It can't be this slow with the mods I've done, but it is.

[j99xj]

Hey everybody. Tonight I got bored and I went out for a drive with my digital camera and recorded my gauge cluster while accelerating at maximum rate in my Jeep (wide open).

When I got home I used the video and a stopwatch to calculate some acceleration times. I repeated the timing multiple times and averaged the values I got and rounded to the nearest tenth.

This is what I calculated:
0-10 mph 2.0 s
0-20 mph 3.0 s
0-30 mph 4.3 s
0-40 mph 5.8 s
0-50 mph 8.3 s
0-60 mph 11.2 s
0-70 mph 14.2 s

Here are my major mods:

These ones should make me faster:
-flat K&N filter
-made the air box hole bigger
-removed the little restrictor in the air tube
-60 mm bored out throttle body
-62 mm smooth bore tb spacer
-pacesetter header with 2.25" downpipe
-2.5" high flow cat
-2.25" dynomax cat back
-intake manifold heatsheild



These ones make me slower:
-2 inch lift kit
-9000 lb mile marker winch (this sucker is heavy)
-jcr winch bumper (this sucker is really heavy)
-29" tall all terrain tires
-I'm at 5000 feet of elevation


Even when the items in my "slow" list effectively "cancel out" some of what I gained in my "fast list" why is my Jeep so dog gone slow??? 11.2 seconds to 60 mph? Come on! :rattle:

[Monkey55]

You have a lot of etra weight on that puppy..

The only true way of finding out if your mods actually made a difference is to test before and after each mod or test before, then after all the mods. Along with fuel, the temp and wind could even change the results.

Your "fast" list does not nessceraly cancel out your "fast" list. I have done more than half of the mods you have done and notice a quicker response and a LITTLE bit more power. Just because you have more power, does not mean that you gain speed. You may actually lose lose speed in lieu of tow end torch..

Also, there are soo many other factors like: tire pressure, sludge in the engine, worn plugs and wires, gas quality, weight of gas in the tank(to get picky), carb vs. efi, auto vs manual, and drag any other place..

So, there's not really one answer.


So, the two things I can suggest is too take off all the wieight and put the same exact amount of gas you had when doing the first test, then test in the same conditions. Compare the results. Then, do a major tune up on your rig and test with the same conditions, then compare the results to the other 2 tests. Then put everything back on and test with the same conditions..

You may find where the lag come from..

BTW - My Jeep ALWAYS runs better and drives faster after I wash it.. :laugh3:

Elias

[Beej]

Have you changed your gearing and speedo gear to accommodate the larger tires? If not, your speedometer is no longer accurate enough to make the right calculations...

[little red cheroke]

BTW - My Jeep ALWAYS runs better and drives faster after I wash it.. :laugh3:

Elias


x2

[j99xj]

Have you changed your gearing and speedo gear to accommodate the larger tires? If not, your speedometer is no longer accurate enough to make the right calculations...

I haven't changed my gears, I still have the stock 3.55 ratio. But I have changed the little speedo gear that goes into the transfer case to compensate for slightly larger tires. So I'm fairly confident in my speed numbers.

[Beej]

I haven't changed my gears, I still have the stock 3.55 ratio. But I have changed the little speedo gear that goes into the transfer case to compensate for slightly larger tires. So I'm fairly confident in my speed numbers. Okay.

So consider this...

If you did it last night, let's say the temperature was around 40 F, pressure was about 30Hg last night, dew point was 12 F, and your altitude is 5000ft. You should have gotten at best only 86.6% of your max horsepower last night. (see this link for the calculator) (http://wahiduddin.net/calc/calc_hp_dp.htm)

You started at 190ish as a stocker, you probably have gained 15 to 20 horses with your mods. And that's at best. That still only puts you at 210hp at best. 210hp x .866 = 181.86hp.

Then add on the extra 350lbs of weight, increased rolling resistance from larger tires and increased wind resistance from your lift, I'd say your numbers are pretty close...

[XJING]

Its a box, a heavy box. I have more mods than you but look at mods as how much more torque is it gonna give me, wanna go quick, get a vette, even strokers aren't all that quick, just put the torque curve where it can be used the best.

[j99xj]

Okay.

So consider this...

