when you put an engine on an engine dyno, and you get the h.p #'s (flywheel h.p.). how much is lost once the engine is put in the car, and ran on a chassis dyno ? i know a certain percentage is lost due to the driveline, but is there a standard % that is lost on all engines ? like if your engine makes 625 flywheel h.p. will 30% be lost on the chassis dyno in general? i know that r.w. h.p. is generally less than flywheel h.p. (and i know that torque is really what matters. he could not give me any torque #'s). just trying to settle a debate about this with someone. you could have a really bad ass sounding small block, pumping 625 h.p. at the flywheel according to the engine builder...but that doesn't give you the proof to go around telling everyone that your putting 625 h.p to the ground. that is exactly what this guy is doing. he had the engine dyno'd by the engine builder and they told him 625 h.p. (no paperwork to back it up), the engine isn't in the car yet, and he's spouting off how the car will run 10's because it's a 625 h.p small block (it's going into a 77 monte carlo, with a stock 350 trans, and stock 3:08 10 bolt....BLAHHHHHHH) i told him that the only way to prove real r.w. h.p. is to strap it on a chassis dyno once the engine is in the car. i told him that he might be a little depressed when he sees the r.w. h.p. #'s. he paid an arm and a leg to have this motor built, and it's still got the stock cast crank, and rods, but it's bored .060 with cast pistons. according to him it's a .494 lift cam, with imsa heads (wtf are they?) a performer intake and a 650 holley. he could have bought a new crate 454 for what he paid to have this engine built. i want to see him cry once he gets some chassis dyno #'s.
I've heard 20% loss as the number generally used for flywheel to rear wheels. Alot of variables that could change that, though.
If its making 600+ hp with cast pistons and stock rods/crank,, it wont live very long. Single 650 four barrel and less than .500 lift,, imsa dirt track heads? 625hp?? Maybe with 300hp shot of nitrous. As to the parasitic loss thru the drivetrain, it will vary depending on what tranny and rearend it has.
You're not a streetracer, are ya? I haven't even met the guy and already know his name. He's Mr Easy Money.
Tell him the only thing that really matters is a time slip. He is full of poop until he shows up with one.
16-18% is a pretty well recognized and accepted range. Higher loss for an auto. Lower for a manual trans. It's ball park accurate.
sounds like a 400hp motor at best. stock th350?? toast. 3.08 10 bolt?? busted why would he spend the kinda cash on that motor in a 77 monte with crap driveline. i'm guessing he's BS'ing you on money spent as well.
Lots of variables here... auto trans or manual, driveshaft - 1 peice or 2, rearend gears, brand of dyno, tire diameter, how the vehicle is strapped down, tire pressure, temperature, etc, etc. There is not an exact percentage of driveline loss for all vehicles. Always, always, always... rear wheel power numbers (HP & TQ) will be lower than flywheel power numbers.
i think you're being nice to even give him 400hp revkev. my 461 olds did 450hp with a similar lift cam, 10.7 compression and a decent amount of work. tell the guy he's full of shit
He probably meant that it was IMCA heads. IMCA sanctions several divisions of dirt track racing around the Midwest. Most divisions are claiming divisions, with claiming prices for motors, shocks, and other items that guys normally overspend on. It sounds like he bought an IMCA modified motor. They have a $300 engine claim. For $300 you get to keep your ignition, carb, possibly intake, fuel pump, and pulley and such off the front of the engine. These motors are built for cheap hp not longevity.
With that setup it sounds more like he will have half that horsepower if he's lucky, you can't properly support 625hp on just a 650 carb and a performer intake not to mention it sounds like to big of a cam for the combo and the crank and pistons will defiantly vaporize if it did have that kind of power, I won't even mention how many things are wrong with the driveline, the quarter mile estimate or the kind of car he is putting it in there are just way to many things wrong here.
