4bangerjp.com
General Forums => The Mess Hall => Topic started by: chrisfranklin on October 19, 2009, 03:00:39 PM
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Was having a heck of a time trying to maintain 70+mph going to Vegas and back over the weekend. Altitude, hills, weight of new armor, the slightly larger tires than the old ATs probably didn't help things along in that regard.
But it's getting kind of embarrasing (maybe even dangerous) not being able to at least keep up with traffic. And, heck, most people were whizzing by me doing 80-100mph. (I also saw what must have been some kind of Nissan Skyline (sorry "GTR") club/group fly by me presumably going to Vegas. And they were driving 5 GTRs in a line and were probably doing 120mph on the I15 North)
I've still got the D35 in the back end and I wasn't looking to re-gear until I had something stronger -- maybe a D44 - back there. Supercharger is a bit more than I want to spend on this old heep w/170k on the clock and it would probably over-power the tranny and the D35 in short order anyway.
Frankly, I might head down to Turbo City in Orange County and get those guys to hook this heep up to a computer and make sure the everything checks out Air/fuel wise; the intake "creation" I've got might be throwing things off at highway speeds.
Not looking to add headers until the stock manifold cracks, but I might end up doing it; same with the electric fan business. Am I missing anything? Otherwise the vehicle is well maintained.
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my 05 stock with 33's and 2 inch lift can hold 70 with trailer of gear for hunting. have to shift alot and run higher rpm in lower gear to keep it. I have throttle body spacer and chip. heavy 4inch steam pipe bumpers front and rear with winch. I never use sixth, mostly run fifth. I have two sets of tires 33-12.5 and 285/75/r-16, the 285's roll easer and are about 9.5 to 10.5 inch wide so that does help. I take alot of road trips about 2-300 miles and I usually bite the bullet and draft people, or find a fast trucker and talk him into letting me draft him on my CB.
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I have the odd 4-banger that seems to run fine on the highway...always in 5th...running 75 mph most days...could go more, but I choose not to.
Only problem I ever have is on windy days....no real hills to speak of here.
35's with 4.88 gearing and a lot of extra armor/weight on there.
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The injector swap did a world of good for me, I actually hit 80mph last week for the first time since I've owned it.
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electric fan gives a good umph back...
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I have the odd 4-banger that seems to run fine on the highway...always in 5th...running 75 mph most days...could go more, but I choose not to.
Only problem I ever have is on windy days....no real hills to speak of here.
35's with 4.88 gearing and a lot of extra armor/weight on there.
I seem to have one of these odd 4 cyls as well :smokes:
I can easily maintain speeds above 70 MPH. Steeper, long-ish inclines are about the only thing that slow me down. Granted I don't have a lot of extra weight, but I still run around just fine.
Oh and when did you switch to 4:88's? didn't you originally go w/ 4:56's because you planned a motor swap down the road? Or did you decide to stay reliably underpowered and go deeper gear-wise :stick:
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I seem to have one of these odd 4 cyls as well :smokes:
I can easily maintain speeds above 70 MPH. Steeper, long-ish inclines are about the only thing that slow me down. Granted I don't have a lot of extra weight, but I still run around just fine.
Oh and when did you switch to 4:88's? didn't you originally go w/ 4:56's because you planned a motor swap down the road? Or did you decide to stay reliably underpowered and go deeper gear-wise :stick:
nothing odd about that, you should be able to maintain 75mph (120kph) with no problems - a lot of people get 31s and 33s and don't account for the speedo error.
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nothing odd about that, you should be able to maintain 75mph (120kph) with no problems - a lot of people get 31s and 33s and don't account for the speedo error.
You make a good point, because I was able to run 70 in 4th with 33's and stock gears, not much more really but it could. Even on longer inclines it wasn't unbearable. All I have armor wise is a gas skid, ghetto homebrew sliders, and diff skids so I don't have a lot of extra weight. Switching from 15X10 steelies to 15X8 alloy wheels made a world of difference too. I also had ZERO performance mods except a K&N filter and exhaust. I've added some since then, but 4:88's was a great investment
I could even tow my trailer no problem with stock gears, it's a 5X8 open similar to this
(http://www.caltraktrailers.com/images/p1010003_001.jpg)
Now I have no problem towing it with a light load at 65-70. I've had close to 1500 LB in it before and the 4 Banger definitely wasn't liking life quite as much :wall:
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I was also able to run 70mph on the highway without issues; I would sometimes have to downshift, but I could probably keep 75mph (I just never chose to run that fast). I run 33's on 4.88's, have about 135K on the clock, and all the mods listed on the signature (which include bumpers, sliders, hard top, winch, etc.).