If you did it last night, let's say the temperature was around 40 F, pressure was about 30Hg last night, dew point was 12 F, and your altitude is 5000ft. You should have gotten at best only 86.6% of your max horsepower last night. (see this link for the calculator) (http://wahiduddin.net/calc/calc_hp_dp.htm)

You started at 190ish as a stocker, you probably have gained 15 to 20 horses with your mods. And that's at best. That still only puts you at 210hp at best. 210hp x .866 = 181.86hp.

Then add on the extra 350lbs of weight, increased rolling resistance from larger tires and increased wind resistance from your lift, I'd say your numbers are pretty close...


My best guess for the weight is about 3850-3900 lbs. This leaves some leway for the amount of gas in my tank. But I don't think I added 350 lbs.

This is how I figure it.
The Jeep itself weighs about 3500. (I have a "Classic" model with all the trimmings except leather seats)
I weight 185.
The winch is 80.
The bumper is about 100.
The total is 3865.

According to the formula from one of Dr. Dyno's pages, hp=(weight x 0.413) / t, where t is the time to 60 mph. So plugging in my time of 11.2 seconds and weight of 3900 lbs, that yields about 144 horsepower.

144 hp < 182 hp

So either 38 horsepower was flushed down the john somehow, or my Jeep is a lot heavier than I think.


The only way I will know for sure is from a dyno test. As they say the dyno doesn't lie. So I think I'll make a few calls and maybe get an appointment. I'm tired of guessing how much power I'm really dealing with.

[j99xj]

Its a box, a heavy box. I have more mods than you but look at mods as how much more torque is it gonna give me, wanna go quick, get a vette, even strokers aren't all that quick, just put the torque curve where it can be used the best.

Believe me, I'm not making a race car. I've driven true sports cars before and know that most Jeeps don't have a chance against them.

[tysonxj]

Are you assuming 0% drivetrain loss? (that would be a neat trick)

Why do you need to know how much power you have, is it worth $50-100 to dyno it?

[Beej]

First off, I don't think it weighs that much. I run 31's with full skids and crap and I've actually weighed my XJ. Minus my weight and with half a tank of gas my actual weight was 3550lbs. I have an SE with no options, so you could maybe add a few.

And I also think that the calculation you are using calculates wheel horsepower not crank horsepower. If you are getting about 144, that's about right...

[j99xj]

If you are getting about 144, that's about right...

I think your absolutely right. That would make a hell of a lot more sense.

144/182 = 0.79 So that's a 21% drivetrain loss which I think is perfectly normal.

[Beej]

144/182 = 0.79 So that's a 21% drivetrain loss which I think is perfectly normal. Sure, but doesn't it make you want a stroker even more?

:D

[Dr. Dyno]

So either 38 horsepower was flushed down the john somehow, or my Jeep is a lot heavier than I think.

You haven't considered a third possibility; that your recorded times might be pessimistic especially since the launch was very slow. Did you powerbrake at all?
The other thing to consider is that at 5000ft, your Jeep is going to be at least 15% slower than at sea level and possibly more if the barometer reading was low and humidity was high.

The only way I will know for sure is from a dyno test. As they say the dyno doesn't lie.

The dyno most definitely CAN lie especially if the dyno operator "doctors" the correction factor when making the final HP/TQ calculations. The only dyno that never lies is the "dino dyno" cause I use the same STP correction (29.92"Hg, 60*F, dry air) all the time. ;)

[Dr. Dyno]

wanna go quick, get a vette, even strokers aren't all that quick

It depends on what you consider to be "not all that quick". My strokered XJ does the 1/4 mile in 14.2 (170lb extra weight reduction) or 14.4 (full street weight). Some might consider that to be very quick, others (who are used to driving cars that run 13's or better) might consider that to be slow.
I could easily get a bunch of speeding tickets even if I drive it with only moderate enthusiasm so I'd say it's more than quick enough for me.

[j99xj]

Did you powerbrake at all?


No.

What's the right way to do it?

[XJING]

It depends on what you consider to be "not all that quick". My strokered XJ does the 1/4 mile in 14.2 (170lb extra weight reduction) or 14.4 (full street weight). Some might consider that to be very quick, others (who are used to driving cars that run 13's or better) might consider that to be slow.
I could easily get a bunch of speeding tickets even if I drive it with only moderate enthusiasm so I'd say it's more than quick enough for me.

