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Author: Subject: Zetec Power Problem
Double R

posted on 22/11/21 at 07:19 PM Reply With Quote
Zetec Power Problem

Evening all,

I need to do some collective brain picking as we can't seem to get any power out of the rebuilt Zetec.

It's an ST170 engine, running Jenvey 45's, on piper 285 cams, vernier pulleys and a gasflowed head with the red line set at 7500rpm.

Now the challenge we have is that it won't run over 150bhp on the rolling road, which is odd as in standard form without the cams and head, an identical enginbe ran to 189bhp.

It's pased a leakdown test, and I'm thinking the only thing it can be is low compression.

Any ideas, suggestions are very welcome as it's driving me mad!

RR

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obfripper

posted on 22/11/21 at 10:02 PM Reply With Quote
Timed to the camshaft spec, or just to the normal zetec timing bar slots in the cams?
The slots are usually about 5-10° off optimum values, the easy way to time in is to use the lift at tdc values which should be on the cam data sheet, and a dti to check/adjust the cam timing at tdc.

Dave

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cliftyhanger

posted on 23/11/21 at 07:24 AM Reply With Quote
Is this still an ST170 head?
If so is the inlet manifold an ST170 type, or std zetec?

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snapper

posted on 23/11/21 at 07:39 AM Reply With Quote
quote:
Originally posted by cliftyhanger
Is this still an ST170 head?
If so is the inlet manifold an ST170 type, or std zetec?


Says it’s on Jenvey’s

I agree cams need to be checked for correct cam timing.
No mention of ECU type





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cliftyhanger

posted on 23/11/21 at 08:02 AM Reply With Quote
quote:
Originally posted by snapper
quote:
Originally posted by cliftyhanger
Is this still an ST170 head?
If so is the inlet manifold an ST170 type, or std zetec?


Says it’s on Jenvey’s

I agree cams need to be checked for correct cam timing.
No mention of ECU type


Yes, saw that. What I meant was it must use a DCOE type inlet, but if still st170 head, the ports don't properly align with a std zetec type of DCOE inlet manifold. Danst makes an st170 specific inlet.
May explain some power loss, but probably not 40bhp

Another point, the 150bhp, was that at wheels or flywheel? Probably 25bhp there.

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Double R

posted on 23/11/21 at 11:50 AM Reply With Quote
Morning fellas, yes some good suggestions.

The inlet manifold is for a 2.0ltr Zetec with Jenvey's. The head-builder mentioned you can get a modified one, although for the cost it will be single figure gains. To answer the ECU, it's running on an Emerald K3.

The timing was the original ST170, which ran really poorly, but after a chat with Piper, we re-timed the cams and added verniers for accuracy.

It still ran very lumpy on low revs, after we did the timing, and cleared a bit after 4500rpm but still running 110bhp. So we where scratching our heads a bit.

I went for the obvious ones, new plugs, leads, coil, which did help a little bit. Compression test was low, but I know this happens on Zetecs, but the leakdown test was good. Also when it was on the rolling road, the tuner put in loads of timing to see if it would pull more power but nothing really changed.

The odd thing was, I had an identical standard 170 engine with this set-up running 185bhp before adding the cams and head so I'm thinking something must be wrong in the engine?

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Double R

posted on 23/11/21 at 11:51 AM Reply With Quote
quote:
Originally posted by cliftyhanger
quote:
Originally posted by snapper
quote:
Originally posted by cliftyhanger
Is this still an ST170 head?
If so is the inlet manifold an ST170 type, or std zetec?


Says it’s on Jenvey’s

I agree cams need to be checked for correct cam timing.
No mention of ECU type


Yes, saw that. What I meant was it must use a DCOE type inlet, but if still st170 head, the ports don't properly align with a std zetec type of DCOE inlet manifold. Danst makes an st170 specific inlet.
May explain some power loss, but probably not 40bhp

Another point, the 150bhp, was that at wheels or flywheel? Probably 25bhp there.


Yes 150bhp at the flywheel

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johnemms

posted on 23/11/21 at 12:33 PM Reply With Quote
My 2.0 Zetec out of an old ford cougar - 125ps std enging 36mm bike carbs made 155bhp ..
Changed head from a focus - ported n polished £££ - Newman fast road cams £££ - 41mm bike carbs - 170bhp ..
I have now put verniers on so maybe next year grab a few horses will also open up exhaust new headers n downpipes..
..
Are you sure you have piper cams?
Ford Cougar cams only make 155 bhp..
Justa thought...








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Double R

posted on 23/11/21 at 03:54 PM Reply With Quote
quote:
Originally posted by johnemms
My 2.0 Zetec out of an old ford cougar - 125ps std enging 36mm bike carbs made 155bhp ..
Changed head from a focus - ported n polished £££ - Newman fast road cams £££ - 41mm bike carbs - 170bhp ..
I have now put verniers on so maybe next year grab a few horses will also open up exhaust new headers n downpipes..
..
Are you sure you have piper cams?
Ford Cougar cams only make 155 bhp..
Justa thought...