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doing more then 70 mph for hours with stock set up on the engine "especially if it's getting tired" with lift and tires and armor is asking allot if you ask me. I run mine mostly around 60mph costing to 70mph down hill and with the winds and I'm running 4.88's, new engine, ported and polished intake, 64mm t/b, pacesetter header with 2 inch exhaust. I could run it faster it will do it but your running it really hard and burning allot more fuel just to get the extra mph out of it. and pulling a trailer I didn't find it any different if anything the extra weight would help you down hill and was about the same any other way your still a big tall brick in the wind lol.
you want speed to run to vegas grab a little sports car to speed down. like them gtr's.
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Mine will run 85 all day long on the highway with a trailer.... :wall: :lol: :lol:
(http://lh3.ggpht.com/_6roifxYIFVU/St3hsDcJiwI/AAAAAAAAAPU/hR2wnon19Y0/s800/Truck%20an%20Jeep.jpg)
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I have an odd 4Banger as well.
I only have 31's but can do 80+ and not much downshifting, only on major hills.
Mine seems to have a lot of get up and go as well. I can get up to traffic speed rather quick(maybe it's my Nascar like shifting?).
I shift around 3000 to 3500 so that helps out quit a bit.
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I'm running 33x12.5R15's with were alot harder to turn then my 31x10.5R15's I could get more speed out of it before I went to the bigger wider tire.
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I mean my 4Banger will do 80-85mph on flat highway and slight inclines the way it's currently setup. But as soon as there is anything in the way of a mild hill to climb on the highway it feels like the fuel flow gets cut in half and I'm slinging down to fourth and even third in some cases.
Zinging along in 3rd gear at 4500RPM just going 60mph when everybody else is doing 75-80 going up a mild incline in a posted 70mph zone just plain $ucks. You guys will say that's the nature of the beast -- 4banger, tires, weight, etc -- but I still feel like something is "off" with the engine ("Yeah, it needs another 4 cylinders...that's what's "off" about it :lol:)
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I mean my 4Banger will do 80-85mph on flat highway and slight inclines the way it's currently setup. But as soon as there is anything in the way of a mild hill to climb on the highway it feels like the fuel flow gets cut in half and I'm slinging down to fourth and even third in some cases.
same here, opposing wind too - funny how the top speed increases when you go the other way.
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I think mine tops about about 65 with 4.10's and 35's, it might be able to hit 70 if the wind is with it
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I think mine tops about about 65 with 4.10's and 35's, it might be able to hit 70 if the wind is with it
is it 65 what your speedo shows or based on gps or adjusted speedo reading?
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I'm talking gps. my speedo reads faster then your actually going now with the 4.88s not much out but still go by my gps.
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I'm talking gps. my speedo reads faster then your actually going now with the 4.88s not much out but still go by my gps.
yeah, gps is good - i thought you said 35s and 4.10 (actually that was TrailLessTaken), that's why i was asking - but from what i know even with 4.88 and 35s should still show less than what your real speed is (unless you changed your speedo gear) - my understanding was that 33s and 4.88 is close to stock speedo reading
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Not correcting your speedometer will have an effect on performance as the PCM uses the vehicles speed to adjust the timing and I believe the fuel curve. Not to mention its a cheap fix.
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Not correcting your speedometer will have an effect on performance as the PCM uses the vehicles speed to adjust the timing and I believe the fuel curve. Not to mention its a cheap fix.
Ah, very interesting. Didn't think of that.
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Not correcting your speedometer will have an effect on performance as the PCM uses the vehicles speed to adjust the timing and I believe the fuel curve. Not to mention its a cheap fix.
Is the PCM adjustment to the timing/fuel curve pegged to the speed as shown on the speedometer or to the actual vehicle speed? My speedometer reads about 5mph slow vs GPS readings. I'm figuring the PCM adjustment to the timing/fuel curve is pegged to the speed shown on the speedometer. I'' have to get this adjusted
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The PCM reads speed by way of the VSS which is tied into the speedometer.
http://4bangerjp.com/forums/index.php/topic,731.0.html
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It's a 15 min job and is dirt cheap, mine's been corrected 3 times now for the tires I've run. Hard to believe anyone would deal with the wrong speedo gear as cheap and simple as the fix is.
