Dyno runs

[BBeach]

Lucky me got to go with my school for a free (for members at least) dyno day. We got to test out the members vehicles ranging from motorcycles to a TJ. Anyways, I figured to post up my final sheet. This one is a little cluttered but I decided to show this one because it had my highest run on it. NOTE: The guy running the dyno had a little trouble gettin used to an automatic jeep so some of the runs will have much variation below 3000rpm or so. It seemed like as if on some of the runs he got on it after peak torque so some things are ommitted. Either way, cant be free and it was a lot of fun. The TJ there got 142rwhp or so. I didnt know this before myself, but when he increased his tire pressure from ~25psi to either 45-50 psi, his whp jumped a bit. And btw, does anyone know what the "ramp rate" is or what its measured in?

http://memimage.cardomain.net/member_images/1/web/793000-793999/793834_32_full.jpg

[BBeach]

I have another dyno sheet with 3 runs on it that isnt as cluttered up that i will post once i get back to school. Also, if i was to change my cam, is that what it would take to change where the peak torque occurs? BTW, mods are magnaflow custom 2 1/4" catback, self-bored 60mm tapered to 62mm throttle body, rustys intake, and clutch fan delete (ironically electric fan died right before the run so it was running hot for a little bit despite the dyno fans.

[Michaelarchangelo]

That seems a bit low. If you figure stock is 190, and you assume a 20% drivetrain loss, that puts you at 152 without any mods.

[tealcherokee]

at sea level at 60*

[BBeach]

That seems a bit low. If you figure stock is 190, and you assume a 20% drivetrain loss, that puts you at 152 without any mods.
Thats what I was thinking too but supposively they can change the ramp rates and all that to make it how they wish?? Either way the guys there said their dyno is a little bit tougher than other ones in the area. One of the guys with one of the new maximas with 265hp or w/e was getting repeated 178fwhp runs. I think if I put my tire pressure up it would have helped out because it helped out for my friend with the TJ suprisingly. Its hard to get an accurate number from those things but they were consistent. I would recommend them for any kind of tuning if its within the same day. Also, its supposed to be ran in the 3rd position once the torque converter locks up right?

[tealcherokee]

yes, 1:1 gear ratio, TC locked.

but thats not a bad number at all, you loose HP as altitude goes up due to the less dense air

[MudDawg]

Standard air= 29.95 inhg (sea level, standard barometer)/ 60*F / 50% RH. Barometric pressure, temperature, and water vapor measured in grains indicates the capability of the atmospheric conditions to support combustion...high barometer good, cold air good, water content bad

Air quality is commonly expressed as Ft. of equiv altitude. A cold dry day can be equivalent to BELOW sealevel conditions. Those most familiar with these concepts are ET class dragracers who depend in being able to predict ET based on current conditions. The air conditions change constantly.

In order for a dyno run to be meaningful and to be used for comparison run to run, the air conditions must be measured and factored in...

[BBeach]

yes, 1:1 gear ratio, TC locked.

but thats not a bad number at all, you loose HP as altitude goes up due to the less dense air Its only 246ft above sea level though.....and it had to be around 40-50 degrees out so it wasnt too hot either. Also, i believe that this individual dyno corrects for air temp and altitude. Either way, i did another 6rwhp better than a tj with a 5 speed after he increased the tire pressure.

[Michaelarchangelo]

What size tires are you running? Stock or larger?

[BBeach]

235/75R15, they were 225/75's before. I only had around 25-30 psi in each tire so im assuming if i pumped them up to 40 they would be less resistance from them. Im not sure of the magnitutde of that change but im pretty sure it woulda helped. Also, my fan died so I had to rely on the dyno fans to stop it from overheating....just my luck. The stock auxillary fan was running so it had to be around 220 degrees. Id say after a minute with the dyno fans running it was back down the regular temperature though so im not even sure if that was a factor. I think its all about the ramp rates or whatever.

[Dr. Dyno]

A chassis dyno 147.2rwhp at 4600rpm is right on the mark for a stock automatic TJ. Assuming a drivetrain loss of 20%, that would equate to 184hp at the flywheel.

[Michaelarchangelo]

Ya but he has a modded xj, which is why it sounded kinda weird too me.

[j99xj]

Maybe its dirty fuel injectors

[BBeach]

Maybe its dirty fuel injectors I highly doubt it, every oil change I use valvoline complete fuel system cleaner and that was maybe 700 miles ago. I put in some premium right before the run too so idk. It does seem a little low but it was still a good 6rwhp more than a 2000 tj with a 5 speed and with properly inflated tires. The dyno itself is known to be a little bit tougher which doesnt make sense to me, if i only knew what the ramp rates were it would help. They said they were running a ramp rate of 150 but im not sure of the units or significance of that.

