Chassis Dyno Run

[jsawduste]

Made 4 pulls today on a chassis dyno. 3rd pull was a bad one.



1st pull was cut at 5000rpm. The rest where allowed to bounce off the rev limiter. Where is was still making HP.

The dyno itself was running without a 9% correction factor. Meaning that the numbers need to bumped by 9% to be true readings.

The peak HP was 185.7@ 4600 plus the 9% gives a total of 204.27

The peak Torque was 241.4 @ 3550 plus the 9% gives a total of 265.54

I am still running the stock MAP and a plug check after the pulls showed the engine running lean. Over the winter I plan on adding one of Jeff`s adjustable MAP sensors and cranking in some additional fuel. Which I suspect will boost my numbers.

Parasitic drag was determined to be the the area of 30-35%. So the above numbers plus 30-35% will give a rough idea of power at the crank.

For comparison this picture from the November 2011 issue of JP where they chassis dynoed there Mopar stroker.


There power levels were 161 HP and 230 torque for the Mopar stroker
and
130 HP and 177 Torque for the stock 4.0 Not sure of the year of the stock engine..

This thread is a bit rough in it`s format but the information is there.

Do understand that it is impossible to compare dynos. But at least I have some idea of how the engine is running and what kind of numbers it is putting out.

The guys at Burns made a video that will be uploaded to YouTube. Soon as I have a link I will post it up.

[Cheromaniac]

Your dyno numbers of 185.7rwhp @ 4600 and 241.4rwtq @ 3550 are pretty respectable especially if you have an auto tranny. An AW4-equipped stock 4.0 XJ will typically put down around 130rwhp and 175rwtq so you're about 40% higher than stock for HP and 35% higher than stock for TQ, with more to come when you've corrected the leanness.
I'd just ignore the 10% "fudge factor" that the dyno operator added to the chassis dyno numbers to derive engine HP/TQ.

[CobraMarty]

Nice. Auto or manual? What brand dyno? Besides the stroker, what are your mods?

[jsawduste]

Nice. Auto or manual? What brand dyno? Besides the stroker, what are your mods?

NV4500 transmission

The engine is built as follows.
93 4.0 block that was bored +.080. Mains and cam journals were line honed.

12 cwt 4.2 crank swinging Eagle H beam rods that are a bit longer the the stock 4.0`s. Custom Diamond Racing pistons set for a zero deck height. FF pins. Actual static compression is 9.56. .043 of quench

Entire rotating assembly (including the clutch) was balanced.

Hesco 274/480 cam (advanced 4 degrees) pushing Mopar roller rockers in a ported and polished 7120 casting head.

Late model curved intake manifold with a 63mm TB and 24 lb. injectors.

Edlebrock header with 2.5 exhaust.

Modified crank sensor that adds 5/6 degrees of timing and the IAT was relocated to the cold air intake.

HV oil pump and high flow waterpump.

Engine has about 10,000 miles on it. The pulls were done right off the street. That is no fresh plugs or any type of tune up.

Over the winter I will go into the harness and add Jeff`s MAP adjusters. Have the adjuster it is setting on my workbench.
In addition a Currie RockJock rear axle is in the works for this winter. It will help flatten my driveline angle out and may have an impact on parasitic drag.

Will find out next spring when I do a few pulls.

[superstingray77]

Nice Numbers!! , how much head work was done do you know what your flow #'s and valve sizes are?

[jsawduste]

Nice Numbers!! :-) , how much head work was done do you know what your flow #'s and valve sizes are?

Thanks,
valves are the factory`s with a 3 angle cut. The bowls were opened up a bit and the short side radius smoothed out. Gasket matching completes the head work.

[Cheromaniac]

NV4500 transmission

Still a good dyno run despite the tranny being a manual (with its lower parasitic HP/TQ loss) rather than an automatic. I just realised that your rpm scale was 9% low, so dividing both your maximum rwhp number of 185.7 and 4600rpm by 0.91 yields 204.1rwhp @ 5055rpm. The maximum rwtq number remains at 241.4 but it's at 3900rpm instead of 3550.
It's a crapshoot trying to guesstimate crank HP/TQ from the dyno results but I'm going to try anyway. I ran your engine specs through my desktop dyno and got 275hp @ 5100rpm with 318lbft @ 3800rpm. The rpm peaks are remarkably similar so it seems the drivetrain loss might be about 24% at peak TQ and 26% at peak HP. Seems reasonable given that your tires are bigger/heavier than stock and that your NV4500 is much heavier than the original AX15.
By comparison the drivetrain losses on my own XJ (AX15, stock tire size, stock drivetrain) come to about 17% at peak TQ and 19% at peak HP so your heavier hardware seems to add about 7% to the drivetrain loss (unless all of my earlier calculations are way off base).