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It's a 15 min job and is dirt cheap, mine's been corrected 3 times now for the tires I've run. Hard to believe anyone would deal with the wrong speedo gear as cheap and simple as the fix is.
who carries the gears? i am fine now but i want to get a 39T in case i ever go to 35s. and how much is one if you remember.
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who carries the gears? i am fine now but i want to get a 39T in case i ever go to 35s. and how much is one if you remember.
Try the Dealer. They are usually under $30.
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Dealer for sure, my last one was $22-23 IIRC
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mine isn't far off. maybe 5-7km's with the 33's with 4.88's.
don't think it would do much to my timing on my old YJ lol being stationary distributor. the tj's with coil over plug would prod adjust for speed and various other conditions.
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mine isn't far off. maybe 5-7km's with the 33's with 4.88's.
don't think it would do much to my timing on my old YJ lol being stationary distributor. the tj's with coil over plug would prod adjust for speed and various other conditions.
Timing isn't controlled by the distributor.
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hate to butt in, but if i follow you guys correctly the ecu adjusts from vss inputs so in my 86 xj with no vss, just regular old cable driven type, it wouldnt matter (to ecu) if my speedo gear is wrong tooth count.
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ya the tbi system doesn't have a speed input to the ecu.. :stupid:
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ya the tbi system doesn't have a speed input to the ecu.. :stupid:
No one cares about you guy's. :lol: :doggy:
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Not correcting your speedometer will have an effect on performance as the PCM uses the vehicles speed to adjust the timing and I believe the fuel curve. Not to mention its a cheap fix.
at what size tire do you need to adjust the speedo? are 31s barely big enough to make a difference?
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at what size tire do you need to adjust the speedo? are 31s barely big enough to make a difference?
i think 31 is 10% off - that means when you're seeing 60mph you're travelling at 66 - same for mileage, your odometer changes by 1000 miles you traveled 1100. mpg as well btw, so your mileage is actually better.
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at what size tire do you need to adjust the speedo? are 31s barely big enough to make a difference?
Yes, 31's are enough to throw it off 5-6 mph at highway speed.
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I don't know but I feel like I've been having problems at highway speeds when I went up from the original tires to 29ATs, then 31MTs. Pretty small leap in size I know, but even with the 29ATs, it seemed like the engine would start "dialing" back at higher speed (especially noticeable when it was under load on inclines ).
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is it 65 what your speedo shows or based on gps or adjusted speedo reading?
If I remember I think that is adjusted, I never bothered fixing mine, cause I mainly just drive mine to the gas station or run in to town to get some food, so I never really get going more then 45 or so
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Well it looks like I am down for a 38 tooth according to the chart -- 4.11, 31". Of course, I am going to measure the tire-diameter aired up to what I use on the street just to make sure the tires are truly 31s.
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To be the most accurate, measure from the ground to the center of the hub and multiply by two.
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The 31MT Firestone Destinations I've got measured 31" at 38psi. So I went ahead and ordered a 38 tooth speedo gear and gasket according to the 4banger chart
Here's the unexpected deal though: I sit there and looked at sites like Quadratec and their chart shows 4:10/31" should use a 36 tooth! Then I read around and apparently some believe that Quadratec is errantly alternating between charts and that 38 tooth is the way to go for those aforementioned parameters.
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Wheel width along with air pressure will also come into play as a wider wheel will make the tire sit flatter while a narrow tire (at the same pressure) will be a bit overinflated. Not to mention height differences between brands and AT and MT', Bias Ply and Radial Ply...
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Timing isn't controlled by the distributor.
yes it is. why do you think people with performance v8's advance the distributor for more high end output and they call it advancing the timing!!!
they also had centrifugal weights in the older distributors to advance timing at higher rpm!!
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yes it is. why do you think people with performance v8's advance the distributor for more high end output and they call it advancing the timing!!!
they also had centrifugal weights in the older distributors to advance timing at higher rpm!!
You cannot adjust the timing on the Jeep. You even said it yourself. The way you can change the timing is by adjusting the CPS. Then the PCM backs or advances the timing.
