Dyno Results

[Frank Z]

Well folks I finally cleared the 1000 mile mark with my stroker and today was DYNO DAY!! WOOT!

Let me start by saying my expectations were a little bit high, but I'm still very pleased with the results.

Reason #1...nothing flew off the motor, none of the pistons left their appointed cylinders, the lifters lifted, and the pushrods....well they pushed rather nicely I guess.http://www.colorado4x4.org/vbb/images/smilies/shrug.gif

I fully expected monsterous torque and horsepower numbers based on what I read on the WWW. To clarify, don't believe everything you read. Horsepower and torque aren't that easy to come by and some folks will exagerate their "Real World" results.


So how did we do?
Peak torque at the reap wheels 178.1 @ 3600-3700 rpm.
Peak horsepower at the rear wheels 137.1 @ 4300 rpm.

Assuming 25% drive train loss the numbers for the motor are 222.6 Ft Lbs torque and 171.4 HP. The stock specs that found at JeepForum.com are 190 hp @ 4750 rpm, 220 ft lb @ 4,000 rpm and I don't believe those numbers to be correct. I'll do a little more search and see what I come up with. I think we can all agree that OEM numbers are inflated a wee bit.http://www.colorado4x4.org/vbb/images/smilies/co4x4/rolleyes.gif

Reason #2 This is a hoot. The guy ( Ben at DL 'Stangs) that was doing the testing on my rig told me that he has a buddy that has another dyno a few miles from the shop I was at. He relayed a story about a gentleman that brought in a rig with a
$12k motor that was built by another local shop (not my shop!!) and the dyno results were only about 10% better than mine!! A full $10k more motor and all that the guy got was 10% more? Ben saw the look on my face (which was one of disbelief) and he calls the other shop and and askes them point blank what the numbers were for the motor we had been talking about. They looked it up on their computer and confirmed what Ben had just told me. Wow, just plain wow. How can I feel too bad about the numbers my engine out after hearing that!?!


Bottom line, the numbers might not be up to the levels I had hoped for, but the real world experience of building my own motor and feeling the seat of the pants power increase is nothing short of amazing. I notice the difference, my wife notices the difference, and so do the kids. The look on the faces of the Ricers is just more gravy for my meat and potatos as well.http://www.colorado4x4.org/vbb/images/smilies/co4x4/thumbsup.gif

No scanner so I can't post the print outs. Ben will be emailing me a copy and I'll post them when he does.

[Flash]

would love to see the dyno spec.?????

Glad to see that it's broke in and and running strong!!!!



flash.

[Frank Z]

I'll post 'em as soon as I get them emailed to me.

[Michaelarchangelo]

Something doesn't seem right. Ive seen dyno graphs for stock 4.0s that had more torque than that.

[jeepinwi]

Frank-
Have you compensated for the elevation? Assuming 3% loss in power per 1000 feet, you can add about 15% to your dyno results. Your results are among the weakest I have seen for a stroker.:dunno:

[Frank Z]

I'll call and ask.

I'm going to try it again, but I want to try a different dyno and see what the results are.

[Pro Stock John]

248 Dynojet? They can correct for altitude and weather.

[Frank Z]

The dyno was Superflow AutoDyn 30.
After doing a little research here, I think the results maybe skewed. If I'm reading some of the Dyno threads correctly the dyno runs should be made in 3rd gear...?

Any input is welcome.

[Michaelarchangelo]

Which tranny do you have?

[Frank Z]

AW4

[BBeach]

Even I got more in my basically stock jeep...147.2rwhp and around 200lb-ft of torque and it was a dyno dynamics dynamometer. Im hoping to build a stroker one of these days so im hoping your results are off. :huh:

[Slo-Sho]

Something doesn't seem right.

I'll 2nd that statement. Then again he doesn't give any details about the motor or how they dyno'd the vehicle so who knows?

[Pro Stock John]

1) So that's probably a load-based dyno? If so, they will dyno lower than a Dynojet, so make sure you compare apples to apples.

2) You should always dyno in whatever gear is 1:1, so that would be 3rd gear.

3) Make sure you try to look at AF when dynoing too, they can stick the sensor in the tailpipe if they have one. Then you can make sure that you are not running out of fuel because you have a bum fuel pump or you are running out of (fuel) injector.