Out of curiosity I pulled up the IMCA site. It sounds like he has the IMCA spec heads for their late model division. I was wrong about the claim. It is now up to $525 or $50 with exchange. Here are the specs and part #'s for the head. (D) Brodix/IMCA spec cylinder heads only. No grinding, polishing or altering of any kind. No use of any substance that may change or alter shape or size of ports, runners or combustion chambers. Only alteration allowed to heads are for push rod clearance and to install shaft rocker system. Maximum valve sizes are 2.08 intake and 1.600 exhaust. Valve seats and guides to remain as manufactured and in as-cast positions. Minimum combustion chamber size to be 62 cc volume. Valve angle to remain as manufactured. Approved cylinder heads as follows: • General Motors (i.e. small block Chevrolet) - Brodix # 46 221 • Ford Motor Company (i.e. small block Windsor) Brodix #46 223 • Chrysler Corporation - Mopar - Brodix #46 222
If we all had the time and money we'd use an engine dyno and a chassis dyno. My rule of thumb is 10% loss for manual transmission, and 15-25% for automatic transmissions. Chassis dyno numbers for auto trans combos will put out all sorts of numbers, some of which sound pretty bad but you have to keep in mind that sometimes we dyno with new 4L60E transmissions which can be locked on the dyno, yielding higher numbers, and other days I've dynoed my 2000 Z/28 and dynoed 413rwhp with an unlocked T400 with an 8" converter, 9" rear and 28" slicks. The Z/28 has the worst combo you could think of for the chassis dyno but has run 10.92@122 mph on motor on pump gas at 3350 raceweight. The same engine in a stick shift car would dyno 460rwhp. My 1998 Formula dynoed 680rwhp and went 9.4@144mph at 3500 raceweight. My 2006 Trailblazer SS dynoed 328rwhp and went 14.1@98.5mph. So dyno and then track.
well, i came to the conclusion abotu the IMCA heads that he has...imca stands for IMa Crack Addict. i know the guy is full of shit. back in the 80's i had a pretty built up 396 in a 68 nova WITH 250 h.p. nitrous on it. the best that car ever ran was 11.90 on dot drag radials, stock open 10 bolt with 3:08 gears and slapper bars. t.h. 400, manual valve body with a 3500 stall. he is claiming that the t.h. 350 he has is a stock re-build with a shift kit, stock converter, stock 10 bolt open rearend, stock rear suspension...etc. basically, he's dumping this motor in a bone stock 77 monte carlo. he's basically a moron that has read too many magazines.
yeah i was thinking something like +-30% loss through the driveline depending on what driveline it's running through. my friend has this bad ass 68 camaro and it's fairly quick for a street car (compaired to other street cars like mustangs). it sounds very healthy and it pulls hard. he was all amped up about it, thinking that it had to be making at least 500 h.p. well, i talked him into strapping it to a chassis dyno...the result was 208 r.w. h.p. he was crushed by those #'s. he never claimed it to be a drag car, and never claimed it to "run 10's"...he just felt that it was a pretty quick car. my guess is that if he ever ran this camaro at the track, the car would run high 14's - low 15's at best. it's funny how guys can spout off how fast their shit is without ever putting it on a dyno, or running it at the track. the proof is in the #'s and time slips. but, if you can't put the power to the ground what good is it besides being a tire smoker ?