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yes it is. why do you think people with performance v8's advance the distributor for more high end output and they call it advancing the timing!!!
they also had centrifugal weights in the older distributors to advance timing at higher rpm!!
sorry man but you're wrong , the timing on the Jeep is controlled by the PCM on a predefined map (a table, not the map sensor) - it uses inputs from sensors to calculate the advance timing based on rpm, map sensor reading, tps and i think the IAT. the table is stored on 2 dimensions rpm and vacuum (map reading) and i think the tps and IAT come in play to adjust the predefined advance. not sure if the coolant temperature is used or not for the Jeep but i believe i saw somewhere that is used on some vehicles. You are right about some v8 distributors that you can rotate them to change the initial advance and also change the weights and/or springs to adjust the curve - all late ECUs use an advance map and calculations to determine the correct degrees of ignition advance though.
you can do it like Jeffy said by changing the cps position which will basically tell the PCM that the TDC is at a different location than it actually is - the downside with that is that you might get out of sync with the cam sensor but i'm not sure what the difference would be to affect the PCM so it could be safe. I don't know on top of my head what the diameter of the flywheel is on the 4banger but guessing here if let's say it is 20'' then you will need to move the CPS about 3/16 of an inch (0.1875'') to get 1deg change in advance - for that it should be fine but if you want to retard or advance the ignition like 4 degrees that can be a problem since you'll run out of room on the bellhousing opening (you'll need to move the cps 3/4'').
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you can do it like Jeffy said by changing the cps position which will basically tell the PCM that the TDC is at a different location than it actually is - the downside with that is that you might get out of sync with the cam sensor but i'm not sure what the difference would be to affect the PCM so it could be safe. I don't know on top of my head what the diameter of the flywheel is on the 4banger but guessing here if let's say it is 20'' then you will need to move the CPS about 3/16 of an inch (0.1875'') to get 1deg change in advance - for that it should be fine but if you want to retard or advance the ignition like 4 degrees that can be a problem since you'll run out of room on the bellhousing opening (you'll need to move the cps 3/4'').
I've heard it's good for a few degrees at most. There isn't much room to do more then that anyway. otherwise, the best option is to get a programmable PCM and control it all by computer.
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Speaking of 4Banger Jeep Speed, Jp magazine is showing a Turbo 4 cylinder in their latest newstand issue. Didn't see who was making it -- must be a project.
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sorry man but you're wrong , the timing on the Jeep is controlled by the PCM on a predefined map (a table, not the map sensor) - it uses inputs from sensors to calculate the advance timing based on rpm, map sensor reading, tps and i think the IAT. the table is stored on 2 dimensions rpm and vacuum (map reading) and i think the tps and IAT come in play to adjust the predefined advance. not sure if the coolant temperature is used or not for the Jeep but i believe i saw somewhere that is used on some vehicles. You are right about some v8 distributors that you can rotate them to change the initial advance and also change the weights and/or springs to adjust the curve - all late ECUs use an advance map and calculations to determine the correct degrees of ignition advance though.
you can do it like Jeffy said by changing the cps position which will basically tell the PCM that the TDC is at a different location than it actually is - the downside with that is that you might get out of sync with the cam sensor but i'm not sure what the difference would be to affect the PCM so it could be safe. I don't know on top of my head what the diameter of the flywheel is on the 4banger but guessing here if let's say it is 20'' then you will need to move the CPS about 3/16 of an inch (0.1875'') to get 1deg change in advance - for that it should be fine but if you want to retard or advance the ignition like 4 degrees that can be a problem since you'll run out of room on the bellhousing opening (you'll need to move the cps 3/4'').
dude I'm not going to argue if you think your right whatever. i'm a licensed tech and my jeep doesn't have variable valve timing or spark timing the only adjustments the pcm in my 95 yj has is fuel timing and length of timing. That's it. Honda "vtec" and other manufactures in newer engines have variable valve timing and spark timing. you can't control spark timing in a distributor unless you move it or have some kind of mechanical advance built in to the distributor witch my yj doesn't. if the pcm changed the spark timing it would make no difference due to the rotor isn't in contact with the distributor cap prongs. the coil can't discharge the energy unless it has somewhere to go. In terms it would short out the coil.
