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VCT on the 1.7 Puma engine - The real facts!
Jenko - 7/6/14 at 02:46 PM

There has been so many discussions on this. On Friday I took the J15 to Northampton motorsports to map a standard engine on TB's with the VCT working as an on / off function. The reality of the system, is if mapped in correctly, it works remarkably well. The results are in my latest blog post. But 155bhp on a standard engine with a decent power and torque curve is admitedly more than I expected.

Check out the blog for the full story.

ceebmoj - 7/6/14 at 03:11 PM

great blog, interesting read.

Ugg10 - 7/6/14 at 07:41 PM

Excellent news, great car and confirmation that my engine should do what I want. Are those figures at the flywheel or at the wheel?

For info what size are your tbs (jenvey?) an also what diametre exhaust and length of headers. My exhaust will have shorter headers and 42mm tbs so interested to see the differences. Also glad the vtec way of controlling the vct works well which opens up my ecu choice a bit.

Thanks for sharing.

[Edited on 7/6/14 by Ugg10]

Jenko - 7/6/14 at 08:17 PM

Figures are at the flywheel....I think it was somewhere around 130bhp at the wheels........

The tbs are good old gsxr750's, k1's I think....not sure on diameter, but 42mm rings a bell, tapering down to 40mm. Exhaust, 2 1/4 inch.....

Just make sure the ecu has a feature to turn the VCT signal off at higher revs.

Ugg10 - 7/6/14 at 08:35 PM

Thanks, sounds similar to my set up. I'm starting to get hopful of what mine may do, anything around 150 would be great. Looking at emerald at the moment but omex 600 is a possibility. My tbs are 42 inlet and oval 43x34 exit which closely matches the head ports.

Ugg10 - 8/6/14 at 09:23 AM

Had another read of your blog, and a look at the power graph, you say that you turn the vct off at 5850rpm, would you care to share when you turn it on at the lower end as it looks like it is before the graph starts. Looking at other comments on the Web they are all around 5500 to 6000rpm to turn off (consistent with yours) but not found out what the turn on point is, info ranges from 1500 to 2500 rpm.

Also for info what injectors were you using, the puma ones in the head or ones in the TBs?

Sorry for all the questions but best to ask twice and do once.

Jenko - 8/6/14 at 10:35 AM

It turns on at around 2000 rpm...can't remember exactly, but alas graph does not show it....

Injectors are standard puma ones in the head not the Tb's

Ugg10 - 8/6/14 at 02:31 PM

Many thanks again for the info, very useful for my build as it seems we will have very similar engine setups, I am planning to use the puma injectors as well. I think 150hp in a ford anglia should be plenty (to start with).

I'm going to be really cheeky and ask whether I can have a copy of your omex map as a starting point, I should be able to translate it to whatever ecu I go with. If that is ok then pm me and I will send you an email address.

The more I look at the j15/vectis the more it looks like a baby lola t70, your colours scheme really suits it.

beaver34 - 8/6/14 at 03:54 PM

nice results

are you running standard cams currently?

Ugg10 - 8/6/14 at 04:24 PM

From the post and his blog looks like engine internals are all standard, be interesting to see what it would do with a set of SS4's (there is a mention of future upgrades, looking froward to seeing this evolve) ?

beaver34 - 8/6/14 at 06:39 PM

Very surprised to see that power on stock cams

Jenko - 8/6/14 at 07:08 PM

[Edited on 8/6/14 by Jenko]

Jenko - 8/6/14 at 07:09 PM

Standard engine apart from Tb's and of course the exhaust system and omex 600... Can't wait to get it through iva and chuck in a set of frp cams.

beaver34 - 8/6/14 at 07:30 PM

Ss4 shawspeed cams are better than the frp and work well with itbs

Some stronger valve springs and rod bolts will see it rev to 8k to make the most of the cams

Jenko - 9/6/14 at 11:55 AM

Must admit, I was unsure about what to rev it to. We figured 7.2k would be safe, but it was still making power at the point. I think the puma engine uses some strange powdered metal construction for the con rods....Can't work out if thats a good thing or not, but there does not seem to be too many horror stories out there......

beaver34 - 9/6/14 at 12:49 PM

quote:
Originally posted by Jenko
Must admit, I was unsure about what to rev it to. We figured 7.2k would be safe, but it was still making power at the point. I think the puma engine uses some strange powdered metal construction for the con rods....Can't work out if thats a good thing or not, but there does not seem to be too many horror stories out there......


they are powered cast and broken to separate.

with hd rod bolts you can rev to 8k, you will need uprated valve springs to do 8k really though, piper make them, shawspeed make the rod bolts

anything above 8k you will have cambelt tensioner issues when lifting off the gas at high rpm

you could go a for a ss3 cam and have the pistons pocketed to run these, would do over 170 then no worries

johnH20 - 9/6/14 at 04:04 PM

Hi Jenko, very interested in your approach. Do you have two complete fuel/spark maps that you switch between? It is difficult to imagine that one map would be optimum for both cam positions.

