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#1
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Torque Curve for 88 Wrangler
Does anyone know where I can get torque curve data for a 1988 Jeep
Wrangler 4.2 L with a manual transmission? My interest stems from the apparent loss of power when I recently up-sized my tires from 205/75R15s to 30x9.50R15s. I knew that I would lose some power with this change, but I'm now finding that I can't even maintain 70mph going up some of the hills on the way to work even when I downshift. Before, I could easily have maintained speed even in 5th gear. Right now, when I do get to 70 on flat terrain, I'm at about 2200 RPMs in 5th or 2850 in 4th. At 60mph I'm at somewhere around 1800 and 2300 RPMs, respectively. So I am wondering where the peak torque is for this engine. Is this power loss just something to be expected, or is there more that I should be able to get more out of my engine? |
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#2
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Welcome to the wild world of larger tires.
You need to regear now to return the torque curve to its original location. I suggest 4.10s because this ratio will work well up to 32" tires before you start to see this problem again. > wrote in message oups.com... > Does anyone know where I can get torque curve data for a 1988 Jeep > Wrangler 4.2 L with a manual transmission? > My interest stems from the apparent loss of power when I recently > up-sized my tires from 205/75R15s to 30x9.50R15s. I knew that I would > lose some power with this change, but I'm now finding that I can't > even maintain 70mph going up some of the hills on the way to work even > when I downshift. Before, I could easily have maintained speed even in > 5th gear. Right now, when I do get to 70 on flat terrain, I'm at > about 2200 RPMs in 5th or 2850 in 4th. At 60mph I'm at somewhere > around 1800 and 2300 RPMs, respectively. > So I am wondering where the peak torque is for this engine. Is this > power loss just something to be expected, or is there more that I > should be able to get more out of my engine? > |
#3
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Wow, you sound like you have some power or tune up issues.
I have been told that the engine peaks the timing advance around 2300 rpm and 2300 seems to be a real 'sweet spot' for my engine. It will just haul out fast from 2300 and hold almost any hill at that rpm. It drops off power real fast at lower rpm under load though unless I am down in the hundreds, it pulls at 400 rpm on pit walls just fine. My 5th at 65 mph is only 1750 rpm and it runs like a pig there. 4th is 2300 rpm. So basically I forget about 5th or overdrive all together and get great mileage. 11L/100km or 23 mpg. I am running 33's with 3.31 gears in my 86. I don't have the emissions computer in the loop though and my CJ didn't need a CAT when new so I have a straight pipe back to a Dynomax turbo muffler. I also have an Accel SuperCoil in there for a hotter spark. The rest is stock on a light 'glass CJ7. It sounds like you are in a strange limbo for gear ratios at regular speeds, but dropping down when in 4th at 2850 rpm means tune up issues to me. Could you have a partially blocked air or gas filter? Is your gas filter in right side up? That filter has two outlets, the center one goes to the carb and the top one goes to the return line. If the return line isn't at the top gas can syphon back to the tank when it sits making it a bugger to cold start and at high speed the gas pump pretty much matches the engine needs so if some is going back to the tank it can starve the engine. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's wrote: > > Does anyone know where I can get torque curve data for a 1988 Jeep > Wrangler 4.2 L with a manual transmission? > My interest stems from the apparent loss of power when I recently > up-sized my tires from 205/75R15s to 30x9.50R15s. I knew that I would > lose some power with this change, but I'm now finding that I can't > even maintain 70mph going up some of the hills on the way to work even > when I downshift. Before, I could easily have maintained speed even in > 5th gear. Right now, when I do get to 70 on flat terrain, I'm at > about 2200 RPMs in 5th or 2850 in 4th. At 60mph I'm at somewhere > around 1800 and 2300 RPMs, respectively. > So I am wondering where the peak torque is for this engine. Is this > power loss just something to be expected, or is there more that I > should be able to get more out of my engine? |
#4
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Well this morning, after driving to work, I checked under the hood
because I had heard an fairly loud hissing noise when I applied gas. Looking in the air cleaner I discovered a lot of oil that had come in the backside of the air cleaner. In fact the brand new air cleaner on that side was soaked and the oil was puddled about 1/4 inch deep in the back. Some was even dripping out the air intake of the air cleaner. I had just had the engine tuned with new plugs, wires, dist. cap, fuel filter, and PCV valve. When I showed it to the mechanic that did the work, he checked out the catalytic converter and discovered that it was quite damaged, as he could hear the ceramic inside rattling around when he shook it. His theory is that the converter is restricting airflow and therefore I guess causing back pressure which is causing the oil to come in from the backside of the air cleaner. I guess this sounds reasonable and could result in lack of power, and besides that, he recommeded a place other than his to do the converter work since they could do it cheaper than he could. Any thoughts? Maybe he owns the other shop, too! |
#5
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I'd bet money you have a Vac leak...I've been down this road so many times it
not even funny. I doubt your cat has anything to do with your problem. Brian 88 Wrangler |
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