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dude I'm not going to argue if you think your right whatever. i'm a licensed tech and my jeep doesn't have variable valve timing or spark timing the only adjustments the pcm in my 95 yj has is fuel timing and length of timing. That's it. Honda "vtec" and other manufactures in newer engines have variable valve timing and spark timing. you can't control spark timing in a distributor unless you move it or have some kind of mechanical advance built in to the distributor witch my yj doesn't. if the pcm changed the spark timing it would make no difference due to the rotor isn't in contact with the distributor cap prongs. the coil can't discharge the energy unless it has somewhere to go. In terms it would short out the coil.
dude, first off i am saying the same thing regarding the inability of adjusting the timing by moving the distributor, so there's no point in an argument there, but read my post again and you'll see that's what i meant (including the quote from you to which i replied - here it is:
Timing isn't controlled by the distributor.
yes it is. why do you think people with performance v8's advance the distributor for more high end output and they call it advancing the timing!!!
they also had centrifugal weights in the older distributors to advance timing at higher rpm!!
if you don't believe me take the distributor out and try to move the rotor while holding the gear - it will not move. Now do the same on a points one and it will move - the ignition advance will vary even though the position of the rotor will not change in relation to the TDC of the cylinders it fires the spark to, so when you have 10 deg advance in timing the rotor won't move forward 5 degrees to compensate.
if the pcm changed the spark timing it would make no difference due to the rotor isn't in contact with the distributor cap prongs. the coil can't discharge the energy unless it has somewhere to go. In terms it would short out the coil.
the rotor is never in the contact with the prongs, and no it will not short out the coil, you can test that by removing the wire from the coil to the center of the dist cap, crank the engine and see what happens, then put it back on and it will start with no problems.
Anyway, whatever (like you said), i'll quit trying to explain since you are a certified tech and we are not.
EDIT: It is explained even in the Jeep Factory Service Manual that you can download from the FAQ section on this site
under general information of the fuel system (page 19 in file 95xj_14.pdf) you can find this
"The PCM is a preprogrammed, dual microprocessor digital computer. It regulates ignition timing, air-fuel ratio, emission control devices, charging system, speed control, air conditioning compressor clutch engagement and idle speed. The PCM can adapt its programming to meet
changing operating conditions"
and also this right under the one above
Powertrain Control Module (PCM) Inputs represent the instantaneous engine operating conditions. Air-fuel mixture and ignition timing calibrations for various driving and atmospheric conditions are preprogrammed into the PCM. The PCM monitors and analyzes various inputs. It then computes engine fuel and ignition timing requirements based on these inputs. Fuel delivery control and ignition timing will then be adjusted accordingly"
on page 31 in file 95xj_14.pdf, section Fuel system component description/System operation - under the engine startup mode section it states "The PCM determines the proper ignition timing according to input received from the crankshaft position sensor"
under engine warm-up mode you'll also find this "² The PCM adjusts engine idle speed through the idle air control (IAC) motor and adjusts ignition timing"
and on the next page (page 32 in the same file) it says "The PCM adjusts ignition timing by increasing and decreasing spark advance" and further down under cruise mode "The PCM adjusts ignition timing by turning the ground path to the coil on and off"
- i believe the official service manual to be correct (and it is the same for most modern engines, not just for Jeeps). copy/paste from the manual below
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if the pcm changed the spark timing it would make no difference due to the rotor isn't in contact with the distributor cap prongs.
the one thing you are correct about is that the rotor metal needs to be as close as possible to the dist cap prongs - for that matter, since the rotor does not move with the ignition advance that metal portion at the end of the rotor covers about 20 deg, if you look at old style distributors with centrifugal advance the rotor has a smaller metal end (covers about 5 deg) and you guessed right that they need to be aligned, they never touch but are very close, there is a spark there as well as the spark plug and if you watch an engine running at night or in the dark on some distributor caps you can actually see the sparks under the cap
this was so I am fair, got a bit thrown off by the way you answered in the reply and i felt that i wasn't all nice in mine either
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Speaking of 4Banger Jeep Speed, Jp magazine is showing a Turbo 4 cylinder in their latest newstand issue. Didn't see who was making it -- must be a project.
http://www.505performance.com/
The turbo kit came from these guy's.
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the one thing you are correct about is that the rotor metal needs to be as close as possible to the dist cap prongs
Not to mention, the contacts are large and do allow for a few degrees of advance or retard. I don't think you can go more then a few degrees without then getting out of sync with the mechanical's.http://www.505performance.com/
The turbo kit came from these guy's.