[jsawduste]

Dino,
thanks for the review. In this case the actual numbers are not gospel but somewhat of a baseline for future pulls. In any case I am pretty happy with the results.

Having mentioned a plug check showed the engine running pretty lean at WOT. If we assume an arbitrary AFR of low/mid 13`s now and an improved AFR of the mid 12`s. What would you expect the numbers to do ?

Just curious to gather an opinion and then compare it too an actual pull.

[Cheromaniac]

Having mentioned a plug check showed the engine running pretty lean at WOT. If we assume an arbitrary AFR of low/mid 13`s now and an improved AFR of the mid 12`s. What would you expect the numbers to do ?

Difficult to say without knowing your current AFR readings. I guess the proof of the pudding is in the eating but consider it a very good result if you gain at least 5lbft across most of the rpm range.
My own AFRs started lean on the dyno with 14.1 at 1500rpm and became progressively richer with rpm to 11.8 at 5000rpm. That was essentially the "sweet spot" with the stock PCM programming and my MAP adjuster set at 5.3v. Richening it up would probably have yielded better low rpm response where the engine runs lean while losing higher up where it's already rich. Leaning it out would probably have the reverse effects and lower the threshold to pinging at low rpm.
Ideally you'd be looking for a flatline AFR near 13:1 right across the rpm range but the only way you're going to achieve that is with a programmeable piggyback computer. Even then, the power gains may be too small to justify the cost especially if you can achieve a good compromise with the MAP adjuster alone.

[Biggrnjeep97]

What tire/axle combo do you have? And were you allowed to run "large" tires? Point being, id love to go get a chassis dyno done but im not certain theyd be thrilled with me running 40" egg shaped swampers! Ive followed your jeep on another forum and have been impressed with your work, Good job!

If we assume an arbitrary AFR of low/mid 13`s now and an improved AFR of the mid 12`s. What would you expect the numbers to do ?

FWIW,
The guys at the local track recommended i tune for a 12.0 at WOT. My understanding is the additional fuel prevents the compressed charge from "prematurely overheating", ie knocking, allowing you to push the timing a bit farther forward. I may be wrong but these guy have much more powerful motors than i so i wasnt going to argue.

[SilverXJ]

If they were at the track and have experience they would have known better than to just give a random AFR (12 is too rich) number. Dyno you tune for power, track you tune for ET and check plugs. Keeping the AFR in a safe level.

[jsawduste]

[quote="Biggrnjeep97"]What tire/axle combo do you have? And were you allowed to run "large" tires? Point being, id love to go get a chassis dyno done but im not certain theyd be thrilled with me running 40" egg shaped swampers! Ive followed your jeep on another forum and have been impressed with your work, Good job![quote="jsawduste"]

Thanks for the kind words. I very much respect your comments.

These pulls were made with a set of 37 inch MT/R`s and a highly modified 8.8.
One of the factors the dyno guys bought up was the driveshaft angle and the parasitic drag of running at a static 21*. This and the tire size raised a few questions. This why we got in touch with the Dyno Manufacture Tech Line. Gave them the specs and they gave us the 30-35% correction factor for "at the crank" numbers.

The 37`s are not going anywhere but I am changing over to a Currie RockJock........Supposed to be here Monday..........Which is a High Pinion axle based on Dana 60 components. This will help to flatten the DS out and hopefully reduce drag. Though it might be a trade off as the ring rear on the RJ is 9.5 vs the 8.8`s well...8.8..

One interesting note was that pulls 2-4 were hot lapped. Meaning I did not shut the engine down to cool off any The first pull was with a water temp of about 200 while the others were more in the area of 210. The jeep had been driven about 20 miles to get to the dyno and was quickly set up and run. So the first pull would have been at the lower end of operating temp but still considered a warmed up engine. In fact we ran the jeep on the rollers for a few minutes at 55 mph in 4th just prior to the last pull.

Also coming next week is an AutoMeter WB to replace the NB AFR with all the pretty lights. The WB and the MAP sensor adjuster will hopefully get my AFR`s in check at WOT. Looking to tune it to 12.5-.8 or so.

Very curious to see what the closed loop numbers are also and to see if the closed loop needs any tweaking via FP and perhaps injector size. Suspect it will be OK but the WB will tell all.

[amcinstaller]

nice jeep! good luck with the coming runs, and great work on the numbers so far. so you think that you could have gained anything at all with a little more head work?

[Cheromaniac]

Very curious to see what the closed loop numbers are also and to see if the closed loop needs any tweaking via FP and perhaps injector size. Suspect it will be OK but the WB will tell all.

As long as you have the WOT numbers dialed in (12.5-13.0) and your upstream O2 sensor is functioning normally, the closed loop AFR should remain at 14.7:1.

[Cheromaniac]

I also agree that your Jeep looks great.