M20 - New Head, Low Power

[AWDBOB]

So,

After a long long time, I have finally come to the M20 section for your thoughts.

Last year I installed a Bimmerheads cylinder head with a 280/274 regrind, HD rockers, etc with ARP studs and a lightly ported intake manifold in hopes to pep the car up a bit.

There was no reason behind this repair, the car ran perfectly fine beforehand.

The problem that has caused me to lose all interest in the car, is that simply, after the swap, the car has no balls. Runs fine, compression is fine, starts fine, idle is a hair choppy bit figured that was normal for the cam.

Everything was replaced with fresh stuff. Plugs, timing verified several times, etc. This isn't my first rodeo, checked for vacuum leaks, etc. Install went very smooth.

The car is still crazy down on power and I have no idea why. It feels like its under load all the time. Just to accelerate normally you have to really put your foot in it. But it's not slow enough to say "there is something very badly wrong".........there's just enough to notice, "I don't think something is right".

Only other mods are magnaflow catback and an SSSquid chip.

If the HG didn't seat properly (despite good compression) could that cause it to be just barely down on power?

Intake manifold runners being ported causing improper fuel atomization?

I put the car away because I was kind of sick of it. And I want to fix it, because it is a very nice car.

Anyway, if you guys have any thoughts, let me know.

[e30sh]

Any chance you skipped a tooth on the cam timing? Leak down / compression test #'s?

[nrubenstein]

Have you put it on a dyno?

[digger]

When you say you check cam timing what exactly do you mean ?

Is the tune you running optimised for your engine?

What are the compression numbers ?

[AWDBOB]

Any chance you skipped a tooth on the cam timing? Leak down / compression test #'s?

There is a chance. I've pulled it back apart to check, but just for good measure (and my sanity) I think I will do so again. I have done so many timing belts that I don't foresee it being an issue, but we all have those days.

I haven't done a leak down yet, comp was right around 157-160ish for all 6 with a very tight grouping.

Have you put it on a dyno?

Not yet, was curious about this myself.

When you say you check cam timing what exactly do you mean ?

Is the tune you running optimised for your engine?

What are the compression numbers ?

By cam timing I mean my timing belt, crank/cam lining up. What I wanted to do but still haven't was to degree the cam in.

The tune is optimized for the build! Through SSSquid who hasn't done me wrong yet.

Compression was right around 157-160ish across the board with a tight grouping.

[digger]

Could just be a little too much cam for compression which tends to make it feel a little flat and doughy. A run on a Dynojet will tell you where you stand. My guess is it would wake a a little better with a cam gear and some advance

[ak-]

Clogged cat? Stretched out throttle cable? ECU and/or chip fiddling? Haha, hope it's not mechanical - good luck.

[packratbimmer]

The iX needs torque to spin up all of the additional load of the AWD. All of the modifications you mentioned could be adding to high end horsepower and subtracting from low end torque.

Does it run stronger after you get it wound up, say after 4,250 RPM?

[AWDBOB]

Could just be a little too much cam for compression which tends to make it feel a little flat and doughy. A run on a Dynojet will tell you where you stand. My guess is it would wake a a little better with a cam gear and some advance

Yeah, that's what I was thinking as well. I'm going to throw it on a dynojet with a cam gear and see where I stand.

Clogged cat? Stretched out throttle cable? ECU and/or chip fiddling? Haha, hope it's not mechanical - good luck.

Checked clogged cat.

Throttle cable I did not consider, but I surely will. Smart thinking.

It's a normal 93oct sssquid chip that ran great before, but it took like 6 chips to get one that worked which was odd. I've use them in every e30/e34 I've owned without issue.

I hope it's not mechanical too, we shall see. Thanks for your input, man.

The iX needs torque to spin up all of the additional load of the AWD. All of the modifications you mentioned could be adding to high end horsepower and subtracting from low end torque.

Does it run stronger after you get it wound up, say after 4,250 RPM?

I've had quite a few vehicles with a LOT of cam, and this doesn't feel like that. It feels like it's trying to pull more weight all of the way through the powerband- it's slouchy and unresponsive, comparatively speaking to the stock automatic iX I used to own. It winds up but never releases (just the tip).

I have half the mind to put a stock cam and intake back in it and see where that gets me. I'll probably accidentally solve the actual problem along the way.

[digger]

It's a normal 93oct sssquid chip that ran great before, but it took like 6 chips to get one that worked which was odd. I've use them in every e30/e34 I've owned without issue.

what do you mean by worked? the car wouldnt start with the first 5? what was different abut the current chip to get it to work?

[AWDBOB]

what do you mean by worked? the car wouldnt start with the first 5? what was different abut the current chip to get it to work?

Correct. The first many the car would just crank with no fire. I never asked what was different about the one that ended up working. But- the car ran great on that chip before I did the head work.

[AWDBOB]

Hey gents-

I finally tore the car out of storage after almost two years and got diagnosing.

First note, AK- you are a genius.

My throttle cable was EXTREMELY sloppy. Tightened it up and the difference was night and day. Car feels more responsive (now that the TB is actually opening all of the way)

BUT

I still have my hesitation off idle and it's still missing here and there- something's just not right. But it runs way too good for it to be off a tooth of timing (I think).

Check these plugs out. One side of the plug was wet on a couple cylinders and the other side dry, I'm thinking the injectors (which I got used, not rebuilt off of ebay) aren't spraying evenly.

No vacuum leaks, I've gone over everything else.

Your thoughts?

Very odd:

[bmwstudent]

1 and 5 look wet, are they?

[AWDBOB]

1 and 5 look wet, are they?

Yes sir they are! I rechecked compression tonight when I had them out too and they were right where they were at before.

Which is why I was thinking injectors.

[LJ851]

Have you tried a new set of plugs? Most fuel wet plugs are fouled.