Dyno results opinions
 

So I finally had my Spotts built 488 dyno tuned. Tell me what you think and what you need to know. I have swapped the rear to 3:55 before the pull. What do you think I might see at the track with just radial tires and some good driving….

Is that torque value correct? It appears to be double the horsepower, I never seen a spread that far apart between horsepower and torque, but could be….

Holy cow torque monster!!!! It made 420hp and 880 lb/ft of torque?

Are you sure you posted the correct dynograph? The hp and torque numbers at the reported rpm leads me to believe this is a diesel application, not a 488 poncho.

If this dyno is of your 488, it’s probably highly suspect.

Also to know what type of number you might run we’d need to know vehicle weight as well.

Someone has to explain the figures to me. How can you have half the HP figure at a higher rpm than the torque value? Also what are the mph figures?

887.0 Torque @ 2271 RPM is 383.5 HP

429.6 HP @ 2980 RPM is 757.5 Torque

Also it has correct the output to SAE J1349 where as most engine dynos use SAE J607

Stan

Not familiar with chassis dyno numbers.
Someone want to break this down that knows more about these things ?
385 HP engines don't have 757 lbs torque.
What would the flywheel HP and TQ be ?

Date on dyno sheet is December 6th of 2022.......
 

Non-believable numbers for a gasoline engine.

Sorry you don’t believe the numbers. I’m driving the car now. It is a torque monster. It was done on a “Mustang Dynamometer” it’s a 3300lb 81 firebird. I have the build sheet from Spotts to prove it. The engine was not cheap….

How is the reported torque at the crank (1223 ) over 330 foot pounds higher then at the rear wheels when the rear wheel torque is being multiplied by the rear gears?

I am assuming that this motor is NA

I’ve posted this Dyno to get reactions from people who have more experience with the process. I’ve never had a car dyno tested before so I have nothing to compare it to. The shop is reputable. The mechanic is a BOP guy who races big cars. He has done quality work on several of my vehicles.

You’re stating that you just had your car tested on this chassis dyno, yet unless I am reading the sheet wrong this print out / test is from 2022.
I don’t think this is your test!

Looks more like a diesel truck engine dyno graph..I'm not buying this..is it April 1st?

Ha. No that’s not the case. I just seems like it was done a short while ago to me. I’m on the 9th year of the build. I went back into receipts and that dyno pull was done when I still had the 3:08 rear in it.

I have the car and the engine in my garage as I write this. The dyno sheet is real. I’ve been on PY a long time and no reason to lie. It’s not me you are questioning it’s the guy who did the dyno….maybe he made a mistake. We did have a short conversation about the numbers though so there was no error about who’s dyno it was. Or maybe you question Paul. Does anyone here know Paul Spotts ? Local tp the PY “Ames Performace” area like myself.

Cost me 1300

Took me a while to get it tuned with the Holley terminator EFI. Paid for two dyno pulls from different guys actually. In the end my friend Mike had the best tune solution. He is a wizard. He resides on this forum. I’m still learning the software….tuning is still beyond me.

🍺🍸🥂

Yup, something stinks here!

I don’t care if you had tested a NA 588 cid motor, your not making 590 crankshaft hp at less then 3000 rpm, it’s pure bs or a mistake!

I’ll ask the mechanic to explain it and let you know what he says.

My duramax has a big spread like that. I've never seen a gas engine do that.

Steve,
You need to understand how that type of dyno works. Rear end gear ratio and rear tire size should make no difference. Normally the test is done in drive 1:1. I talk with someone who did the test in both 2nd and 3rd gear and it made also no difference. In some cases they use a fixed amount for tire to crank and other places do a coast down to try to measure the drive train losses.

Stan

Ok got,and thanks for waking me up this morning Stan, but still something is off with those results.

Ok so sorry for the confusion but like I said that is the first dyno sheet I’ve seen. Talked to the mechanic and he explained to me what’s going on. The torque numbers are indeed wrong on that sheet. He told me some of the differences between a mustang dyno and a “dyno jet ?” machine and how they work. He is standing by the HP numbers though. Sorry if that upsets some of you.

Do you have the dyno sheet with your 3.55 gears in the car?
Paul Spotts built my engine. His shop is a half hour away from my house. I use 2nd Street Speed in Perkadie for my dyno work.

No I just swapped the gears this summer and I am still dialing in the tune. I probably won’t do it again though because of the cost and I don’t think the numbers would change much. I am also not overly concerned with the exact figures. The car has plenty of power for me, but everyone wonders what their car could do at the track.

printout shows 568.5 crankshaft horsepower with the Correction Factor, which is believable, nothing unusual there. I'm unsure of what the rpm of 2950 is measuring, I would expect the horsepower peak in the 5200-5500 engine rpm range. I would think torque to be in the 600-625 range on this 4.5" stroke engine.
Would need more info on car to estimate track times

What's the difference between a Mustang dyno and a dynojet?

Opinions...........

http://forums.mustangworks.com/f12/d...-dynojet-9929/




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The car is pretty much an unmodified 81 firebird. I think the original curb weight was almost 3400lbs. I have aluminum heads, intake, and wheels so it’s still over 3000 easy. Th400 trans, Holley efi, dennys driveshaft, moser 3:55 rear. 275/40/18 rear tires. What else do you need ? I do have adjustable shocks but no drag tires. Headers, 2.5” exhaust, and turbo muffs

I was told one of the differences with the mustang dyno is that it puts a load on the engine while testing while the dyno jet does not which could result in as much as a 10% difference in readings.

568 corrected flywheel hp i believe.