Jenko - 9/6/14 at 05:27 PM

As I understand it, it was fairly straight forward to figure out a base setting for both the on off position. I know he spent some time getting this right. To be honest, Troy from nms is so familiar with the omex software he could really rocket the settings.

I'm exactly sure where it does turn the VCT on as the rpm on the plot does not go down that far, but I will try and find out.

Paul.

nickm - 9/6/14 at 07:27 PM

Hi Jenko

Your making me wish id kept my old Puma and not bought a brand new 1.6 !!

Good figures but the pull with the VVC will make it feel even more

Nick M

Jenko - 12/6/14 at 08:33 AM

If interested, I've added some more plots to the blog, that shows the comparisson between the full on, full off, and on/off of the vct system.

Ugg10 - 12/6/14 at 11:01 AM

quote:
Originally posted by johnH20
Hi Jenko, very interested in your approach. Do you have two complete fuel/spark maps that you switch between? It is difficult to imagine that one map would be optimum for both cam positions.


Sorry to butt in but my understanding of the process is -

Keep the VCT in the Off position - map the engine as normal maximising power/torque/efficiency etc. - save the map (map being tables of load vs rpm for injection duration and ignition advance)
Switch the VCT to the On position - map the engine as normal maximising power/torque/efficiency etc. - save the map

Print out the two power/torque runs for the on/off positions, one will give better performance at low and high rpm (off position), one will be better at mid (on position), find the cross over points - approx 2k and 6k for the Puma 1.7.

The in a new map copy the low and high (below and above the identified cross over points) rpm bits out of the Off position map and the middle (between the identified cross over points) rpm bit out of the On position map. You now have a composite map that cover all loads and rpm sites but takes the best bits of the two positions of the VCT. The last thing to do is to set the rmp switch aux output to come on and go off at the chosen rpm to conrol the VCT (you also need to plug in the cold start, cranking parametres etc. as usual).

So, one map but made up of two separate mapping sessions at on and off VCT positions and then controlled by the rpm triggered Aux out.

Hope that helps.

Ugg10 - 12/6/14 at 11:05 AM

quote:
Originally posted by Jenko
If interested, I've added some more plots to the blog, that shows the comparisson between the full on, full off, and on/off of the vct system.


Many thanks for posting the on/off/total plot, very useful and graphically shows the benefit of the VCT and also the point at which to switch. I am starting to get a little excited at the thought of getting my engine up and running later in the year (to many mechanical jobs to sort out first !).

[Edited on 12/6/14 by Ugg10]

Jenko - 12/6/14 at 11:28 AM

quote:
Originally posted by Ugg10
quote:
Originally posted by johnH20
Hi Jenko, very interested in your approach. Do you have two complete fuel/spark maps that you switch between? It is difficult to imagine that one map would be optimum for both cam positions.


Sorry to butt in but my understanding of the process is -

Keep the VCT in the Off position - map the engine as normal maximising power/torque/efficiency etc. - save the map (map being tables of load vs rpm for injection duration and ignition advance)
Switch the VCT to the On position - map the engine as normal maximising power/torque/efficiency etc. - save the map

Print out the two power/torque runs for the on/off positions, one will give better performance at low and high rpm (off position), one will be better at mid (on position), find the cross over points - approx 2k and 6k for the Puma 1.7.

The in a new map copy the low and high (below and above the identified cross over points) rpm bits out of the Off position map and the middle (between the identified cross over points) rpm bit out of the On position map. You now have a composite map that cover all loads and rpm sites but takes the best bits of the two positions of the VCT. The last thing to do is to set the rmp switch aux output to come on and go off at the chosen rpm to conrol the VCT (you also need to plug in the cold start, cranking parametres etc. as usual).

So, one map but made up of two separate mapping sessions at on and off VCT positions and then controlled by the rpm triggered Aux out.

Hope that helps.


First off, it wasn't my approach, it was the knowledgable chaps at NMS...whereas I do understand how the system works, the real clever bit is in the mapping.

But what Ugg10 has said here is correct. One map is used after the two points of on/off are found. The only thing to add was there wasn't really two mapping sessions, just from a quick optimisation it was clear where to turn on and off from there on in it was just like mapping a normal car. The only other thing to build in was the throttle load. Under light throttle load (i.e. <30%) there was efficiency savings to be had, so they figured out that there was no need for the vct to be on at gentle motorway cruising speeds. This is nice because you can hear a notable change in the induction noise between on and off, so it's fairly quiet when you want it to be.

