Kingman Posted March 1, 2009 Share Posted March 1, 2009 Like on my step mom's Sportage V6, it shifts out of first under full throttle at 6200 rpm with a tach max at 8000 rpm. My dad's F150 5.4L shifts out of first at 5400 rpm with the tach max at 6000 rpm. How come a Pathfinder won't seem to rev over 4700 and it has an 8000 rpm max? What determines how far an engine can rev? Timing? Valves? Cam? Link to comment Share on other sites More sharing options...
Precise1 Posted March 1, 2009 Share Posted March 1, 2009 My Pathy will rev to where ever I want, but the red line is around 6K, not 8k. Sounds like your timing is off (or something effecting the timing). That's a sure way to have a motor flatten out. Yes, it is the design/materials of the engine components, bore and stroke, valve train can be a limiting factor, etc. Simply said, you have an old truck that isn't tuned very well; stay away from redline. B Link to comment Share on other sites More sharing options...
Kingman Posted March 1, 2009 Author Share Posted March 1, 2009 (edited) Last time I checked my timing was at 12 degrees. I'll have to check again next time I go to my mom's and get a timing light on it. And by max I meant the highest number on the tach. In neutral it revs fine to redline, but in gear it just won't pick up past 4700. It just gets there and refuses to go any faster or rev any higher. This is with manual control and not letting it shift by its self. I read somethind about advancing the timing to 15 degrees? I want to rebuild the top end some time, have the heads done and replace the lifters as well as install european cams. Also, at around 4700 rpm it sort of feels like it's sputtering a little and not running right. If you say timing, could my belt have slipped a tooth? It's almost new though... Edited March 1, 2009 by Kingman Link to comment Share on other sites More sharing options...
94extreme Posted March 1, 2009 Share Posted March 1, 2009 redline.. from design of the motor. shifting etc.. ecu. Link to comment Share on other sites More sharing options...
Precise1 Posted March 1, 2009 Share Posted March 1, 2009 Always go by the redline on the tach, not highest reading the gauge goes to. Are you sure your dad didn't put a governor on your truck?? Yes, you set the base timing, but the ecu advances/retards it from there according to engine conditions. If you have poor sensors, vacuum leaks, clogged valves, etc this will make the ecu react to conditions that don't actually exist, hence spluttering, RPM flattening out, etc. That's what I mean when I said it isn't tuned very well. I don't know the TBI system well enough to recommend what to test/examine, but I believe there is a section in the manuals for that. B Link to comment Share on other sites More sharing options...
Kingman Posted March 1, 2009 Author Share Posted March 1, 2009 (edited) Always go by the redline on the tach, not highest reading the gauge goes to. Are you sure your dad didn't put a governor on your truck?? Yes, you set the base timing, but the ecu advances/retards it from there according to engine conditions. If you have poor sensors, vacuum leaks, clogged valves, etc this will make the ecu react to conditions that don't actually exist, hence spluttering, RPM flattening out, etc. That's what I mean when I said it isn't tuned very well. I don't know the TBI system well enough to recommend what to test/examine, but I believe there is a section in the manuals for that. B I just think it's weird that in so many other vehicles, the rpms use most of the tach. On mine, what's the point in having an 8k max if it won't rev past 5k. Lol I hope he didn't...he'd be getting a good I lost my manual, damnit! Which sensors? There's no vacuum leaks, I fixed all the ones that were, and valves? As in internal exhaust and fuel valves? Or EGR valves and what not? Edited March 1, 2009 by Kingman Link to comment Share on other sites More sharing options...
Precise1 Posted March 2, 2009 Share Posted March 2, 2009 what's the point in having an 8k max if it won't rev past 5k. That same gauge may have been used in several different models so all they need is a different face plate for different red line limits. This saves $ and keeps the cost of the vehicle lower; I have no problem with this. I lost my manual, damnit! Unlose one on ebay?? As in internal exhaust and fuel valves? Or EGR valves and what not? Valves in the head could affect things as they wear and don't seal as well, but mainly all the valves, diaphrams, on/around the motor. Which sensors? I don't know the TBI system well enough to recommend what to test/examine Sorry Bud, but I can't walk you through what/how to test on the internet about a system I have never worked on. B Link to comment Share on other sites More sharing options...
Kingman Posted March 2, 2009 Author Share Posted March 2, 2009 (edited) I don't know the TBI system well enough to recommend what to test/examine I read right over the "don't" in that sentence... That same gauge may have been used in several different models so all they need is a different face plate for different red line limits. This saves $ and keeps the cost of the vehicle lower; I have no problem with this. Oh yeah, true. Makes sense. Unlose one on ebay?? Getting there... Valves in the head could affect things as they wear and don't seal as well, but mainly all the valves, diaphrams, on/around the motor. Hmmmm... Oh, and I took a look at my "new" O2 sensor, and when I took it out my truck ran exactly the same. Shouldn't it run different? The top was also white powdery looking... Edited March 2, 2009 by Kingman Link to comment Share on other sites More sharing options...
SteeevO Posted March 2, 2009 Share Posted March 2, 2009 have you read any codes from the ecu? it's probably a good place to start. just my $.02 Link to comment Share on other sites More sharing options...
Kittamaru Posted March 2, 2009 Share Posted March 2, 2009 My truck can rev as high as 6750 rpm before it self-limits. Doesn't matter if I'm in gear or not, it WILL NOT go past 6750 rpm. Which is probably a good thing as that's just a hair before the solid red at 7k rpm Granted, I'm a newer 1990 MPFI engine... but eh. And trust me - she sounds mighty fearsome at 6000+ rpm... and kicks like a damn mule too XD Link to comment Share on other sites More sharing options...
