Dyno HP vs driving feel

General engine tech -- Drag Racing to Circle Track

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Warp Speed
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Re: Dyno HP vs driving feel

Post by Warp Speed » Wed May 16, 2018 1:15 pm

Scotthatch wrote:
Wed May 16, 2018 11:40 am
andyf wrote:
Wed May 16, 2018 12:30 am
Big numbers on the dyno doesn't mean it is fun to drive on the street. I'm working on that exact issue right now with a 512 inch big block that made nice numbers on the dyno but is a real chore to drive. The problem in the car is that the engine doesn't have any throttle response below 1500 rpm. So driving it at low speeds in a parking lot is a pain. Once the engine is over 2000 rpm it is off to the races but from idle to 2000 rpm it is bog city. You typically can't find issues like that on a dyno since you can't really do low speed part throttle testing on a dyno. And the WOT dyno numbers won't tell you how the engine is going to act at part throttle off idle. Some people might not think it matters but if you sell a guy a $20K engine and his wife hates the car since it lugs and bucks every time he tries to drive thru the burger joint then you have an issue. Sometimes you have go with a smaller cam and a smaller carb than what the dyno says in order to have
I have done this very thing

Big block big sheetmetal tunnel ram with 2 650 dp carbs ran flawless at wot but what a bear to drive .... we tuned and tuned and people would come over and say how bad can it be ? I would toss them keys and let them see ..almost all would come back shaking there head .... after a while we realized the carbs will just not meter right with a low pressure drop you get at low rpm and part throttle ... most early Holley carbs need that 20.4 inch of water pressure drop to meter fuel some of today's carbs will work down to 3 inch of water but those cost money ...so I switched to 2 500 cfm edelbrock carbs and yes I gave up peak HP but it was a joy to drive so did not care at all
If Edelbrock carbs fixed it, the Holley carbs should have been fine with the proper adjustments.

RCJ
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Re: Dyno HP vs driving feel

Post by RCJ » Thu May 17, 2018 12:45 pm

Does an engine pull back to max rpm faster if you hold it wot and slow it with the brakes or scrub speed with the driving line etc ...vs releasing the throttle to slow.

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