P.

Paul AS - 12/6/14 at 12:21 PM 

code:
Your making me wish id kept my old Puma and not bought a brand new 1.6 !!


Dear oh dear Nick - you need to get your car finished mate!! 1.4, 1.6, 1.7 , VVC ? You're gonna wish you had em all!!

Any danger of IVA yet??

johnH20 - 12/6/14 at 02:26 PM

Thanks for the above. I would only add that ,in theory at least, you could be anywhere in the speed range at less than 30% ( or what ever your chosen value ) of throttle opening hence you would need a full VCT 'off' map to cover this. Only likely to be a transient condition outside of cruise though.

Jenko - 12/6/14 at 02:52 PM

quote:
Originally posted by johnH20
Thanks for the above. I would only add that ,in theory at least, you could be anywhere in the speed range at less than 30% ( or what ever your chosen value ) of throttle opening hence you would need a full VCT 'off' map to cover this. Only likely to be a transient condition outside of cruise though.


If you take speed out of the equation as the ecu has no idea of car speed or gear. The fuel and ignition map are plotted by rpm vs throttle load. So simplistically, any part of the table that is under the 30% throttle load is mapped accordingly to account for the fact that the vct is off. Still just one fuel and ignition map required. If you wanted to change the throttle load point that the vct kicks in then yes, you would need to do some fuel map optimisation. But around 30% seemed about right during the rolling road session.

If you think about it, that only covers a fairly small part of the fuel / ignition map, but means when you are off throttle or driving gently, the advanced cam is not needed. I suspect even the standard ford ecu has some algorithm that backs of the cam advance on light throttle loads, but I would still think that it only uses one map.

Ugg10 - 12/6/14 at 03:21 PM

I've no evidence for this but I suspect the Ford map just rounds off/angles the edges of your table top "on" portion of your map i.e. that bit above 30% TPS value and between 2k and 6k RPM approx. giving a slightly smoother lead in and lead out to those boundaries. This is probably what you would do if you were controlling the VCT via a PWM map which is avalable in the Omex 710 ECU and what the Triggerwheels/motorsportselectronics VCT controller does.

Intersting on the Triggerwheels site it shows a power map for their VCT controller that looks almost identifical to Jenko's map graphs he has added to his blog - http://trigger-wheels.com/store/contents/en-uk/d68.html - which sort of prooved that the simple off/on/off method is pretty good.

Jenko - 12/6/14 at 06:16 PM

Re the vvt pro and the graphs on the trigger wheel website.....this is what frustrates me and I believe is misleading to the customer.

First off....I've had stuff from Trigger wheels before, and found them brill so this is no reflection on them. But, as per the previous thread with the company who developed the VVT pro, I think the claims are a little confusing. No problem with the product, and reality is a full on controller that also looks at the cam sensor and is constantly variable has to be a good thing. I just wish they show a real like for like. You cant compare the with vvt pro without showing what a correctly mapped on / off system loks liket....plus, why do they compare the vvt controler with a permantly on cam..of course this will hold back power at the top end.

I still agree that the variable control is no doubt better than on / off, but we are yet to see by how much....

johnH20 - 12/6/14 at 06:34 PM

Not wishing to set myself up as an expert which I am not I have seen 3D cam maps. An important dimension of OEM stuff is fuel economy and emissions which may or may not concern us performance types at your choice. The cam map has a significant influence here. My interest, as I suspect with most enthusiasts, is best performance within the practical limits of affordable mapping. For an OEM this takes thousands of man hours including validation ( 50k miles durability remember ). I admire what has been done here, just want to understand fully what that is so that someday maybe I can emulate it. Well done Jenko/NMS.

Jenko - 12/6/14 at 08:38 PM

quote:
Originally posted by johnH20
Not wishing to set myself up as an expert which I am not I have seen 3D cam maps. An important dimension of OEM stuff is fuel economy and emissions which may or may not concern us performance types at your choice. The cam map has a significant influence here. My interest, as I suspect with most enthusiasts, is best performance within the practical limits of affordable mapping. For an OEM this takes thousands of man hours including validation ( 50k miles durability remember ). I admire what has been done here, just want to understand fully what that is so that someday maybe I can emulate it. Well done Jenko/NMS.


Spot on....I can't begin to think how complex the OEM mapping is to allow for all the variables (including selling the cars in other countries). And it could well be on a full throttle run, the VCT system basically works like the on/off. Hence why the graph on the trigger wheels site looks not to disimilar to the one I ended up with (although it's on an ST170).