What power to expect?

[NigelO]

I picked up my Westie on Sunday, but I already knew it needed a tweak to the maps, as it has an awful coldstart, dodgy tickover, fluffy throttle response off idle and the occasional spit back through the TBs

I was previously mapped to 172bhp, which feels a little bit low, especially when reading the power levels of similarly-specced cars.

So - for the experienced owners on here, what do you think I should reasonably expect from the following spec:-

• 2l Zetec Silvertop
• 270 degree cams
• Three-angle valve seats
• Skimmed block (CR unknown, but presumably slightly up over standard)
• 45mm Jenvey TBs
• DTA E48 ECU

I want something that behaves nicely in traffic and doesn't require gobfuls of throttle to pull away, but at the same time, a few extra ponies aren't to be sniffed at

I'll probably be going to for a day's dyno work at Bailey Performance when the sun comes out... Any predictions?

[Kingster]

I guess it depends on what the “270” cams are exactly and if there’s any other head work. 

My Old silver top on throttle bodies was 168bhp  so maybe 10-15bhp more for a set of fast road cams?

Therefore my guess 180.5bhp 

[rjc4176]

Mines a 2.0 zetec silver top,it made 173bhp at the wheels with piper fast road cams,ported head skimmed block on a fresh rebuilt engine last year with 45 webbers,about 2 years before with a standard head and 130 cams made about 145bhp at the wheels on the same dyno

[DamperMan]

Omex throttle bodies bog standard 2.0 black top.  178 bhp.  So i’d hope the extra work done to your engine would produce more.   Mine runs great on full throttle or normal driving light throttle, but sometimes coughs on mid throttle so the map probably needs some more development.    Longer duration cams,  and higher CR’s will make a more peaky engine which is less forgiving if the maps off.   Still with electronic control it should be possible to get the best possible drive ability from that engine.   Personally i’d check the obvious stuff first before handing the keys to a rolling road.   Like no inlet leaks, spark plugs, leads etc. Air meter the inlets to make sure they are all set the same.  Sometimes the adjustment screws on the butterfly’s  or bleeds move..   If you know the cam supplier they should be able to give pretty close  timing info.    If you have the software and cables it’s worth checking the  throttle pot set up correct.   Ecu getting  the right kind of temperature figures for air and engine.    Beyond that i’ve Looked at map tables and all the correction factors and decided that needs a rolling road. 

[Kingster]

1 hour ago, DamperMan said:

Omex throttle bodies bog standard 2.0 black top.  178 bhp.  So i’d hope the extra work done to your engine would produce more.

Blacktops tend to do more than Silvertops I reckon. I went from 168bhp on std silvertop to 183bhp on std blacktop. Must have got a good one mind 

[Kevin Wood]

If it's suffering the drivability issues you report now, I think it's probably worth going back to basics and checking the cam timing (against the spec for whatever cams it has - most modified cams aren't set correctly on the Ford alignment marks), TPS alignment, all other ECU sensors,  throttle body balance, lambda sensor operation if it has one, check the compression and give it a fresh set of plugs before doing anything else.

If that has cured the running issues, then enjoy. If not, then you need to dig deeper yourself or take it to someone who can diagnose / map it.

Rolling road power readings are notoriously inaccurate, with some being conservative, and others fiddling the results to keep the customer happy on top of the basic lack of repeatability that you can get with a rolling road dyno. Some engine tuners are optimistic with the power claims for their products too. 

What matters is that the engine has been tuned for optimum power in the spec in which it is presented.

A zetec on throttle bodies in that spec. and properly tuned will never need " gobfuls of throttle to pull away " - quite the opposite,  so fear not, you probably just have a few niggles to sort out.

[Kingster]

23 minutes ago, Kevin Wood said:

Rolling road power readings are notoriously inaccurate, with some being conservative, and others fiddling the results to keep the customer happy on top of the basic lack of repeatability that you can get with a rolling road dyno. Some engine tuners are optimistic with the power claims for their products too. 

Couldn’t agree more!

Really useful for a session start and finish comparison - but you can never really compare one dyno result to another.

My car drives great especially around the 3500 to 5500 rev range I tend to use most - so I’m very happy. Plus I have a nice “pub” dyno print out to show for it 

[NigelO]

I've probably paid for 30+ dyno / mapping sessions in my 15 years of modifying my Fiat Coupe 20VT, so I know first hand that the peak power figure from a dyno run has very little bearing on how fast the car feels. Its all about "area under the curve".

My Coupe felt fastest when it was delivering about 400bhp - fairly early spool, followed by a huge mid-range, just tailing off at the top end. I've now gone further still and I've peaked at 488bhp. Its still monstrous in the mid-range, but all the excitement is from 5,000rpm through to 7,500rpm. This means that on the rare occasion when I I get to let it off its leash, its utterly ballistic, but for 98% of the time, its just a laggy turbo-nutter Fiat that struggles to keep up with an enthusiastically driven 320D....

I'd love to get the Westy to 185 - 190bhp, but I'd much rather have a 175bhp car that drives nicely and has great throttle response and calm manners

I'll check some of the basics, but I'm happy to throw a couple of hundred quid at some proper expertise to get everything sorted properly

[Zetecinside]

Bhp is not worth predicting as its pretty much meaningless. Why, well take any engine, set it up for great fuel economy. Your bhp will be x amount but your doing 50mpg.

Take same engine and increase fuel till its on border of washing every ounce if oil from the bores, you will now have more bhp than initially but only get 30mpg.

In a weeks time take it to a different RR. Use both maps and i bet your power will again be different.

A good RR operator would not sacrifice torque for peak power unless thats what was asked for. 

Just my thoughts.

[Kevin Wood]

3 hours ago, NigelO said:

I'll check some of the basics, but I'm happy to throw a couple of hundred quid at some proper expertise to get everything sorted properly

My point was that, if you turn up at a rolling road to get it tuned but you've got a more basic problem, you'll end up potentially wasting your money paying for expensive RR time while the operator changes the plugs, or tells you that your engine's down on compression, etc. You might spend time time mapping it before realising that the fuel pressure's down, and you need to do it again after changing the pump or the FPR. It always pays to make sure that everything is tip top before turning up at a rolling road.

3 hours ago, Zetecinside said:

A good RR operator would not sacrifice torque for peak power unless thats what was asked for.

A good RR operator shouldn't need to with a mapped fuel and ignition system. That's a compromise that's made at the stage of specifying the cams and basic tune of the engine. A well mapped system will always get the best out of the engine - best economy when pootling around, best power when "on it".

[Zetecinside]

Slightly disagree.

My lotus twink has emerald and i can switch between maps on the fly.

On same RR at slark the difference between full power and guest map was 30bhp almost.

Thats an over bore and 1600 crank so differences would be smaller on a basic engine.

My point is i can say its got 180bhp, when really i can run the low setting and its just over 150bhp

The difference is a change in fuel mapping and ignition mapping. Its essentialy a dry and wet setting.

[Kevin Wood]

Yes, of course you can have a milder map you can switch in if you want to, but there's no reason to.

[Kingster]

8 hours ago, Kevin Wood said:

Yes, of course you can have a milder map you can switch in if you want to, but there's no reason to.

Well there’s the reason specified above, wet/dry track map and you might want an economical touring map vs an all out sprint map. 

[Zetecinside]

Point is its not as easy to give a number.

But

If thats what you want, then 170bhp is a good ball park figure for a 2.0 @ 6000 rpm and 90% efficiency.

Incidentall, the same engine @ 7000 rpm with a reduced efficiency of 85% give just a couple of bhp less.

169 vs 167

This is worked out by calculating the air consumed and using STP conversion factors.

Lets not forget that different RRs use more "favourable" conversion factors to plot their graphs, so what we say and they say may be different.