Piper camshafts

campbellju

Moderators
Staff member
My engine build is coming to an end. I dropped by the shop last week to talk camshaft timing/setup with the builder.

A couple of queries. He checked the duration of the cams that were bought by the previous owner (many many years ago) which I'd always assumed were the 260/260 kit. He found the actual duration to be more like 263/256. This is a guide as the measurement accuracy is +/- with the closest being 262/258 and the worst being 265/254. The intake was consistently a little higher than the exhaust though which reading up is not normal on turbo cars.

I understand if you do split timing on a turbo car it should be the exhaust side that's slightly higher rather than the intake. I can only think it's to help low/mid range that you might use for a rally car rather than the max HP you look for on a drag car? To be honest it's close enough to what I want on a car to not worry about though I'd appreciate people's views.

More concerning is the cam timing. For my last engine build (only "many years ago") I'd simply followed Piper's guidance for 110/110 (Inlet/Exhaust timing) given on their website:

http://www.pipercams.co.uk/pipercams/www/product_nav.php?type=C&cat=CM&man=16&engine=222

Double checking on the internet I understand the OEM cam timing is 110/120 for our SR20DET.
Tomei recommend a 110/115 setting for all their camshafts on our engine
HKS recommend a 108/114 for all their camshafts

My concern is Piper developed the cams for the Primera SR20, as this is the only other application referenced on their site, and lazily transferred the settings over for the GtiR?

I know that to tune the cams in I ideally need a rolling road but I want a decent starting point. On my last map I had to do some abnormal mapping for idle and cruise that I'd not seen on other cars. A 10deg shift on the exhaust cam is pretty significant if Piper have just done a copy and paste error!!!

What other timing suggestions are given by manufacturers for our cars. As with the Tomei and HKS recommendations, I'd expect most to be in a similar range?

Cheers,
Jim
 

campbellju

Moderators
Staff member
I was chatting with another member last night who helped me setup the cams before. He recalled we had the same conversation about the Piper specs last time as well and chose a different starting point to the one they recommended. We were concerned about valve damage as much as anything else with the Piper specs. Neither of us could remember what we went for in the end. It's probably written down somewhere but I've moved houses a few times in between.

As my car is mainly on the road rather than the track then the standard Nissan cam timing doesn't seem ridiculous to keep the overlap sensible. It would give less compromise for low end performance over high end power.

Anyone any feedback on their own experiences with cam timing on our cars?
 

The Doc

Moderators
Staff member
What amount of lift was the duration measured at, some of the manufacturers use differing ways to measure it.
 

campbellju

Moderators
Staff member
Piper don't give any information on how they measure lift. It's a good point as I can see they might be more optimistic for marketing purposes.

I spoke to the engine builder this morning to better understand what he'd done. He commented on the difference in cam profiles from different manufacturers that make the centreline asymmetric by a few degrees to help snap shut valves.

If that's the case then the piper cams could have an offset profile so the piper timing spec might look strange but is actually the correct starting point.

The engine builder will have a go at re-measuring the timing profile to get a better understanding of what's happening.
 

campbellju

Moderators
Staff member
I've been doing my homework on camshaft timing. I won't embarrass myself by trying to explain it but I am wiser as to how it all interacts and can see that it's difficult to recommend a specific starting point beyond what Piper and Nissan suggest.

In theory the 110/110 should help the top end but my 3071 only has a .64ar and may not benefit from the extra overlap. I'll ask the engine builder to also mark up the 110/120 as well to see if it makes any significant difference to the top end (extra air), turbo pick-up or off boost performance.

The 110 on the intake I'll leave alone to give a margin of error between the valves and the piston.
 

Jon Olds

Well-Known Member
I used to set valve timing based on the peak lift position, but it was time consuming compared to setting it up on lift on overlap. If the lift on overlap figures are available, I would use these. Can't help on the effects of changing LCA on turbo cars though, as I don't know enough
Jon
 

campbellju

Moderators
Staff member
Thanks Jon. Sadly I only have the peak lift position but thankfully I'm just getting the engine builder to to do this so it's costly but less of a PITA. It's helpful that you reference the overlap. Although I'm talking about moving the exhaust timing to a few different positions it's the difference in overlap I'm interested in.

Cheers,
Jim
 

Jon Olds

Well-Known Member
With my 'big (high lift) cam' VW engine setting up experiences, its a nightmare trying to get a clock onto a follower then ensring the clockm gives a reliable repeatable reading on a 12mm+ high lobe peak.
Aiming for 1,2 or 3mm lift off the seat on overlap is so much easier
Jon
 

campbellju

Moderators
Staff member
I spoke to the engine builder this morning who had already done what I was thinking of setting the cam spec to 110/110.

This is Piper's recommendation and should help with high rpm breathing. I can always play with this in the future moving it back to 120 on the exhaust side if I'm suffering with low rpm smoothness
 

Fusion Ed

Active Member
Just FYI, piper don't give figures on hydraulic or some rocker cams. Its annoying on the R as they are solid, but by their own words there are too many variables involved. Don't go too mad with lift however, since the .64 housing is quite restrictive. If you see strange things happening on the AFR graph at high loads, its probably issues with cylinder backfilling. I have seen this happen on a couple of R's with incorrect cam timing.
 

campbellju

Moderators
Staff member
Sorry, I've only just seen this reply. Thanks for your guidance Ed. I'm glad you highlighted my concern about the .64 housing being restrictive. It's a good fun little turbo but it has its limitations. I'll watch out for any AFR funnies at high revs.
 
Top