ZHP 4k Dip - Not What You Think

I had my car dyno'd back in January and a couple things came to light on the results. See attached "best run."

1) There is a noticeable dip at 4k. I feel this when I'm driving the car and it shows on the chart too. I have had the ECU reprogrammed by BMW back when the car was fairly new. It now has 89k miles on it and it seems to have returned.

2) KrisL's car was also there and he was +10 on torque, +4 on HP. His torque curve is smooth up to 4k, then increases as it approaches 4600rpms.

Our cars are nearly identical except he's got a sedan and more miles. Neither of us have done CVV, disa, or VANOS seals.

Thoughts? I have a CVV and all of the associated parts waiting to be installed. Should I do VANOS seals?

If you do the CVV, VANOS seals, VCG, and new plugs all at the same time, I`m pretty sure you`ll see a noticeable improvement throughout the RPM range.

What we REALLY need is for a Bimmer-obsessed techno-geek to build a stand-alone, RPM-selectable digital engine management unit so you could plug in your laptop and fatten up the AFR, dial in a little more spark advance, raise the rev limit, etc., on the fly....

Interesting, just looked back at my graph, and there is also a small dip at ~4k, but not as substantial as yours.

My ZSP 330Ci had a slight dip in the dyno, too. It wasn't nearly as pronounced as a ZHP, so you don't feel it while driving, but it's there, regardless.

Originally Posted by CorruptCommie

Interesting, just looked back at my graph, and there is also a small dip at ~4k, but not as substantial as yours.

ALL Double-VANOS engines have a slight dip just below 4 grand, ZHPs seem to be a bit more pronounced, probably due to the more aggressive cam grind. The VANOS utilizes 2 "turnover points" (for lack of a better term)....the intake valves begin opening earlier (around 1500 RPMs), to fatten-up the midrange torque, then at 3800, it starts holding back on them to promote top-end horsepower. The upper "turnover point" is apparent at right around 4000 RPMs, but in the majority of cases, when you`re really hammering the throttle, you blast right through this point and it`s hardly noticeable.

What *IS* truly amazing s the torque/power delivery of our engines (and makes them the envy of most other manufacturers)....look at the dyno chart, and note how FLAT the torque curve is (it`s not really fair to call it a "curve"). From just above idle `til around 6000 RPMs, the engine outputs at least 85% of its maximum torque, while still making prodigious horsepower *all the way to redline*. This is unheard of in most cases.

Originally Posted by jvr826

I had my car dyno'd back in January and a couple things came to light on the results. See attached "best run."

1) There is a noticeable dip at 4k. I feel this when I'm driving the car and it shows on the chart too. I have had the ECU reprogrammed by BMW back when the car was fairly new. It now has 89k miles on it and it seems to have returned.

2) KrisL's car was also there and he was +10 on torque, +4 on HP. His torque curve is smooth up to 4k, then increases as it approaches 4600rpms.

Our cars are nearly identical except he's got a sedan and more miles. Neither of us have done CVV, disa, or VANOS seals.

Thoughts? I have a CVV and all of the associated parts waiting to be installed. Should I do VANOS seals?

Definitely do the seals. My car only has 47K on it, but I'm going to do them this summer. I need every Hamster I can get on my slug.

Jeff,

You need VANOS seals asap man. In addition a lot of the guys at ZHPmafia have reported less 4k dip with the GAS disa rebuild. I also think your CVV is a potential problem source. I mean think about it, if your CVV isn't sucking the oil back into the pan then it is going down your cylinders and robbing you of power. Replace your needed parts and try again. I think you will see massive improvement.

I'll get my ZHP dyno'd n compare results since I've done my DISA, CCV, VCG and had my VANOS rebuilt all within 30-40K miles.

Just curious Jeff, how much did it cost to get a dyno run?

Originally Posted by av98

I'll get my ZHP dyno'd n compare results since I've done my DISA, CCV, VCG and had my VANOS rebuilt all within 30-40K miles.

I'm about to do my CVV also. I'll post up my thoughts after.

seems i'm the lucky one since my car has no signs of dip

I figured as much and thanks to all of you. I had no idea about the DISA rebuild kit... very affordable alternative to buying a new one.

Is that little pin they refer to metal? Or will I need to borrow a friend's kid to reach in to the intake to remove it, should it fall off?

