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#21
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Higher chassis dyno numbers from auto trans car you say?
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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! |
#22
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No, the chassis dyno numbers are lower. The auto equipped car wastes more energy getting the power to the rear wheels. So to make up for this inherent loss the conversion factor needs to take this into consideration. A manual car losses "about" 15% getting the power to the ground. Basically the 1:1 drive only has some bearings taking a little power and the rearend, universal joints and wheel friction losses contribute to the remainder. An auto trans car also has loss through the torque converter, transmission pump, and other parts so it looses more. Someone before us came up with the loss ratios and did so hopefully by trial and error.
Looking at it from the reverse side, an engine that produced 400 horsepower on an engine dyno should be expected to produce about 320 horsepower in front of an automatic and 340 with a manual on a chassis dyno using the 20% and 15% losses.
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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. |
#23
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All great info. For fun I found this computation to get a rough idea of power:
https://www.mk5cortinaestate.co.uk/calculator4.php
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"No replacement for displacement!" GTOAA--https://www.gtoaa.org/ |
#24
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OK, let's add another fly in the ointment. What if the dyno guy runs the car in drive with an overdrive transmission. For instance say a 700R4 where 4th gear is a 7/10 overdrive gear.
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If you built it, drive it. red 62 Tempest total stock restoration. white 62 Tempest modified, 61 389 Tri-Power, and a conventional drive train. |
#25
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Paul Carter made a good point about not using percentages - the amount of loss would go up the higher the power output of the engine.
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Will Rivera '69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears '64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears '69 LeMans Vert, 350, #47 heads: Non-running project Last edited by grivera; 03-06-2021 at 09:45 AM. |
#26
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Quote:
On an engine dyno, we almost always run the engine, no accessories, open headers (sometimes they are dyno headers which inflate the numbers), rarely ever has an air cleaner on it, and the engine temp is controlled, usually well below what you'll see in a car. When installed in the car, the air cleaner is in place, a full exhaust system, all the accessories and belts, the hood is up with a fan blowing on it but it's really up to the car and it's cooling system to control temps, so you get much closer to real world running conditions. I haven't had one yet that has shown less than 100hp difference from a dyno to the car, and I'm betting I have one here that's even worse. Planning to put dads car on a chassis dyno, and we already know it made 724hp and 764 tq on an engine dyno running pretty much just as I described above, no accessories, through the chassis headers used on the car. I'm going to bet it will struggle to push close to 600hp at the tire. More like upper 500's is what I think it will do. |
#27
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Quote:
Dennis |
#28
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71 GTO, 463, KRE 295 cfm heads ported by SD Performance, RPM intake, Qjet, Dougs Headers, Comp cams HR 246/252 ...11 to 1 , 3.55 cogs, 3985lbs.....day three- 11.04 at 120mph ....1.53 60', 6.98 1/8 mile |
#29
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I know someone in the UK that owns a rolling road. I don't know who the manufacture is. He told me that after the dyno test he can do a coast down test and then is able to give an approximation of flywheel 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 |
#30
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I addressed testing in different gears in reply #15. Does not make a big difference. What CAN make a difference, is being able to lock the clutch on some modern converters. With a looser converter, locking the clutch can make a 40+ hp difference, and make for a much more accurate graph.
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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 |
#31
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#32
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At an 1/8-mile track, I was running 7.0x with the green-line converter.
The red-line converter was MUCH tighter than it should have been, and cost me nearly a tenth just on 60' time. Don't remember exactly, but somewhere in the 7.teens-7.2 range. The third was an experiment by the guy who made the green-line converter, using a hybrid 8" converter. I'll have to see if I can find the dyno for it. At the track, the car blew through that converter, not useable at all.
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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 |
#33
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We used to run at least 6 vehicles in both types of testing to get an AVERAGE Coast Down Time and calculated Road Load Horsepower to submit to the EPA. Each vehicle would do a 14 run Track Test each night for several days in Florida or at the Proving Grounds in Michigan or Arizona. And there were 6 or more vehicles in each segment of the Vehicle Line (Mustang, Cougar, T-bird, F-150 Truck, F-250 Truck. We would also run a test vehicle at the Lockheed Wind Tunnel in Georgia and weigh it at different curb weights to get body height, and Frontal Area effects of each segment in a vehicle class. So when you take your single vehicle and put it on a rear wheel dyno and make a couple of pulls and then try to compare that with drag strip data, I have to smile as you are way short on the info you need to do the job correctly. When we did Emissions Testing we always ran on the same dyno for the series of tests at the EPA. The track testing, (14 runs 7 in each direction) each night for 10 days = 140 runs on actual track conditions to get a number that was close for EPA Testing. Most enthusiasts get less than 10 runs on a dyno test at a hot rod location. Great bragging rights but actually, as some have said, does not match actual track data unless you actually run on a track under consistent conditions. Discussions like this one as I said make me smile. Simulations are ok for discussion too but are not the same as actual Track Data under controlled conditions on the same day and testing is over multiple days with one driver using very expensive monitoring equipment to record the data, VS looking at a screen and writing down a couple of numbers. Engine and Wheel Dynos can be "tricked". Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. Last edited by Tom Vaught; 03-08-2021 at 01:04 PM. |
#34
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Quote:
A very involved process is required to get close to the right actual answer. Many $$$,$$$s involved in getting actual close to reality answers. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#35
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I think Tom's posts 33-34 provided the actual truth to the problem of determining true horsepower/torque. When I consider the costs of all the dyno tests generally available to most people, I begin to think that when Pontiac Jim in another thread said the "butt dyno" was good enough for him, he was right to some extent. If your engine/trans combo makes you feel good about the power you have then your good. If not carefully research the best ways to increase that power.
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"No replacement for displacement!" GTOAA--https://www.gtoaa.org/ |
#36
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I went to a "dyno day" then had a "computer tune on my '04 GTO-stock. Same shop but they had a Mustang and a dynojet. 10 HP difference before any computer tuning. One 280 RWHP one 290. Don't remember which.
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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 |
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