Double R
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| posted on 22/11/21 at 07:19 PM |
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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
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| posted on 22/11/21 at 10:02 PM |
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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
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| posted on 23/11/21 at 07:24 AM |
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Is this still an ST170 head?
If so is the inlet manifold an ST170 type, or std zetec?
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snapper
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| posted on 23/11/21 at 07:39 AM |
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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
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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cliftyhanger
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| posted on 23/11/21 at 08:02 AM |
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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
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| posted on 23/11/21 at 11:50 AM |
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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
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| posted on 23/11/21 at 11:51 AM |
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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
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| posted on 23/11/21 at 12:33 PM |
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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...
Own chassis & Build - First time pass!!
"7's" aren't really "cars", they are 'experiences"
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Double R
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| posted on 23/11/21 at 03:54 PM |
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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
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| posted on 23/11/21 at 05:14 PM |
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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
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| posted on 23/11/21 at 07:06 PM |
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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
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| posted on 24/11/21 at 05:00 PM |
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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
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| posted on 24/11/21 at 07:25 PM |
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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
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| posted on 25/11/21 at 10:47 AM |
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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
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| posted on 26/11/21 at 09:22 AM |
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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
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| posted on 26/11/21 at 02:00 PM |
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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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cliftyhanger
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| posted on 30/11/21 at 10:03 PM |
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Are these piper cams meant to be used with the VVT? If they are, you want "about" 40 degrees of extra advance on te inlet if the solenoid
is disconnected.
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RWD Focus
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| posted on 1/12/21 at 06:22 AM |
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When I first built my ST170 engine to put in my RWD focus, it had standard bottom end and seemed fine when in the donor car. Mine had cat cams, 45mm
throttle bodies on the rollers it made 157bhp at the flywheel. No smoking ran smooth etc but just no power. Just to say all the bores looked very good
no wear etc.
Did a compression check and all 4 cylinders were well down.
Rebuilt it with steel rods, rebore and forged pistons. Head back on with same comes, verniers etc, same throttle bodies and it made 197bhp
I think compression is probably your issue
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Double R
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| posted on 2/12/21 at 05:54 PM |
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Evening fellas - appreciate the advice and ideas
I've just had a chance to run a compression check on the engine and it tells a sorry tail.
Pressures were 1-12psi. 2-12psi, 3-20psi, 4-20psi so clearly something is up with the bottom end.
I'm going to pull it out next week and the builder is going to pull it apart, probably re-build with uprated pistons and rods. The bores were
good when originally tested however I'm considering the over-bore to remove any doubt.
Cheers
RR
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cliftyhanger
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| posted on 3/12/21 at 11:34 AM |
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Surpised it ran at all with those figures!
When I built my St170, all the rings were well and truly gummed up, and a couple broke trying to free them up.
So I fitted a set of zetec rings (no ST170 rings were available, and I was led to believe they work, which they seem to), flexihoned the bores and all
good. Does breathe a bit over 7300rpm ish, rev limit set at 7500.
I do have a spare engine, tempted to build that up later next year with a new set of pistons/rebore etc, and if you are fitting new pistons, for £150
extra I would definately rebore.
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Double R
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| posted on 3/12/21 at 11:35 AM |
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Hi all - just wanted to say a big thanks for all the messages and view points on this, really helps the thinking.
I decided to put some time into this morning as I'm back from work travels.
Test 1: So I ran the compression test again on a standard approach, all plugs out, compression test in one cylinder, turn over 5 times with cluch
pressed and throttle open.
All 4 cylinders are at 20psi.
Test 2: Added a tiny bit of oil into cylinder 1 and repeated the test which gave 100psi.
Test 3: Added approx 10ml of oil into cylinder 1 and repeated the test, this gave 150psi.
Now I'll repeat this for all cylinders, and test again once the oil has dissapated, but I'm coming to the conclusion the bores/rings
possibly pistons are goosed
RR
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