Preferred Dyno Pull RPM Range w/Data

[AL427SBF]

Reset ...

As cobra replica owners with motors built to perform, tell the forum what RPM range you are interested in for Dyno Pulls to measure your engines performance.

1. 4500 up to your specified max. RPM ... 0 votes
2. 4000 up to your specified max. RPM ... 0 votes
3. 3500 up to your specified max. RPM ... 3 votes
4. 3000 up to your specified max. RPM ... 7 votes
5. 2500 up to your specified max. RPM ... 16 votes

Appreciate the participation, enough data to show most drivers would like to see how their motors build power over the drivable RPM range.

[Barry_R]

Originally Posted by AL427SBF

Barry, to further the discussion ...

Parameters -
1. All engines are in the car and are registered for the street
2. All engines run on pump gas, figure 92 octane max, means Cr probably no greater that 10.5:1
3. Expected peak BHP is ~1 for every cubic inch, e.g. 427 CID is expected to have ~427 BHP
4. Motor was put together properly and broken in with > 2000 failure-free street miles

If a customer came to you for a dyno and requested you measure as much of the power band as is reasonably safe to do, what would be your starting RPM to record data?

Client could have motor sizes of -
a. CID < 351, RPM Start = ?
b. CID 351-427, RPM Start = ?
c. CID > 427, RPM Start = ?

Certainly not Engine Master candidates, but right in-line with good performing street builds.

First I would need to pull the motor out of the car. I own and use an engine dyno. Chassis dynos are great for tuning but the numbers you get have no basis in reality.

Next is that a 1 HP per cube engine in my world is either a pooch or built as a near stocker or towing piece. Something down at that level - assuming proper build and fuel - should be able to be tied to a dock and held at WOT until it runs out of fuel - or the oil temp gets so high that the thing melts into a single blob.

I'd have no problem running one of those at 2500 and my dyno would grab something like that at low RPM without breaking a sweat. But most 1 per cube stuff will be all pooped out by 5500 anyways...so the common 3000-3500 RPM power band holds true.

What you should really be looking for and nobody seems to care about is the part throttle drive stuff. I'll run engines for ten or fifteen minutes at a light loaded 2000 or 2500 to sort & spot check cruise fuel and timing. Even though this is where 90% of the driving happens it's also where owners generally go to the bathroom or call their buddies to report the hollywood numbers....

[Jerry Clayton]

Hopefully this will work
C:\Users\jerry clayton\Pictures\2013-05-03 Komet

Wellllllllll---this isn't going too good, but----this is 2 pulls on a Mustang Chassis Dyno---One with a K&N aircleaner with their extreme top and the other run with the aircleaner off but without the base plate that I like to have to smooth the airflow-there are 50 ft lbs torque and 50 hp between the horizontal lines so you can see that up to about 4200 rpm that it made about 20 hp and 20-50 ft lbs tq differance----



Sorry----but I mistyped some numbers--there are 50 hp/lb tq between the horzontal lines---differances are 10 - 20 or so on tq and 5 - 10 hp maybe 12-15 in a couple spots----- I seem to have memory of other tests where we had 8-12 hp differance but don't remember what size engine------

[ERA Chas]

Barry-you're making the same well-intentioned mistake that Brent and Jerry did. All of your experiences and knowledge have been wasted over the course of 3 pages here.
Some customers you don't want.

[Jerry Clayton]

I think that a lot of the differances in concepts come because of the differances of a eddy current chassis dyno and a water brake engine stand dyno-----the eddy current will add a controlled rate of load depending on vehicle data loaded into the controller computer----it is based on rolling and aero load of the vehicle---a water brake dyno doesn't do that--you add load to hold the engine at the rpm instead of letting it accelerate along a curve representing the vehicles dynamics-------

and then there is the inertia dynos that compute numbers based on time to accerate a weighed load( as in a big steel drum full of concrete---------

[Barry_R]

Not in any position or with any intent of questioning Jerry's data there - but 50 pounds of TQ from an air cleaner change seems like an awfully big change...

[vector1]

Originally Posted by Barry_R

Not in any position or with any intent of questioning Jerry's data there - but 50 pounds of TQ from an air cleaner change seems like an awfully big change...

If the bottom two lines are the a/f ratios, I guess that would be part of the reason plus airflow smoothing of a good base plate.

[Jerry Clayton]

I edited the post where I had mis typed---

[Barry_R]

No problem. I was trying to be "delicate" about that...

[Jerry Clayton]

I used to have a base plate that I could fasten down on the carb but someone must of borrowed it----seems like there was a consistant 8 hp differance between no cleaner and an K&N extremetop 14 x 3 unit------