It's surprising to see anything from them. They brought out their first kit several years ago then did nothing with it. I see they have a 2.5L pictured with the turbo. $3000 is a lot though.
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Not to mention, the contacts are large and do allow for a few degrees of advance or retard. I don't think you can go more then a few degrees without then getting out of sync with the mechanical's.
pretty much translated in 1/2 the degrees to the dist since it's 1 full rotation for every 2 crank rotations
It's surprising to see anything from them. They brought out their first kit several years ago then did nothing with it. I see they have a 2.5L pictured with the turbo. $3000 is a lot though.
$4,550 for the JK supercharger (centrifugal procharger unit) kit only with FMU (no fuel/timing ECU) - quite expensive.
$5,100 for the turbo kit with Accel Fuel management and Intercooler - $3,900 for the DIY kit with the same intercooler and Accel ecu but still high priced since you need to fab everything else.
I wonder how many of these they actually sell.
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I wonder how many of these they actually sell.
I highly doubt they sell more then 5 a year if that. I forgot that they made a kit since they do not advertise. I think the only other company to make a kit was Turbo City but they stopped as they didn't want to get CARB Certification and it was already a slow seller.
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You can't go wrong with Bounty Hunter's 62mm throttle body and spacer. Just remember to grind or bore the intake manifold. The difference it made on mine was substantial.
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Haha. I remember getting mine up to 66mph once! ha
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who carries the gears? i am fine now but i want to get a 39T in case i ever go to 35s. and how much is one if you remember.
I have a bunch, let me know what you need. If I don't have it, I recommend www.tacomaspeedometer.com . Cheap and ship fast.
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I have a bunch, let me know what you need. If I don't have it, I recommend www.tacomaspeedometer.com . Cheap and ship fast.
i think i need the 39T for 35s and 4.88s, but i need the short version (YJ '95)
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29,30,33,34,35,37 is all I have, seems the 39 and 41 are pretty popular with the lower gearsets. The long shaft/short shaft are interchangeable, just swap the gear onto whichever length shaft you need. I would highly recommend Tacoma Speedometer at the above link.
I would also recommend this Universal Speedometer Signal Interface from Dakota Digital, pretty cheap ($80) and can adjust your speedo for any tire size or gear ratio, and for any drivetrain/ECM combination for that matter. I run one, works great as I run two different sizes of tires between my road and offroad tires, adjusting the speedo is just a few pushes of the button below the dash. I also HAD to run one since I installed a super-short SYE and it no longer uses a speedo gear. http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=287/home_id=59/mode=prod/prd126.htm
(http://www.dakotadigital.com/cartimages/prd_zm_126.jpg)
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with 33/12.50's and stock gearing (no speedo correction either) I can only maintain 45mph in 5th which is roughly 53mph after correction. In 4th gear I can maintain 60-65mph on the speedo or about 70-75mph corrected but it sucks down some gas at that speed. This is all at about 1/2 to 3/4 throttle input with one to two passengers and no load.
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I put in the 38 tooth today and it worked fine right off the bat. There's a little metal bump at 6 o'clock on the VSS port opening on the transfer case. You just apparently need to line up your teeth-range numbering on the VSS -- mine was 31(2?)/38 -- directly over that little metal bump and you're all set. I also put in a new gasket, then reset battery. Feels like its driving better already.
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29,30,33,34,35,37 is all I have, seems the 39 and 41 are pretty popular with the lower gearsets. The long shaft/short shaft are interchangeable, just swap the gear onto whichever length shaft you need. I would highly recommend Tacoma Speedometer at the above link.
I would also recommend this Universal Speedometer Signal Interface from Dakota Digital, pretty cheap ($80) and can adjust your speedo for any tire size or gear ratio, and for any drivetrain/ECM combination for that matter. I run one, works great as I run two different sizes of tires between my road and offroad tires, adjusting the speedo is just a few pushes of the button below the dash. I also HAD to run one since I installed a super-short SYE and it no longer uses a speedo gear. http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=287/home_id=59/mode=prod/prd126.htm
(http://www.dakotadigital.com/cartimages/prd_zm_126.jpg)
I still haven't installed this...do you mind doing a quick write up of how you wired it in so I'm not starting from scratch?? :thumb:
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I put in the 38 tooth today and it worked fine right off the bat. There's a little metal bump at 6 o'clock on the VSS port opening on the transfer case. You just apparently need to line up your teeth-range numbering on the VSS -- mine was 31(2?)/38 -- directly over that little metal bump and you're all set. I also put in a new gasket, then reset battery. Feels like its driving better already.
does correcting your speedo actually optimize engine performance?
