High RPM breakup

Ok so finally got everything squared away mechanically, and now I'm having an issue with a high rpm breakup..... I don't know the RPMS as I don't have a tach, but it's close to redline.


Running a 2.5 auto SBEC with bunch of fun mods (big turbo, intercooler, injectoors, etc...) I've swapped my ignition system with Known good components off my van, but I'm having the same issue all the time, with no changes, so I'm thinking it's in the tune.


Here are my two issues that may be related.

1) when trying to break torque I can't build any boost and the rpms don't even climb. I might show 1 or 2psi on the boost gauge and the car is stumbling a little.


2) when making a full throttle pull, where the trans downshifts to first, at the top end of the rpm it breaks up, almost sounds like a real fast staging limter. Air fuel is around 10.8 to 11.0 right before, then goes all over because of the rapid misses. If I put the trans in first gear and just use light throttle it will get up high in the rpms and then have the same miss, just not as violant, guessing because the car isn't under boost.

Now if I'm rolling into the throttle and the trans doesn't shift to first it will build boost and pull strong. I doubt I'm getting the rpms as high as when the engine is in first gear, as I let out of the gas around 80mph, 40 mph over the limit is fast enough for me ;)


Any ideas?

Well I'm pretty sure I fixed it. Not 100 % yet, it's rainging out and traction is an issue, but I used a Boostbutton SBEC Stage 4 cal, slightly modified, and went for a drive. Went through first gear, and hit second without missing. Ran 2nd up to 105mph and no misfire. When I let out of the gas turns out I was only going 35, so I'd had "some" wheel spin. Maybe with more load I get a different outcome, but I'll know more tomorrow.

You were using a flashable SBEC before?
Did you check the rev limit settings and method (spark or fuel cut) and spark cut fraction?
My factory tach in Mini is off and when i would be in the clear zone on the tach i was hitting rev limit in the cal.
I could check my spark cut fraction if you need, i can't remember for sure but think I'm using 4/5.

Keep in mind Wayne this is my 87 wagon that I picked up. It used to be owned and was built by TM member Wallace. It has a flashable SBEC. I honestly don't know what the issue was, but putting the Staged 4 boostbutton cal found in the cal repository fixed the issues. I was thinking that it had to do with timing but I'm not sure. Come to think of it I may be running a stage 4 cal in the van too.

Been driving the wagon past couple of days and with the exception of some cold running issues, it's running great!!!!

Good news.
I could kinda tell you weren't talking about the van. But all the same is true. But glad your new flash appears to have resolved! I liked that wagon ! Good luck with it.