CAMSHAFT CHOICE
Turbo Mini Forums

someone who has a dyno, for instance Dave?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Msg to Ian Avonbar

Ian if possible could you elaborate a bit on the difference between the AR13T, Phase 1 and Phase 2 turbo cams? As I mentioned previously I have an AR13T I plan to use, but if there are obvious improvements over it in the ph 1-2 cams then I may be persuaded to use a different one? It is to be used with one of your st 4 turbo heads and 1293cc, low compression (15cc pistons)
Thanks.

That's correct. Someone with a dyno.


Tom, I recall my phase 1 cam drove very nicely from low RPM, admitedly with a 8.8:1 CR and stock dizzy... When i went to the ph2, i did notice the loss in off boost performance.
I them went over to Weber Alpha injection, and this improved matters, to the point i was happy with it.

This years engine saw another 'freshen up' and the fitting of 1.5 rockers. I'm not happy with how it is at the moment, remember i have the benefit of fully mapped ignition, but am also very fussy about good road manners!!! LOL!

Edited by turbodave16v on 29th Sep, 2004.

good point there dave...

is it a cam problem causing lag or is it a lacking ignition system?!?!!!!


alex

AlexF

can't beat the 266/286 hybrid on 108 lobe centres?
actually it worked for me but i depends on inlet to exhaust flow ratios , boost, how efficient the burn is ,exhaust system ,inlet,rockers ,ignition timing, ambient temp , intercooler size and flow , turbo a/r ratios , etc etc etc good luck dave !!!!!!!

Most people prefer overall drivability the 1.5 rockers only accentuate lag due to the engine 'feeling' the valve lift prior to the build up of gass speed i actually dislike 1.5's on ALL A series engines non of my current atmo race engines are using 1.5's
Going back to cams, we all know that in most instances life with a hot turbo motor is a compromise but they have to be user friendly.
We have tried the bigger exhaust valves with the smaller inlets, bigger inlets with offset 32 exhausts and christ knows what else all i can say is the best power we have is 35mm inlets 29 mm exhaust T2.5 19psi phase 2 cam lota of work in the exhaust manifild 2.1/4 s/stn steel down pipe etc etc etc using Micro Dynamics programmable ignition system. we now sell this system over the counter.
Cams again Tom phase 1 inlet 16-56 268 degree duration exhaust 59-30 270 degree duration time cam in "109
Phase 2 24-60 duration 264 exhaust 67-33 duration 280
just out of interest the 266/286 never worked properly but figures are 24-56 duration 263 inlet and 71-39 duration 280 exhaust

http://www.avonbar.com

ahh , the reason why your 266/ 86 cam didn't work was probably your timing figures , i think you will find that it is :
in, 260 dur 380 thou with 1.5 r tim fig 26 / 54
ex 290 dur 468 thou with 1.5r 73 / 37
for 110 lobe centers
it is a cam more for race than drivabillity on the road , but i have used them in milder engines with good results
also i spoke to another couple of ex employees about the ar13t ,and we agreed it was the mg metro cam ground by roland alsop
also what do you mean be the engine feeling the rockers - they obviously influence something off boost and surely it is air speed ?
morals from this banter are basically ,no one has tried every combination of cam boost ,head valves, and therefore it is almost impossible to say it was down to a particular part over another

Stuart you really have all your facts wrong as usual as far as my products.
Jst fo rthe record Roland Alsop has NEVER produced a camshaft for me. You lot might have used him in the past for all your 'homer Engines'Kent Cams produced the original AR13T for me.

http://www.avonbar.com

Yes my AR13T new and unused came in a Kent Cams box!

It may be new and unused but probably 10+yrs old!!

Ian is it correct that the AR13T was ground from a blank? It looks to me like it was as the base circle radius is fairly large compared to reground cams I have seen?

Tom, the original ones were all ground on blanks the later ones were all profiled but on MG cams as they were the closest to the spec that i wanted This was to maintain the base circles With blank cams is the lift is kinder to the valve train and also helps build up gas volocity rather than the severity of some reprofiled jobs.Piper now do ALL my camshafts. fromA & K sreies to Vauxhall
My 216 hp T2.5 motor also runs on a blank.but x drilled.

http://www.avonbar.com

WELL GUYS, WE HAVE CERTAINLY GOT A GOOD FORUM GOING HERE
HOPEFULLY WE MAY GET AN EXCELLENT CAM DEVELOPED FROM THIS FORUM.
Lets not get too heated though.
THANKS ALL
BENROSS

Edited by BENROSS on 1st Oct, 2004.

touchy ,
which of your products do i have the wrong facts for ? i mearly listed the 266/286 cam figures i use
can you swear you have never used a cam ground by roland for any engine built by avaonbar?
and as for a reprofiled cam giving different port velocity to the same profile on a blank thats just .......

anyway this is deviating away from ben getting a cam , my best advice would be to decide on some basic engine parts , realistic power what head ,comp ratio, then speak to the experts , ring kent and piper cams see what they recomend and make a decision based what has been posted on here and their answers

THANKS stuart at vmax for the advice, and to ian at avonbar,
thanks to EVERONE, for the input.
iam no stranger to the A series Engine at all, i have been building these units and racing them for over 30 years but not with the turbo application, we all want to get the best motor possible so i have been sourcing info of you all.

cam profile selection is regarded as a BLACK ART
kept very secret as its only the last trick the guy has left under his sleve to take the WINNING FLAG, well it used to be in the seventies! what we need is to push some new ground on these cams for our TURBO applications
and to show all those hot hatch cossie boy racers its not just a matter of turning up the boost and fitting big wheels & fitting ICE.
THANKS ALL keep it coming

Edited by BENROSS on 1st Oct, 2004.

