 350 TPI using a large tube runner setup, small tube headers with mufflers, and cylinder head flow data from the Sep 00 issue of GMHTP and TPIS Insider Hints. I tabulated peak HP, peak TQ, and the RPM at which each peak occurs. The factory heads utilized the published compression ratios. I decided to keep the compression ratio of the aftermarket heads constant at 10:1 to reduce the number of variables.
Some general conclusions I came away with were...
1. Heads are more important than cams. Lingenfelter makes this statement in his book and this data really backs it up. For example, replacing the stock cam in an 89 iron head L98 with a ZZ3 is worth 27 HP and 4 ft-lbs torque. If you keep the stock cam but replace the heads with a set of AFR 190s, HP jumps up 78 and torque increase 23 ft-lbs! Even if you yanked the stock cam and installed Mr Peanut in it's place, you made 42 HP more than the factory L98 with AFRs up top.
2. The value of larger cams was greater with the stock L98 and Edelbrock heads. Holding the valve open longer was of most benefit when the port did not flow as well. The nice thing about the TFS and AFR heads is that you can run a short duration cam to retain low speed cylinder pressure with little impact to top end HP. AFR makes this claim in their catalog and this spreadsheet supports it. (NOTE: Too bad Dyno 2000 can't model the impact of flow velocity since this is also critical to power and may cause downward revisions in the TFS and AFR numbers.)
3. The 90-92 L98/G92 cam is the best overall factory TPI cam. It has the HP of the 88-89 cam and the TQ of the 87 cam. This along with the changeover to speed density helps explain why the 90-92s are the fastest of the F bodies.
4. The AL L98 heads are worth a significant bump in power over the iron versions due to the increased compression and better exhaust flow. Between the heads, speed density metering, and better flowing intake, I now know why the 90-91 6 speed L98 Vettes could just walk away from me in first gear.
5. The ZZ3, ZZ9, and Accel 74211 cams were just about optimal for this engine in my opinion. It just so happens that these are probably the most popular for the application. The Lunati 50179 is another excellent choice.
In order to make the data more meaningful, I utilized a color coding scheme as follows. The numbers in the DELTA column that are pink indicate a cam that I felt was either too small or too large for this application. The green color signifies those cams which were acceptable but not necessarily optimal. The "blues" are those cams I feel are best suited to this application. In making this judgement I looked not only at the peak values but also the shape of the TQ curve, it's performance relative to other cams with similar specs, and results from 1/4 miles sims in Dragstrip 2000.
This file represented a LOT of hours of my time. I hope you find it useful. If you have any comments or suggestions for improvement, let me know.
Finally, keep in mind that computer modelling is useful but will never fully substitute for actual hardware experience. Find people running the heads and cams you're interested in and ask how they work in real life.
Mark "why say it in few words when you can use many" Muchinsky.
muchinsk@flash.net
Linkpage:http://members.optushome.com.au/iroc..._dyno/dyno.htm
I have just taken a copy of this article,i was wounder if its possible to add 78HP just swap the heads.
Anders
Dyno 2000 Simulations for 350 Chevy Tuned Port Injection ( TPI )
-------------------------------------------------
Thankyou to Mark Muchinsky for allowing us to host his article here. Coming soon are dyno simulations for the GM L31 Vortech cast iron cylinder heads. In order to view the download (dyno simulations) you will need to have "Excel 97", or a later version of Excel on your computer.
-------------------------------------------------
The attached Excel 97 file was my summer project. In it you will find two workbooks. The first workbook contains specs on a number of mild to medium-large EFI compatible small block roller cams (I included the Comp Xtreme Energy series even though they are ground with LSAs of 110 degrees). The second contains the results of a whole bunch of Dyno 2000 simulations I ran.
The simulated engine was a 350 TPI using a large tube runner setup, small tube headers with mufflers, and cylinder head flow data from the Sep 00 issue of GMHTP and TPIS Insider Hints. I tabulated peak HP, peak TQ, and the RPM at which each peak occurs. The factory heads utilized the published compression ratios. I decided to keep the compression ratio of the aftermarket heads constant at 10:1 to reduce the number of variables.
Some general conclusions I came away with were...
1. Heads are more important than cams. Lingenfelter makes this statement in his book and this data really backs it up. For example, replacing the stock cam in an 89 iron head L98 with a ZZ3 is worth 27 HP and 4 ft-lbs torque. If you keep the stock cam but replace the heads with a set of AFR 190s, HP jumps up 78 and torque increase 23 ft-lbs! Even if you yanked the stock cam and installed Mr Peanut in it's place, you made 42 HP more than the factory L98 with AFRs up top.
2. The value of larger cams was greater with the stock L98 and Edelbrock heads. Holding the valve open longer was of most benefit when the port did not flow as well. The nice thing about the TFS and AFR heads is that you can run a short duration cam to retain low speed cylinder pressure with little impact to top end HP. AFR makes this claim in their catalog and this spreadsheet supports it. (NOTE: Too bad Dyno 2000 can't model the impact of flow velocity since this is also critical to power and may cause downward revisions in the TFS and AFR numbers.)
3. The 90-92 L98/G92 cam is the best overall factory TPI cam. It has the HP of the 88-89 cam and the TQ of the 87 cam. This along with the changeover to speed density helps explain why the 90-92s are the fastest of the F bodies.
4. The AL L98 heads are worth a significant bump in power over the iron versions due to the increased compression and better exhaust flow. Between the heads, speed density metering, and better flowing intake, I now know why the 90-91 6 speed L98 Vettes could just walk away from me in first gear.
5. The ZZ3, ZZ9, and Accel 74211 cams were just about optimal for this engine in my opinion. It just so happens that these are probably the most popular for the application. The Lunati 50179 is another excellent choice.
In order to make the data more meaningful, I utilized a color coding scheme as follows. The numbers in the DELTA column that are pink indicate a cam that I felt was either too small or too large for this application. The green color signifies those cams which were acceptable but not necessarily optimal. The "blues" are those cams I feel are best suited to this application. In making this judgement I looked not only at the peak values but also the shape of the TQ curve, it's performance relative to other cams with similar specs, and results from 1/4 miles sims in Dragstrip 2000.
This file represented a LOT of hours of my time. I hope you find it useful. If you have any comments or suggestions for improvement, let me know.
Finally, keep in mind that computer modelling is useful but will never fully substitute for actual hardware experience. Find people running the heads and cams you're interested in and ask how they work in real life.
Mark "why say it in few words when you can use many" Muchinsky.
muchinsk@flash.net
Linkpage:http://members.optushome.com.au/iroc..._dyno/dyno.htm
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