Real world dyno results

av8rds · May 18, 2010

So I had to take my truck on the chassis dyno yesterday to tune out some detonation so I figured I'd share some results.

I attached the actual engine Dyno results from when it was built. Its a 393 with .060 over(398), AFR 185 heads, Edelbrock EFI upper/lower, and a custom cam(which I, at this point dont have the specs for but it was a TQ setup)

So the overview is at 3500 rpms its making 181ft/lbs and 122Hp at the wheels, at 3900 it jumps to 200HP(climbing to 230ish) and 270ftlbs(climbing to 291) of TQ. This is WAY down from the Engine Dyno sheet I attached. And the engine dyno shows a big TQ jump at 2400/2500rpm not up at 3900???

My tuner thought it was from the TQ converter locking up but I seem to remember it only locks up in 4th gear(Chevy 4l60e). I'm gonna have to look at the software and check as thats making a huge difference if thats the issue. Not that I really need any more TQ down low, I really dont.

So over all on the chassis dyno:

Max HP = 232@4239rpm/69.6mph
Max TQ = 291.4@4051/61.5mph

down from the engine dyno of:

Max HP = 381.7@4300rpm
Max TQ = 504.8@2900rpm

This is with the 398, 4L60e, Atlas 4sp, 4.88's and 36in Iroks.

recoiljunky · May 18, 2010

If it makes you feel any better, here's what my new 398 Stroker with Edelbrock heads, Performer intake, Holley 660 TA, Comp Cams X4262H cam did on the dyno:

My EB has an NP435, D20, 4.56, 36x12.50 TSLs.

I swapped my intake to an Air Gap and I'm still finishing up my cam swap (XE284H.)

av8rds · May 18, 2010

oh good thinking I forgot I took a picture! The run is listed my MPH not RPM though, it just happened to be the one he had on the screen.

recoiljunky · May 18, 2010

I was sorely disappointed when I got mine chassis dyno'ed. I didn't have the motor dyno'ed by itself, so I thought something must be wrong with the motor. Parasitic drag must be a mother on these EBs. I always thought that my 398 was a ~400hp / ~400tq motor.

broncnaz · May 18, 2010

Big tires and less than optimal gearing will drag the power right out of a engine. once in high gear where the actual testing numbers pan out you really see the losses. It can be hard for big tires to actually provide enough traction for the dyno as well.
I think a lot of people end up being a little disappointed in dyno numbers. As a lot of people think they must have the big numbers. Also the cams we tend to run wont make those big numbers and I really doubt a 262H cam would come close to making 400hp on the engine dyno

lonesouth · May 18, 2010

curious what a new truck would show on a Dyno...My 4runner is supposed to kick out 270hp and 330lbft of torque, which is hard to believe for a 4.7ltr

understanding that tires and gearing kind of make this and apples and oranges discussion

I'll see if I can dig up the dyno sheet from my ATK reman 351

fwilder · May 18, 2010

my mostly stock 302 would be flat embarrasing :-[

DonsBolt · May 18, 2010

broncnaz said:
Big tires and less than optimal gearing will drag the power right out of a engine. once in high gear where the actual testing numbers pan out you really see the losses. It can be hard for big tires to actually provide enough traction for the dyno as well.

I agree if you put a set of 33 or 35 inch all terrains on, I bet you would get a lot better numbers. Also if you have a doubler between the TC and the trans, will reduce your numbers.

MattW · May 18, 2010

Different brands of dyno's can have an impact on your numbers too.

recoiljunky · May 18, 2010

broncnaz said:
Big tires and less than optimal gearing will drag the power right out of a engine. once in high gear where the actual testing numbers pan out you really see the losses. It can be hard for big tires to actually provide enough traction for the dyno as well.
I think a lot of people end up being a little disappointed in dyno numbers. As a lot of people think they must have the big numbers. Also the cams we tend to run wont make those big numbers and I really doubt a 262H cam would come close to making 400hp on the engine dyno

I know their software has got to be a little biased but....

389.4 hp

With the 262 cam, my motor would light up my spooled rear end with 36" TSLs and get away from you if you weren't careful.

broncnaz · May 18, 2010

Yeah I think the software tends to be a little biased. In that its only computing parameters not a actual engine. While I would say thats pretty close for engine numbers. but I would always expect less.

Broncobowsher · May 18, 2010

This was from about 5 years ago. http://azbronco.org/a504trip.htm
It had 4 Broncos and the dyno numbers. The dyno operater included a guestimated correction factor that we also put in there.

That old 351 was fun even though it was under 250HP at the wheels. But the 300 ft-lb sure made it fun!

av8rds · Jul 6, 2010

In a couple of other dyno threads they has suggested using smaller tires for better hook up and better numbers.

I was ok using my bigger tires as they hooked up ok and I didnt want some exaggerated HP claim. I wanted real world results.

This weekend I put on some baby shoes(33*12.5 AT's) to try to narrow down a vibration. Usually run 36*13.5 Irocks at 6pis offroad 10-15 psi on road.

Some observations:

1) spool with more tread/softer sidewall(Irok)=very acceptable on street spool with these tires=bad!

2) burnouts are a blink away. Without that big soft tire absorbing some HP, its gone from very fast off the line to a monster. I have to be very careful about 1st gear and quite a few times the shift to second resulted in more chirping if I wasnt careful.

So in conclusion if you want to up your numbers I think smaller tires are the way to go, like I said I wanted 'my' world numbers so I'm happy just observing that I was shocked it made that much of a difference.

Justafordguy · Jul 6, 2010

lonesouth said:
My 4runner is supposed to kick out 270hp and 330lbft of torque, which is hard to believe for a 4.7ltr

Is that all? My old pickup's 363 has 435HP/720TQ, It smokes a little but I think I can take you. LOL

Quick & Dirty · Jul 6, 2010

Most chassis dyno's are the inertia type. They calculate horsepower by how quickly the mass of the drum can be accelerated. If you have a lot of rotating inertia in the vehicle (heavy tires/wheels, driveshaft, t-case gears, transmission) that adds to the accelerated load but is not part of the calculation.

If you can find a brake type dyno that measured a steady state rather than acceleration, the numbers may look better.

An old drag racing rule of thumb is 1 pound of tire is worth 10 pounds of body for the effect on acceleration. The inertia dyno does give a realistic picture of the ability to accelerate, as heavy tires are a significant drag on the power available.

The engine dyno may also have been "corrected" for standard conditions, and the chassis dyno wasn't.

recoiljunky · Jul 6, 2010

That's the best explaination I've ever heard regarding chassis dynos. Thanks Q&D.

Real world dyno results

av8rds

MAhole!

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