neilm

I've seen on a couple of Yank sites about using an Under Drive Pulley Kit will see power increases of up to 5bhp..

Which seems a pretty wild claim on a Normally Aspirated Motor

Anyone on here got any experience of these things ?

Also any other nice simple tricks that will help push me closer the 200BHP mark.


Engine is a 2.0 Black Top on Dellorto 45's with OMEX Management, Kent Focus 12 Cams with Solid Lifters, Ported Head.


Dont want to Supercharge it or Turbo it.

Ex-Finesse

I purchased a Focus Sport pulley, apparently proven results of 3bhp. In theory you should get higher gains on a modded engine

Info here.

It's 23% underdriven, and is the lightest of all zetec crank pulleys I could find.



As for other mods... what air box / filter system are you using? What were your intake temps whilst it was being mapped @ Northampton?

Carbon airbox may be a few hundred quid, but it'll certainly give more consistent air temps throughout the year. Some friends of mine have really struggled with air temps on ITB'd zetecs and I4s.

Could you fit longer trumpets? Any pics of the engine? My engine builder is going to modify my inlet manifold so the bodies are angled up by 18degrees above the horizontal, which apparently increases air velocity. Just wondering if this had been done on yours.

Do you have space for longer trumpets?

All I can think of at the moment.

Red16

are these underdrive pulleys just a lightened crankshaft pulley? if so it wont make any difference to your power figures, in theory it would improve engine response in the same sort of way as a lightened flywheel but it would be so small an amount you wouldnt be able to measure it.

PF Ben

iTrader: (1)

Hi Neil, don't do it! They really are dog knob, I tested one about four years ago on a Focus and it didn't do a damn thing!

Ben

neilm

I run my carbs open....

I've only got room for 50mm trumpets and have upgraded to the Titan Motorsport Billet ones with the 7 degree taper etc and they are lovely...



Cheers for the heads up Ben... I shall spend on something else.... bigger valves or a compression ratio raise or some thing like that.

Wardy257

You should already be pretty close to 200 bhp on that spec, something is not quite right.

neilm

Well a friend of mine had his MkI Cortina set up earlier this week and that was a brand new black top on Weber Alpha and a pair of 45's and that made 160bhp on the nose

The engine was brand new and has only done around 1500 miles...

But 160-170 is about what you normally see on a standard 2.0 Zetec on carbs and management

So I've found between 15-20bhp with the cams and head porting

I wouldnt expect to find 30-40bhp with just those mods.

Ex-Finesse

No, they're also smaller than standard, hence the term "underdrive".

They'll therefore drive your auxilaries slower - alternator, power steering, water pump, etc.. and this'll lessen the drag on the crank.

Important also for high revving engines where standard engine pulleys could overspeed some components, such as the waterpump, causing cavitation!

Neil - zetecs respond well to changing the trumpets. I hope your new tapered ones yield some improvements

What CR are you running? 10.5:1 is certainly safe. 11:1 is getting a bit high for standard pistons, but I've seen some people claim it.

I think you could be at the stage I was with mine. Going further would mean forged pistons, solid lifters and a new cam. Yours obviously already has the solids, mine was a silvertop

Wardy257

If Dunnell can get 195bhp from cams and headwork, so can you:

http://www.dunnellengines.com/zetec_...tionkits_2.htm

These guys are the best, Dunnell have worked on the ZETEC (or ZETA as it was back then) from day one.

Ex-Finesse

"Option 2" graph shows distinctely under 190bhp though....

They also keep using some standard equipment for longer than I'd personally be happy with.

All my zetecs have maticulous maintenance, yet they all have a nasty half-second tap of dry tappets when first started, it's worse if it's had a good thrashing on the previous journey.

Dunnell seem to stick with std. hydraulic tappets and std. rods even in their high power engines (230bhp). I'm looking for around the same power, and we're going solids and steel rods. I pray for std rods @ 8k rpm

Wardy257

Dunnell know what they are doing, the grapth is just a representation.

I would not even bother using carbs these days though unless they are for race regs. I would also sacrifice 10 bhp for better response and low down torque too.

neilm

I agree Dunnell is THE place to go if you want a race engine thats built to conform to the regs but be a winner, as their engines win on a regular basis.


Anyway.. forgot to mention, mine was rollered at 178.4bhp, 148lbft Torque and 141bhp at the wheels.

This was at Northampton Motorsport and those who know, will know they never quote you happy.... they've broken my heart a few times.

Oh and I forgot to say we fitted a pair of vernier pulleys but swinging the cams didnt really make any difference


Dont seem to have any issues with low down torque or throttle response my only real issue is the fueling is bang on on full chat but rich mid range so it needs more work setting the Dellortos up and I just want more power....

Wardy257

Fuel inject it, it is the only way to go. You will waste a lot of RR time get carbs set up and even then it will not be right. Twin 45s fetch good money so sell them and get some 40mm TBs.

I saw a test with these pulley a while ago and they lost power!!!

Red16

ah right, cheers for pointing that out