Not at full throttle
You only needs 40 or less hp to maintain speeds which is a 160 tq @ 1313 rpm and 80 tq @ 2626 rpm. The drivability is how well your car part throttles through the speeds.
headers vs manifolds on a 318 2bbl difference ????
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Most dyno tests have cams that start at that area of rpm. Any reasonable hot rod even if equipped with a smaller cam like a 220/224@050 should, for best performance, have a converter that flashes around that area even though the cams power band (listed) is lower.
Remember a dyno is testing the engine at WOT, not part throttle.
Mostly because the cams tested at 3K plus aren’t designed to operate under full throttle conditions under 3K.
(That and the above.)
Engine Dyno's are a valuable tool, but in the end all engines have to be tuned once in the car anyways. Dyno numbers can be all over the place and vary substantially. To me, I like the E.T. slip.
ir3333
Well-Known Member
My small cam, stock 340 dart is designed to run WOT from idle up and torque up to 3500 is most important.
WOT from idle or low speed when safe, breaks the tires loose easily but you can't push it on the street to 5500 rpm. And there are straight stretches coming and going from all of our cruz nites were you could run WOT if there is no traffic but even if you stay in it to 90 mph it would only be 3700 rpm. There is no place anybody could run to 5500 rpm on the street safely.
WOT from idle or low speed when safe, breaks the tires loose easily but you can't push it on the street to 5500 rpm. And there are straight stretches coming and going from all of our cruz nites were you could run WOT if there is no traffic but even if you stay in it to 90 mph it would only be 3700 rpm. There is no place anybody could run to 5500 rpm on the street safely.
There have been engines that produced more mph and lower ET's than the dyno suggested.
Try 1st and 2nd at speeds above 40 mph
5500 rpm is about 55 mph in 1st and 95 mph in 2nd but I know what you mean even at full throttle on the street your gonna generally spend more time 2500-4500 rpm than 4500-6500 rpm. But one thing being left out is engines that have stronger well built 4500-6500+ rpm power also tend/can to be stronger under 4500 rpms too in all but the lowest rpm. Key word is well built.Eg a factory 340 makes around 275-300 ish hp at 5000 rpm a well built 340 might make 400 hp at 5600 rpm but will make 275-300 hp around 4000 ish rpm sooner and more usable why a 400 hp engine feels so much stronger. A well build 500 hp 340 might make 400 hp by 5000 rpm and 275-300 hp even sooner. Your not gonna hit those mid rpm power numbers with an RV cam.
Not saying build a 400-500+hp engine for better mid rpm power, but a well put together engine that makes peak power in the 5200-5600 range even if little plans to operate there can give better mid rpm power with little effect down low if done right.
And... it goes the other way too ... big horsepower on the dyno and a snail ET slip with low MPH.
How much experience do you have working with a Dyno ?
Like correction factor, what it's used for, why you need to know what it is and how it affects performance at the track.
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The problem with engines with Dyno numbers and the car not operating to the Dyno numbers are not the Dyno nor the car it is operator of said engine or car not optimizing the rest of the package to run what it's supposed to. If I choose to put a 3500 rpm converter behind my engine that makes peak torque at 5000 rpm it would be a slow turd but it would still have that peak torque.
ir3333
Well-Known Member
That's why care is required watching the videos. In the engine masters video 2.5" exhaust vs 3" exhaust,
they proved the 3 1/2" was superior on a 600hp big block by about 13hp!
But under 3500 rpm the 2 1/2" exhaust was noticeably stronger...and they skipped over that so fast i'm betting
most missed it, but they did point it out. more power up to 3500 rpm is important in a street machine.
they proved the 3 1/2" was superior on a 600hp big block by about 13hp!
But under 3500 rpm the 2 1/2" exhaust was noticeably stronger...and they skipped over that so fast i'm betting
most missed it, but they did point it out. more power up to 3500 rpm is important in a street machine.
Zero experience. Most likely will stay that way my remainder few years of my "working on car life" ... LOL
Okay, yeah the time slip and Dyno numbers can go hand and hand as long as the operator chooses to optimize the car to the engine. Anything can make a car not perform it's best, tune, fuel, suspension, gearing all that and usually doing it all at once is best but yeah a lot of people do things here and there but sometimes forget that every action causes another reaction
That's why I said the dyno is a useful tool. I have nothing against the dyno and wished I had a shop with a dyno it. Actually, I just wished I had a shop!!!!
BasinStBlue
Well-Known Member
Bought a new 69 Dart GT with 318. Added a set of
Doug thorly headers and 2 inch dual exhaust. car slowed
down 3 tenths. LD 4D and 600 Holley. CURED.
Doug thorly headers and 2 inch dual exhaust. car slowed
down 3 tenths. LD 4D and 600 Holley. CURED.
it was tied under 3500 rpm
About 1978, put a set of cheap BlackJack headers on my otherwise stock 73 Duster 340. They leaked, rattled and hung low, but the car ran almost 3/4 of a second quicker in the quarter, even with a traction problem it didn't have with the stock manifolds.
MopaR&D
Nerd Member
The 360 in my D200 got a noticeable boost in throttle response and part-throttle acceleration going from manifolds to 1-5/8" Hedman long tubes. Originally a 2-bbl engine, I swapped on a Performer intake and 1406 carb (along with MSD-style ignition). When I put in the headers I ran 3" pipes (same diameter as header collectors) as far back as I could before connecting back to the factory exhaust. You barely need to touch the gas pedal to get that 4500-lb beast moving, it's pretty amazing. Something I've always found interesting, the engineers knew about the benefits of free-flowing exhaust in HD truck applications for a long time as mine has 2-1/4" true duals that look like to be factory and it's a 1972 3/4-ton pickup. Same goes for newer 3/4- and 1-ton trucks with gas V-8s, sometimes they run dual head pipes back to the middle of the frame or farther into a BIG 2-into-1 muffler and a fairly big tailpipe.
I agree on all your points. Considering this van engine is a stockish 318 that would be pressed to spin to 5k rpm, a dyno of this engine would give more usable info if started at a lower rpm. Even then we don't get much info about part throttle driveability from dyno testing.
Seems some forget about that thing called a transmission that has different gears in it. 5500 rpm in first could only be 25mph.
Ant
Well-Known Member
More justification for me to buy headers, lol.
Dynos are generally dealing with performance engines, usually means higher stall and shift points drops are generally above 3000 rpm. Plus dyno pulls only works well over a fairly narrow rpms so they favor top end.
Unless your running a big cam and or race intake downstairs is fine. Plus hp as a % tq is 25 to 50 % from 1313 to 2626 rpm you need to do bigger tq changes to effect power down there vs 75 to 125 % from 3939 to 6565 rpm.
Richard Holdener did a half throttle dyno run, I forget the exact % but was like 80% of the power and a similar curve wish he did a 25 % throttle my guess curve would be similar still and power % above throttle %.
To me or a post above? IF me, yes.
Not true. If the engine is, let’s say a stock 340 or 360, the dyno can hold the engine and allow the brake at a very low rpm. I have not yet personally seen it under a 2K start point.
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You seem to have forgotten I added the LOL &/or LMAO to help what should be an obvious joke and or sarcasm.
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