[BBeach]

We have no idea on the specs of your jeep, but do you have the stock injectors in there? Stock exhaust, intake? Maybe it was running lean. With the AW4, make sure its in the 3 position and let it lock then you slowly bring it up to maybe 65mph (depends on gearing/tires) and then floor it so it'll stay in that gear. Unless you want to mod it to hold that gear which would be ideal. How was your tire pressure, when we did a dyno on my friends jeep, his whp changed a little bit when we pumped up his tires.

[Frank Z]

The motor is a 4.6L.

The build up can be seen here. (http://www.colorado4x4.org/vbb/showthread.php?t=80410)

the AF was 13.8 at 3600 rpm and fell to 12.2 at 4800 rpm.

As I stated earlier, I don't have a scanner, so I'll have to wait until the shop emails a copy to me that I can post here.

Based on some of the other threads I've seen with close to the same results, it does appear that the results are skewed because of the transmission not being in the correct (3rd) gear. I'll get it back on a dyno as soon as I can, but that won't be till next week some time.

[Slo-Sho]

13:1 is about ideal for an N/A motor throughout the RPM range. The AW4 while electronically controlled can still be operated w/o the TCU connected to it's main harness. It is possible to physically leave the shifter in the '3' slot and apply power to the TC lock up solenoid so you can get a rolling off idle WOT stomp w/ a true 1:1 engine/trans ratio. Also those 33's will change the final drive ratio, so the power figures you're shooting for are most likely for a rig with stock gearing/tire size.

[Frank Z]

So the $.69 question then becomes... What's the proper way to perform the dyno pulls with a 97 XJ running an AW4 tranny?

Do I simply put the tranny in 3rd and go from there?
Do I need to unplug the TCU?
If the TC solenoid needs to be engaged, whats the best way to do it?

[NoCoastFocus]

Can you post the dyno graph Frank? I am willing to bet it wasn't sae corrected.

[Frank Z]

No, not yet.

Yes the results are SAE corrected.

Definetly a gear selection issue. I'll be working on a TC lock after I get more time to read up on the subject and scrounge some parts.

[j99xj]

I've lived in Colorado Springs my whole life (I'm only in Fort Collins (CSU) for college) and as other's have said you MUST take the altitude into account.

Colorado Springs is at least 6000' in the downtown area, so that's an 18% loss right there.

If you did the dyno test on the north east side of the city (500-750' higher) your loss could be as much as 20 %.

Don't feel too bad, EVERYBODY takes the same horsepower hit here in Colorado, unless you one of the lucky few that have turbocharger or supercharger.

I'm scared to take my little 4.0 with only bolt ons to the dyno if a stroker can only make what yours did!

[Frank Z]

Yes the results are SAE corrected.

Definetly a gear selection issue. I'll be working on a TC lock after I get more time to read up on the subject and scrounge some parts.

[Pro Stock John]

Dyno's can correct for altitude. What gear did you dyno in?

33's will hurt numbers, the bigger and heavier the rolling the more it hurts the numbers. But we might be talking 5-10rwhp.

I dyno my turbo Formula (867rwhp) on 28W slicks since it would just spin on the dyno with factory 26" radials.

But a factory 28" radial would dyno a bit better. I think 13:1 is okay, but no leaner on a load dyno.

[Frank Z]

Drive.

[Pro Stock John]

Would that be 4th? That would be overdrive and like .75:1 or something, so the numbers would be lower if the Jeep was actually in 4th gear in the pull.

[Frank Z]

Yes, that's what I've been saying....

[BBeach]

I dont know, performing a dyno in 4th gear locked with 33's all the way till redline....say if you had stock 3.55 gearing you'd be doing somewhere in the ball park of 180mph. I would imagine they woulda blown up? :fuse:

[Frank Z]

Yes I'm on 33's, yes the axles are locked, no I don't have stock gears.... 4.56's

[BBeach]

Yes I'm on 33's, yes the axles are locked, no I don't have stock gears.... 4.56'sIts still gonna be 144mph, what kinda tires are they? And as far as locked I meant the torque converter. Im gonna take an educated guess that when its locked there's more parasitic loss than when there's an open diff, someone correct me if im wrong.

[Frank Z]

Where are you getting your numbers from? 144mph?

