Cause of low power on new Engine

[AJKOK1]

Hi All,

I hope i am posting in the right area, if not, then i apologize in advance. I have a bit of a conundrum and reading through this forum there appears to be a lot of very knowledgeable people who may just be able to offer some thought.

I have a brand new 2.0 Duratec engine ( not sure the specific engine is relevant), and it runs and feel fine. The engine in stock trim ( comes with KMS engine management and throttle bodies) should generate 185bhp. Mine generates 160bhp. I only found this out taking it to a specialist engine tuner, who were going to rolling road it, update to better cams and then re-run. They have approx 8 cars ( identical to mine) with the same engine and setup, all produced within a few BHP, 185 and all were 205+ with cams. Mine added about 15 bhp with the cams ( up to 175), but only from 6000 rpm +, BHP actually fell below 6000 revs.

All new parts, identical setup, so naturally they said something is wrong here.

This is what they have checked :

Car was run before and after fitting of cams + springs. Fuel values were setup and checked, and confirmed down on power both before and after.
Ran car on the dyno with silencer removed in case it was restricted or blocked.
Checked position of Crank Trigger
Checked throttle bodies are reaching full throttle
Carried out power runs with varying ignition trims (both plus and minus)
Drained and refilled sump to check correct oil level
Carried out a compression test ( perfect)
Rechecked cam timing, profile and tilt.

So i am stuck and the garage are stuck. They cannot see anything that would make it show consistently down on power, fuelling is all fine, next day they did another car the same as mine with the exact same engine and KMS system, again, perfect 185 stock, 205 after Cams. So there is something funny ( possibly simple) with mine.

I'm sorry this is a rather extended post, i'm really just seeking so advice from experts on what else i should look at, what might cause it to be down on power that clearly everyone so far has overlooked. Any advice of thoughts would be very gratefully received.

thanks in advance

Al.

 

[1gibson]

Gasket(s) hanging into the airflow at intake or exhaust manifold?

 

[NickJ67]

You said compressions were good, but how did they compare with the other engines that are being testing and getting the higher powers (when fitted with same cams). Just wondering if your engine has lower compression ration for some reason.

Other thing that occurs to me is that as outputs are being presumably being measured on a chassis dyno, perhaps the engine is putting out the same power but it is being absorbed somewhere down the line. Diff ratios and tyre pressures can also affect the readings.

Nick

 

[patprimmer]

Also you say cam timing is correct. How do you know this?

Regards
Pat
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[MikeHalloran]

It's brand new.
Drive it gently for 3000 miles and retest.


Mike Halloran
Pembroke Pines, FL, USA

 

[JackAction]

Although stating the obvious (but you did not say you checked it), is the air filter or intake track (leading to the throttle bodies) blocked?

Although you did not specify, I think your engine has Variable Cam Timing. Is it working properly? Meaning, is it «stuck» on the low rpm cam?

Is the EGR valve stuck (partially) open somehow?

 

[GregLocock]

Diffs wear in over the first 6000 miles, you are not just testing your engine. And yes Cynthia, a diff can absorb 20 hp, that's why they get hot.

At full power you need to check the intake vacuum, and the exhaust backpressure. Do they have a flow rate meter? use that.





Cheers

Greg Locock


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[inline6]

what happens when you overlay your entire power curve with one of the "better" ones? is it down across the entire board?

 

[AJKOK1]

Hi all,

thank you so much for your feedback.

I have some good news to report After more diagnosis over the weekend by the garage, they had another identical car come in which they fitted the same updated cams too and they got exactly the same result, down on power across the curve below 6,000 rpm and modest improvement above. As unusual as it sounds, it turns out this batch of cams are a bad lot, with the timing slots machined in slightly the wrong position. This alerted the garage to them being a possible cause, they were swapped out with a new set from a fresh batch, and bingo, the engine performed as expected on the rolling road.

The car is fitted with a LSD and as was pointed out by one of the posters, they take a bit longer to run in. At peak flywheel BHP is now 199.4 and BHP at the wheel is 170 bhp.

My engine was compression tested and was actually slightly better than many of the ones showing the improved power, so we are confident the new Cams were the cause of the bad curve and my slightly below baseline BHP was simply a symptom of a very new engine that still needs a few more miles on her to fully loosen up.

Very grateful to all your posts and suggestions. Typical the one factor not considered was the integrity of the cams themselves, still a lesson learned.

Thanks again

Al.

 

[patprimmer]

If the shop degreed the cams as they installed them, they would have found it. They where a bit lucky not to bend a valve or two.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[benta]

Glad you found the cause.

A little experience from my side:
three years ago i received my new BMW 325i E90 and was really disappointed. Having had a 330i E90 before, the 325 was incredibly lame.

But, after appr. 5000 km, it suddenly came to live and was almost as aggressive as the 330.

Seems BMW programs the ECU for a break.in periode before offering fullpower.

Benta.

 

[Tmoose]

I'm glad it got resolved.
Have you driven the car, and do you agree the performance has improved?
Higher top speed, or timed acceleration (not from a standing start) would be more meaningful than how it "feels."

I'm unclear how the "bad cams" caused your baseline test to be 160 in place of 185, and how "good cams" could make a weak engine engine strong again, unless the stock cams were somehow bad, too?
On 27 July you reported the specialist tuner had "Rechecked cam timing, profile and tilt."

On July 30 "It turns out this batch of cams are a bad lot, with the timing slots machined in slightly the wrong position."

Sounds like prior to July 27 the "checking" had consisted of reading the part number and maybe the scam, I mean cam specs out of the catalog, and on July 29 someone swapped some parts.

As Pat said, some basic cam degreeing would have prevented the confusion, rework and parts swapping.

What would have happened if you had got the only set of "bad" cams sent to the shop that week, and the rest of the batch went to other shops?
What if it was really an installation error, and the "bad cam" defense is really an excuse?
Do the dyno print outs include the correction factor in effect during the test?

Parts swapping is not really a substitute for "tuning" in my opinion. Or even legitimated basic diagnosis, much of the time.