4.2 mini stroker dyno results

[ohho92]

I have a 92 XJ with a fresh 4.2 mini stroker that I had dynoed a few days ago. The results at first were not what I expected. Driving it felt like it had more to offer. So I want to see what you guys think and any suggestions.
I'll start with the build list:
91 HO block bored over.060, deck milled.008
Silvolite 2229 pistons dished to 18cc's
Mopar p4529229 cam
62mm throttle body
Ford 5.0 24# injectors
Stock rebuilt head milled .010
.051 head gasket
2.25 down pipe, 2.5 cat back
APN header

Stock 4.0 rwhp/ft lbs at 0' elevation (29.9"Hg) 70* temp Chrysler used 29% drivetrain loss w/ AW4
134.9/159.8 (a few less at 58*)

Dyno #'s at 5500' elevation (25.25"Hg) 58* temp
rwhp/ft lbs. 118.3@ 4250 rpm/168.7@ 3150 rpm
Crank= 167/238

Corrected 1.17 dyno #'s at 0 elevation. 29.9" Hg at 58* temp
Rwhp/ft lbs. 137/196
Crank= 195/277

So my final gain at 0' elevation was +5 rwhp and +52 rw ft/lbs over stock, 195hp/277 ft/lbs
The corrected dyno numbers were provided by dynojet. I spilled coffee all over the dyno sheet otherwise I would have posted it.
Overall the best comparison I can make to explain the difference is now the acceleration with 35's feels like the old engine with 33's and 4.88's. It has a snappy response at take off and accelerates better from 1000-4800 rpms.

[ohho92]

I forgot to add the CR is 9.5:1 running on 87 octane fuel. The dyno guy also mentioned that the AF ratio looked great up to 4500 rpm where it started running a little rich. If I can see the AF ratio on the dyno sheet I'll post it.
All in all I'm very pleased with the feel of the new motor.

[ohho92]

Correcting my mistakes, I should preview before submitting!
Gains- 5hp and 52 ft/lbs over the stock 190hp and 225ft/lbs at the crank.
Not porting the head might affect the hp some on the top end. At the time of the build my machinist recomended not porting it. He said it wasn't worth the effort on an inline 6 with my build.

[Cheromaniac]

Corrected 1.17 dyno #'s at 0 elevation. 29.9" Hg at 58* temp
Rwhp/ft lbs. 137/196
Crank= 193/276 (rwhp & rwtq /0.71)

So my final gain at 0' elevation was +3 hp and +51 ft/lbs over stock, 193hp/276 ft/lbs

That's a very nice torque gain over stock considering you've only added 5.7% more displacement. You can put that down to the higher compression, and the Mopar p4529229 cam adding more torque at lower rpm. If you'd ported the head you could have gained ~15hp at the top end.

[ohho92]

I thought so too considering it's turning 35" maxxis trepadors which are heavy tires. The torque came up nicely at 1600 rpm and steadily climbed. It was a crazy sight/sound to here it hit 100 mph at 5000 rpm in 3rd gear. Thanks cheromaniac for all the literature online. It gives us all a great starting point instead of taking a shot in the dark. I already have plans and some parts to rebuild the original 4.0 that came out of my cherokee to a short rod 4.6 or 4.7. I'll enjoy this one for a couple of years for now.

[Cheromaniac]

I already have plans and some parts to rebuild the original 4.0 that came out of my cherokee to a short rod 4.6 or 4.7.

Make it a long rod (4.0L) stroker with Bulltear custom pistons.
Can you post your 4.2 mini-stroker dyno sheet?

[ohho92]

I spilled coffee all over it that's why I didn't post it originally. What specific info did you want to see? I can see if some of the specifics are legible.
I'm thinking about going to another shop that has a mustang Dyno and see how it differs from the dynojet.

[ohho92]

Here's what I can make out:

RunFile_002.drf- 1/17/2015 9:08am
Run type; RO
Run conditions: 57.86*F, 855.22 mBars, humidity 10%
SAE: 1.17
Max power = 118.3
Max torque = 168.7
CF: SAE smoothing:5

The rest was the hp/tq chart. You can visit their web page http://www.denverhorsepower.com and see if you come up with any additional info.

Not much detail on the sheet compared to others I've seen. Wasn't that impressed with the service, that's another reason why I might go to the mustang dyno in a couple of weeks. Thanks

[Cheromaniac]

Just wanted to know at what rpm you were getting maximum HP and maximum TQ.
Was it something like 4200rpm and 3000rpm respectively?

[jeepxj3]

I wish you did a before and after dyno runs instead of just the after and calculated/corrected numbers.

Impressive how much TQ is added with just 5.7% more displacement, higher CR, smaller (0.010") quench, 62mm TB, headers and mild 29 cam.

[ohho92]

Yes, max hp at 4250 rpm and max tq at 3150 rpm. I did use the 232 crank, I forgot to list that on my parts list. I will get another dyno run in a couple of weeks just to compare the difference and I will get it laminated before I get home.

[ohho92]

A quick update. The engine now has 2300 miles and running good. Took a trip to Moab for the Easter jeep safari event. 6 hr trip over a couple of 10,000' passes and the increased torque is very much appreciated. No more 2nd gear to the floor and only 55mph up 6% grades. Played around a few trails with plenty of power to spin the 35's. Averaged 14mpg overall with 16 mpg on the highway at 65-70mph. At 70+ it dropped to around 13. It will hold overdrive on most hills and pickup speed in third nicely.
I also contacted the dyno shop and had a discussion over the power numbers. The figures came out as follows. 18% altitude loss and 30% drivetrain loss info I found throughout my search.

Rear wheel
At sea level 145hp/242tq
At 5500' 118hp/169tq

Crank
At sea level 205hp/295tq
At 5500' 168hp/242tq

I rounded up the numbers so they might be off a little, give or take. Overall I'm pleased and on track to build the original engine to a 4.7 stroker, just might take some time.

[Cheromaniac]

I have you at a dyno corrected 146rwhp/208rwtq.
Assuming a 29% drivetrain loss that's 205hp/293lbft at the crank. A decent slug of torque from 4.2L.
Most importantly you're happy with the results and that makes it worth the effort.
With a suspension lift and 35" tires, don't expect much gas mileage but it should still be an improvement over a stock 4.0.

[ohho92]

You are correct on the rear wheel torque. After looking at my math I noticed the mistake. Thanks