The tires are Cooper Discover STT's.

[BBeach]

Where are you getting your numbers from? 144mph?

The tires are Cooper Discover STT's. There's plenty of calculators out there but I just took 5000rpm / (.75 4.56) * 60 * 33pi / (12*5280) . Idk how hard that is to read but I just took plugged and chugged in my calculator. If it was till 5250 rpm just multiply by 1.05. The only reason I ask about the tire is the speed rating, though you can go over them, and in the case of a dyno its short term.

[Frank Z]

I just plugged some numbers (5000rpm, 33" tires, 4.56 gears) into my free version of Virtual Engine Calculator and came up with 107.69mph.

[Flash]

Its still gonna be 144mph, what kinda tires are they? And as far as locked I meant the torque converter. Im gonna take an educated guess that when its locked there's more parasitic loss than when there's an open diff, someone correct me if im wrong.


Tires that blow apart due to speeding faster the there rating, don't come apart because you past the magical number. they come apart because of the extra heat that is generated at that speed.......yes centrifugal force is grate, and would tear then apart if it was keep at that kind of speed.

the real Question is wheel speed and they would be the same at 5000 RPM weather you had 215/75/15(stock 27") or 35" mudder.


Flash.

[tealcherokee]

flash i have no clue what your trying to say in that last sentance, if your saying wheel speed will be the same at 5000rpm with a 27" and a 35" tire youre wrong.

WS(wheel speed)=rpm / transmission gear / transfercase gear / diff gear

so WS=5000/1/1/4.56
WS=1096rpm
now the circumference of a 27" tire is ~84"
the circumference of a 33" tire is ~104"

with a 27" tire the jeep is traveling at 92064 ipm (inches per minute)
on 33's its traveling at 113984 ipm

92064" 60 min foot mile
------ ------ ------ ------ = 87mph
min hour 12" 5280'

113984" 60 min foot mile
------- ------- ------- ------- = 108mph
min hour 12" 5280'

[BBeach]

flash i have no clue what your trying to say in that last sentance, if your saying wheel speed will be the same at 5000rpm with a 27" and a 35" tire youre wrong.

WS(wheel speed)=rpm / transmission gear / transfercase gear / diff gear

so WS=5000/1/1/4.56
WS=1096rpm
now the circumference of a 27" tire is ~84"
the circumference of a 33" tire is ~104"

with a 27" tire the jeep is traveling at 92064 ipm (inches per minute)
on 33's its traveling at 113984 ipm

92064" 60 min foot mile
------ ------ ------ ------ = 87mph
min hour 12" 5280'

113984" 60 min foot mile
------- ------- ------- ------- = 108mph
min hour 12" 5280'And you're neglecting the fact he said he left it in drive which is a transmission ratio of .75:1 not 1:1....108 mph x 1/.75 = 144...The problem all you guys are having is you're prolly calculating with respect to 1:1 ratio, which dyno's should be in, but he said he was in 4th.

Flash, the wheel speed will be different given the same gearing, in this case 4.56 . A 10" tall tire is going to spin MUCH faster than a 40" tire (if it makes it easier to imagine).
Yes the tire"explode" speed isnt a magical number, but I'd guess he woulda spent a couple seconds up there, which isn't much. But sometimes that's all it takes. Mudders plus lots of centrifugal G's dont mix well together.

[Pro Stock John]

Okay well...

1) I don't know the gear ratio of overdrive, .75 was just my guesstimation.

2) Dynoing with bigger gears will lower rhwp. So will bigger tires.

3) Having a vehicle see a lot of mph on a dyno won't blow up the tires since a dyno pull only last 10-20 seconds depending on how long and how you load the converter and trans.

[Flash]

Sorry didn't quit word it right.

The point that i was trying to make is the the tire rpm(axle speed ) would be the same weather it was a 27" or a 35".......But yes your right, tire rolling dist and mph would be way different between 27 and 35 inch tire.;)

Flash.


flash i have no clue what your trying to say in that last sentance, if your saying wheel speed will be the same at 5000rpm with a 27" and a 35" tire youre wrong.

