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#1
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Chassis Dyno Power to Flywheel Power?
This is a chassis dyno (DynoJet) for a '71 455HO engine that made an average best of 332 hp and 436 ftlb torque. How does that translate into flywheel numbers?
Dennis |
#2
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Your posted 332 hp is not average best as you have said, but it's the true peak hp on the most productive pull!
Is the car auto or manual trans? If auto the flywheel hp could be as high as 390, if manual trans it could be 415 hp. What was the motors average water temp during these pulls?
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#3
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Steve25, M22 manual trans and 3.42 rear gears. The engine was rebuilt back in '05 with .030 forged pistons (CCP's?), stock rods with ARP bolts, 8.6 to 1 compression, factory RA (2 1/8" outlet) exhaust manifolds, HO intake & 7041267 Q-jet, and an early Pypes 2.5" mandrel exhaust system with 'X' pipe and Racepro over-axle muffler.
Dennis |
#4
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IMO the numbers don't translate. From our experience chassis dyno numbers are all over the place, especially with an automatic transmission.
But it looks like a nice build. |
The Following User Says Thank You to PAUL K For This Useful Post: | ||
#5
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I had one chassis dyno guy tell me slicks vs street radials even make a difference.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#6
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Interesting articles...
https://www.hotrod.com/articles/1106...-engine-dynos/ https://www.onallcylinders.com/2012/...u-should-know/ Related topic here on PY: https://forums.maxperformanceinc.com...t=chassis+dyno .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#7
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Agree with Paul K.
To further illustrate, I've attached a graph with two different chassis dyno tests on it. This graph is the SAME car/motor/tune. The ONLY difference was that the torque converter was changed. Flywheel HP was unchanged, so how could any formula account for that much difference? I later tested a 3rd converter, and it provided a graph that was nothing like either of these! Also, always get print out of the HP/TQ plotted against wheel speed, as well as against RPM - especially if you have a looser converter.
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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'. '67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust My webpage http://lnlpd.com/home |
#8
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Quote:
The first think you need to understand is that most chassis dyno software uses a different dyno (weather) correction factor than a engine dyno uses. Note the SAE 0.98 and 0.99 baseline. That is reducing the measured HP. On an engine dyno that would have been around 1.02 to 1.03 which would have increased the measured HP. Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#9
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Thanks everyone for your posts. I see now that it is an 'impossible-to-answer' question, just too many variables to consider to make any direct correlations to flywheel data.
Lee, you chassis dyno'd a low compression 455 as I recall...can you repost those? I'm not trying to compare the two 455's, just curious to see what yours did again. My 455HO was rebuilt back in 2005 when it was in the Chicago area and was then chassis dyno'd in 2010 when it was in the Toronto area before I bought it in 2015. It had a Comps Cams XE 276 (230/236/110) when dyno'd (since changed). Dennis |
#10
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As I said about there different weather dyno correction factors that can be used. You dyno sheet says "SAE" and Lee's says "STP"
Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#11
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I think Lee's comments are good. I've always wondered since rear end gears multiply torque of the engine to rear wheels how that does not affect chassis dyno numbers also.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#12
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It's impossible to answer, but the track data is the most fun to get.
I wish that I'd been able to get my motor on an engine dyno so that I had that data to go with my chassis dyno and track data. My ET slips (with some math) show 50-65 more HP than I've ever been able to print on a chassis dyno... It's way more fun going to the track anyway, and Alamo City Motorplex has a taco stand that I really like.