Unfortunatley, in todays world of reletivly mundane vehicles comming from the factory turning 14's yep, its just not that quick, I had a 60 falcon in high school in the early 1980's did 12.20's and that was concidered very quick for a street car. In the 80's. (but thats 25 yrs. ago and apples vs. oranges)

I appluade you Dino, Its a great feat to get 14's out of a vehicle that was never meant to do more than take the "average" guy to his favorite fishing spot. I am going to build a stroker for my beast this winter. Its the best most economical way to rebuild, but I'm likeing the torque aspect of what it will give me more than making it quick,
And Dino, you can get speeding tickets in anything with some "enthusiastic driving" LOL

[Dr. Dyno]

No.

What's the right way to do it?

Left foot on the brake, right foot on the accelerator, tranny shifter in 1st, rev up to ~2000rpm, then release brake and floor go pedal simultaneously. Shift manually at ~5000rpm in each gear and hope for the best.

[j99xj]

Left foot on the brake, right foot on the accelerator, tranny shifter in 1st, rev up to ~2000rpm, then release brake and floor go pedal simultaneously. Shift manually at ~5000rpm in each gear and hope for the best.


Ok I did that. Only thing thats different is that my tranny shifts from 1-2 no matter what gear selection I'm in at about 4700-4800 rpm. Also I lay rubber on the road at any rpm above 1900.

These are my new times: They are quicker below 30 but slower above 30.
0-10 1.8 s
0-20 2.8 s
0-30 4.2 s
0-40 6.1 s
0-50 8.4 s
0-60 11.6 s
0-70 15 s

Another weird thing that happens only when I'm in the 1-2 gear selection at WOT is that after the shift from 1 to 2 the engine speed is about 3250, then it bogs down to about 3000 rpm. Maybe its the torque converter locking up, I'm not sure.


But I can't really make a direct comparison from tonight's run to the other run I made a few days ago. The atmospheric conditions are almost certainly to be different.

I'm just going to get a dyno test done. It would be nice to see an air/fuel ratio graph as well to see if my fuel curve needs a little more enrichment, (I made a map adjuster but I haven't installed it yet).

[Dr. Dyno]

Another weird thing that happens only when I'm in the 1-2 gear selection at WOT is that after the shift from 1 to 2 the engine speed is about 3250, then it bogs down to about 3000 rpm. Maybe its the torque converter locking up, I'm not sure.

Yes, that's exactly the reason why the revs drop. You might be able to adjust the tranny cable to the TB enough to make the tranny shift at 5000-5100rpm but it won't make a significant difference to the times.


Unfortunatley, in todays world of reletivly mundane vehicles coming from the factory turning 14's yep, its just not that quick

Unfortunately you're right. :( Take a look at this list of hot hatchbacks:

http://www.angelfire.com/my/fan/Hot-Hatch.htm

Before I built the stroker, any one of them would have beaten me. Now I can stay ahead of nearly all of them but it's only a matter of time before the bar is raised again and you find hot hatches running 13's. That'll be the time when I'll think about super/turbocharging my stroker.

[SCW]

Before I built the stroker, any one of them would have beaten me. Now I can stay ahead of nearly all of them but it's only a matter of time before the bar is raised again and you find hot hatches running 13's. That'll be the time when I'll think about super/turbocharging my stroker.


Doc, you're a doc! Just go get a Porche on your gold card and call it good! :D

[BBeach]

Ok I did that. Only thing thats different is that my tranny shifts from 1-2 no matter what gear selection I'm in at about 4700-4800 rpm. Also I lay rubber on the road at any rpm above 1900.

These are my new times: They are quicker below 30 but slower above 30.
0-10 1.8 s
0-20 2.8 s
0-30 4.2 s
0-40 6.1 s
0-50 8.4 s
0-60 11.6 s
0-70 15 s

Another weird thing that happens only when I'm in the 1-2 gear selection at WOT is that after the shift from 1 to 2 the engine speed is about 3250, then it bogs down to about 3000 rpm. Maybe its the torque converter locking up, I'm not sure.


