No real power past 5,000 rpm

David P · Post by **David P** » Tue Apr 03, 2012 1:36 am

So I picked up a free 77' 530i a couple months ago. After some time driving it around, I got to noticing that the powerband pretty much just ends at 5k rpm. The engine will go past that, but doesn't really pull. even though it's more than 1k under redline. As such, my top speed seems to be limited to 100mph. Also possibly related to this is my poor fuel economy. Roughly 8-9mpg city, with 16 highway on a good day.

Real quick note on the car
My brother and I put in all new spark plugs, replaced a bad wire, put in new cap and rotor, and set the timing dead perfect.
It's currently got a good condition battery meant for an e30 shoe-horned in there (funny story).
The guy who gave it to me said that he autocrossed it for a few years, and the friend he got it from raced it for an unknown amount of time. I believe him as the car came mostly stripped for weight reduction, had two 4 point harnesses, and has Style 4 wheels with 245/45 Toyo Proxess tires.

That's it, the rest of the history on that car is a mystery.
So, any thoughts?

Falkenberg · Post by **Falkenberg** » Tue Apr 03, 2012 3:35 am

I'd check fuel/air ratio, fuel supply, and play with the ignition timing first. And check if the air filter is clean.

David P · Post by **David P** » Tue Apr 03, 2012 3:40 am

I recall the air filter being in good shape, and the ignition timing is spot on. I know I need to check the fuel system, as occasionally I will smell the hint of fuel vapors when I get in the car after it's been sitting for a couple of days.
It probably also wouldn't hurt to get a valve adjustment done, and tighten up the exhaust (it is leaking at the connection point right near the transmission).

Falkenberg · Post by **Falkenberg** » Tue Apr 03, 2012 3:57 am

What method did you use to set the ignition?
By the way, I've seen other people complain that stock M30 engines don't really pull well up to the redline. Maybe somebody with an identical engine can give you some feedback here. My E12 is not good for reference, but I did own an E32 730i M30 that used to go to the the redline quite happy.

David P · Post by **David P** » Tue Apr 03, 2012 5:00 am

My brother brought over his inductive pick-up timing light. I did some quick research here on the forum, and we timed it at the appropriate engine speed with the vacuum advance disconnected and the hose plugged.
I, too, have read that somewhere too, especially the 530i's still equipped the terrible awful thermal reactors and related smog equipment. I live in California, so we have it the worst out here. Luckily, I just picked up a set of standard headers that I believe will work (correct me someone if I'm wrong here) off an 83' 733i. I'm also setting up the car for track use, so no need for smog equipment!

Mike W. · Post by **Mike W.** » Tue Apr 03, 2012 10:05 pm

David P wrote:My brother brought over his inductive pick-up timing light. I did some quick research here on the forum, and we timed it at the appropriate engine speed with the vacuum advance disconnected and the hose plugged.
I, too, have read that somewhere too, especially the 530i's still equipped the terrible awful thermal reactors and related smog equipment. I live in California, so we have it the worst out here. Luckily, I just picked up a set of standard headers that I believe will work (correct me someone if I'm wrong here) off an 83' 733i. I'm also setting up the car for track use, so no need for smog equipment!

Wow, just saw your location, you're local!

On the exhaust, if you really mean headers, they may or may not fit off an E23, I haven't tried even a stock E23 downpipe yet. E28, which does share a very similar body, will have interference problems on the idler arm with a stock exhaust. If you're just talking manifolds, the ones off a E23 will fit, but you will need to modify the downpipes as they'll be too short and at a slightly different angle, not a bolt up to the rest of the exhaust in other words.

Getting back to your original peak power isn't far off 5K, so there isn't much benefit to revving to redline, it just means you aren't going to hurt the engine. If stock, you also have points and condenser ignition and EGR, neither of which help. Is it smooth but just no power or missing and cutting out? If the later, it might even just be plugs, again, with the conventional ignition, neither plugs or the other parts lasted long. Like maybe 5K running well.

David P · Post by **David P** » Wed Apr 04, 2012 3:06 am

Oh wow, we are located quite close! Perhaps we could meet up at some point and poke around under our hoods.

As for the exhaust, I do indeed know that the manifolds will fit fine, but not the rest of the system, due to 1) the thermal reactors are a tad longer and 2) there is a good chance the triangle flange off both the headers will have a different alignment than what is currently on the car. I'm fine will all that as I have access to a welder, and said welder belongs to a friend with far more welding and vehicular experience than I, and he is willing to help.

And indeed, back to the original issue, I forgot to thing about the points and condenser. I'll probably just end up replacing those in the near future. As for the EGR, since I will be setting this up for track with no future plans of any sort of "legal" street use, I'll be ripping out as much of the emissions systems as I can. I'll be kind of forced to anyways when I put the e23 manifolds in.

socalfiver · Post by **socalfiver** » Fri Apr 13, 2012 7:25 pm

Does it have a rev limiting rotor?