4bangerjp.com
General Forums => The Mess Hall => Topic started by: bumati on December 18, 2009, 08:51:17 PM
-
1995 Wrangler YJ with a 2.5 ltr. the exhaust manifold had the usual crack so it was replaced with the banks Torque tube. It now hsa a huge flat spot at 2000 rpm it comes to life at 2500 rpm. I have a AEM brute intake /6 cylinder throttle body/ 4wd stainless cat back/ E3 or bosch +4 plugs/ DEmon coils and plug wires/ new cap and rotor. i thought the problem was the cracked manifold but now i do not know? suggestions?
-
any codes / check engine light? does it do a "nose down" or just no power?
-
Did the flat spot come before or after the header?
Just a thought,
Disconnect the battery for awhile to reset the computer.
It might just need a chance to recalibrate.
-
no codes, not a one
battery has been disconnected and rewired with heavy gauge cables/yellow top Optima
It ran like crap before, i thought it was the manifold? you could hear the leak rather loudly!! i was hoping the header would fix it, but now i don't know?
-
did you have the big tb and intake during this problem?
try going back to the stock tb and see. i may just be that the flow rate is to much for low end with the bigger tb
-
I did put the stock TB back on. i kinda figured it had to much air flowing in with the large TB. It did not change a thing. Short headers is going to take some torque but is this the norm?
-
I did put the stock TB back on. i kinda figured it had to much air flowing in with the large TB. It did not change a thing. Short headers is going to take some torque but is this the norm?
can you make a vid of whats happening so we can see what your talking about.
I know mine will do that if you catch it off guard. If I happen to lug the engine it will suck hole up to about that rpm your talking about.
it's kinda like if you shift to a higher gear to fast and lug it.
-
exactly if you do not shift fast and high in the rpm range, it will bite you on the bum! I am a old carb/jet/motorcycle guy. this is my first time at modify of an injected. the same princapal apply just do not no how to fix them
-
it's not really anything you can fix if it's the problem I'm describing. Your just outside the power band of the engine.
-
no codes, not a one
battery has been disconnected and rewired with heavy gauge cables/yellow top Optima
It ran like crap before, i thought it was the manifold? you could hear the leak rather loudly!! i was hoping the header would fix it, but now i don't know?
exactly if you do not shift fast and high in the rpm range, it will bite you on the bum! I am a old carb/jet/motorcycle guy. this is my first time at modify of an injected. the same princapal apply just do not no how to fix them
unless you have a big hole in the exhaust won't make much of a difference - the only way would be affected is if your O2 sensor gets false readings (not talking about performance header vs stock). my guess is that it "feels" better just b/c you can't hear it anymore :)
you can get a bit more power if you add some fuel but just at wot (pedal to the floor) but don't expect anything dramatic - would improve a little. Same if you shift the O2 output (for closed loop, so not at wot) although in that case you take a hit on your mpg which is not that great to begin with.
-
My experience with cracked jeep manifolds is that it takes out the O2 sensor pretty fast.
If your running a 4.0 TB it will likely runn better down low with a throttle body spacer.
Dave
-
Not great mileage? i was pulling down 22 mpg! with 31" tires i was getting 11.2 with my 33's
-
you have a exhaust leak?
I though you fixed that with the header?
-
no leaks. everythig i hooked back up. new plugs/ wire etc... it just has a giant flat spot. Will try the TB spacer.
-
no leaks. everythig i hooked back up. new plugs/ wire etc... it just has a giant flat spot. Will try the TB spacer.
it's prob just the power band of the engine now with the header. to make the power in low rpm you will need to get a cam to match and even then it may not make low end power. headers are to improve top end but you will loose torque at low end it's a trade off. re-gearing to bigger gears like 4.88's help to keep the rps up there also.
unless you do have some type of running problem? you said it ran like crap before you changed the manifold? or was it just noisy from the leak?
hope it helps. if not my advise is find a stock manifold that's not cracked and put it back on and see if you prob is gone if it is it's the power band of the header.. and if your not happy with the power band of the header you will have to just leave it stock.