Edited by BENROSS on 2nd Oct, 2004.

nice to see that some advertised a seri turbo experts are puting some knowledge on this board :), hope they 'll not make too much advertising on their own products,and will let the happyness of this board intact...( better than dealing with mine 266/286 is best than your phase 2 etc etc, or my very big valve head is best than your 36/29 , could you help us to see how they are working without black magic and with detailed RRs power curves vs boost and specs, this would be best that words, are you engineers or dreaming words salers? )
about cams, I have used the std a seri one, the mg metro na cam, the kent 274i cam, and now the avonbar phase 2 cam ;
all these engines have grown in specs regulary (meaning that the std cam was with a std engine with slightly improve in boost and intercooling), the mg ( same as kent 500) was used in the same eng with less cr and more boost , the 274 cam was with 9.2 cr and 10 psi, the phase 2 is in a little monster ( 7.8 cr ; stuart monster turbo head, phase 2 cam, good intercooler,+40 pistons)
the last engine is in his firsts miles , the impression is that it is very drivable , it's surprising how it is idling nicely, then supporting light to part throttle in the traffic and have good transition to boost, can't say more as the braking isn't finished..... this is not my engine but a friends one, mine isn't finshed yet , but specs are the same without that low cr: 8.5 and more std head, basicaly an na st3 with slighlty more space in the chamber , and turbo exhaust valves....

this to say that the phase 2 is a lot more civilized than what i though..
my first turbo with the std cam was healthy it was lacking a lot pass 4500/5000 revs, the second with the mg cam was strong and nice to use, the 274 cam beated the two first in the corner as it was better than the std cam in the lower revs and pulled hardier and longer than the mg cam ( certainly the longer exhaust was important to let all these exhaust gas escaping ; the phase 2 is simply as drivable as the 274 but the 274 was gentle and you feel that the phase 2 have something from an hungry lyon......;I'll let you know how it is when the throttle and the revs will be used freely.
cheers
fab

Edited by fab on 3rd Oct, 2004.

well guys do we have any power graphs?
etc. RRs print outs you could post.
these would be worth a thousand words

BENROSS

Fab, are you using 1.25 or 1.5 rockers???

Hi TD
I'm now using 1.25 rockers , the only cam which has been used with 1.5 have been the std mety cams,
I don't use them anymore since the 274 one, they give about nothing at the top , and are so troubling in the lower revs, definetly, 1.5 are needless in well prep turbo, or perhaps only on the exhaust side to help a little on a shorty cam, but that's only consideration.
benross, sorry about RR prints, you are so lucky to have so many RR, french haven't these sort of tuning help as we can't tune our car by the law, so RRs are very rare.
I have just my feeling and trys to help.

if you need a bag of power , the phase 2 cam is really a very good cam (a known very good torkey cam inlet which make it drivable , with suffisant lift on the cam to not restrict the inlet charge, it can be used with high boost as his exhaust can flow a lot with near 290°, it open early so let some expending gas going to the turbo, so help them to escape and spool the turbine, this make the turbo very responsive and reduce the piston pumping; the next effect is that it reduce exhaust back pressure letting the blown inlet charge to vent the exhaust gas out of the cylinder. this cam can extract with 16 psis around 160 hp from a well prep a seri,
the 274 cam is also a very good choice (harry extract about 140 strong hps from his a seri),
the mg cam (kc 500) can also be a good cam, but I think that it could be beneficial to use larger exhaust valves, ans so cost £££ (larger exhaust valves are also heavier, have a larger stem than the mety turbo stem reducing the flow in the port, and are also closer to the chamber wall, wich also reduce the flow..., or perhaps a 500 cam with 1.5 lifts only on the exhaust side...

fab

Hi Fab,

good to see you again on this board.
Do you think it is a good idea to remove my 1,5 rockers which I am using at the moment with my 274i cam. Have you tried it in direct comparison with both kind of rockers??
Good friends of mine bought an inertia rolling road about 4 weeks ago, which should be usable in a few weeks. I would like to try such stuff then and see the different power graphs!
Harry

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

i have a set of offset bushes in copper s rockers on steel posts, does any body no the ratio of this set up, only ever used them on n/a engine with 296 cam

FAB.
Thanks so much,your comments & experience are so welcome you and everyone have put me in the dead centre of the ball park.
we all thought 1:5s A ok for turbo applications.

jerrys final thought ?
surely all this sugests that most cams work in wide specification of engines , with just some basic knowledge used in your cam choice can you really go wrong ? one may be better than another but so many other parts influence the overall result (rolling roaded , dynoed or not ) , which can also be affected by your expectations or demands from your engine

just fitted piper phase 2 in mine,pulls as sweet as a nut right across rev range and only £57.00
luvley jubbly,lol

Thought i'd see if anyone has had any experience with this cam I spotted on the Kent Cam website:-

Kent 274sp Sports Torque,
Power Band 1500 - 6500,
Cam Lift 7.23mm Inlet 7.13mm Exhaust,
Valve Lift 8.85mm Inlet 8.71mm Exhaust, Duration 248 / 274 Degrees,
Timing Figures 16/52 71/29,
Valve Timing 108 Degrees

I was unsure of how well scatter cams work in turbo engines, I'd heard that charge robbing becomes worse with turbocharging?

Any thoughts?