# Miss/break up above 4500rpm **URL:** \ **Category:** NYSpeed Automotive\ **Created:** [October 7, 2011, 10:10am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249 "2011-10-07T10:10:50Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 7, 2011, 10:10am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/1 "2011-10-07T10:10:50Z")
The car in question is my '77 280z. It’s a turbocharged L28, run by megasquirt 2. Quick parts list: 72lb seimens deka injectors, aem fpr, walbro 255, evo 8 IC, full exhaust. The engine is fresh with a couple hundred miles on it. The megasquirt is triggered off the stock optical distributor and fires an MSD blaster 2 coil directly. This is not a recent problem, I’ve been fighting it all summer. It seems to happen at all boost levels, but seems more pronounced at higher boost(~10psi). Sometimes it feels like a miss, sometimes more like a power loss. AFR’s are in the mid 10’s, timing is ~23\* at 10psi. On the way to school today it started going lean(badly) anywhere in boost, the fuel pump has been sounding loud all week. I’m going to check it out later. I have datalogs available if anyone wants to see. ![http://img718.imageshack.us/img718/5895/fallingoff.png](http://img718.imageshack.us/img718/5895/fallingoff.png) ![http://img249.imageshack.us/img249/6519/fallingoff3.png](http://img249.imageshack.us/img249/6519/fallingoff3.png) Edit: in the second datalog pic, I pedaled it in 1st, that’s why the MAP does funny things. ---
**Author:** ![Onyx\_Z32](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/onyx_z32/32/7581_2.png) [@Onyx\_Z32](https://forums.speedlife.net/u/Onyx_Z32)\ **Post date:** [October 8, 2011, 5:45am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/2 "2011-10-08T05:45:09Z")
Wow a tech post that includes a datalog, lol :tup: Bump for you! ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 8, 2011, 8:02am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/3 "2011-10-08T08:02:11Z")
lol, thanks. I found a bunch of crap in the fuel pump screen, some gas tank sealer flaked off and plugged it, I now have a filter between the pump and the tank. It seems to be running good now, but I’m hesitant to call it fixed just due to how many other ‘little’ problems I’ve caught along the way, anything from a cracked distributor cap to the wrong piston rings. Power seems to fall off pretty quickly at 5200-5300, but the cam in this motor is absolutely tiny, the N/A cams aren’t big by any means, but the turbo cam is small. I think my next mod will be slapping in my extra N/A cam, people claim that it opens up another 500rpm or so on the top. ---
**Author:** ![yunvme666](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/yunvme666/32/5065_2.png) [@yunvme666](https://forums.speedlife.net/u/yunvme666)\ **Post date:** [October 8, 2011, 8:55am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/4 "2011-10-08T08:55:36Z")
did you update the firmware at all recently ? i found mine got set to a 5500 rev limit some how when i changed to ms2e . and it sounds like the same thing yours was doing as far as how it ran… go through all the screens and make sure something didnt accidentally get changed. also have you checked the plug gap , maybe go down a bit … ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 8, 2011, 12:44pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/5 "2011-10-08T12:44:55Z")
Rev limits are 6000 and 6200 for soft/hard. The problem is NOT fixed. ☹ Plug gap is .040 Look at the first datalog pic, the light blue line on top is rpm, notice how it climbs quickly, then starts climbing much slower and almost levels off. This is the power loss I’m feeling. I’m thinking this is a fuel pressure related problem, but the AFR’s don’t really seem to show it, any suggestions on a pressure sensor that I could have the MS log? I found this one, don’t see why it wouldn’t work. [http://cgi.ebay.com/ebaymotors/Pressure-transducer-sender-100-psi-oil-fuel-air-/250799543734](http://cgi.ebay.com/ebaymotors/Pressure-transducer-sender-100-psi-oil-fuel-air-/250799543734) ---
**Author:** ![donkeyballs69](https://avatars.discourse-cdn.com/v4/letter/d/f6c823/32.png) [@donkeyballs69](https://forums.speedlife.net/u/donkeyballs69)\ **Post date:** [October 8, 2011, 1:07pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/6 "2011-10-08T13:07:33Z")
I would start by closing the gap a bit and see if it helps and if it does close it some more. I was having similar problems and i went to a colder plug and went from .32 to .29 gap. Edit: I was also having problems like this on E85 and it was out of fuel pressure and my STFT would climb through out the pull. My injector duty was only 50-60%. ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 8, 2011, 1:20pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/7 "2011-10-08T13:20:51Z")
I just did a burst datalog of 3rd from ~1500rpm to 5300, power falls off smoothly at 4500 to almost nothing at 5300. I got out of it because it stopped accelerating. I can’t seem to attach a .zip of the log, it keeps saying invalid file, but here is a pic of it. It seems like the engine just says game over at 4500, valve float? ![http://img24.imageshack.us/img24/8292/3rdgeardl.png](http://img24.imageshack.us/img24/8292/3rdgeardl.png) ---
**Author:** ![donkeyballs69](https://avatars.discourse-cdn.com/v4/letter/d/f6c823/32.png) [@donkeyballs69](https://forums.speedlife.net/u/donkeyballs69)\ **Post date:** [October 8, 2011, 1:34pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/8 "2011-10-08T13:34:18Z")
Try this! Go out and do a pull but only use 1/2 to 3/4 throttle the whole pull and see what happens. When i was out of fuel pressure my car was faster @ 1/2 throttle and it would set off low fuel rail pressure code if i held 1/2 throttle till redline. It could be valves also and would def drop power @ high rpms but see what happens with less throttle. My tuner told me over and over i wasn’t out of pressure and i argued for weeks till i tried that and put my car in limp mode lol. ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 8, 2011, 1:44pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/9 "2011-10-08T13:44:43Z")