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does correcting your speedo actually optimize engine performance?
Yes, the ECU uses the speed data in its calculations...
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I still haven't installed this...do you mind doing a quick write up of how you wired it in so I'm not starting from scratch?? :thumb:
It's not that hard. I talked a friend through it over the phone once. :lol:
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I had a guy want me to talk him through a timing chain on the phone,
he normally could not change his own sparkplugs....
I told him to go to Autozone rent a puller and call me
when he had the dampener off the engine...............
He called me like 3 weeks later.....
:roflol:
Dave
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Yes, the ECU uses the speed data in its calculations...
awesome, since I run 33's and stock gearing without a corrected speedo I wonder if it would be worth while till I put some gears in it down the road.
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Most people that do recal the speedo notice a decent little bump in mileage,
as well as a smoother running engine under load. Not earth shattering but a nice tweek.
Off to add it to the mod list... :)
Dave
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awesome, since I run 33's and stock gearing without a corrected speedo I wonder if it would be worth while till I put some gears in it down the road.
I would recommend to do it, because it is cheap and quick...
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I would recommend to do it, because it is cheap and quick...
Anywhere in particular you recommend getting it from? I will definatly do it as the jeep gets driven quite frequently, seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...
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I put in the 38 tooth today and it worked fine right off the bat. There's a little metal bump at 6 o'clock on the VSS port opening on the transfer case. You just apparently need to line up your teeth-range numbering on the VSS -- mine was 31(2?)/38 -- directly over that little metal bump and you're all set. I also put in a new gasket, then reset battery. Feels like its driving better already.
And I also checked the speedo vs. gps at lower speeds and a variety of highway speeds -- 55-80 -- yesterday and it looked like the speedo and gps were fairly dead on.
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Anywhere in particular you recommend getting it from? I will definatly do it as the jeep gets driven quite frequently, seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...
Try dakota... They can even custom make if you need them to (I didnt go this way when I had 31's and 4.88; I know I was going to 33's soon and was not willing to spend the dough, but they offered to make it).
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Anywhere in particular you recommend getting it from? I will definatly do it as the jeep gets driven quite frequently, seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...
the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..
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Anywhere in particular you recommend getting it from? I will definatly do it as the jeep gets driven quite frequently, seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...
i was told here that the gears are the same just the shaft is different (shorter for 91+) and that you can put the new gear on the old shaft
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the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..
Guess I am going to leave it alone if thats the case... I will just use my gps for a speedometer.. Thanks for the info!
i was told here that the gears are the same just the shaft is different (shorter for 91+) and that you can put the new gear on the old shaft
good to know thankyou!
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the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..
Yes, when I replaced my transfer case I dont think the speedo cable got hooked up correctly because my speedo isnt working... Anyway, that explains why I havent noticed any change in performance. Thanks.
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Anywhere in particular you recommend getting it from? I will definatly do it as the jeep gets driven quite frequently, seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...
The long and short shaft are interchangeable on the gears, I may be able to set you up if you know what gear you need.
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The long and short shaft are interchangeable on the gears, I may be able to set you up if you know what gear you need.
I used the thread in faq and found that I needed the 36 tooth, but from other sites it says the 35 tooth....
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I have a 35.
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I have a 35.
I am pretty sure that is what i need, i will go out and actually measure the tire tomorrow.
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I used the thread in faq and found that I needed the 36 tooth, but from other sites it says the 35 tooth....
Speedometer gears aren't an exact science since tires can vary even when the sidewalls say the same size. I have adjusted some of the numbers that I have actually tried. Still, any chart should get you without 5mph of 'prefect'. Mine is currently for all intensive purposes dead on.
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Speedometer gears aren't an exact science since tires can vary even when the sidewalls say the same size. I have adjusted some of the numbers that I have actually tried. Still, any chart should get you without 5mph of 'prefect'. Mine is currently for all intensive purposes dead on.
yes sir, exactly why I am going to take the good ole tape measure to my tires!!
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I have a 35.
the outer diameter of my tire is 32 inches.