[Dr. Dyno]

I've just noticed that the run was done on a Dyno Dynamics dynamometer. This dyno typically absorbs ~8% more power than a Dynojet so the drivetrain loss for a 2WD automatic is more like 28%. That would make the flywheel figure ~204hp.

[BBeach]

I've just noticed that the run was done on a Dyno Dynamics dynamometer. This dyno typically absorbs ~8% more power than a Dynojet so the drivetrain loss for a 2WD automatic is more like 28%. That would make the flywheel figure ~204hp. That would make a bit more sense, I just wish i pumped up the tires a little bit. Dyno would you imagine it making a big difference from going from 25psi to say 40psi on 235/75R15's? Also, does changing the cam change the peak torque of the engine? What would be a good cam that would be good for mid to higher rpms or does the stock one do that fine enough?

[j99xj]

I don't know if the tires would make a lot of difference but changing the cam would make a huge difference.

The performance of any engine is directly related to the cam. But if your going to change the cam you might as well do a rebuilt. And if your doing a rebuild you might as well do a stroker.

I've been thinking about ways to get more leverage. Either a longer stroke or lower gears. And I'm currently undecided about this.

[Dr. Dyno]

Dyno would you imagine it making a big difference from going from 25psi to say 40psi on 235/75R15's?

It WOULD make a little difference 'cause with the higher tire pressure there's less rolling resistance.

Also, does changing the cam change the peak torque of the engine?

Depends on the cam you select. Yes, it can change both the actual peak torque number AND the rpm at which peak torque occurs. The change in peak torque isn't huge but it's measureable on the dyno.

What would be a good cam that would be good for mid to higher rpms or does the stock one do that fine enough?

The stock '96+ cam is actually a pretty decent unit and produces very good torque from off idle to about 4500rpm. You can improve on it further simply by adding Yella Terra 1.7 ratio roller rockers to increase valve lift. OTOH, you could shift the torque peak to nearer 4000rpm by substituting a bigger cam e.g. Crane 753905 or CompCams 68-231-4 but as j99xj said, it's no easy exercise to just swap in a cam because it's inside the block. If you're going to take that route, I'd follow j99xj's advice to either rebuild the rest of the engine or build a stroker.
With all the cam failures that have been occurring in strokers (including mine at 34k miles), I suggest you keep the stock cam and do the roller rockers instead for the sake of reliability.

[lilredwagn]

With all the cam failures that have been occurring in strokers (including mine at 34k miles), I suggest you keep the stock cam and do the roller rockers instead for the sake of reliability.
Yikes! Is this problem being actively discussed anywhere?

[j99xj]

With all the cam failures that have been occurring in strokers (including mine at 34k miles), I suggest you keep the stock cam and do the roller rockers instead for the sake of reliability.

I read about your "cam clamity" on your stroker page. That sucks you had to tear the engine down again.

Just curious. Does the stock cam in your stroker feel any different compared to the crane (performance wise)?

Have you had any detonation issues with the stock cam? (You mentioned the stock cams only good to about 9.1:1)

[BBeach]

Now that im back to school I scanned the more clean dyno sheet, this one doesnt show the 147.2rwhp run but its much cleaner.
http://memimage.cardomain.net/member_images/1/web/793000-793999/793834_35_full.jpg

[Dr. Dyno]

At least it shows a maximum torque of ~185rwtq at 3700rpm or ~257lbft at the flywheel.

I read about your "cam clamity" on your stroker page. That sucks you had to tear the engine down again.
Just curious. Does the stock cam in your stroker feel any different compared to the crane (performance wise)?
Have you had any detonation issues with the stock cam? (You mentioned the stock cams only good to about 9.1:1)

I haven't done any timed acceleration runs yet but by the SOTP, it's hard to tell any difference between the stock cam and the Crane. One thing that's definitely noticeable is the smoother idle and the absent valvetrain noise. With the crane cam & Mopar valve springs, there was always a mild ticking sound at idle up to ~2000rpm.
I've had no detonation problems at all with the stock cam despite a 9.4:1 CR. I think the late intake valve opening and closing of the stock cam (and high intake centerline angle) help to keep down cylinder pressure despite the short 0.050" lift duration of 197 degrees. The high intake centerline angle makes it behave, in effect, like a bigger cam.