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77 Trans Am, 469 w/ported E-Heads via Kauffman, matched HSD intake, Butler Performance forged rotating assembly, Comp custom hyd roller, Q-jet, Art Carr 200 4R, 3.42s, 3 inch exhaust w/Doug's cutouts, D.U.I. Ignition. 7.40 in the 8th, 11.61@116.07 in the quarter...still tuning. |
#13
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Quote:
Without getting in the math. While the rear end gears do multiply torque. They at the same time also change tire / roller RPM. Stan
__________________
Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#14
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Quote:
1. This is my own 455. Stock "66" casting heads, bevel-edged pistons, CR ~7.8, 222/242 HFT cam 116lsa, .443/.435. tri-Y headers, 3" exhaust, Performer intake, Q-jet, automatic with stock stall. 2. 400 with SD Performance ported 6X heads. CR ~ 8.3:1. 2.5" R/A manifolds, Performer intake, Q-jet, 4spd manual tranny. HR cam, 224/236, 115lsa, lift just under .540". 3. 455 built back in '03, using box-stock Edelbrock heads, pretty sure they were 85cc. Cam is a Crane HFT single pattern, 228/228, 112 lsa, lift was somewhere in the .530-.540" range with the rockers used. Stock intake with a Q-jet. Doug's headers and a good exhaust (don't remember specifics). Transmission was a switch-pitch THM 400, with the testing done with the converter in the tight position. Owner's desires were "run fine on pump gas, and I want it mild enough that my wife can take the kids to get ice cream in it." I talked to him a few years ago, and it was still running fine.
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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'. '67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust My webpage http://lnlpd.com/home Last edited by Lee; 03-02-2021 at 03:55 PM. Reason: typo in #2's valve lift |
The Following User Says Thank You to Lee For This Useful Post: | ||
#15
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Quote:
Stan & Skip, I've done/seen some testing in different gears, and the differences have been less than expected. They are usually a LITTLE different, but a few times no real difference at all. The mild 6.0 LS in my Cutlass put 386 to the wheels in 2nd and 3rd gears. Oh, in post #7 above, I mentioned testing 3 different torque converters and getting 3 totally different looking dyno curves. I forgot to mention that all 3 of those converters were SUPPOSED to have the same stall speed!
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'73 T/A (clone). Low budget stock headed 8.3:1 455, 222/242 116lsa .443/.435 cam. FAST Sportsman EFI, 315rwhp/385rwtq on 87 octane. 13.12 @103.2, 1.91 60'. '67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust My webpage http://lnlpd.com/home |
#16
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Quote:
Dennis |
#17
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Quote:
Dennis |
The Following User Says Thank You to SD455DJ For This Useful Post: | ||
#18
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Not necessarily related to the OP's topic at hand, but Lee's comment in his post #15 should be be well noted........
"I forgot to mention that all 3 of those converters were SUPPOSED to have the same stall speed!" This knowing the torque converter is often stated, and should be, a great "bang for the buck" when it comes to performance enhancement. Like a camshaft catalog operating range, don't always rely on what the catalog states about a torque converter, this regarding the stall ! .
__________________
'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
The Following User Says Thank You to Steve C. For This Useful Post: | ||
#19
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Quote:
We always have to make allowances when attempting to convert rear wheel to flywheel horsepower or vice versa. a conversion factor estimates converter slip, and the more converter slip the higher the ratio. Manual trans have no slip and the power train loss is loosely figured at 15% while a "normal" converter with an auto is figured at 20%. As soon as converter slippage changes the ratio changes also. The converter with the lowest rear wheel horsepower has to be the one with the most slippage. I could see a loose converter needing a 25% conversion factor. So in my "normal" world 332 rear wheel horsepower would be converted using 332/.8=415 for auto, and 332/.85=390 for manual. If the converter was sloppy, then we might have 332/.75=442 flywheel horsepower. Is this precise? Hell no. Other than ripping out the engine and sticking it on an engine dyno after running on the chassis dyno, it's the best we have -- and at least makes for some light conversation at the end of the dyno session.
__________________
Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon in progress. |
#20
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"You and I use the same conversion figures, but you swapped auto and manual numbers. So auto is 415 and manual is 390 at the flywheel."
I can agree with this statement from lust4speed as many 455HO's with similar builds to this particular one have engine dyno'd at 400 hp +/- and 510 lbft torque +/-...so the 15% is close. The 455HO we last dyno'd made 430 hp and 535 torque (stock w/8.6 SCR and a Summit 2802 cam, through the factory exhaust manifolds and 2.5" mandrel headpipes). Dennis |
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