Kingman Posted March 2, 2009 Author Share Posted March 2, 2009 (edited) have you read any codes from the ecu? it's probably a good place to start. just my $.02 Still clear. The problem has been around for a long while, just getting around to mentioning it. Like a lot of things... Edited March 2, 2009 by Kingman Link to comment Share on other sites More sharing options...
MY1PATH Posted March 2, 2009 Share Posted March 2, 2009 when under load mine also sputters just a little @ 4700rpm but smooths out by 5k. I just figured its the engine telling you its near its limit. I run my timing on my tbi @ 15 deg instead of 12 I also know that the mpfi vg30e is sopposed to run @ 15. I notice better fuel economy when running 15 deg but nothing else feels differant. as far as redline, like everyone else said, its the design of the engine. in the case of the vg30 there is risk of the pistons coming up faster than the valves can close @ above 6600rpm. so the ecu prevents you from doing so. Link to comment Share on other sites More sharing options...
Precise1 Posted March 2, 2009 Share Posted March 2, 2009 And trust me - she sounds mighty fearsome at 6000+ rpm... and kicks like a damn mule too XD Not for long... B Link to comment Share on other sites More sharing options...
Kingman Posted March 2, 2009 Author Share Posted March 2, 2009 My truck can rev as high as 6750 rpm before it self-limits. Doesn't matter if I'm in gear or not, it WILL NOT go past 6750 rpm. Which is probably a good thing as that's just a hair before the solid red at 7k rpm Granted, I'm a newer 1990 MPFI engine... but eh. And trust me - she sounds mighty fearsome at 6000+ rpm... and kicks like a damn mule too XD Sounds much better with no muffler at 5000 rpm in park. At idle and there are the best sounds a vg30 can make. Link to comment Share on other sites More sharing options...
94extreme Posted March 2, 2009 Share Posted March 2, 2009 run the ecu diagnostic man. mine never has cut out at redline or beyond it.. hmm Link to comment Share on other sites More sharing options...
bitemedoughboy.com Posted March 2, 2009 Share Posted March 2, 2009 when under load mine also sputters just a little @ 4700rpm but smooths out by 5k. I just figured its the engine telling you its near its limit.I run my timing on my tbi @ 15 deg instead of 12 I also know that the mpfi vg30e is sopposed to run @ 15. I notice better fuel economy when running 15 deg but nothing else feels differant. as far as redline, like everyone else said, its the design of the engine. in the case of the vg30 there is risk of the pistons coming up faster than the valves can close @ above 6600rpm. so the ecu prevents you from doing so. sounds like your cam timing is retarded by one tooth or 5° Link to comment Share on other sites More sharing options...
edicer2 Posted March 2, 2009 Share Posted March 2, 2009 (edited) my na vg30e in my 86 300zx had reved to 7 before i know mine in my pathy had got to 6500 something before also Edited March 2, 2009 by edicer2 Link to comment Share on other sites More sharing options...
bitemedoughboy.com Posted March 2, 2009 Share Posted March 2, 2009 my na vg30e in my 86 300zx had reved to 7 before i know mine in my pathy had got to 6200 before also was that loaded? just looked in my '85 FSM and the factory rev limiter is set at 6500 on the z31's not sure about the pathy specs. Link to comment Share on other sites More sharing options...
edicer2 Posted March 2, 2009 Share Posted March 2, 2009 its stock i didnt load anything. I was just driving to see if the limiter would kick in if there was one like 2 years ago and it just kept going up and up once it got to 7 i quit lol. I didnt want any valve float to happen. I know it went to 7k becasue i have a digital dash and it was clear as day. ANd for thr 6500k ish in my old pathfinder 93 was seeing if it could go as high as the z since it had the same motor but guess not. Link to comment Share on other sites More sharing options...
Kittamaru Posted March 2, 2009 Share Posted March 2, 2009 Not for long... B Oh, trust me - I rarely go near that high, and I don't hold it there long. Mostly, it's a certain on ramp we have in Harrisburg merging onto I-83... the damn thing has a stop sign at the end of the turn to face the right direction, and the "run on" space is less than 50 foot long before it's an off-ramp again (as in, you ahve about 50 feet to get up to speed before someone hits you in the ass) terrible, terrible ramp... I avoid it like the plague but sometimes I don't have a choice and I have to gun her... she always seems a little peppier after that the rest of the day XD Link to comment Share on other sites More sharing options...
edicer2 Posted March 2, 2009 Share Posted March 2, 2009 yeah you definantly dont ever hold it up there very long at all its just asking for something to break. I hardly every rev past 4 Link to comment Share on other sites More sharing options...
Kittamaru Posted March 3, 2009 Share Posted March 3, 2009 *nods* Likewise - I try my best to stay under 4k and I like to nearly idle along at 1500-2000 rpm, but when you need power, you need power - at high rpm's the VG30E can certainly deliver Link to comment Share on other sites More sharing options...
adamzan Posted March 3, 2009 Share Posted March 3, 2009 After driving a 5 speed wd today, I want one. Link to comment Share on other sites More sharing options...
SC88Pathy Posted March 3, 2009 Share Posted March 3, 2009 My 88 shifts under full throttle at around 6000. I'v only ever once hit the rev limiter, when I had the truck in first by accident. Link to comment Share on other sites More sharing options...
Kingman Posted March 3, 2009 Author Share Posted March 3, 2009 My 88 shifts under full throttle at around 6000. I'v only ever once hit the rev limiter, when I had the truck in first by accident. Hmmmm...there really be something out of wack on mine... Link to comment Share on other sites More sharing options...
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