I like having my power at higher rpms and just keep it in the 3-4000rpm range and I run 4.88's to help keep it up there. and someday hope to build up the engine I have with heavier springs and harsher cam to improve top end mid to top end power!!
hope this helps.
-
Yea, sometimes you can balance the longer exhaust channel by lenthening the intake path, thats why I said a TB spacer might help pull the at flat spot down, ON my engine with cams headers etc it moves the power band down 600 to 800 RPM which is perfect for me, but I have a try-Y not a matched tube header.
Dave
-
Well I was raised on the Jap 4 banger of Honda and Toyota but never a Datsun. that's right no friggin Nissans. Never owned a Kawaski for the same reason!!
I was going to go with the 4.88 gears soon, now look like sooner than later. Anybody in Columbus ohio have any experience with the swap in a ford 8.8?
The TB spacer will be on order, the longer intake makes sense.
-
Not great mileage? i was pulling down 22 mpg! with 31" tires i was getting 11.2 with my 33's
22 is great for a Jeep but far from being considered a good one nowadays - however, since it's over 20 it's really good. Anyway, that was a side note to what i otherwise said.
it's prob just the power band of the engine now with the header. to make the power in low rpm you will need to get a cam to match and even then it may not make low end power. headers are to improve top end but you will loose torque at low end it's a trade off.
imo with the Jeep stock cam wouldn't make that much of a difference, i think that would be more of a hit when you have a hi-perf cam.
-
22 is great for a Jeep but far from being considered a good one nowadays - however, since it's over 20 it's really good. Anyway, that was a side note to what i otherwise said.
imo with the Jeep stock cam wouldn't make that much of a difference, i think that would be more of a hit when you have a hi-perf cam.
I put a pacesetter header on my yj and noticed a flat spot to in the low rpm that if you hit just right the eng will suckhole bad. but if you keep the rpms flowing and don't let it get down that far it's fine. Thats why I have asked him so many times to try the stock manifold just to see if it goes away. I put my stock one back on and it fixed that flat spot but lost top end so went back to my header and got 4.88`s. and i`m hardly ever low enough on take off to cause that prob anymore. but when it does you just have to drop a gear or throw in the clutch and start your take of again or just lug it throw till it picks up at around the 2700-3000 rpm range again.
(http://i831.photobucket.com/albums/zz239/Torch_Ind/random/SSPX0645.jpg)
-
I put a pacesetter header on my yj and noticed a flat spot to in the low rpm that if you hit just right the eng will suckhole bad. but if you keep the rpms flowing and don't let it get down that far it's fine. Thats why I have asked him so many times to try the stock manifold just to see if it goes away. I put my stock one back on and it fixed that flat spot but lost top end so went back to my header and got 4.88`s. and i`m hardly ever low enough on take off to cause that prob anymore. but when it does you just have to drop a gear or throw in the clutch and start your take of again or just lug it throw till it picks up at around the 2700-3000 rpm range again.
got the same header but didn't get a chance to test it yet (still work in progress on other stuff) - once i get it moving i guess i'll find out. What you describe i've experienced with the stock header as well, but i guess it's a seat of the pants opinion - most likely regearing would improve that spot.
-
got the same header but didn't get a chance to test it yet (still work in progress on other stuff) - once i get it moving i guess i'll find out. What you describe i've experienced with the stock header as well, but i guess it's a seat of the pants opinion - most likely regearing would improve that spot.
could be mainly gearing I guess cause I think i went to bigger tires at the time to. can't remember honestly.
but the tb and header made a big difference for top end and help highway and throttle response. but I did notice that flat spot at the very low rpm if you luged it off the start but I figured it was to be expected with the mods I've done and it's still stock computer. Hoping to do some computer mapping in the future but still debating turbocharging or not. may just turbo the g/fs dd civic with a accord eng I have kicking around from my last car that I no longer have. time will tell. but definitely want to do some mapping and injector upgrade
-
Ok redid the install and checked every thing. Runs much better. Still a liittle down on torque in the lower rpms. What the problem was. I guess I will never know? Dirty connections? Did have to make a custom downpipe.