Thanks to all of you. I had no idea you could rebuild the DISA. Is that little pin they mention metal or will I need to borrow a friend's kid to reach in and dig it out for me?

Originally Posted by av98

Just curious Jeff, how much did it cost to get a dyno run?

Our local BMWCCA Chapter had a Dyno day back in January. Three pulls, video and data, plus a BBQ lunch was $85. It was a really fun day. There was a Z8 with a Dinan race engine - what an experience! And an ActiveE that pulled 490 lb-ft of torque. You may read about it in our chapter newsletter, page 16:

http://ggcbmwcca.org/download/bombe/bombe13mar.pdf

We may be doing another one later in the year.

Out of curiosity what kind of Dyno did they use? Fans/temperature? They did it in fourth gear, right? Those results look very low to me!

Originally Posted by CorruptCommie

Out of curiosity what kind of Dyno did they use? Fans/temperature? They did it in fourth gear, right? Those results look very low to me!

SuperFlow Technologies all-wheel drive chassis dyno. It was cold, low 50's at best, and yes there were fans. I'm fairly certain these were 4th gear pulls.

For most of the day the readings seemed lower than expected, but we had a couple outliars. An F30 335 slushie pulled a strong 260rwhp and a Z4 3.0 pulled 201.

It really wasn't about the numbers as comparing to others who were not there makes no sense, but KrisL was there and it made sense to compare to his.

Originally Posted by heztheone

seems i'm the lucky one since my car has no signs of dip

No....*it`s there*....you`re just not aware of it....

Originally Posted by Fast Bob

No....*it`s there*....you`re just not aware of it....

u'r just hatin'

Today's the big day, dyno baseline run at TPS in Campbell for the ZHP. Will report back with results.

Looks like I have the 4K dip so far

Here are the numbers for my 05 330i ZHP auto (20% transmission loss) with 146,000 miles + the VANOS rebuilt, VCG/CCV/DISA replaced, oil dipstick o-ring , etc...

Non-Corrected:



Corrected SAE:



Random Dyno Pics:

av98, looks like my car on the dyno! Interesting results. I'd say you are doing pretty well with the slush box. It is interesting to see you have the dip as well, according to my research, BMW didn't ever release any fixes for the auto cars because apparently (and according to them) they do not suffer from the dip. I guess we now know better. Thanks for posting this up!

EDIT: and poo on BMW for not giving the ZHP 280ish hp in stock trim. They could have, but they didn't.

Originally Posted by smolck

av98, looks like my car on the dyno!

same here

Originally Posted by smolck

EDIT: and poo on BMW for not giving the ZHP 280ish hp in stock trim. They could have, but they didn't.

tell me about it

Thanks all! I figure I'm in the right range considering my AT trans loss (20%).

• 235HP x 0.20 (20%)= 47HP -> 235HP - 47HP= 188HP
• 222lbs TRQ x 0.20 (20%)= 44.4HP -> 222lbs TRQ - 44.4lbs TRQ= 177.6lbs TRQ

It was funny, the 4K dip was causing the reading to stop polling on the sensor; hence we had to do 7 runs instead of the standard 4.

Definitely love the SGM color!

280HP is pretty high, I think we could have gotten 255HP like the N52 on the 06 330i. That would have been awesome but it would be a low 5.0-5.3 0-60 car which would cannibalize their M3 sales.

Just to update you folks... I've replaced the CVV and rebuilt the DISA using the German Auto Solutions kit and my 4k dip is gone! The CVV didn't have much impact, it was the DISA. It looked fine when I had it out except that it seemed to be hanging up just a little. That would explain the intermittent dip experience I was having. Upon disassembly it wasn't worn, but had a good amount of gunk built-up on the pivot lever.

With it rebuilt the car pulls stronger and the dip is gone. It seems to rev towards redline much faster now too. Rejuvenated!!

The kit is super high quality. For those tackling it, it's not hard at all. The "use once" retaining ring they shipped with mine didn't like being repositioned so I mangled it after pressing it on too far. They warn you about that in the instructions, yet I still futzed it up. I was able to find a replacement locally after hunting around a bit - I have 99 more if anyone needs one.

When I find the time, and patience, to rebuild the VANOS, I'll report back again.