But I can't really make a direct comparison from tonight's run to the other run I made a few days ago. The atmospheric conditions are almost certainly to be different.

I'm just going to get a dyno test done. It would be nice to see an air/fuel ratio graph as well to see if my fuel curve needs a little more enrichment, (I made a map adjuster but I haven't installed it yet).
Yeah thatd be the torque converter locking up. In the top of second gear, at say 4700rpm, you could put it back into the 1-2 position and it'll hold second gear till 5300 or whatever you want. Its just a little bit more of a boost to your times, but i wouldnt push it past 5200rpm. Just stroke the thing.

[j99xj]

Yeah thatd be the torque converter locking up. In the top of second gear, at say 4700rpm, you could put it back into the 1-2 position and it'll hold second gear till 5300 or whatever you want. Its just a little bit more of a boost to your times, but i wouldnt push it past 5200rpm. Just stroke the thing.

My tranny shifts at 4700 rpms or so from 1st to 2nd no matter what. I still need to check the cable slack like Dr. Dyno said. I think getting an extra 500-600 rpms out of the engine should improve my 0-60 time by a few tenths. My engine is still pulling strong at that rpm.

[BBeach]

Yeah i dont think theres too much to do other then tighten it for the 1-2 shift, but i was talking about the 2-3 shift. Hold it in the 1-2 "position" once it hits 4600rpm or so, just late enough so the torque converter wont lock up enough to make a difference, then shift into D once its at 5200rpm in 2gear. You dont want to shift into the 3 position because you'll get the torque converter to lock up again.

[MudDawg]

My lil ole 2.5 with a 3 speed auto goes 0-60 in 13.2 with 33's. But I shift it at 6,500....LOL

[jeepinwi]

http://media.putfile.com/XJ-acceleration-001
http://media.putfile.com/jeep-acceleration
The first video is my XJ accelerating today. Keep in mind that I could not get a great launch trying to hold the camera, steering wheel, and shifter. I put a stop watch to the times and here's roughly what I got:
0-30 3.15 sec
0-40 4.4 sec
0-50 6.15 sec
0-60 8.75 sec
0-70 11.6 sec
My XJ is an SE model, 2 door, 5 speed, has 225/70/15 tires, 115k miles, and a homemade cold air intake. I really did not want to let off at the top of 3rd gear, but I was on a 40 mph road!:nono:

The second video is my old YJ accelerating. It had 6 cyl/5 speed, 30" tires, ported head, 150k tired miles. Stopwatch gave me:
0-30 3 sec
0-40 5.4 sec
0-50 7.8 sec
0-60 11.7 sec

[j99xj]

http://media.putfile.com/XJ-acceleration-001
http://media.putfile.com/jeep-acceleration
The first video is my XJ accelerating today. Keep in mind that I could not get a great launch trying to hold the camera, steering wheel, and shifter. I put a stop watch to the times and here's roughly what I got:
0-30 3.15 sec
0-40 4.4 sec
0-50 6.15 sec
0-60 8.75 sec
0-70 11.6 sec
My XJ is an SE model, 2 door, 5 speed, has 225/70/15 tires, 115k miles, and a homemade cold air intake. I really did not want to let off at the top of 3rd gear, but I was on a 40 mph road!:nono:

The second video is my old YJ accelerating. It had 6 cyl/5 speed, 30" tires, ported head, 150k tired miles. Stopwatch gave me:
0-30 3 sec
0-40 5.4 sec
0-50 7.8 sec
0-60 11.7 sec

Holy crap your xj revs up quick.

I'll see if I can post the two videos I used to calculate my two timesets. I'm not making any promises though.

[j99xj]

Ok I got the two videos uploaded.
http://media.putfile.com/1999-Jeep-XJ-accel
http://media.putfile.com/1999-Jeep-XJ-burnoutaccel

The difference between my videos and jeepinwi's videos are a night and day difference, even when our 0-60 times are only about 2.5 seconds apart.

You'd think my cargo area was full of bricks and cement bags with the kind of acceleration I have.

But my XJ is much faster than stock. If I had to guess what my stock 0-60 was, it was probably 13-14 seconds. So getting it down to 11.2 isn't that bad at all.

Oh yea, the videos might take a few minutes to view, if you have dial up you might as well go watch some tv before viewing them.

