Cam reprofile for beginner and children

[renmure]

Not Lotus related but hopefully someone can offer some simple (perhaps simplified) advice.

I'm thinking about having the cams on my Alfa engine reprofiled to get a bit more power and a bit more throbbing, lumpy race car like noises... yup, I'm really that shallow. but without feeling like I'm driving a soon-to-explode hand grenade.

On the Piper Cam website there's a bit where you can enter your current engine and they offer an option/options for what you can end up with. This comes up with the single option for the Alfa V6 24 valve engine as ARV6BP270H which has the "spec" below so it all seemed simple.



Searching on the Stratos forum a couple of others had done something similar but gone for this #1326 HYD option which confused the issue for me.



Doing some more digging I found this comparison table.



I know I have the GTA cams in my engine which shows a potential 6 BHP over the standard cams. It shows the Piper ARV6BP270H as having a potential 16 over the standard. It also shows the Piper "Fast road" option as having a potential 25 BHP over the standard ones. It doesn't show the #1326 option. Cost wise, there's nothing in it really. I know that car will have to be remapped after any cam change to get the full benefit and that's no problem.

I've spoken to the sales guy at Piper and effectively been told that they are all popular and it really comes down to what the individual wants. That's great, but doesn't really help me.... probably because I'm not actually sure what it all means

I'll no doubt be guided by the LB factory, they've already said it's quite a good idea for my car, but is there anyone who can simplify the above or offer pointers or .... ?

[graeme]

I can't help technically, but if I could have one car back it would be the Sport160, just for that lumpy idle. Do it!

[robin]

Both have the same duration so will have similar shaped power curves (in terms of at what RPM peak torque is developed).

The 1320 has 9.9 mm lift Vs 9.65 for the 270 so in theory can generate a bit more gasflow and thus more power.

The lumpiness will all come from lift on overlap. Assuming you don't have adjustable sprockets (so called Verniers) then this will be quite random between cars and possibly even cams of the same grind.

Go for the 1320 ... Provided piper say they are compatible with your lifters and springs.

[renmure]

I can't help technically, but if I could have one car back it would be the Sport160, just for that lumpy idle. Do it!

That's my type of answer
This all just came into my head when I thought back to my old S1 Exige 190 lumping away at idle

[renmure]

Both have the same duration so will have similar shaped power curves (in terms of at what RPM peak torque is developed).

The 1320 has 9.9 mm lift Vs 9.65 for the 270 so in theory can generate a bit more gasflow and thus more power.

The lumpiness will all come from lift on overlap. Assuming you don't have adjustable sprockets (so called Verniers) then this will be quite random between cars and possibly even cams of the same grind.

Go for the 1320 ... Provided piper say they are compatible with your lifters and springs.

Thanks. I hoped you would shout up

I'm delighted to be told what to do so just want to check, do you mean 1326 above rather than 1320?, as in the link in the photo? If so then great because that seems to be what the other 2 guys went for.

Muppety question time but... is there a down side to this? It seems like a cheap(ish) way to get more power, some cam profile options in the table above show more than 10/15% more (whether I really need that is a different matter) so why isn't everyone else doing it? Is there a point where it blows up the engine or something like that?

If my GTA engine has a different cam from the standard engine to give a potential 6 bhp more out of the box then why didn't Alfa make it something "better" to give even more?

[Shug]

Cams *tend to* just move the torque curve about. So you'll get a bit less shove lower down, traded off with more power as the revs increase.

Standard engines also have to do things like comply with emissions regs etc, not something that's generally helped by throwing more fuel and air through them.

An engine which produces more power with revs will tend to stress things a bit more due to it tending to run higher up the rev range for longer - but it's not likely a set of cams will start stressing the internals to a point that things start getting fragile, unless you go full on race cam and up the rev limit to where the power would be on that cam profile.

[renmure]

Cams *tend to* just move the torque curve about. So you'll get a bit less shove lower down, traded off with more power as the revs increase.

Standard engines also have to do things like comply with emissions regs etc, not something that's generally helped by throwing more fuel and air through them.

An engine which produces more power with revs will tend to stress things a bit more due to it tending to run higher up the rev range for longer - but it's not likely a set of cams will start stressing the internals to a point that things start getting fragile, unless you go full on race cam and up the rev limit to where the power would be on that cam profile.

Thanks also.

That makes sense. I didn't think of the effect on emissions and probably mpg aspects as well of just burning more stuff and can see why that's perhaps not for everyone all the time.