So I've just had a good chat with Piper and the tuners as there is definately something off, particularly as we're 25% down.

So by deduction, the timing has been altered on the dyno for the best power, the injection system worked really well on the previous engine and the head is fresh from being gasflowed. So I'm thinking the top half of the set-up should be ok.

That then points to a bottom end problem, where there's cewrtainly no rattles/knocks etc, but the compression is down, which could well be the culprit.

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cliftyhanger

posted on 23/11/21 at 05:14 PM Reply With Quote
Was the fuelling changed? I would expect a bigger demand from a flowed head and bigger cams.

But a compression test should be easy to do, trouble is ideally you want to compare your readings to a good ST170, using the same tester (they can vary)

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Double R

posted on 23/11/21 at 07:06 PM Reply With Quote
quote:
Originally posted by cliftyhanger
Was the fuelling changed? I would expect a bigger demand from a flowed head and bigger cams.

But a compression test should be easy to do, trouble is ideally you want to compare your readings to a good ST170, using the same tester (they can vary)


Good question - we kept the fueling the same as it has 45's on it with quite large jets, but yes it may well be losing something at the top end. We had it at 180+ on this set-up though, so it could be losing a bit but I'm thinking not 40-50bhp?

Yes - I'll go an have a chat to the builder tomorrow, and get the compression test re-done. I've got a spare ST170 that's being rebuilt, so I'm thinking of swaping the bottom end

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Grimsdale

posted on 24/11/21 at 05:00 PM Reply With Quote
quote:
Originally posted by Double R
Compression test was low, but I know this happens on Zetecs, but the leakdown test was good. Also when it was on the rolling road, the tuner put in loads of timing to see if it would pull more power but nothing really changed.


if the compression test was low, but the leakdown was fine (i.e. rings and valve seats ok), it may well be cam timing, as others above have suggested.
If the exhaust valve is opening too early or the inlet closing too late you will get a low reading.


I presume the timing you're referring to is ignition timing.

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Double R

posted on 24/11/21 at 07:25 PM Reply With Quote
quote:
Originally posted by Grimsdale
quote:
Originally posted by Double R
Compression test was low, but I know this happens on Zetecs, but the leakdown test was good. Also when it was on the rolling road, the tuner put in loads of timing to see if it would pull more power but nothing really changed.


if the compression test was low, but the leakdown was fine (i.e. rings and valve seats ok), it may well be cam timing, as others above have suggested.
If the exhaust valve is opening too early or the inlet closing too late you will get a low reading.


I presume the timing you're referring to is ignition timing.


I'm glad you asked that as that's exactly the question I asked after talking to Piper yesterday

Apparently these cams have a clear window of performance, so you'll get a little bit here and there until you hit the sweet spot when there's a noticable uplift in output. So they are sensitive, and require fettling when they're on the dyno.

When it was on the rolling road, the guys played with all the usual changes, including ignition timing, but moved the exhuast quite a bit which is where the power came in. Only problem was the power moved from 115-143bhp which is a long way off.

So I had a chat with the builder (who was a bit crestfallen) who was expecting 200bhp+ and we compared ideas. Only conclusion that we can get to is that theres a compression problem, that we can only attribute to the pistons, which in fairness have not been changed, so we'd all assumed they were stock. He's agreed to strip it down to see what's the problem, potentially adding high compression pistons if needed.

I just need to get the lump out of the car and start the work!

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snapper

posted on 25/11/21 at 10:47 AM Reply With Quote
If you have changed cams they need properly setting up with degree wheel and dti gauge
The fuel and ignition map will need to be changed to suit the new cams and head, also bigger cams often need more compression ratio as more overlap reduces static compression





I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)

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djtom

posted on 26/11/21 at 09:22 AM Reply With Quote
If you have fitted verniers I assume you have removed the variable valve timing solenoid and blanked it off?

Be aware that you will need to time the cams from scratch with a dti, don't use the original timing slots or cam position as a baseline, as the variable valve timing retards the inlet cam at rest to something like -40 degrees for emissions reasons, so if this is used as baseline timing then that will certainly kill all the top end power.

Low compression ratio could be static (knackered rings etc) or dynamic (too much overlap caused by mistiming cams). Before ripping it apart I'd time in the cams properly by measuring at lift at TDC and try it again.

[Edited on 26/11/21 by djtom]

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Double R

posted on 26/11/21 at 02:00 PM Reply With Quote
Yes, there are still a few things that I need to check before taking it out.

The solenoid is disconnected, but still in the top of the engine, I've used this approach with the previous engine so I assumed this would be ok.

I've just bought the long tube so I can do a proper compression test over the weekend so I can see how low it is.

On the cam timing, the guys started with the piper settings as baseline, which ran at 110bhp. The bottom end power was also very low, which could link to the compression problem.

From there they moved the cam timing over a number of runs to get the best power out of it, which was still pretty low at 140bhp. They finally worked on the ECU mapping which got another 3.5bhp which is really strange as it's so low.

So I can see that something is fundamentally wrong with the engine as the output is increadibly low, but I'm considering finding a Zetec specialist and getting a second opinion.

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