[Michaelarchangelo]

What about changing out the valve body on the tranny?

[FatXJ]

I know this may sound a little wierd but I was having the same problem as you, my 99 XJ (2.25" downpipe, 2.5" Flowmaster catback,MSD coil and wires, Accel Cap & rotor, K&N, Bored TB) is slower than it should be. I have been getting pretty bad gas mileage as well so I finally found the problem, it was the fan clutch. I replaced it with the perfectly good working clutch off my 87 XJ and it made a huge difference in acceleration.

My clutch went bad by freezing up and being always on. I'm sure it was sucking a good amount of HP from the motor.

[Michaelarchangelo]

Ditch the clutch fan altogether, and you will notice how much faster the xj will rev.

[aroncull]

Here are my major mods:

These ones should make me faster:
-flat K&N filter
-made the air box hole bigger
-removed the little restrictor in the air tube
-60 mm bored out throttle body
-62 mm smooth bore tb spacer
-pacesetter header with 2.25" downpipe
-2.5" high flow cat
-2.25" dynomax cat back
-intake manifold heatsheild

I also live in CO North of Denver..
I have some similar "mods"
my curb weight is 4500# !!
"Go by a landscaping place near you that has a weigher and you can get an exact measurement... i have a Pioneer right up the street from me.."

So yeah she's heavy
4" of lift, Rockers, front Warn bumper with brushgaurd, rear BPI with spare and high lift, 33's, tomken gas tank skid, roof rack uh.. yeah so shes heavy..
engine stuff:

Drop in K&N filter
AirFlow Snorkel
[Done the GoJeep way with plexiglass in the Airbox to help push the air up into the whole filter.. ofcourse the old inlet is closed off as a well. ]
Accel Cap, Rotor, 8MM super stock wires and new Bosch PLatt set to stock gappage.
5-90's Mega battery cable set that replaces most of the cables..
CFS Radiator
new serp belt
newer Intake of of a 2000 XJ mine is a 97 sport
Banks turbo torque Header and 2.5" pipe all the way out through a Vmax cat back muffler and a high flow Cat..

i cant compare mine to yours litterlly because i havnt done any stopwatching but she is fast and the throttle isthere whenver i need it.. i think shes fast at least....LOL

I would recommend completing your ignition upgrades and see if that helps it did for me.. plugs and wires..
What kind of gas do you use?
Naturally i am assuming the higher octane stuff..
what about your injectors?
use any fuel injector cleaner?
um i cant think of anything else..

Aaron

[j99xj]

I would recommend completing your ignition upgrades and see if that helps it did for me.. plugs and wires..
What kind of gas do you use?
Naturally i am assuming the higher octane stuff..
what about your injectors?
use any fuel injector cleaner?
um i cant think of anything else..

Aaron

My engine runs perfectly and is in the best "tune" it can be. I do run cheap gas (85 octane) but my engine absolutely refuses to ping. So I don't see any advantage to using more than 85. I do run injector cleaner so theres no problem there.

I'm starting to think my performance woes are not from a weak engine but from too tall of gearing and that my engine just doesn't have enough "leverage".

Did you see those videos I posted, and did you compare mine to the other guy's videos who posted above me?

If you haven't, you'll know what I'm talking about when I say I'm geared way too tall. My rpms just don't climb very quickly at all. And I'm still in 2nd gear at 70+ miles per hour!

[j99xj]

Update:

I raced another xj last night and I was slightly ahead of him until he pulled away at about 50 mph or so.

He had a stick, and was powershifting. And boy he was trying hard to catch me. (I could hear him chirp the tires after shifting.)

Even though I lost the race I wasn't sad. I was VERY suprised my automatic XJ held its ground against a stick. I figured I would get KILLED off the line.

By the looks and sounds of his Jeep he had intake and exhaust mods like me so it was a "fair" race.

So I'm not complaining about my Jeeps performance anymore now that I know that I'm at least on par with other 4.0s in my area.

[BBeach]

I raced my friend in his 99 xj when i had another 300 pounds, passenger and gear. We kept with each other till higher rpms where i pulled forward by maybe a fenderlength....Ive got my selfbored TB on now so maybe i can squeeze in another fenderlength. :rolleyes: