Kelford Cams Low Vacuum/High MAP at Idle
 

Does anybody have any experience or knowledge of Kelford Cams? I am putting together a turbocharged engine, The pistons have a reduced Compression Ratio of 9.7 (down from stock 10.8). The Kelford Cams part is 211-T with these specs:Camshaft Specifications
Mazda LFVE 211-T
VALVE CLEARANCE:
INTAKE: 0.25MM SET COLD AT THE: CAM
EXHAUST: 0.30MM SET COLD AT THE: CAM
CAM LIFT:
INTAKE: 10.05MM
EXHAUST: 10.10MM
ROCKER RATIO:
INTAKE: 1
EXHAUST:1
NETT VALVE LIFT:
INTAKE: 9.80MM
EXHAUST: 9.80MM
ADVERTISED DURATION AT 0.10MM
INTAKE: 264°
EXHAUST: 264°
DURATION AT 1.00MM VALVE LIFT
INTAKE: 224°
EXHAUST: 224°
TIMING AT 1.00MM VALVE LIFT
IVO:
IVC:
EVO: 48° BBDC
EVC: 4° BTDC
SUGGESTED CENTRELINES:
INTAKE: VARI
EXHAUST: 116°
LIFT AT TDC
INTAKE:
EXHAUST: 0.66MM

I'm seeing 60KPA MAP at idle. There do not appear to be any vacuum leaks (smoke test, pressure test, etc.), timing was rechecked/set with tool and valve clearances checked, Crank TDC alignment to pulley verified. When RPM's are increased, MAP drops considerably.

My question is what sort of Vacuum should I expect or is reasonable at idle for this configuration or is something wrong and I'm missing something? Idle on start is 1100 and drifts down to 800 as warms.

When you say timing was checked/set “with tool”
do you just mean the I & E marks on the pulleys lined up? Or was the cam actually degreed and adjusted to set the exhaust centerline set to 116? It shouldn’t be too far off but there’s tons of factors that can influence cam centerline; cam grind, whether it’s a billet cam blank or a welded/reground oem cam, whether or not the head and block hAve been surfaced and how much was removed etc.

Also, are you running some sort of standalone ECU? What is the commanded intake cam advance at idle?

All that to say, bigger cams with more overlap will generally make less vacuum, does the car drive/function ok? Is there a reason you’re concerned with it beyond the number being different?

In process of tuning right now but kind of blocked moving forward until determining if what we're seeing is kosher. Many, many parts were changed so not moving from a "tuned" engine and just adding cams.

This is an NC, so the Mazda tool(s) used are the bar to lock the cams using the slots in the rear of the cams and the inserting rod that screws inti the side of the engine to ensure the crankshaft is in the right place. I was a bit wary of that so we also checked TDC of cylinder 1 old school via the sparkplug hole. The engine was not degreed beyond that and I could not say what sort of mechanical advance that results in but that it is the Mazda procedure for timing (as well as ensuring the alignment hole in the spoke of the crankshaft pulley is aligned with the bolt hole in the timing cover behind it). Anyone know what sort of mechanical advance that process results in the stock cam giving?

Ohh, I see. I assumed it was an NB. Honestly using the cam and crank lock tools should be a very accurate way to set timing, which is why most OEMs moved to that style and got rid of keyways, so I’d guess the exhaust cam should be pretty close to the spec’d 116* centerline. Honestly I don’t think you’ve got anything to worry about if it runs fine

It doesn't run fine. Using ECUTEK software, at idle...fuel trim is maxing out and pegging at 25%, AFR is low, Ignition timing is retarding to 5-6 degrees, etc...much needs to be sorted out but if there is a core issue with this setup having a 60kpa MAP at idle, that problem needs to be fixed first.

Soujds like it just needs to be tuned. If it’s running on a base map meant for oem cams and a full point and a half more compression, it’s gonna run like shit.

It does not idle like shit but it does operate off idle like shit and yes it will need to be further tuned. The question on the table is if 60kpa MAP at 800 RPM idle is reasonable for this setup...the question is mostly about the Kelford Cams and should I keep looking for a problem?

Increasing the overlap and duration will decrease cylinder pressure at idle. The idle speed will need to be increased compared to stock cams. Obviously you need a fair amount of tuning. I would target a slightly higher idle than what you will eventually settle on. Eg if 1000-1100 is feasible with your setup then start out with a 1200-1400rpm while tuning. Extreme valve events can require very high idle speeds. F1 cars idle at 6-7krpm and as high as 9-10krpm while in use.

Thanks @LeoNA . I had been planning on an idle that settles down to 900 with about 12 degrees advance but I guess a higher RPM of 1000 is viable. Other than adjusting the idle to affect MAP at idle, what do you think of my situation...do you think there is likely a vacuum leak, some connection, a timing error or something I'm missing or does it sound reasonable for my config?

I don’t believe there is anything wrong.

I fitted a set of biggish cams to my car and with lots of overlap/duration I was also getting 60kPa at idle.
Made prev MAP only tuning method useless, as idle and 1/4 throttle driving were both 60kPa with obviously totally differing fuel reqs.
Moving to MAPxTPS fixed the issue as then we could reflect true conditions and tune it accordingly.
I also bumped the idle a little to 1100 as it appeared happier than trying for 750rpm..

if the high kPa figure bothers you , then you could use cam gears to reduce the overlap which would help, but then you are reducing the benefit of the cams, which to me wouldnt make sense..

@rascal it doesn't bother me unless it is indicative of some other problem I've missed but I've now gone over everything 2-4 times depending on what is it. Do you have an NA, NB or NC? What did you use to adjust the tune? What cams did you use?

I have an NB but the concepts are the same, and an adaptronic piggyback to adjust the tune,
Mine were custom cams from a builder here in Oz.

can’t remember the specs (was a few engine builds ago now!) but think they were around 226 deg at 1mm I think. 270 adv duration?
Don’t quote me on those figures, but enough for make a difference…

Putting bigger cams in is almost always going to affect your idle. I wouldn’t be concerned at all.

Have you ever used ECUTEK, Haltech or one of the others?

I have a Haltech now. 1500 with custom pnp harness I made, as Haltech don’t do pnp for nb1..

Do you know what your MAP kpa at idle is? What RPM are you running at warm idle?

as I mentioned above, 60kPa at idle. Bumped idle to 1100 to smooth it out..

@rascal Cool. Thanks!

Anybody else with thoughts?

It's not a vacuum leak. It is because of the increased valve events. Don't worry about the manifold pressure. Increase the idle rpm to improve the cylinder pressure and idle quality. Larger cams have increased operating ranges. Higher on the top end and the bottom. The whole power range is shifted up.