WS(wheel speed)=rpm / transmission gear / transfercase gear / diff gear

so WS=5000/1/1/4.56
WS=1096rpm
now the circumference of a 27" tire is ~84"
the circumference of a 33" tire is ~104"

with a 27" tire the jeep is traveling at 92064 ipm (inches per minute)
on 33's its traveling at 113984 ipm

92064" 60 min foot mile
------ ------ ------ ------ = 87mph
min hour 12" 5280'

113984" 60 min foot mile
------- ------- ------- ------- = 108mph
min hour 12" 5280'

[Pro Stock John]

35's have a lot more rolling resistance than 27's.

[Dr. Dyno]

I dyno'd my stroker last month and got 210hp@4900rpm and 250lbft@3750rpm at the rear wheels. I have stock size 27.4" tires and the dyno run was done in 3rd gear (I have the AX15 5-speed).
If you have an automatic, you'll get the highest dyno numbers if you do the run in 2nd gear. If you do it in 3rd, you'll get about 15hp less. Bigger tires add rolling resistance and will further lower the dyno numbers.

[jeepinwi]

You guys are missing a very important fact here. THE SPEED LIMITER ON AN XJ KICKS IN AT 116 MPH. With 33's and 4.56's, it would be impossible for Frank to run his stroker up to 5k rpm's in overdrive. The speed limiter would kick in. Since he had it in drive, his run was done in 3rd gear, which is 1:1.

If we could assume 18% loss in power for elevation, Frank's sea level numbers would be 262 Ft Lbs and 202 HP.

IMO, still weak for a stroker.

[BBeach]

You guys are missing a very important fact here. THE SPEED LIMITER ON AN XJ KICKS IN AT 116 MPH. With 33's and 4.56's, it would be impossible for Frank to run his stroker up to 5k rpm's in overdrive. The speed limiter would kick in. Since he had it in drive, his run was done in 3rd gear, which is 1:1.

If we could assume 18% loss in power for elevation, Frank's sea level numbers would be 262 Ft Lbs and 202 HP.

IMO, still weak for a stroker.Isn't it based more upon RPM? The computer figures out the speed by the output of the tranny right? So basically the speed limiter is based on the rpm at which stock tires will hit 116mph, which isnt the same as when 33's will hit that rpm. My jeep hits the limiter at 112-118 (for example) at maybe 3500rpm in OD locked (i believe) at WOT though unlocked sounds correct. (then again maybe max acceleration at those high speeds is locked because the losses with it unlocked are overwhelmed by the other forces on the jeep (mainly drag). Anyways, it hits it at a given rpm in top gear, so like you're saying in 4th gear I'm assuming its going to stop at a pre-programmed 3500-3600 or something. He's still going to be doing an actual 140mph, but none-the-less, he's wouldnt be gettin a full dyno graph which is contrary to what he got. Maybe he just left it in Drive but floored it enough to let it kickdown to 3rd, then go from there. Im not 100% on how the top speed things works so ill look around to see what I can find :read: , but Im assuming output speed at the sensor (tranny output i beleive) and not what the tires are actually doing (140 or so in this case). Anyone? :dunno:

[Flash]

I thing once Frank Z get the Dyno sheet up it may tell us a lot more of why the Dyno pull was incorrect.

To speculate some more,.........if he started to lean out at top end would explain a lot. If he actually hit is rev limiter or speed limiter.:eeks1:

Flash.


Isn't it based more upon RPM? The computer figures out the speed by the output of the tranny right? So basically the speed limiter is based on the rpm at which stock tires will hit 116mph, which isnt the same as when 33's will hit that rpm. My jeep hits the limiter at 112-118 (for example) at maybe 3500rpm in OD locked (i believe) at WOT though unlocked sounds correct. (then again maybe max acceleration at those high speeds is locked because the losses with it unlocked are overwhelmed by the other forces on the jeep (mainly drag). Anyways, it hits it at a given rpm in top gear, so like you're saying in 4th gear I'm assuming its going to stop at a pre-programmed 3500-3600 or something. He's still going to be doing an actual 140mph, but none-the-less, he's wouldnt be gettin a full dyno graph which is contrary to what he got. Maybe he just left it in Drive but floored it enough to let it kickdown to 3rd, then go from there. Im not 100% on how the top speed things works so ill look around to see what I can find :read: , but Im assuming output speed at the sensor (tranny output i beleive) and not what the tires are actually doing (140 or so in this case). Anyone? :dunno: