It's Coming Together

[Longboarder]

Back from the rolling road and partial success and partial failure.

Swung the cams and 24 advance on the inlet(crank 48) and 6 retard on the exhaust (crank 12) gives a broader power band without much loss low down. Flat torque curve from 2000 to 7000. However there is only a slow rising BHP. Doesn't get to 100 till 4300 and climbs slowly to 150 max at 7000. Car drives fine. Much better than with the VVT controlled by a simple switch. So better to drive, accelerates better but no significant gain in BHP.

So do I junk the engine and fit a blacktop, fit a blacktop head or start saving for some of cat cams finest ST cams and followers?

I did come across a post somewhere by an ST owner where he fitted some uprated blacktop cams with a modified front pulley centre. I've lost the post and he didn't say what followers he used.

Two steps forward but one back. I wish I had stayed with the blacktop.

 

Nigel

[Longboarder]

The success. Timing the inlet to 24 degrees advance and the exhaust cam 6 degrees retard from the 0 datum worked best. The torque curve went pretty flat. No power crash after 5500.

The failure is the cams themselves. I suspect they were already flowing about as much air as they could so no significant increase in the BHP figure from re-timing them which is much as expected. However the figure once again is across a broader band although a little higher up the rev range. At least it is still pulling when you change gear rather than having to change because the power has dropped right off. What does this mean? A better drive, you have to keep the revs up for action but still fine round town. Lost that sudden switch of power coming in at 3000 and just as suddenly going off at 5500-6000. A big advance on the VVT controlled by a simple switch.

 

Car behaved well on the rollers. New engine runs sweet as a nut and nothing broke which is nice since I built it. No overheating. Breather passed about 50ml of oil into the new lightweight catch tank. No oil or water on the floor. Used about 3 gallons petrol. Standing beside the car when it is doing about 120mph on a rolling road is an experience.

 

Dinger, you are right that the standard cams are maxed out and can give no more. Interestingly what is shown is that a fixed advance of 24 degrees gives a much better power spread than switching 0deg/30deg as most end up doing if they don't have pwm control in their ecu.

My conclusion is still that the ST is an expensive engine to tune but an inlet vernier is a good step if you can't stretch to new cams and followers.

 

What now? Do I start saving for some cat cams and followers or go back to blacktop? Whatever, it will have to do as it is for another year. I don't know if I can afford more power. I only get 2000 road miles out of the rear triple eights and if that comes down any more I will never be able to afford new cams

 

Nigel

Figures are at the wheels. The two curves are different cam timings.

[Guest dinger]

Nigel,

 

Stick with the St170 mate,

 

Its an extremely strong engine and will give you confidence when on track,

 

Its a known fact that the only restrictive part of this engine is the cams, As the only way to increase power is to increase volume and the standard cams have not got enough lift or duration as it still needed to be driveable for the normal user, Save for a set of cams and an appropriate ECU and I dont think you will have any regrets looking back,

Speak to Matt at "Tour de Force" in Kimbolton as he is the god of VVT, Below is my origonal Rolling road printout which was done to pass IVA so not a balls out map, The most noteable difference between your on eand this one is huge difference in Torque at low revs,

My setup gave very good low down torque, this is acheived by constantly changing the cam timing from the inputs from speed sensor and cam position sensor, letting the ECU to fully control the cam, Hence the term "varible valve timing" Matt found that even at idel the engine needs a small amount of change in the timing to give good hydrocarbons, As the torque drops off around 4500 revs BHP takes over as there is no need for torque, after all you are now in the perfect power band,

 

You will still spend the same amount of money getting the Zetec to 230 bhp as you would complete the ST170 engine,

I would personally aim to raising the torque low down the rev range, that will make a very different and rewarding car to drive.

I do feel that the wind was blowing towards you while urinating and you have had your traousers covered in wee wee, but if anything, it has given you some good experience and great deal of knowledge gained from those tests,

 

I stand by my statement in an earlier post that the only way to make good power is to spend good money getting there!

Please dont give up on that engine, While the Zetec's and duratecs have broken down with broken conrods and melted pistons you will be waving to them as you drive past.

 

Dave

[Longboarder]

Very interesting. Your map is an old one. Can you tell me what mods you have made since then in the form of hardware? Have you fitted cams and followers (or lashcaps)? Have you done anything to head or exhaust? What have been the overall effects for you?

Comparing the maps is difficult. Two different rolling roads and mine is wheels and yours corrected flywheel and I don't know what corrections have been applied. So only useful to compare profiles of the curves. If I apply a 20% mark up to all my figures (Est flywheel) they look a little less shabby but even more pretend. I have got a big hole up to about 5000rpm where cam advance is too great which was expected but then mine hangs on a bit better to 7000 and doesn't drop away so fast. That's simple for you to fill as moving your cam closer to 24 deg advance from 6000 is just a few minutes with the cam map and looks like it might pay dividends. I'm stuck with what I've got and not much chance to make any changes. I would like more power but it aint gonna happen for a while. The rest of this years budget is going to go on suspension set-up and tyres.

 

Nigel

[Guest dinger]

I left the engine and the map alone as I was happy with the power and the way it delivered it, I merely put the map up to show the differences in where the torque and BHP were delivered,

 

I think your right to spend the money in the chassis area Nigel as you are going to see a larger improvement in lap times if thats what you are heading for, Alot of people seem to get lost in chasing BHP when alot of time can be made up in chassis development and driver tuition.

 

Power is nothing without grip! I'm sure that was a tag line for a major tyre manufacture, LOl,

[Longboarder]

Rats. I thought you may have a fire breathing monster and I could pick your brains.

Out of interest do you have an exhaust vernier? The gains are significant. What cam timing does your map show for full throttle at 6000rpm and above?

 

Nigel

[Guest gdc]

el 0st 170 is brill engine nigel if you need mess about with it . then you will get

srtange readfings, i if you faf about with it .. leave it alone .

[Longboarder]

Hi Graham, I have run with it standard for over a year and don't like the power delivery. Current set-up is only a little more power but a much wider spread. Ideal would be to properly control cam advance for an even better spread of power.

 

Nigel