How about I turn the boost down to 8psi? Wouldn’t the AFR’s start to go lean If it was a fuel issue? ---
**Author:** ![yunvme666](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/yunvme666/32/5065_2.png) [@yunvme666](https://forums.speedlife.net/u/yunvme666)\ **Post date:** [October 8, 2011, 1:55pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/10 "2011-10-08T13:55:14Z")
email me a data log, im bored i wanna see if i see anything odd. ill pm my email… ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 8, 2011, 2:12pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/11 "2011-10-08T14:12:56Z")
Just emailed it. ---
**Author:** ![jimwildman](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jimwildman](https://forums.speedlife.net/u/jimwildman)\ **Post date:** [October 11, 2011, 12:30pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/12 "2011-10-11T12:30:19Z")
personally I think your running too much timing at 10psi and high revs, hard to see the rpm line tho… Believe me you will allmost allways feel a drop in power well before onset of det. I agree on the spark gap as well… Try that its easiest… at any rpm pull 1 degree of advance per psi… as a starting point… boosted fuel charge burns much faster so less advance is needed… much more than just a way of controlling detonation. but by all means read this if you havent… [http://www.034motorsport.com/spark-timing-myths-debunked-a-131.html](http://www.034motorsport.com/spark-timing-myths-debunked-a-131.html) ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 11, 2011, 1:55pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/13 "2011-10-11T13:55:17Z")
I had it advanced to a ‘safe’ 23 degrees using a det cans type setup, this is a VERY low compression engine at 7.4:1, I’ve had it up around 25 degrees but that was getting close to the line. Typical N/A timing numbers for this engine are ~38 degrees. ---
**Author:** ![jimwildman](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@jimwildman](https://forums.speedlife.net/u/jimwildman)\ **Post date:** [October 11, 2011, 2:08pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/14 "2011-10-11T14:08:50Z")
I hear you but honestly try a few degrees the other way you might be surprised where your optimal ignition point is. its safe and easy to try, same as regapping plugs incase there is spark blowout. ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 15, 2011, 2:33pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/15 "2011-10-15T14:33:06Z")
The first 2 pics are the same part of the log, the 3rd is earlier in the same drive at 8psi. The 2nd graph on all the logs are boost and fuel pressure-28psi. The 2nd 2 pictures have the derivative of RPM as the purple line, first at 12psi and 3rd at 8psi. Gap has been changed to .022". In the 2nd pic, dRPM falls from ~500 to ~200, just to give you an idea of the power loss. The next step is changing from hydraulic to mechanical lash adjusters, I’ve got everything, just have to do it. ![http://img443.imageshack.us/img443/1682/logwithfuelpressurec.png](http://img443.imageshack.us/img443/1682/logwithfuelpressurec.png) ![http://img5.imageshack.us/img5/821/fuelpressurewithdrpm.png](http://img5.imageshack.us/img5/821/fuelpressurewithdrpm.png) ![http://img43.imageshack.us/img43/2640/8psi.png](http://img43.imageshack.us/img43/2640/8psi.png) ---
**Author:** ![Gus](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/gus/32/5112_2.png) [@Gus](https://forums.speedlife.net/u/Gus)\ **Post date:** [October 15, 2011, 3:08pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/16 "2011-10-15T15:08:22Z")
Vince: Talk to me Jesse, this ain’t working brother. Jesse: It’s your fuel map, it’s got a nasty hole. That’s why your unloading in third. Leon: I told you it was third. Had to do it. ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 16, 2011, 5:18pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/17 "2011-10-16T17:18:46Z")
lol [https://youtu.be/zSfFx5V4dB4](https://youtu.be/zSfFx5V4dB4) I was all ready to put it back together, then I found out that the threads for one of the cam tower bolts was stripped. Hopefully I can find a helicoil kit, and not fuck it up. I think this is the last week NYIRP is open for the year. When I took the ones that were collapsed out, they sprang back and felt normal. I think the spring binds in the body. I decided to still convert to solids. ---
**Author:** ![somedude](https://avatars.discourse-cdn.com/v4/letter/s/ecd19e/32.png) [@somedude](https://forums.speedlife.net/u/somedude)\ **Post date:** [October 16, 2011, 11:29pm UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/18 "2011-10-16T23:29:30Z")
I am not at all familiar with the valvetrain on that engine other than what you talked about in the video. It just got me thinking what would cause the springs to be weak/broken under those adjusters. could it be low oil pressure at high rpm caused wear on whatever seal/valve holds oil pressure in them to keep them pumped up? Do you have a way to verify good oil pressure when you get those swapped out just to play it safe? .040 plug gap would be a bit big if this were a audi 2.7T engine or SHO engine, I had issues blowing the spark out on my turbo SHO engine at higher boost with a gap at 040 so I had to knock it down a bit to get it to clear up. ---
**Author:** ![Copper280z](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/copper280z/32/5464_2.png) [@Copper280z](https://forums.speedlife.net/u/Copper280z)\ **Post date:** [October 17, 2011, 5:04am UTC](https://forums.speedlife.net/t/miss-break-up-above-4500rpm/217249/19 "2011-10-17T05:04:55Z")
The stock oil pressure gauge(somewhat worthless) reads over halfway up the scale at anything over idle. I need to hook up a decent mechanical gauge. When I started to unscrew those lifters, they snapped up to the top like normal, every single one.