Chassis dyno. Even from dyno to dyno of the same make/brand differences can vary.
In the end, it's a "tuning tool" more than anything else.

It would be interesting to know at what RPM peak power was made and at what RPM was peak torque.
On our 4.5" stroke engine the RPM difference between peak power and peak torque was around 1600 rpm.
Tested on a engine dyno.

Smackdown: Engine Dyno vs. Chassis Dyno
https://www.motortrend.com/articles/...chassis-dynos/



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Here this 488-inch 4.5" stroke Pontiac made peak torque at 4100 RPM and peak power at 5500 RPM. The spread between the two was 1400 RPM.

592 hp and 625 lb-ft of Torque.

https://www.motortrend.com/how-to/48...e1B6OEcjx2OCD4


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"Sorry if that upsets some of you" ?
You put it out there like your engine is making so much unbelievable power it upsets people.
Its not a standard dyno sheet so people have questions.
Seems like its a nice solid street engine that makes around 560 HP, nothing wrong with that. But no street Pontiac is putting out 887 lbs torque, much less 1200.
And that thing has got to weigh way more than 3400 lbs in street trim. Those cars are heavy.

That’s the internet for you. Not at all what I intended. I do understand people get ass hurt over the whole “my rides better than yours thing” though.

I think you just want to believe and that is fine. I have no idea how much HP your engine is making and really don't care. What I and others are pointing out is all of the problem with the dyno sheet you posted. The dyno sheets says 75% drive train efficiency. I believe that is to low yet when you calculate what was used

► 429.6 / 592.1 = 0.72555 which is even lower.

Stan

PS - Let me add 130.7 MPH with a 3.08:1 rear
and a 26" tire is around 5200 RPM
and a 25" tire is around 5410 RPM
and a 24" tire is around 5640 RPM

Appears the RPMs shown are the actual roller RPM’s on the wheel dyno, and are not from engine speed. Like Stan mentioned with a 26 inch tall tire and 3.08 gears it figures out to be around 630 ft lbs of tq@3200 RPM (engine speed, there is a conversion factor) and the max HP is @ 5200 (engine speed).. Usually the software will convert the engine RPM numbers for you from the roller speeds. Appears they either may have printed off the wrong info sheet (roller RPM) or info wasn’t given to them to calculate the engine RPMs.

Thanks for the input guys.

Jay,
With peak torque is at 3200 RPM and peak power at 5200 RPM that suggests a 2000 RPM spread.
I'm certainly no expert here but based on my observations that doesn't look right.

I've already posted a few examples but here are two more....

Another 4.5" stroke
Peak power at 7000 RPM
Peak power at TQ at 5500 RPM
1500 RPM spread.

https://forums.maxperformanceinc.com...=4.5%22+stroke

Here on this 4.5" stroke combination the spread was 1000 RPM and as much as 1400 RPM depending on the intake/carb set up.

https://www.motortrend.com/how-to/cc...-alloy-indian/



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Peak torque always takes place in any NA motor once the limit the camshaft sets on air flow is reached, this of course assumes that the heads , intake and carb are not the cork in terms of minimum port area yet or cfm.

So to me this spread being discussed of being too wide is not so easily carved in stone.

A non expert opinion here, I was suggesting what I thought might be a normal rpm spread between peaks.

Here is one comment that relates....

"I'm trying to understand why some engine have a wide power band between hp peak and tq peak and others don't."


https://www.speed-talk.com/forum/viewtopic.php?t=3549


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Would probably need to see a full graph and more drive terrain details to really give more of an educated guess on what the spread actually is or why it is that wide. Wheel dynos seem like they are hard to compare numbers between other combos or dynos. It could be the torque converter multiplied the torque for a bit at a that lower rpm and the engine’s actual peak tq was higher. If it was on an engine dyno the peak tq and power would more than likely come out closer to a that 1500 spread like your suggesting.

Makes sense, thank you.

And I can relate to your comment about wheel dynos being hard to compare numbers. When I converted to direct port fuel injection on my 505 we were unable to use the engine dyno for the numbers. The dyno facility is not set up for the fuel injection. But for interest I put the car on a chassis dyno. The results were very confusing !



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If say peak hp numbers are correct at 3000 rpm ,How are you going to gear your car to cross the finish line at max hp ?haha,if you ever bring it to the track

If the dyno operator wasn't using an RPM signal, the software may have been using drum speed. This may be why the torque values are wrong as stated by the OP.

The HP may be close, but with the torque being wrong, it may just be an approximation. I have no doubt the engine is stout, but this is really why chassis dyno's are more for tuning than for bragging rights.

412hp chassis 568hp crank,I don't think so.Almost 40% gain?Bullsh..

Large differences like that between engine and chassis dynos are not unusual.

I see it all the time with our stuff as we have went from the engine dyno to a chassis dyno on several occasions.

An example is Dad's engine which made 724 HP on Tony Bischoffs engine dyno. We already know that to be very accurate and not inflated. It was even tested with the exhaust used on the car, no fancy dyno headers that Inflate numbers

Same engine in the car on a NASCAR certified chassis dyno that we've used several times with repeatable numbers he made 505 HP at the tires.
That's a big percentage difference but not out of the ordinary. He's pushing through a 4l80 with the converter unlocked, a heavy 3.5" steel driveshaft rated for 1000 HP and a 12 bolts rear

That whole 15 percent difference that is commonly thrown around on the internet is complete bs. You really can't put a number on it like that and you can't compare one chassis dyno to another. There are way too many variables. The key is to keep using the same dyno and make your tuning changes, that's what it's for. Going to different chassis dynos is going to throw you for a loop and make no sense at all.