No plans to move the rev limiter and what you've said helps explain why I'd read that if you went too wild with the cams the car could become a bit of a pest at low revs or in traffic but I hadn't appreciated why.

[Evoman]

Have you spoken to any of the Alfa experts like Dan at Autolusso in the Lakes branch? Super knowledgeable chap about the GTA engine and tuning options.

[renmure]

No. The truth is that I'll end up just going with whatever advice the guy who built my engine (he's an Alfa and Ferrari engine specialist) and the folk at the LB factory say. I was just trying to get some background info about things. I hadn't realised there was so many variables. If I have any input it will be for the #1326 thing above.

[Evoman]

Yours is the 'Bussone' 3.2 litre engine though no? Does that chart not show comparisons of the different cam profiles for the 3 litre Busso?

This book could be of interest: https://books.google.co.uk/books?id=m61 ... &q&f=false (Chapter 15 Camshafts - a group buy was organised a while back for the Jim K performance camshafts and with remap on a GTA engine 290bhp was the figure being aimed for)

[renmure]

I'm sure all the info in the book will fly over my head..... but I've found a copy on eBay and ordered it, thanks

I understand the camshafts from the 3.0 and 3.2 engines are the same, just the profiles that are different. Anyhow, LB have a set of nice, freshly reconditioned camshafts all boxed up for me. They are going to speak directly to Piper and give the full spec of the engine along with all the info from the recent rolling road session and see what their recommendation is. It will be interesting to see what they come back with.



The working plan, assuming Piper come back with something suitably lumpy and giving more power, is to keep the current GTA cams in the car till it goes through the IVA test then swap for the Piper ones and head back to SCS Delta for another rolling road tuning session.

Vroom vroom

[Evoman]

This is the thread where the author of that book is involved in the discussions regarding regrinding camshafts for the GTA engine

https://www.alfaowner.com/Forum/alfa-gt ... p-buy.html

I think a 10mm inlet cam was initially trialled then followed by a 10.3mm inlet. Some interesting hardness tests from his work shows the GTA cam to be nearly double that compared to some well known tuner cams.

[robin]

Yes #1326, sorry.

Assuming you keep the old cams,I don't think you have much to lose except the ££ it cost.

You might not like the loss of low end torque, but given 3.2L V6 I imagine it will still have plenty of torque to not stall on you or require mad revs to pull away

I don't think the factory cam sprockets will be adjustable, so don't forget you will need four of those (assuming there are four cams). Then whoever installs the cams needs to set the cam phase to hit the LATDC number. Easy on inline 4, harder on V6. Otherwise if you go with stock sprockets you might find the LATDC is more or less than it should be.

No doubt your alpha engine specialist has more direct experience. My knowledge mostly from the Krappy-K.

Cheers,
Robin

[renmure]

Hi,
Can I bump this and ask for some further online education

Bare with me here....

We are having a slight change in relation to my Stratos now that the IVA has been overcome.

The intention was to change the 3.2 GT cams for reprofiled Piper Cams and the profile that Piper suggested was this one:



The new direction is to change to an AH Motorsport Fast Road cam profile who have come back to me and said...

Our Profile is 290 degs 10.11 lift 35/75 75/35

So, going back to the table below I'm taking a guess that it's the AHM / Kent Fast road one listed here??:



Can anyone .. Robin, I'm looking at you here give a simple enough explanation for a numptie of the difference between the Piper and AHM profiles and what that means/does? eg I'm seeing 290 degrees with the AHM one and 48 degrees with the other

I know that ListerBell are fitting vernier pulleys as well as part of the change and the car is heading over to the same rolling road / mapping experts who did the ECU etc so I'm really just trying to get a bit more knowledge for myself.

[woody]

They 290 is the cam duration; there will be lift for 290 of each 360 degree rotation of each cam lobe. In the case of the one AHM/Kent far road cam, the inlet is 290 and the exhaust 262 degrees respectively.

The other cam has a duration of 264 degrees for both exhaust and inlet with an overlap between the inlet and exhaust of 48 degrees. So the over lap relates to the position of the inlet and outlet can lobes relative to each other.

Of course, with verniers on separate inlet and exhaust cams, the overlap is variable (I say this as I'm in the middle of reading mini engine stuff, they have only one cam so the relationship of the lobes to each other is always fixed, even with a Vernier).

The overlap for the AHM /Kent can isn't listed, not is the info to calculate it. It's undoubtedly a more extreme cam though with much more inlet timing and a bit more valve lift.

The AHM can will be the lumpier of the 2. If you want really lumpy, get them to use the standard fixed pulleys like Lotus did with the 160 (don't!).