I don't believe I've EVER seen a legit dyno test (as opposed to a magazine spec 'feelgood' test) agree with factory published power numbers. I am pretty sure that there was never any such thing as a factory 400 HP 455 Olds in a mass produced version. Maybe in the 'only 50 ever built, sold only to factory approved race teams' type of cars, but not the showroom cars. We have both an engine dyno and a chassis dyno. Both are state-of-the-art machines with their own digital weather stations hooked up. On the rail (rear engine, race prepped glide, 9", no driveshaft), drivetrain loss is in the teens (off the top of my head). On the Flash (long driveshaft, 9", TH400, and more power), drivetrain loss is in the low 20s. I've seen it in the low 30s, but that usually indicates something wrong. Most modern cars get into the high teens with manual and low 20s with auto, most older stuff is a few % more loss. The chassis dyno numbers are a better indicator of on-track performance. Chassis dyno time is cheaper. If it's the kind that can be loaded and the load controlled by the software, instead of relying only on the weight of the drum for a load, It is more than sufficient for dialing in your tune-up, diagnosing power loss issues in the driveline (which you can't do on an engine dyno), determining if you have the right gearing, tire size, etc, and if not, what it should be, and estimating on-track performance. The engine dyno is far superior when you are wanting to test multiple parts, do complex tuning like injection, etc, because it is easier to work on the engine between runs, and most chassis dynos aren't set up for cool stuff like exhaust pyrometers on every exhaust port, air and fuel flow meters to measure A/F ratio going in and compare it to A/F ratio going out (measured by the wide band), and a host of other neat features rarely found on chassis dynos. A dyno tune of some kind should be considered the final (not optional) step of any performance engine build. On average, dyno tuning a professionally track tuned engine sees a gain of 3-10%. Your average street car, shade-tree tuned by ear, that sounds and drives like the tuning is close, is more in the range of 10-30%. You simply aren't getting the performance you paid for when you bought those parts, without a proper dyno tune. ALL Dynos measure torque. NO dyno measures HP. How can a dyno operator tell you he can give you HP and not torque? HP is not a unit of force, it is a unit of work (work is a function of force, distance, and time). HP = torque X RPM / 5252. That is the definition of HP. HP cannot be directly measured, it must be calculated. If I paid for a dyno session on my fresh built engine and they couldn't give me a printout, I'd be pissed. Printout capability has been standard since dyno equipment went to recorded data in the late 70s (earlier dyno are just a torque dial that looks like a big tach, and you have to read it on the fly, write down the torque numbers, and calculate HP by hand). Buying an engine rated that high (625 HP) from a shop that does not own a modern, digital engine dyno, is like paying the local crack-head to clean your house. It may be shiny when it's done, but it is sure to be missing something Speaking of which, your buddy is on crack, and here's why: On a streetable engine with no power adders, torque is _almost_ always within 20% of cubic inches. Therefore peak torque on a street 454 being in the 550 ft-lb range is asking a lot (since the 454 is the least efficient and most poorly designed big block out there). To make 625 HP, your HP peak would be north of 6000 RPM. With stock rotating parts? It wouldn't survive the first dyno pull. Plus, in a 4200 Lb land yacht with 3.08 gears, it would be lucky to beat a stock 350 powered Monte through the 1/4 mile - the stock 350 should make more power under 3500 RPM, where the whole race will be with that gearing. It would also be doing well to pull 9" of vacuum at it's 1500+ RPM idle speed, require a 3500+ RPM converter to not stall on the line, and I don't know anyone who could drive a car like that in traffic more than once and keep all of their hair. We went to the first big block Engine Masters Challenge. Limited to 470 CID. No limit on budget, just basic rules like stock valve angle, no roller cams, single carb. Our engine was 630 HP (and the best idling engine in attendance, with 11" at 1000 RPM idle), and right in the middle of the main pack of competitors. Many big name builders came. Many made less power than we did AND they broke. Only a handful beat our numbers by more than a few %. I am pretty sure we were the only engine in the competition that had a factory crank, AND competitive power output, AND didn't break (even after dozens of passes in our dragster after the competition). So I know a thing or 2 about 600+ HP engines. The main pack of competitive engines were between 600 and 650 HP at 465-470 CID. I think almost 1/3 broke before they completed the 6 dyno pulls at the competition, and some of those were built by shops that are big names in racing engines(and have been long enough to be on-topic for this board...). 625 HP from less than 500 cubic inches on pump gas is a tall order, and some of the biggest names in engine building failed to succeed without breaking on the dyno, when the testing was monitored and all the runs were legit, with no cheating the dyno, cheating the fuel, etc. It just ain't easy. As for the IMCA engines - common is 350-500 HP. There is one with a 720+ HP Caddy somewhere in the southwest.... However, at our local tracks, we dyno 400-HP-at-the-wheels cars and 300-hp-at-the-wheels cars, and watch the 300 HP car beat the 400 HP car, and his buddy whose engine builder claimed 550 HP (with no dyno printout). Being competitive in IMCA is more about chassis setup than anything else. Carburetor - at 450 HP, a 795cfm Q-jet beats a 850 CFM Holley because the Q-jet is a better carb. At 470 HP, the 850 CFM Holley edges out the Q-jet, because the Q-jet just can't flow enough air. At 500 HP, an 1150 Dominator (525 HP) stomps an 850 double pumper (500 HP), because the 850 is at it's limit and the Dominator is a better carb. A stock smogger Caddy 500 at 300 HP and 480 Ft-Lbs loses almost 45 HP going from a 795 Q-jet to a 650 Holley. Also, every competitive engine at the EMC we went to had a 1050 CFM or bigger carb. Most 454s left the factory in stock form with 750 CFM or bigger carbs. Airflow + cubic inches is 90% of making power. My money says he'd be doing well to make 1/2 of the power he thinks he has through a 650 CFM carb, unless the rest of the combo is full-on race stuff.
wow...thanks for all that info cadDaddy !!! the engine this guy has for his dinosaur monte carlo isn't a 454...it's a 350, 2 bolt main, bored .060 over. he's not a friend, he's just a guy i see on occasion. alot of people seem to forget that a smaller c.i. engine, making less h.p. can whop ass on the bigger engines if it's put in the right car. chassis setup and weight are a huge advantage. stick a 400 h.p. small block in an impala with stock suspension and it'd be a dog at the track. stick that same engine into a vega with a 4 link...and it would make one hell of drag car.
10 second 1/4 mile if he pushes it off a 1320 foot cliff !! some people talk just to hear themselves make noise.No way that street intake could ever flow that much.350 HP max and the rest of his combo is shit,too.
I use a friends chassis dyno. My th400 soaks up 37 more hp than my th 350. And don't laugh but different weights of different sets of my rear wheels will change my et at the drags. Getting all that rotating mass going.
255hp at the wheels tells me max 340 HP at the flywheel, unless there is something seriously wrong with your drivetrain. Probably closer to 300 if your drivetrain is really well set up. Of course, the dragstrip calculations most people use make a lot of assumptions. For starters, using the standard 'weight and ET' and 'weight and MPH' calcs, 12.0 and 110 MPH give you different HP numbers. Assuming it was one run, your car must have less aerodynamic drag than the number that is 'assumed' by the generic calculation, or any one of many things that can cause the ET and MPH to disagree with the basic calculation. Especially on big-inch low-RPM engines in really small cars, you will get a higher number for HP than you are really putting to the ground in most cases, using the common equation. There are much more accurate calculations, but they require inputing a lot more information, and require much higher math to solve. The dragstrip is also notoriously unreliable as a measurement of engine power just because there are so many variables that can affect ET. A stock '70 Eldo is rated at 400 HP also, but makes 323 HP on the engine dyno with an HEI and better springs, but otherwise stock. Of course, if you look at a '76 500, it is rated at 190 HP (30 HP less than a '74 472, by the way, which is identical in every way except for stroke), but the '76 500 makes 302 HP on the dyno. Since the only difference between the Toro and regular 455 is the Toro has a more restrictive oil pan (kills off power compared to the RWD pan), and the non-toro engine is rated lower, that alone makes the numbers suspect. Also, lets not forget that the Toro and Eldo are the same car aside from body character lines and the engine. And the Eldo has a few hundred pounds more weight in gadgets, extra body bracing, insulation, etc. The 500 and 455 are both rated at 400 HP. The 500 makes more power, and the Eldo is faster. So a stock '400 HP' 455 is less than 320 HP. I'm not an Oldsmobile expert, but on the Caddy, the rated 400 HP is listed as being at 4400 RPM. A stock production engine has valve springs that are so weak that they are floating so bad by 4200 that the power numbers are dropping like a rock. And while I'm not an Oldsmobile expert, I know that the stock 455 valvetrain is more fragile than the stock 500 valvetrain, and the Toro and Eldo have the same tall gear ratio and high weight, so the Olds should be set up for big bottom end torque, not high RPM HP, just like the Caddy, or the Toro would be a total dog off the line. Technically, '71-older HP ratings are supposed to be 'gross' HP - a theoretical number that that engine, with the carb and intake port CFM, cubic cinches, compression ratio, and cam lift and duration should make IF it achieved 100% volumetric efficiency (very uncommon, especially in production cars) AND had zero internal friction (impossible). However, that calculation was then 'edited' by the marketing department before it was published. There will always be those who stand by the factory power ratings, or their engine builder's power ratings, like a bible. But really, unless you have had your engine on a legit dyno, any power numbers are nothing but guesses.
The Jalopy Journal
